Rabbits

Rabbits are popular pets for both children and adults. They are easily litter trained and require minimal maintenance. This chapter stresses diagnosis and management of problems commonly encountered in pet rabbits. Refer to the supplemental readings for more comprehensive information.

BIOLOGIC CHARACTERISTICS

Rabbits, hares, and pikas are members of the order Lagomorpha. Lagomorphs have six incisors, in contrast to the closely related rodents, which have four incisors. The additional incisors (peg teeth) are small, rounded teeth located directly behind the upper incisors. Currently, there are over 100 breeds of rabbits, which vary in size, ear and body conformation, and coat type, recognized by the House Rabbit Breeders Society.

• •All domestic rabbits are descendants of European wild rabbits, Oryctolagus cuniculus.
• •The two main genera of rabbits are Oryctolagus, the European wild rabbits, and Sylvilagus, the cottontail rabbits. These genera differ in chromosome number and cannot interbreed.
• •Rabbits can range in size weighing from 2.5 lb in the dwarf breeds up to 28 lb in the giant breeds.
• •Giant breeds, which average more than 5 kg in body weight, include the American Checkered Giant, the Flemish Giant, and the Giant Chinchilla rabbits.
• •Medium breeds, which average from 3.5 to 5 kg in body weight, include the Californian, the Silver Marten, and the Rex rabbits.
• •Small breeds, which average less than 3.5 kg in body weight, include the Netherland Dwarf, the Jersey Wooly, and the Polish rabbits.
• •Ears vary in size and shape between the different breeds, and most rabbits have upright ears. However, there are breeds that have ears in a downward carriage, which are known as “lops.”
• •Coats can be divided into normal, Rex, and Satin breeds. Normal fur coats have an undercoat with projecting guard hairs. Rex breeds have short guard hairs that do not project above the undercoat, thus producing a “velvety” fur coat. Satin breeds have a genetic mutation that results in a “shiny” haircoat.
• •Specific information concerning breeds can be obtained from the American Rabbit Breeders Association by mail (PO Box 426; Bloomington, IL 61702) or on their Website (www.arba.net).

Anatomic and Physiologic Characteristics

• •Females of several breeds of rabbits have a large pendulous dewlap under their chin. This area is a frequent site of moist dermatitis, especially in obese rabbits kept in humid, warm environments that may have difficulty grooming themselves.
• •The sense organs of rabbits are well developed. Like other prey species, the eyes are laterally set. This provides a completely circular field of vision with the exception of the small area below the mouth. Thus, long sensory hairs around the snout and the sensitivity of the lips help rabbits discriminate food.
• •Teeth are open rooted and grow continuously. The deciduous teeth are shed right around the time of birth and the permanent teeth complete eruption around 3 to 5 weeks of age. The dental formula is 2/1 incisors, 0/0 canines, 3/2 premolars, and 2-3/3 molars. Rabbits are distinguished from rodents by possessing an extra set of upper incisors, which are also known as “peg teeth.”
• •The gastrointestinal (GI) tract has a simple glandular stomach, a long intestinal tract, and a large cecum.
• •The stomach serves as a reservoir for ingesta and is rarely empty. It holds approximately 15% of the GI contents. The cardia and pylorus are well developed, and, due to the anatomic arrangement of the cardia to the stomach, rabbits are unable to vomit.
• •The cecum is the largest organ in the abdominal cavity and holds approximately 40% of the GI contents.
• •Rabbits exhibit cecotrophy, which means they consume soft cecotrophs, also known as “night feces.” Antiperistaltic contractions in the colon retrograde non-fiber particles and fluid back into the cecum for fermentation and the formation of cecotrophs, which are an important source of B-vitamins, electrolytes, and nitrogen.
• •The skeletal system is light and delicate compared with most mammals. The skeleton makes up 8% of the total body weight in rabbits, as opposed to 13% of the total body weight in cats.

Key Point.

Red, pink, or orange discoloration of the urine occurs periodically in healthy rabbits. The color may be caused by porphyrin pigments or food-related metabolites excreted in the urine. Cytologic examination of the urine for red blood cells will help distinguish porphyrinuria from hematuria.

• •Calcium and phosphorus are excreted primarily through urine in rabbits. Thus, the urine may be thick and creamy due to calcium carbonate precipitate. Calcium is excreted in the bile in most other mammals.
• •In rabbits, high total leukocyte counts may not be characteristic of acute inflammation from infectious causes. Instead, the distribution of the white blood cells (WBCs) shifts from a normally high lymphocyte/low neutrophil ratio to neutrophilia and lymphopenia.

Reproductive Characteristics

• •Sexual maturity varies in different breeds. As a general rule, females (does) sexually mature at approximately 4 to 8 months of age and males (bucks) sexually mature around 6 to 10 months of age.
• •Females have a silent estrus and are induced ovulators.
• •Breeding seasons are influenced by day length and temperature, though mating can occur year-round when environmental conditions are controlled. Gestation lasts for an average of 30 to 33 days. Pseudocyesis may last 17 days.
• •Depending on the breed, litters range from 4 to 10 kits. Primaparous does usually have smaller litters. Kits are born blind and hairless and remain in the nest for approximately 3 weeks.
• •Does have four and five pairs of mammary glands and nipples spread from the axilla down to the inguinal region. Does usually nurse only once daily for 3 to 5 minutes.
• •Neonatal rabbits are totally dependent on milk up to day 10. Rabbit milk varies with stage of lactation but is approximately 13% protein, 9% fat, and 1% lactose. Small amounts of solid feed and hay can be digested around day 15 and cecotrophy commences on day 20.

Normal Parameters

Reference ranges for physiologic values are listed in Table 176-1. Reference ranges for hematologic values, serum biochemical values, and urinalysis are listed in Table 176-2, Table 176-3, Table 176-4 .

Table 176-1.

REFERENCE RANGES FOR PHYSIOLOGIC VALUES IN RABBITS

Temperature		38–40°C
Heart rate		130–325 beats/min
Respiratory rate		32–60/min
Life span		5–9 yrs
Blood volume		55–65 ml/kg
Food consumption		50 g/kg/day
Water consumption
	General population	50–100 ml/kg/day
	Breeding does	<900 ml/kg/day

Table 176-2.

REFERENCE RANGES FOR HEMATOLOGIC VALUES IN RABBITS

Erythrocytes		5.1–7.9 × 106 m3
Hematocrit		33%–50%
Hemoglobin		10.0–17.4 g/dl
Mean corpuscular volume		57.8–66.5 μm3
Mean corpuscular hemoglobin		17.1–23.5pg
Mean corpuscular hemoglobin concentration		29%–37%
Platelets		250–650 × 103/mm3
Leukocytes		5.2–12.5 × 103/mm3
	Neutrophils	20%–75%
	Lymphocytes	30%–85%
	Monocytes	1%–4%
	Eosinophils	1%–4%
	Basophils	1%–7%

Table 176-3.

REFERENCE RANGES FOR SERUM BIOCHEMICAL VALUES IN RABBITS

Albumin	2.4–4.6 g/dl
Alkaline phosphatase	4–16 U/L
Amylase	166.5–314.5 U/L
Bicarbonate	16–38 mEq/L
Blood urea nitrogen	13–29 mg/dl
Calcium	5.6–12.5 mg/dl
Chloride	92–112 mEq/L
Cholesterol	10–80 mg/dl
Creatinine	0.5–2.5 mg/dl
Globulin	1.5–2.8 g/dl
Glucose	75–155 g/dl
Glutamic-oxaloacetic transaminase	14–113 U/L
Glutamic pyruvate transaminase	48–80 U/L
Lactic dehydrogenase	34–129 U/L
Phosphorus	4.0–6.9 mg/dl
Potassium	3.6–6.9 mEq/L
Serum protein	5.4–8.3 g/dl
Sodium	131–155 mEq/L
Total bilirubin	0.0–0.7 mg/dl
Total lipids	243–390 mg/dl

Table 176-4.

REFERENCE RANGES FOR URINALYSIS IN RABBITS

Urine volume
	Large breeds	20–350 ml/kg/day
	Average breeds	130 ml/kg/day
Specific gravity		1.003–1.036
Average pH		8.2
Crystals present		Ammonium magnesium phosphate, calcium carbonate monohydrate, anhydrous calcium carbonate
Casts, epithelial cells, or bacteria present		Absent to rare
Leukocytes or erythrocytes present		Occasional
Albumin present		Occasional in young rabbits

PATIENT MANAGEMENT

Caging

• •Cages or hutches can be purchased or constructed. Cages should be large enough to allow free movement. Small breeds, which weigh up to 2 kg, require a minimum of 1.5 ft² of floor space per animal. Large breeds, which weigh 5 kg or more, require at least 5 ft² of floor space per animal. Cages should be at least tall enough to allow the rabbit to stand on its hind limbs and be easy to clean.
• •Cages with plastic bottoms and wire tops are easy to clean and are well ventilated. Wire mesh flooring may also be used; however, provide a solid area for the rabbit as wire flooring may predispose rabbits to sore hocks. Use 14-gauge wire with the mesh openings no greater than 1 × 2.5 cm to prevent the rabbit from getting its feet caught.
• •Straw or hay bedding should be provided in one area of the cage. Soiled bedding should be cleaned out daily. Because most rabbits are fastidious and prefer to defecate and urinate in one spot, they often can be trained to use a litterbox.
• •Rabbits can be housed indoors or outdoors at temperatures ranging from 40°F to 80°F. Rabbits are very susceptible to heat stroke in ambient temperatures above 85°F. If outdoor housing is used, provide ventilation or protection from direct sunlight. In temperatures below 40°F, provide heat or protection from cold.
• •Rabbits should be allowed time out of the cage regularly for exercise and socialization. However, they should always be supervised, as they may chew on dangerous objects such as electrical cords and poisonous plants.

Diet

• •Free-choice timothy or coastal hay should be provided to maintain the rabbit's dental and GI health. High-fiber diets are required for proper wearing of the continuously growing teeth and have a protective effect against enteritis. Inadequate fiber in the diet results in cecocolic hypomotility and ultimately changes in cecal microflora.
• •A variety of vegetables and fresh, leafy greens such as dandelion greens, cilantro, parsley, and romaine lettuce should be offered as a salad one to two times daily.
• •Pelleted diets are balanced and convenient; however most of these are alfalfa based and are low in fiber. Most commercial pellets are nutrient dense (high in protein and digestible carbohydrates) and can predispose rabbits to obesity. High-fiber, timothy-based pellets (Oxbow Pet Products, Murdock, NE; www.oxbowhay.com) are preferable over alfalfa-based pellets.
• •The high level of calcium in alfalfa diets may result in hypercalciuria or urinary calculi.
• •Rabbits like sweet foods. A limited amount (approximately 2 tablespoons per 2 pounds of body weight) of fruits such as papaya, melon, or berries can be provided as a treat or to entice an anorectic animal to eat.
• •Foods high in starches or fat such as seeds, nuts, bread, and corn are not advisable as they can predispose rabbits to obesity and GI disease.
• •Fresh water should always be available. Rabbits have a higher water intake than many other mammals. Their daily average water intake is approximately 50-150 ml/kg of body weight. Rabbits fed a large amount of leafy greens will have lower water intake.

Clinical Techniques

Restraint

Key Point.

Restrain rabbits gently but firmly for most procedures. Inadequate restraint can result in a spinal fracture in the rabbit if it is allowed to kick with its hind legs. Support the hindquarters when carrying or lifting a rabbit to prevent spinal injuries.

• •Carry the rabbit with its head tucked under one arm while supporting the body with your forearm; stabilize the back and rump with the other hand.
• •Alternatively, while supporting the back of the rabbit against your body, the forelegs can be grasped between the fingers of one hand while the hind limbs are supported firmly between the fingers of your other hand. This method is effective for examining the ventrum of the patient. (Fig. 176-1 )
• •When examining a patient on a table, keep the rabbit close to your body and always keep a hand on it to prevent it from jumping off the table (Fig. 176-2 ).
• •An especially nervous or aggressive rabbit may need to be wrapped securely in a towel to prevent injury to itself and to the handler. Some rabbits also calm down if their eyes are covered with a hand or towel.

Figure 176-1.

To examine the ventrum and anal area, cradle the rabbit as shown. Be sure to provide support to the hind limbs.

Figure 176-2.

Proper method for restraining a rabbit.

Diagnostic Techniques

Venipuncture

Blood can be collected from the jugular, lateral saphenous, cephalic, and lateral ear veins. Rabbit veins are thin and fragile, so small-gauge needles (i.e., 25-gauge or smaller) should be used. To prevent hematoma formation, apply direct pressure to the venipuncture site for several minutes. Pluck or wet down the fur from the site for better visibility of the vein.

• •Jugular veins lie superficially in the jugular furrow. Hold the rabbit at the edge of a table with the neck held in extension. This technique can be difficult in females with large dewlaps and should not be done for patients in respiratory distress. If anesthetized, the rabbit can be placed in dorsal recumbency with the neck extended down over a table edge for better visibility of the jugular veins.
• •The lateral saphenous vein is the preferred site for obtaining blood samples for routine blood tests. A fairly large volume of blood can be collected from this vein, especially in medium and large-sized rabbits. Have the handler place the rabbit in either lateral or sternal recumbency with the hind end directed towards the edge of the table. Have the handler hold off the saphenous vein by hooking one or more fingers around the back of the back leg proximal to the stifle; encircling and squeezing the proximal thigh too tightly will cause the vein to collapse. Wet down or pluck the fur from the mid-thigh region to better visualize the vein. Apply direct pressure after venipuncture to prevent hematoma formation.
• •Cephalic veins can be used to collect small volumes of blood. Place the rabbit in sternal recumbency and encircle the foreleg around the elbow to extend the leg. Use either a tuberculin or insulin syringe to minimize the risk of collapsing the vein with too much negative pressure.
• •Plucking the hair over the vein is easier than shaving fine fur.
• •The lateral ear vein can be used for blood collection in some large rabbits. Use extreme caution however, as thrombosis of the vein can result in sloughing of the pinnae.

Radiography

• •Radiographs of the head can provide important information about the sinuses and the dental roots. Sedation is usually required.
• •Rabbits have very small thoracic cavities. Thoracic radiographs are useful in differentiating between pneumonia, cardiac disease, and neoplasia.
• •The stomach and cecum are often full of ingesta and may obscure abdominal organs. However, moderate to severe gas distention of the stomach, cecum, or intestines suggests GI stasis.

Ultrasonography

• •Ultrasound examination can provide useful information about abdominal organs such as the liver, spleen, kidneys, and reproductive tract.
• •Urinary calculi and sludge can be seen on ultrasonographic examination of the bladder.
• •Guided aspirates of thoracic and abdominal masses can provide representative samples for cytologic examination. However, the patient must be sedated for the procedure, which should only be performed by experienced practitioners.

Treatment Techniques

• •Subcutaneous administration of fluids is acceptable in non-critical cases and may be the only practical route of fluid administration in small rabbits. Estimate daily maintenance fluid needs at 100 to 150 ml/kg/24 hours.
• •Use an indwelling catheter in critical cases.
• •Small-gauge catheters (i.e., 24-gauge) can be placed in the cephalic or lateral saphenous vein in most rabbits.
• •Jugular catheters can be difficult to insert and may require a cutdown procedure.
• •Medications can be administered orally into the lateral cheek pouch. Use liquid or paste preparations when possible because rabbits have a long, narrow oropharynx that makes pill administration difficult.
• •Anorectic animals can be syringe fed specialized hand-feeding formulas for herbivores (Critical Care for Herbivores, Oxbow Pet Products, Murdock, NE; www.oxbowhay.com). A gruel made of moistened rabbit pellets can also be used. Vegetable baby foods are low in energy content and fiber and should only be used short term.
• •
  Nasogastric tubes can be placed in medium-to-large rabbits that require long-term nutritional support or that have had extensive oral surgery. The technique that follows is similar to that for placing a tube in a cat.

  • •
    With manual restraint, place two to three drops of a topical anesthetic (Ophthaine, Solvay Animal Health, Inc., Princeton, NJ) in the mucosa of one nostril. Wait 5 minutes, and then repeat application.
  • •
    Lubricate the tip of a small infant feeding tube (e.g., 5 Fr., Bard-Parker, Becton-Dickenson and Company, Rutherford, NJ) with topical lidocaine (Xylocaine) jelly. Pass the tube medially along the nasal passage to the level of the last rib. The tip of the tube is located in the distal esophagus.
  • •
    Secure the free end of the tube to the skin above the nose and eye with a butterfly tape and suture. An Elizabethan collar may be necessary to prevent the rabbit from dislodging the tube.
• •Dietary supplements containing Lactobacillus spp. may aid in the treatment of enteritis by repopulating the GI tract with healthy bacterial flora, decreasing intestinal or cecal pH, and competing with bacterial pathogens for mucosal attachment sites. Commercial products in paste form are available (e.g., Bene-Bac, Pet-Ag, Inc, Hampshire, IL).
• •Commonly used antibiotics are listed in Table 176-5 .

Table 176-5.

DRUGS COMMONLY USED IN RABBITS

Drug	Dose	Comments
Antimicrobials/Antifungals
Benzathine, penicillin G	42,000–84,000 IU/kg q7d × 3 treatments SC	For treatment of Treponema cuniculi
Chloramphenicol	30–50 mg/kg q12h PO
Ciprofloxacin	10–20 mg/kg q12–24h PO	Have a suspension made by a compounding pharmacist for easy administration
Enrofloxacin	5–15 mg/kg q12h PO, SC, IM	Limit subcutaneous and intramuscular administration due to potential tissue necrosis at injection sites
Gentamicin	4 mg/kg q24h IM, IV, SC	Use with caution or avoid use
Griseofulvin	12.5 mg/kgq12h PO
Penicillin	40,000–60,000 IU/kg q48hr SC	Use with caution
Tetracycline	50 mg/kg q8–12h PO
Trimethoprim/sulfa	30 mg/kg q12h PO, IM, SC
Antiparasitics/Insecticides
Fenbendazole	10–20 mg/kg PO, repeat in 14d
Lime sulfur solution	2.5% dip q7d for 4 weeks	Used in young animals for treatment of mites, fleas, fungal dermatitis
Ivermectin	0.2–0.4 mg/kg q10–14d SC for 2–3 treatments	Effective against ear and fur mites
Piperazine citrate	200 mg/kg; repeat in 2 weeks
Pyrantel pamoate	5–10 mg/kg; repeat in 2 weeks
Pyrethrin products	Topically as directed q7d
Selamectin	6 mg/kg topically
Sulfadimethoxine	50 mg/kg PO first dose, then 25 mg/kg q24h PO for 10–20 days	For treatment of coccidiosis
Tranquilizers/Premedications
Acepromazine	0.5–1.0 mg/kg IM/SC
Atipamazole	Give same volume SC as medetomidine	Reversal for medetomidine
Diazepam	1–3 mg/kg IV, IM	Used in combination with ketamine
Glycopyrrolate	0.01–0.02 SC
Ketamine	20–50 mg/kg IM
Ketamine/acepromazine	40 mg/kg (K)/0.5–1.0 mg/kg (A) IM
Ketamine/diazepam	10–15 mg/kg (K)/0.3–0.5 mg/kg (D) IM, IV
Ketamine/medetomidine	0.15–0.35 mg/kg (M) IM/5–20 mg/kg (K) IV later
Ketamine/midazolam	25 mg/kg (K)/≤ 2 mg/kg (M) IM
Medetomidine	0.25 mg/kg IM
Midazolam	1–2 mg/kg IM or slow IV
Propofol	2–15 mg/kg IV
Xylazine	1–5 mg/kg SC, IM
Analgesics
Aspirin	10–100 mg/kg q8–24h PO
Buprenorphine	0.01–0.05 mg/kg q6–12h SC, IM, IV
Butorphanol	0.1–1.0 mg/kg q4–6h SC, IM, IV
Carprofen	1.0–2.2 mg/kg q12h PO, SC, IM
Flunixin meglumine	1.1 mg/kg q12–24h SC, IM
Ibuprofen	2.0–7.5 mg/kg; PO q12–24h
Ketoprofen	1 mg/kg q12–24h IM
Morphine	2–5 mg/kg q2–4h SC, IM
Oxymorphone	0.05–0.20 mg/kgq8–12h SC, IM

Tranquilization and Anesthesia

• •Injectable tranquilizers are suitable for short diagnostic or surgical procedures. Ketamine (5-10 mg/kg) and medetomidine (Domitor, Pfizer Animal Health, Exton, PA) (0.15-0.18 mg/kg) in combination given IM or IV provides adequate relaxation and sedation.
• •Use inhalant anesthesia for long or painful surgical procedures. Clinically, isoflurane and sevoflurane are commonly used. Anesthetic induction and recovery are usually faster with sevoflurane. Gas anesthesia in rabbits can be induced by face mask or in an induction chamber. Premedicate with a combination of ketamine with medetomidine, diazepam, or midazolam as needed, especially if using isoflurane. Buprenorphine and glycopyrrolate can also be given as needed. Gradually increase the concentration of isoflurane over several minutes until a surgical plane of anesthesia is reached. Anesthesia usually is maintained at 0.25% to 2% isoflurane in oxygen. With sevoflurane, use an induction level of 5% to 8%, reducing to 0.5% to 3% for maintenance.

Key Point.

Intubation can be difficult because of the long, narrow oropharynx, large incisors, and large fleshy tongue that can obstruct the view of the pharyngeal cavity. Intubation is most successful in large rabbits; consider intubating medium-sized rabbits for long surgical procedures. However, repeated attempts to intubate can damage the larynx, causing soft tissue trauma or laryngospasm that can be fatal after the rabbit is extubated. If laryngeal trauma occurs during intubation attempts, abandon the procedure and use a face mask, or postpone the procedure to another day. Corticosteroids may or may not be helpful in decreasing inflammation of the larynx and tracheal mucosa.

• •
  The following technique can be used to intubate medium to large rabbits.

  • •
    Administer ketamine (5-10 mg/kg IM) and medetomidine (0.15-0.35 mg/kg IM) in combination. Supplemental isoflurane may be necessary to further relax the rabbit for intubation.
  • •
    Place the rabbit in sternal recumbency. Extend the neck straight up and forward.
  • •
    Place the tip of the short, flat-blade laryngoscope blade (i.e., Miller blade), at the base of the tongue. Hook the base of the blade against the top front incisors, and use the blade as a lever to see the glottis. Pass a small endotracheal tube along the blade into the opening of the glottis. Depending on their size, most rabbits require a 2.5- to 5.0-mm endotracheal tube. The glottis cannot be seen while trying to pass the tube.
  • •
    Alternatively, the glottis can be visualized with an otoendoscope or endoscopic telescope in a sedated rabbit. The endotracheal tube is passed along the endoscope and inserted as above.
  • •
    Use a face mask to maintain anesthesia during short procedures or if intubation attempts are unsuccessful.
  • •
    Monitor all rabbits closely during any anesthetic episode. A Doppler, EKG monitor, and pulse oximeter can be used to monitor heart rate and oxygen saturation.

DERMATOLOGIC PROBLEMS

Dermatitis/Alopecia

Etiology

• •Mange, fur, and ear mites cause localized or diffuse dermatitis, alopecia, or both. The area involved depends on the type of mite (see “Ear Mites”; “Fur and Mange Mites”).
• •Dermatophytosis is associated with alopecia and a scaly dermatitis, particularly around the head and ears (see “Superficial Mycosis”).
• •Fur-barbering is common in rabbits on diets deficient in roughage. A high incidence of barbering in does is seen during breeding season; this is probably related to hormonal influences.
• •Ptyalism, alopecia, and dermatitis around the mouth are associated with malocclusion.
• •Moist dermatitis of the dewlap is common in does during breeding season, especially in warm or humid environments.
• •Moist dermatitis with erythema and ulceration of the ventral abdomen and perineal area results from urine scald. Urine scald is associated with urinary incontinence, cystitis, excessive calcium in the urine, uterine adenocarcinoma, or poor management and unclean caging.
• •Treponematosis (rabbit syphilis), caused by Treponema paraluiscuniculi causes a scaly dermatitis in the genital area. The nose, lips, and periorbital area are less commonly involved.

Clinical Signs

• •Mite infestations produce clinical signs characteristic of the mite involved (see “Ear Mites”; “Fur and Mange Mites”). Pruritis is common with sarcoptic mite infestations.
• •Dermatophytes cause a partial alopecia with slight scaliness and erythema. Rabbits are usually pruritic.
• •Fur-barbering is characterized by alopecia of the dewlap, back of the neck, and paws. The underlying skin is normal.
• •Moist dermatitis of the dewlap or ventral abdomen is typically erythematous with scaling and ulceration. The fur around the alopecic areas is moist. Rabbits sometimes self-mutilate this area; use a collar to prevent further trauma.

Diagnosis

Determine the primary cause of the alopecia to make a diagnosis.

• •Examine skin scrapings of scaly areas for evidence of adult mites or eggs.
• •Obtain samples of fur and keratin debris for fungal culture.
• •Submit a skin biopsy specimen for histologic examination if the causative agent cannot be determined by other diagnostic tests.
• •Examine the teeth in rabbits with excessive ptyalism and alopecia around the mouth (see “Malocclusion”).
• •Obtain abdominal radiographs of rabbits with urine scald for evidence of cystic calculi. Submit a urine sample for urinalysis and bacterial culture and sensitivity testing.
• •Submit a blood sample for serum biochemical analysis to check for high concentrations of calcium, blood urea nitrogen, and creatinine.

Treatment

Treatment is directed toward the primary cause (see “Ear Mites”; “Fur and Mange Mites”; “Hairballs”; “Malocclusion”; “Treponematosis”; “Cystitis”; “Superficial Mycosis”).

• •Correct the diet to include adequate roughage if fur-barbering is suspected. Perform ovariohysterectomy in females with a suspected hormonal basis for fur-barbering.
• •Treat adult rabbits with suspected mite infestations with ivermectin (see Table 176-5).
• •Treat treponematosis with penicillin (see “Treponematosis”).
• •Treat dermatophytosis with antifungal agents, administered topically or orally depending on the extent of lesions.

Ear Mites (Psoroptes cuniculi)

Etiology

• •Ear mites are common ectoparasites.
• •Psoroptes cuniculi is a large, non-burrowing mite that spends its 3-week life cycle on the host rabbit.
• •Mites have biting mouthparts and cause inflammation by biting and chewing the epithelial surface of the skin.

Clinical Signs

• •Infestation with psoroptic mites usually is confined to the inner epithelial surface of the ear. Lesions begin in the concha and eventually extend to the inner surface of the pinna. Other areas, such as the dewlap and feet, sometimes are involved.
• •Lesions consist of thick, dry, flaky, gray-to-tan crusts on the inner surface of the ear pinna. The underlying epithelial surface is raw, inflamed, and hemorrhagic.
• •Psoroptic mites cause intense pruritus. Affected rabbits shake their heads or scratch their ears with the rear feet.

Diagnosis

• •Psoroptic mites are large and sometimes visible with the unaided eye.
• •Use an otoscope to detect movement of the mites within the ear canal.
• •Microscopic examination of crusts and exudate usually reveals mites and eggs.
• •Check rabbits with mild cases of otitis for the presence of mites.

Treatment

• •Ivermectin is effective against ear mites (see Table 176-5). Repeat treatment in 3 weeks. A combination therapy of ivermectin and topical acaricides can be used for severe infestations.
• •Because the lesions are usually very painful, and the aural crusts resolve after ivermectin treatment, avoid pulling off the crusts to clean the ears. Ears can be cleaned 1 to 2 weeks after pain subsides and lesions heal.
• •Apply an antibiotic cream topically if a secondary bacterial infection is present. Topical application of anti-inflammatory agents may be beneficial once bacterial infection is under control.

Prevention

• •Psoroptic mites are transmitted easily between rabbits. Isolate affected rabbits from healthy rabbits.
• •Keep cages and bedding clean to minimize spread through contaminated fomites. The environment should be treated with flea products safe for cats to prevent re-infection.

Fur and Mange Mites

Etiology

• •Cheyletiella parasitivorax is the common fur mite of rabbits. Because of its large, white, flake-like appearance, it is often called “walking dandruff.” Infestations with other species of Cheyletiella occasionally occur. Listrophorus gibbus is a less common fur mite and is considered nonpathogenic.
• •Cheyletid mites are non-burrowing, obligate parasites with an approximate 35-day life cycle.
• •Cheyletid mites may cause a self-limiting, transitory dermatitis in humans.
• •The cheyletid mite is a known vector of rabbit myxomatosis in Australia.
• •Mange mites (e.g., Sarcoptes scabiei, Notedres cati) occur infrequently in rabbits.

Clinical Signs

• •Lesions produced by cheyletid mites consist of a scaly dermatitis with a flaky, grayish-white exudate. Mites primarily inhabit the dorsal trunk and scapular region. The underlying skin may appear erythematous and inflamed. Pruritus is not a major clinical sign.
• •Other areas of the body can be involved in severe infestations. Rabbits may act as if they are depressed and in pain.
• •Mange mites produce a crusty dermatitis with alopecia.
• •Intense pruritus results from mites burrowing in the epidermis.

Diagnosis

• •Cheyletid mites are easily identified through microscopic examination of cellophane tape preparations of affected skin. Press a strip of cellophane tape to the skin lesions to obtain a sample.
• •Deep skin scrapings are necessary to find mange mites. Results are sometimes falsely negative. Differential diagnosis then is based on the typical clinical signs of each type of mite.

Treatment

• •Ivermectin (0.4 mg/kg SC q10-14d for three treatments) is effective against most mites that infest rabbits. The treatment period should extend through the life cycle of the mite.
• •Topical acaricides, including pyrethrins, carbamates, and lime sulfur solution dips (see Table 176-5), are also effective against fur and mange mites. However, these products should be used cautiously as they have been associated with toxicity in rabbits.
• •Cheyletid mites can exist off the host for short periods. Treat the home environment with parasiticides and eliminate potential fomites.
• •The mite is highly contagious and all rabbits in contact with the affected rabbit should also be examined and treated. Other pets in the household kept in contact with infested rabbits should be examined.

Myiasis

Etiology

• •Myiasis (fly larval infestation) occurs in rabbits kept outdoors in warm weather. Rabbits can become infested with cuterbrid larvae or maggots of the flesh fly. Maggot infestation is also known as “fly strike.”
• •Obesity, perineal dermatitis, and urine scald predispose rabbits to maggot infestation.

Clinical Signs

• •Although some rabbits can be asymptomatic, rabbits may appear to be in pain, reluctant to move, or lame.
• •Cuterebrid larvae burrow into subcutaneous tissue and cause one or more firm, fistulated, subcutaneous swellings surrounded by necrotic tissue. Areas commonly involved include the ventral cervical, inguinal, hindquarter, dorsum, and axillary regions.
• •Aberrant migrations to the nasal passages, eyes, sinuses, and ear canals have also been described. An infection of the eye is known as ophthalmomyiasis.
• •Maggots usually burrow through large, moist necrotic areas at the base of tail and dorsum, as these are difficult areas to groom for overweight rabbits.
• •Secondary bacterial infections of the lesion are common.

Diagnosis

Diagnosis is based on a history of outdoor housing, clinical signs, and presence of larvae in wounds.

Treatment

• •Sedation and pain medication are usually indicated before clipping soiled fur and removing larvae from the wounds.
• •Remove cuterebrid larvae intact with hemostats if possible. Avoid rupture of the larvae.
• •Remove maggots from the necrotic wounds.
• •Thoroughly debride wounds of necrotic tissue. Perform complete surgical excision of any abscessed skin. Clean the surgical site daily and allow the wound to heal by second intention.
• •Ivermectin (0.4 mg/kg SC q14d for two treatments) can be administered to kill larvae, but the larvae still need to be removed from the sites.
• •Observe affected rabbits carefully for several weeks for additional lesions.
• •Antibiotics with good skin activity such as trimethoprim-sulfa (30 mg/kg PO bid) are recommended for treating secondary bacterial infections.

Prevention

• •Keep outdoor rabbits in screened hutches, especially during summer and fall.

Superficial Mycosis

Etiology

• •Trichophyton mentagrophytes is the most common dermatophyte that affects rabbits and is usually self-limiting. Infections with Microsporum spp. and other dermatophytes occur much less frequently.
• •Infection occurs by direct contact with infected animals, contaminated fomites, or asymptomatic carriers.

Clinical Signs

• •Lesions usually appear on the head and ears and can extend to the neck, legs, feet, and nail beds.
• •Lesions consist of areas of alopecia with erythema and scaly dermatitis. Rabbits are usually pruritic. Alopecic areas may be circular with slightly raised edges.

Diagnosis

Dermatitis resulting from dermatophytosis must be differentiated from other possible causes, including mites, fur-barbering, and bacterial dermatitis.

• •Submit samples of fur from the edge of the lesion for culture on dermatophyte-culture medium.
• •T. mentagrophytes does not fluoresce with ultraviolet light.
• •The organisms can be demonstrated with either periodic acid schiff (PAS) or silver stains in histologic sections of skin biopsy specimens.

Treatment

Treatment of dermatophytosis is directed toward elimination of the organism while preventing spread of disease. Other animals and humans, especially children, are susceptible to infection.

• •Clip affected areas and apply topical antifungal agents daily for 3 to 4 weeks.
• •For extensive lesions, lime sulfur solution dips (2%–3%) given every 5 to 7 days are often effective for treating fungal dermatosis. Continue treatment for 4 weeks.
• •Griseofulvin is effective if given daily for 4 weeks or until the infection clears (see Table 176-5). Give griseofulvin with fats to enhance absorption. Gris-PEG (Allergen, Inc.), an ultramicronized formulation for improved absorption, is given at one-half the normal dose. Griseofulvin should be administered cautiously, because it can cause bone marrow suppression and panleukopenia at high doses. Do not give it to breeding does, as it may be teratogenic.
• •Instruct owners to wear gloves when handling or treating affected animals because of the zoonotic disease potential.
• •Check other animals in the household for evidence of dermatophytosis.

Prevention

• •Prevent contact with infected animals.
• •Disinfection of the environment is important. Vacuum the contaminated area and wipe down all surfaces with a 1:10 dilution of bleach and water. Foggers containing enilconazole or formaldehyde can be used for carpeted areas.

Ulcerative Pododermatitis (Sore Hocks)

Etiology

• •Ulcerative pododermatitis (sore hocks) usually develops as a result of management-related problems. Soiled or wet bedding, abrasions from flooring, sedentary behavior caused by obesity, small cages that restrict movement, and abrasions from thumping are predisposing factors.
• •Ulcerative granulomatous lesions involve the plantar surface of the hocks and may be unilateral or bilateral. Forepaws are less commonly affected.
• •Secondary bacterial infections, usually S. aureus, are common with severely ulcerated lesions.
• •Chronic infections can develop into abscesses or may spread to underlying bone, resulting in osteomyelitis.

Clinical Signs

• •Early or mild lesions are areas of erythema and thinning fur on the plantar surface of the hock.
• •Lesions may progress to raw, ulcerative sores with scabs. Mucoid, purulent, or thick caseous exudate is present with secondary bacterial infections.
• •Severe lesions cause lameness and reluctance to move. Rabbits may be anorectic and depressed.

Diagnosis

• •Diagnosis is based on clinical signs. If wounds appear infected, submit samples for bacterial culture and sensitivity testing.
• •Radiographs of the hocks may be indicated in severe cases to evaluate underlying bone involvement.

Treatment

• •Correct the predisposing management and environmental factors.
• •Thoroughly clean and debride necrotic wounds. An antibiotic cream such as silver sulfadiazine can be applied topically.
• •Topical astringents such as Domeboro solution (Bayer, Inc., West Haven, CT) are beneficial in treating moist wounds. Apply the solution daily until the wound appears dry.
• •Protect wounds with sterile, soft, padded bandages.
• •Healing is often prolonged. Clean the wound with an antibacterial soak, topical antibiotics, and bandaging, daily or every other day.
• •Systemic antibiotics are necessary if infection is present.

Prevention

• •Wire flooring should be smooth, nonabrasive, and of sufficient width to prevent abrasions. Place soft, dry bedding, such as hay or several thicknesses of newspaper, in one area of the cage.
• •Cages should be clean and of sufficient size to allow free movement.
• •Check the feet and hocks periodically for signs of inflammation.
• •Overweight rabbits should undergo weight reduction to decrease the risk of developing sore hocks.

RESPIRATORY DISEASE

Respiratory disease is common in pet rabbits and can result from many interrelated factors. Historically, Pasteurella multocida has been implicated as the major cause of respiratory disease, though it is probably now less common than in the past. Other bacteria, viruses, and non-infectious causes such as allergens, thoracic/nasal neoplasia, cardiovascular disease, nasal obstruction due to dental disease, and exposure to respiratory irritants should also be considered when working up a patient with respiratory disease.

• •Respiratory irritants such as excessive ammonia in dirty, poorly-ventilated cages, aromatic wood shavings (cedar), and cigarette smoke may predispose some rabbits to respiratory infections.

Upper Respiratory Tract Infection (Snuffles)

Etiology

• •Bacterial agents that haven been implicated in sinusitis and rhinitis in rabbits include: Pasteurella multocida (see Pasteurellosis), Bordetella bronchiseptica, and Staphylococcus and Pseudomonas species.
• •Infections can be transmitted from the doe to offspring or by direct contact with infected rabbits. Infection also may be spread by aerosol (sneezing) or fomites.
• •Chronic disease may be subclinical and precipitated by stress.

Clinical Signs

• •Intermittent episodes of sneezing and rhinitis with serous or mucopurulent nasal discharge are common findings.
• •Exudate can block the nasolacrimal duct resulting in conjunctivitis, serous-to-mucopurulent ocular discharge, and periorbital matting or alopecia. One or both eyes may be affected.
• •Auscultation of the nares and trachea often reveal rattles and rales.
• •Many rabbits have no other clinical signs. Rabbits with severe disease may be anorexic and lethargic.

Diagnosis

Diagnosis of rhinitis is based on clinical signs and isolation of the causative agent through bacterial culture and sensitivity testing.

• •Submit a swab of nasal or conjunctival exudate for bacterial culture and sensitivity testing. Small-tipped culturette swabs are convenient for sample collection (e.g., BBL CultureSwab, Becton, Dickinson & Co., Franklin Lakes, NJ).
• •Skull radiographs provide useful information about the nasal passage and sinuses. Increased opacity may indicate accumulation of exudate. Decreased opacity may indicate lysis from advanced infections or neoplasia. Elongated roots of cheek teeth obstructing the nasal passage may be visible. Thoracic radiographs help differentiate upper airway disease from pneumonia, cardiovascular disease, and thoracic neoplasia.
• •If available, computed tomography (CT) of the skull will provide detailed information about the nasal passages and sinuses.

Treatment

• •Give antibiotics at the first signs of respiratory disease (see Table 176-5). Chloramphenicol, enrofloxacin (Baytril, Bayer Animal Health, Shawnee Mission, KS), trimethoprim-sulfa, or parental penicillin G can be administered until culture results are known. The antibiotic choice may change based on results of bacterial culture and sensitivity testing.
• •If conjunctivitis is present, cannulate and flush the nasolacrimal duct of the affected eye or eyes with sterile water or saline. A topical ophthalmic anesthetic is necessary for this procedure. Repeated flushes of the nasolacrimal duct daily for 2 to 3 days or every 3 days for four or five treatments is most effective. Apply an ophthalmic antibiotic solution such as ciprofloxacin (Ciloxan, Alcon Laboratories, Fort Worth, TX) gentocin, or chloramphenicol four to six times daily for 14 to 21 days.
• •Long-term therapy may be necessary with chronic disease.

Prevention

General preventive measures are described in the following section on Pasteurellosis.

Pneumonia

Pneumonia can be acute or chronic and may occur alone or accompany upper respiratory disease.

Etiology

• •Pasteurellosis is the most common cause of pneumonia in rabbits, though other bacteria such as B. bronchiseptica and S. aureus may also be involved. The infection spreads to the lungs from the upper respiratory tract through the trachea or, less frequently, through the bloodstream.
• •Stress is an important factor in disease. Sudden temperature changes, poor sanitation, or poor ventilation in high-ammonia areas contribute to the development of disease.

Clinical Signs

• •Chronic pneumonia is characterized by labored breathing, weight loss, cachexia, and anorexia.
• •Clinical signs are often inapparent until disease is advanced.
• •Acute death is common in young rabbits.

Diagnosis

Diagnosis of pneumonia is based on clinical signs and supportive diagnostic tests.

• •Auscultate the thorax for crackles, expiratory wheezes, or decreased lung sounds over areas of consolidation or abscess.
• •Thoracic radiographs help determine the extent of disease and may reveal lung lobe consolidation, air bronchograms, or well-delineated soft-tissue opacities if pulmonary abscesses are present.
• •Results of a complete blood count (CBC) may reveal a relative increase in heterophil numbers or a reversal of the lymphocyte/heterophil ratio, indicating an inflammatory response.
• •Tracheal washes are very difficult in rabbits because of the anatomy of the oropharynx and are not recommended.
• •Postmortem lesions may include acute fibrinopurulent pneumonia, pleuritis, and septicemia.

Treatment

• •Parenteral antibiotic therapy is preferred in rabbits with severe pneumonia.
• •Supportive therapy includes supplemental fluids, vitamins, and force-feeding of anorectic animals.
• •If an indwelling catheter can be placed, give fluids intravenously. Administer subcutaneous fluids if catheter placement is too stressful.
• •Force-feed anorectic animals. Hold recumbent animals sternal while feeding and give food slowly to minimize stress and to prevent aspiration.
• •Place severely dyspneic rabbits in an oxygen cage.
• •Euthanasia often is elected for severely debilitated rabbits with advanced disease.

Pasteurellosis

Etiology

• •Pasteurellosis is an endemic bacterial disease of rabbits. It is caused by Pasteurella multocida, a small, gram-negative, bipolar coccobacillus.
• •Infection is spread by direct contact with infected rabbits or contaminated fomites, aerosolization, or from does to offspring during birth and nursing.
• •Bacteria colonize the soft palate and nasal turbinates and may produce a lifelong infection. Infection may be subclinical with intermittent episodes of mucopurulent nasal discharge, which often is precipitated by stress.
• •
  Spread from the nasal cavity can occur by several routes:

  • •
    The eustachian tube to the middle or inner ear, meninges, and brain
  • •
    The nasolacrimal duct to the conjunctiva
  • •
    The trachea to the lungs
  • •
    Hematogenously to the peripheral lymph nodes, reproductive tract, lungs, or other organs.
• •Pasteurella infections can also result in abscesses in the subcutaneous tissues, retrobulbar space, and internal organs. Culture of the abscess capsule wall is recommended however, since other bacterial organisms have also been implicated.

Clinical Signs

Clinical signs of disease depend on the site and chronicity of infection.

• •Respiratory signs associated with pasteurellosis include rhinitis, conjunctivitis, and pneumonia.
• •Neurologic signs, including head tilt, torticollis, nystagmus, and facial nerve deficits, can be seen with infections of the middle or inner ear, meninges, or brain.
• •Abscesses can occur in the joints, tooth roots, various organs, and in subcutaneous tissue. Exudate is typically white, thick, and caseous.
• •Abscesses in the retrobulbar space often result in exopthalmus and subsequent ocular infections and corneal ulcers.
• •Generalized illness, fever, and peracute death may occur from septicemia or pleuropneumonia of more pathogenic strains of P. multocida.

Diagnosis

• •Submit samples from exudate, blood, or tissue for bacterial culture and sensitivity testing.
• •Isolation of P. multocida is sometimes difficult. To maximize culture results, the swab should be inoculated onto a blood agar plate or Cary-Blair transport medium. Additionally, when collecting samples from an abscess, the swab should be directed toward the inner wall of the capsule as the necrotic centers are often sterile.
• •Enzyme-linked immunosorbent assays (ELISAs) have been developed to detect antibodies to P. multocida and may be helpful in detecting subclinical carriers. The test requires whole blood or serum and is reported as high positive, low positive, or negative. Results must be interpreted with discretion, as low positives can occur with antibodies of closely related, but normal bacteria or from maternally acquired antibodies. False negatives may occur early in an infection or in immunocompromised individuals.
• •Radiographs of affected areas can help delineate the extent and severity of the disease.

Treatment

Key Point.

Successful treatment of pasteurellosis can be difficult, especially in rabbits with advanced disease.

• •Antibiotic therapy should be based on culture and sensitivity testing. Enrofloxacin (5-10 mg/kg PO q12h) and chloramphenicol (50 mg/kg PO q12h) administered for several months have been used successfully in the treatment of rabbits with chronic pasteurellosis.
• •Injections of penicillin G benzathine/penicillin G procaine (40,000 IU/kg SC q24h for 2 weeks, then q48h for 2 or more weeks) have also had reported success in the treatment of pasteurellosis.
• •Perform complete surgical excision of subcutaneous abscesses; the thick-capsule wall and caseous nature of the exudate preclude simple lancing and draining.
• •Mandibular or joint abcesses require extensive debridement and wound care (see Mandibular and Joint Abscesses).
• •Daily management includes thorough cleaning and flushing until healing is well advanced.
• •Debilitated rabbits require supplemental fluids, force-feeding, and general nursing care.

Prevention

• •Pasteurellosis is an endemic disease in rabbits, and control is difficult. Colonies are kept Pasteurella-free through serologic testing and strict isolation and sanitation procedures.
• •Prevention involves isolation of healthy animals from rabbits with clinical signs of disease. Eliminate rabbits with evidence of disease from breeding colonies.
• •Closely examine pet rabbits for signs of respiratory disease before purchase. New rabbits should be quarantined from other rabbits in the household until their disease status is known.
• •Minimizing stress, feeding the rabbit a proper diet, and using good husbandry practices are important in preventing the spread of pasteurellosis.

GASTROINTESTINAL DISEASES

Rabbits often are anorectic when a primary GI disease is involved. Anorexia is also common with metabolic abnormalities such as kidney disease and lead toxicoses and with any severe systemic infection. A change in food intake can alter the flora of the GI tract, resulting in the excessive production of volatile fatty acids and subsequent change in cecal pH. This can lead to the over-population of pathogenic bacteria resulting in either diarrhea or GI stasis.

Diarrhea/Enteritis/Enterotoxemia

Etiology

Key Point.

Lack of roughage in the diet, stress, and antibiotic therapy are all factors that contribute to disruptions in cecal microflora and pH, which can result in diarrhea.

• •Diets high in digestible carbohydrates contribute to overgrowth of pathogenic bacteria by supplying a ready source of fermentable products. Toxins produced by these bacteria are primary factors in enterotoxemia.

Bacterial Pathogens

• •Clostridium spiroforme, a gram-positive, anaerobic, spore-forming rod, is one of the primary pathogens in bacterial enteritis in rabbits. Although this organism can be present as normal GI flora, with a ready supply of fermentation products (digestible carbohydrates) it produces iota toxin, which causes severe enterotoxemia.
• •Escherichia coli causes diarrhea in young rabbits and has a variable morbidity and mortality rate depending on the pathogenicity of the serotype involved. E. coli is not part of the normal gut flora but often is found in large numbers in the cecum of rabbits with diarrhea. The bacteria attach to the mucosal epithelium, causing necrosis and disruption of normal intestinal and cecal function. Enterohemorrhagic E. coli have also been isolated from rabbits and may pose a zoonotic risk.
• •Clostridium piliforme (formerly Bacillus piliformis), which causes Tyzzer's disease, is associated with acute diarrhea and death, primarily in young weanling rabbits. C. piliforme may be a subclinical inhabitant of the gut. With stress, the bacteria proliferate and cause severe epithelial necrosis of the cecum, colon, and distal ileum.
• •Lawsonia intracellularis, an intracellular, gramnegative, curved to spiral-shaped bacteria has been associated with proliferative enterocecocolitis in weanling rabbits.

Viruses

• •A coronavirus has been described as a cause of diarrhea and subsequent death in 3- to 10-week-old rabbits. The virus denudes the intestinal villi; diagnosis is made by identifying the virus in feces or cecal contents.
• •Rotavirus may be present as normal flora, but may act as a mild pathogen by destroying cells that produce disaccharidases and by contributing to carbohydrate overload. Severity of the diarrhea is variable and is affected by other contributing microorganisms.

Parasites

• •Intestinal coccidiosis is primarily a disease of young rabbits. Twelve species of intestinal Eimeria infect rabbits. Diarrhea secondary to intestinal coccidiosis is usually mild; however, coccidia may predispose rabbits to bacterial enteritis (see “Coccidiosis”). The highly pathogenic Eimeria stieda infects the liver.
• •Cryptosporidia parvum may cause a transient diarrhea in young rabbits for 3 to 5 days. No known treatments are available.

Management Related Factors

• •Antibiotic therapy can cause suppression of normal gut flora and overgrowth of pathogenic bacteria. Diarrhea is associated with antibiotics that are active against gram-positive aerobes and selective gramnegative anaerobes. Antibiotic-induced diarrhea has been associated with the oral administration of lincomycin, clindamycin, erythromycin, ampicillin, amoxicillin, cephalosporins, and penicillin.
• •Stress is a major factor in diarrhea. Stress-related epinephrine release may have a direct effect on intestinal motility and digestion, allowing overgrowth of pathogenic organisms.

Clinical Signs

• •Diarrhea may vary from soft, pasty stool to a profuse, malodorous liquid. Mucus and blood may also be present. The perineal region and hindlimbs are often stained with feces.
• •Rabbits with mild diarrhea may be otherwise normal. Severe diarrhea may be accompanied by lethargy, weight loss, anorexia, and dehydration.
• •Intestinal gas often is detected on abdominal palpation.
• •Sudden death may be the only clinical sign in peracute disease. In chronic cases, the rabbit has intermittent bouts of diarrhea and anorexia and may have progressive weight loss.

Diagnosis

Diagnosis of the primary cause is based on clinical signs, history, and specific tests.

• •Dietary history is very important. Determine the fiber content of the normal feed and the amount of supplemental roughage.
• •Identify bacterial pathogens by submitting fecal samples for aerobic and anaerobic bacterial culture and sensitivity testing.
• •Do a direct fecal smear or fecal flotation to check for spore-forming gram-positive bacteria and coccidia.
• •Results of serum biochemical analysis often reveal electrolyte and metabolic abnormalities in animals with moderate-to-severe diarrhea.

Treatment

• •Correct the diet in animals on marginal or deficient dietary fiber levels.
• •Dietary Lactobacillus supplements such as Bene-bac may help repopulate the GI tract with normal flora.
• •Metronidazole (20 mg/kg PO, IV q12h) has been effective in treating rabbits with enterotoxemia caused by C. spiroforme.
• •Enrofloxacin (10 mg/kg PO q12h) or trimethoprim/sulfa (30 mg/kg PO q12h) is indicated if E. coli bacterial enteritis is suspected.
• •Chloramphenicol (30-50 mg/kg PO q12h) can be used to treat proliferative enteritis caused by L. intracellularis.
• • Oral administration of antibiotics is effective in rabbits with mild-to-moderate diarrhea. Give antibiotics parenterally in rabbits with severe clinical signs. Avoid antibiotics that may induce enteritis.
• •Intravenous fluid therapy is indicated for rabbits with moderate-to-severe diarrhea. Subcutaneous fluids are usually adequate for cases with mild diarrhea.
• •Anorectic animals should be force fed replacement diets such as Critical Care for Herbivores (Oxbow Pet Products, Murdock, NE; www.oxbowhay.com).
• •If young rabbits test positive for coccidiosis, administer appropriate therapy (see Coccidiosis).

Prevention

• •Instruct owners to feed their rabbits proper diets with an adequate content of indigestible fiber, such as timothy hay.
• •Minimize stress in young or weanling rabbits. Sudden temperature changes, changes in food, overcrowding, or poor sanitation contribute to disease.
• •Isolate diseased animals from healthy rabbits.
• •Screen young rabbits for coccidiosis or give prophylactic therapy.

Coccidiosis

Etiology

• •Coccidia are host-specific protozoan parasites.
• •Twelve different species of intestinal Eimeria infect rabbits, with E. perforans being the most common. Pathogenicity varies according to species. E. magna is the most pathogenic species affecting the small intestine.
• •Hepatic coccidiosis results from infection with the highly pathogenic Eimeria stieda.
• •Infection results from the ingestion of sporulated oocysts.
• •Coccidiosis is primarily a disease of young and weanling rabbits. Natural immunity develops against each Eimeria species after exposure. No cross protection in immunity exists between different Eimeria species. Adult animals can become ill if exposed to a species against which they have no immunity.
• •The severity of disease is determined by the age at time of exposure, the species of Eimeria involved, the number of oocysts ingested, and environmental stress factors.

Clinical Signs

• •Intestinal coccidiosis is often subclinical or causes only intermittent mild-to-moderate diarrhea and associated dehydration. However, coccidia may predispose the rabbit to bacterial enteritis (see “Diarrhea/Enteritis”). Clinical signs are usually most apparent in young rabbits.
• •Severe diarrhea, intussusception, and death may occur with heavy infections. Blood and mucous may also be associated with the diarrhea.
• •Hepatic coccidiosis is associated with anorexia, weight loss, abdominal enlargement, diarrhea, icterus, and acute death.

Diagnosis

• •Presumptive diagnosis is based on identifying Eimeria oocysts in a fecal sample or intestinal scrapings. The presence of organisms on histologic examination is required for definitive diagnosis.

Treatment and Prevention

• •The age of the host and the severity of clinical signs are factors to consider in treatment. Animals with light parasite burdens usually develop immunity to the organism and recover without therapy.
• •Therapy with coccidiostats is more prophylactic than therapeutic. Coccidia are susceptible to treatment only during a specific period in the protozoan life cycle. Clinical signs are usually inapparent during this period.
• •Coccidiostats may slow multiplication until host immunity develops.
• •Trimethoprim/sulfamethoxazole (30 mg/kg PO q12h for 10 days) has proved effective for the prevention and treatment of coccidiosis.
• •Sanitation is of utmost importance for effective therapy and prevention. Routinely disinfect cages, food bowls, and water bottles.
• •Screen rabbits for shedding of coccidial oocysts. Separate or cull carriers from colonies.
• •Check all young rabbits for coccidia.

Gastrointestinal Stasis

Etiology

• •Dietary factors

Key Point.

Lack of roughage in the diet is a major predisposing factor in GI stasis.

• •Stress is a major factor in GI stasis. Stress-related hormonal release may have a direct effect on intestinal motility and digestion, allowing overgrowth of pathogenic organisms.
• •Hairballs slow GI motility, prolonging retention of fermentable food.

Clinical Signs

• •No fecal pellet production in over 24 hours. Patients are also often anorectic.
• •Some rabbits have painful abdomens and may stay in a hunched position. The stomach or cecum may be distended with intestinal gas that may be detected on abdominal palpation.

Diagnosis

• •Dietary history is very important. Determine the fiber content of the normal feed and the amount of supplemental roughage.
• •Results of serum biochemical analysis often reveal electrolyte and metabolic abnormalities.

Treatment

• •Fluid therapy is critical in the treatment of rabbits with GI stasis. Stable patients can be administered fluids subcutaneously once to twice a day. Critical patients require IV catheterization.
• •Correct the diet in animals on marginal or deficient dietary fiber levels.
• •Broad-spectrum antibiotics, such as the fluorinated quinolones, trimethoprim/sulfa, or chloramphenicol are indicated if bacterial enteritis is suspected. Oral administration is effective in animals with mild-to-moderate diarrhea. Give antibiotics parenterally in rabbits with severe clinical signs. Avoid antibiotics that may induce enteritis.
• •Force-feed anorectic animals with Critical Care for Herbivores (Oxbow Pet Products) or softened rabbit pellets mixed with vegetable baby food or canned pumpkin.

Prevention

• •Instruct owners to feed their rabbits proper diets with an adequate content of indigestible fiber.
• •Minimize stress in young or weanling rabbits. Sudden temperature changes, changes in food, overcrowding, or poor sanitation contribute to disease.

Malocclusion

Etiology

Key Point.

Malocclusion is one of the most common causes of anorexia in rabbits.

Clinical Signs

• •Rabbits with malocclusion often have no other clinical signs. Owners may report that the rabbit shows interest in food, but stops eating after a few bites. Most remain alert and active.
• •Excessive salivation is common in rabbits with malocclusion.

Diagnosis

• •Perform a thorough oral examination in all anorectic rabbits. Examine the back molars with an otoscope or nasal/vaginal speculum. Sedation may be necessary in some especially nervous or active rabbits.

Treatment

• •Incisors can be cut with a diagonal cutter or, preferably, a dental drill. Both pairs of upper incisors should be clipped.

Key Point.

Do not use Resco-type nail clippers to cut incisors because excessive trauma can result in split incisors and loosened tooth roots.

• •Molar malocclusion requires dentistry with sedation. The procedure is usually short and can be done with an injectable tranquilizer. A combination of medetomidine (0.15-0.35 mg/kg SC, IM) and ketamine (5-10 mg/kg SC, IM) works well and can be reversed when the procedure is finished. Gas anesthesia can be used by holding the anesthetic mask over the rabbit's nostrils, leaving the oral cavity free for working in the mouth.

Technique—Teeth Triming

• 1.Place the rabbit in sternal recumbency with an assistant extending the neck and head forward.
• 2.The mouth can be held open by looping strips of gauze around both upper and lower incisors. The assistant holds the gauze around the lower molars in one hand, while the second hand is placed on top of the rabbit's head and holds the gauze looped around the top incisors, forcing the head and neck into extension. Make sure the nostrils are not occluded and the neck is extended or the rabbit will have difficulty breathing. Alternatively, a metal speculum made for rabbit dentistry can be used to hold the mouth open; however, this tool can damage the oral mucosa if used inappropriately.
• 3.Use a short vaginal or nasal speculum with an attached light source to examine the oral cavity. Check both lateral and medial edges of upper and lower molars.
• 4.A dental drill rounds and smoothes sharp edges but must be used with care. Use a tongue depressor or the speculum to isolate the arcade and prevent damage to the tongue or buccal mucosa. Burr guards can also be purchased. Long-shank burrs made specifically for use in the long, narrow oral cavity of rabbits are available.
• 5.A small bone rongeur can be used to clip the sharp edges of the cheek teeth. Use a tongue depressor or speculum to push the tongue to one side while clipping the medial edges of the lower cheek teeth. This method is quick and easy but leaves rough edges and may cause fractures of the teeth.
• •Root elongation of the premolars and molars can develop in rabbits with chronic malocclusion. Elongated roots of the mandibular teeth can be palpated as firm bony nodules on the ventral mandible. Roots of the maxillary teeth can invade the nasal passages, sometimes causing obstruction and resulting in inspiratory stridor. The roots often become infected, resulting in mandibular, maxillary, or retrobulbar abscesses (see “Mandibular and Joint Abscesses”).

Prevention

• •Most rabbits with incisor malocclusion need their incisors clipped every 4 to 8 weeks.
• •Check rabbits with molar malocclusion every 2 to 3 months. Dentistry may be needed as often as every month or only once yearly.
• •Rabbits with malocclusion should not be bred.
• •Instruct owners to feed a high-roughage diet to encourage normal wear of the teeth.

Hairballs (Trichobezoars)

Etiology

Key Point.

Inadequate dietary roughage is associated with gastric hairballs in rabbits.

• •Other factors may contribute to formation of hairballs. Long-haired breeds may consume large amounts of hair while grooming during shedding. Hormonal influences in breeding season may contribute to aggression and fur-barbering. Mineral deficiencies may cause pica of hair. Boredom also may be a factor in fur-barbering.
• •Rabbits are unable to vomit, contributing to accumulation of hair in the stomach.

Clinical Signs

• •Anorexia is the primary clinical sign associated with trichobezoars. Often rabbits remain alert and active, with no other signs.
• •Weight loss, depression, and palpable intestinal gas may be present in some rabbits. Fecal pellets may appear small, the amount of pellets passed may be less than normal, and hair may be visible in the pellets, causing them to “string” together.
• •Diarrhea may develop in some animals because of changes in the cecal microflora from decreased gastric motility (see “Diarrhea/Enteritis”).
• •Acute pyloric obstruction causes severe depression, lethargy, bloating, dehydration, hypothermia, and shock.

Diagnosis

Key Point.

Suspect a trichobezoar in an anorectic but otherwise alert rabbit with a history of inadequate dietary fiber and excessive shedding.

• •A soft mass palpable in the stomach area of an anorectic rabbit is evidence of a hairball. The stomach of a healthy rabbit is normally full. However, a rabbit that has been anorectic for several days should have an empty stomach.
• •Radiographs are used to confirm a diagnosis. An enlarged stomach may be visible on plain radiographs. Contrast radiography of the upper GI tract may outline the hairball. Give barium at a standard small-animal dose of 10 to 14 ml/kg orally into the cheek pouch.
• •Ultrasound examination can be used to detect a mass in the stomach area.
• •A CBC and serum biochemical analysis are indicated in dehydrated, severely ill, or debilitated animals.

Treatment

Key Point.

Providing adequate dietary roughage and making sure that the rabbit is hydrated are extremely important for successful treatment of rabbits with trichobezoars.

• •Medical management is successful in most rabbits. Although a few clinicians advocate routine surgical removal of hairballs, the risk of surgical or anesthetic complications is high considering the debilitated condition of most of these rabbits.
• •Give supplemental fluids (approximately 100–150 ml/kg/day) subcutaneously or, preferably, by intravenous catheter in debilitated animals.
• •Stimulate GI motility by encouraging the animal to move around. Allow the rabbit out of the cage as much as possible to exercise. Administer GI motility stimulants if no intestinal blockage is suspected and gut motility is poor.
• •Give the rabbit petrolatum-based oral lubricants such as Laxatone at 1 to 2 ml/day for 3 to 5 days to aid in fur passage.
• •Offer free-choice hay and fresh vegetables at all times. Force-feed anorexic patients with products such as Critical Care for Herbivores (Oxbow Pet Products) several times a day.
• •Pain medication such as buprenorphine (0.01–0.05 mg/kg SC, IM q6-12h) or flunixin meglumine (1.1 mg/kg SC, IM q12h for no more than 3 days) may be indicated in patients with abdominal pain and distention.
• •Although rare, rabbits with acute pyloric obstruction must be treated surgically. Even with surgery, the mortality rate in rabbits with pyloric obstruction is high.

Prevention

Key Point.

Correct the diet to include adequate dietary fiber (see Diet). Provide free-choice timothy hay and fibrous vegetables. Feed rabbit pellets that have a high-fiber content (>20%).

• •Routinely brush long-haired rabbits or heavy shedders.
• •Some owners administer a petrolatum-based cat laxative to their rabbits every 1 to 2 months.
• • Encourage rabbits to exercise. Prevent obesity by restricting the amount of pellets fed and not feeding sweet “treats”.

UROGENITAL/REPRODUCTIVE DISEASES

Uterine Adenocarcinoma/Hyperplasia

Etiology

Key Point.

Uterine adenocarcinoma is the most common tumor in domestic rabbits.

• •Adenocarcinoma rarely occurs in does younger than 4 years of age. The incidence in rabbits older than 4 years of age ranges from 50% to 80% in certain breeds such as the Dutch, French Silver, and Havana, suggesting a genetic component to the disease. Occurrence is independent of breeding status.
• •Endometrial changes such as atrophy of the glandular epithelial cells and increased collagen content are associated with development of uterine neoplasia.
• •Endometrial changes that may precede neoplastic changes include endometriosis, endometritis, and papillary, cystic, or adenomatous hyperplasia.
• •Local metastasis can extend through the uterine myometrium and invade adjacent structures in the peritoneum such as lymph nodes. Hematogenous spread to the liver, lungs, and brain occurs late in the clinical course, after 10 to 12 months.

Clinical Signs

Uterine adenocarcinoma is a slow-growing tumor that can be multicentric and involve both horns of the uterus.

• •Clinical signs are usually inapparent during the early hyperplastic stages.
• •Hematuria or a serosanguineous vaginal discharge is often the first clinical sign noted.
• •Decreased reproductive performance such as small litter size, stillbirths, dystocia, litter desertion, and infertility are seen in breeding does.
• •Cystic mastitis is associated with uterine changes in many does.
• •Depression, anorexia, dyspnea, and ascites are often noted in late-stage cases, especially if metastasis to the lungs has occurred.

Diagnosis

• •An enlarged, thickened uterus or multiple rounded caudal abdominal masses may be palpable on physical examination. A mass may be difficult to differentiate from abdominal fat in small does.
• •An enlarged uterus may be visible on abdominal radiographs. Thoracic radiographs should be taken to screen for pulmonary metastasis.
• •Abdominal ultrasonography also can be used to identify an enlarged uterus or uterine masses and to detect liver or lymph node metastases.

Treatment

• •Ovariohysterectomy is successful if done before metastasis has occurred.
• •Surgical resection of early focal abdominal metastasis is the treatment of choice but carries a guarded prognosis because of metastasis that may not be visible at the time of surgery.
• •Prognosis is poor after pulmonary metastasis has occurred. Euthanasia is recommended.

Prevention

• •Routine ovariohysterectomy of does before 2 years of age is recommended.
• •Educate owners with intact does about the early clinical signs of uterine adenocarcinoma and recommend yearly to semi-annual check-ups once the patient is 3 years of age.
• •Consider ovariohysterectomy in does older than 3 years of age with evidence of cystic mastitis or increased aggressive behavior.

Mastitis

Etiology

Mastitis in rabbits can be either septic or nonseptic.

• •Septic mastitis is most common in lactating does. Trauma from abrasive bedding or caging, heavy lactation, and poor sanitation predispose the mammary gland to infection.
• •Staphylococcus aureus and Pasteurella and Streptococcus spp. are the most commonly isolated bacteria. E. coli and Pseudomonas, Pasteurella, and Klebsiella spp. also may cause mastitis.
• •Nonseptic, cystic mastitis is seen in both breeding and non-breeding females older than 4 years of age. It may be associated with high estrogen levels, uterine hyperplasia, and uterine adenocarcinoma. In some cases, malignant cellular changes may occur and develop into mammary adenocarcinoma.

Clinical Signs

• •With septic mastitis, the affected gland is swollen, firm, erythematous to blue-tinged, and warm to the touch. Infection spreads until all glands are affected.
• •Abcesses of the mammary gland can develop independent of lactation status.
• •Systemic signs of septic mastitis include pyrexia, depression, anorexia, death of neonates, or death of the doe.
• •With cystic mastitis, glands became swollen, firm, and blue-tinged with a clear-to-dark serosanguineous discharge from the teats. Rabbits are not systemically ill.

Diagnosis

• •Diagnosis of septic mastitis is based on clinical signs, history of lactation or pseudocyesis, and isolation of bacteria on culture of gland tissue or exudate.
• •Cystic mastitis must be differentiated from septic mastitis and mammary neoplasia. Culture and sensitivity testing of the discharge is negative for bacterial growth. Fine-needle aspiration and cytology is indicated to identify any neoplastic tissue.

Treatment

• •Administer antibiotics for septic mastitis. Base therapy on results of culture and sensitivity testing.
• •Pain medication such as buprenorphine is indicated if the rabbit appears to be in pain. Warm compresses 2 to 3 times daily may be helpful. Consider surgical drainage or excision of mammary abscesses.
• •Suckling kits need to be removed from the doe as they may become infected with the bacteria and die from septicemia.
• •Cystic mastitis usually resolves within 3 to 4 weeks after ovariohysterectomy. Severely affected glands may require surgical excision.

Prevention

• •Keep lactating does in a clean environment. Make sure no sharp surfaces or wire edges are present that can traumatize the teats.
• •Routinely examine lactating does for evidence of inflammation or teat injuries.
• •Cystic mastitis can be prevented by routine ovariohysterectomy of young, healthy does.

Dysuria/Hematuria

Etiology

• •Red, pink, or orange discoloration of the urine occurs periodically in healthy rabbits. The color may be the result of porphyrin pigments or food-related metabolites excreted in the urine.
• •Thick, creamy to sandy, white urine indicates the presence of excess calcium in the urine. Unlike most mammals, intestinal absorption of calcium does not depend on vitamin D. Increases in dietary calcium intake results in large amounts of calcium being excreted in the urine.
• •Hematuria occurs commonly with cystitis. Frank blood independent of or at the end of urination may indicate uterine adenocarcinoma.
• •Cystic calculi occur in both male and female rabbits. Calculi usually are composed of calcium carbonate or calcium oxalate and may be associated with high dietary calcium intake.

Clinical Signs

• •Rabbits with urinary pigment changes or excessive calcium in the urine usually have no other clinical signs.
• •Dysuria, stranguria, urine scald, lethargy, anorexia, and depression may be seen in rabbits with cystitis or cystic calculi. Rabbits may also exhibit teeth grinding or stay in a hunched position in response to abdominal pain.

Diagnosis

• •Differentiate hematuria from pigment changes in the urine by simple dipstick analysis for blood. If urine discoloration is intermittent, dispense dipsticks for owners to check the urine at home.
• •Submit a urine sample for urinalysis in rabbits with clinical signs of cystitis, cystic calculi, or hematuria. Calcium oxalate crystals are commonly present, though ammonium phosphate, calcium carbonate, and monohydrate crystals are also often seen. If bacteria are identified, a urine sample collected by cytocentesis should be submitted for culture and sensitivity testing.
• •A serum biochemical analysis and a CBC are necessary to assess renal function.
• •Distinguish between hematuria and hemorrhagic vaginal discharge occurring secondary to uterine adenocarcinoma by physical examination, history, urinalysis, abdominal radiographs, and abdominal ultrasonography. Uterine adenocarcinoma is likely in a doe older than 3 years of age with a thickened uterus or multiple abdominal masses.
• •Obtain abdominal radiographs if cystic calculi are suspected. Calculi are usually radiopaque and therefore visible in the bladder or urethra. Calculi may also be visible in the ureters or kidneys. Large amounts of calcium sediment may be visible in the bladder in rabbits excreting large amounts of calcium.

Treatment

Treatment is not necessary in rabbits with pigment-based changes in urine color.

• •Instruct owners to decrease the dietary calcium levels in rabbits with hypercalciuria. Grass hay (e.g., timothy) has a lower calcium content than legume hay (e.g., alfalfa). Feed grass hay, green leafy vegetables, and timothy-based pellets.
• •Treat rabbits with simple bacterial cystitis with antibiotics. A 3-week course of chloramphenicol or trimethoprim/sulfa is usually effective. Submit a second urine sample for bacterial culture and sensitivity testing after 4 to 6 weeks.
• • Cystic calculi must be removed surgically. Submit calculi for stone analysis. Decrease dietary calcium after surgery to help prevent recurrence.

Prevention

• •For prevention, decrease dietary calcium levels, especially in mature or aged rabbits.
• •Many pelleted diets are derived from alfalfa and exceed dietary calcium requirements. Change to timothy-based pellets and substitute grass or timothy hay for alfalfa hay in the diet. Discontinue any supplemental vitamins.
• •Overweight rabbits are predisposed to hypercalciuria and urolithiasis. Decrease or eliminate pellets from the diet and encourage rabbits to exercise to prevent obesity.

Treponematosis

Etiology

• •Treponema paraluiscuniculi is the causative agent of rabbit syphilis.
• •T. paraluiscuniculi is a spiral-shaped bacterium transmitted by direct and venereal contact between breeding rabbits or from doe to offspring. It is not a zoonotic disease.

Clinical Signs

• •Most lesions develop on the external genitalia and perineum. Infection of the nose, eyelids, lips, and chin may result from autoinfection. Lesions initially consist of erythematous vesicles that progress to papules, ulcerations, scaliness, and dry crusty lesions.
• •Nasal lesions in pet rabbits are commonly mistaken for dermatophyte lesions.
• •Rabbits remain alert, responsive, and active.
• •The incidence of abortions, metritis, and infertility may increase in breeding females.

Diagnosis

• •Diagnosis is based on history, clinical signs, distribution of lesions, and response to therapy.
• •Submit fur samples for fungal culture and do skin scrapings to rule out dermatophytes and ectoparasites.
• •Treponema organisms can be identified by darkfield microscopic examination of skin scrapings. The organisms also can be demonstrated histologically with silver stains of skin biopsy sections.
• •Serologic tests such as the rapid serum regain (RPR) are available commercially to determine the presence of antibodies against T. cuniculi. A fluorescent antibody test against treponemal antigen also is used, and an ELISA is available to screen for antibodies. These tests are used for screening in rabbit-breeding colonies.

Treatment

• •T. paraluiscuniculi is susceptible to penicillin. Give injections of benzathine penicillin G (a long-acting penicillin) at 42,000 to 84,000 IU/kg IM at weekly intervals for 2 to 3 weeks. Response is rapid; lesions dramatically regress, usually after one injection.
• •Tetracyclines and chloramphencol have also been effective against T. cuniculi.

Prevention

• •Screen rabbits in breeding colonies for treponematosis.
• •The incidence of disease in pet rabbits is low. Preventive serologic screening is not necessary.

NEUROMUSCULAR/SKELETAL DISEASES

Mandibular and Joint Abscesses

Etiology

• •Abscesses of the mandible and joints occur frequently in pet rabbits. Bacteria such as Pasteurella multocida, Staphyloccoccus aureus, Pseudomonas aeruginosa, Fusobacterium nucleatum, Peptostreptococcus micros, Strepcococcus milleri group, Actinomyces israelii, Arcanobacterium haemolyticum, Prevotella spp., Proteus spp., and Bacteroides spp. have been isolated. Bacteria can also spread hematogenously from the initial infection.
• •Malocclusion and root elongation of the cheek teeth sometimes accompany mandibular abscesses. Infection may spread from the oral cavity along the tooth root.
• •Soft-tissue abscesses can also occur in the oral cavity or joints secondary to a penetrating wound from a foreign body.

Clinical Signs

• •Joint abscesses are most frequent in the distal limb joints. The swellings are large, firm, and warm to the touch. Rabbits may be lame, depending on which joints are involved.
• •Mandibular abscesses occur as firm swellings in the ventral facial area. Abscesses are sometimes quite large before they are apparent to the owner. Excessive ptyalism may be an early symptom.
• •Affected rabbits may refuse to eat if mandibular abscesses are accompanied by dental disease.
• •Many rabbits remain active and alert with no other clinical signs.

Diagnosis

• •Thick, white purulent exudate is present on fine-needle aspirate of the swelling. Cytologic examination of the exudate shows neutrophils and proteinaceous debris; bacteria may or may not be visible.
• •Obtain radiographs to check for and evaluate the extent of any bone involvement.
• •Submit tissue samples for bacterial culture and sensitivity testing. Because the necrotic centers are often sterile, collect samples from the inside of the abscess capsule wall.

Treatment

Key Point.

Simple lancing of mandibular and joint abscesses is ineffective because of the thick, caseous nature of the exudate.

• •Complete enbloc surgical excision of the abscess is the preferred treatment. However, depending on the extent of involvement, this may not be possible and aggressive surgical debridement is the next best option. Remove any molars or premolars that are loose or that have radiographic evidence of extensive infection of the roots. Flush the soft tissue with copious amounts of sterile saline.
• •Abscesses often re-occur and multiple surgeries concomitant with antibiotic therapy may be required for resolution.
• •Antibiotic-impregnated polymethylmethacrylate (AIPMMA) beads can improve the success rate of surgical treatment of mandibular abscesses if abscessed tissue cannot by completely excised.
• •Amputating the affected limb may be the most effective therapy for abscesses involving the joint and surrounding bone. Rabbits adapt well to amputation of either a fore or rear limb.
• •Disease may recur in other joints, even if amputation of the affected limb has been performed. Hematogenous spread of the bacterial infection to other joints may occur at any time during the clinical course.
• •Long-term antibiotic therapy is necessary. Some rabbits respond to oral fluoroquinolone or injectable penicillin therapy in combination with surgical debridement or amputation.
• •Owners must be able to do extensive nursing care at home. Have the owners flush open wounds with sterile saline once or twice daily.
• •The prognosis for successful therapy is guarded. With bony involvement, the prognosis is poor.

Torticollis/Head Tilt/Ataxia

Etiology

• •Bacterial infection of the inner ear, middle ear, or meninges is the most common cause of torticollis in pet rabbits. Pasteurella multocida is often implicated as a primary cause, though other bacteria may also be involved.
• •Encephalitozoon cuniculi is another common cause of torticollis and incoordination in rabbits.
• •Vascular lesions, infection with herpesvirus, cerebral nematodiasis, hypovitaminosis A, and toxicoses (e.g., lead poisoning) are less common causes of head tilt and uncoordination.

Clinical Signs

• •Onset may be acute or slowly progressive. The head tilt may be mild or accompanied by torticollis, incoordination, and the inability to stand.
• •Some rabbits have no other clinical signs. Other rabbits become depressed, anorexic, and lethargic.
• •Rabbits with severe depression, positional nystagmus, and facial nerve deficits may have brain or meningeal lesions.

Diagnosis

Diagnosis is based on clinical signs. Establishing the exact cause may be difficult.

• •Carefully examine both ear canals for evidence of infection.
• •Rabbits with severe otitis media may have swellings at the base of the ear. White, creamy, caseous debris can often be massaged out of the ear canal. Cultures and sensitivity testing can be helpful in identifying organisms and in directing antibiotic therapy.
• •Results of a CBC may reveal an inflammatory response.
• •Skull radiographs may aid in diagnosis. Anesthesia is usually necessary for proper positioning. Bony changes in the bulla may indicate osteomyelitis.
• •Serologic tests can be used to detect antibodies against E. cuniculi or P. multocida. A positive result is not diagnostic of the specific agent but is helpful in ruling out some possible causes.
• •Often, the cause cannot be established, and a tentative diagnosis is based on response to therapy. Rabbits with pasteurellosis often improve with long-term antibiotic therapy and supportive care. Rabbits with parasitic migration may remain unchanged or improve gradually. Rabbits with clinical signs secondary to encephalitozoonosis are usually unresponsive to treatment or they deteriorate clinically.
• •The cause sometimes is determined only on postmortem examination.

Treatment

• •Give antibiotics long-term, usually a minimum of 4 to 6 weeks. Choose an antibiotic that penetrates the blood-brain barrier and is effective against pasteurellosis (e.g., chloramphenicol and enrofloxacin).
• •If exudate is visible in the ear canal, clean and flush the ear thoroughly. Tranquilization or anesthesia may be necessary. Administer a topical antibiotic in the ear canal 3 to 4 times daily. Administer systemic antibiotics based on culture and sensitivity testing.
• • Administer an oral Lactobacillus supplement during long-term antibiotic therapy.
• •Supportive care is necessary in rabbits that are laterally recumbent or that have severe torticollis. Recumbent rabbits should be turned every 6 to 8 hours or propped up sternally to prevent hypostatic congestion of the lungs. Apply eye lubricants several times daily if the blink reflex is diminished. Hand-feeding may be required. Keep rabbits on clean, dry bedding to prevent urine scalding and contact dermatitis.
• •Inform owners about the amount of supportive care needed in recumbent rabbits. Many owners elect euthanasia when faced with the difficulties and the time required for long-term nursing care.
• •Euthanasia often is selected in debilitated rabbits if no clinical improvement is seen after several days of therapy.

Encephalitozoonosis (Encephalitozoan cunuculi)

Etiology

• • E. cuniculi is an obligate, intracellular, microsporidian parasite prevalent in domestic and wild rabbits. The organism infects mice, rats, hamsters, and guinea pigs less commonly.
• •The major route of transmission is by ingestion of spore-contaminated urine. Inhalation and vertical transmission can also occur. E. cuniculi spores are environmentally resistant and can survive for 4 weeks in mild environmental conditions.
• •The organism can infect lungs, kidneys, liver, heart, brain, and eye. Many infected rabbits are asymptomatic, or may develop clinical signs after a stressful event or other immunosuppressive conditions.

Clinical Signs

• •Depending on the site of infection, clinical signs can vary and include: torticollis, ataxia, nystagmus, rolling, seizures, paresis, and death. Clinical signs of encephalitozoonosis are similar to those of the neurologic form of pasteurellosis.

Diagnosis

• •Presumptive diagnosis is based on clinical signs and results of diagnostic testing of rabbits exhibiting neurologic signs.
• •Serologic tests are available to detect the presence of antibodies against E. cuniculi. These include ELISAs and indirect fluorescent antibody assays.
• •Definitive diagnosis requires histopathologic examination of affected tissues. Spores can be seen in the tissue and lesions in the brain usually consist of multifocal areas of necrosis and granulomas with perivascular lymphoplasmacytic cuffing.

Treatment

• •Several treatment protocols have been reported; however, results have been variable. Administer fenbendazole (20 mg/kg q24h for 28 days), oxibendazole (30 mg/kg PO q24h for 7-14 days, then reduced to 15 mg/kg q24h for 30-60 days), or albendazole (30 mg/kg PO q24h for 30 days, then 15 mg/kg PO q24h for 30 days or 10-15 mg/kg PO q24h for 3 months).
• •Clinical signs may recur in some rabbits when drugs are stopped. These rabbits may require medications indefinitely to control clinical signs.
• •For rabbits with suspected concurrent bacterial infection, antibiotic therapy with chloramphenicol (30–50 mg/kg PO q12h for 7 days) can be administered while awaiting the results of serologic testing.
• •Patients with severe neurologic signs are often anorectic and will require supportive care such as fluids and force feeding until clinical signs abate.

Prevention

• •Identify carriers in rabbit colonies and breeding facilities through serologic testing. Cull animals that test positive.
• •Eliminate urine contamination between cages through proper sanitation procedures. Most disinfectants, such as quaternary ammonium compounds, iodophors, phenolic derivatives, alcohols, and hydrogen peroxide, are effective in inactivating spores.
• •Prevent possible contact between pet rabbits housed outdoors and wild rabbits or rodents by elevating cages off the ground or housing pets in a rodent-proof enclosure.

Vertebral Fractures/Luxation

Etiology

• •The rear leg muscles of rabbits are well developed for strong kicking and thumping.

Key Point.

If rabbits are restrained poorly with inadequate control of the rear legs, animals may kick suddenly, resulting in fracture of their spinal vertebrae.

• •The lumbosacral region (L7) is the most common site for fracture or luxation.

Clinical Signs

• •Clinical signs of a fractured back depend on the degree of spinal cord damage and can include partial or complete paralysis of the rear legs and loss of normal bladder and bowel function.
• •Signs are acute in onset and directly related to a traumatic incident.
• • Other disease problems may cause clinical signs similar to a vertebral fracture. Multifocal infection of the spinal cord secondary to pasteurellosis, parasite migration, or vascular thrombosis within the cord can cause neurologic deficits. The clinical onset is usually more chronic and slowly progressive than that of a fracture.

Diagnosis

• •Diagnosis is based on history and clinical signs.
• •Obtain radiographs of the vertebral column to confirm a fracture or luxation.

Treatment

• •If a diagnosis is made within 6 to 12 hours of the time of the fracture, administer methylprednisolone sodium succinate, prednisolone sodium succinate, or dexamethasone at shock dosages.
• •Conservative medical management such as cage rest and nonsteroidal anti-inflammatory agents can be used to manage mild cases. Anti-inflammatory and pain medication such as Carprofen (Rimadyl, Pfizer Animal Health, Exton, PA) or Meloxican (Metacam, Boehringer, Ingelheim Vetmedica, St. Joseph, MO) are often effective in making the patient more comfortable. Attempts to stabilize the fracture surgically are usually not practical because of the poor prognosis and degree of nursing care necessary.
• •Some owners try long-term supportive care to see whether neurologic function returns. They must be instructed on manual expression of the bladder and general nursing care. The rabbit's bedding should be changed multiple times a day to prevent urine scald. The patient will also need to be placed on alternating sides frequently prevent formation of pressure sores.
• •Prognosis for recovery is guarded to poor. Euthanasia usually is recommended in rabbits with complete transaction of the cord resulting in complete rear limb paralysis and urinary and fecal incontinence.

Prevention

• •See Figure 176-1, Figure 176-2 for proper restraint of rabbits.

Bone Fractures/Joint Luxations

Etiology

• •The skeleton of the rabbit is light and fragile. The tibia, radius, and ulna fracture easily with traumatic events such as getting a limb caught in wire caging or accidentally being dropped or stepped on.
• •Traumatic joint luxations of the elbow or stifle joint occasionally occur.

Clinical Signs

• •Rabbits with bone fractures or luxations are acutely lame.
• •Rabbits have minimal soft tissue to protect the long bones below the elbow and stifle from penetrating the skin, thus open fractures are common at these sites.
• •Fractures are usually palpable on physical examination. Joint luxations are palpable as firm swellings.

Diagnosis

• •Diagnosis is based on history, clinical signs, and physical examination.
• •Obtain radiographs to evaluate fractures for surgical repair or to confirm joint luxations.

Treatment

• • Splints used in combination with padded bandages are usually adequate to stabilize metatarsal, meta-carpal, and phalangeal fractures. Bandage the foot in a functional position. Contour a moldable splint or casting material such as Orthoplast (Johnson & Johnson, New Brunswick, NJ) or Vet-lite (Runlite SA, Micheroux, Belgium; see www.runlite.com for distributors) along the plantar surface.
• •External coaptation can also be effective for closed, simple, long-bone fractures. Maintain the limb in a normal position and incorporate both the joints above and below the fracture into the splint. Ideally, there should be at least 50% cortical contact between the fragment ends.
• • Intramedullary pins can be used for better axial alignment of long bone fractures and to minimize bending and rotational forces. The pins should occupy at least 60% to 70% of the medullary cavity. Cross-pins can be used for supracondylar humeral or femoral fractures. Bone plates are not usually recommended other than in large rabbits because the thin cortices of rabbit bones makes screw placement difficult.
• • External skeletal fixation provides rigid stability with minimal soft tissue disruption. Because fixator pin diameter should not exceed 20% of the bone diameter, Kirschner wires are often used in smaller patients. Most metal bars and clamps are too large or heavy for rabbits; therefore, bone cement or acrylics injected into appropriately sized rubber tubing are effective as fixator bars. (see Chapter 111 for examples of external skeletal fixators)
• •Severely comminuted or open fractures may be best managed with limb amputation. Rabbits usually adapt well to amputation and can ambulate easily on three limbs. Forelimb amputation is best performed by removing the scapula. Mid-femoral amputation of the hind limb is preferred over coxofemoral disarticulation.
• •With a joint luxation, anesthesia is needed to manipulate the joint into normal position. With the joint reduced and the limb in extension, apply a splint to allow the surrounding soft tissue to develop fibrosis and keep the luxation reduced. Some luxations may additionally require a transarticular pin to stabilize the joint.

  See Section 8 for treatment of orthopedic disorders in dogs and cats.

Postoperative Care

• •Obtain a radiograph of the leg after repair to assess bone alignment and placement of pins (if used).
• •Postoperative management vital for successful healing includes strict cage rest, a clean environment, a good diet, and frequent monitoring any bandages or fixators.
• •Antibiotics are indicated in all open and contaminated fractures to prevent subsequent osteomyelitis and abscess formation.