Table 1-1.

Parasitic, Bacterial, and Viral Causes of Diarrhea in Kittens

Disease	Clinical Signs	Diagnostic Test(s)	Infectious Agent	Comments	Treatment
Parasitic Causes of Diarrhea in Kittens
Trichomoniasis	Large bowel diarrhea Subclinical infection is common	1.Direct fecal smear 2.InPouch fecal culture 3.Fecal PCR	Tritrichomonas blagburni trophozoites identified on fecal smear and culture DNA detected via PCR	Fecal PCR testing is the most sensitive method. Fecal InPouch culture can take up to 10 days to yield a positive result	Ronidazole 30 mg/kg PO every 24 h for 14 days. Isolate infected cats. Retest.
Cryptosporidiosis	Subclinical infection is common Small bowel or mixed-bowel diarrhea	1.Acid-fast stain on fecal cytology 2.DFA testing 3.Fecal PCR	Cryptosporidium felis oocysts	More common in kittens and immunocompromised cats. Infection can be self-limiting.	Treatment can be challenging. No drug is FDA approved. Azithromycin (7-10 mg/kg PO every 12 h for 10 days) is recommended.
Giardiasis	Small bowel diarrhea Subclinical infection is common	1.Direct fecal smear 2.Fecal flotation (centrifugation) 3.Fecal ELISA 4.Fecal DFA 5.Fecal PCR (recommended for determination of Giardia assemblages if warranted)	Giardia intestinalis (has 8 assemblages [A-H] that determine its zoonotic potential) Flotation and DFA detect cysts via microscopy and ELISA detects soluble antigen	Fecal flotation combined with fecal ELISA has a combined sensitivity of > 97% PCR testing has a lower sensitivity than ELISA and flotation ELISA testing should be used for baseline screening only	None of the treatments are FDA approved. Metronidazole 25 mg/kg PO every 12 h for 7 days or Fenbendazole 50 mg/kg PO every 24 h for 5 days. Environmental control is important.
Coccidiosis	Subclinical infection is common Large bowel to mixed-bowel diarrhea	Fecal flotation (centrifugation)	Cystoisospora felis oocysts Cystoisospora rivolta oocysts	Coccidiosis is typically a disease of kittens, and diarrhea can be self-limiting.	Sulfadimethoxine is approved but is coccidiostatic, label dose is 55 mg/kg PO initial dose followed by 27.5 mg/kg every 24 h for up to 14 days. Ponazuril 50 mg/kg PO every 24 h for 4 days. Environmental control.
Whipworms	Large bowel diarrhea	Fecal flotation (centrifugation)	Trichuris serrata	Rare in domestic cats.	Fenbendazole 50 mg/kg PO every 24 h for 5 days (not FDA approved).
Roundworms	Small bowel diarrhea, failure to thrive, “pot-bellied” appearance	Fecal flotation (centrifugation)	Toxocara cati Tocascaris leonina	Common in kittens < 6 months old.	Pyrantel pamoate 20 mg/kg PO beginning at 2 wks of age, or Fenbendazole 50 mg/kg PO every 24 h for 5 days.
Hookworms	Small bowel diarrhea, melena, iron-deficiency anemia, failure to thrive	Fecal flotation (centrifugation)	Ancylostoma tubaeforme, Ancylostoma braziliense, Uncinaria stenocephala Ancylostoma caninum	Relatively uncommon in cats.	Selamectin, moxidectin, milbemycin oxime, emodepside. Fenbendazole and pyrantel pamoate are not FDA approved but are used off-label.
Bacterial Causes of Diarrhea in Kittens
Clostridium perfringens	Subclinical infection is occasionally seen Diarrhea can be small bowel, large bowel, or mixed in nature	1.ELISA test for C. perfringens enterotoxin 2.Fecal PCR for enterotoxin gene (should not be used alone to make a diagnosis)	C. perfringens enterotoxin	The pathogenicity of C. perfringens is unclear in cats, and detection of the enterotoxin via ELISA in diarrheic kittens and cats is far less common compared with dogs. A stained fecal smear for detecting endospores is highly insensitive and is not recommended. Fecal culture alone is of no diagnostic utility.	Supportive treatment is sufficient in most cases. In cats with systemic illness, metronidazole (10 mg/kg PO every 12 h for 5-7 days), amoxicillin (22 mg/kg PO every 12 h for 5-7 days), or tylosin (10 mg/kg PO every 24 h for 5-7 days) is recommended.
Clostridium difficile	Subclinical infection is occasionally seen Diarrhea can be small bowel, large bowel, or mixed in nature	1.Fecal culture (negative culture rules out infection) 2.ELISA test for C. difficile toxins A&B	C. difficile toxins A&B	Detection of C. difficile toxins A&B in asymptomatic kittens is not uncommon.	Supportive treatment is sufficient in most cases. In cats with systemic illness, metronidazole (10 mg/kg PO every 12 h for 5-7 days) is the drug of choice.
Campylo-bacteriosis	Subclinical infection is commonly seen with nonpathogenic species C. jejuni can cause large bowel diarrhea	1.Fecal culture 2.Fecal PCR 3.Stained fecal smear is extremely unreliable and insensitive	Over 14 species described in dogs and cats C. jejuni is pathogenic and zoonotic	Most Campylobacter spp. are non-pathogenic. Prevalence rates of Campylobacter spp. are higher in non-diarrheic cats vs. diarrheic cats. PCR is helpful to differentiate Campylobacter species.	Avoid injudicious antimicrobial therapy. Supportive treatment and appropriate barrier control is optimal. Azithromycin (5-10 mg/kg PO every 24 h for 5-21 days) is warranted in immunocompromised cats or cats with systemic illness.
Salmonellosis	Subclinical infection is uncommonly seen Diarrhea is typically small bowel Other clinical signs include fever, lethargy, anorexia, vomiting	1.Fecal culture 2.Fecal PCR	Two main species, Salmonella enterica and Salmonella bongori, each of which contains multiple serotypes	Infection of cats with Salmonella has been associated with feeding of raw meats. Outbreaks of S. enterica serovar Typhimurium infection in cats have been associated with seasonal song bird migrations (“songbird fever”).	Avoid injudicious antimicrobial therapy. Supportive treatment and appropriate barrier control is optimal. Amoxicillin (22 mg/kg PO every 12 h for 7 days with enrofloxacin 5 mg/kg PO every 24 h for 7 days) is warranted in immunocompromised cats or cats with systemic illness.
Anaerobiospirillum infection	Large bowel diarrhea	1.Histopathology of colon with special stains	A. succuniciproducens	Infection is relatively rarely documented in cats.	Amoxicillin-clavulanic acid 15 mg/kg PO every 12 h for 14 days.
Gastric and intestinal Helicobacter infections	Subclinical infection is very common Clinical signs can range from vomiting to anorexia to diarrhea and lethargy depending on which species and organ system are involved	1.PCR of gastric biopsies (helpful for determination of species) 2.Serology (only determines exposure) 3.Cytology of impression smears or biopsies 4.Rapid urease testing of gastric biopsies 5.Culture is of low sensitivity	Over 15 species of Helicobacter described in dogs and cats	Majority of cats show no clinical signs.	Treatment is not routinely administered in infected cats. A 2-3 wk course of omeprazole with metronidazole and clarithromycin PO has been used with varying success in eradicating the infection.
Tyzzer's disease	Small and large bowel diarrhea, hepatic disease	1.PCR of affected intestinal or liver biopsies 2.Histopathology and special stains of intestine and liver	Clostridium piliforme	Infection can be rapidly fatal.	Amoxicillin 22 mg/kg PO every 12 h for 10 days.
Viral Causes of Diarrhea in Kittens
Feline Panleukopenia Virus	Fever, lethargy, inappetence, vomiting, diarrhea, sudden death Cerebellar signs can also occur	1.Canine parvovirus fecal antigen (ELISA) 2.Histopathology (usually necropsy) 3.PCR of feces, tissue samples 4.Fecal electron microscopy 5.Virus isolation (feces, tissues)	FPV, occasionally infection with related mink enteritis virus, CPV-2a, CPV-2b, or CPV-2c	Pathogenesis of FPV is similar to that of CPV infection. Subclinical infection is probably widespread. Marked variation in the sensitivity and specificity of fecal ELISA tests. Disinfection of the environment with bleach or potassium peroxymonosulfate is important.	Supportive care, IV crystalloids and parenteral antimicrobials (ampicillin and fluoroquniolone), antiemetics, dextrose, colloids, antacids (H2-blockers or proton pump inhibitors).
Feline Coronavirus	Enteric FCoV subclinical infection is common or may result in diarrhea If FIP develops, may see fever, lethargy, inappetence, vomiting, diarrhea, icterus, uveitis, neurologic signs, abdominal distension (effusion)	1.RT-PCR for detection of FCoV in feces (enteric FCoV) 2.Serology for detection of antibodies to FCoV indicates exposure only 3.For FIP, immunohistochemical staining for coronavirus antigen within lesions characterized by pygranulomatous or granulomatous vasculitis 4.Diagnosis also supported by analysis of abdominal effusion (high protein exudate that contains low numbers of nucleated cells [<5000 cells/µL] 5.RT-PCR for detection of FCoV in effusion or tissue samples	FCoV	FCoV is commonly detected in healthy and diarrheic cats with a prevalence ranging from 36-75%. Interpretation of positive FCoV serological or PCR-based tests must be made cautiously.	No cure exists for FIP. Prednisolone therapy with or without chlorambucil has been associated with prolongation of life span and improved quality of life. Several immunomodulators and antiviral drugs have been tried, but none has shown convincing benefit in vivo.
Feline Leukemia Virus	Extremely variable and depends on the strain involved, challenge dose, host immune function, age, and coinfections Uncommonly, FeLV causes enteritis that clinically and histologically resembles that caused by FPV, except that lymphoid depletion is absent	1.Screening via ELISA or related immunochromatographic in-house assays for free FeLV antigen (targets FeLV p27 antigen in serum or blood) 2.IFA on serum or bone marrow targets FeLV antigen in blood cells 3.PCR on blood, bone marrow, or tissue targets FeLV RNA or proviral DNA	FeLV-A (present in all cats with FeLV) FeLV-B FeLV-C	The use of tears or saliva is suboptimal compared to serum for ELISA testing. Infected cats should be housed indoors to prevent spread of infection to other cats. Avoid feeding raw-food diets to infected cats.	Supportive care with management of opportunistic infections when warranted. Antiviral agents and immunomodulators are of limited benefit for treatment of cats with FeLV infections.

CPV, Canine parvovirus; DFA, direct fluorescent antibody; ELISA, Enzyme-linked immunosorbent assay; FCoV, feline coronavirus; FDA, U.S. Food and Drug Administration; FeLV, feline leukemia virus; FIP, feline infectious peritonitis; FPV, feline panleukopenia virus; IFA, indirect immunofluorescent antibody assay; IV, intravenous; PCR, polymerase chain reaction; RT-PCR, reverse transcriptase-polymerase chain reaction