Treatment of esophagogastric intussusception due to cryptosporidiosis using paromomycin in a corn snake (Pantherophis guttatus)

Abstract

A 3-year-old captive corn snake (Pantherophis guttatus) was taken our veterinary clinic with a complaint of intermittent body swelling. Radiography revealed soft-tissue swelling, and ultrasonography confirmed intussusception of the digestive tract. Celiotomy revealed esophagogastric intussusception, which was subsequently corrected. Histopathological examination of gastric mucosal biopsy and polymerase chain reaction (PCR) from feces were revealed protozoan parasitism within the lesion and detected specific genes of Cryptosporidium spp. Oral administration of paromomycin at 100 mg/kg once daily for 10 days, subsequently twice weekly for 90 days under strict hygiene management were conducted as postoperative treatment. The snake was in good clinical health. PCR and ultrasonography for Cryptosporidium spp. 752 days after surgery showed no evidence of cryptosporidiosis.

Cryptosporidium is a coccidian protozoan of the phylum Apicomplexa that is an intestinal parasite infecting various animals. Cryptosporidium spp. that infects reptiles include Cryptosporidium varanii in lizards, C. ducismarci in tortoises, and C. serpentis in snakes [5, 8, 18]. Cryptosporidium serpentis is highly pathogenic to snakes and induces hypertrophic gastritis, with clinical signs including postprandial regurgitation, inappetence, lethargy and midbody swelling [3]. There have been several reports of the oral administration of hyperimmune bovine colostrum, halofuginone, or paromomycin to treat cryptosporidiosis in reptiles [2, 6, 7, 14, 15]. However, halofuginone has been reported to be ineffective against cryptosporidiosis in reptiles [7]. The efficacy of paromomycin is affected by differences in its susceptibility to Cryptosporidium spp. and reptile species [15]. The efficacy of paromomycin in treating cryptosporidiosis in snakes has been reported in the king cobra (Ophiophagus hannah) and eastern indigo snake (Drymarchon couperi) [2, 15].

A previous study reported gastric intussusceptions associated with cryptosporidiosis in a corn snake (Pantherophis guttatus), and surgical reduction of the intussusceptions and gastropexy was performed; however, paromomycin was not administered; subsequently, intermittent regurgitations continued, and the snake died 15 months later [1]. There are no reports on the efficacy of paromomycin against cryptosporidiosis in corn snakes.

We report the case of a 3-year-old, captive, male cone snake weighing 66.0 g. The snake was fed two frozen-thawed neonatal mice approximately once every 2 weeks. The temperature and humidity were maintained at 28–30°C and 60–70%, respectively, and pet sheets were used as flooring material for the snake from the beginning of the rearing. The owner reported that midbody swelling had been observed intermittently for the past month. However, 2 weeks before admission, the snake was fed a usual diet and responded well to food, with no signs of regurgitation after meals. The snake exhibited persistent swelling in the same area for 1 week before admission. During the physical examination, the swelling was approximately 6 cm in the craniocaudal area in the rostral third of the body. There were no signs of emaciation or dehydration, and the activity was normal.

To examine the swollen area in detail, radiography, ultrasonography, and fecal examination using sucrose flotation were performed on the same day. Radiography revealed only soft-tissue swelling at the site of the swelling, and no abnormal gastrointestinal gases or osteolysis were observed (Fig. 1). Ultrasonography of the swelling area revealed a concentric ring appearance of the digestive tract near the esophagus, indicating intussusception (Fig. 2a) [12]. Fecal examination did not detect any pathogens. Because ultrasonography revealed intussusception in the swollen area, surgery was performed under general anesthesia to reduce the intussusception. Anesthesia was induced by subcutaneously administering alfaxalone (6 mg/kg, alfaxalone multidose; Meiji Animal Health Co., Ltd., Kumamoto, Japan), midazolam (0.5 mg/kg, midazolam injection solution 10 mg; Nichi-Iko Pharmaceutical Co., Ltd., Tokyo, Japan), butorphanol (0.4 mg/kg, Vetorphale 5 mg; Meiji Animal Health Co., Ltd.). Subsequently, the trachea was intubated using a 5-Fr catheter (Atom Pink-catheter; Atom Medical Co., Ltd., Tokyo, Japan) and anesthesia was maintained via isoflurane inhalation using a closed-circuit anesthesia system during surgery. The snake was mechanically ventilated (COMPOS β-EV; Metan Co., Ltd., Kawaguchi, Japan) throughout the surgery. Positive pressure ventilation was performed with an inspiratory pressure of 10 cmH₂O and a frequency of four breaths/min.

Fig. 1.

Preoperative radiographs of the snake. These radiographs show craniocaudal swelling (allowheads) of approximately 6 cm in the rostral third of the body. (a) Dorsiventral view. (b) Right lateral view.

Fig. 2.

Transverse ultrasound images of the swollen area. (a) Preoperative ultrasonogram reveals a concentric ring appearance of the digestive tract near the esophagus, indicating intussusception. (b) Ultrasonogram taken 752 days after surgery reveals no signs of intussusception.

The surgery was initiated with the snake in the left lateral recumbency, and a 5-cm incision was made in the right ventral scale in the craniocaudal direction. The muscle layer below the edge of the rib was incised. When the swelling was confirmed under celiotomy, it was found that the esophagus had invaginated into the stomach, causing esophagogastric intussusception (Fig. 3). Although blood flow to the intussuscepted area was not poor, adhesions were observed around the intussuscepted area. The intussuscepted area was reduced by grasping it with ring tweezers and peeling off the adhesions. Because preoperative ultrasonography and intraoperative macroscopic findings showed swelling of the stomach, the stomach body was incised after reducing the intussusception and a biopsy of the gastric mucosa was performed. The abdominal muscles were then sutured with simple ligature sutures using 6–0 absorbable thread (Monodiox; Alfresa Pharma Co., Ltd., Osaka, Japan), and the skin was sutured with simple ligature sutures using 5–0 nonabsorbable thread (ELP Ao Nylon; Akiyama Medical MFG. Co., Ltd., Tokyo, Japan). After surgery, meloxicam (0.5 mg/kg, meloxicam tablets 5 mg; Nichi-Iko Pharmaceutical Co., Ltd.) and enrofloxacin (5 mg/kg, Baytril; Elanco Japan Co., Ltd., Tokyo, Japan) were orally administered once daily for 7 days.

Fig. 3.

Intraoperative gross findings image of the swelling area. Surgical findings indicate that the swollen area has caused the esophagus (E) to invaginate into the stomach (G), resulting in esophagogastric intussusception.

Gastric mucosal tissue was fixed in 10% neutral-buffered formalin, routinely processed, and stained with hematoxylin and eosin. Histopathological examination of the gastric mucosal tissue revealed diffuse thickening of the gastric mucosa with elongated and partially branched glandular tissue. Numerous protozoa, approximately 5–10 μm in diameter, were present on the mucosal epithelial surface and within the crypts (Fig. 4). Extensive edema and lymphatic dilation were observed from the lamina propria to the submucosal tissue, and inflammatory cells, mainly lymphocytes and plasma cells, infiltrated the interstitium. To detect gene from Cryptosporidium spp., fecal samples were extracted. PCR was performed using the IDEXX proprietary RealPCR™ service platform (IDEXX Laboratories Japan Co., Ltd., Tokyo, Japan). The target gene for enteropathogenic detection was the Cryptosporidium spp. small subunit ribosomal RNA (ssrRNA) gene (A093489). The Cryptosporidium spp. ssrRNA was detected in the fecal samples. However, because it was not possible to sequence the amplified genes, the Cryptosporidium species could not be identified. This snake was diagnosed with cryptosporidiosis-associated esophagogastric intussusception based on surgical findings, histopathological findings, and PCR testing.

Fig. 4.

Hematoxylin and eosin-stained histopathologic image of gastric mucosal tissue. Histopathological examination reveals hypertrophic gastritis with intralesional protozoan parasites. Bar=100 μm. (a) Showing edematous thickening of the lamina propria and submucosa and lymphocytic infiltration. (b) Showing mucosal epithelium. (c) Showing parasitic protozoa.

Oral administration of paromomycin (100 mg/kg, Ameparomo; Pfizer Japan Inc., Tokyo, Japan) was initiated the day after surgery. It was administered once daily for the first 10 days, followed by twice a week for the next 90 days. Paromomycin was dissolved in 5% glucose solution at a concentration of 50 mg/mL and orally administered using a syringe. Owners were instructed to wear latex gloves when handling the snake and performing cage maintenance. In addition, if any excrement was found, they were instructed to remove it before drying. The cages were cleaned by spraying with 5% dilution of sodium hypochlorite, rinsing with tap water, and drying. One month after surgery, feeding was resumed with a diet smaller in size and quantity than the usual diet, and the snake passed stools regularly after eating and gained weight. Therefore, the oral administration of paromomycin was discontinued 3 months after surgery. At 295 and 752 postoperative days, the body weights were 100 and 267 g, respectively. In addition, PCR testing for Cryptosporidium in fecal samples on postoperative days 295 and 752 was negative. Furthermore, ultrasonography was performed 752 days after surgery, and results showed no recurrence of intussusception (Fig. 2b). Until the final follow-up (800 days after surgery), there was no recurrence of intussusception, swelling in the midbody, or gastrointestinal symptoms such as loss of appetite or regurgitation.

In veterinary clinics, fecal testing using the sucrose flotation method is a well-known method for detecting Cryptosporidium in snakes [11, 16]. In this case, oocysts were not identified by fecal testing using the sucrose flotation method, but Cryptosporidium spp. gene was detected by PCR testing. Therefore, PCR testing should be considered for the detection of Cryptosporidium [17].

The multiple concentric rings of the digestive tract observed on ultrasonography were consistent with the intussusception found on celiotomy. Gastric tissue biopsy confirmed gastrointestinal intussusception associated with cryptosporidiosis. Cryptosporidiosis in snakes causes regurgitation due to thickening of the gastric mucosa [16]. In this case, hypertrophic gastritis was also observed histologically. In general, vomiting due to direct stimulation of gastrointestinal structures occurs when mechanoreceptors in the pharynx and tension and chemoreceptors in the gastric and duodenal mucosa are stimulated, sending signals to the vomiting center in the brainstem [10]. In previous reports and in this case, the epithelium on the gastric surface and in gastric glands was hyperplastic, and the lamina propria contained small numbers of heterophils, lymphocytes, and plasma cells [1]. In this case, chronic hypertrophic gastritis due to cryptosporidiosis may have resulted in abnormalities in gastric and esophageal peristalsis, leading to esophagogastric intussusception.

The treatment of cryptosporidiosis with paromomycin has been reported in several reptile species [2, 5, 8, 14, 15]. Several reports have indicated that oral paromomycin sulfate may be efficacious in suppressing oocyst shedding and even eliminating infection [8, 15]. In Hermann’s tortoises (Testudo hermanni), oral administration of 100 mg/kg of paromomycin initially suppressed clinical signs and oocyst shedding, but the disease subsequently recurred [14]. Higher oral doses of paromomycin (360 mg/kg) are effective against eastern indigo snakes (Drymarchon couperi), king cobras (Ophiophagus hannah), and bearded dragons (Pogona vitticeps) [2, 8, 15]. Treatment should consider the potential nephrotoxicity, ototoxicity, and risk of mucosal breach associated with the aminoglycoside paromomycin [9]. In this case, due to concerns about side effects from using paromomycin at high doses, paromomycin was administered orally at 100 mg/kg once daily for 10 days, followed by the same dose twice weekly for 90 days [9]. There were no drug-related side effects during treatment. Cryptosporidium serpentis oocysts are reported to be shed in feces and transmitted via the fecal–oral route [16]. Strict waste management reduces the risk of reinfection [13].

Monitoring oocyst shedding for extended periods using PCR may be an option for documenting resolution in snakes [17]. PCR tests after treatment were consistently negative. However, this does not mean that Cryptosporidium spp. has been completely eradicated. Histological examination via gastroscopic biopsy under anesthesia is useful for proving the absence of Cryptosporidium spp. [4]. However, invasive stomach and intestinal tissue biopsies are difficult in asymptomatic pet snakes [15]. A feasible clinical examination test for cryptosporidiosis in snakes is ultrasonography, which detects gastric mucosal thickening [16]. Follow-up treatment of snake cryptosporidiosis with repeated fecal PCR testing and gastrointestinal ultrasonography over time may aid in the clinical diagnosis. In captive corn snakes with cryptosporidiosis-associated intussusception, the combination of strict hygiene measures and oral administration of paromomycin after surgical correction may reduce the recurrence of intussusception and increase clinical well-being and survival.

CONFLICT OF INTEREST

There is no conflict of interest.