Working up gastrointestinal disease in the ferret (Proceedings)

Gastrointestinal disease is common in pet ferrets and is frequently accompanied by weight loss and wasting. Unique anatomy and physiology, including rapid gastrointestinal transit time and short, simple gastrointestinal tract makes the ferret predisposed to gastrointestinal disease. Ferrets are used as laboratory model for a number of human disorders involving the gastrointestinal tract, including gastric and intestinal ulcers, gastric carcinoma and helicobacter gastritis.1 Etiologies are many, can be multi-factorial, and can include foreign body-related disease, bacteria, virus, neoplasia, inflammatory conditions, stress and dietary change. Gastrointestinal disease, in particular diarrhea, can be secondary to the stress of other primary non-GI related diseases. Some practitioners report improvement in some refractory cases with diet modification, which suggests dietary allergen or intolerance. A thorough work up is critical for distinction between etiologies typically producing similar clinical signs and symptoms.1,2

Specific Gastrointestinal Diseases in the Ferret

It is beyond the scope of these proceedings to describe all causes of diarrhea in ferrets in detail. A list of both documented and anecdotally reported contributors are listed in Table 1. Keep in mind that many cases involve more than one disease process and can be complicated by psychologic stress. Therefore, ANY disease process could contribute to diarrhea in the ferret.

Table 1. Diseases producing intermittent or chronic diarrhea in ferrets.

Working Up Gastrointestinal Disease in the Ferret

Working Up Gastrointestinal Disease: the History and Physical Examination

While working up gastrointestinal disease in ferrets is seldom straight forward, careful attention to history and signalment may reveal some important patterns. Ferrets under one year of age are more prone to foreign body ingestion, coccidia and proliferative colitis, while coronavirus and Helicobacter mustelae typically affect older ferrets.1,2 Diarrhea occurring soon after introduction of a new ferret into the household could suggest an infectious etiology, such as coronavirus, coccidia or possibly giardia. Infectious agents such as Lawsonia and Mycobacteria, however, tend to affect only a few members of a group.1,2 Diarrhea occurring soon after an unusual event such as travel, veterinary visit, change in social structure (addition or loss of a social companion) or normal routine may reflect stress and not underlying disease.

While some assumptions can be made based on clinical signs and history, it is impossible to diagnosis specific gastrointestinal disease based on observations such as the color and character of diarrhea. In other words, "green slime" does not always equal epizootic catarrhal enteritis (ECE), and making such an assumption can delay proper diagnosis and treatment.

Working Up Gastrointestinal Disease: Clinical Pathology

Considering the numerous etiologies of ferret gastrointestinal disease, workup must be thorough. Complete blood count (CBC) and chemistry panel are non-specific but can provide clues to diagnosis and help evaluate overall patient condition. In many cases, biochemical changes simply reflect patient dehydration, anorexia and wasting. Anemia can occur from chronic inflammation and/or blood loss.

Routine culture and sensitivity can help identify primary or secondary bacterial pathogens. Helicobacter mustelae is a common pathogen of ferrets, but cannot be identified on routine culture. Biopsy and histopathology of gastric samples, and/or PCR of gastric, colonic and/or mouth swabs provide a more specific diagnosis. As Helicobacter mustelae is thought to be present in nearly all ferrets, and apparently does not always produce disease, the most useful application of PCR may be to monitor response to therapy and detect reinfection. 4

Working Up Gastrointestinal Disease: Radiography and Ultrasound

Radiography can be useful in the diagnosis of gastrointestinal disease. Abnormal gas patterns can suggest foreign body obstruction or enteritis. Survey radiographs can often reveal evidence of GI masses or thickened bowel loops. Contrast media have been used to evaluate the gastrointestinal tract. A recent study on results of the use of barium sulfate, 8-13 ml/kg, indicated that small intestinal transit time was less than 2 hours. Visualization of the barium-filled small bowel was optimal at 20 and 40 minutes post barium administration. Small bowel loops in these normal ferrets did not exceed 5-7 mm in width. The use of ketamine and diazepam to facilitate radiography did not significantly slow GI transit time in these ferrets.24

Abdominal ultrasonography can be an extremely effective diagnostic tool for evaluation of abdominal organs in dogs, cats and other mammals. Information on organ size, shape, density and even gastrointestinal motility can be beneficial. The most common reported usage in the pet ferret is for evaluation of adrenal glands in ferrets with suspected adrenal neoplasia, but gastrointestinal ultrasound should provide benefits similar to those reported in canine and feline patients.

Working Up Gastrointestinal Disease: Endoscopy

Rigid or flexible endoscopy of the gastrointestinal tract is a common diagnostic tool for diagnosis of refractory gastrointestinal disease in dogs and cats. Few reports exist documenting its usefulness in ferrets, but can be expected to provide similar benefits. The author has reported use of a semi-flexible 1.2 mm endoscope with air insufflation to document gastric ulceration in a ferret.4

Laparoscopy has also been described in the ferret. The technique is relatively simple, but primary use is for visualization and biopsy of those organs available for collection via simple clamshell or punch-style biopsy forceps or True-cut needles, such as liver, pancreas and kidney.25 Full-thickness gastrointestinal biopsies must be obtained via traditional laparotomy.

Working Up Gastrointestinal Disease: Gastrointestinal Biopsy

Biopsy of gastrointestinal tract remains the most specific test for confirmation of etiology, especially in those cases refractory to treatment. Diagnosis of gastrointestinal neoplasia, inflammatory gastrointestinal disease and disease secondary to unusual forms of bacteria is extremely difficult without biopsy. Biopsy and histopathology are extremely useful for monitoring response to treatment. ECE virus and canine distemper virus can also be detected in biopsy samples of the small intestine through immunohistochemistry and PCR.14, 15

In human medicine, gastrointestinal biopsy remains the gold standard for diagnosis of helicobacter-related gastroenteritis, as simple presence of the organism does not always correlate well with disease.26

Gastric and/or colonic mucosal biopsy samples can be collected via semi-flexible or flexible endoscopy. Surgical biopsy during laparotomy, however, gives the added advantage of allowing visualization and targeting of grossly abnormal sections, and collection of full-thickness samples.

Working Up Gastrointestinal Disease: Miscellaneous Testing

As mentioned earlier, specific PCR tests are available for detection of FECV, canine distemper, Rotavirus and Helicobacter mustalae. Novel PCR tests are also offered for detection of Salmonella sp. and for Mycobacteria sp. (Table 2).

Table 2. Specialized polymerase chain reaction testing to aid diagnosis of gastrointestinal disease in ferrets.

Some gastrointestinal diseases such as Helicobacter-related gastric ulceration produce hematocheaizia. Fecal occult blood testing can help confirm the presence of blood. As some diseases produce only intermittent bleeding, a single negative occult fecal blood test does not rule out gastrointestinal hemorrhage.3,4 The Hemoccult Fecal Occult Blood Test (Beckman Coulter, www.coulter.com) has been evaluated in clinical practice for use in ferrets. Elimination of dietary heme must precede testing, and can be accomplished by feeding a non-heme containing diet. Johnson-Delaney and Lennox demonstrated success with the use of two carnivore critical care diets (Quantum Series Enteral Carnivore Diet, Walkabout Farms, Pembroke, VA, www.herpnutrition.com; Oxbow Pet Products, Murdock, NE, www.oxbowhay.com)1,4

Treatment of Gastrointestinal Disease in the Ferret

Treatment options vary with underlying etiology (Table 3). In the absence of definitive diagnosis, supportive therapy can include rehydration and correction of electrolyte imbalances, nutritional support, and gastrointestinal motility modifying drugs and protectants. Supportive therapy is also important in those cases of GI disease where supportive therapy is the only option, for example viral enteritis. Anti-infective drugs can specifically target etiologies such as bacteria or protozoa. Chemotherapy has been effective in gastrointestinal neoplasia, in particular lymphoma.28 As gastrointestinal lymphoma may be linked to Helicobacter sp. in humans and ferrets, treatment of lymphoma likely should include therapy for Helicobacter sp. as well, as is sometimes indicated in human patients.29 Some authors have advocated immune suppression therapy in cases of inflammatory bowel disease.30 Caution must be used, as underlying cause is frequently uncertain and may involve an infectious agent. There are anecdotal reports of successful resolution of chronic GI disease through elimination of specific dietary ingredients, for example, wheat corn, or beef.

Table 3. Formulary of drugs used to treat gastrointestinal disease in ferrets.

References available from the author upon request.

Reprinted in part with permission from the North American Veterinary Conference, 2007.