Abstract

Diseases of the intestinal system are often some of the most difficult to understand, diagnose and treat. This is especially true in cetacean species where gastroscopy is usually limited to the first of multiple chambers, where fecal material is already liquid and where sampling may be complicated by acquisition and difficulties in handling. Clinical disease of the gastric chambers, and the small and large bowel can be a challenge to detect. Antibiotic use has resulted in better survival rates in cetaceans but its use is affected by experience, comfort and prejudice. The small numbers of cetaceans maintained in controlled environments slows the progress in the classification of intestinal disease conditions.

Signs of intestinal illness in cetaceans vary and may include loss of appetite as well as regurgitation, vomiting, diarrhea, depression, lethargy, isolation and decreased cooperation. Initial diagnostic tests usually include a visual evaluation, a complete blood count, and serum chemistries. Bloodwork findings are often nonspecific and may include anemia, an elevated white blood cell granulocyte count, elevated fibrinogen, elevated sedimentation rate, and a decreased serum iron.

Oral Cavity

Diseases of the oral cavity may include trauma, infection as a result of virus, bacteria, fungi and yeast, tumors, foreign bodies, and metabolic disorders. While diagnostic techniques are similar to other species, differentiation of etiologic possibilities may be challenging. Some Candida infections may only show a change in mucosal coloration resulting in paleness of the affected area. The lesions may be circular in shape or appear as an advancing pale border that slowly spreads across the mucosa over a number of weeks. Direct culture with swabs is sometimes nonproductive. Cytological exam for invasive candidiasis from culturettes or scrapings is also frustrating. When biopsy is difficult to implement for possible Candida infections then a deep scraping can be done. Improved recovery of the organism is accomplished by placing the instrument edge directly into fungal agar.

Esophageal Disease

Diseases of the esophagus are not common, though ulceration associated with Candida and secondary bacterial infection are associated with individuals who show chronic weight loss and signs similar to acid reflux. Diagnosis can be suggested by cytological sampling from a stomach tube, though it should be differentiated from gastritis endoscopically with supportive cytology and culture. Anorexia, resistance to force feeding, and regurgitation may be seen clinically.

Gastric Disease

Diseases can involve a number of chambers and exhibit a number of different presentations. Ulceration in the first chamber is best diagnosed with gastroscopy. If a scope is not available then a stomach tube should be passed and a sample taken for cytology, pH, and culture. Cytological findings may include red cells, basal cells, inflammatory cells and possible infectious agents such as yeast elements or parasites in newly acquired animals. Grossly the stomach sample may be red to brown in color from hemorrhage or from the diet. Often the stomach contents have a strong sour odor due to poor digestion and bacterial overgrowth. Cytological abnormalities may be back flushed from the second chamber so the exact location can not be determined. Blood work findings may include an elevated white count, a decreasing red count, decreased platelets, elevated sedimentation rate, elevated fibrinogen, and decreased serum iron in more severe cases. Ulcers of the second and third chamber or the duodenal ampulla are not amenable to endoscopy and diagnosis may be dependent on recognition of gastric symptoms and subtle blood work changes as noted. In some cases the animal may need to be treated symptomatically with pH modification, coating agents, and antibiotics. Treatment based on antibiotic use appears to be more successful than those without. Acid modification may need to be prolonged with relapse possible if therapy is discontinued before complete resolution of the lesions. Over use of H2 blockers can result in poor digestion of fish bones resulting in regurgitation or temporary impaction of the stomach. This problem can be managed by reduction of the drug involved and by monitoring gastric pH. One of the least emphasized factors is the timing of treatment. Individuals which are already thin or emaciated require additional caloric intake at the same time the clinician is attempting to manage food amounts. If too much body condition is lost during therapy the ulceration may not heal properly and could result in perforation. Clues to potential complications can be seen in the poor healing of external lesions such as rake marks.

Diseases of the Small and Large Intestine

Duodenitis is not common in cetaceans compared to other types of gastrointestinal disease. A group of beached rough tooth dolphins (Steno bredanensis) with severe duodenitis had elevated BUN, anemia, hypoproteinemia, reticulocytosis, and elevated sedimentation rates. Histologic findings included necrotizing, suppurative, plasmacytic, eosinophilic duodenitis and enteritis. There were also other systems affected including nephritis, arteritis and lymphadenitis.

Typical diagnostic techniques for lower bowel disease in cetaceans include aerobic and anaerobic cultures, cytology of fecal material, and parasite exam. To aid in bacterial flora interpretation it is recommended that fecal cultures be done on animals while they are clinically normal. Anaerobic cultures are useful in determining the presence of possible pathogens and in correlating this with cytology results. Work done at SeaWorld on clostridia organisms showed that the vast majority of isolates were Clostidium perfringens type A and that about 70% were toxin producers. Human classifications of bowel disease include Inflammatory Bowel Disease (Crohn's Disease, Ulcerative Colitis, Lymphocytic Colitis, Collagenous Colitis), Irritable Bowel Disease (etiology unknown), and infectious Bowel Disease (Traveler's Diarrhea-bacterial, viral, parasitic). Another bacterial infection, Clostridium difficile, may be linked to antibiotic use and their secondary effects on the intestinal flora.

Feces for cytology are collected with a flexible open-ended tube with sterile technique. Cytology results in colitis cases may vary in findings and severity. Inflammatory cells may be classified based on morphology and numbers. The bacterial flora is evaluated for composition and morphology. Special note is taken when there is a predominance of one morphologic type, such as bacilli with the presence of spores that may indicate a clostridia involvement.

One area that has not been adequately utilized is colonoscopy. It is often assumed that the size of the rectum and the liquid fecal material will make this a low yield technique. While few attempts are known this deserves further evaluation. The eventual goal is to establish protocols for evaluation of the intestinal tract utilizing cytology, culture and histology to categorize findings into common disease categories.