Abstract

A twenty-three year-old, 196 kg, female Atlantic bottlenose dolphin (Tursiops truncatus) was presented for partial to complete anorexia for four days. Diet consisted of herring, capelin, and squid. A physical examination was performed under manual restraint.

The dolphin was bright and alert with a good energy level. She was in good body condition with blubber and fat stores estimated to be adequate. She had few skin lesions consistent with poxviral dermatopathy (tattoo lesions). The oral cavity was examined and no lesions were noted. Gastric samples were taken via stomach tube for cytological evaluation, and respiratory and fecal samples were obtained for cytology and bacterial and fungal culture. For cytological examination, both Gram stains and Diff-Quick were utilized. After the gastric sample was taken, 1 liter of tap water was administered via the stomach tube and approximately 1 kg of fish force-fed. Blood was collected from the ventral fluke vein and a CBC, serum chemistries, and ESR were performed. No murmurs were detected upon auscultation. Upon cessation of restraint, the animal ate 1 kg of fish.

Evaluation of the diagnostic samples showed only a slight elevation in the WBC (7,800 x 10³/UL; individual normal 4,500 x 10³/UL) and the ESR (52 mm/60 min). No other abnormalities in the blood picture were noted. The gastric cytology and bacterial culture were within normal limits. Cultures of respiratory system and feces revealed normal flora. Cytology from the blowhole showed an increased number of bacteria, though a normal distribution, and increased amounts of mucous.

The next day (day 6 of clinical course), the animal was alert and bright, but very agitated. She was again disinterested in feeding, but did consume one fish, which was medicated with 30 mg of dexamethasone. That afternoon she consumed 2.0 kg of fish and remained alert.

For the next few days, the animal remained mostly anorectic, with rare instances of unassisted feeding. She was maintained on oral fluids given via a stomach tube and assisted feeding. She had a minimum of 3 kg of herring per day with 2 liters of water. On day 9, another gastric sample was pulled. Several minor oral erosions were noted while obtaining the gastric sample. Gastric cytology showed an increase in mucous and white blood cells. A blood sample also showed a slight increase in the WBC and again, an elevated ESR. Cimetidine hydrochloride, 900 mg PO BID, azithromycin, 500 mg PO SID, and itraconizole, 100 mg PO SID to combat any potential gastritis and other possible infectious causes of the inflammatory response indicated by the elevated ESR and WBC.

On day 11 after no improvement in attitude or appetite, another complete physical examination was performed. This included all diagnostics in the first exam as well as a sonogram and gastroscopy. The abdominal sonogram showed a non-pregnant animal with no abnormalities. The thoracic cavity showed a right lung field of increased density as indicated by an obvious echoic pattern going into the lung and not bouncing off the usual air interface. There was also the presence of a fluid density in the pleural space, indicating potential pleuritis, pneumonia, or hydrothorax. Gastroscopy was unremarkable with no obvious areas of ulceration or foci of infection. Blood work continued to be WNL besides persistence of the increased ESR (43 mm/60 min) and WBC (8,500 x 10³/UL). Prior medication regimen was continued, and a respiratory infection was considered likely given the sonogram, increased number of bacteria in the blowhole cytology, and elevated WBC and ESR.

On day 14 the animal appeared somewhat improved. She was eating most of her diet, and ESR and WBC were declining toward normal values. The ESR had gone from 52 to 24 mm/60 min. over the course of treatment and the WBC had dropped from 8,500 x 10³/UL back to her normal of 4,500 x 10³/UL.

By day 16 a regular regime of treatment, assisted feeding, and tubing with water had been established. There was little to no change in the animal, except signs of weight loss and increased lethargy. Repeat diagnostics remained fairly constant. Thoracic radiographs were obtained to help determine the status of the lungs. The right lung showed a somewhat nodular pattern where the left lung was difficult to visualize due to an overall increase in density.

On day 17 she became completely anorectic and was agitated. At approximately 16:00 hours, she began to list to her left side while floating in the medical pool. Shortly thereafter she began episodic bouts of hyperactivity and gaping of the mouth and then died at approximately 18:00 hours.

At necropsy the dolphin weighed approximately 185 kilograms with a rostrum to fluke notch length of 258.0 cm. Muscling and blubber layer (2.8 cm) were considered adequate. No abdominal or cardiac groove adipose stores were noted. The thoracic cavity contained 2.6 liters of pale yellow fluid with few, small, free-floating off-white, friable masses consistent with fibrin aggregates. Fluid analysis and Diff-Quick cytology revealed a total protein of 4.2 g/dl and moderate cellularity comprised of primarily macrophages with vacuolated cytoplasm with lesser numbers of neutrophils. The lungs were diffusely firm to rubbery, mottled pale red to pale tan, with a single 4x4x3 cm irregular white region rimmed by a 1 mm red zone in the mid-dorsal aspect of the right lung, consistent with necrosis. The pleura had few, randomly distributed, up to 4 mm diameter, irregular adherent fibrin aggregates. Cytology of lung impression smears showed moderate numbers of vacuolated macrophages with rare erythrophagocytosis and few neutrophils and erythrocytes. Additional gross lesions included small erosions in the second gastric compartment, a focal gingival ulcer, and few regions of cutaneous hyperpigmentation consistent with tattoo.

Histologically the lung had extensive alveolar accumulations of macrophages with occasional admixed lesser numbers of neutrophils and erythrocytes as well as moderate quantities of granular proteinic material and rarely fibrin. Mild, multifocal Type II pneumocyte hyperplasia and diffuse, moderate interstitial edema were also noted. The right lung had a focal zone of necrosis and suppuration with intralesional cocci bacteria. The liver had moderately severe, diffuse lobular collapse and central veins were often collapsed. Centrilobular regions were mildly congested and contained moderate numbers of hemosiderin-laden macrophages with some macrophages containing phagocytosed erythrocytes or erythrocytic debris. Centrilobular hepatic plates were tortuous or fragmented, composed of atrophied hepatocytes containing moderate quantities of hemosiderin. Lymph nodes from all regions were moderately edematous with mild to moderate sinus histiocytosis. The fundic stomach had few small erosions. Remaining histologic lesions were incidental or of no clinical significance.

Chronic passive congestion of the liver, pulmonary edema and pleural effusion were consistent with congestive heart failure. Focal necrosuppurative pneumonia was considered an opportunistic bacterial infection late in clinical course. Notably no gross or histologic cardiac lesions were noted aside from the absence of adipose in the cardiac groove. Clinical signs were initially non-specific, though a primary rule out of respiratory infection, probably pneumonia, was established irrespective of the only mild elevation of the WBC. Anorexia and lethargy were the only clinical signs consistent with heart failure and were non-specific. Age could have been construed as a risk factor. Other signs often observed in heart failure, such as cough, dyspnea, syncope, and cyanosis were lacking in this case. Ascites was not a feature however pleural fluid was evidenced via sonography and probably thoracocentesis would have been a useful diagnostic modality in this case. Retrospectively, cardiac sonography and possibly electrocardiography may have been useful for defining impaired cardiac function. In the absence of additional clinical indicators of potential cardiac impairment, these were not contemplated and can be difficult to both perform and assess in cetaceans.

Heart failure appears to be a relatively uncommon phenomenon in cetaceans, with only a single reporting in the literature, secondary to cardiomyopathy.¹ In the case presented here, no gross or histologic cardiac abnormalities were noted, and the cause of heart failure was obscure. Possibly a derangement of contractility or conduction existed though this is speculative. Heart failure could be considered a differential in middle-aged or older captive dolphins with vague respiratory signs.

Acknowledgements

The authors wish to thank Dr. T. Meehan, Dr. L.S. Zwick, keepers and technicians at the Brookfield Zoo hospital and Seven Seas exhibit, and Jane Chladny and the University of Illinois Veterinary Diagnostic Laboratory histopathology laboratory.

References

1.  Bossart GD, DK Odell, NH Altman. 1985. Cardiomyopathy in stranded pygmy and dwarf sperm whales. Journal of the American Veterinary Medical Association 187(11): 1137-1140.