Abstract

Toxoplasma gondii is a parasite of world-wide distribution in all warm-blooded mammals causing neonatal diseases and occasionally abortions. Intestinal toxoplasmosis was diagnosed in a captive neonatal bottlenose dolphin (Tursiops truncatus gilli) that died after an acute onset of diarrhea.

The parents were wild-caught and maintained in captivity for eight years. They had had no history of medical problems. Relevant history of the mother included a previous dolphin calf that died from acute clostridial infection at the age of 11 months. The pregnancy was considered normal. Animal management methods meet the AZA standards, which included monthly blood analysis.

At parturition, labor was delayed for 2.5 hours and had to be manually assisted. The placenta was expelled after 8 hours, and lactation began 6 hours after. At birth, the calf appeared normal, and no abnormalities were recorded for 12 days. At that time, the keeper reported that the mother was excreting milk in the pool and the frequency of lactation diminished. Clinical abnormalities included severe diarrhea, decreased activity, and abnormal posture. Blood samples revealed a severely dehydrated animal with a moderate leukocytosis. As the condition worsened, oral electrolytes were given via gastric tube as well as supportive therapy including antibiotics, but the animal died shortly after.

One relevant necropsy finding was that the intestine had progressive changes of color and some hemorrhages. The content of the intestine suggested digested blood towards the rectum. Microscopic lesions were more prominent in the small intestine, showing an acute severe nonsuppurative enteritis associated with numerous free and intracellular tachyzoites and cysts that morphologically resembled T.gondii. Other lesions included a moderate interstitial pneumonia, mild nonsuppurative myocarditis, mild nonsuppurative hepatitis with diffuse hepatic lipidosis, and a mild depletion of lymph nodes. The lungs also had necrotic zones.

The presumptive diagnosis of intestinal toxoplasmosis was confirmed by immunohistochemistry with anti-T.gondii polyclonal rabbit serum. The presence of abundant numbers of T. gondi organisms in enteric epithelial cells suggest an oral rout of infection.