Abstract
Five recently wild-caught 8- to 11-kg whitetip reef sharks (Triaenodon obesus) were treated for nematodiasis due to anemia, unthrifty condition, and high fecal loads of nematode ova. Levamisole (8 mg/kg PO) did not reduce shedding. On days 74–75 of quarantine, a combination tablet of pyrantel/praziquantel/febantel was administered (10/10/50 mg/kg PO), and on day 77, due to 'flashing' behavior, a praziquantel bath was started (2 mg/L). On day 78, the sharks were lethargic with a reduced feeding response. The bath treatment was discontinued. Clinical signs progressed to significant lethargy, dyspnea and tachypnea, cutaneous vesicles and ulcers, and anorexia. Major diagnostic findings included severe anemia and abundant larval gill nematodes. Supportive care included hyperoxygenation, steroids, fluid and nutritional support, antibiotics, antifungals, epoetin, and gastroprotectants. Clinical signs never resolved and all five sharks died or were euthanized between days 94 and 216.
Histopathology showed intravascular larval nematodes in the gills with mild to severe lymphocytic infiltration and focal necrosis (5/5), rare larval nematodes intravascularly in the liver and spleen and in a dermal granuloma (2/5), and adult nematodes in the stomach (1/5). Other changes included gastroenteritis or enteritis (5/5), subacute renal tubular necrosis (2/5), vasculitis and edema (2/5), Aspergillus terreus splenitis or hepatitis (2/5), and Aeromonas sp. septicemia (1/5).
Morbidity and mortality was likely due to a severe inflammatory response following the acute death of larval nematodes. Gill nematodes are not well described in elasmobranchs and the clinical significance of these parasites is unknown.1,2 However, tissue biopsies as well as possible sequelae from the death of histozoic nematodes should be considered prior to treatment.
Acknowledgments
We would like to thank Dr. Sarah Poynton, Dr. Ian Beveridge, and Dr. Karrie Rose for help with parasite identification.
* Presenting author
Literature Cited
1. Benz, G.W. 2004. Metazoan parasites and associates of Chondrichthyans with emphasis on taxa harmful to captive hosts. In: Smith, M., D. Warmolts, D. Thoney, and R. Hueter (eds.). The Elasmobranch Husbandry Manual: Captive Care of Sharks, Rays and their Relatives. Ohio Biological Survey, Columbus, Ohio. Pp. 325–415.
2. Borucinska, J.D., and K. Heger. Disseminated granulomas associated with nematode larvae in a shortfin mako shark. J Wildl Dis. 35: 96–100.