Intravascular Ciliated Protozoa: An Important Cause of Mortality in Captive Reared Kihansi Spray Toads (Nectophrynoides asperginis)
1Northwest ZooPath, Monroe, WA, USA; 2The Toledo Zoo, Toledo, OH, USA; 3Buffalo Zoo, Buffalo, NY, USA; 4Detroit Zoo, Royal Oak, MI, USA; 5Dept of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA, USA; 6Department of Herpetology, Wildlife Conservation Society-Bronx Zoo, Bronx, New York, USA; 7Electron Microscopy Laboratory, California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA
Ciliated protozoan infections of the alimentary tract are common in amphibians and considered nonpathogenic.4 Ciliates can also be found on the skin and gills of aquatic amphibians, but rarely cause disease.1,5 Intravascular or visceral forms of pathologic ciliated protozoan infection have not been documented in amphibians. The Kihansi spray toad (Nectophrynoides asperginis) (KST) is a recently discovered and highly endangered species with a range limited to a single spray zone created by a waterfall along the Kihanzi river in the Udzungwa Mountains, Tanzania.3 Habitat destruction by a recently installed hydroelectric plant, and possibly chytridiomycosis, has completely decimated the wild population. Shortly after discovery of this species, 500 individuals were collected by members of the Wildlife Conservation Society and dispersed to captive breeding programs in several U.S. zoos. More recently the extant captive populations have been consolidated to two facilities, The Toledo Zoo and the Wildlife Conservation Society, to optimize breeding potential. There has been some success in the breeding programs, although progress has been impeded by husbandry problems and infectious disease, particularly a novel form of intravascular ciliated protozoan infection, detected at two of the breeding facilities.2 This report describes the pathologic findings associated with this condition.
Northwest ZooPath has 67 KSTs on file from three different institutions, (Detroit, Toledo and Buffalo Zoos), and 20 of these toads (30%) were diagnosed with fatal intravascular ciliated protozoan infections. Nineteen were from the Toledo Zoo, one was from the Buffalo Zoo and none were from the Detroit Zoo. Twelve affected toads were females, seven were males and sex was not determined for one. All toads had large numbers of intravascular ciliates in all viscera.
Lesions associated with this condition were hepatic sinusoidal obstruction and hepatitis, glomerular capillary obstruction, and lymphatic obstruction and lymphangiectasia with regional edema and cellulitis of the legs and face. The source of the infection was believed to be skin, although ulceration was not commonly seen. Ultrastructural, immunohistochemical and molecular studies are currently being conducted to determine the identity of the ciliate. Husbandry conditions are being modified in an effort to limit the occurrence and spread of this infectious disease.
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