Case report of systemic coccidiosis in a radiated tortoise (Geochelone radiata)

Abstract

More than 30 species of coccidian parasites have been described in Chelonidae (tortoises and turtles). Eimeria spp. are apparently the most common coccidia in chelonians. Findings of Caryospora cheloniae, Isospora sp., and Mantonella sp. have also been published, but reports about systemic coccidiosis are rare. We describe a case of a coccidiosis diagnosed cytologically in a radiated tortoise (Geochelone radiata) which was captive-bred in Germany. Infection was systemic and involved the lymphoid system. Intracytoplasmatic stages of parasite development were identified cytologically, histologically, and ultrastructurally. The systemic coccidiosis was associated with variable degrees of inflammation in the different organs and contributed substantially to the cause of death in this tortoise. Fragments of coccidian 18S- and 28S-rRNA from the tortoise liver were sequenced; the 18S-rRNA sequence had the highest identity to intranuclear coccidia described previously in a travancore tortoise (Intestudo forstenii) and a leopard tortoise (Geochelone pardalis). The analysis of maximum likelihood phylogenetic tree showed relation to species of the order Sarcocystidae. The biology of these coccidia and the route of infection in this case remained unclear.