Evaluation of Cytauxzoon felis infection status in captive-born wild felids housed in an area endemic for the pathogen

Abstract

Objective-To determine whether apparently healthy captive-born wild felids that were not native to North America and were housed in an area endemic for Cytauxzoon felis harbored the pathogen. Design-Prospective observational case series. Animals-11 captive-born wild felids that were (1 bobcat [Lynx rufus] and 1 cougar [Puma concolor]) or were not (1 lion [Panthera leo] and 8 tigers [Panthera tigris]) native to North America and 6 domestic cats (5 pets and 1 feral). Procedures-Blood was collected, and a PCR assay for C felis was performed. The C felis 18S rRNA gene sequence was characterized in samples that tested positive. Blood smears were evaluated microscopically for intraerythrocytic organisms consistent with C felis. Blood smears from an additional 6 feral domestic cats found dead on the study premises were also evaluated. Results-4 tigers and 6 domestic cats without clinical signs of disease tested positive for C felis infection via PCR assay; intraerythrocytic organisms consistent with C felis were identified in smears from 1 C felis-infected tiger (which also had azotemia) and in smears from 11 of 12 domestic cats. Possible erythrocytic inclusions were identified in 1 tiger that tested negative for C felis. Sequences of C felis 18S rRNA amplicons from all infected tigers shared > 99.8% identity with reported C felis sequences from North American domestic cats and were identical to amplicons from domestic cats on the premises. Conclusions and Clinical Relevance-Captive tigers without clinical signs of disease tested positive for C felis. The PCR assay for C felis appeared to be more reliable than cytologic detection of piroplasms in tigers.