Genetic variability of archived Cytauxzoon felis histologic specimens from domestic cats in Georgia, 1995-2007.

Cytauxzoon felis infection in domestic cats has historically been nearly 100% fatal. However, increasing reports of domestic cats that survive cytauxzoonosis and reports of asymptomatic cats with C. felis infections suggest the existence of different parasite strains that vary in pathogenicity. The objective of the current study was to obtain epidemiologic information about cytauxzoonosis through genotypic characterization of archived histologic specimens from domestic cats with C. felis infections that were diagnosed in Georgia between 1995 and 2007. Such retrospective data on genetic variability will provide an historic context for current studies of C. felis genotype frequencies. Cytauxzoon felis DNA was obtained from formalin-fixed, paraffin-embedded tissues from infected cats diagnosed with cytauxzoonosis at necropsy. Genetic characterization of C. felis was performed using sequence analysis of the polymerase chain reaction-amplified ribosomal internal transcribed spacer regions 1 and 2 (ITS1, ITS2). Eleven different combined ITS1 and ITS2 sequences were identified, the majority of which were identical to those previously reported in fatally infected cats from Georgia. The findings of the current study document the existence of genetically distinct C. felis populations in historical samples and, together with data from contemporary samples, demonstrate a diverse population structure for C. felis.