Identification and genetic characterization of Cytauxzoon felis in asymptomatic domestic cats and bobcats.

The objectives of the current study were to assess the prevalence of Cytauxzoon felis infection among a population of domestic cats that were clinically healthy but at higher risk for parasite exposure and to determine if the strains present in these asymptomatically infected cats were genetically unique as compared to those present both in domestic cats that were fatally infected and in the natural reservoir host, the bobcat. Using real-time PCR analysis targeting a portion of the parasite 18S rRNA gene specific for C. felis, 27/89 (30.3%) high-risk asymptomatic domestic cats from Arkansas and Georgia, and 34/133 (25.6%) bobcats from Arkansas, Georgia and Florida, were identified as positive for C. felis infection. Conventional PCR analysis was performed on all positive samples, targeting the C. felis ribosomal internal transcribed spacer regions 1 and 2 (ITS1, ITS2) in order to utilize the ITS sequences as markers to assess the genotype variability of the parasite population. Within the asymptomatically infected domestic cat samples, 3 genetically distinct parasite populations were identified. The C. felis ITS sequences from asymptomatic cats were identical to those previously reported from clinically ill infected cats, and 2 of the 3 sequence types were also present in infected bobcat samples. While sequence diversity exists, evaluation of the ITS region does not appear to be useful to verify pathogenicity of C. felis strains within host species. However, the presence of asymptomatic C. felis infections in clinical healthy domestic cats warrants further investigation to determine if these cats can serve as a new reservoir for C. felis transmission.