Genetic variability of Cytauxzoon felis from 88 infected domestic cats in Arkansas and Georgia.

Although cytauxzoonosis has historically been nearly 100% fatal in domestic cats, increasing number of reports of infected cats that demonstrate less-severe disease suggest the existence of different strains of Cytauxzoon felis. To test this hypothesis, the genetic variability of C. felis was examined in blood samples from naturally infected domestic cats from Arkansas and Georgia by using the first and second ribosomal internal transcribed spacer regions (ITS1, ITS2) as markers to assess genotypic variability. In addition, the clinical outcome of infection (survival vs. fatal disease) was analyzed. Within the C. felis ITS1 region, there were a total of 8 single nucleotide polymorphisms (SNP) and a single nucleotide insertion. Within the ITS2 region, there were a total of 4 SNPs and a single 40 base pair insertion. When taken together, the ITS1 and ITS2 sequence data defined a total of 11 different sequences and 3 unique genotypes. One unique ITS1-ITS2 genotype was detected in samples submitted exclusively from Arkansas, and a second unique genotype was submitted exclusively from Georgia. There was a significant association between infection with C. felis that contained particular ITS genotypes and survival of the infected domestic cat. The identification of unique C. felis genotypes obtained from different geographic areas and the association of particular ITS genotypes with the outcome of infection suggest the existence of parasite strains that may vary in pathogenicity to the domestic cat and offer an explanation for the survival of some infected cats in more recent case studies.