Rapid High-Resolution Melt Analysis of Cytauxzoon felis Cytochrome b To Aid in the Prognosis of Cytauxzoonosis.

Cytauxzoon felis is a virulent, tick-transmitted, protozoan parasite that infects felines. Cytauxzoonosis was previously thought to be uniformly fatal in domestic cats. Treatment combining atovaquone and azithromycin (A&A) has been associated with survival rates of over 60%. Atovaquone, a ubiquinone analogue, targets C. felis cytochrome b (cytb), of which 30 unique genotypes have been identified. The C. felis cytb genotype cytb1 is associated with increased survival rates in cats treated with A&A. The purpose of this study was to design a PCR panel that could distinguish C. felis cytb1 from other cytochrome b genotypes. Primer pairs were designed to span five different nucleotide positions at which single-nucleotide polymorphisms in the C. felis cytb gene had been identified. Through the use of high-resolution melt analysis, this panel was predicted to distinguish cytb1 from other cytb genotypes. Assays were validated using samples from 69 cats with cytauxzoonosis for which the C. felis cytb genotypes had been characterized previously. The PCR panel identified C. felis cytb1 with 100% sensitivity and 98.2% specificity. High-resolution melt analysis can rapidly provide prognostic information for clients considering A&A treatment in cats with cytauxzoonosis.