Babesia Species of Domestic Cats: Molecular Characterization Has Opened Pandora's Box

This is the first comprehensive review of the literature pertaining to species reported from domestic cats. Description of the four species ( , and ) named based on morphology and/or host specificity is documented. Feline babesiosis is of major veterinary concern only in South Africa. Reports of the rare occurrence of feline babesiosis cases in Europe (France, Germany, Poland, and Spain) and Asia (Israel, India, and Pakistan) are documented. Molecular characterization has revealed that cats can harbor a variety of species. The previous practice of referring to all piroplasms, especially small ones, seen on feline blood smears as is therefore no longer tenable. The near-full-length 18S rRNA gene sequences entered into GenBank in 2001 (accession no. AF244912) are designated as definitive for sensu stricto. All published literature relating to molecular characterization of feline species that could be traced was critically assessed. Four species are now known to be involved in causing feline babesiosis in South Africa: the closely related s.s. and (clade I), (clade II), and species cat Western Cape (clade VI, s.s.). Clade VI also includes and reported from cats in Asia. Six other species have been reported from domestic cats: the dog-associated s.s., , and , as well as , and . Phylogenetic relationships of all named species were assessed and are presented as trees. The relatively high prevalence of in clinically healthy cats (16% in Brazil, 13% on St Kitts, and 8.1% in Portugal) suggests that immunocompetent cats can harbor the infection with no discernible untoward effects. Reports of occurrence of and other species in domestic cats should be accepted only if they are supported by credible molecular provenance.