Babesia microti in rodents and raccoons from northeast Florida.

Human babesiosis in the United States is caused most commonly by the intraerythrocytic protozoan parasite, Babesia microti . Although a few reports have described evidence of Babesia species in animals in Florida, to date Babesia microti specifically has not been reported from Florida or most other southern states. To determine if the organism is present in vertebrates in the region, small mammals were trapped and sampled at 2 sites in northeastern Florida, and DNA extracts from blood samples were screened for B. microti DNA via PCR assays targeting portions of the nuclear small subunit rRNA (18S rDNA) and beta-tubulin genes. Amplified fragments from representative samples of PCR-positive hosts were sequenced and compared phylogenetically to reference strains of Babesia species. The B. microti strains found in cotton rats ( Sigmodon hispidus ) most closely resembles B. microti sensu stricto strains that are pathogenic to humans, and strains found in raccoons ( Procyon lotor ) most closely resembles previously described raccoon-related strains of B. microti sensu lato. The results of this study suggest that B. microti is prevalent among cotton rats and raccoons at some sites in northeast Florida and may pose a risk to humans in the region.