Two species of canine Babesia in Australia: detection and characterization by PCR.

The haemoprotozoan Babesia canis has been recognized in Australia for many years, and a second, smaller species has recently been discovered. Amplification and sequencing of a partial region of the 18S small subunit ribosomal RNA (rRNA) gene enabled detection and characterization of the large and small canine babesiae of Australia for the first time. Isolates from northern Australia were genetically characterized to be 99% homologous to Babesia canis vogeli, confirming previous speculation about the subspecies of B. canis endemic to Australia. The partial 18S rRNA gene sequence amplified from isolates obtained in southeastern Australia was genetically identical to Babesia gibsoni, a species not previously known in Australia. The polymerase chain reaction (PCR) used was shown to be specific to Babesia and had a high sensitivity, detecting DNA at a parasitemia of approximately 0.0000027%. This study also reports the first known detection and characterization of B. canis DNA in Rhipicephalus sanguineus ticks using PCR.