Development and evaluation of a seminested PCR for detection and differentiation of Babesia gibsoni (Asian genotype) and B. canis DNA in canine blood samples.

Canine babesiosis has recently been recognized as an emerging infectious disease of dogs in North America. We sought to develop a seminested PCR to detect and differentiate Babesia gibsoni (Asian genotype), B. canis subsp. vogeli, B. canis subsp. canis, and B. canis subsp. rossi DNA in canine blood samples. An outer primer pair was designed to amplify an approximately 340-bp fragment of the 18S rRNA genes from B. gibsoni (Asian genotype), B. canis subsp. vogeli, B. canis subsp. rossi, and B. canis subsp. canis but not mammalian DNA. Forward primers were designed that would specifically amplify a smaller fragment from each organism in a seminested PCR. The practical limit of detection was 50 organisms/ml of mock-infected EDTA anticoagulated whole blood. The primer pair also amplified an approximately 370-bp fragment of the B. gibsoni (USA/California genotype) 18S rRNA gene from the blood of an experimentally infected dog with a high percentage of parasitemia. Amplicons were not detected when DNA extracted from the blood of a dog that was naturally infected with Theileria annae at a low percentage of parasitemia was amplified. Due to limited sensitivity, this test is not recommended for the routine diagnosis of B. gibsoni (USA/California genotype) or T. annae. The PCR test did not amplify Toxoplasma gondii, Neospora caninum, Leishmania infantum, Cryptosporidium parvum, or canine DNA under any of the conditions tested. The seminested PCR test was able to detect and discriminate B. gibsoni (Asian genotype), B. canis subsp. vogeli, B. canis subsp. canis, and B. canis subsp. rossi DNA in blood samples from infected dogs.