Detection of Anaplasma platys in dogs and Rhipicephalus sanguineus group ticks by a quantitative real-time PCR

Anaplasma platys is an obligate intracellular, tick-borne pathogen of dogs, which causes canine infectious cyclic thrombocytopenia (CICT). The vector role of Rhipicephalus sanguineus group ticks has been only suggested, but definitive evidence is lacking. This study aimed to detect and quantify A. platys DNA in infected dogs and in their respective ticks through a quantitative real-time PCR assay. From March to May 2009, blood and tick samples from dogs residing in a CICT-endemic area were collected and molecularly analysed. Differences (p < 0.05) were detected in the bacterial load between tick nymphs (3.5 × 10−2 ± 2.5 × 10−2) and adults (female: 1.2 × 10−1 ± 1.1 × 10−1; male: 9.3 × 10−2 ± 1.2 × 10−2) and between unengorged (1.1 × 10−1 ± 2.8 × 10−2) and partially or fully engorged ticks (1.9 × 10−1 ± 2.7 × 10−2). No difference was found between ticks collected from positive (1.1 × 10−1 ± 0.6 × 10−1) and negative (1.2 × 10−1 ± 0.3 × 10−1) dogs (p > 0.05). The mean bacterial load detected in positive dogs was lower than that in their respective ticks (p > 0.05). This study provides circumstantial evidence of the putative role of Rhipicephalus sp. I as a vector of this pathogen.