Prevalence and first molecular characterization of Anaplasma phagocytophilum, the agent of human granulocytic anaplasmosis, in Rhipicephalus sanguineus ticks attached to dogs from Egypt

PCR targeting 16S rRNA gene integrated with sequence analysis were performed to investigate the prevalence and the molecular identity of Anaplasma phagocytophilum in Egyptian Rhipicephalus sanguineus ticks attached to dogs. A total of 413 adult and nymphal R. sanguineus ticks were collected while attached to 72 free-roaming dogs from four locations (Imbaba, Boulaq, Haram, Monib) in Giza Governorate, Egypt. DNA was successfully extracted from 401 specimens (133 nymphs and 268 adults). The overall prevalence rate was 13.7% and adult ticks showed a significantly higher infection rate (16.4%) compared to nymphs (8.3%). Sequence comparisons of 218-bp showed that detected organism belongs to A. phagocytophilum. The sequence showed 99.1% similarity (2 nucleotide differences) with some strains described as human pathogens and with that detected in the established tick vectors. Phylogenetic analysis placed the bacteria on a separate branch with that found in R. annulatus from Egypt (DQ379972) (99.5% similarity). Our variant strain was designated as A. phagocytophilum-Ghafar-EGY (AB608266). This report is the first molecular characterization of A. phagocytophilum in R. sanguineus in Egypt, suggesting that this tick species may act as a competent vector for a variant strain of human granulocytic anaplasmosis agent.