Highly variable year-to-year prevalence of Anaplasma phagocytophilum in Ixodes ricinus ticks in northeastern Poland: a 4-year follow-up.

Anaplasma phagocytophilum is transmitted mainly by Ixodes ricinus ticks in Europe. We followed-up A. phagocytophilum infection rate in I. ricinus in three selected collection sites in northeastern Poland during a four-year period. Overall infection rate was 14.1% (208/1474) with highest infection rate among females (36.8% verses males 8.2% and nymphs 0.9%). We noted a very big year-to-year variation of infection prevalence in each collection cite every year reflecting changeable granulocytic anaplasmosis risk for humans and animals.