Prevalence and distribution of Anaplasma phagocytophilum in ticks collected from dogs in the United Kingdom.

Background: Anaplasma phagocytophilum is the etiological agent of canine granulocytic anaplasmosis in dogs and causes human granulocytic anaplasmosis (HGA). Tick-borne anaplasmosis has been recognised as an emerging zoonotic health concern worldwide. The aim of the present study was to determine the prevalence of A. phagocytophilum in ticks collected from dogs in the UK and map its distribution. Routine surveillance of tick-borne disease is essential as part of a "One Health" approach to infectious disease management.

Methods: Tick DNA samples collected in 2015 as part of a large-scale tick surveillance programme were analysed using a previously validated diagnostic quantitative PCR for A. phagocytophilum.

Results: PCR analysis indicated that 138 out of 2994 tick DNA samples analysed were positive for A. phagocytophilum, a prevalence of 4.6% (95% CI: 3.89-5.42). Among these 138 tick DNA samples, 131 were from Ixodes ricinus, six were from Ixodes hexagonus and one was from Ixodes canisuga. Three of the I. ricinus tick DNA samples positive for A. phagocytophilum DNA were also positive for Borrelia spp. DNA and one was positive for Babesia spp. DNA, indicating co-infection. The ticks positive for the pathogen DNA were found widely distributed throughout the UK.

Conclusions: These data provide important information on the prevalence and wide distribution of A. phagocytophilum in ticks infesting dogs within the UK.