Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in Ixodes ricinus ticks in Brønnøysund in northern Norway

Abstract

Ticks are important vectors of disease for both humans and animals. In Europe, Lyme borreliosis is the most abundant tick-borne human disease, whereas anaplasmosis, or tick-borne fever, is the most widespread tick-borne infection in domestic animals. However, knowledge about the prevalence of the causative disease agents in questing ticks in the northern range of their distribution in Norway is missing. Ixodes ricinus ticks were therefore collected by flagging vegetation in Brønnøysund, an area near the Arctic Circle in Norway where ticks have been abundant for decades. Ticks were analysed for infection with Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum by real-time PCR amplification of the 16S rRNA gene of B. burgdorferi and the msp2 gene of A. phagocytophilum. B. burgdorferi s.l. were subsequently genotyped by conducting a melt curve analysis of the PCR-amplified hbb gene or by directly sequencing the PCR-amplified rrs (16S)-rrl (23S) intergenetic spacer. A. phagocytophilum was genotyped by msp2 gene sequencing. B. burgdorferi s.l. isolates were detected in 11.3% (15/133) of the nymphal ticks and in 33.3% (29/87) of the adult ticks. Of the 44 Borrelia-infected ticks collected, B. afzelii was identified in 42 ticks (95.5%), whereas B. garinii was detected in only 2 ticks (4.5%). A. phagocytophilum was detected in 0.8% of nymphal ticks (1/133) and in 4.6% of adult ticks (4/87). Mixed infections of more than one B. burgdorferi genospecies were not observed. One adult tick was co-infected with B. afzelii and A. phagocytophilum.