Prevalence of Borrelia burgdorferi in Ixodes ricinus ticks collected from moose (Alces alces) and roe deer (Capreolus capreolus) in southern Norway.

As part of a larger survey, ears from 18 roe deer (Capreolus capreolus) and 52 moose (Alces alces) shot in the 2 southernmost counties in Norway were collected and examined for Ixodes ricinus ticks. Seventy-two adult ticks, 595 nymphs, and 267 larvae from the roe deer, and 182 adult ticks, 433 nymphs, and 70 larvae from the moose were investigated for infection with Borrelia burgdorferi sensu lato (s.l.). The results showed the presence of B. burgdorferi s.l. DNA in 2.9% of the nymphs collected from roe deer and in 4.4% of the nymphs and 6.0% of the adults collected from moose. The spirochetes were not detected in adult ticks from roe deer, or in larvae feeding on roe deer or moose. In comparison, the mean infection prevalences in questing I. ricinus collected from the same geographical area were 0.5% infection in larvae, 24.5% in nymphs, and 26.9% in adults. The most prevalent B. burgdorferi genospecies identified in ticks collected from roe deer was B. afzelii (76.5%), followed by B. garinii (17.6%), and B. burgdorferi sensu stricto (5.9%). Only B. afzelii (76.7%) and B. garinii (23.3%) were detected in ticks collected from moose. The present study indicates a lower prevalence of B. burgdorferi infection in I. ricinus ticks feeding on roe deer and moose compared to questing ticks. This is the first study to report B. burgdorferi s.l. prevalence in ticks removed from cervids in Norway.