Tick-Borne Pathogens in Ticks Feeding on Migratory Passerines in Western Part of Estonia

During southward migration in the years 2006-2009, 178 migratory passerines of 24 bird species infested with ticks were captured at bird stations in Western Estonia. In total, 249 nymphal ticks were removed and analyzed individually for the presence of Borrelia burgdorferi sensu lato (s.l.), tick-borne encephalitis virus (TBEV), and Anaplasma phagocytophilum. The majority of ticks were collected from Acrocephalus (58%), Turdus (13%), Sylvia (8%), and Parus (6%) bird species. Tick-borne pathogens were detected in nymphs removed from Acrocephalus, Turdus, and Parus bird species. TBEV of the European subtype was detected in 1 I. ricinus nymph removed from A. palustris. B. burgdorferi s.l. DNA was found in 11 ticks (4.4%) collected from Turdus and Parus species. Bird-associated B. garinii and B. valaisiana were detected in I. ricinus nymphs removed from T. merula. Rodent-associated B. afzelii was detected in 3 I. ricinus nymphs from 2 P. major birds. One of the B. afzelii-positive nymphs was infected with a mix of 2 B. afzelii strains, whereas 1 of these strains was also detected in another nymph feeding on the same great tit. The sharing of the same B. afzelii strain by 2 nymphs indicates a possible transmission of B. afzelii by co-feeding on a bird. A. phagocytophilum DNA was detected in 1 I. ricinus nymph feeding on a T. iliacus. The results of the study confirm the possible role of migratory birds in the dispersal of ticks infected with tick-borne pathogens along the southward migration route via Estonia.