Migrating Birds at Ottenby Sweden as Carriers of Ticks and Possible Transmitters of Tick-Borne Encephalitis Virus

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Abstract
Investigations of birds trapped at the Ottenby Bird Station on the island of Oland in the Baltic Sea demonstrated that ticks are carried by numerous bird species, particularly Passeriformes. The resident bird population as well as birds undertaking migration were found to be infested. Among birds undertaking long-range migration, infestation was made probable only for individuals coming in from the south in spring. The tick species most commonly encountered was Isodes ricinua. while I. arboricola and Hyalomma marginatum were occasionally represented, the last mentioned in but a single case. Infestation rates during autumn migration were: in early Aug., 0% (62 birds of 7 species examined), in Sept. 8.8% (136 birds of 14 species), and in Oct. 5.4% (93 birds of 11 species). In most cases only one or a few ticks were taken off each bird. Only larval and nymphal ticks were encountered, except 1 female of I. arboricola. Examination of blood samples to demonstrate presence of tick-borne encephalitis virus was negative and only one of 291 serum samples collected from a Gorden Warbler (Sylvia borln), neutralized this type of virus.