Birds carry bacteria across the hemispheres: Migratory birds transmit borreliosis

Migrating birds transmit different forms of the Borrelia bacterium or Borrelia spirochetes to every corner of the globe. Birds are especially prone to Borrelia infected ticks during their autumn and spring migrations. The bacteria may also persist for several months in the birds and it may then be reactivated in response to migration. Borrelia spirochetes and the role of birds as global transmitters of the bacteria have been investigated by a Swedish research group led by Professor Sven Bergström. The group is part of a Finnish-Swedish research consortium included in the Microbes and Man Research Programme, which is co-funded by the Academy of Finland and the Swedish Foundation for Strategic Research.

Migratory birds play an important role in the transmission of Lyme borreliosis. The fact that the same type of Lyme disease exists in both the northern and the southern hemisphere shows that birds participate in the natural circulation of Borrelia spirochetes by carrying them all across the globe.

Previously, it was thought that only mammals could function as reservoir hosts for Borrelia infected ticks. The research results of the Bergström group show that Borrelia infected ticks can exist in birds, as well – i.e. without a mammal reservoir.

Lyme Borreliosis is an infectious disease caused by the Borrelia bacterium. It can cause eczemas, arthritis and, at the worst, even different kinds of neurological disorders. In Finland, a couple of thousand people are infected by the disease each year.

Microbes and Man Research Programme is a three-year programme during 2003-2005. With the budget of 5,4 million euros 15 projects are funded. The programme is implemented in Finnish-Swedish collaboration.