Lyme disease 2000. Emerging zoonoses complicate patient work-up and treatment.

Lyme disease and other tick-borne diseases affect all age groups, including active persons age 50 and older. There has been a steady expansion in case numbers and the geographic borders of Lyme disease over the last two decades. Better recognition of two emerging tick-borne zoonoses (babesiosis and human granulocytic ehrlichiosis) that can be co-transmitted with Lyme disease is changing the approach to diagnosis and treatment of Lyme disease. Advances from genetic cloning have improved our understanding of the immune mechanisms associated with treatment-resistant Lyme arthritis and enabled the development of the first Lyme disease vaccine. The available vaccine is less efficacious in persons age 65 and older than in younger adults, but it may be a useful adjunct to other preventive measures in areas endemic for Lyme disease.