RISK OF URBAN LYME-DISEASE ENHANCED BY THE PRESENCE OF RATS

To determine whether Norway rats contribute to the risk of human Lyme disease in a central European city park, densities of endemic rodents were compared as were feeding densities of vector ticks and prevalence of infection by the Lyme disease spirochete, Only Norway rats and yel low-necked mice were abundant, and three limes as many mice as rats we re present. More larval ticks fed on rats than on mice, and far more n ymphs engorged on the rats, All rats but only about half of the mice i nfected ticks, Each rat was more infectious than each infectious mouse . infected rats were distributed throughout the city, Spirochetes infe cted about a quarter of the questing nymphal ticks. The capacity of ra ts to serve as reservoir hosts for the Lyme disease spirochete, theref ore, increases risk of infection among visitors to this and other urba n parks.