Exchange of Borrelia burgdorferi between Ixodes persulcatus (Ixodidae:Acarina) sexual partners.

Borrelia burgdorferi sensu lato infection rate in Ixodes persulcatus Schulze maintained at different relative humidity gradients in male and females pairs, separated by sex, and in ticks of both sexes having either normal or abnormal exoskeleton were compared. Ticks were collected in the St. Petersburg Region of Russia during 1992 and 1994. We observed that the infection rate among the ticks maintained as sexual pairs was 1.75-2.00 times higher than that among ticks maintained singles, indicating a borreliae interchange between sexual partners. This pathogen interchange was thought to result from a venereal or omovampiric (cannibalistic) mode of borreliae transmission. Borrelia burgdorferi s.l. was determined to be present in 22.9% (112 infected specimens of 489 total), whereas infection occurred in 17.4% of single females and 16.5% of single males. The data indicate the importance of isolating ticks sexually during quantitative disease investigations with borreliae as well as tick-borne encephalitis virus and other tick-borne pathogens.