Venereal transmission of La Crosse virus from male to female Aedes triseriatus.

Horizontal transmission of La Crosse (LAC) arbovirus in colonized Aedes triseriatus was first observed in mating cages. LAC antigen was visualized by fluorescent antibody technique in multiple organs of 5 (2.5% of 198 females dissected after contact in mating cages with males, with a transovarial infection rate of 31%. Venereal transmission of LAC virus was demonstrated by limited contact induced mating. Antigen was detected in bursal contents of 35 (53%) of 66 females dissected within 24 h after induced mating by males previously infected by intrathoracic inoculation. Antigen was observed in ovaries, heart, gut, salivary glands, or other organs in 13 (3.4%) of 379 females dissected 1 to 14 days post-mating. LAC virus was isolated from infected males, from contents of the bursa copulatrix of females following mating, and from dissection remnants of 6 of the 13 females in which disseminated antigen had been observed. Venereally infected females were shown to be capable of transmission of LAC virus by bite to mice and to eggs.