Venereal transmission of St. Louis encephalitis virus by Culex quinquefasciatus males (Diptera: Culicidae).

Uninfected, virgin, colonized Culex quinquefasciatus Say females became infected when caged with males that had been infected with St. Louis encephalitis (SLE) virus by inoculation. When these females were assayed 7 or 28 d after first exposure to infected males, 23% and 25%, respectively, were infected with SLE virus. Fifty-eight percent (n = 83) of the inseminated females were infected with SLE virus, whereas only 23% (n = 23) of virgin females were infected. These data show that at least some of the horizontal transmission demonstrated was by a venereal route. This study indicates that if Cx. quinquefasciatus males were infected vertically with SLE virus in nature, they could infect their female mates horizontally.