NONVASCULAR DELIVERY OF ST-LOUIS ENCEPHALITIS AND VENEZUELAN EQUINE ENCEPHALITIS VIRUSES BY INFECTED MOSQUITOS (DIPTERA, CULICIDAE) FEEDINGON A VERTEBRATE HOST27

We determined whether mosquitoes infected with the viruses St. Louis e ncephalitis (SLE) or Venezuelan equine encephalitis inoculate virus ex travascularly or directly into the vascular system. Infected mosquitoe s fed on the distal 3rd of the tails of suckling mice. Significantly m ore mice whose tails were amputated at the midpoint within 10 min of m osquito feeding survived than did siblings whose tails remained intact . Even when tails were amputated 1-6 h after SLE virus-infected mosqui toes fed, the median time to death was significantly longer in mice wi th amputated tails (7.1 d) than in mice with intact tails (5.8 d). We concluded that mosquitoes inoculated virus primarily extravascularly, rather than directly into the vascular system, while feeding on a vert ebrate host. Extravascular, rather than intravascular, delivery of pat hogens by mosquitoes may affect disease pathogenesis and vaccine effic acy.