A research project is proposed to test the hypothesis that Culiseta melanura transmit eastern equine encephalitis (EEE) virus rapidly after brief extrinsic incubation (EI) periods of 2-3 days versus the 14 days suggested in the literature and, if already infected, transmit virus more than once during a single gonotrophic cycle by having multiple host contacts prior to each egg laying. The speed of mosquito transmission is a fundamental component of arbovirus-vector-host cycles. Anything that reduces the time required for mosquitoes to transmit an arbovirus increases the probability of disease transmission by: 1) decreasing survival time required for mosquitoes to successfully transmit virus, 2) increasing mosquito-host contacts, and 3) increasing the number of infected mosquitoes. An understanding of these dynamic events is basic to describing arboviral maintenance and amplification as well as designing multifaceted control programs. Preliminary studies and published information support our research hypothesis. EEE virus infects and disseminates rapidly in a colony strain of orally infected Cs. melanura. Saliva from these mosquitoes contains infections EEE virus after less than 3 days of EI. Field studies have shown that some Cs. melanura imbibe multiple blood meals during a single gonotrophic cycle. Recent literature suggests that infected mosquitoes are more likely to transmit virus multiple times than uninfected mosquitoes. A graphical model shows quantitatively how these events can dramatically increase the probability of successful transmission. Experiments are proposed herein to study rapid virus transmission and the frequency of multiple blood-feeding. We will examine the influences of EI time, amount of blood imbibed, virus dose, and incubation temperature on mosquito infection and ability to transmit virus. The frequency of multiple blood-feeding and its seasonal variation will be determined from field studies. After investigating rapid transmission and its natural frequency, the importance of this process for EEE virus will be clarified. This research will provide basic information that will improve our ability to minimize the occurrence of arboviral disease. The research hypothesis can be applied to a variety of other arboviral and non-viral arthropod-borne diseases.
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