Virus-Vector-Host Relationships of Aedes stimulans and Jamestown Canyon Virus in a Northern Indiana Enzootic Focus

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Abstract
Collections of hematophagous Diptera at the Kingsbury State Fish and Wildlife Area in northern Indiana between 1982 and 1984 yielded 118,972 mosquitoes from which 5 isolates of Jamestown Canyon virus and 3 isolates of trivittatus virus were obtained. All Jamestown Canyon isolates were from Aedes stimulans, including 1 from a pool of newly emerged males and 2 from pools of newly emerged females. These 3 isolates suggest that Jamestown Canyon virus is transovarially transmitted by Ae. stimulans. All isolates of trivittatus virus came from pools of Ae. trivittatus. No isolates were obtained from >4,000 tabanids collected along with the mosquitoes those years. Transmission trials with field-collected newly emerged adult female Ae. stimulans demonstrated a mean midgut infection rate of 44%, a disseminated infection rate of 16%, and an oral transmission rate of 12% to suckling mice. Precipitin tests of field-collected bloodfed female mosquitoes indicated that white-tailed deer were the preferred host for numerous mosquito species including Ae. stimulans. The results of this study suggest that Ae. stimulans is a primary vector of Jamestown Canyon virus and that transovarial transmission is the probable overwintering mechanism for this California group virus.