An Evaluation of the Hypothesis of Transovarial Transmission of Eastern Equine Encephalomyelitis Virus by Culiseta Melanura

Abstract

Evidence for and against the hypothesis of transovarial transmission by Culiseta melanura was obtained during an ongoing eastern equine encephalomyelitis (EEE) surveillance and control program. Evidence inconsistent with transovarial transmission included failure to isolate virus from 1,047 larvae, from 2,140 first-brood adults, or from 8,919 males collected at the same time as 3,977 nonblooded females which yielded 12 EEE isolates. Evidence supporting the hypothesis was the isolation of virus from both blooded and nonblooded adults simultaneously and also from a population with a parity rate so low that the infection rate for parous specimens would have been 1:8. Two alternative hypotheses which assume transovarial transmission are advanced to explain these results, but they seem so unlikely that the data are interpreted as opposing the concept.