Comparison of three methods for determining transmission rates in vector competence studies with Culex univittatus and West Nile and Sindbis viruses.

Culex univittatus mosquitoes were infected by ingesting West Nile and Sindbis viruses, respectively. After 13-19 days, comparative viral transmission rates were determined using 3 methods: 1) transmission to hamsters by bite, 2) in vitro transmission while feeding on suspensions in capillary tubes and 3) transmission while feeding on droplets of suspension. Transmission rates were 59-100%, except for Sindbis virus by droplet feeding when the rate was 9%. Except for the latter, rates determined by the different methods were very similar in the case of each virus. It was concluded that capillary feeding is an acceptable alternative to feeding on hamsters for determining transmission rates for Cx. univittatus with West Nile and Sindbis viruses.