Murray Valley encephalitis: a survey of suspected mosquito vectors.

Abstract

SummaryA survey of the mosquitoes of a section of the Murray River Valley of Australia has provided data of value to epidemiologic investigators of Murray Valley encephalitis and to persons possibly concerned with mosquito problems in this area.In these studies, 16 species of mosquitoes are recorded. Laboratory tests for Murray Valley encephalitis virus on 17,833 mosquitoes representing 10 species have been negative. Several other types of virus, an unclassified pox virus and myxomatosis virus, were isolated from mosquitoes collected.Interpretation of data on the biology of adult mosquitoes permits some evaluation of the relative potential importance of the various species as vectors of Murray Valley encephalitis. It is concluded that certain species should be suspected as vectors, in the following order of importance: Culex annulirostris, Culex fatigans “complex,” Mansonia linealis, Aedes theobaldi and possibly Anopheles annulipes. As no epidemiologic evidence could be found that the virus was still present in the area studied, the negative findings neither prove nor disprove that mosquitoes are vectors of this virus, and further studies are warranted.A sample of 71 larval collections has been analyzed as to larval habitats, association of various species, the conditions of water source and use leading to mosquito breeding and possible control problems. It is suggested that an effective program for mosquito control would require modification of existing irrigation facilities and practices, as well as an attack on natural and purely domestic water sources of mosquitoes.