A review of environmental determinants and risk factors for avian-associated mosquito arboviruses in Canada

Abstract

A number of mosquito-transmitted arboviruses which cause disease in humans have been isolated in Canada. Four in particular, West Nile, western equine encephalitis, eastern equine encephalitis and St. Louis encephalitis viruses have avian hosts and have caused epidemics and/or epizootics in parts of the United States and Canada over recent decades. However, with the exception of recently emerged West Nile virus, relatively little is known about the environmental drivers and risk factors which promote epidemic occurrence of mosquito-transmitted arboviruses in North America. This paper reviews environmental drivers and risk factors of those mosquito arboviruses with avian reservoirs which have had epidemic outbreaks in parts of the U.S.A. and Canada as a preliminary step towards future research on the effects of climate change and mosquito-borne arboviruses in Canada. The review highlights how the outcome of interactions between changing environmental conditions, with endemic or introduced invasive arboviruses, is likely to be strongly mediated by local abiotic and biotic conditions. It concludes that the processes linking abiotic and biotic determinants to virus transmission may not be generalizable. Continued research into the regional idiosyncrasies of the ecology of arboviruses will, therefore, be necessary in order to assess the effects of a changing climate on arboviruses in Canada.