Abstract
The Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba have generally reported the highest human incidence of West Nile virus (WNV) in Canada. In this study, environmental and biotic factors were used to predict numbers of Culex tarsalis Coquillett, which is the primary mosquito vector of WNV in this region, and prevalence of WNV infection in Cx. tarsalis in the Canadian prairies. The results showed that higher mean temperature and elevated time lagged mean temperature were associated with increased numbers of Cx. tarsalis and higher WNV infection rates. However, increasing precipitation was associated with higher abundance of Cx. tarsalis and lower WNV infection rate. In addition, this study found that increased temperature fluctuation and wetland land cover were associated with decreased infection rate in the Cx. tarsalis population. The resulting monthly models can be used to inform public health interventions by improving the predictions of population abundance of Cx. tarsalis and the transmission intensity of WNV in the Canadian prairies. Furthermore, these models can also be used to examine the potential effects of climate change on the vector population abundance and the distribution of WNV.
Highlights
Since the introduction of West Nile virus (WNV) into eastern North America in 1999 [1], WNV has become an endemic disease in the most of southern Canada, especially in the Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba, which have had the highest human infection rate in Canada
In the final WNV infection rate model, we found that increasing Cx. tarsalis abundance, and month lagged temperature were associated with increased WNV infection rate, while one month lagged mean precipitation, 3 months total precipitation, and water land cover were inverse associated with infection rate (Table 3)
The variables associated significantly with WNV infection rate in this study were similar to the weekly model; on the monthly time scale, we found an inverse relationship between mean degree days and WNV infection rate when time lagged temperature was controlled
Summary
Since the introduction of West Nile virus (WNV) into eastern North America in 1999 [1], WNV has become an endemic disease in the most of southern Canada, especially in the Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba, which have had the highest human infection rate in Canada. Of the 2,315 cases in Canada in 2007, more than 98% occurred in these three prairie provinces [2]. Saskatchewan alone accounted for over half the human cases reported in Canada. West Nile Virus is primarily transmitted and amplified among local avian fauna and ornithophilic mosquito vectors, with occasional spillover into mammalian populations through mosquito blood feeding [3,4,5,6]. Surveillance of mosquito infection rate provides sufficient lead time for intervention and management of mosquito borne diseases [7,9]
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