Epidemiology and Evaluation Department
July 16, 2020
Effect of climate change on invasive mosquitoes, Zika virus, and migrant worker health in Windsor and Essex County
Between 1941 and 2012, the annual average temperature for the City of Windsor increased by almost 1°C (City of Windsor, 2012). Windsor and Essex County (WEC) also experienced a 1-3% increase in rainfall per decade from 1970 to 2000 (City of Windsor, 2012), with level of precipitation and humidity expected to continue to increase in southern Canada in the coming decades (Ng et al., 2019).
One potentially dangerous effect of these climatic changes in Windsor and Essex County (WEC) is the proliferation of invasive mosquitoes. The past four years have seen the introduction of Aedes albopictus and Aedes aegypti, both carriers of the Zika virus, to WEC, and climatic changes are expected to encourage greater numbers of these mosquitoes in the coming decades (Ng et al., 2019). More specifically, rising temperatures combined with stagnant water from flooding are expected to facilitate the survival and proliferation of these species (Kovats et al., 2003). Indeed, the Aedes albopictus population in WEC (identified from trapping) increased from 17 in 2016 to 1,129 adult mosquitoes in 2018, thus demonstrating that these mosquitoes can reproduce rapidly. Furthermore, these mosquitoes spread out from one to seven different trapping locations from 2016-18.
One particular population that may be at risk for exposure to these mosquitoes are migrant farm workers. Leamington has over 8,000 migrant workers during the summer season who are housed in over 600 bunkhouses (Hennebry, McLaughlin & Preibisch, 2016). The majority of these migrant workers are from Mexico and nearby Caribbean countries, which are endemic for mosquito-borne diseases such as Zika. A recent survey in Ontario, however, found that less than a quarter of migrant farm workers saw a doctor for any health symptoms (Hennebry et al., 2016). Therefore, it is imperative that surveillance of Aedes mosquitoes and incidence of the Zika virus be increased in this area, not only to protect the health and well-being of migrants, but also the well-being of WEC as a whole.
Funding for a three-year exploratory study (2019-2022) of invasive mosquito species in Leamington, Ontario was awarded to the Windsor-Essex County Health Unit by the Public Health Agency of Canada (PHAC) via the Infectious Disease and Climate Change Fund. The primary goal of the study is increased surveillance of invasive mosquito species in Leamington, including coordination with Parks Canada for surveillance and viral testing in Point Pelee National Park. An additional objective is to assess potential risks to the Leamington community, with special attention paid to vulnerable populations, such as migrant farm workers.
Prior to mosquito surveillance (scheduled to begin May 2020), a scoping review of all literature relating to climate change, Aedes mosquitoes, the Zika virus, and migrant workers was completed. From over 65,000 reviewed records, 88 were chosen to address the specific scoping review objectives. About two-thirds (65/88) of these records were empirical studies, and 23% (20/88) were done in Canada.
Results of the review revealed extensive information on Aedes mosquitoes, the Zika virus, and climate change in the United States and other parts of the world affected by these mosquitoes. However, there are gaps in the literature regarding how Aedes mosquitoes, Zika, and climate change may affect vulnerable populations. Empirical work, such as WECHU’s current PHAC grant, that examines how Aedes mosquitoes, Zika, and climate change interact in their effect on migrant workers in Canada is greatly needed.