Mosquitoes and West Nile Virus
Ability of different mosquito species to acquire and transmit WNV is highly variable
Mosquitoes are critical for the transmission of WNV from birds to humans and horses
In North America, large number of Culex species are involved in WNV transmission
WNV is transmited when mosquito injects infected saliva into host
Primary vector for WVN in the prairie provinces of Manitoba, Saskatchewan, and Alberta is Culex tarsalis
Cx. tarsalis is one of the most competent WVN vectors evaluated to date in laboratory studies
Cx. tarsalis has been found as far north as the southern boundary of the boreal forest transition zone
Grassland and agriculture area is the preferred area of distribution of Cx. tarsalis in Western North America and other regions of the Great Plains
Cx. tarsalis, as well as many other mosquitoe species, lay eggs in stagnant water bodies with high organic content, such as artifical containers, water-filled hoof prints, and weedy roadside ditches
Factors that facilitate transmission of WNV in Cx. tarsali:
Note: Cx. tarsalis is also the primary vector for St. Louis and Western Equine Encephalitis viruses in North America
Many factors contribute to the spatial and temporal distribution of vectors and vector-borne disease
Climate conditions such as temperature and precipitation influence:
- Can vertically transmit WNV to its offspring during winter when female mosquitoes are in diapause (overwintering of WNV), and then transmit horizontally during the summer
- Produce multiple generations per season
- Take multiple blood meals during each generation
Purpose of targeted surveillance for virus within mosquito population is to detect virus prior to outbreaks in humans and horses, and to establish a base-line of mosquito-born activity so we can monitor changes in their population over time
- Reproduction, development and survival of vectors, which in turn influence distribution and abundance of vectors
- Blood seeking activity
- Rates of pathogen amplification through development, multiplication and survival within vectors
- Particulary useful for vector control, introduction of biosecurity measures for livestock or initiate preventative vaccination
Note: WNV has also been detected in ticks!
Engler, O., et al. (2013) European Surveillance for West Nile Virus in Mosquito Populations. Int. J. Environ. Res. Public Health. 10:4869-95.
Chen, CC., et al. (2013) Climate Change and West Nile Virus in a Highly Endemic Region of North America. Int. J. Environ. Res. Public Health. 10:3052-71.
Nelms, BM., et al. (2013) Overwintering Biology of Culex (Diptera: Culicidae) Mosquitoes in the Sacramento Valley of California. J. Med. Entomol.. 50(4):773-90.