Steve Whyard - Battling Mosquitoes and the West Nile Virus

posted 4 June 2010

article in The Bulletin: 4 Sept 2008

Manitobans are well acquainted with female mosquitoes, both as pests and carriers of the West Nile Virus; male mosquitoes do not bite, but actually feed on plant nectar. Steve Whyard, Biological Sciences, is working on ways to address the insect problem through mosquito population control, and through new treatments for the “patients” – both the people patients and the mosquito patients.

Mosquito Population Control

One common method of controlling the mosquito population is through the use of pesticides, including fogging. The unfortunate consequences of regular pesticide use are that mosquito populations gradually become resistant to pesticides, and the pesticides can poison many additional species. Whyard’s lab is pursuing other approaches.

One of these is the sterile insect technique. The essential step is to release large numbers of sterile, but otherwise healthy, male mosquitoes into an area. If there are sufficient numbers of these sterile males, then most females will breed with them, and consequently not produce any young. Typically, the males are sterilized by radiation, but this weakens them and renders the approach ineffective, because the females breed with the naturally occurring fertile males instead, and go on to produce many healthy, hungry offspring. Whyard’s group is working on an alternative – to use genetic engineering to produce sterile males and breed them in captivity.

In another approach, Whyard’s lab is developing materials, known as “gene-silencing” molecules, which specifically attack mosquitoes’ genes that are essential for the mosquitoes’ development. By feeding these materials to mosquito larvae, the larvae are killed before they can develop into biting adults. By selectively targeting only the right genes, it will be possible to make pesticides that kill only the mosquitoes, without adversely affecting any other species, or only a few others. This will be a great improvement over current pesticides. This general approach of developing species-specific pesticides should also be applicable to many other noxious insect pests.

Treatment

In a third aspect of his research, Whyard is examining how the West Nile virus infects different species, with the aim of developing new therapeutic agents that can suppress viral infection in either humans, the mosquitoes, or both. By examining how the virus hijacks the cellular proteins of its different hosts, the researchers are identifying key molecules that the virus needs to replicate. By blocking how the virus affects host cells, it is possible to prevent the virus from infecting different hosts, like birds and mosquitoes, and thereby, stop the infection cycle. Whyard anticipates that this work could be useful in developing treatments against other serious insect-borne diseases such as dengue virus and malaria.

Quick Mosquito Facts:

Only the female mosquito blood feeds - she uses the blood to nourish eggs; some species can produce eggs without blood meals; but the majority are obligate blood-feeders.

Mosquito development is dependent on availability of water, but it also depends on temperature - the warmer it is, the faster they develop into adults.
The majority of mosquitoes get consumed during the larval and pupal stages by other aquatic species - the adults you see represent only a small fraction of the population.
Mosquitoes transmit disease to about 700 million people each year. It is the older females that are responsible for this disease transmission, and they first have to acquire an infected blood-meal, let the pathogen proliferate for severay days to a week and then bite again!