August 9, 2006

York Region reports first positive West Nile virus mosquitoes


NEWMARKET York Region Health Services reports that a mosquito pool has tested positive for West Nile virus (WNV). A “pool” defines one batch of mosquitoes caught overnight in one trap and sent for testing.


The mosquitoes were trapped in the Township of King, close to the intersection of Highway #9 and Highway #27. The positive mosquitoes are the first this year in York Region.  On-going treatment of the catch basins in this area will continue as well as the necessary treatment of surrounding stagnant water (i.e., roadside ditches) on public property. Surveillance for the virus will also be increased in this area.


There were 14 positive mosquito pools reported last year in York Region.  To date in 2006, there have been no reported positive cases of bird or human WNV in York Region.


Trapping mosquitoes is part of the 2006 York Region WNV control plan. Traps are set up at various locations throughout the Region, with mosquitoes sent for testing.


Like humans, WNV is transmitted to the bird population by infected mosquitoes. Crows, blue jays and other raptor species are known to be most susceptible to the disease and act as early warning signs for the presence of the virus in a particular area.


Report dead crows and blue jays. York Region Health Services requests that residents report sightings of dead crows and blue jays through the Health Connection information line. Suitable specimens may be collected and submitted to the Canadian Co-operative Wildlife Health Centre in Guelph for testing. All crows and blue jays that are reported will help to map out possible WNV activity in York Region.


Dead bird pick-up service is available. Most dead birds will not be suitable for testing, but knowing what species they are and where they died is important information. Do not handle birds with bare hands or dispose of dead birds through the municipal garbage systems. Please contact Health Connection for pickup of dead birds of any species.


The symptoms for WNV illness consist of fever, muscle weakness, stiff neck, confusion, severe headache, and a sudden sensitivity to light. For a very rare few, the virus causes serious neurological illness including encephalitis (inflammation of the brain). Those experiencing symptoms should seek medical advice.


Prevention and protection are the best ways to protect yourself and your family from WNV. There are simple and common sense precautions that should be taken:


·        Minimize outdoor activities where and when mosquitoes are most active such as dusk, night and dawn

·        Wear protective clothing such as long sleeved shirts, full-length trousers, socks, light coloured clothing and tuck pant legs into socks when possible.

·        Consider using an insect repellent, as directed

·        Make sure screens on your home are tight-fitting and in good repair

·        Mosquitoes breed in still water. Eliminate stagnant water around your property which may gather in pool covers, flower pots, children’s pools, old tires and birdbaths


The York Region WNV control plan for 2006 includes:


·        Mosquito, bird and human surveillance


·        WNV control activities, including a larviciding strategy:

- The strategy includes four larvicide applications (in June, July, August and September). Two larvicide applications have now been completed. These applications target all catch basins along Regional and Municipal Roads and in catch basins, as required, on private property


- Methoprene is the larvicide that is used. It comes in a slow-release pellet-like formulation and is administered in catch basins when the mosquito is in the larval stage of development. It interferes with the mosquito life cycle, preventing the mosquito larva from reaching maturity. It is not sprayed. It has been approved by both the provincial and federal governments and is considered low risk for humans, pets and the environment when it is applied according to label directions


·        The WNV control plan also includes public education regarding common sense and effective measures to prevent exposure to WNV


To report a dead crow or blue jay and for more information on WNV or any health-related concern, contact York Region Health Services Health Connection at 1-800-361-5653 or visit


To review the current status of WNV in Ontario, visit

For more information on the Regional Municipality of York and our services, please visit


Media Contact:         Jennifer Mitchell-Emmerson, York Region Health Services

                                 Phone:  (905) 830-4444, ext. 4016 or After-hours Pager (905) 830-3302


Back to top