Southeast Saskatchewan - Estevan in particular - has become a hotbed for the growth of the dreaded culix tarsalis mosquitoes, the species that carries the West Nile virus. The high risk period for exposure to the virus is now upon us and local efforts to reduce the mosquito populations have been stepped up considerably. However the conditions that favour the mosquitoes this year seem almost overwhelming. In a recent trapping period (July 11 to 16) Estevan showed a huge average population of 550.3 mosquitoes per night in the trap compared with just 37.3 per night in Weyburn, and 31.8 per night in Moose Jaw, and 26.8 per night in Maple Creek and slightly lower in Swift Current. Some individual traps are snaring as many as 790 mosquitoes per night. Of the mosquitoes being trapped, nearly 53 per cent are of the culix tarsalis breed, which are now into their second generation this summer. Their numbers will only increase as the number of nuisance mosquitoes subsides. Warmer temperatures and a high volume of local standing water make local areas perfect breeding grounds. Larry Doan of South East Tree Care, the company that has been charged with the job of laying down larvicides to try to combat the culix tarsalis and other mosquito breeds, said the effort being put into the program this year in the Energy City is substantial. He said they have increased their larvacide program by at least 30 per cent in terms of larvacide volumes and hours spent on the effort. "Everything was saturated, even in areas you'd never expect it," said Doan, noting that in many instances the larvacide had to be carried into the pools of water by people on foot since the all terrain vehicles couldn't get into the core sectors. "We're spending about 245 person hours per week on the larvacide program. That's a lot, and that was in June and well into July. We've experienced some drying conditions this month but it's still very difficult getting to some areas. It's been hard on the equipment and the people. We know we're up against it, but we're trying as best we can to keep the population in check, knowing that even in the best of times, you only get 30 to 40 per cent," Doan said. Those doing the larvacide work have been receiving full co-operation from the City of Estevan's leisure services department who are monitoring the effort and seeing that the program receives the funding necessary to carry out an effective fight. "The City is very good at allowing us to put the plan together each year and we have continuing good communication with them. They're letting us try new products this year, too, and they are effective. We know that from the dead larva count we make on the follow-up visits," Doan added. The company divides the city into five parts and then attacks each area on a rotation throughout the week, hitting an area, somewhere in the city, every day, Monday through Friday."But it's a large larva population and it's still going up," said Doan, noting that he was very aware of the statements coming from the local health region and province telling people that the next two weeks will be critical in terms of assessing the West Nile virus risk. "It's critical in terms of assessing West Nile for the rest of the season," said Phil Curry, the West Nile virus co-ordinator. "We will continue to monitor mosquito activity throughout the summer and notify media and public about the risk and personal protective measures." The latest report for Saskatchewan noted there has been no positive mosquito pools as yet, meaning no mosquitoes caught in traps that have been infected with West Nile. There have been only two positive pools found in Manitoba to date. Single human cases have been reported in North and South Dakota though, and 10 total human cases in the United States this summer. But with the conditions being optimal for culix tarsalis, the risk levels in the Sun Country Health Region have been raised to moderate from low. Officials now warn that we could start to see some West Nile activity in birds, possibly resulting in human exposure and reported cases soon enough. If warm weather continues, accompanied by more moisture, the incubation period for the third generation of culix tarsalis will be shortened and they will be out and flying around in a shorter period of time, thus infecting more birds and people. "We're seeing some success in fighting the problem, but it's difficult," said Doan. "This has been an ideal year for mosquitoes, so in a normal year, if we kill 40 per cent of 100, then we can make it easier for people, but when you get 40 per cent of 10,000, well, that leaves a lot of mosquitoes still out there doing damage." Doan said that mosquito control teams not only visit well known breeding grounds for the mosquitoes, but have added several more areas in the city that have become breeding areas only this year thanks to the larger and more numerous water catchment areas caused by the heavy rains.
