Experts Say the Best Way to Control West Nile Virus and Mosquitoes is to Target Them in Water


LIBERTYVILLE, Ill. -- West Nile Virus (WNV) has become a serious health issue since its introduction in the United States in 1999. WNV disease is transmitted to humans, pets, birds and other animals through bites from infected mosquitoes. With more than 280 human deaths reported in 2002, many are wondering what more can be done to prevent this disease. Traditional methods to control mosquitoes use chemical insecticides sprayed into the air to kill the free-flying, adult mosquitoes.

What most people may not realize is, there is a more effective way to eliminate mosquitoes before they can transmit WNV. Larviciding, a process of treating water habitats where mosquito larvae live with biological products, is effective at reducing the number of adult mosquitoes and preventing disease. Mosquitoes require a water source for most of their lives. The adult female mosquito lays eggs in water such as ponds, storm drains and ditches, which hatch into small, wiggly larvae that complete their development in water by eating small food particles. The larvae then transform through a resting stage and emerge from the water as hungry adults, ready to bite humans and animals for a blood meal.

Experts believe that controlling larvae in the water reduces the amount of area that needs to be treated with insecticide and provides long-term mosquito control. Some larvicides are based on naturally occurring bacteria that control mosquito larvae very effectively.

Products that eliminate mosquito larvae simply do not allow the bugs to develop into adults; therefore, these products stop the spread of mosquitoes at the larval stage before they become biting adults.

Mike McGinnis, owner of a private mosquito control company called Colorado Mosquito Control, Inc., has been in this industry for 23 years. His company was founded on the idea that larviciding is the best option for eliminating the mosquito population. He uses larvicides 90 to 95 percent of the time, primarily Valent BioSciences Corporation's naturally occurring bacteria-based products VectoBac and VectoLex, which he considers to be very effective.

"In any Integrated Pest Management (IPM) program, you need to be looking toward larvicides," he said. "In Colorado, we have a lot of standing water and, therefore, mosquitoes. It's a fairly arid climate, and we don't have heavy, thick vegetation. So our larval sites are very accessible and obvious. That makes it easy for us to do larval control."

He said the most important reason to control mosquitoes at the larval stage is that it is better for the environment and safer than spray pesticides on adult pests. In fact, the New York City Department of Health and Mental Hygiene's Web site explains that, because larvicides are applied in areas where the general public does not have access, they aren't a danger. The site further emphasizes, "larvicides are not applied in areas that drain into waters consumed by humans."

In another part of the country, Dennis Wallette, director of the Tangipahoa Mosquito Abatement District in Hammond, La., said his primary focus is larviciding, as well.

"The materials are more target-specific than adulticides," said Wallette, adding that larviciding is also "the most cost-effective way of attacking the mosquito population." "The larvae are in a confined space. Plus, you're getting them before they become biting adults. Any mosquito you kill as a larva is one that won't be biting as an adult."

Wallette said this is a fairly common viewpoint in the mosquito control community.

"More organized programs that use an integrated approach would take the position that larviciding is the priority," said Wallette. "It has less of an overall impact on the environment."

Source: Valent BioSciences Corporation

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