Eight Reasons Why Spraying Pesticides Is Not the Solution To West Nile Virus

How much of a risk is West Nile Virus (WNV)? To some extent, only time will tell. But public health experts stress that there is no cause for fear and panic, or for panic driven “solutions.”  In fact, the so-called “solution” of spraying pesticides to kill mosquitoes will actually lead to bigger problems. Here are eight compelling reasons why spraying pesticides is not the answer to WNV.

1. Least Effective Measure 
The US Center for Disease Control and other experts say that spraying or fogging is the least effective means for slowing the spread of WNV carrying mosquitoes.  For fogging to have maximum effect, a mosquito has to be flying. Estimates are that fogging kills only about 10% of adult mosquitoes. The  federal-provincial task force on WNV admits there is little evidence for the efficacy of insecticide spraying.  Adult mosquitoes live only about two weeks, with new larvae hatching constantly. This means that spraying cannot be a one shot operation, but needs to be repeated 
frequently if chosen as a means of control .

2.  Predators Harmed, Mosquitoes Thrive 
Aerial spraying or fogging is more harmful to mosquito predators than to mosquitoes. Since predators are farther up the food chain, they will take in higher amounts of pesticide. By decreasing mosquito predator populations, aerial spraying actually leads to increases in mosquito populations.  Data from a study in New York State published in the Journal for Mosquito Control  found that after 11 years of insecticide spraying, the mosquito population had increased 15 times. Pesticide exposure also results in immune suppression in birds, which serve as the hosts for WNV.   Birds exposed to organophosphate pesticides tend to suffer immune suppression (as do mammals, amphibians and other animals.) This makes them less able to fight off viral and bacterial infections, the very opposite of what is needed. Once infected with WNV, birds are more likely to develop symptoms and to remain ill longer than if they had not been exposed. Thus, pesticide spraying leads to more frequent and longer infections and higher viral loads in birds, making it more likely they will spread the disease to  mosquitoes. This increases the possibility of 
mosquitoes transmitting the virus to humans and other mammals.

3. Super Mosquitoes, Sicker Mosquitoes 
For some reason, as yet unknown, mosquitoes exposed to pesticides are more 
likely to have WNV in their salivary glands and develop a damaged gut lining which becomes more porous, allowing WNV to pass through. Over a decade of insecticide spraying to control encephalitis in Florida has not been effective, and mosquitoes are now 15 times more likely to pass on the disease. Mosquitoes, which have short life spans, go through many generations in a single year. The mosquitoes which  are exposed to pesticides and survive are more likely to develop resistance to them. So 
aerial spraying contributes to the development of “super mosquitoes” which can only be killed by using higher amounts or different types of pesticides.

Read more here: http://www.environmentalhealth.ca/spring03false.html