West Nile virus, Vermont, and Pesticides

West Nile virus, known as WNV, is transmitted by mosquitoes. WNV first appeared in the U.S. in 1999, when at least 62 people in the New York City area developed WNV encephalitis and seven people died. After months of testing birds and mosquitoes, WNV presence was confirmed in Vermont on October 2000. A Hermit Thrush found in Putney on September 29, 2000 was the first bird in Vermont to test positive for WNV 1.

WNV presence in neighboring states and adjacent counties in New York indicate WNV has likely been present, although not detected in Vermont in both bird and mosquito populations.2 Public health officials now agree West Nile virus is probably widespread in the bird population of the eastern U.S., and that it is only a matter of time before the West Nile virus is regularly detected in Vermont.

Because mosquitoes are the vectors of WNV, massive pesticide spraying programs have been carried out in New England in the last two years. Emphasizing responsible use of larvicides to keep mosquito populations low, the State of Vermont is also planning to advise municipalities on aerial and ground spraying with synthetic pyrethroids if needed.

Although under continuous review and discussion regionally, Vermont’s current proposed triggers for initiation of pyrethroid spraying are one of the following: one confirmed human WNV clinical infection, one confirmed horse WNV clinical infection, or multiple confirmed active bird infection with corresponding localinfected mosquitoes. The spray zone originally proposed by the Arboviral Task Force was a two-mile radius circle, an area of roughly 8,700 acres, around established WNV diagnosis. This spray zone is no longer considered necessary or effective by the Center for Disease Control, and will not be used by Vermont officials in determining spray zones.

 Implementation of a spray program would be the responsibility of local municipal officials, under advisement from the Vermont Department of Agriculture. Spraying would beconducted either by truck or by aerial application.

VPIRG believes spraying thousands of acres of Vermont with synthetic pyrethroids is difficult to justify, when:
·  For most humans, WNV is a low risk disease. Most people are not aware of being infected. Death results in approximately 0.001% of infected individuals.
·  Widespread pesticide use is documented to harm sensitive ecosystems and vulnerable individuals.
·  There is already much people can do to protect themselves from mosquitoes, including using lower risk bacterial larvicides, disrupting larval habitat, and wearing protective clothing.

To ensure any pesticides used in the West Nile virus response plan are applied in a manner which will have minimal environmental and human health implications, VPIRG has proposed strict parameters be set prior to implementing a statewide mosquito control strategy.