Anvil is an insecticide widely employed to combat West Nile Virus, a mosquito-borne disease identified in approximately 10,000 residents of the United States from 1999-2006. It is sprayed in Chicago and many other cities. Sumithrin, a synthetic pyrethroid, is the main active ingredient.
Anvil is applied aerially via fixed-wing and rotary aircraft or via ground applications (truck/ATV/backpack) using ultra-low volume (ULV) sprayers. According to the Anvil Technical Bulletin published in January 2006, these sprayers create a fine mist of drops that average 17 micrometres in size. A very small amount of active ingredient is used; about 0.6 ounces (17 g) of active ingredient is used to treat 1 acre (0.40 ha) (4.2 kg/km²).
Anvil has been tested in 43 field trials in the United States against 30 mosquito species.
Sumithrin was registered for use by the U.S. Environmental Protection Agency in 1975 and Anvil is registered for ground and aerial application in outdoor residential and recreational areas. Anvil is manufactured and distributed by Clarke Mosquito Control. 
In 2003, Anvil was used to treat more than a million acres (4,000 km²) in Larimer County, Colorado during a West Nile Virus outbreak. According to the Anvil Technical Bulletin, this application reduced mosquito populations by approximately 80 percent.
No-spray protests have called for more organic methods of preventing West Nile due to concerns about the health and environmental effects of the spray as well as recent studies showing the ineffectiveness of the spray.
- "Archived copy". Archived from the original on 2007-01-18. Retrieved 2007-03-06. Clarke Mosquito Control Anvil Page
- Garey, J; Wolff, MS (1998). "Estrogenic and antiprogestagenic activities of pyrethroid insecticides". Biochem Biophys Res Commun. 251 (3): 855–9. doi:10.1006/bbrc.1998.9569.
- Bretveld, RW; Thomas, CM; Scheepers, PT; Zielhuis, GA; Roeleveld, N (2006-05-31). "Pesticide exposure: the hormonal function of the female reproductive system disrupted?". Reprod Biol Endocrinol. 4 (30). doi:10.1186/1477-7827-4-30. PMC . PMID 16737536.