The New York City Department of Health and Mental Hygiene (DOHMH) will apply larvicide by helicopter to non-residential, large natural areas such as marshland on Staten Island, Queens, and the Bronx on Friday, Monday, and Tuesday from 6 a.m. to 7 p.m., if weather permits. In case of rain or high winds, the operation will be postponed to the next possible day.
The larvicide is to prevent human infection of the West Nile Virus (WNV), which is transmitted through the mosquito Culex tarsalis. Apart from humans, the virus is known to be transmitted to birds and horses. The West Nile Virus can result in symptoms from those similar to a cold to movement disorders and reduced consciousness to near-coma.
The first WNV human case in the United States was discovered in 1999, and since 2003 the virus has spread nationwide. The DOHMH first responded to the virus’ wide spread by spraying an adulticide, which was later discovered to be ineffective in killing adult mosquitoes, and might even increase the mosquito population as it can kill mosquito predators. The adulticide may also be harmful to humans.
Larvicide, on the other hand, can reduce the population of mosquitoes effectively, and does not pose as much hazard to humans. Two kinds of larvicides are commonly used: the bacteria Bacillus sphaericus and Bacillus thuringiensis israelensis (Bti). Bacillus sphaericus needs oxygen to grow and gathers at the surface to get as much oxygen as possible, thus limiting the mosquito larvae’s oxygen supply, eventually killing them. Bti produces toxic chemicals that kill a limited number of species, including mosquitoes, and have little effect on other species. People who come into contact with Bti in high concentrations may experience eye and skin irritation.
The larvicide is to prevent human infection of the West Nile Virus (WNV), which is transmitted through the mosquito Culex tarsalis. Apart from humans, the virus is known to be transmitted to birds and horses. The West Nile Virus can result in symptoms from those similar to a cold to movement disorders and reduced consciousness to near-coma.
The first WNV human case in the United States was discovered in 1999, and since 2003 the virus has spread nationwide. The DOHMH first responded to the virus’ wide spread by spraying an adulticide, which was later discovered to be ineffective in killing adult mosquitoes, and might even increase the mosquito population as it can kill mosquito predators. The adulticide may also be harmful to humans.
Larvicide, on the other hand, can reduce the population of mosquitoes effectively, and does not pose as much hazard to humans. Two kinds of larvicides are commonly used: the bacteria Bacillus sphaericus and Bacillus thuringiensis israelensis (Bti). Bacillus sphaericus needs oxygen to grow and gathers at the surface to get as much oxygen as possible, thus limiting the mosquito larvae’s oxygen supply, eventually killing them. Bti produces toxic chemicals that kill a limited number of species, including mosquitoes, and have little effect on other species. People who come into contact with Bti in high concentrations may experience eye and skin irritation.
