West Nile Virus (WNV) is a mosquito-borne pathogen that poses a significant threat to public health. It has spread westward since being found in the northeastern U.S. in 1999. Most people have some degree of immunity to the virus, but as with many pathogens, the very young and very old are most susceptible. Symptoms of infection with WNV are flu-like at first (West Nile Fever), and most people recover from this, but a percentage of infected people develop spinal meningitis or encephalitis. In the last 3 years, over 500 people have died from WNV infections in the U.S.

The U.S. Center for Disease Control (CDC) states that the best way to control the mosquito species that vector the disease is to use an integrated pest management (IPM) approach. Key to the IPM approach is knowledge of potential breeding sites, host-vector behaviors, historic vector distributions, host demography, and disease outbreaks.

The main hosts of WNV are birds belonging to the corvid family (commonly represented by jays, magpies, and crows). WNV cannot be transmitted directly from birds to humans (or to any other mammal)—the virus must be vectored by a mosquito. WNV has been found in Utah and has infected people from Box Elder County down to Washington County. The best ways to reduce the spread of this disease are to suppress mosquito populations and avoid contact with mosquitoes.

Generally, the most effective and economical way to control mosquitoes is to eliminate or alter their breeding sites (i.e., municipal drainage systems, irrigation canals, marshes, backyard ponds, bird baths, tree holes) such that the site no longer allows mosquito larvae to complete their development. This is often the most permanent means of reducing a local mosquito population.

The use of a mosquito larvicide, such as Bacillus thuringiensis israelensis (Mosquito Dunks), methoprene (Altosid), or monomolecular surface films, is very effective at destroying mosquito populations. Typically, larvicides are more effective at mosquito abatement than adulticides because the larvicide application targets the immature mosquitoes when they’re relatively consolidated within a water body. Once the adult emerges, it disperses and seeks shelter, thus greatly increasing the area requiring treatment.

The mosquitoes that vector WNV (Culex pipiens, typically) are active in the morning and early evening (when the sun is low), though they will indulge in a midday bloodmeal should the opportunity present itself. Wearing long sleeves, pants, and repellent should help keep mosquitoes away if you must be outdoors at dawn or dusk. To keep mosquitoes out of the home, make sure window screens are well-secured and do not have holes. Get rid of backyard breeding sites wherever possible—empty standing water in flower pots, buckets, barrels, trash cans, rain gutters, bird baths, and children’s wading pools. Consider drilling holes in tire swings and applying small amounts of cement to tree holes (or any depression where water collects).