Warm, wet weather brings West Nile worries

Though not as fun as barbecues, swimming and vacations, mosquitoes are part of summer. A wet winter and heavy snowmelt this year are heightening concerns about the pests and the West Nile virus they sometimes carry.

Signs of the virus have already occurred. State health officials reported last week that a horse in Sparks was found infected with West Nile virus. The virus is most often transmitted to humans and animals from the bite of infected mosquitoes. Birds are the original carriers of the virus.

It can prove deadly to some who are infected with it.

The first Nevada cases of West Nile in humans were reported in 2004. Last year, 30 human cases of the disease alone were reported in the state.

It has been five years since someone in Carson City contracted West Nile virus, though health officials say they believe it was contracted while the person was out of the area.

Spraying has already begun in an effort to cut down on mosquito numbers.

Carson City Environmental Health has sprayed once this spring. A 250-acre area along the Carson River corridor targeting Mexican Ditch, Buzzy's Ranch and other sections was treated with Altosid by helicopter last week.

Altosid, also known by its generic name Methoprene, is an insecticide and growth regulator. It affects mosquitoes and other insects in their egg and larvae stages so they can't reproduce. It won't kill the adult insects, however, according to the U.S. Environmental Protection Agency.

The city's first pesticide spray of the season was a little earlier than usual, May 19, and surveying, trapping and treatment have been going on since the beginning of the month, said Teresa Hayes, an environmental health specialist for the city.

"Our focus this year will be on surveillance and abatement," Hayes said. "We'll check every complaint."

Hayes advises people to dump out all standing water - the most attractive location for mosquitoes to breed - and to check for it in not-so-obvious locations, such as old tires and children's buckets, wagons and plastic pools, for example.

Also fix door and window screens so mosquitoes can't fly into your home, and apply insect repellent whenever you go outside, she said.

A proper repellent is a brand that includes at least 20-30 percent of the insecticide DEET, according to the Nevada State Health Division.

As the weather warms, so will standing water, which will provide an even more hospitable climate in which the mosquitoes can breed. Although mosquito season typically runs from April to October, the West Nile cases are most prevalent in August and September, the state also reported.

"Check your property now," while the weather is cooler, and be vigilant about removing water as it accumulates through the season, Hayes advised.

People with ornamental ponds should be sure to keep them clean and remove algae. Aerators and fountains also help to retard mosquito breeding in these ponds because these items keep the water moving. Mosquitoes prefer standing water.

And effluent, used to water such places as golf courses, is richer in nutrients and runs at a higher temperature, making these areas important to watch because warm, rich water can make mosquitoes breed even faster, Hayes said.

Horse owners need to ensure these pets are vaccinated for the virus.

Other diseases caused by mosquito bites besides West Nile include other forms of encephalitis, such as St. Louis, LaCrosse, Western and Eastern equine strains, and dengue fever.

Mosquitoes around the globe can spread malaria and yellow fever, but these are diseases that aren't known to occur in the U.S.

• Contact reporter Terri Harber at tharber @nevadaappeal.com or 882-2111, ext. 215.

Tips on avoiding West Nile Virus

Avoid mosquito bites

Use insect repellent on exposed skin when you go outdoors. Use an EPA-registered insect repellent such as those with DEET, picaridin or oil of lemon eucalyptus. Even a short time being outdoors can be long enough to get a mosquito bite. And it only takes one bite to become infected.

Get double protection

Wear long sleeves during peak mosquito biting hours, and spray repellent directly onto your clothes.

Clothing can help reduce mosquito bites

When weather permits, wear long-sleeves, long pants and socks when outdoors. Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or another EPA-registered repellent will give extra protection. Don't apply repellents containing permethrin directly to skin. Do not spray repellent on the skin under your clothing.

Be aware of peak mosquito hours

The hours from dusk to dawn are peak biting times for many species of mosquitoes. Take extra care to use repellent and protective clothing during evening and early morning.

Drain standing water from around your home

Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by getting rid of items that hold water such as flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, discarded tires and cans.

Install or repair screens

Some mosquitoes like to come indoors. Keep them outside by having well-fitting screens on both windows and doors. Offer to help neighbors whose screens might be in bad shape.

Report dead birds to local authorities

Dead birds may be a sign that West Nile virus is circulating between birds and the mosquitoes in an area. Over 130 species of birds are known to have been infected with West Nile virus, though not all infected birds will die. It's important to remember that birds die from many other causes besides West Nile virus.

- SOURCE: Center for Disease Control