June 27, 2008

Heavy rainfall has affected most of the Midwest, but flooding won't be the only consequence. An increased mosquito population will be an outcome of more rain as well, said Barbara Ogg, a University of Nebraska-Lincoln Extension educator in Lancaster County.

"It's already increased," she said. "We've seen a lot of mosquitos, and it's going to continue. We're going to see numbers of mosquitos that we haven't seen for many years."

The greatest risk associated with mosquitos is the West Nile virus. In 2007, 163 Nebraskans contracted West Nile with four of those leading to fatalities, according to the Department of Health and Human Services Web site.

To help protect against mobs of mosquitos, Ogg said, Nebraskans need to prevent mosquito breeding while protecting themselves.

Any containers or standing water should be dumped. A small pond or body or water that can't be removed can pose problems. Ogg said products containing bacillus thuringiensis israelensis, or BTI, come in the form of doughnuts, biscuits or granules and can be put into a pond to cut down on mosquito larvae.

"You don't have to worry about wildlife or animals drinking out of a pond," Ogg said, "because it is something that is real specific to mosquito larvae."

She said BTI products can be bought at hardware stores or garden centers and cost $10 to $15. Ogg said the amount of BTI product to buy depends on the square footage of a pond or standing water.

For those with plenty of cash, a device called a Mosquito Magnet can be bought for about $500. They work with a propane tank to generate carbon dioxide, which attracts mosquitos and traps them.

"Unfortunately, bug zappers don't work on mosquitos," Ogg said. "Mosquitos aren't attracted to light -- they find us by detecting carbon dioxide and other odors we give off."

The Center for Disease Control recommends three types of repellents that work best against mosquitos.

-- DEET is the most common chemical in insect repellents. DEET works best for those who want to stay outside for long periods of time. However, Ogg said, many people dislike the oily feeling and odor of DEET. She said no definitive studies show DEET causes heart problems in children, but the American Association of Pediatrics doesn't recommend its use on children under 2 months old.

-- Picaridin is a repellent that has similar effectiveness compared with DEET. Advantages are that it is not greasy and has no odor. The AAP has not formulated recommendations about using picaridin on children.

-- Natural oil of lemon eucalyptus is available in Repel Lemon Eucalyptus, a non-greasy product with a pleasant smell. Oil of lemon eucalyptus may not last as long as the other two repellents. A natural botanical product, it may appeal to those who want to use green products.

Ogg said because the elderly are at a greater risk of having serious reactions from the West Nile virus, people older than 50 should always wear repellent if they are exposed to mosquitos.

She said Culex tarsalis, the mosquito that is the best vector for the West Nile virus, is more prevalent farther west. For that reason, those in central and western Nebraska need to be especially conscious of mosquitos and protect themselves with repellents.

"There's a lot of cases in the eastern part of the state," Ogg said, "but it's because populations are higher. On an individual basis, people in the western part of the state are more at risk."

Symptoms of West Nile, which causes the brain to swell, include headaches, neck stiffness, skin rash, stupor, disorientation, paralysis, coma and possible death. Ogg said symptoms begin to show 3 to 14 days after the virus is contracted. She recommends seeing a doctor as soon as these symptoms show.

Mosquitos may be more prevalent this summer, and Ogg said they will continue being a health concern for months ahead.

"These Culex tarsalis mosquitoes start feeding on humans and other large mammals in the summer after nesting birds leave their nest," she said. "The risk of West Nile virus will continue through the summer months until frost."