April 11, 2014

Mosquitoes begin hatching despite a hot and dry spring

It’s shaping up to be a hot and dry spring in the central San Joaquin Valley, but the drought hasn’t stopped mosquitoes from hatching.

It’s shaping up to be a hot and dry spring in the central San Joaquin Valley, but the drought hasn’t stopped mosquitoes from hatching.

Mosquitoes have plenty of places to breed in backyards, from neglected swimming pools to flower pots. And they breed faster in warm weather.

“It’s typically a week from hatching to flying this time of year,” said Tim Phillips, manager of the Fresno Mosquito & Vector Control District.

Spring is the time to check around homes for places where mosquitoes can breed, he said. Two kinds found in the Valley last year can carry diseases that, in extreme cases, can be fatal. One is West Nile virus, the other is yellow fever.

Most often, symptoms of West Nile virus are mild, but the disease can cause neurological problems.

Mosquitoes that carry the West Nile virus are commonly known as the southern house mosquito and the encephalitis mosquito, and bite at dusk and dawn.

Last year, there were 372 cases of West Nile virus in California and 14 deaths. There were no deaths in the Valley, but Fresno County reported seven illnesses. Tulare had five illnesses, Madera had three and Kings County had one.

There were no positive West Nile virus cases in Merced County last year. However, mosquito warnings were issued in the cities of Merced, Gustine, Hilmar and Winton. Warnings are issued when mosquitoes carrying the virus are detected, according to Allan Inman, manager at the Merced County Mosquito Abatement District.

Inman said 2013 was a successful year for mosquito control in Merced County compared to 2012 when 13 human cases were reported. He said this was due in big part to a quicker and more aggressive response by the abatement district. The county plans to set AGO (autocidal gravid ovitrap), which targets female mosquitoes looking for a place to lay eggs, at the fairgrounds before May 1.

This year, there have been no West Nile virus cases reported in Merced. But according to Inman, it is still too early. The season of disease transmission usually doesn’t start until June, so the risk of becoming infected this time of year is slim to none.

However, Valley mosquito control managers are concerned about the Aedes aegypti mosquito, a species not native to California that was found last year in Madera, Clovis, Fresno and Fowler.

The mosquito is brown with white markings. An aggressive biter during the day, it is commonly found in hot, humid tropical areas, such as southeastern United States, Mexico, and Central and South America.

The mosquito is capable of transmitting deadly yellow fever, dengue and other diseases, said Steve Mulligan, president of the American Mosquito Control Association, a national nonprofit organization.

Vector control agents went door to door last year warning residents to empty all standing water, and the insecticide promethean was sprayed in and around thousands of infested homes.

This year, six of the species have been trapped in Clovis and a female Aedes aegypti mosquito has been caught in a Madera trap. There’s no indication of disease in the mosquitoes, Mulligan said.

The Aedes aegypti mosquito acquires yellow fever and dengue from infected humans, then transfers the infections to other people. Dengue is a virus that can cause headaches, body pains and a rash similar to measles. Extreme cases can be deadly. Yellow fever is a virus that causes severe flulike symptoms and sometimes jaundice. It also can kill. Last year, the Aedes aegpyti mosquito was first found in a trap near the Madera cemetery on June 9.

The female mosquito lays up to 200 eggs several times a season, preferring to lay them just above the water line of a container. And because mosquitoes require very little water to breed, the Merced County Mosquito Abatement District, suggests that residents check their properties and drain even the smallest amount of standing water.

“We definitely need the public’s cooperation,” said Inman. “We can only see what’s in people’s front yards, but we can’t see what’ s in their backyards. And if anyone sees properties with standing water around their neighborhoods, they should give us a call.”

Besides draining empty containers, the Merced County Mosquito Abatement District also recommends that people stay indoors at dusk and dawn, wear clothes that protect the skin from bites, and use mosquito repellant containing DEET.

For more information the abatement district at (209) 722-1527.

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