Wednesday, October 30, 2013

Mosquitoes known to carry dengue, yellow fever seen in California [ W4llppr ]

By Steve Gorman

LOS ANGELES (Reuters) – A tropical mosquito known to carry dengue and yellow fever has been detected in California, raising concerns among public health officials and prompting intense efforts to prevent the spread of the potentially deadly diseases.

The mosquito, known by the scientific name Aedes aegypti requires little standing water to reproduce.

“This mosquito bites during the day. It’s an aggressive mosquito and that in itself – the nuisance aspect – is going to be huge for people in our areas,” said Steve Mulligan, director of the Consolidated Mosquito Abatement District that encompasses parts of Fresno County.

“It could bring about an impact in our lifestyle. We like to be outdoors in summertime and enjoy our backyards,” he said.

None of the specimens trapped and tested since the mosquito first appeared in California’s Central Valley in June have been found to carry disease, and no illnesses associated with the insect have been reported.

But the tiny insect’s feeding and breeding habits make it a voracious pest, which if allowed to propagate could pose a risk to the nation’s most populous state as an avenue of infection for dengue and yellow fever, public health authorities said.

Native to tropical and subtropical regions, the species has already turned up in Hawaii, Arizona, Texas and parts of the U.S. Southeast, Florida in particular.

“We’re hoping to eradicate this species, but that will be challenging, and we’re certainly interested in whether it can survive the winter months in California,” said Vicki Kramer, chief of vector-borne diseases for the state Department of Public Health.

Vector-control authorities in Fresno, Madera and San Mateo counties, where the mosquito has been identified, are warning residents to empty bird baths, dog dishes, flower pots and other sources of standing water from around their homes.

Homeowners are also advised to keep screens over open windows and doors, to apply repellent when outside and to use mosquito netting over infant cribs, carriers and strollers.

Mosquito abatement districts are using special pesticides in places where aegypti is found, but they need help from the public to pinpoint infestations. They say the biggest telltale sign is being bitten in the daytime.


Most mosquito species that bite people and are common to residential areas of California tend to feed at night. Others that bite during daylight hours are typically found in rural or undeveloped areas only, officials say.

For now, the risk of contracting dengue or yellow fever in California is low, because a mosquito would have to bite an already infected person then bite another person, experts say.

While there have been locally transmitted human cases of dengue reported in Florida this year, and occasional cases in Hawaii and Texas, all 183 cases documented in California since 2010 have been in people infected while traveling in Latin America, Asia or Africa, Kramer said.

Yellow fever in California is even more rare. The last known case was in 1999, she said.

Aedes aegypti is a primary vector for both diseases, and the chances of local transmission rise as the incidence of “imported” human cases grows and the Aedes aegypti mosquito population expands.

Dengue causes high fever, debilitating joint and muscle pain, headaches, vomiting and a skin rash. Yellow fever often begins with flu-like symptoms and can progress to a more severe phase that can lead to jaundice and internal bleeding.

Both can be fatal. Worldwide, some 500,000 people with severe dengue require hospitalization each year, and 2.5 percent of those stricken die, according to the World Health Organization. It estimates the annual number of yellow fever cases worldwide at 200,000, resulting in 30,000 deaths a year.

(Reporting by Steve Gorman; Editing by Cynthia Johnston and Gunna Dickson)