Don’t Give Mosquitoes Any Breeding Room, Public Told

Recent storms have turned marshes, back yards and swimming pools into breeding grounds for disease-carrying mosquitoes, and county health officials say they fear the mosquito population will increase sharply over the next few months.

The Orange County Vector Control District, concerned about a potential rise in mosquito-borne diseases such as encephalitis, is urging residents to quickly rid their homes of mosquito-breeding areas.

“Mosquitoes are proven carriers of disease,” said Dr. James Webb, an ecologist with the district. “That’s why homeowners should get on top of things and dump any standing water they have in their yard.”

Even a small amount of water can serve as a hatchery for mosquitoes, according to health officials. Water in a wheelbarrow, for example, can spawn 15,000 mosquitoes in one week.

Karen Adams, a public health nurse with the Orange County Health Agency’s department of epidemiology, advises people living in mosquito-infested areas to avoid being outdoors during the early-morning and evening hours. Residents should also wear long-sleeved shirts or use insect repellent when they go outside, she said.

While Orange County is home to 21 types of mosquitoes, Webb said his main concern is the southern house mosquito, a brown mosquito adapted to human habitations and one of the mosquito species known to carry the encephalitis virus.

“These mosquitoes are so small that you can’t feel their bite,” Webb said. “And it’s very hard to hear them coming because they usually attack the lower body. They’re very sneaky.”

The encephalitis virus transmitted by the mosquito is especially dangerous to young children and the elderly. In many adults, the virus, which inflames the lining of the brain, causes flu-like symptoms. But with children and elderly people, the virus can cause death.

The most common form of the virus is St. Louis encephalitis, which is also known as sleeping sickness. This strain produced most of Orange County’s recorded cases of encephalitis. Another common strain is Western equine encephalitis. It is mostly found in horses and other livestock and there are no recorded cases of people contracting it in the county.

Although mosquito season in California typically runs from June until October, Webb said it is possible for mosquitoes, and the diseases they carry, to become a problem at other times.

“Traditionally, St. Louis encephalitis is a June-to-September problem in the western states, but Southern California is a unique environment that hasn’t really been studied in terms of the transmission of disease from mosquitoes,” Webb said. “We still don’t know the whole picture.”

Webb said he is not positive that the number of encephalitis cases will rise, but he noted that this year’s weather conditions are similar to 1984, when the county had its last recorded outbreak of mosquito-borne encephalitis.

“In the literature, when there is a significant rainfall before mosquito season, and it is followed by hot, drought-like conditions, there is a large increase in the number of mosquito-related encephalitis cases,” he said.

Dr. Hildy Myers, an epidemiologist with the Orange County Health Care Agency, said there were only two reported cases of mosquito-borne encephalitis in California last year. No cases have been reported in the county since 1984, when about half a dozen people contracted the virus, one of whom died.

Born to Breed After a month of heavy rains, mosquitoes are thriving and breeding again. Here are some tips for keeping these pests at bay. Prevention: * Dump water from open containers. * Cover swimming pools or clean every day with filter and skimmer. * Put mosquito fish in ponds, fountains or other bodies of water that cannot be drained. The two-inch-long fish eat mosquito larvae and may be obtained free from Orange County Vector Control. * Make sure screens fit securely. * For clothes and body, use repellents with the active ingredient diethyltolumide. * Avoid outdoor work at dusk or dawn, when mosquitoes are most active. * For more information, call Orange County Vector Control, (714) 971-2421. Diseases: Encephalitis is the most common mosquito-borne disease in the western United States. Orange County has had no cases since six were reported in 1984. Studies show mosquitoes are not carriers of the virus that causes AIDS. Sources: Orange County Vector Control, Los Angeles Times reports