By DONNA BETH WEILENMAN
MARTINEZ, Calif. – West Nile virus has been found in a group of mosquitoes north of Marina Vista near Fairmont Road, and in a sentinel chicken near Escobar and Pine streets in Martinez, said Deborah Bass, public affairs manager for the Contra Costa Mosquito and Vector Control District.
The district has started fogging in Martinez and in neighboring areas, she said.
So far this year, eight mosquito groups, 11 birds, 17 chickens and one horse in Contra Costa County have tested positive for the virus, Bass said.
In 2006, two people from Contra Costa County died of the disease, and since 2005, 54 have been diagnosed with West Nile virus, she said. However, recent studies have indicated that a majority of cases are not diagnosed and the disease is underreported.
Of those affected, only one in five will show the symptoms of a fever accompanied by headache, body aches, joint pains, vomiting, diarrhea or rash. Most will recover, but lingering weakness can last for weeks to months, according to information provided by the Centers for Disease Control and Prevention.
For about 1 percent, particularly those 60 and older or those with other medical conditions, the disease is worse. They’ll develop a serious neurological illness, such as encephalitis or meningitis, and about 10 percent of those will die, the center’s information said.
Martinez residents should take precautions, Dr. Steve Schutz, the district’s scientific program supervisor, said.
“At this time of year, the type of mosquitoes that can transmit West Nile virus are less selective about their blood source and are more likely to bite people,” he said. “Wearing mosquito repellent when outdoors is important.”
A vaccine is available to prevent the disease in horses, but so far, none has been approved for humans. Schutz recommended the use of repellents containing DEE, which Bass said is the most effective agent; Picaridin, a pepper derivative; or oil of lemon eucalyptus, as well as staying indoors at dawn and dusk or when mosquitoes are present. Bass said citronella is helpful but only in small areas.
In addition, Martinez residents should dump standing water to prevent mosquito breeding. Bass said residents should check their yards at least twice a week for flower pot saucers, rain gutters, boat covers, trash that can collect water, lawn indentations that hold water for several days, trash can lids, old tires, bird baths and anything that can hold water for more than five days.
Residents can prepare for anticipated winter rains, but also need to note where sprinkler water collects, too, she said.
She said neglected swimming pools continue to pose “an enormous problem in Contra Costa County.” Even a partially filled pool can produce more than a million mosquitoes – including the two types that transmit West Nile virus – and can spread disease up to five miles away, she said.
Martinez residents may report neglected swimming pools by calling (925) 771-6195, or by visiting www.ContraCostaMosquito.com. The same website tells visitors how to obtain free mosquito-eating fish for ponds and water troughs, and provides the district’s fogging schedules. Dead birds can be reported to the state hotline, 877-968-2473.
Bass said residents don’t need to take any precautions before the district fogs their area. The usual product used is Pyrocide 7067, a botanical pesticide derived from chrysanthemum flowers.
“We use very little, approximately 1/4 teaspoon of active ingredient per acre.” The products used are registered with the Environmental Protection Agency for both mosquito control and public health protection, she said.
We all need to work together to combat mosquitoes and West Nile virus,” Bass said. “A few hundred mosquitoes only need a few tablespoons of water to thrive and become biting adult mosquitoes. And it only takes one bite to get the virus.”