6 HORSES IN A.V. DOWN WITH WEST NILE VIRUS.

Byline: Charles F. Bostwick Staff Writer

LANCASTER - Six horses have been sickened in the past month in the Antelope Valley by the West Nile virus, three so badly they were euthanized.

Nighttime temperatures are dropping since fall had come, but mosquitoes are still active and the ones that survive now will produce a new generation next spring, an entomologist said.

``We're not in the clear yet. Residents should still take precautions and make sure to remove all standing water to avoid mosquito production,'' said Karen Mellor of the Antelope Valley Mosquito & Vector Control District.

Two of the infected horses were from Rosamond, two from Antelope Acres and one each from Quartz Hill and Leona Valley. One Rosamond horse was infected in late August and the others in September, but the vector-control district was just notified of the test results Tuesday, Mellor said.

``Sentinel'' chicken flocks - kept by the vector-control district to be tested regularly for mosquito-borne diseases - have showed signs of the virus in east Lancaster, west Lancaster and east Palmdale.

Mosquitoes captured last month near a marshy area fed by runoff water beside Palmdale Boulevard west of 30th Street East also showed signs of the virus.

A new flock of sentinel chickens was recently placed in the White Fence Farms neighborhood of west Palmdale to monitor any virus activity there, especially since some residents have horses. White Fence Farms is part of the area where property owners voted this summer to join the vector-control district.

Because the incubation time for West Nile virus is three to 14 days, vector-control officials expect to see more infections confirmed within the next month or two.

So far this year, 753 human cases of West Nile virus with 16 deaths have been reported in California. Nationwide, there have been 1,512 human cases with 41 deaths.

Potentially fatal to humans - especially chronically ill and elderly people - and to horses, West Nile virus is spread by mosquitoes that extract blood from infected birds and then pass the virus on to people or other animals.

The vector-control district keeps eight flocks of chickens around the valley to detect the virus. The virus is not as fatal to chickens as it is to ravens, jays and other wild birds.

Health officials say the risk of acquiring the virus is low. About 80 percent of people who become infected with the virus show no symptoms, and most of those who become ill show only mild flulike symptoms.

STEPS TO TAKE

--People at the highest risk of life-threatening disease are over age 50 or have weak immune systems from another illness.

--Most mosquitoes do not have West Nile virus.

--Eighty percent of infected people have no symptoms. People typically develop symptoms between three and 14 days after coming in contact with an infected mosquito.

--Mild symptoms include fever, headache, body aches, vomiting and sometimes swollen lymph glands or a skin rash. They pass on their own.

--Of those infected, one in 150 can develop severe symptoms or even die. Severe symptoms can include high fever, neck stiffness, tremors, muscle weakness, vision loss, numbness and paralysis. Neurological effects can be permanent.

--The best way to protect against the disease is to protect against mosquito bites.

Source: Los Angeles County Health Department, Centers for Disease Control and Prevention.

MOSQUITO TIPS

To reduce exposure to the virus, health officials suggest residents follow the precautions recommended for all mosquito-borne diseases:

--Get rid of standing water, where mosquitoes can breed. Empty all small containers at least once a week, keep pools and spas chlorinated or drained, and avoid over-watering that lets water form puddles on lawns or in gutters.

--Get mosquito-eating fish (Gambusia affinis) for free from the mosquito district if you have sources that cannot be drained, such as fish ponds and large horse troughs.

--Wear long-sleeve shirts and pants and use mosquito repellent containing DEET when outdoors during dusk and dawn.

--Keep tight-fitting screens on doors and windows to prevent mosquitoes from entering homes.

--Horse owners should make sure their horses are properly vaccinated.

--Report stagnant pools and other backyard sources to the mosquito district so technicians can treat them. The mosquito district can be reached at [phone]. Its Web site is www.avmosquito.org. Crows and ravens that have recently died - without obvious trauma - can be reported by calling (877) WNV-BIRD. Use gloves, a shovel or an inverted trash bag to pick up any dead bird.

Source: Antelope Valley Mosquito and Vector Control District

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(ran in AV edition only) STEPS TO TAKE (see text)