Virus Finding Among Birds Raises Disease Concern

The discovery of the St. Louis encephalitis virus during routine testing of small birds in Orange County has stirred concern that mosquitoes may transmit the potentially deadly virus to people.

The virus has been detected this summer in the blood of finches and sparrows kept in five of nine surveillance traps. Two chickens in the San Gabriel Valley also have tested positive for the virus.

While experts emphasize that no human cases of St. Louis encephalitis have been reported in the area this year, they caution that mosquitoes can carry the virus from birds to people. “If you find it in the birds, that means the mosquitoes have it. That’s why we use it as an early warning system,” said James P. Webb Jr., vector ecologist with the Orange County Vector Control District, which maintains the five traps where the birds tested positive.

The traps are in Irvine, Huntington Beach, Garden Grove, Anaheim and Fullerton.

The district announced news of the testing this week, and Webb said it represented the most significant activity in the trapping program in five or six years.

In response, the district is urging people to remove potential breeding sites from their yards by properly filtering and covering pools, stocking ornamental ponds with mosquito-eating fish and removing cans, barrels, jars and old tires in which standing water can collect. A wheelbarrow of water can breed as many as 15,000 mosquitoes in one week, officials said.

“The important message for people is to eliminate places where mosquitoes can breed,” said Dr. Hildy Meyers, an epidemiologist with the Orange County Health Care Agency.

Health experts have been particularly sensitive to the threat of encephalitis since a 1984 epidemic sickened 26 Southern California residents, killing six.

Encephalitis can cause brain and spinal cord inflammation. Mosquitoes in California are known to carry St. Louis encephalitis as well as western equine encephalitis, which can affect horses as well as people. The virus cannot be transmitted from person to person or from birds to humans.

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In Orange County, vector control officials grew concerned when regular testing of birds at the nine trapping sites began turning up positive readings. Blood samples are taken from the birds and tested every two weeks.

What caught officials’ attention was the fact that the virus was detected at more than half the sites, and among 8% to 12% of the birds at a site.

“Suddenly, at five or six places, we see positive birds,” Webb said.

Meanwhile, in Los Angeles County, the virus has been detected in two of five so-called “sentinel chickens” in a coop in Monterey Park. Such chickens, like the birds in Orange County, are tested as part of an encephalitis warning system.

The Monterey Park chickens are maintained by the San Gabriel Valley Mosquito Abatement District, which began a widespread search for mosquito breeding grounds.

In nearby Montebello, for instance, technicians searched a cemetery and found evidence of mosquito breeding in graveside flower basins. They emptied water and larvae from thousands of basins during a two-day effort by the San Gabriel district and the South Gate-based Greater Los Angeles County Vector Control District.

In Orange County, authorities have increased spraying activity at wetlands such as the San Joaquin Marsh and Upper Newport Bay.

They are suggesting that residents can protect themselves by applying mosquito repellent, wearing long-sleeved shirts and long pants and by refraining from going outdoors at night in mosquito-infested neighborhoods.

Orange County residents with mosquito problems can contact the Orange County Vector Control District at (714) 971-2421 or (800) 734-2421.

In the San Gabriel Valley, the local district can be reached at (818) 814-9466.