Wet Winter Raises Encephalitis Fears : Disease: Rainfall may produce a record number of mosquitoes, which carry the untreatable virus. Authorities are trying to keep track of the pests amid slashed budgets.

After a winter of record rainfall, California public health authorities are worried that the state may experience a summer of record mosquito production--a condition that could lead to outbreaks of encephalitis, a disease carried by the insects that is untreatable and, on rare occasion, fatal.

Across the state, from Los Angeles to Kern County to Sacramento, mosquito control authorities and health officials are scurrying to keep track of the pests, which breed in water during the warm weather. Moreover, the fear of an outbreak comes at a time when some mosquito abatement districts are expecting budget cutbacks of as much as 30%.

“This is going to be the toughest year that we have had since I can remember in 15 years,” said Allen Hubbard, manager of the Sacramento-Yolo Mosquito and Vector Control District. “We’re going to have more mosquitoes and we’re really worried about the disease factor.”

Although encephalitis usually occurs in rural areas, experts are concerned that this year there could be an outbreak in heavily populated urban and suburban regions, including Orange and Los Angeles counties. An urban outbreak took health authorities by surprise in 1984, when Los Angeles County experienced its first cases and its first death from the disease.

In Orange County, which has not had a reported case of mosquito-borne encephalitis since 1984, officials are suggesting that residents remove any standing water, the breeding ground for mosquitoes, from their yards. Dr. James Webb, an ecologist with the Orange County Vector Control District, also suggested that people cover swimming pools or clean them daily. Those with ponds or fountains might consider adding mosquito fish, a two-inch-long fish that eats mosquito larvae and can be obtained from Orange County Vector Control, he said.

To minimize the risk of being bitten, vector control officials suggest that residents use mosquito repellent, make sure window screens fit securely and avoid working outdoors at dawn or dusk, when mosquitoes are most active.

Robert Murray, an epidemiologist who tracks encephalitis for the state Department of Health Services, said: “The potential for (an outbreak) in heavily populated urban/suburban areas is frightening.”

Murray and other state officials are cautious not to sound too alarmist, saying it is too early in the season to predict whether there will be a major outbreak. But William Reeves, a retired UC Berkeley professor and expert in the field of mosquito-borne disease, said he is concerned about a repeat of the widespread outbreaks of encephalitis that California experienced in the 1940s and 1950s, before the state put extensive mosquito control measures into place.

“If you travel up and down the Central Valley of California and other parts of the state and see the water availability, it is very similar to what we had in the early days of the ‘40s and ‘50s,” Reeves said. “I can’t promise anybody that there is going to be an epidemic. It could for some reason not happen, but I’ve been doing this for 50 years now and wrote the so-called book on the topic.”

Mosquitoes in California are known to carry two types of the encephalitis virus--western equine encephalitis, which strikes horses as well as humans, and St. Louis encephalitis, which is the more common of the two in this area. Both strains produce the same symptoms.

There is no treatment for encephalitis, which can cause inflammation of the brain and spinal cord. Although most infections are mild, producing flu-like symptoms of headache and fever that last about two weeks, the illness can on rare occasions become severe, causing confusion, paralysis, coma and death.

Over the past 10 years, there have been 83 cases of encephalitis reported in California, and two deaths. But for every case that is reported, state health officials say hundreds more go unreported because the symptoms are so mild that physicians and victims fail to recognize them.

The California Department of Health Services uses chickens as a means of tracking the disease. This year, the agency is shipping 1,000 chickens to mosquito abatement districts across the state. These “sentinel flocks,” as they are known, are set out in cages near bodies of water that might breed mosquitoes.

Every two weeks, blood is drawn from the chickens to see whether they have contracted encephalitis--a sign that they have been bitten by infected mosquitoes.

In the southern part of the state, the chickens have been in place for a month and have shown no signs of disease, said Ken Townzen, a public health biologist supervising the program. Townzen said chickens are being shipped this week to northern districts, where cooler weather delays the mosquito breeding season.

Townzen said there are three conditions necessary for an epidemic: plenty of water, an abundance of mosquitoes and evidence that the virus is present. “Right now we’re at the water stage,” he said. “And in Southern California, in certain areas, they are at the mosquito stage. But we don’t have any indication of virus yet.”

In Los Angeles County, authorities say their traps are showing twice as many mosquitoes this year as last. In tracking encephalitis, officials look for two species in particular--the culex tarsalis and the aedes malinamon. The mosquitoes become infected by biting wild birds.

Officials of the Southeast Mosquito Abatement District, which covers 1,000 square miles east of the Harbor Freeway, said Monday that they have received approval from the U.S. Environmental Protection Agency to begin spraying chemicals at mosquito breeding sites to prevent the larvae from developing into adult insects. The agency also uses other means, including so-called “mosquito fish”--minnows that feed on the larvae--to curb breeding.

Other districts, worried about a proposal by the state Legislature to cut their funding, are delaying plans for spraying. Hubbard, the Sacramento official, said his agency usually conducts aerial spraying in the Sacramento Valley, where huge rice paddies provide fertile ground for mosquito breeding.

“We’re afraid to spend too much right now,” Hubbard said. “Normally we spend several hundred thousand dollars a year (on crop dusting) and we’re not going to do that this year at all.”

Times staff writer Catherine Gewertz contributed to this story.

Dangerous Illness

Mosquitoes in California are known to carry two types of the encephalitis virus, western equine and St. Louis. Both cause mild, flu-like symptoms in most people, but in severe cases can cause paralysis, coma or death. There is no treatment.

Here are reported cases in California; hundreds more go unreported.

YEAR WESTERN EQUINE ST. LOUIS DEATHS 1981 0 0 0 1982 1 0 0 1983 0 9 1 1984 0 26 1 1985 0 3 0 1986 2 3 0 1987 0 1 0 1988 0 2 0 1989 0 29 0 1990* 0 2 0 1991** 0 3 0 1992 0 2 0

* 1 case contracted outside state

** 2 cases contracted outside state

SOURCE: State Dept. of Health Services