Rising Number of Mosquitoes Raises Concern

Orange County has experienced a significant increase in its mosquito population, several species of which are known carriers of a potentially fatal strain of encephalitis virus, a Vector Control District official said Thursday.

Fred Beams, assistant district manager, said the annual mosquito infestation is occurring weeks earlier than in previous years. Beam said that stagnant water in backyards or vacant lots--often standing in such items as old tin cans or tires--appears to be the source of the current infestation.

“I don’t want to cry wolf or sound overly alarmed, but at the moment there already are two unconfirmed cases of (the St. Louis strain of) encephalitis in Los Angeles County this year,” he said. “Our county is known to have 21 species of mosquitoes, and five and possibly six of those are carriers of the virus.”

Symptoms of the virus include a rising temperature, headaches and muscle aches, all of which can lead to permanent brain damage or death.

Beams said he was convinced that the surge in insect populations “can be narrowed down to ordinary backyard sources,” because the county Vector Control District sprays all storm drains, gutters, catch-basins and other public sites with standing water every nine days, a schedule designed to disrupt mosquito breeding cycles.

He added that three so-called sentinel flocks of chickens maintained in the county by the Vector Control District to detect the presence of virus-bearing mosquitoes “so far have shown nothing” in the way of infected insects.

The flocks are located in the San Joaquin Marsh in Irvine, at Featherly Regional Park in Trabuco Canyon and near San Mateo Point in San Clemente. If a chicken is bitten by a disease-bearing mosquito, antibodies in the bird’s system will attack the virus, and this process shows up in periodic blood tests of the flocks.