The yellow-fever mosquito is still biting residents in Clovis and Madera and the only way to get rid of the potentially deadly pest is with the public's help, authorities say.
Wednesday, mosquito-abatement crews urged the public to call them to set up a home inspection.
"Until we eliminate the breeding sites, we will still have it," said Steve Mulligan, manager of the Consolidated Mosquito Abatement District, which oversees Clovis.
Mulligan said there are hundreds of homes inside and outside the containment area -- bounded by Barstow, Temperance, Shaw and Armstrong avenues -- that still need to be inspected.
For the past six weeks, crews have gone door to door to ask homeowners to allow them in their backyards, but many residents have not responded to the request, he said.
Dozens of homes also need to be inspected in Madera near the Arbor Vitae Cemetery, west of Highway 99, said Leonard Irby, manager of the Madera County Mosquito and Vector Control District.
When the first yellow-fever mosquitoes was found June 9 near the Madera cemetery, the infestation area was confined to a nine-block neighborhood, Irby said. Since then, the infestation area has grown, he said.
"It's a pesky little guy that likes to hide out," he said.
There's no evidence of the mosquito crossing Highway 99 into east Madera, Irby said. But the mosquito has been discovered southeast of Madera, in the Madera Ranchos area near Avenue 12, and in the Parkwood area near Avenue 13 and Road 27. Irby said abatement crews believe they have eradicated the mosquito from those areas, but residents still need to exercise caution, because mosquitoes with the West Nile virus have killed three birds in the Madera Ranchos area.
Mosquitoes that carry the West Nile virus are commonly known as the southern house mosquito and the encephalitis mosquito, and bite at dusk and dawn. They are native to the central San Joaquin Valley.
Fresno, Kings, Madera and Tulare counties have reported mosquitoes positive for the virus this year.
The yellow-fever mosquito, known as Aedes aegypti, is an aggressive, day-biting insect not native to California. It is commonly found in hot, humid tropical areas, like the southeastern United States, Mexico, and Central and South America.
This mosquito is a carrier of yellow fever, dengue and chikungunya -- tropical diseases with symptoms including fever, severe headaches and body aches. In severe cases, the diseases can lead to death.
Unlike common mosquitoes that like stagnant swimming pools, a female Aedes aegypti can lay eggs in any open container -- a planter, a bucket, a bird bath, an unused dog dish or an empty beer bottle -- as long as it has water.
The female mosquito also lays up to 200 eggs several times a season, and prefers to lay eggs just above the water line of the containers.
Since finding the yellow-fever mosquito in Madera and Clovis, abatement crews and local health officials have worked long hours and on weekends to determine the extent of the infestation, Mulligan and Irby said.
In Madera, crews have sprayed a mosquito-killing, larvacide fog from a pickup truck in the infected neighborhoods, hoping to eradicate adult Aedes aegypti, Irby said. The fog is organic and not harmful to residents, pets or plants, he said. Crews also have sprayed insecticide in infested areas.
Clovis has not used the larvacide fog, Mulligan said. Instead, crews have been spraying insecticide in infested areas, he said.
There are no plans for aerial spraying in either city, Mulligan and Irby said.
Authorities still don't know how the yellow-fever mosquito found a home here. The mosquito tends to stay near its home and it travels less than a quarter mile, Mulligan and Irby said. The distance between Madera and Clovis is about 35 miles. The Madera Ranchos and Parkwood areas are halfway between Madera and Clovis.
Mulligan said Clovis and Madera are the only places where the mosquito is still breeding. "It could be in other areas, but we won't know the full extent of the problem until residents let us inspect their homes," he said.
Residents who are bitten by a mosquito during the day or who detect unusual numbers of mosquitoes in one area are urged to report them to the Madera Mosquito and Vector Control District at (559) 662-8880 or the Consolidated Mosquito Abatement District at (559) 896-1085.
Tips to control mosquitoes and avoid bites:
Dump out any water-filled containers.
Throw away containers that are not needed.
Containers or large objects, such as boats or old appliances, should be covered, turned over or placed under a roof so they don't fill with water.
Clean bird baths and pet-watering dishes weekly and dump the water from overflow dishes for potted plants and flower pots.
Make sure gutters are not holding water and cover rain barrels with tight lids.
Fill tree holes and other cavities in plants with sand or soil.
Check for hidden bodies of water such as wells, septic tanks, manholes and clogged drains.
To avoid mosquito bites, wear long-sleeve shirts, long pants, socks and shoes. Also used repellents such as DEET, picaridin, oil of lemon eucalyptus, or IR3535 (as directed on the product label). Do not use repellents under clothing.
Also use mosquito netting over infant carriers, cribs and strollers, and install or repair window and door screens to keep out mosquitoes.