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Residents Reminded To Be Wary Of West Nile Virus
mosquito graphic

More than 340 new West Nile Virus-positive mosquito samples were collected across California in the past week, including several in San Joaquin and Stanislaus counties.

San Joaquin County Mosquito and Vector Control District Public Information Officer Aaron Devencenzi said residents still need to be vigilant in protecting against mosquitoes as we wind through the late summer and early fall months.

“As long as people continue to see mosquitoes outdoors, it’s important to take precautions,” he said.

The District is also asking people to call in and report it if they are bothered by daytime biting mosquitoes or have significant numbers of mosquitoes on their property; call 209-982-4675.

While mosquitoes are most often active at dusk and dawn, the daytime biting mosquitoes are a different, more invasive breed and District officials want to be notified if they are found.

“People also need to be careful of the urban myths about what may repel mosquitoes,” he said, urging instead that residents follow the Public Health Services ‘Three Ds’ of protection.

Public Health Services recommend that people prevent exposure to mosquito bites and West Nile Virus by practicing the D’s:

DEET – Apply insect repellent containing DEET, picaradin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children two months of age and older.

Dawn and dusk – Mosquitoes bite in the early morning and evening so it is important to wear proper clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep mosquitoes out. Repair or replace screens with tears or holes.

Drain – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including flower pots, old car tires, rain gutters and pet bowls. If you know of a swimming pool that is not being properly maintained, contact your local mosquito and vector control agency.

The local district, in fact, has mosquitofish available for local residents to help keep the mosquito population down in ponds and other water on their property.

“We have them, we will deliver them, or they can come to the district office and pick them up,” Devencenzi said of the mosquitofish.

They are available throughout spring, summer and fall.

Devencenzi added that as of right now, the number of positive mosquito samples and cases of West Nile Virus are “very close to a five-year average” for the San Joaquin County region.

Positive tests of mosquito samples have dropped from the numbers being seen earlier this spring when heavy rains pelted the region but Devencenzi said there’s still the need for caution.

“We do have significant West Nile Virus activity,” he said. “Last week, Aug. 6 through 12, we had 15 positive mosquito samples, from Escalon, Lodi, Stockton, Ripon and Manteca, so pretty much from all over the county. We also had two positive birds, from the Stockton area.”

The trapping and testing of mosquito samples will continue, he said. Samples can contain up to 50 individual mosquitoes.

The district is also testing for St. Louis Encephalitis Virus (SLEV). SLEV is related to West Nile Virus (WNV) and is transmitted via the bite of Culex mosquitoes, the same mosquitoes that transmit WNV. It has not been detected here yet but has been detected in other California counties. It presents very similar to WNV, said Devencenzi, and officials are keeping an eye out for it.

Statewide this year, there have been 22 human cases of WNV reported, including a 70-year-old Manteca man diagnosed in July. There have been 171 dead birds testing positive for WNV, and 1814 positive mosquito samples.

The San Joaquin County Mosquito and Vector Control District is available to help with the prevention of mosquitoes in neglected pools and respond to other mosquito problems in your area. To request District service, call 209-982-4675, 1-800-300-4675 or visit the District website at