As pleasant spring temperatures transition into sweltering summer days and nights, mosquitoes will be more active and looking to make a meal of any arm, leg, neck, etc. they can find. Along with their ravenous appetite comes a risk of contracting West Nile Virus and St. Louis encephalitis.
Both the Turlock and Eastside Mosquito Abatement Districts would like to remind residents to take steps like "Dump and Drain" to prevent mosquitoes and mosquito‐borne diseases.
In 2020, California recorded 231 cases of West Nile Virus in humans and 20 cases in horses. Of the 231 human cases, 11 were fatal, according to the California Department of Public Health.
Stanislaus County saw 36 cases of West Nile Virus in humans and three in horses. The county also recorded one human case of St. Louis encephalitis.
As of April 23, there have been no cases of West Nile Virus reported in California.
Mosquitoes become infected with West Nile Virus when they feed on infected birds. Infected mosquitoes can then spread West Nile Virus to humans and other animals when they bite, according to the Centers for Disease Control.
Approximately 1 in 5 people who are infected with West Nile virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Less than 1 percent will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). About 10 percent of people who develop neurologic infection due to West Nile virus will die, according to the CDC. People over 50 years of age and those with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and organ transplants, are at greater risk for serious illness.
There are no medications to treat or vaccines to prevent West Nile Virus infection. People with milder illnesses typically recover on their own, although symptoms may last for several weeks or months. In the neuroinvasive forms, patients can suffer severe and sometimes long-term symptoms.
It’s not just the transmission of West Nile Virus that has the area’s mosquito districts concerned. The mosquito breed responsible for transmitting the Zika virus has been detected in Stanislaus County. Aedes aegypti mosquitoes, which are invasive for the region, are capable of transmitting viruses such as St. Louis encephalitis, chikungunya, dengue, yellow fever, and Zika.
In contrast to the native amber-colored Culex mosquitoes, whose peak biting times are dawn and dusk, Aedes aegypti mosquitoes are black and white, bite aggressively during the day, and feed almost exclusively on humans. Additionally, the larvae of Aedes aegypti mosquitoes require much less water. Females lay their eggs just above the water line in small containers and vessels that hold water, such as dishes, potted plants, bird baths, ornamental fountains, tin cans, or discarded tires. The eggs can survive for up to eight months after the water dries out.
Most people infected with St. Louis encephalitis do not have symptoms, according to the CDC. Those people who do become ill may experience fever, headache, nausea, vomiting, and tiredness. Some people may develop neuroinvasive disease, such as encephalitis or meningitis. In rare cases, long-term disability or death can occur. There are no vaccines to prevent or medicines to treat St. Louis encephalitis.
The mosquito abatement districts encourage residents to dump and drain any standing water around their property.
“Preventing opportunities for mosquitoes to breed around your home can help protect you and your family," said David Heft, the general manager for Turlock Mosquito Abatement District. "Take a moment to look around your property and dump and drain any items with standing water that can allow mosquitoes to develop.”
In cases of larger amounts of standing water such as neglected swimming pools, ponds, water troughs, or ornamental ponds, the districts encourage residents to place mosquitofish in them. Residents may contact the Turlock or Eastside Mosquito Abatement offices to arrange for mosquitofish pickup or delivery.
The Districts will continue with their surveillance programs identifying mosquito breeding sources and mosquito borne disease activity. They will treat according to their surveillance results. The Districts anticipate more WNV and mosquitoes in the coming months and would like to remind residents they can help by taking the following precautions:
• Dump or drain standing water. These are places mosquitoes like to lay their eggs.
• Defend yourself against mosquitoes by using repellants containing DEET, Picaridin or Oil of Lemon Eucalyptus.
• Avoid being outdoors at dusk and dawn. These are the times when WNV carrying mosquitoes are generally most active.
•Report neglected swimming pools to your local mosquito abatement district.
• Use tight fitting door and window screens to keep mosquitoes from entering your home.
• Contact your veterinarian for information on vaccinating equine against WNV.
For additional information or to request service, residents should contact their local District Stanislaus County MADs:
• North of the Tuolumne River contact: Eastside Mosquito Abatement District at (209) 522-4098 (www.eastsidemosquito.com)
• South of the Tuolumne River contact: Turlock Mosquito Abatement District at (209) 634-1234 (www.turlockmosquito.org)
Reporting and testing of dead birds are important steps in preventing West Nile Virus. A confirmed case of the virus in dead birds or mosquito samples helps to identify areas that need treatment to reduce mosquito activity. To report a dead bird, call the California State hotline at 1-877-WNV-BIRD or report it online at www.westnile.ca.gov. Birds of particular interest are crows, ravens, magpies, jays and raptors (hawk or eagle).