April ushers in spring gardens and warmer weather … and it also marks the time when West Nile virus begins appearing.
Managers at mosquito vector control districts are offering suggestions on how residents can keep an eye on their property and help protect themselves.
“With warmer temps forecast for this week and next, it’s a great time for residents to go through their yards looking for any kind of container that may be holding water,” said Stephen Abshier, manager of the Sutter-Yuba Mosquito and Vector Control District. “Even though we haven’t had significant rain in some time, people are turning on their sprinkler systems to water lawns and plants.”
He said irrigation water can fill up the smallest of containers, which provide a good breeding spot for mosquitoes.
“It takes very little water for a mosquito to lay eggs in, develop through their immature stage and emerge as a flying adult mosquito,” he said. “The fewer mosquitoes that are able to reproduce in the early part of the season will correlate to a dramatic overall reduction in the numbers that build through the season and into the fall.”
David Whitesell, Colusa Mosquito Abatement District manager, asks that people refrain from over watering their lawns to the extent that water will run off into the street gutters and remain standing.
“Water is necessary for three of the four life stages of the mosquito. The egg, larvae, and pupae are aquatic. The fourth stage is the adult mosquito,” Whitesell said. “In the summer the four stages of the mosquito life cycle may require as few as three to four days, while in cooler periods of the year they require several weeks to become adults.”
Both districts are monitoring swimming pools and people can call their respective district to request a free inspection of their pool and staff have resources to help minimize the risks.
“The District does have a limited amount of mosquito fish available to residents within the District boundaries,” Whitesell said. “Anyone wishing to receive fish is asked to call the district in advance and to bring their own containers for transportation.”
“An unmaintained green pool is of great concern because the mosquito species responsible for West Nile transmission will breed in unmaintained backyard pools and spas,” Abshier said. “District staff can take care of most any mosquito breeding problems with a quick visit for an inspection and when needed, a treatment.”
California’s dead bird program is in full effect and the public can call the hotline if they find a dead bird. The dead fowl are often markers of the presence in the area of West Nile virus -- an infectious disease spread by mosquitoes that usually has little to no effect on people, but in rare cases can cause extreme illness and even death.
“If the hotline accepts the bird, district personnel will pick the bird up to be tested,” Whitesell said.
In May, an aerial contractor will fly over the Yuba-Sutter area to photograph suspect pools and later, staff will visit those homes to inspect and treat pools that are producing mosquitoes.
“We want to be clear that we don’t collect or distribute any information about what may be in a resident’s yard that is unrelated to mosquito production,” Abshier said. “We do everything we can to make our pool visits as non-intrusive as we can, respecting people’s privacy and property. There is no fine or penalty for an unmaintained pool.”
Abshier said there are mosquito abundance traps that provide data on the mosquito population throughout the district and the numbers are low, which is normal for this time of year.
“We also maintain seven chicken flocks in different places in the district, known as sentinel chicken flocks,” Abshier said. “Every two weeks through the mosquito season, a tiny blood sample is collected from each chicken and submitted to a lab. They are looking for antibodies in the chicken blood sample that would confirm the immune response in the chicken to the virus infection.
Another method of detecting the virus is through collecting and submitting mosquitoes that are trapped in the field for this purpose. Labs are able to isolate mosquito-borne diseases including West Nile virus, Western Equine Encephalitis and St Louis Encephalitis.
Whitesell said humans and horses are all susceptible to the virus along with birds.
“A vaccine is available for the horse and is highly recommended as infected horses have nearly a 50-percent mortality rate. No vaccine exists as yet for humans,” he said. “Of people infected by WNV, about 80-percent show no symptoms whatsoever. About 20-percent have West Nile fever, developing common flu-like symptoms: nausea, fever, body aches, mild skin rash, and swollen lymph nodes.”
He said West Nile fever can be debilitating with recovery taking weeks or months. WNV can be severe in the elderly and those with low immune systems.