This deadly virus was found in Merced County for the first time in decades
A chicken in Merced County has tested positive for St. Louis encephalitis virus for the first time in decades, the mosquito abatement district reported.
St. Louis encephalitis can cause people to have mild flu-like symptoms. In more serious cases, symptoms could include seizures, paralysis, a coma and could even result in death. The virus has no specific treatment.
“The sentinel chicken sampled that tested positive for (the virus) is the first detection of the virus in Merced County in over 40 years,” said Rhiannon Jones, general manager of the Merced County Mosquito Abatement District. “We were surprised we didn’t find it in a mosquito first. It does send up some red flags for us. We’re going to increase our surveillance and testing.”
The chicken was found outside of Gustine last month, and the mosquito abatement district received confirmation yesterday that the bird tested positive for the virus.
To date, 30 mosquito samples in eight California counties have tested positive for the virus this year. The only chicken to test positive so far was the one found in Merced County. Last year, there were three human cases of St. Louis encephalitis in California. Those were the first human cases in 20 years.
Older adults and people with a weakened immune system are more likely to develop severe symptoms of encephalitis.
In addition to encephalitis, 20 mosquito samples, five chickens and one dead bird have tested positive for West Nile virus in Merced County.
Both viruses are carried by the same Culex mosquitoes and are controlled by the same surveillance and abatement methods, said David Heft, general manager of Turlock Mosquito Abatement District.
St. Louis encephalitis was a virus historically controlled by mosquito abatement districts in California before West Nile virus came on the scene about 15 years ago. St. Louis seemed to disappear after West Nile became the dominant virus, but it has reappeared in some counties in the last two or three years, Heft said.
Heft said the flooding earlier this year resulted in large numbers of Culex mosquitoes, which may carry St. Louis and West Nile, and “that is helping to drive (the St. Louis) virus.” Mosquitoes spread the two viruses by biting an infected bird and then biting a person.
Officials anticipate encephalitis and West Nile vius detections will increase in the coming months. Residents should make sure to drain standing water, use repellents with DEET, Picaridin, or Oil of Lemon Eucalyptus, avoid being outdoors during dawn and dusk and report neglected swimming pools.
To report mosquito-breeding problem areas and request service, call 209-722-1527 or 800-622-3242. Anonymous calls are accepted.
This story was originally published August 16, 2017 at 2:05 PM with the headline "This deadly virus was found in Merced County for the first time in decades."