LAKEPORT – Routine surveillance has detected West Nile virus in two dead birds and two mosquito samples in Lake County, signaling an unusually late start of the West Nile virus season in Lake County.

Local health officials said Thursday that the bird and mosquito findings serve as reminders that local residents and visitors should remember to take appropriate precautions to avoid mosquito bites, which is the way that West Nile virus (WNV) spreads to humans.

The first WNV-positive dead bird was an American crow collected in Lucerne on July 1. The next WNV-positive dead bird was an immature Western scrub jay collected in the city of Clearlake on Aug. 5.

Two samples of Western Encephalitis mosquitoes (Culex tarsalis), both collected near Upper Lake on Aug. 18, were reported positive for WNV Thursday morning.

West Nile virus first arrived in California in 2003 and in Lake County for the first time in 2004, officials reported. The virus infects humans, birds, tree squirrels, horses and humans and is transmitted through the bite of infected mosquitoes. Once established in an area, it has the potential to cause illness in humans.

In 2008, there were no confirmed human cases of West Nile virus in Lake County, but there was one case of illness in a horse and the virus was detected in dead birds, mosquitoes and in a sentinel chicken flock that is tested routinely.

The low incidence of West Nile virus disease in Lake County residents can be attributed to vigorous efforts to control mosquitoes, according to the Thursday report. While mosquitoes are an important part of the environment and cannot be completely eliminated, the reduction of heavy mosquito populations near places where people live and recreate is an important disease prevention measure.

In addition, people must take personal responsibility to avoid mosquito bites by wearing protective clothing, using appropriate mosquito repellants, and staying indoors during morning and evening hours when mosquito activity is high.

Most (approximately 80 per cent) of people who catch West Nile virus do not show any symptoms. About one in five infected people experience fever, headache, body aches, nausea, vomiting, and occasionally swollen lymph glands or a skin rash. These symptoms can last for a few days, but sometimes continue for weeks.

About 1 in 150 cases of West Nile virus will develop severe illness, which can lead to disorientation, coma, tremors, convulsions, muscle weakness and other neurological symptoms, sometimes resulting in death.

There is no specific treatment for West Nile virus, nor is there a vaccine for humans, officials reported.

According to the Lake County Public Health Officer, Dr. Karen Tait, “The best way to stay healthy during West Nile virus season is to prevent exposure to mosquito bites. Avoiding West Nile virus infection involves both personal protection against bites and reduction of environmental breeding grounds for mosquitoes. These are precautions that need to be taken every year.”

A lot of people assume that since this has been a dry year and the lake level is low that there are no mosquitoes, but that has not been the case. The Lake County Vector Control District reports that mosquito activity – particularly for the Culex mosquitoes that transmit WNV—has been very high in some localized areas of the county.

The Vector Control District has been regularly trapping and testing mosquitoes throughout the county to identify the areas that are at highest risk, and target those areas for source reduction and treatment.

Lake County Vector Control District Manager and Research Director, Jamesina J. Scott, Ph.D., asks residents to maintain their pools to prevent mosquitoes, and to let the District know of unmaintained swimming pools and spas.

“An unmaintained swimming pool can produce hundreds of thousands mosquitoes per week, and those mosquitoes can fly up to five miles away. So a single neglected swimming pool can increase an entire community’s risk of mosquito bites and mosquito-borne illness,” Scott said.

The Lake County Vector Control District can put mosquito-eating fish into pools that will be out-of-service for a month or more, or use biorational control products like Bti, a bacterial spore that controls mosquitoes without affecting other plants or animals that use the water.

Residents can call the district at 707-263-4770 to report neglected swimming pool or to request mosquito fish, mosquito inspections or mosquito control services.

For more information, visit http://www.cdc.gov/Features/WestNileVirus/ or www.westnile.ca.gov/ .