The Scientific-Technical Services staff is part of a comprehensive approach to protecting public health. Their surveillance program utilizes a variety of field and laboratory techniques to monitor mosquito-borne diseases, as well as population densities of mosquitoes, black flies and midges.
Disease surveillance efforts detect West Nile virus (WNV), St. Louis encephalitis (SLE) and Western Equine encephalomyelitis (WEE) in mosquitoes, as well as antibodies for infections in wild birds and sentinel chickens. Mosquito and sentinel chicken blood samples are shipped to the UC Davis Center for Vectorborne Diseases (CVEC) for analysis.
The department is headed by a Scientific-Technical Services Director and staffed by four full-time Vector Ecologists, one Assistant Vector Ecologist and part time Field Assistants.Read more about mosquito-borne diseases
The disease surveillance program serves as an early warning system in the detection of mosquito-borne viruses that can infect people and animals. Monitoring diseases allows the District to be more efficient and timely conducting control efforts and outreach to affected communities.
The District’s response level is based on a set of guidelines provided by the California Department of Public Health (PDF), reflecting the level virus transmission risk to humans.See the latest West Nile virus statistics
Disease Surveillance Testing
Testing for the presence of virus/pathogens in mosquitoes, sentinel chickens, and dead birds helps identify the disease transmission risk before human cases occur.
Sentinel chickens provide the early warning system that allow the District to effectively communicate potential threats to the public. It also facilitates an unbiased assessment of the severity of a disease outbreak due to the very consistent yearly efforts.
Blood samples from captured free-ranging wild birds are taken bi-weekly to obtain sera samples and analyzed by the UC Davis Center for Vectorborne Diseases (CVEC) for the presence of WNV, SLE and WEE antibodies. The amount of antibodies in birds is important. The more antibodies present in birds, the less likely the diseases can spread. This is because their immune systems is more likely to fight off an infection. Birds are captured, bled and release unharmed.
Since these mosquitoes are seeking a blood meal they are less likely to be infected than the mosquitoes seeking a place to deposit eggs (see Reiter-Gravid Trap). During mosquito season, traps are set overnight at fixed locations throughout the District to capture mosquitoes.
Unfortunately, due to the very smelly nature of the yeast infusion, almost exclusively Culex quinquefasciatus (southern house mosquito) are attracted to these traps. The southern house mosquito plays an important role in the transmission of WNV to the human population. Like EVS traps (above), these traps are placed late in the afternoon and collected the following morning.
The ovitrap simulates a container, such as a plant saucer or bucket. It has a special cardboard-lined wall which stimulates egg-laying and is filled with water. A mosquito attracted to this trap will lay her eggs on the artificial lining of the cup. A vector ecologist will retrieve the lining and inspect the material for eggs.