Surveillance

Shasta Mosquito and Vector Control District constantly monitors mosquito numbers, environmental conditions, and disease occurrence in order to make the best possible decisions about appropriate levels of mosquito control within the District. For current surveillance numbers, please check Disease Updates and Vector Populations.

Mosquito Surveillance8 “New Jersey” Light traps are distributed throughout the District from April through October. These traps are collected weekly and the mosquitoes are identified and counted to provide an accurate assessment of mosquito populations throughout the District all through the mosquito season. 

In addition, the District runs 60 CO2 baited EVS traps throughout the District aimed at collecting live mosquitoes on a weekly basis that are sent to the state lab to be directly tested for the presence of encephalitis viruses. Detection of virus activity in the District prompts intensified and focused mosquito control to ensure the protection of the health of residents in areas where the risk of the spread of the disease is high.

Finally, the District deploys “Gravid traps” in various locations to catch mosquitoes for virus testing. These traps are designed to collect mosquitoes that are “gravid” or carrying eggs. The gravid female mosquitoes seek out the stagnant water in the trap for depositing their eggs and get sucked into the trap by a fan. This type of trap is very good for collecting Culex Pipiens mosquitoes, a potential vector of West Nile Virus. Since these mosquitoes must have blood-fed in order to produce eggs, they are more likely than non-gravid mosquitoes to have acquired mosquito-borne diseases from an infected host.

Tick SurveillanceShasta Mosquito and Vector Control performs annual surveillance for Ixodes pacifcus and Dermacentor sp. ticks, attempting to establish abundance trends, and provide residents with areas of heightened public concern. Ticks have the potential to vector such diseases as Lyme disease, Anaplasmosis, Babesiosis, Ehrlichiosis, Rocky Mountain Spotted Fever, and Tick-borne relapsing fever. For additional tick information, read more about ticks as vectors.

Dead Bird SurveillanceDead bird surveillance is another tool to monitor the presence and spread of viruses in the environment. Reports of dead birds have declined in recent years and this number continues to wane. In 2018, the District received 37 dead bird reports and 5 of the 9 tested were WNV positive. For information on reporting a dead bird, you can find out more here.

Sentinel Chicken SurveillanceSentinel chickens have long been used in California to detect diseases circulating in the environment. Chickens are used for a number of reasons including ease of care, and they do not suffer any adverse effects due to infection. District staff monitored five flocks of eight chickens each located throughout the District from rural Cottonwood to central Redding. Blood samples were taken from each bird between April and October every two weeks. The California Department of Public Health tested the sample for immune response to mosquito-borne diseases. In 2018, 4 of the 40 chickens tested were found to have been exposed to West Nile virus.

Rodent SurveillanceRodents, like rats, mice and ground squirrels have the potential to transmit disease within Shasta County, so Shasta Mosquito and Vector Control conducts limited disease surveillance in conjunction with public education to help reduce the risks of contact with wild animals. Rodents in California have the potential to transmit: hantavirus, arenavirus, leptospirosis, rat bite fever; and through fleas, plague bacteria. For additional rodent information, read more about rodents as vectors.