Shasta Mosquito & Vector Control District
(This information also available in a pdf brochure)
BACKGROUND
In response to endemic
malaria, the Redding
Mosquito
Abatement District was established in 1919 and was followed by the formations of the Anderson, Clear Creek and
Cottonwood Mosquito Abatement Districts in the 1920's. During
the 1950's the four districts were consolidated to create the Shasta Mosquito Abatement District.
Two annexations occurred
in the mid-1970's which added 48 square miles from the Palo Cedro and Balls Ferry areas, to make a
130 square mile
district. In March of 1994, the District changed its name to the Shasta
Mosquito and Vector Control
District to better reflect its services. In 1995, the District annexed the
Shasta Lake, Keswick, Shasta, Centerville, Cloverdale, Happy Valley, Olinda,
West Cottonwood, Coleman, Millville, Bella Vista, Mt. Gate and Jones Valley
areas. With this annexation the District comprised approximately 384
square miles. In 2007 the District annexed Lakehead, Castella, French
Gulch, Igo, Ono, Shingletown and Viola therefore the District now encompasses
approximately 1,086 square miles in Shasta County.
PUBLIC HEALTH
Mosquitoes are an important “vector” under the definition used by the California Department of Health Services. A vector is an insect or other arthropod that transmits disease or discomfort to humans, their pets and livestock. Other important vectors include fleas, which can transmit important diseases such as bubonic plague, and ticks, which transmit Lyme disease and other important human diseases. Mosquitoes are the most important vectors of human disease worldwide. Annually about 1.5 million people throughout the world are killed by mosquito-borne malaria alone. Mosquitoes also transmit such health problems as canine heartworm, which can threaten our pets and livestock. Other important diseases that are transmitted by mosquitoes to man include dengue hemorrhagic fever, yellow fever, and a number of types of encephalitis. Several types of encephalitis, which range in severity from flu-like symptoms to coma, paralysis, brain damage and death, are found in nature in wild bird populations in California. Shasta Mosquito and Vector Control District’s main efforts are focused on assuring that mosquito numbers within the District remain low enough to keep the transmission of encephalitis from birds to man unlikely.
MOSQUITO SOURCES
Although we normally think of mosquitoes as small, flying and blood-sucking insects, they actually live three quarters of their life cycle in standing water sources. Mosquitoes go through a complete metamorphosis, just like butterflies, with an egg, larva, pupa and adult stage. Eggs are laid on or near the surface of standing water. The tiny shrimp-like larvae and pupae live in the water until the adults emerge from the pupae and fly off to seek a blood meal. Since standing water sources are more confined and easier to locate than flying adult mosquitoes, Shasta Mosquito and Vector Control District concentrates most of its efforts on locating these juvenile mosquito sources. Depending on the particular source, District personnel may work to eliminate the standing water or kill the mosquitoes that are living there. There is a whole spectrum of sources where mosquitoes breed within the District. Larger sources include such things as river and stream isolations, ponds and reservoirs, canal seepage, ditches, catch basins, swamps, sloughs and intermittently flooded areas such as irrigated pastures and riparian habitats. Smaller sources often go unnoticed in residential and industrial settings, and may include such things as leaky pipes, discarded tires, plugged rain gutters, bird baths, cans, buckets, wading pools, pool covers, wheel barrows, basements, tree-holes or almost anything that can conceivably hold even a small amount of standing water for more than a couple of days. Since adult mosquitoes may fly for miles from these sources, it is necessary for the Shasta Mosquito and Vector Control District to control mosquitoes in all types of sources wherever and whenever they occur within the District. Also, any effort made by residents within the district to clean up items around their homes and businesses that may hold water and breed mosquitoes, benefits themselves and other people over a very wide area.
PHYSICAL CONTROL
Shasta Mosquito and Vector Control District conducts a multi-faceted approach to controlling mosquitoes and protecting public health within the District. The portion of that work which involves eliminating mosquito sources, improving access to these sources, or modifying sources to discourage mosquito breeding and encourage the growth of natural mosquito predators is called physical control. In the early days of mosquito control in the U.S. large public works projects were undertaken to drain swamps for malaria prevention. Because of the importance of these wetlands as wildlife habitat, this sort of massive alteration of the environment is very uncommon nowadays. We do spend quite a bit of time maintaining existing drainage systems to assure that water flows freely to discourage mosquito breeding. Other physical techniques that we use to reduce large mosquito breeding include making banks of holding ponds steeper to discourage emergent vegetation, removal of brush and berry bushes that provide cover to mosquito larvae, and construction and maintenance of roads that provide access to known mosquito sources that cannot be eliminated, such as isolations along the Sacramento River. Many of the access roads within the District, which are commonly used by the public, from fishermen to bird-watchers, have been historically built and maintained by the Shasta Mosquito and Vector Control District. Another important aspect of physical control within the District involves source prevention. Our personnel review plans for large construction projects within the Shasta Mosquito and Vector Control District to be sure that they will not adversely affect natural runoff and create new mosquito sources. Cleaning up rubbish that may hold water, ditch maintenance, periodically changing bird-bath water, and cleaning rain gutters are all physical control measures that everyone can take around their homes to decrease the health risk and annoyance caused by mosquitoes.
MOSQUITO CONTROL CHEMICALS
Another aspect of our comprehensive, modern and integrated approach to mosquito control is chemical control. The Shasta Mosquito and Vector Control District uses a variety of environmentally compatible chemicals to control mosquito larvae and adults without causing harm to non-target organisms. Some of our products for larval control are based on unique bacteria, which produce protein substances that kill mosquito larva but are completely non-toxic to all other insects and other animals. Insect growth regulators, which interrupt the mosquito’s life cycle, are also used. Other chemicals are applied which float on the surface of the water and prevent the mosquito larvae from obtaining air to breathe. Adult mosquitoes are killed using ultra-low-volume aerosol applications of modern pyrethrin-based chemicals. The District has five weather stations which are used to assure that application of chemicals to control adult mosquitoes takes place when conditions are right to get the maximum effectiveness against mosquitoes while having the least possible adverse effects on the environment. All of the mosquito control products used by the District are easily biodegradable and do not persist in the environment.
BIOLOGICAL CONTROL
Mosquito control is achieved in persistent water sources from ponds to watering troughs through the use of the mosquitofish Gambusia affinis. This small relative of the guppy was originally discovered in The Gulf Coast area. Since its discovery in the 1920’s it has been released worldwide for mosquito control to the point that it is now the most widely distributed freshwater fish in the world. Shasta Mosquito and Vector Control District raises mosquito fish, which are given out free of charge to residents within the District for control of the mosquito’s aquatic life stages. Our integrated pest control methods also encourage natural mosquito control by discouraging growth of mosquito larvae while encouraging the survival and proliferation of natural mosquito predators.
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. 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. Since encephalitis diseases occur more frequently in bird populations than among humans, five sentinel chicken flocks are kept in different areas of the District to monitor encephalitis virus activity. Blood samples are taken from the chickens every two weeks and sent to a state lab to be tested for the presence of antibodies to encephalitis viruses. Also live mosquitoes are trapped and 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.
SERVICE REQUESTS
Since the Shasta Mosquito and Vector Control District has been in existence since 1919 we have many years of experience locating and dealing with mosquito sources throughout the District. However, we have rather limited manpower to cover a very large area. Therefore, we depend on input from our constituents to keep us informed about new mosquito problems as they arise. If a resident fills in our online service request form or calls in to the District to report a mosquito problem a technician will contact them and make an on-site inspection to assess the nature of the problem and the source of any mosquitoes, and prescribe an appropriate course of action to bring the best possible control of the situation. Since our services are paid for through tax revenues, there is no additional charge to our constituents for our response to service requests.
The Shasta Mosquito and Vector Control District provides a large assortment of pamphlets and other materials containing helpful information about mosquitoes, other vectors of human pest importance, diseases of concern, and general pest control. In addition we have biologists on staff to answer questions, write articles, give interviews to the press and talk to schools and civic organizations about all issues related to public health pest control.
For More Information:
(530) 365-3768