Los Angeles County West Vector & Vector-Borne Disease Control District

About the Los Angeles County West Vector & Vector-Borne Control District

    The Los Angeles County West Vector & Vector-Borne Disease Control District (District) was formed in 1944 and contained about 5 square miles. Over the next 56 years, there have been a number of annexations into the District. The District covers approximately 640 square miles, contains 23 cities and unincorporated territory of the County of Los Angeles, and provides services for 3,480,000 people. This makes the District the second largest vector control district in the state of California by population served.

    The District includes the cities of Agoura Hills, Beverly Hills, Calabasas, Culver City, El Segundo, Hawthorne, Hermosa Beach, Hidden Hills, Inglewood, Lawndale, Lomita, the westerly portion of Los Angeles City, Malibu, Manhattan Beach, Palos Verdes Estates, Rancho Palos Verdes, Redondo Beach, Rolling Hills, Rolling Hills Estates, Santa Monica, Torrance, West Hollywood, Westlake Village, and unincorporated territory of the County of Los Angeles. The District is governed by a Board of Trustees. Each city and county within the boundaries of the District may have representation on the Board. This is an example of government by local representation.

    Vector control is necessary on a continuous routine and area-wide basis to protect the health and enhance the economic development, recreational use, and enjoyment of outdoor living.

    With the emergence of new diseases and vectors locally (Lyme disease, mosquito-borne encephalitis, Africanized honeybees & Red Imported Fire ants) and nationwide (Dengue hemorrhagic fever in Texas and the West Nile virus throughout the nation), surveillance work and control measures have taken top priority throughout the United States.  Reducing and controlling the number of vectors, that are able to spread and amplify these diseases or inflict pain or injury,  is the focus of vector-borne communicable disease programs.

    Presently, the District's main focus is the surveillance and control of mosquitoes, Africanized honeybees and Red Imported Fire ants, along with the monitoring of ticks and Lyme disease.

    While impossible to eliminate all mosquitoes, numerous methods are employed to keep their numbers as low as possible. Vector control districts employ an integrated management program to reduce mosquito populations and keep the diseases they can transmit under control. Surveillance includes intensive field monitoring, laboratory testing, and research studies on the newly emerging and previously known mosquito-borne diseases. Control methods include a myriad of procedures. Among them are public education, the elimination of standing water, and the use of a variety of environmentally sensitive biological controls, including mosquitofish.

    During the 1983 mosquito season, two cases of St. Louis encephalitis (SLE) were reported in Los Angeles County, of which one resided in the geographical boundaries of the District. This marked the first record of SLE in Los Angeles County since the 1940's. In 1984, an epidemic of SLE occurred; sixteen cases and one death were reported.  In 2003, the West Nile virus first appeared in California and Los Angeles County. By the end of 2004, there were 830 human infections and 28 deaths throughout the state and 2539 human infections across the nation. St. Louis encephalitis (SLE), Western Equine encephalomyelitis and the West Nile virus (WNV) are now endemic in Los Angeles County with local wild bird populations serving as the reservoir for these viruses.

    In 1998 the first tick in Los Angeles County known to carry Lyme disease was found in the Santa Monica Mountains. Since then, a number of other locations have produced positive ticks for Lyme disease. The tick that has the potential to carry the infectious agent for Lyme disease, the western black-legged tick (Ixodes pacificus), can be found throughout mountainous and rural areas within the District.

    In November 1998, the first Africanized honeybee (AHB) colony was discovered in Lawndale, a city within the District's boundaries. By April 6, 1999, the entire 4,083 square miles of Los Angeles County was declared colonized. The District currently receives over 7,000 service requests per year for AHB hive and swarm removal during the spring, summer, and fall.

    An essential program of the District includes educating the public about the life cycle of the mosquitoes, ticks and bees, diseases carried by these vectors, property owners' responsibilities, and functions of the District. General public education is accomplished through the use of informational brochures, fact sheets, city bulletins, public speaking engagements, informational booths at local fairs and public service announcements.

    District staff has distributed thousands of pamphlets on mosquitoes, Africanized honeybees, Lyme disease, and other vectors. Additionally media and service group packets and videos describing services of the District, backyard breeding, bee preparedness and other vector-borne diseases have been widely distributed. Public service announcement tapes are routinely distributed to all local cable stations and written public service announcements are distributed to local radio stations.

    District staff has implemented an education program in the public and private elementary schools. The District conducts mosquito control, bee, and tick education problems education program through a cooperative effort with the teachers. The District provides each class with student and teacher workbooks, puzzles, book marks, necessary slides, videos and visual aids. District staff trains the teachers and encourage them to administer the program yearly as part of their science education.

    The District has indoctrinated the residents of the District to coexist with the Africanized honeybees utilizing cable television, lectures, and community bulletins. The District has been the lead agency in training and coordinating fire departments, police departments, and 911 systems throughout the District. The education program includes speaking engagements at schools, clubs, other organizations, and businesses.

    The primary goal of the District is the control of mosquitoes by preventing them from breeding. Although this is more time consuming, more difficult to accomplish, and more costly over a short time span than other control methods, a preventative program will be more cost-effective to the District over the years. The District is now becoming involved in the review and make recommendations on environmental impact reports that will prevent the construction of areas (sumps, improperly graded channels, etc.) that may support the breeding of mosquitoes and other vectors.

    Another important aspect of prevention is education of the residents through contact with field staff. When staff inspects an area, a notice will be left to inform the resident that a technician has been present and will list the findings and the action taken. District staff will make every effort to personally speak to the residents to explain the need for mosquito control activities.

    Staff also provides education to residents on how to bee proof their home and surrounding area in an attempt to decrease "home sites" for the Africanized honey bee.

    Although District staff attempt to eliminate breeding sources, the need for biological and chemical control of mosquitoes is necessary. The District has been divided into zones which are routinely inspected and treated. Each zone has been assigned a technician who inspects known sources, answers service requests, and searches for new sources associated with the request.

    When a breeding source is found that cannot be permanently abated, the technician will determine the best method of treatment. The preferred method of control is the use of biological control agents. The main biological control agent used by the District is the mosquito fish, Gambusia affinis.

    If the source cannot support Gambusia affinis, staff will then use larvicides to control mosquitoes before they emerge as adults. The District treats sources with either Bti or Altosid Liquid Larvicide (methoprene). Both of these chemicals are safe to the environment and target specific.

    Africanized honeybee swarms and nests are removed when requested by citizens or emergency response units who feel their safety or the public's safety is in jeopardy. After the swarm and/or nest is removed, technicians will set remnant bee traps, if necessary, to collect those bees that were away from the nest. The remnant bee trap will be baited with a pheromone that attracts bees. The technician will return the following day and remove the remaining bees.

   Besides being nuisances, mosquitoes may transmit a number of communicable diseases. The diseases of most concern in the Los Angeles County West Vector & Vector-Borne Disease Control District are St. Louis encephalitis (SLE) and Western Equine encephalomyelitis (WEE). Since there are no cures or vaccines available for humans, surveillance for the presence of virus and controlling mosquitoes are the best methods for reducing the potential for human disease. The two main components of the District's mosquito surveillance program are sentinel chicken serology and the collection of mosquitoes.

    Sentinel chicken serology is performed by placing chickens in an area over a long period of time and testing their blood for the presence of antibodies to SLE and WEE viruses. The District maintains 18 flocks of chickens located strategically throughout the District. The chickens are bleed once ever two weeks during the months of April through October. Blood samples are processed and tested in the District's laboratory. By performing these tests "in-house", the District is able to sample more often and obtain results within 48 to 72 hours. Therefore, the presence of virus activity is identified earlier. Confirmation samples are sent to the State Laboratory for quality control. The results obtained from these tests are used to increase inspections and control measures in the areas where virus is present.

    Collecting adult mosquitoes can provide several important pieces of information. When traps are set at specific locations over a time period, or in response to service requests, increases in the mosquito population can be detected. Once these mosquitoes are identified, control measures can be directed towards those species which feed on man and may transmit SLE and WEE viruses. These mosquitoes can also be tested for the presence of virus. The detection of virus in a mosquito which feeds on man indicates a true potential for human disease, and immediate control measures can be implemented. Trap collections not only determine where control measures are needed, but also determine the effectiveness of control measures which are in place. Mosquitoes that are capable of transmitting SLE and WEE viruses are pooled and sent to the State Viral and Rickettsial Laboratory for testing.

    Staff sample and identify bee collections using the Fast Africanized Bee Identification System (FABIS). The District also has an active yellow jacket surveillance and control program. During the year 2000, the District will begin conducting in-house microscopic identification of the Lyme disease borrelia in ticks via IFA technology.

    The District also identifies arthropods for residents of the District and for physicians. Surveillance of other vectors and diseases may be conducted at a future date. Future surveillance of vectors may include, but is not limited to, spiders, rats and fleas. Future surveillance of diseases may include, but is not limited to, plague, hantavirus, murine typhus, West Nile virus, and Dengue hemorrhagic fever.

    Vector-related problems decrease property values, affect residents, and lower the overall economic potential of a community.

    Obvious economic losses due to mosquitoes biting include loss of weight by livestock, illness, or loss of life by disease or physiological reaction in man and domestic animals, or simply intolerable nuisance levels. Such factors can destroy the economy in large areas, greatly reduce productivity, and drive many residents away. When exposed to high vector annoyance, livestock fail to feed and gain weight profitably.

    The previous incidence of malaria in many countries so debilitated the population that national productivity was reduced to 40% of estimated capacity due to this mosquito transmitted disease.

    The enormous cost of medical care and the loss of life where vector-borne diseases are prevalent represent significant economic loss. One study examined the economic burden imposed on residents of Massachusetts who had survived Eastern equine encephalitis infections. Transiently affected persons mainly required assistance of direct medical services; the average total cost per case was $21,000. Those who suffered persistent sequelae remained at home and seemed likely to live a normal life span, but without gainful employment. The cost associated with persistent sequelae, which included medical expenses, education, institutionalization, and loss of income, was approximately $3 million per case. Major losses may occur to recreational interests, tourist trade, real estate and land development, and to other associated local business, when an area gets a reputation for being infested with vectors.

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