Purpose of the District

One of the first things to recognize is that mosquito control is a year-round public health profession activity and its branch of science is Culicidae Entomology. Mankind’s battle with the mosquito has existed for centuries. This persistent insect caused the first building of the Panama Canal to fail, when thousands were infected by mosquito-borne yellow fever. Millions more have died in other parts of the world from malaria and dengue-virus.  In the U.S., mosquitoes have infected many people with encephalitis, causing death or permanent disability. Mosquito-borne diseases cause more than a million deaths each year around the world.

Closer to home, everyone has had the experience of being driven indoors or retreating from a picnic in the park because the mosquitoes decided it was time to feast. Clearly put, mosquitoes continue to be a major health and nuisance/comfort problem.

An Integrated Pest Management program (IPM) is the proven approach to mosquito control by reducing mosquito populations and, with it, the threat to public health and discomfort. This multi step process is a systematic approach to control all phases of mosquito growth and infestation. The information that follows provides a general picture of the activities that are needed for the program over the course of a year.

PRE- OR OFF-SEASON ACTIVITIES:

General Issues
Many activities of the mosquito control program are normally carried out in the “off season” when mosquitoes are not normally active – usually during the winter. These activities include staff training and certification; equipment purchase, repair and calibration; budgeting and other financial activities; and analysis of the previous year’s data. In some areas, source reduction activities are done at this time. Much of the information collected during mosquito control activities consists of maps, tables, and charts. Most of the information is linked to a physical location. For this reason, it is vital to have a mapping program available to the mosquito control program. This can be done by coordinating with another city or county department that already has a geographical information systems (GIS) section or activity. This part of our program is in the working stage with a cooperative effort of Franklin County GIS and our District.

Surveillance
Surveillance, as applied to vector-borne disease, is the organized monitoring of levels of virus activity, vector populations, and infections in vertebrate hosts, human cases, weather, and other factors to detect or predict changes in the transmission dynamics of arboviruses. Since all of this information is rarely collected by a single agency, it is extremely important that the various data-collecting agencies actively communicate and exchange information.

  • Review all published data, past health department records, and other data to determine the types of mosquito borne diseases, numbers of cases by year and date of onset (or diagnosis), economic and other costs, if known. Review complaint calls for nuisance mosquitoes by year and date, and determine the peak periods of nuisance problems.
  • Collect and review historical meteorological data for the area: temperature, rainfall, humidity, and wind direction. Plot this information against mosquito abundance (or nuisance calls) to see if there are any predictors of high mosquito abundance, disease transmission, etc.
  • Map the locations of high-risk populations (e.g., elderly citizens), using local census or other community data. This allows our program to prioritize resources if an epidemic should occur.
  • Collect and review topographic maps, aerial photography, and other similar resources to help in locating probable larval habitats, concentrations of bird or other hosts of mosquito-transmitted viruses.
  • Use the data collected above to decide where to place light traps or other sampling stations, and where to concentrate efforts to monitor larvae.
  • Based on the foregoing information, select the areas at greatest risk within the service area (city, district, county, etc.) and plan to concentrate the available resources in those areas.

In some respects, a mosquito control program can be compared to a military campaign: it is crucial to know the enemy. The more that is known about the important species in the area, the more likely they can be effectively and economically controlled.

  • Habitat mapping. The off-season is the best time to map the locations of larval habitats within the mosquito control district. It may also be useful to map major sources of mosquitoes that may be located outside the boundaries of the control district, if these are known or suspected sources of problems during the mosquito season.
  • Seasonal characteristics.  Off-season is the time to take the opportunity to construct graphs of seasonal abundance of mosquitoes, by species. This is also done for larval surveys as well as adult surveys. Over several years, it will be possible to construct an average count for each species, by week. When the current counts for a particular species rise above the long-term average, this may indicate an emerging problem.

 

Control Activities
This is the most visible part of the program, but its success is strongly dependent on attention to the points covered above.

  • Source reduction. Several types of source reduction can be carried out during the off-season: clearing of stream channels, community cleanup (e.g., door-to-door inspections, tire amnesty programs), and similar activities.
  • Larval control. Most control is done later in the season, but some areas are treated before they become flooded by spring rains, irrigation or runoff.
  • Adult control. Adult mosquito control is not done at this time, unless emergency control is needed.
  • Public education. Public education, especially activities focused on K-12 school programs, can be carried out at any time of the year as well as arrangements  for presentations at meetings of civic groups, nature groups, service clubs, and other groups that have an impact on the local community.

EARLY-SEASON ACTIVITIES:

Surveillance
In early-season activities, as above, the surveillance program gathers the intelligence data needed to combat the mosquitoes and prevent disease transmission.

  • Larvae. With the arrival of spring warming, rain, irrigation  or flooding, Aedes and Ochlerotatus mosquito eggs will hatch, and diapausing Culex female mosquitoes will emerge, take a blood meal, and begin laying eggs. This is the time to begin monitoring larval populations and take appropriate control actions.

 Interim:

  • Adults. Similarly, light traps, gravid traps, or other methods are used regularly to monitor adult mosquito abundance. Triggers for control action are determined: by how many females per trap night of a particular species pose a health threat or a nuisance problem.
  • Disease surveillance. Vertebrate hosts (e.g., dead birds as indicator for West Nile virus) are monitored for evidence of virus activity. This may be simply recording and mapping the locations of dead birds reported by the public. Depending on other resources, the local health department, a state laboratory or other facility may be available to perform virus testing on dead birds.

Virus assay kits for testing dead birds and mosquito pools are used in the District’s in-house insect laboratory. Mosquito infection rates are an important indicator of a disease threat. The state health laboratory is also available to provide this service. Infection in domestic animals (horses, etc.) and humans is an indicator of impending trouble and an indication that immediate action is required.

  • Habitat mapping is continued during the course of the mosquito season. New locations are plotted on the map and entered into the GIS database. New locations are added to the inspection and treatment routes of the field staff.
  • Seasonal abundance characteristics can give us evidence of approaching problems. For example are the numbers of Culex tarsalis and pipiens far above normal? Is Aedes vexans more abundant than normal?

Control Activities

  • Source reduction. Activities can continue during this period. Efforts should concentrate increasingly on the elimination of potential disease vector species larval habitats.
  • Larval control. Biocontrol agents, such as mosquito eating fish (Gambusia affinis) can help in WDFW approved locations to balance out a good control program. “Biological pesticides” such as Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus are effective mosquito control agents.
  • Chemical control of larvae includes a variety of materials. Larvicidal oils and monomolecular films cover the water surface and prevent the larvae from breathing. Growth regulators, such as methoprene, affect the development of the mosquito larvae, preventing the adult from emerging from the pupa.
  • Adult control. Selective uses of adulticides are needed when there is evidence of virus activity early in the season, or if nuisance species are at high levels.
  • Public education. Newspaper, radio, and television announcements are prepared to increase public awareness of the threat of mosquito-transmitted disease. Coordination with local media increases the community’s awareness of the types of work done by the mosquito control program.

MID- AND LATE-SEASON ACTIVITIES:
During this period even more effort is dedicated to larviciding and, as needed, adulticiding. Disease surveillance data guides the level of mosquito control, especially control of adult mosquitoes. Public education and close contact with media resources is continued. As mosquito populations decline with the onset of cold weather, our program returns to the pre-season/off-season routine, in preparation for the next year.

ELEMENTS OF A COMPREHENSIVE PROGRAM:

  • Continue measures established in the program described above. Augment public education and source reduction efforts.
  • In collaboration with other relevant agencies and stakeholders, define the full scope of the program.
  • Encourage feedback and communication between the program and relevant stakeholders.
  • Hire and train appropriate professional staff needed to fulfill the requirements of the program.
  • Procure the necessary equipment, chemicals and other materials needed to carry out the program.
  • Build on the existing monitoring program, establishing a long-term database for comparison to current year data.
  • Prepare an emergency response plan for dealing with vector-borne disease outbreaks.
  • Increase disease surveillance activities by mosquito testing or other techniques as appropriate.
  • Build risk maps to assign priorities to areas within the district using census data, mosquito abundance data, disease incidence and other relevant data.
  • Maintain good communication among the Centers for Disease Control and Prevention, state public health and local public health agencies.
  • Evaluate the governmental disease surveillance network.
  • Evaluate and improve the disease reporting system among physicians, hospitals, laboratories and public health agencies.
  • Develop and maintain a responsive animal and vector disease reporting system among veterinarians, wildlife agencies, the public, mosquito control contractors, laboratories and state and local public health agencies.
  • Keep the public and public officials informed regarding disease incidence projections, cases identified and response planning.

 

INFORM THE PUBLIC:
Mosquito control programs need the support of an informed public. Many of the successful strategies for control involve individuals, their families and their neighborhoods. The public also has concerns about the problems related to the mosquito populations and about insecticides and spraying. Keeping the public informed leads to a stronger, better supported program that is tailored to the community and its values. Our communications plan includes public education about preventing the breeding of mosquitoes, personal protection guidance, and the activities and success of the District and other agencies involved is critical to the success of our program.

DEFINE THE GOALS FOR PUBLIC INFORMATION:
The public information challenges of mosquito control are many. Mosquito control includes two areas of responsibility: individual and public. Areas of individual responsibility relate to personal actions residents can take to reduce personal risk from mosquitoes, such as eliminating breeding pools on their property and using insect repellants. Public responsibility relates to the development and maintenance of community-wide mosquito control activities and programs.

Public information strategies will vary based on which area of responsibility is being impacted and the goal to be achieved. The information needs vary depending on whether the goal is to:

  • Educate policy makers and gain their support for policy issues
  • Inform the public about mosquito control generally
  • Provide instructions to the public to prevent exposure and lower risk
  • Deal with a public health crisis, such as West Nile virus
  • Inform the public of pesticide risks and benefits
  • Inform the public about the use and timing of pesticides in their areas
  • Gain support for financial resources for mosquito control

 

A respected spokesperson should be identified. This may be the local health official or another public official with credibility and profile in the community. The spokesperson(s) could come from academia, the medical community, the local hospital, or public health. The lead agency at the local level will want to designate a public information officer or team to develop materials, inform the press, respond to questions, and network with information officers in related organizations, such as emergency medical services, hospitals, county or city manager’s offices, the state, etc.

Strategies to inform the public can include press education prior to the mosquito season; educational meetings with policy-makers such as city councils and county commissioners; preparation of materials for the public; web-site development; plans for a hotline and recorded messages; and regular information to the public about mosquito surveillance and disease incidence.

 

CREATE EFFECTIVE MESSAGES:
A proactive approach will involve developing a simple message, easily understood that resonates and is memorable. Many states have already initiated public health campaigns such as the 2003 “Fight the Bite” campaign. When developing campaigns, it is important to have a unified message across the state. Other public health campaigns may serve as models for community awareness. A successful campaign:

  • Utilizes web sites, public service announcements and information hotlines as tools for community education and involvement
  • Develops multiple strategies to reach people at home, work, school, in shopping areas and in places of worship
  • Provides succinct messages to the public throughout the year and emphasizes prevention as the best protection against illness
  • Assures that programs are sustainable even in the absence of mosquito-borne illness in the community

 

INFORM THE PUBLIC – PLANNING AND ACTION CHECKLIST:

  • Develop an information exchange process that will keep the public in tune with decisions and anticipated actions
  • Determine who should be included in the public information network to plan for the information campaign or campaigns. What sister agencies or neighboring jurisdictions need to be involved?
  • Decide if there will be proactive press education prior to the mosquito season
  • Determine who will develop and update web sites. What links will be established?
  • Decide what specific information can be given to the public about the use and timing of pesticide applications
  • Identify language barriers that need to be considered when developing campaigns
  • Anticipate objections to the program by a minority opinion that may be vocal enough to disrupt the project or lead to minority reports
  • Establish a follow up mechanism such as a survey to determine the success of education and outreach
  • Develop a pre-season campaign to educate the public
  • Designate a spokesperson to handle medical questions and work with the coroner’s office and the hospitals if death and/or illness occur
  • Prepare fact sheets for physicians and the public
  • Educate key decision-makers
  • Maintain statewide data and coordinate information campaigns with a single, unified message to the public on prevention of mosquito-borne illness.

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