Response Plan Policy Statement
Lewis County will prepare for the possible arrival of the West Nile Virus by:
- Adopting the Washington State Mosquito-borne Disease Response Plan (November 2002) as a framework for developing a local response that is consistent with Washington State agencies and other jurisdictions;
- Adopting Ecology’s Best Management Practices for Mosquito Control (March 2003) to determine appropriate control measures
- Developing a local response Plan that identifies specific or unique activities for Lewis County and roles and responsibilities, using the Guidelines For A Phased Response section of the state plan as a template.
Three key Components in responding to mosquito born disease:
Public Information:
Enhanced public awareness and prevention education are two important strategies to address mosquito-borne diseases in Lewis County. These strategies can promote public cooperation and personal responsibility in reducing man-made mosquito habitat and using personal protection. Health care providers can also be informed about the diagnosis and treatment of human arboviral encephalitis.
A public health education campaign about mosquitoes and arboviruses should accomplish the following objectives:
- Encourage personal protection techniques, such as appropriate dress, use of insect repellents, and minimizing outdoor activities between dusk and dawn.
- Improve public understanding of the sources and reservoirs of arboviral diseases such as mosquitoes, birds, and mammals.
- Increase awareness among the public and health professionals of the potential risk for infection with arboviral disease locally and when traveling to other areas.
- Encourage health care providers to promptly report cases of human encephalitis.
- Improve knowledge among health care providers of the signs and symptoms of human arboviral encephalitis.
- Public information messages increase community awareness of agency activities and provide suggestions about property maintenance and personal protection. Requests for public help in observation and reporting of dead birds tend to increase participation and awareness.
Surveillance:
Lewis County will conduct surveillance in four primary areas: mosquitoes, birds, horses, and humans.
Mosquito surveillance is an essential component of a comprehensive mosquito-borne disease prevention and control program. Lewis County will survey for the species of larvae and apparent increases in larvae to assist in determining appropriate habitat reduction and mosquito control responses. Lewis County will also monitor for adult mosquitoes at selected locations. As part or the Plan, Lewis County will identify areas where surveillance is to be conducted. There are nine potential West Nile Virus mosquito vectors in Western Washington. Six of those species have been identified in Lewis County. Information about those six species is provided in the table below.
West Nile Mosquito Vectors in Lewis County
Table 1
| Species | Preferred Larval Habitat | Typical Flight Range | Biting Habits | Significance |
|---|---|---|---|---|
| Aedes cinereus | Woodland pools, cattail swamps | Does not travel far | Aggressive day biter | Low |
| Anopheles punctipennis | Usually woodland pools, may be in artificial containers | Does not travel far | Aggressive day and biter, bite cows, horses, humans | Med |
| Culex pipiens | Polluted water, artificial containers, stormwater | Usually does not travel far | Night biter; feeds on birds, mammals including man and dogs | High |
| Culex tarsalis | Ponds, ditches, marshes, artificial containers | Several miles | Primarily an evening biter; prefers birds, but will bite man & livestock | High |
| Culiseta inornata | Wetland pools, any stagnant water, artificial containers | Does not travel far | Bites at dawn & dusk; serious pest of livestock | Medium |
Birds and mammals surveillance can be important indicators for mosquito-borne viruses and may provide early warning to allow for appropriate actions to prevent human cases and reduce impacts on livestock, pets, and wildlife. Avian morbidity/mortality surveillance appears to be the most sensitive early detection system for West Nile virus and should be a component of every arbovirus surveillance program. The surveillance system should include two components:
1. Submission of selected individual birds for testing.
2. A reporting and mapping system for sightings of dead or ill birds and for birds found to be positive for WNV.
The effectiveness of dead or ill bird reporting will be enhanced by collaboration with groups and individuals most likely to find dead or ill birds, such as agencies whose employees spend considerable time out of doors (parks, fish and wildlife, public utilities, etc.) and members of birding and outdoor recreational organizations.
Avian surveillance should be initiated when local adult mosquito activity begins in the spring. The County anticipates beginning active bird surveillance A database should be established to record and analyze dead bird sightings with the following suggested data; caller identification, date observed, location, species, and condition. This information should be reviewed periodically to detect increases in avian mortality. Birds chosen for testing should have died within the last 48 hours and be in good condition with no decomposition or severe trauma. Birds from areas showing a general increase in observed bird deaths are of particular value. Crows, ravens, and jays should be emphasized for testing, as they are very susceptible to West Nile virus.
Horses have been found to be particularly susceptible to West Nile virus. Veterinarians in Lewis County should report equine encephalitis cases to the Washington State Department of Agriculture. This information will be forwarded to Lewis County’s West Nile Surveillance Data-Base and Mapping.
Human case surveillance is another important component of on overall mosquito-borne disease surveillance program. This includes the need to ensure rapid and complete laboratory diagnosis of all suspect cases. Human surveillance data should be evaluated together with mosquito, bird, and horse surveillance information to determine the Risk Categories and the efforts needed to prevent additional outbreaks of mosquito-borne disease.
To ensure detection of human outbreaks, enhanced passive surveillance for cases of encephalitis of unknown etiology should be implemented during the mosquito season (May through September). This passive surveillance is enhanced by general alerts to key health care personnel, such as primary care providers, infectious disease physicians, neurologists, hospital infection control personnel, and diagnostic laboratories. A high index of suspicion for arboviral encephalitis should be encouraged. Appropriate clinical specimens should be submitted from suspect human cases.
Active human surveillance should be initiated when information indicates the presence of arboviruses in mosquitoes, birds, or animals. This should include identifying physicians in appropriate specialties (e.g., infectious disease, neurology, and intensive care medicine) and hospital infection control personnel and contacting them on a regular basis to inquire about patients with potential arboviral infections. Physicians should be encouraged to submit clinical specimens from suspect cases.
The national case definition for arboviral encephalitis should be used to classify cases as confirmed or probable once laboratory results are available. Rapid sharing of surveillance results with agencies and the public is essential for development of appropriate disease control measures. This may be accomplished by using established networks of health care providers, internet sites, telephone hotlines, and press releases. However, confidentiality is important for bird and mammal testing as well as for human surveillance information. Identifying information should be protected including the animal owner’s name and street address, veterinarian’s name and address, name and address of individual or institution submitting a specimen, and in some cases, species of bird or mammal. Summary level information should be provided to the public by local health jurisdictions.
Control
Lewis County will use Ecology’s Best Management Practices for Mosquito Control to determine appropriate control measures. The county’s Plan stresses public education and information emphasizing personal responsibility in protection and removal or cleaning of outdoor containers of water. County initiated control activities will only occur at Risk Category 3 and above. Control will be limited to treating publicly owned man-made surface water facilities where the appropriate mosquito larvae have been detected and other surveillance criteria indicate treatment is appropriate.