West Nile Virus Response Plan

Transcription

1 West Nile Virus Response Plan West Nile virus (WNV) is spread by the bite of an infected mosquito. Since 1999, when the first U.S. outbreak occurred on the East coast, the virus has spread across the United States. WNV will present a considerable challenge, in part due to minimal historical data on mosquitoes in King County. In order to launch and sustain a science-based and appropriate response, data about mosquito habitats, breeding seasons, effective control mechanisms and other relevant information are required to tailor King County s response to our community. It is important that the King County WNV plan be flexible so that as more knowledge is gained on WNV we are able to formulate and modify appropriate responses. For background information on WNV see Appendix A. Links to additional information may be found in Appendix B. The plan has three main components Education, Surveillance, and Control. Laws and regulation are also briefly addressed. The plan provides a science-based, regional framework to control WNV. While Public Health Seattle & King County (Public Health) is the County lead for WNV response coordination, the plan addresses actions to be taken by other county agencies including the Departments of Natural Resources and Parks (DNRP), Transportation (KCDOT) and Development and Environmental Services (KCDES). For other jurisdictions and for private lands the plan provides suggested strategies. Education Public Health Education is the key Public Health strategy and role. We are developing messages both for the public as well as for partner agencies to distribute. When new WNV staff are hired, an education and outreach program will be developed. A media strategy is also planned. The key messages for the public address risk, habitat reduction, personal protection and mosquito avoidance. Community Outreach Identify audiences (at-risk populations, Healthcare for the Homeless Network, shelters, soup kitchens, outdoor recreation stores, realtors, gardening stores and groups, etc.). Spring Develop a distribution plan. Spring April

2 Respond to s and phone calls from the public (Public Health is already receiving a large volume of s from concerned residents). Send materials when requested. On-going Visit each suburban city and drop off materials. Spring Provide materials, outreach visits, presentations to major groups. Spring - fall Work with cities to create WNV presentations for city personnel to deliver. Provide other information/be a resource. As needed. Update WNV video. As needed Update and add educational materials. On-going PH Veterinarian: serve as departmental leader in a team facilitating activities related to WNV. Give presentations to appropriate audiences. Work with zoos. On-going Develop guidance related to mosquito control for homeowners. On-going Provide media response and messaging. On-going Pest Control Operators (PCOs) Develop a list of contacts for internal use. Spring Make available the latest information to PCOs. On-going Identify capacity in the PCO industry to address anticipated control work needs. Spring Supply PCOs with information to bring to consumers, act as PCO resource. Spring Medical Provider Education Public Health s Communicable Disease Control, Epidemiology and Immunization section will develop educational materials and information for health care providers on recognition, reporting, diagnosis and management of WNV cases. On-going Internal Audience King County Letter from Executive Sims to County employees regarding WNV and personal protection April Continue to meet with County agency partners in a working group; advise on habitat reduction on county properties. On-going KCDNRP, KCDOT, DDES and Executive Services (KCES) These departments will have Public Health and other materials for distribution to staff and residents. As needed Surveillance Surveillance (larval, adult mosquito, bird/mammalian, and human) will be critical in the coming months. Larval surveillance is key for control work. Tracking adult mosquitoes may provide additional information about areas with mosquito infestation. Adult trapping allows easier identification. Bird surveillance provides information about arbovirus activity, perhaps in geographically discrete areas. For a list of potential WNV mosquito vectors in King County, see Appendix C. April

3 Larval surveillance Public Health Increase larval collection to more than 50 samples (last year s level) Spring/summer Advise cities to do larval surveillance on their own properties, link them with the state DOH, who will provide training On-going Work with Farm Management program on volunteer surveillance On-going Enter data into GIS database As received Analyze data from database to help predict where larval control work should be done On-going Facilitate meetings between cities and state DOH to increase overall county larval surveillance Spring Procure mosquito surveillance equipment. Spring KCDNRP and KCDOT Staff may be asked to gather information on larva numbers captured at various King County-owned locations in the unincorporated areas of the County. Information will be gathered as part of a routine investigation of a mosquito complaint, during larval control efforts, during routine maintenance activities, or at the request of Public Health. Adult mosquito surveillance Public Health Develop a database to receive new complaints and incorporate previous complaints. Data will be entered into the database for GIS mapping. In place mid-march Adult trapping, driven by clusters of bird deaths or other data. As needed Field visits to some complaints-- one-on-one property-owner education. Spring - Fall Limited enforcement is possible through solid waste regulations. KCDNRP and KCDOT Mosquito trapping surveillance may be carried out by County agencies or other entities at the request of the Public Health. As needed Mosquito complaint calls will be summarized on a weekly or monthly basis. Information collected will include name, address, parcel number, and comments that will be sent to Public Health for inclusion in their tracking system. On-going Dead bird surveillance Public Health Increase the number of dead crows collected (per state DOH resources). Focus on the collection of freshly dead birds (deceased less than 24 hours). Rapid detection and collection of dead birds provides quicker results for surveillance. April

4 Administrative staff will enter dead crow reports into database for GIS mapping. As needed Human Surveillance Public Health Public Health s Communicable Disease Control, Epidemiology and Immunization section will conduct surveillance for human cases of WNV among persons with compatible illness in accordance with Centers for Disease Control and Prevention and the Washington State Department of Health protocols. Health care providers in King County will be informed of the details of the surveillance system in late Spring. Control The intent of mosquito control is to address health issues related to mosquito borne diseases, in this case WNV. Public Health is not recommending that topical mosquito control be undertaken for nuisance control or aesthetic reasons. Public Health will continue to respond to mosquito nuisance complaints by providing information on ownerinitiated mosquito control. King County s Integrated Pest Management policy is intended to limit the use of pesticides and encourage the least toxic agents, and low impact methods where possible. Accordingly, this plan does not recommend mosquito control in sensitive areas such as wetlands. Several methods of control are being considered, including reduction of artificial habitats and larvicidal agents to kill immature mosquitoes. Under extreme circumstances adulticides may be considered but since they are less effective, more toxic, and often require aerial spraying, adulticides are a last option. Larvicides, often in the form of briquettes or pellets, are applied to aquatic areas where mosquitoes lay eggs. Permits and licenses are required to apply larvicides to state waters (essentially any body of water that drains or connects to a natural water body). Public Health will not do any control work except for habitat reduction on its own properties. Public Health s main control function is to provide a scientific framework and advice to governmental and other entities for control work on their properties. Habitat reduction Public Health Education. On-going. See Appendix F, Basic Recommended Actions for details. Limited enforcement might be possible through solid waste regulations. Field visits based on complaints -- one-on-one property-owner education. Spring - fall April

5 KCDNRP, KCDOT and KCES In addition to parks, King County government owns and maintains solid waste facilities, wastewater facilities, about 1400 storm water drainage facilities, 30,000 catch basins and many miles of roadside drainage ditches in unincorporated King County. As a major property owner, King County government s activities will address habitat reduction as described in Appendix F, Basic Recommended Actions, habitat modification, potential facility modifications and repairs. 1. Habitat Modification Habitat modification ranges from removing potential small artificial habitat such as containers to changing the physical features of a facility. County agencies are responsible for managing any County owned or maintained property and will follow the same basic mosquito control measures being recommended to the public. See Appendix F for a list of typical recommended actions. 2. Physical Modifications or Repairs. The first consideration at any facility with artificial mosquito habitat should be whether it is practical for the problem to be reduced by physical modification or repair. See Appendix F for a description of these efforts. Larval Control Public Health Public Health will offer advice but will not perform or pay for control work. County and other government property owners will be advised to examine and assess habitat for larva presence (especially catch basins, retention ponds, other bodies of water) and to possibly do larva control when larvae are present. Possible criteria for larviciding include: 1. proximity to housing 2. densities of populations over age community concerns voiced 4. incidence of mammalian/bird cases. Public Health has no legal authority to require jurisdictions to control habitat and conduct control work. Public Health will assess what each city/agency is doing. Spring-fall Public Health will not require private property to owners to apply larvacide, but will offer options and advice that can be used based on specific circumstances. On-going Public Health will facilitate workshops for cities to understand county efforts, explain processes related to licensing and permitting. March - April Public Health will evaluate larviciding efforts to assess efficacy of method. Winter 2003/2004 April

6 KCDNRP, KCDOT, and KCES Aside from habitat reduction, two options for killing mosquitoes exist natural (predator) control and artificial control. For information on the possible vector species found at various facilities, see Appendix D. 1. Natural Control One long-term strategy is to introduce natural predators, which feed on mosquito larva. Any future decision to do this will be made in cooperation with the Washington Department of Fish and Wildlife (WDFW). See Appendix F for details. Natural predators include amphibians, such as frogs or salamanders, and insects such as water beetles or dragonflies, birds, and bats. 2. Larvicidal Agents Any pesticide application to the waters of the state requires an NPDES permit prior to beginning any control actions. King County is applying for an extension of the Washington State Department of Health coverage under the existing Washington State Department of Ecology Mosquito Control NPDES permit which was issued in The KCDNRP s Water and Land Resources Division (WLRD) has reviewed the evidence available and is recommending that there is a benefit to providing early limited larvicide treatment at selected stormwater ponds. This recommendation is based on: 1) The recommendation by the State Department of Health; 2) Consultation with Public Health Seattle & King County; 3) The results of the technical memo drafted by the WLRD Science Monitoring and Data Management Section Ecological Assessment of three Larvicides for Mosquito Control in Stormwater Ponds (dated March 7, 2003); and 4) The results of 2002 stormwater pond study that indicated the presence of a primary vector species. The best time to control mosquitoes is when they are in the larval stage. There are several products that can be used to control mosquito larva. Based on the information available for the ecological assessment, the preferred larval control agents to be used on County properties are: Bacillus thringiensis israelensis (Bti) and Bacillus sphaericus (Bs). Methoprene products, Monomolecular surface film (MMF), and Golden Bear Oil are products covered under the permit applied for by the State Health Department. Since methoprene impacts other aquatic insects and potentially some fish, its use by KCDNRP will be limited to extremely rare cases or a significant outbreak of the WNV. See Appendix E for a description of each larva control measure. Facilities will be selected for potential treatment if they meet the following criteria: 1. There is water in the facility with mosquito larva present, or adult mosquitoes attempting to lay eggs. 2. The pond is adjacent to residential or commercial buildings. 3. The pond is located in an area of concern with regards to the number and density of residents over 50 years of age. April

7 4. No natural predators are apparent or the mosquito population exceeds a minimum of 0.3 larvae per dip sample in spite of the existence of natural predators. 5. Habitat modification or natural controls are not practical or have not had a chance to take effect. Based on these criteria, KCDNRP will begin a larviciding program on selected stormwater ponds as needed throughout the mosquito season Similarly, a KCDOT program to larvicide its storm water ponds would be conducted as needed throughout the mosquito season. There are over 30,000 catch basins in the KCDOT road right-of-way located primarily throughout the urban unincorporated area. Treatment of all of these facilities would be cost prohibitive. Control activities for catch basins will be based on the criteria listed above. The preferred method of control at catch basins will be vactoring. Laws and Regulations There are no current BOH or other local regulations dealing with mosquitoes. Some enforcement of mosquito habitat minimization may be possible through solid waste code (i.e., where solid waste is the primary violation and mosquito habitat is also present). The King County Board of Health will review regulatory options in April. Budget Appendix I contains Public Health, DNRP, and DOT estimates of costs needed to implement this plan. Costs may increase as the season progresses and WNV related conditions change. April

8 Appendix A West Nile virus background West Nile virus (WNV) is an arbovirus (arthropod borne virus) that is transmitted to birds and mammals through the bite of an infected insect, generally mosquitoes. Birds, especially those of the Corvid (crow) family frequently act as a host to the virus and can pass it back to an uninfected mosquito. Mammals do not appear to be able to transmit the virus back to mosquitoes. The majority of people and animals who acquire the virus have mild flu like symptoms that frequently go unnoticed. However, of those who do become symptomatic, a small percentage may develop a form of encephalitis, which can be fatal. West Nile Virus first appeared in the U.S. in 1999 in New York. Initially, it was diagnosed as St. Louis encephalitis. Prior to its introduction in the U.S., West Nile Virus has been present in Europe and Africa since its first discovery in WNV is related to St. Louis encephalitis, which has been present in the U.S. for decades. According to the U.S. Center for Disease Control, approximately 1 in 150 people infected develop a severe illness. The case counts for the U.S. since the introduction of the disease is: Year No. of States Clinical Cases Deaths DC DC * 44+DC The disease is also known to affect several hundred species of birds and mammals. Most notable are horses and corvid birds (crows, jays, etc.) * 2002 Case count as of April

9 Appendix B Additional resources More information on WNV and links to related web sites can be found through the following Internet links: Washington State Department of Health: Washington State Department of Health WNV response plan: Public Health Seattle & King County: U.S. Center for Disease Control: King County Department of Natural Resources and Parks Environmental Risk Program at Cornell University: Information from EPA on insect repellent containing DEET April

10 Appendix C Possible West Nile virus vector mosquitoes in King County To date, eight species of mosquitoes in King County have been associated with the West Nile Virus. Two of the eight species are considered to be the most likely vectors for WNV once it arrives in King County, these are culex pipiens and culex tarsalis. The other species have been associated with WNV positive tests, but may not be efficient carriers of the disease. Pending the results of additional research, King County control efforts will focus on the culex species. A brief description of each species follows and Appendix D shows the habitat types and the associated vector mosquitoes favoring each habitat. Knowing the preferred habit for each species of mosquito can help determine the best management strategy. The following information is taken primarily from Darsie and Ward (1981) and Meyer and Durso (1998). Culex pipiens, the northern house mosquito, occurs in foul water with a high organic content, such as catch basins and stormwater ponds. It is a primary vector of St. Louis Encephalitis and has been implicated in the transmission of dog heartworm. Females feed at dusk or after dark, readily enter homes and prefer avian hosts, but will also feed on large mammals, including man. This species occurs throughout the northern United States and Washington. Culex tarsalis, the western encephalitis mosquito, may be found in any standing fresh water, especially around agriculture. It is the most important vector of arborviruses in western North America. It prefers to feed on birds, but will also feed on large mammals and man after birds are done nesting. This species is widespread in North America and may be found at all elevations. It is an important encephalitis vector where that disease is present. Aedes vexans, the inland floodwater mosquito, occurs in all types of floodwater situations, including roadside ditches and mud puddles, temporary pools formed by flooding in creek bottoms, and water pooling from irrigation. Eggs may lie dormant in soil 3 years or more, until the area becomes wet again. Some do not hatch until re-wetted several times. Adults are good fliers and capable of dispersing 5-15 miles from where they emerge. This species is likely present in many stormwater ponds, is a vicious day biter but rarely enters homes, and is widespread throughout North America. Aedes cinereus is a woodland species, usually found in permanent bogs and marshes. The larvae are secretive and tend to hide among aquatic vegetation or under leaves. Adults emerge primarily in early spring and are known as ankle biters because they tend to attack people around the lower legs. They are aggressive biters but often are not noticed because people are distracted by other species in their face. This species is widespread in North America, except in the arid southwest. Anopheles punctipennis, the woodland malaria mosquito, prefers algae-laden pools along the edges of slow moving streams and rivers. This species rarely enters homes, tends to be a night biter, and attacks man outdoors in woodland or foothill situations. April

11 It is found throughout Washington State and is widespread throughout much of the U.S. and North to central British Columbia, Canada. It is likely to be found where springs or creeks are associated with stormwater ponds. Coquilletidia perturbans larvae occur in permanent marshes with emergent cattails and tulles. This species is unique because the larvae attach to roots and stems of aquatic vegetation and cannot be controlled with surface treatments like Bti or oils. Only products like methoprene are effective against this species. Adults are vicious biters and feed at dusk or after dark. This species has a single generation per year and is found throughout most of North America. Culiseta inornata, the winter mosquito, is an unusually large mosquito that occurs in a variety of sunlit habitats including ponds, irrigation or glacial runoff, rain pools, salt marshes or even artificial containers. It is an early season species and does not like hot weather. This species is widespread in North America at all elevations. Ochlerotatus japonicus larvae are found primarily in artificial containers or tree holes. This species was first identified in New Jersey in 1998 and has now spread to thirteen other states and Quebec, Canada. All other states where it is found are in the northeastern United States; the only western record is from King County, Washington. April

12 Appendix D Disease vector mosquito species associated with drainage control facilities Habitat Type Facility type Vector Species Permanent Water Year round wet ponds Larger Regional Ponds Wet Bioswales Anopheles punctipennis Culex pipiens Culex tarsalis Marshes & Wetlands Wet Bioswales Some Regional Facilities Adedes cinereus Coquilletidia preturbans Temporary or Flood Water Temporary Wet Ponds Dry Bioswales Retention/Detention Ponds Open Ditches Adedes vexans Culiseta inornata Culex pipiens Culex tarsalis Artificial Containers / Tree Holes Catch Basins Underground Tanks/Vaults Discarded containers & Tires Ochlerotatus japonicus Culex pipiens Culex tarsalis Culiseta inornata April

13 Appendix E Larvicidal control methods under consideration Bacillus thuringiensis israelensis (Bti) is a naturally occurring bacterium, which is used to disrupt the feeding abilities of aquatic fly larva. Bti is specific to fly larva and has little known impact on other species. In order for it to be effective the mosquito larva must ingest it, once the larva shifts to the pupae stage, Bti is no longer an effective control. Depending on the form of Bti used and water conditions, it has a residual life of 1 to 30 days. Bacillus sphaericus is also a naturally occurring bacterium, which disrupts the larva feeding abilities. Bs is best used in water with a high organic content. As with Bti, it is specific to fly larva and has little or no impact on other species. The residual life of Bs is 1 to 4 weeks. Methoprene is a chemical growth inhibitor, which prevents the mosquito larva from progressing to the adult stage. Since this chemical also may impact other insects and fish, it is not recommended for use where it will easily move into natural water bodies. Methoprene does not have to be ingested by the larva to be effective. Depending on the form of methoprene used, it has a residual life of 2 to 21 weeks. In a closed pond or a situation where there is little chance of outflow to natural water bodies, the long term version of methoprene may have a good cost/benefit ratio since it may be effective for most of a breeding season. This would reduce the need for staff to reapply pesticides through the summer months. Monomolecular surface film (MMF) is a pesticide that forms a thin layer on the water surface and makes it difficult for the mosquito larva to maintain its position at the water surface where it needs to be to breathe. In addition, adult mosquitoes trying to land on the water surface to lay eggs will become trapped in the water and drown. Although MMF has little impact on fish and other invertebrates, it will affect other insects that rely on a water surface tension. This is a reasonable method to use where a rapid impact is desired. It is not effective on the coquilletidia perturbans mosquito larvae that attach to cattails for breathing. This control agent is not suitable in windy conditions where the material will be dispersed by water movement. Golden Bear Oil is a light oil that can be sprayed onto the surface of the water. The thin layer of oil clogs the breathing tube and suffocates the larva and pupae. This is effective on both the larva and the pupae, but it also impacts other aquatic organisms. Use of Golden Bear Oil should be kept to a minimum. As with MMF, it is not suitable for windy conditions. April

14 Appendix F Mosquito control measures 1. Basic recommended actions Empty anything that holds standing water, such as old tires, buckets, plastic covers, and toys. Change water in birdbaths, fountains, wading pools and animal troughs weekly. Remove unused containers bottles, cans, and buckets that may collect water. Make sure roof gutters drain properly, and clean clogged gutters in the spring and fall. Fix leaky outdoor faucets and sprinklers. 2. Habitat reduction/physical modifications or repairs When considering a facility for mosquito control, the first consideration should be whether the problem could be reduced by physical modification. In general this is not going to be a practical alternative for drainage facilities. Most facilities serve water quality and flow control functions, with specific design features to enhance those functions. Modifications to the features may compromise the function. Physical modifications must be designed or reviewed by an engineer to insure they meet applicable design requirements. Possible design modifications may include changes to the flow rate, enabling the facility to drain sooner; eliminating low spots, which collect small amounts of standing water; or removing vegetation. Alternatively, if a pond can be deepened or made into a permanent wet pond, the conditions for natural predators may be enhanced. Repairs may include scarifying the pond bottom where it is no longer infiltrating as originally designed, reshaping the pond slopes to eliminate isolated pools of water, and cleaning the pond to remove inappropriate vegetation. Mosquitoes will use the lifting hole in the access covers for catchbasins, tanks, and vaults to get into the structure and either breed or shelter from the heat of the day. If possible they should be denied access by covering the hole with a Tracy Patch, which is a piece of duct tape covering the hole. When the tape is removed to access the structure it should be replace with a fresh piece of tape. 3. Natural control options: The WDFW is investigating whether there are native minnows or fish that may be appropriate for introducing into ponds or wetlands which may not have a native population established. WFWD may also approve the use of gambusia (mosquito fish), which are a non-native species, but only in situations where they will not escape to natural waterways. April

15 Appendix G Focusing the response Surveillance and control efforts will be prioritized based on indicators of the level of risk expected to be experienced by specific areas or locales. Indicators of increased risk include combinations of these factors: The documented presence of West Nile virus (WNV) in an area or locale; Concentrations of dead crows or birds that might indicate the presence of WNV prior to laboratory confirmation; Concentrations of people over 50 years of age, the age group most vulnerable to WNV infection morbidity; Concentrations of people whose circumstances increase their mosquito exposure (e.g. unsheltered homeless, outdoor activity participants such as play-field and park users and outdoor concert attendees); Concentrations of complaints concerning adult mosquitoes or breeding habitat; Proximity to shallow, still bodies of water that can provide mosquito breeding habitat; and Other factors identified as knowledge of WNV evolves. Areas or locales will be ranked using the above risk-related indicators. Those ranked most highly will be the main focus of surveillance and potential control efforts. In addition to focused surveillance, geographically representative sampling of mosquito breeding habitat will be attempted in both urban/suburban and rural areas as county and external resources allow. Nonprofit organizations, such as equestrian groups, may be encouraged to assist with surveillance in rural communities. April

16 Appendix I West Nile Virus Projected Cost 2003 (Grand Total is $915,982) $273,322 $375,041 Education Control $267,617 Surveillance $84,586 Projected Cost By Agency 2003 PUBLIC HEALTH $260,389 $571,005 NATUARAL RESOURCES AND PARKS TRANSPORTATION April