WEST NILE VIRUS RESPONSE PLAN. Developed: December 2016 Revised:

Transcription

1 WEST NILE VIRUS RESPONSE PLAN Developed: December 2016 Revised: 1

2 Table of Contents Introduction... 3 Plan Summary... 3 Response Plan... 5 Information and Outreach Strategies Vector Index

3 Introduction West Nile Virus (WNV) appeared in the U.S. in 1999 in New York. Mosquitoes become infected with the virus when they bite a bird that's a carrier, and then the mosquito can pass it on to other animals - including humans, all of whom can become carriers. While the risk is low, the bite can lead to encephalitis, or an inflammation of the brain, which can be fatal. West Chester Borough has formed the West Nile Task Force (WNTF) to educate and bring awareness to the public on the importance of safe and effective means of mosquito prevention. The WNTF is comprised of Borough staff, elected officials, Borough citizens, employees of the Chester County Health Department and community stakeholders. The WNTF has been charged with developing a comprehensive response plan to limit the risk of West Nile Virus transmission by emphasizing prevention measures such as habitat control, larvicide application, public education and personal protection from bites. The plan identifies the roles and responsibilities of West Chester Borough, its citizens, and the Chester County Health Department regarding the strategies for mosquito prevention and control, reduction of sources of breeding, and sharing information about mosquitoes and the diseases they can transmit. The ultimate goal of the plan is to create a culture in West Chester Borough of awareness and prevention such that the need to consider WNV sprays is a last resort method of control. This plan aims to prevent both human illness related to WNV and pesticide exposure that can harm humans or other species such as beneficial insects. With the successful implementation of this plan, human illness related to WNV and exposure to pesticides will be prevented. The plan has been developed in collaboration between West Chester Borough, the Chester County Health Department and Don t Spray Me a citizens organization founded by residents of the Borough of West Chester that raises awareness about the dangers of pesticides and advocates more effective means of controlling mosquitoes such as larviciding; the group opposes mosquito spraying in Chester County citing studies on a lack of efficacy and harmful immediate and long term health effects on people and the environment. Plan Summary In the absence of effective human WNV vaccines, preventing disease in humans depends on application of measures to keep infected mosquitoes from biting people. The West Chester Borough West Nile Response Plan is a phased response plan that is grounded in prevention through breeding site reduction and larval control, and an educational campaign. Guided by the surveillance strategies, integrated efforts to control mosquitoes are necessary to maintain vector populations below thresholds that would facilitate WNV amplification and increase human risk. Failing that, efforts to reduce the abundance of WNV-infected biting adult mosquitoes must be quickly implemented to prevent Risk levels from increasing to the point of a human disease outbreak. Properly implemented, monitoring mosquito abundance and WNV activities in the vector mosquito population 3

4 will provide a warning of when Risk levels are increasing. Human surveillance on its own is not sufficiently sensitive to allow for outbreak control measures. The plan emphasizes the following principles: Responding to Actual Risk: For most people, the risk of contracting West Nile is very low. While there is need for caution, residents need not be overly fearful, and the Borough s response will reflect changes in risk throughout the mosquito season. Eliminating Mosquito Breeding Sites: Breeding source reduction is a very effective means of vector control which can be accomplished through public education and action to eliminate standing water. Controlling Mosquitoes at the Larval Stage: Larval control is critical in maturity to biting adult mosquitoes and as such vigilant surveillance and relatively non-toxic bacterial and insect growth inhibitor treatment should be a key strategy. Teaching Personal Protection Techniques: Broadly advertised in a thorough publicity campaign. Using pesticides as a last resort Assisting Higher Risk Groups: Addressing the needs of high risk groups for screen repair, gutter cleaning, and mosquito repellent. Public Education: Credible and accurate education is a continuous process that should begin before there is a public health threat. This response plan has been specifically designed and written for West Chester Borough and should not be assumed to be wholly applicable to other municipal areas within Chester County. 4

5 Response Plan The response plan below identifies and outlines the collaborative roles and responsibilities of West Chester Borough, its citizens and the Chester County Health Department relevant to surveillance, control measures, investigations and communication activities aimed at minimizing the health effects of West Nile Virus that can be transmitted through vectors such as mosquitos and birds. The Risk Level specifically identifies the transmission risk and the conditions that are present which trigger the corresponding actions to prevent an increase in transmission). The Vector Index included in the Risk Level is used as a guideline based upon national and state best practices. Please refer to the Vector Index section for an explanation of the index. Risk Level Vector Surveillance and Control Human Surveillance and Investigation Level 0 No Risk West Chester Borough assesses larval control inventory and secures assesses County-wide WNV plan Vector Index = 0 additional inventory as needed and secures funding Climate unsuitable for mosquito assesses County-wide WNV plan and activity secures funding Level 1 Low Risk Vector Index = No current surveillance findings indicating WNV activity conducts routine monitoring of mosquito populations monitors and investigates public complaints; physical or larvicidebased remediation of breeding sites shares relevant surveillance data from West Chester Borough West Chester Borough assesses, monitors for human cases communicates relevant surveillance data from West Chester Borough Information and Outreach West Chester Borough develops communication campaign to include goals, objectives, strategies, messaging, logo slogan, etc. West Chester Borough engages the Chester County Health Department, citizens, businesses, and neighboring municipalities in communication plan and development of campaign materials as applicable West Chester Borough initiates communication campaign with emphasis on mosquito awareness, personal protection, identifying and eliminating breeding sites using 1 to 2 mass communication outlets Citizen block captains canvass the Borough providing approved education and building community awareness about their role in 5

6 Risk Level Vector Surveillance and Control Human Surveillance and Investigation monitors and treats catch basins, marshes, pump stations, storm inlets, water treatment plants, streams, etc. with larvacide as applicable Citizens report dead bird sightings on-line at the Pennsylvania Dead Bird Surveillance program for West Nile virus ( rting/) engages with Pennsylvania Dead Bird Surveillance program as appropriate Risk level 2 Minimal Risk Risk level 1 activities Risk level 1 activities Vector Index = increases surveillance in area of WNV-infected mosquito/bird to One laboratory confirmed assess spread of virus WNV-infected mosquito Citizens monitor standing water pool/bird throughout the Borough, educate residents and report to Public Works Department West Chester Borough Public Works Department and/or County Health Department implements physical or larvicide-based remediation as applicable Level 3 Moderate Risk Vector Index = Rise in the number of laboratory confirmed WNV-infected mosquito samples/birds and consistently high number of Risk level 2 activities assesses surveillance data from neighboring areas for patterns in mosquito population and WNV infection considers barrier spray around waste Risk level 2 activities Information and Outreach mosquito control Risk level 1 activities West Chester Borough updates website with relevant information for citizens West Chester Borough initiates public information campaign with emphasis on recognizing the signs and symptoms of WNV, and the importance of personal protection for high risk groups (immunosuppressed, elderly, etc.) West Chester Borough distributes 6

7 Risk Level Vector Surveillance and Control Human Surveillance and Investigation mosquito populations water treatment plants if mosquito population is growing around the plant Level 4 High Risk Vector Index = Continued rise in mosquito populations and laboratory confirmed WNV-infected mosquito samples/birds in the same sampling area as compared to Risk level 3 over multiple sample periods or one laboratory confirmed case of WNV in a person who lives, works, recreates, attends school in West Chester Borough Risk level 3 activities increases surveillance in area of human positive to assess spread of virus; physical or larvicide-based remediation of breeding sites assesses need for adulticide control in collaboration with Pennsylvania Department of Environmental Protection Risk level 3 activities Reviews laboratory reports Investigates for possible source of infection Information and Outreach Bti larvicide samples (as available) for use in standing water on private property and West Chester Borough staff discuss use of barrier spray for waste water treatment plants if relevant West Chester Borough staff inform elected officials of elevated risk factors and reviews response plan activities to date educates West Chester Borough staff and elected officials on spread of virus and considerations to further minimize/eliminate spread; based upon mosquito and human surveillance data, environmental conditions, etc.; all considerations will be based upon mosquito and human surveillance data, vector index, environmental conditions, effectiveness of control measures already implemented West Chester Borough elected officials and staff meet with Chester County Health Department to finalize next steps including those needed in the event of progression to level 5; community alert from the Borough and letter from the Mayor are developed as appropriate. West Chester Borough issues 7

8 Risk Level Vector Surveillance and Control Human Surveillance and Investigation Level 5 Very High Risk Vector Index = 801 & above Continued rise in mosquito populations and laboratory confirmed WNV-infected mosquito samples/birds in the same sampling area as compared to Risk level 4 over multiple sample periods or more than one laboratory confirmed case of WNV in a person who lives, works, recreates, attends school in West Chester Borough initiates standard adulticide spray protocol to include use of adulticide in a manner consistent with EPA requirements, lead truck that warns citizens in the spray area, etc. Risk level 4 activities Information and Outreach community alert to prepare residents, including high risk groups (immuno-suppressed, elderly, etc.), particularly in the event adulticide spraying is needed. Alert should include explanation of decision factors, notification process, what to do if spraying occurs, personal protection, etc. using 3 or more communication outlets. Borough collaborates on alert message with the Chester County Health Department Citizen block captains disseminate the information above in an official, approved communication and letter from mayor West Chester Borough elected officials and staff meet with Chester County Health Department to initiate adulticide spray based upon completed response plan activities, mosquito and human surveillance data, environmental conditions, etc. West Chester Borough will disseminate spray date, time, location and personal precaution information to all residents through all communication outlets available 48 hours in advance of the spray. will disseminate spray date, time, location and personal precaution information to registered 8

9 Risk Level Vector Surveillance and Control Human Surveillance and Investigation Information and Outreach hypersensitives and bee keepers; local government; Pennsylvania Emergency Management Agency; County 911; and statewide representatives 48 hours in advance of the spray. 9

10 Information and Outreach Strategies Critical to any collaborative, citizen focused initiative is clear, reliable and trusted information. To that end, a key element of the response plan outlined above relies heavily on the information and outreach efforts. Below are a few strategies West Nile Task Force recommends considering: Communication Outlets Letter from mayor/elected officials Flyers/posters to be hung in Business Improvement District Yard signs Borough and Chester County website updates Social Media (Facebook, Twitter, etc.) Door hangers Informational pamphlets/flyers at public events Robo-call system (ChescoReady) Block Captains An essential grassroots element of West Chester Borough s WNV response plan is the use of block captains volunteer residents who work within a one to four block territory of the Borough to disseminate information, materials through direct house-by-house communication across the entire Borough. Although block captains do not need to attend any meetings, they are always welcome at meetings of Don t Spray Me (DSM), West Nile Task Force, Sustainability Advisory Council, and other Borough bodies. Block captains are also invited to Don t Spray Me social events that include educational presentations and displays, networking opportunities, and learning about the environment. Block captains are expected to thoroughly grasp the fundamental philosophy of the Response Plan: to help educate the public in reducing both mosquito breeding and pesticide spraying. Block captains agree to: hand out, in their assigned territory, letters from the mayor, door hangers, notice of impending spraying, and similar items, a total of 3 or 4 times a year, including knocking on doors to try for personal contact; invite and pay attention to questions, comments from neighbors, and information about possible breeding sites; contact DSM accordingly; and relay back to those neighbors any resulting information from DSM, the Borough, or the County; read and remain aware of the Chester County Health Department, Borough, and DSM web sites, Facebook pages, print handouts, and communications that reflect general policies, changes in Risk level, results of WNTF meetings, relevant local events, and the like. 10

11 Vector Index The Vector Index (VI) is an estimate of the abundance of infected mosquitoes in an area and incorporates information describing the vector species that are present in the area, relative abundance of those species, and the WNV infection rate in each species into a single index (Gujaral et al. 2007, Bolling et al. 2009, Jones et al. 2011). The VI is calculated by multiplying the average number of mosquitoes collected per trap night by the proportion infected with WNV, and is expressed as the average number of infected mosquitoes collected per trap night in the area during the sampling period. In areas where more than one WNV vector mosquito species is present, a VI is calculated for each of the important vector species and the individual VIs are summed to represent a combined estimate of the infected vector abundance. By summing the VI for the key vector species, the combined VI accommodates the fact that WNV transmission may involve one or more vectors in an area. Increases in VI reflect increases in risk of human disease (Bolling et al. 2009, Jones et al. 2011, Kwan et al. 2012, Colborn et al in press) and have demonstrated significantly better predictive ability than estimates of vector abundance or infection rate alone, clearly demonstrating the value of combining information for vector abundance and WNV infection rates to generate a more meaningful risk index (Bolling et al. 2009). As with other surveillance indicators, the accuracy of the Vector Index is dependent upon the number of trap nights used to estimate abundance and the number of specimens tested for virus to estimate infection rate. Mosquito-based arbovirus surveillance provides three pieces of information (parameters): a) the variety of species comprising of the mosquito community; b) density of each species population (in terms of the number collected in each trap unit of a given trap type); and c) if the specimens are tested for the presence of arboviruses, the incidence of the agent in the mosquito population. Taken individually, each parameter describes one aspect of the vector community that may affect human risk, but the individual elements don t give a comprehensive estimate of the number of potentially infectious vectors seeking hosts at a given time in the surveillance area. Parameter Information Provided Value in Surveillance a) Mosquito Community Composition Diversity of species in the area Documents the presence of competent vector species in the area b) Mosquito Population Density c) Infection Rate of Virus in Mosquito Population Relative abundance of mosquito species in terms of trapping effort Proportion of the mosquito population carrying evidence of the disease agent Quantifies the number of individuals of each mosquito species at a given point in time, particularly important for the key vector species Quantifies incidence of infected and potentially infectious mosquitos in the key vector population; demonstrates if important bridge vectors are involved 11

12 To express the arbovirus transmission risk posed by a vector population adequately, information from all three parameters (vector species presence, vector species density, vector species infection rate) must be considered. The Vector Index (VI) combines all three of the parameters quantified through standard mosquito surveillance procedures in a single value (Gujaral et al. 2007, Bolling et al. 2009, Jones et al. 2011, Kwan et al. 2012, Colborn et al in press). The VI is simply the estimated average number of infected mosquitoes collected per trap night summed for the key vector species in the area. Summing the VI for the key vector species incorporates the contribution of more than one species and recognizes the fact that West Nile (WN) virus transmission may involve one or more primary vectors and several accessory or bridge vectors in an area. The Vector Index is expressed as: Vector Index References The above information can be found at Centers for Disease Control and Prevention website at Bolling BG, Barker CM, Moore CG, Pape WJ, Eisen L Seasonal patterns for entomological measures of risk for exposure to Culex vectors and West Nile virus in relation to human disease cases in northeastern Colorado. J Med Entomol. 46(6): Doi: /j x.Epub2012 Apr 10 Bolling BG, Barker CM, Moore CG, Pape WJ, Eisen L Modeling/GIS, risk assessment, economic impact: Seasonal patterns for entomological measures of risk for exposure to Culex vectors and West Nile virus in relation to human disease cases in Northeastern Colorado. J Med Entomol. 46: Colborn, J.M., K.A. Smith, J. Townsend, D. Damian, R.S. Nasci, J.P. Mutebi West Nile Virus Outbreak in Phoenix, Arizona 2010: Entomological Observations and Epidemiological Correlations. J Amer Mosq Control Assoc. In press. Gujral IB, Zielinski-Gutierrez EC, LeBailly A, Nasci R Behavioral risks for West Nile virus disease, northern Colorado, Emerg Infect Dis. 13(3): Jones RC, Weaver KN, Smith S, Blanco C, Flores C, Gibbs K, Markowski D, Mutebi JP Use of the vector index and geographic information system to prospectively inform West Nile virus interventions. J Am Mosq Control Assoc. 27: Doi: 12

13 Kwan JL, Park BK, Carpenter TE, Ngo V, Civen R, Reisen WK. 2012a. Comparison of enzootic risk measures for predicting West Nile disease, Los Angeles, California, USA, Emerg Infect Dis. 18(8): Kwan JL, Kluh S, Reisen WK. 2012b. Antecedent avian immunity limits tangential transmission of West Nile virus to humans. PLoS One. 7(3):e