Chair and members of the Board of Health. Original signed document on file. Dr. Nicola J. Mercer, MD, MBA, MPH, FRCPC Medical Officer of Health & CEO

Transcription

1 2017 West Nile Virus Summary TO: Chair and members of the Board of Health MEETING DATE: April 4, 2018 REPORT NO: Pages: 14 PREPARED BY: APPROVED BY: SUBMITTED BY: Mike Coburn, Public Health Inspector, Environmental Health Shawn Zentner, Manager, Environmental Health Christopher Beveridge, Director, Health Protection Original signed document on file Dr. Nicola J. Mercer, MD, MBA, MPH, FRCPC Medical Officer of Health & CEO Recommendations It is recommended that the Board of Health: 1. Receive this report for information. Key Points In 2017, Wellington-Dufferin-Guelph Public Health (WDGPH) implemented its 15 th consecutive West Nile virus (WNV) prevention program. This program aims to prevent or reduce human exposure to WNV through public education, larval and adult mosquito surveillance and larviciding activities. WDGPH has two contracts to accomplish WNV activities: 1. Canadian Centre for Mosquito Management Inc. (CCMM) conducts larval surveillance, catch basin and surface water treatments, live adult mosquito trapping and surveillance, and addressing standing water complaints in and outside of the City of Guelph. 2. Entomogen Inc. conducts adult mosquito identification and viral-testing. The City of Guelph s Property Standards Inspection Department addressed 22 standingwater complaints. Outside of the City of Guelph, CCMM addressed five complaints by citizens regarding standing water. Two human cases of WNV were confirmed within the borders of Wellington-Dufferin-Guelph (WDG), which represented 0.7 cases per 100,000 people. Three avian cases of WNV were reported by the Canadian Wildlife Health Cooperative at the Ontario Veterinary College, Guelph.

2 Three WNV-positive mosquito pools were identified in WDG. Public education in 2017 included communicating key messages regarding ways to prevent mosquito bites, elimination of standing water on private property to reduce mosquitobreeding areas, and encouragement to contact WDGPH to request free larvicide treatment for municipally-owned catch basins (storm drains) located on residential property through online and print materials. Discussion WNV is transmitted from adult mosquitoes to humans and was first found in Ontario in Birds of the Corvid family (crows, ravens and blue jays) act as the primary reservoir for the virus, and mosquitoes are the vectors that spread the virus from infected birds to humans and to other animals. 1 The mosquito species of greatest concern for the transmission of WNV are Culex restuans and Culex pipiens. 2 These mosquitoes thrive in urban environments where they breed in small bodies of protected, stagnant water as found in catch basins, abandoned swimming pools, unused tires, blocked eaves troughs, and bird baths. Interventions to interrupt the larval stage of the mosquito life cycle has been key to controlling the spread of WNV. Health Effects of WNV It is estimated that between 70% 80% of people infected with WNV have no symptoms. 3, 4 Some people experience mild, flu-like symptoms including fever, headache, body aches, a mild rash, and swollen lymph glands. 5, 6 In rare cases (<1%) the virus can cause severe symptoms such as inflammation of the brain or spinal cord, which can sometimes be fatal. 6 People over age 50, who have chronic diseases or who are immunocompromised, are at higher risk for serious health effects. However, WNV can cause severe complications for people of any age or health status. 7 There is no specific treatment or vaccine for WNV infection in humans, however, mild symptoms such as fever and body aches can be managed and treated. In 2017, Ontario had 153 lab confirmed and six probable cases of WNV for an incidence rate of 1.1 per 100,000 people while WDG had two confirmed cases for an incidence rate of 0.7 per 100,000 people (Appendix A). WDGPH s Prevention Program WDGPH s WNV prevention program dates back to 2002 when the first human case from within the health unit area was reported. The program typically runs from May/June to September/October of each year depending on weather conditions, when mosquitoes are most prevalent and the potential for infection is highest. 1 The purpose of the WNV program is to prevent or reduce human exposure to WNV within the community through larviciding, mosquito Page 2 of 14

3 surveillance and public education. Adulticiding is not part of WDGPH s WNV program and is carried out in accordance with the Ministry of Health and Long-Term Care s West Nile Virus Preparedness and Prevention Plan. A summary of WDGPH s prevention program for 2017 can be found in Appendix B. Larvicide Program The 2017, larvicide program involved larval surveillance, catch basin (storm drain) and surface water treatments, post-treatment surveillance, live adult mosquito trapping, and responding to standing water complaints, all of which were conducted by the Canadian Centre for Mosquito Management Inc. (CCMM). CCMM was retained to continue this service in Mosquito species identification and viral-testing of adult mosquitoes were carried out by Entomogen Inc. Standing water complaints within the borders of the City of Guelph were addressed through the City of Guelph s Standing Water By-law (By law Number (2003) 1719) by the City of Guelph s Property Standards Inspection Department, often in conjunction with WDGPH and CCMM. In early May 2017, a Public Notification was placed in local newspapers more than two weeks before larviciding treatments began (Appendix C). Public notification is required by the Ministry of the Environment and Climate Change in the process of obtaining larvicide application permits. The public was encouraged to have catch basins located on their own properties treated. Larviciding service was offered for free and was promoted through a media release and the WDGPH website. In 2017, treatment requests increased from 140 requests in 2016 to 152. Surveillance for mosquito larvae in catch basins began in late May Catch basins are designed to trap water and sometimes this water remains stagnant for an extended period of time creating ideal conditions for mosquito breeding. It is widely acknowledged that catch basins provide the single most important developmental site for urban Culex populations of mosquitoes, the primary vectors of WNV. Therefore, timely application of larvicide to catch basins is critical to the success of urban WNV management program. Based on surveillance, surface water and catch basin treatments began in mid-june 2017 and concluded on September 26 th, Details regarding CCMM s larviciding program are found in Appendix D. The public was encouraged to notify WDGPH of areas of standing water that may be conducive to mosquito-breeding. A total of 22 standing water complaints were addressed by the City of Guelph s Property Standards Inspection Department, the majority concerning swimming pools on private property that were not being maintained. Enforcement of this by-law commenced and concluded, based on larval and adult mosquito activity determined through surveillance. Only five complaints regarding standing water were registered outside the borders of the City of Guelph. Three of these five complaints resulted in surface water treatments by CCMM. Complaints regarding standing water (typically areas of wetland in newer subdivisions) were addressed by CCMM. All but one of these areas were locations where treatments had been carried out in the past and which were scheduled for treatment during the 2017 season. Page 3 of 14

4 Surveillance Surveillance activities in 2017 included the collection of both adult and larval life stages of the vector species, Culex restuans and Culex pipiens. The presence of larval vector species determined whether or not larvicide would be applied. Trapped adults were sent to Entomogen Inc. for species identification. Identified vector and bridge species were grouped together into pools (groups of mosquitoes of the same species) and tested for the presence of WNV. A total of 140 mosquito pools were tested and three pools were found to be positive for WNV. The mosquitoes for all three of these positive pools were trapped within the City of Guelph. A summary of surveillance activities and findings by Entomogen Inc. can be found in Appendix E. Unlike previous years, WDGPH saw increases in the number of human infections, vector species, and the number of positive mosquito pools. Human infections increased from one in 2016 to two in 2017, both acquired locally. The overall number of adult mosquitoes trapped increased from 2,052 in 2016 to 3,116 in 2017 with a corresponding increase in the number of WNV vector species (1.35% of all mosquitoes trapped in 2016 to 1.64% in 2017). Of the 3,116 mosquitoes trapped, 2,928 were identified to species. Interestingly, three mosquito pools tested positive for WNV following three consecutive years with zero testing positive. Public Education Public education efforts continued in 2017 to convey WNV concerns and the simple steps that can be taken by the public to reduce their risk of contracting the virus. Key messages included steps to prevent mosquito bites, elimination of standing water on property to reduce mosquito breeding areas, and public encouragement to contact WDGPH for free larvicide treatment for municipally-owned catch basins on their property. Key messages were delivered through: Public notices regarding the mosquito larvicide program were published in three local newspapers (Orangeville Banner, Guelph Mercury Tribune and Wellington Advertiser). The WDGPH WNV webpage. A WNV media release was distributed in May 2017, communicating the key messages listed above. WDGPH collaborated with the City of Guelph to distribute WNV prevention postcards through the City s rain barrel program. In July 2017, a blog was posted on the WDGPH website titled Fighting the mosquito bite this summer In August 2017, Brock University research results prompted a local earned media. In late August 2017, another media release was distributed following two area residents testing positive for WNV. Key messages were re-iterated and information regarding positive mosquito pools was also shared. Key messages were tweeted and posted on Facebook in spring and summer Page 4 of 14

5 Conclusion WNV exists in WDG and will continue to be a presence in the future as long as there are Corvid birds to act as reservoirs for the virus and mosquito vectors to transmit the virus to humans. Warmer spring and summertime temperatures allow for faster larval development and creates potential for an extra generation of adults, which live longer thus increasing the potential for magnifying the virus in the environment. High levels of snow melt and rainfall create more larval habitat which increases the likelihood of higher mosquito populations. Warmer winters provide favourable hibernating conditions which contribute springtime mosquito emergence. These environmental factors are complicated and unpredictable. Consequently, forecasting mosquito populations and potential virus activity is not practical or feasible. Vigilant surveillance, larviciding, and educational efforts in 2018 and beyond is important, and will continue to be the most effective tools WDGPH can use to prevent the spread of WNV. Ontario Public Health Standard Infectious and Communicable Diseases Prevention and Control The Board of Health shall develop a local vector-borne management strategy based on surveillance data and emerging trends in accordance with the Infectious Diseases Protocol, WDGPH Strategic Direction(s) Health Equity: We will provide programs and services that integrate health equity principles to reduce or eliminate health differences between population groups. Organizational Capacity: We will improve our capacity to effectively deliver public health programs and services. Service Centred Approach: We are committed to providing excellent service to anyone interacting with WDG Public Health. Building Healthy Communities: We will work with communities to support the health and well-being of everyone. Health Equity A higher prevalence of WNV has been found in both mosquitos and humans in low-income areas. The environmental characteristics of low-income areas can be conducive for mosquito development, potentially leading to a higher occurrence of WNV disease in humans. 8,9 Page 5 of 14

6 WNV prevalence in low-income areas is thought to occur due to a combination of three factors: 1. Older infrastructure characterized by antiquated runoff systems that contribute to poor drainage and favourable mosquito breeding habitats; 2. Less investment in private property upkeep, leading to a higher density of stagnant water; and 3. Lack of knowledge with a lower likelihood of requesting mosquito management in the area. 8 References 1. Health Canada. [Internet]. Surveillance of West Nile virus. [updated 2017, Dec 21; cited 2018 Mach 26]. Available from 2. Ontario Ministry of Health and Long-Term Care. West Nile Virus Preparedness and Prevention Plan Toronto ON: Queen s Printer for Ontario. 3. Mostashari F, Bunning M, Kitsutari P et al. Epidemic West Nile encephalitis, New York, 1999: Results of a household-based seroepidemiological survey. Lancet. 2001; 358: Zou S, Foster GA, Dodd RY et al. West Nile fever characteristics among viremic persons identified through blood donor screening. J Inf Dis. 2010; 202: Watson J, Pertel P, Jones R et al. Clinical characteristics and functional outcomes of West Nile Fever. Ann Intern Med. 2004; 141: Hayes E, Sejvar J, Zaki S, Lanciotti R, Bode A, Campbell G. Virology, pathology, and clinical manifestations for West Nile Virus Disease. Emerg Infect Dis. 2005; 11: Health Canada. [Internet]. Surveillance of West Nile virus. [updated 2015, June 26; cited 2018 Mach 26]. Available from 8. Harrigan R, Thomassen H, Beurmann W et al. Economic Conditions Predict Prevalence of West Nile Virus. PLoS ONE. 2010; 5(11): e LaDeau SL, Liesnham PT, Biehler D, Bodner D. Higher mosquito production in low-income neighbourhoods of Baltimore and Washington, DC: Understanding ecological drivers and mosquito-borne disease risk in temperate cities. Int J Environ Res Public Health. 2013; 10(4): Appendices Appendix A WNV Rates in WDGPH and Ontario (10 year trend) Appendix B Infographic: Summary of WDGPH s 2017 WNV Program Appendix C Larvicide Public Notice Appendix D Summary of CCMM s Larval Mosquito Control Program (Larviciding) Appendix E Summary of WNV Surveillance Activities Page 6 of 14

7 Appendix A Incidence Rates of Lab-Confirmed ad Probable West Nile Virus Illness, Wellington-Dufferin-Guelph and Ontario, Number of cases per 100,000 people A WDG rate ON rate Year of Case Onset Page 7 of 14

8 Appendix B 2017 West Nile Virus Program Report Wellington-Dufferin-Guelph Public Health Background Mosquitoes West Nile virus cycles between mosquitoes, especially Culex species, and birds. Some infected birds can ' develop high level of the virus in their bloodstream and mosquitoes can become infected by biting these infected birds. Mosquitoes with West Nile virus can bite and infect humans. Humans Bird Amplifier Host Surveillance and Reporting 115 traps cases submitted from mosquitoes submitted mosquito pools tested per 100,000 people* 12 different sites positive for West Nile virus confirmed and probable in WDG case of West Nile virus in WDG, possibly locally acquired 1.1 cases per 100,000 people of confirmed and probable cases of West Nile virus in Ontario 409 mosquito pools tested positive for West Nile virus in Ontario We treated: 22,345 roadside catch basins 152 non-roadside catch basins ha. stagnant surface water Public Education Media release website education, and social media posts on preventing bites and eliminating standing water 'WDG rates are based on very low number of cases and should be interpreted with caution. Page 8 of 14

9 Appendix C NOTICE Ground Application for Larval Mosquitoes Wellington-Dufferin-Guelph Public Health will conduct a mosquito larvicide program from May 1 to October 31, The Medical Officer of Health has authorized the program to reduce mosquito populations suspected of carrying West Nile virus. Ministry of the Environment and Climate Change licensed applicators or trained technicians will apply the larvicide by hand, in and around communities in Wellington and Dufferin counties. Larvicide will be used in mosquito larvae breeding sites, such as: roadside ditches temporary pools sewage lagoons storm-water retention ponds areas of standing water municipal catch basins Products Used For catch basins: Altosid Pellets (PCP#21809, pellet); Altosid XR Briquets (PCP#27694, ingot); and VectoLex WSP (Reg. No , pouch). For standing water sites: VectoBac 200G (Reg. No , granular); and VectoLex CG (Reg. No , granular). Altosid is a methoprene product; VectoBac is a Bacillus thuringiensis israelensis product; and VectoLex is a Bacillus sphaericus product. When used according to directions, these larvicides pose little risk to people. For information about the products used or details on the exact locations and dates of treatment please call our toll free number For more information contact: Shawn Zentner, MPH, BASc, CPHI(C) Manager, Health Protection Wellington-Dufferin-Guelph Public Health T: ext Page 9 of 14

10 Appendix D Summary of CCMM s Larval Mosquito Control Program (Larviciding) Table 1: Summary of Types of Treatment Locations Location Type Summary of Types of Treatment Locations (Per Round of Treatment) 2017 Total (Per Round) Roadside Catch Basins 22,354 Non-Roadside Catch Basins 152 Environmentally Sensitive (ESA) Area Catch Basins Stagnant Surface Waters Ditches x 48 Storm Management Ponds x 39 Woodland Pools x 6 Wetland x 7 Storm Management Ditches x 6 Ponds x 1 Naturalization Areas x ha (Total Surface Area) Figure 2: Summary of Non-ESA Catch Basin Larvicide Treatments Summary of Non-ESA Catch Basin Larvicide Treatments 2017 Product Rounds App. Rate CBs Treated/Round Total Prod. Used All Rounds Altosid Pellets g/cb 22, kg Altosid XR Briquets 1 1 Briquet/CB Briquets Figure 3: Summary of ESA Catch Basin Larvicide Treatments Summary of ESA Catch Basin Larvicide Treatments 2017 Product Rounds App. Rate CBs Treated/Round Total Prod. Used All Rounds VectoLex WSP 4 1 Pouch/CB Pouches Page 10 of 14

11 Appendix D con t Figure 4: Summary of Stagnant Surface Water Larvicide Treatments Wellington-Dufferin-Guelph Public Health Vector-borne Disease Summary of Stagnant Surface Water Larvicide Treatments 2017 Product Total Treatments App. Rate Area Treated Total Prod. Used All Treatments VectoBac 200G kg/ha ha kg Figure 5: Summary of Larvicide Application Dates Wellington-Dufferin-Guelph Public Health Vector-borne Disease Summary of Larvicide Application Dates 2017 Site Product App. #1 App. #2 App. #3 App. #4 Unschedul ed Apps. Roadside CBs Altosid Pellets June July Aug. 2-4 Aug N/A Nonroadside CBs Altosid XR Briquets June 16 Aug. 23 N/A N/A N/A N/A ESA CBs VectoLex WSP July 9 July 16 Aug. 4 Aug. 21 N/A Stagnant Surface Waters VectoBac 200G N/A N/A N/A N/A June 16 Sept. 26 Page 11 of 14

12 Appendix D con t Wellington-Dufferin-Guelph Public Health Vector-borne Disease Summary of Product Application Location by Community 2017 Roadside (Non- ESA) CBs Treated w/ Altosid Pellets Non-Roadside (Non-ESA) CBs Treated with Altosid XR Briquets ESA CBs w/ Vectolex WSP Stagnant Surface Waters w/ Vectobac 200G Arthur Elora Guelph Guelph Drayton Guelph Erin Rockwood Elora Orangeville Orangeville Orangeville Erin Rockwood - Fergus Fergus - - Arthur Guelph Harriston Mount Forest Orangeville Palmerston Puslinch Page 12 of 14

13 Appendix E Wellington-Dufferin-Guelph Public Health Vector-borne Disease Summary of Adult Mosquito Species Surveillance 2016 Vector Species Species Identified Total Number Overall % Culex pipiens/restuans % Bridge Vector Species Ochlerotatus trivittatus % Aedes vexans vexans % Ochlerotatus stimulans % Ochlerotatus triseriatus % Anopheles quadrimaculatus % Anopheles punctipennis % Ochlerotatus canadensis % Anopheles walkeri % EEEV Vector Species Culex erraticus % Non-Bridge Vector Species Coquillettidia perturbans % Ochlerotatus black-legged % Ochlerotatus broad-banded % Aedes cinereus % Aedes/Ochlerotatus species % Ochlerotatus excrucians % Psorophora ferox % Anopheles species % Culiseta morsitans % Culex territans % TOTAL 2, % Page 13 of 14

14 Appendix E con t Table 1 : Confirmed WNV-Positive Mosquito Pool Summary and Locations 2017 Wellington-Dufferin-Guelph Public Health Vector-borne Disease Confirmed WNV-Positive Mosquito Pool Summary and Locations 2017 Collected Tested Species Identified # of Mosquitoes in Pool Location Aug. 2 Aug. 6 Aedes vexans vexans 11 Guelph Aug. 2 Aug. 6 Ochlerotatus triseriatus 19 Guelph Aug. 24 Aug. 26 Culex pipiens/restuans 1 Guelph NOTE: A total of 140 mosquito pools were tested for WNV. Page 14 of 14