2015 Vector-Borne Disease Technical Report

Transcription

1 2015 Vector-Borne Disease Technical Report

2 Table of Contents Executive Summary... 1 Introduction... 4 West Nile Virus... 4 Eastern Equine Encephalitis Lyme Disease Program Evaluation Conclusion Appendix A Case Definitions Appendix B 2015 Weekly Codes Appendix C 2015 Risk Assessment... 30

3 Executive Summary This report summarizes Peel Public Health s Vector-Borne Disease program activities in Vector-borne diseases are diseases that are transmitted to humans or other animals by an insect or other arthropod. In Ontario, West Nile Virus (WNV) and Lyme disease are the two main endemic vector-borne diseases of public health importance as both of these diseases can be acquired within the province. Another vector-borne disease of concern in Ontario is Eastern Equine Encephalitis (EEE). EEE is a rare but serious viral disease spread by mosquitoes that can affect people and horses. The EEE virus has been detected in Ontario in horses and mosquitoes but, to date, no human cases have been reported. Peel Public Health s 2015 Vector-Borne Disease Prevention Plan identified activities Peel Public Health would carry out in order to comply with Ontario Regulation 199/03 Control of West Nile Virus. Under Ontario Regulation 199/03, the local Medical Officer of Health (MOH) is required to conduct a risk assessment of the conditions pertaining to WNV in the health unit. The risk assessment identifies the probability of human infection based on WNV surveillance activities as well as other pertinent information elements. Completion of the risk assessment in accordance with the regulation offers guidance to the MOH regarding appropriate WNV reduction activities, and if needed, provides a review of appropriate mosquito reduction activities (i.e. larviciding or adulticiding) and their effectiveness. Peel Public Health s approach to WNV control emphasized disease prevention in humans and protection of the environment through region-wide surveillance and Integrated Mosquito Management (IMM). This meant an emphasis on public education, source reduction and larviciding. If the level of WNV in Peel increased, then education, surveillance and reduction activities would be intensified. Surveillance activities indicate that WNV is endemic in Peel and that WNV levels can fluctuate widely from year to year. In 2015, there were 22 positive mosquito batches reported, which was the same number that was reported in There was an increase in the number of human cases reported in 2015 with two confirmed cases, whereas in 2014, there were no human cases. Source reduction and larviciding activities focused on the Culex pipiens and Culex restuans mosquitoes, the main vectors of WNV in Peel. These two mosquito species breed in water that has been stagnant for more than a week in sites such as catch basins, roadside ditches, culverts and artificial containers (abandoned swimming pools, tires, buckets, etc.). These mosquito habitats were priority targets for elimination through improved maintenance and for larviciding where stagnant water could not be removed. Other mosquito habitats such as marshes and natural ponds were only treated if they 1

4 were found to be important to local WNV transmission. Surveillance of mosquitoes provided an early warning of the risk to human health. This information was used to enhance mosquito reduction and education efforts in high risk areas to interrupt the amplification of WNV before it had a significant impact on human health. The West Nile Virus component of the 2015 Vector-Borne Disease Prevention Plan was consistent with the recommendation from the United States Centers for Disease Control and Prevention. Eastern Equine Encephalitis (EEE) is a mosquito-borne viral disease which occurs primarily in the eastern half of the United States where it causes disease in humans and horses. The main EEE transmission cycle is between birds and mosquitoes. The most important mosquito species in maintaining the bird-mosquito transmission cycle is Culiseta melanura. Mosquito surveillance conducted by Peel Public Health over the last several years has found low numbers of this species in Peel. In 2015, Peel Public Health continued to monitor the prevalence and distribution of Cs. melanura using the regionwide adult mosquito CDC light trap network. In 2015, two Cs. melanura were found in the CDC light traps, one was found in central Brampton and one in north Caledon. Both mosquitoes tested negative for EEE. If the virus had been found in the local mosquito population or if a confirmed case of EEE involving a human or horse occurred in Peel, then increased surveillance and public education would have commenced. Lyme disease, like WNV, is included in Ontario Regulations 558/91 and 559/91 making it both a reportable and communicable disease under the Health Protection and Promotion Act. Lyme disease is an illness caused by the bacterium, Borrelia burgdorferi, which can be spread through the bite of an infected tick. In Ontario, the disease is spread by the blacklegged tick (Ixodes scapularis) which is sometimes called the deer tick. To date, an established black-legged tick population has not been identified in Peel, although there are numerous sites in Peel region that have a combination of environmental factors that would support new populations of black-legged ticks to become established in the future. In 2015, two confirmed Lyme disease cases were reported in Peel; one was associated with travel to the north-eastern United States and one was acquired in eastern Ontario. In June, active tick surveillance was undertaken Mississauga in an area surrounding where a black-legged tick was found by a resident. The tick dragging sessions did not identify any ticks. In 2015, Peel Public Health continued passive tick surveillance by examining ticks brought into Peel Public Health offices by the public. Thirty-three tick samples were submitted to Peel Public Health: 2

5 five ticks black-legged tested negative for Lyme one tick black-legged tick tested positive for Lyme (found in eastern Ontario) two black-legged ticks (pending results by PHAC) 25 additional ticks: 19 dog ticks, two groundhog ticks, one squirrel tick, one Lone Star Tick that was found in South Carolina by a Peel resident, and two ticks are awaiting identification by the Public health Ontario laboratory s (data as of December 22, 2015). Specimens associated with human contact were submitted to the Central Public Health Laboratory (CPHL) in Toronto for species confirmation. The three black-legged ticks were sent to the Public Health Agency of Canada s (PHAC) National Microbiology Laboratory in Winnipeg for Lyme disease testing. One tick was found to be positive for Borrelia burgdorferi. The positive tick was submitted to Peel Health by a Peel resident whose exposure was in eastern Ontario. 3

6 Introduction The Region of Peel has had a West Nile Virus Prevention Plan since In 2009, Peel Public Health developed a Vector-Borne Disease Prevention Plan which focused primarily on WNV but also addressed other vector-borne diseases of concern. The 2015 Vector-Borne Disease Prevention Plan followed the blueprint of the plan from the previous year as it included components for Lyme disease and EEE as well as WNV. West Nile Virus WNV was first detected in Peel in birds and mosquitoes in Locally acquired human illness occurred for the first time in 2002 when 112 residents had laboratory evidence of WNV infection (55 suspect cases, 20 probable cases and 37 confirmed cases, including two deaths). However, the case definition has changed since If current human case definitions were used, there would have been 18 confirmed cases in One of the goals of the Vector-Borne Disease Prevention Plan is to minimize the impact of WNV with a regional surveillance program involving humans and mosquitoes (adults and larvae). The surveillance program guides the Integrated Mosquito Management (IMM) activities which include mosquito larvae reduction, stagnant water site remediation, and risk communication activities. Surveillance activities continue to indicate that WNV is endemic in Peel and that WNV levels can fluctuate widely from year to year. In 2015, Peel Public Health continued human and mosquito surveillance, public education and larval mosquito reduction activities. WNV Surveillance Program 2015 The human case surveillance program is intended to detect human cases of WNV in Peel. All probable and confirmed human cases identified by hospitals and physicians are reported to the local public health department. The MOHLTC has developed case definitions and diagnostic test criteria (refer to Appendix A). In 2015, there were two confirmed human cases of WNV in Peel Region. Table 1 presents the number of human cases of WNV in Peel Region from 2002 to In 2002, 57 probable and confirmed cases of WNV were reported based on the case definitions at the time. If the present day case definition was applied, there would have been 18 confirmed human cases in

7 Table 1: Number of Human Cases by Municipality (confirmed and probable), Region of Peel, Year Region of Peel Mississauga Brampton Caledon In 2002, there were a total of 112 cases with laboratory and/or clinical evidence of WNV infection; 57 cases were classified as probable or confirmed. In subsequent years, only confirmed cases were reported as a result of changes in disease classifications. If the present day classifications were applied, there would have been 18 confirmed human cases in Comparison with Other Ontario Health Units As of December 22, 2015, there were 32 confirmed or probable WNV human cases in Ontario, compared to 11 in 2014, and 55 in 2013, and 262 in Comparison with Other Provinces In 2015, there were a total of 76 human cases in Canada, compared to 21 cases in 2014 and 115 cases in 2013 and 428 cases in In 2015, positive human cases were found in Ontario (32), Quebec (39) and Manitoba (5). WNV Adult Mosquito Surveillance Program 2015 Peel Public Health monitored WNV activity in the local mosquito population from June 16 to September in GDG Environnement Lteé provided Peel Public Health with mosquito identification and WNV and EEE testing services as part of the monitoring program. 5

8 Map 1 shows the locations for the fixed traps set in Peel Region in Thirty-one fixed CDC light traps were distributed by Regional ward, with a minimum of one trap per ward across Peel: 17 in the City of Mississauga, nine in the City of Brampton and five in the Town of Caledon. The red dots denote traps from which positive WNV mosquitoes were collected. In 2015, there were 10 traps that collected positive mosquitoes, five each in Mississauga and Brampton. The Region of Peel sent adult specimens collected in the 31 mosquito traps to GDG Environnement Lteé (Map 1). As requested by Peel Public Health, a maximum of two pools for WNV (Culex complex only) were tested per trap during the first six weeks of the adult surveillance program. Up to four pools of WNV vector mosquitoes were tested in the remaining 11 weeks in the traps located in Brampton and Mississauga. The rationale behind increasing WNV tests in the later part of the season is based on historical test results which indicate that the WNV bridging vectors generally do not test positive until late July or early August. Pool sizes contained a maximum of 50 mosquitoes. These pools were homogenized, extracted and viral tested. The gold standard real time RT-PCR test was used according to the MOHLTC criteria. In 2015, 88,089 mosquitoes were collected with 40,053 being identified; of those, 13,021 were WNV vectors (Table 2). The most abundant vector species in Peel in 2015 were Aedes vexans vexans and Culex pipiens/restuans (Table 2). The majority of positive pools were Culex pipiens/restuans with 21 of 22 (95%) (Table 3). The other positive pool was Aedes vexans vexans (5%) (Table 3). Of the 22 WNV positive mosquito batches that were identified in 2015, 15 were in Brampton and seven in Mississauga. 6

9 Map 1: Map of Mosquito Trap Location, Region of Peel,

10 Table 2: West Nile Virus Vector Species Abundance Totals, 2015 Species Specimens tested Percentage approximate (%) Ae vexans vexans 6, Cx. pipiens / restuans 6, An punctipennis Oc japonicus Oc trivittatus Oc triseriatus/hendersoni Cx species 82 1 An quadrimaculatus 3 <1 Cx salinarius 13 <1 Total 14, Source: GDG Environnement Lteé: based on PCR data Table 3: West Nile Virus Vector Species Testing Pools, 2015 Species Pools Tested Specimens Tested Positive Pools Cx pipiens/restuans 432 6, Ae vexans vexans 335 6,860 1 An punctipennis Oc japonicus Oc trivittatus Oc triseriatus/hendersoni Cx species Cx salinarius An. quadrimaculatus Total 1,238 14, Source: GDG Environnement Lteé: based on PCR data 8

11 # of Positive Mosquito Pools by Week Figure 1 compares the annual number of positive mosquito batches per week for the 2002 baseline year and Based on previous years data, positive mosquito batches are likely to occur any time after June. There are occasions when no positive mosquitoes are found at sites during the weeks tested. The year to year onset and peak of WNV-positive mosquito batches vary. The first positive trapping events in 2015 occurred during week 30 (July 27 and July 28) in central Mississauga. The last positive batch in 2015 occurred during week 38 (September 21) in west Brampton. The weekly onset and cessation of positive mosquito batches were relatively typical of a normal year. Figure 1: WNV Positive Mosquito Batches by Week of Collection, Region of Peel, 2002, (N=128) (N=22) (N=22) (N=51) Note: Larviciding was not undertaken in

12 The minimum infection rate (MIR) is used as an indicator of the prevalence of WNV transmission intensity and therefore, the risk for human disease. The MIR is the number of positive batches of infected mosquitoes of a given vector species divided by the total number of mosquitoes of a given vector species that were tested for the presence of the virus, expressed per 1,000. Table 4 represents the MIR s for the Culex species grouped by municipality in Peel region in Higher MIR s are usually indicative of greater WNV activity among a given species but can be unreliable when the sample size is less than 1,000. Since fewer than 1,000 Culex mosquitoes were collected in Caledon this data would not fully represent the MIR rate in this municipality if positive mosquito batches were reported in The overall MIR in Culex species in Peel region was 3.39 in Table 4: Minimum Infection Rates* of Culex Species in Each Municipality, Region of Peel, 2015 Municipality Mississauga Brampton Caledon Peel Region Vector Species Culex pipiens/restuans Culex salinarius Culex pipiens/restuans Culex salinarius Culex pipiens/restuans Culex salinarius Culex pipiens/restuans Culex salinarius 2015 Actual Number Tested 2015 Positive Batches 2015 MIR* 1, , Not reportable sample size under 1,000 6, *The Minimum Infection Rate (MIR) is calculated as the number of positive batches of infected mosquitoes of a given species divided by the total number of mosquitoes of a given vector species that were tested for the presence of the virus, expressed by 1,000 WNV Larval Mosquito Surveillance Program 2015 Larval surveillance is useful in guiding WNV prevention and reduction activities. It is used to determine the location, species and population densities of mosquitoes. Larval surveillance activities are vital for predicting adult emergence and establishing optimal times for implementation of larval reduction measures. In 2015, staff surveyed a variety of aquatic habitats for the presence of mosquito larvae from early June to late September. Potential breeding sites were identified by referring 10

13 back to breeding site information collected in previous years and by stagnant water complaints received through the Environmental Health Contact Centre or on-line reporting form. Increased larval monitoring and aquatic site mapping was undertaken on public lands in the vicinity of Caledon Equestrian Park near Palgrave before and during the 2015 Pan Am Games. This enhanced surveillance assisted in identifying sites of concern that required larvicide applications at this Pan Am Games facility. Larval surveillance was conducted at 2,196 potential mosquito breeding sites identified by VBD staff on publicly-owned lands across the Region in Table 5 provides a breakdown of the distribution of surface water sites monitored by municipality in 2015 relative to previous years. In 2015, over half (56%) of the potential breeding sites monitored were in Mississauga, 21% in Brampton, and 23% were in Caledon. Table 5: Number of Surface Water Sites Monitored by Municipality, Region of Peel, 2002, Year Peel Region Mississauga Brampton Caledon ,073 1, ,274 1, , , ,015 1, ,086 1, ,196 1, Note: Monitoring season ran from May-September 2002 through 2008, and from June-September since 2009 Figure 2 represents the larval surveillance results by breeding site type (habitat) in Peel Region in Culverts (32.6%) and ditches (29.8%) comprised almost three quarters of sites with larvae present. These are the most difficult locations to contain mosquito populations using control measures because of their relative abundance and effectiveness at holding standing water. 11

14 Figure 2: Type of Sites Found to Contain Mosquito Larvae, Region of Peel, 2015 Storm Water Management Wet Pond 3.7% Other 3.4% Field Pool 1.3% Marsh 1.3% Woodland Pool 5.3% Creek 9.8% Ditch 44.1% Culvert 30.3% 12

15 Species Identification - Larval Analysis In 2015, staff identified 9,403 mosquito larvae from June to September, an increase from 2014 when 7,002 larvae were identified. There were 14 different species identified in 2015; the same number identified in The majority (65%) were of the Culex species - Cx. pipiens/restuans and Cx. salinarius which are key WNV vectors, as well as Cx. territans, a non-wnv vector. This figure is slightly lower than the percentage of larvae identified as Culex species in 2014 (71%). Aedes vexans vexans, a confirmed WNV bridge vector in Ontario, accounted for 22% of larvae identified in Oc. japonicus, an invasive species of concern that is a WNV vector, accounted for less one percent of larvae identified. Larval Mosquito Reduction A major part of the Region of Peel Vector-Borne Disease program is to conduct activities to reduce the number of vector mosquitoes. This goal can be achieved by preventing the emergence of mosquitoes by eliminating or altering habitats (source reduction) to make them less conducive to mosquito breeding, and by pesticide treatment at the larval stage to impede their development into viable adult mosquitoes. Source reduction is important and the Region of Peel s public education and outreach program highlights the need for eliminating stagnant water. However, it is very difficult and cost-prohibitive to eliminate all breeding sites because very little water is required for most female mosquitoes to lay their eggs, particularly in the case of the Culex species. Therefore, the prevention plan relies heavily on the larviciding program. The purpose of the larviciding program is to reduce mosquito abundance, especially the Culex species. It is easier, more efficient and cost effective to control mosquito populations by treating at the larval stage with larvicides before adult mosquitoes emerge and become more widely dispersed. Habitats of importance include roadside catch basins, ditches, culverts, discarded tires, unused swimming pools, field pools and containers left outdoors. These breeding sites promote the emergence of multiple mosquito species because of standing or slowmoving water and the presence of decaying organic matter which serves as food for the larvae. Special attention and efforts were directed towards monitoring catch basins and surface water breeding sites such as ditches, culverts, and field pools. Catch basin networks are extensive in urban and suburban environments. They retain a small amount of water and organic matter in the form of sediment that collects in the sump of the catch basin. The majority of catch basins in Peel have been found to contain larvae. Surface water breeding sites are many in number and type and can change from year to year requiring a systematic approach to their surveillance and treatment. 13

16 Habitat modification, which includes altering the habitat to eliminate standing water, can also reduce the potential to breed mosquitoes. In 2015, Peel Public Health staff continued to work with municipal departments to pursue all effective measures to achieve this outcome. Catch Basin Treatment Three rounds of roadside municipal catch basin larviciding were conducted in The municipal catch basins were treated with Altosid Pellets with the exception of the catch basins located within Environmentally Sensitive Areas (ESAs) which were treated with VectoLex 2 WSP (Bacillus sphaericus). Non-roadside catch basins were treated once with a single application of Altosid Briquets which provide over 90 days of control. A prophylactic approach was followed where catch basins were treated regardless of whether water was present. Factors such as catch basin cleaning, new subdivisions, parked vehicles and construction prevented access to some roadside catch basins and resulted in a variance in treatments during each round. Table 6 summarizes the catch basin treatment activities across Peel Region in A total of 299,454 (round 1: 99,573; round 2: 98,613; round 3: 100,160) roadside catch basins in Peel were treated with kg of Altosid Pellets, and 984 roadside catch basins in Peel Region were treated with Vectolex water soluble pellets (WSP). Altosid XR Briquets were applied to 1,108 non-roadside catch basins, including those located in or along parks, private backyards, daycares, government buildings, social housing complexes and long-term care facilities in Peel in Table 6: Summary of Catch Basin Treatments, Region of Peel, 2015 Number of catch basins Treated Round 1 Round 2 Round 3 Quantity of Altosid (kg) Number of Pouches Number of catch basins Treated Quantity of Altosid (kg) Number of Pouches Number of catch basins Treated Quantity of Altosid (kg) Number of Pouches Altosid Briquettes Number of catch basins Treated Brampton 45, , , Caledon 4, , , Mississauga 50, , , ,082 Peel 99, , , ,108 Source: GDG Environnement Lteé,

17 Surface Water Treatment Monitoring mosquito larval habitats to assess the presence and abundance of mosquito larvae was conducted using a standard plastic dipper following the Ministry of Environment and Climate Change s (MOECC) sequential sampling method. On each surveillance visit, the standing water site was given a pool rating based on the total number of larvae observed. Larval samples were also collected and identified by Peel Public Health staff. If vectors were identified, the surface water site was referred to GDG Environnement Lteé for treatment from June 1 to September 25. There were 619 surface water treatments undertaken in 2015 (Table 7), compared to 648 treatments in GDG Environnement Lteé staff reported an additional 685 surface water visits did not result in treatment as the sites were dry, had low larvae counts or vector species were not present at the time of their site visits. Table 7: Number of Surface Water Sites Treated, Region of Peel, 2015 Month Number of Sites Treated Quantity of Vectobac Applied (L) Treated Area (ha) June July August September Total Source: GDG Environnement Lteé, 2015 Environmentally Sensitive Areas Permission from the Ontario Ministry of Natural Resources (MNR) and a special wetlands permit were obtained to allow for larviciding within specific Environmentally Sensitive Areas (ESA s) in Peel. Six ESA s were noted in the permit: Rattray Marsh, Cawthra Woods, Heartlake Wetland Complex, Credit River Wetland (O Neil Court Storm Water Management Pond), Credit River Marsh and Lorne Park Prairie. ESA s are defined by the MOECC and spatial location data is obtained from the MNR. There are two circumstances when a Sensitive Area and Species Protocol are required by the MOECC in order to obtain a permit and apply a larvicide. The first situation occurs when a catch basin is either located within an ESA or it is known to be the last catch basin before an outfall into an ESA. In Peel, there were

18 municipal catch basins that met one of these criteria. VectoLex WSP was used to control mosquito larvae in ESA catch basins. The second situation occurs when a standing water site falls within an ESA. In Peel, there are several standing water sites that meet this criterion including multiple sites within Rattray Marsh, Cawthra Woods, Heartlake Wetland Complex, Credit River Wetland (O Neil Court Storm Water Management Pond), Credit River Marsh and Lorne Park Prairie. Pesticide Effects Surveillance In 2015, pesticide effects surveillance was included in the WNV component of the Vector- Borne Disease plan. As in previous years, Peel Public Health continued to work with other municipalities, conservation authorities and the MOECC to ensure our larviciding program did not negatively impact the ecosystem. Peel Public Health also used larvicide products that have been identified as having the least environmental impact. Staff from the Vector-Borne Disease team conducted field inspections to verify the service provider contracted to conduct larviciding in Peel was applying the larvicides in accordance with MOECC regulations. Efficacy and Quality Assurance Peel Public Health conducted quality assurance monitoring of roadside catch basins during all three rounds of treatment. VBD students were assigned map zones and noted the catch basins that did not have a coloured paint dot associated with the latest application round. GDG Environnement Lteé was provided a list of the missed catch basins which were to be revisited within 24 hours of notification. An increased number of missing paint dots on the catch basins grates were noted in 2015, this may have been the result of poor quality paint used to mark the catch basins dots. Peel Public Health has conducted catch basin methoprene efficacy tests since larviciding was initiated in the Region of Peel in The Vector-Borne Disease team follows the post-larviciding monitoring for methoprene efficacy protocol noted in the MOECC Permit Applicant Guide for Municipalities and Health Units: Controlling Mosquito Larvae for Prevention and/or Control of West Nile Virus. Peel Public Health staff collected mosquito pupae and roadside catch basin water following each application round of the pellets from a small number of catch basins. The pupae were kept in jars covered with mesh lids and observed daily to see if viable adults successfully emerged over a period of 4 days. The number of dead pupae, dead adults and live adults were counted. In 2015, 47 pupae were collected and 9 viable adults 16

19 emerged, resulting in 81% efficacy, which is a higher than the 73% efficacy result recorded in 2013 and Risk Assessment Summary In 2015, from mid-june to early October (week 24-39), a weekly risk assessment was conducted based on surveillance information collected during that week to identify the relative risk of human infection in Peel Region. Various surveillance factors that influence the risk of WNV infection were evaluated. The factors included were: Seasonal temperatures Adult mosquito vector abundance Virus isolation rate in vector mosquito species Human cases of WNV Local WNV activity (equine, mosquito) Time of year WNV activity in proximal urban or suburban regions Each surveillance factor was assigned a weighted score based on the observations of the previous week. The WNV Mosquito Adulticiding Risk Assessment form was completed weekly and when the risk assessment level exceeded a value of three, a decision tree process to consider additional action was invoked. The possibility of adulticiding is considered when the risk level exceeded a value of four. In 2015, the risk assessment level did not exceed the value of four; the highest assessment score in 2015 was 3.88 in week 34. Public Education and Community Outreach Activities Peel Public Health has developed various educational resources about personal protective measures and individual and household activities that prevent or discourage the breeding of mosquitoes. The resources include flyers, fact sheets, posters, mailers and newspaper advertisements. These resource materials are made available on the Region of Peel Vector-Borne Disease website The website is also used to post WNV surveillance results, update larviciding activities and provide the public with access to the VBD Prevention Plan as well as annual reports dating back to As in previous years, educational materials on WNV were mailed to the following groups: long-term care facilities, child care centres, garden centres, golf courses, horticultural societies and multicultural associations. The only newspaper advertisement in 2015 was the larviciding application notice which is required by the MOECC. 17

20 In 2015, residents or organizations were encouraged to sign up at to receive notification of positive WNV activity in Peel. In addition, the electronic WNV notification database for institutions and for parks and recreation facilities that were located within a one kilometre range of each of the 31 fixed mosquito trap sites continued to be utilized. An was sent to institutions and to parks and recreation facilities when a positive mosquito batch was reported in their area. There was also one Health Professionals Update on WNV that was distributed to physicians in the region of Peel in The Health Professionals Update can be found at: Eastern Equine Encephalitis Eastern Equine Encephalitis, commonly referred to as EEE, is a viral disease of wild birds that is transmitted to horses and humans by mosquitoes. Of the North American mosquito-borne diseases, EEE appears to be the most severe human pathogen; approximately 33% of people who develop EEE die of the disease and many survivors have long-term health effects. In Ontario, outbreaks of EEE have occurred sporadically among horses, but no human cases have ever been confirmed. The lack of verified human cases of EEE in Ontario is not entirely understood, since human cases have repeatedly been reported in several states bordering the province. In 2015, there was no EEE positive mosquito pools reported in Ontario; however, there were five equine cases reported in the province (data as of November 23, 2015). Adult mosquito surveillance conducted over the last several years has found the key zoonotic species for EEE, Culiseta melanura, to be present in Peel but in very low numbers. In 2015, Peel Public Health continued to monitor the prevalence and distribution of Cs. melanura using the region-wide adult mosquito CDC light trap network. In 2015, two Cs. melanura were found in the CDC light traps, one was found in central Brampton and one in north Caledon. Both mosquitoes tested negative for EEE. In 2015, Peel Health relied upon adult and larval mosquito surveillance data in decisionmaking about EEE public education and mosquito reduction activities. 18

21 Lyme Disease In 2015, Public Health Ontario identified 16 Lyme disease risk areas in the province. Risk areas identify where black-legged ticks are most likely to occur. The risk area closest to Peel region is the Rouge Valley. It should be noted that ticks can be spread by birds, in particular, songbirds that feed off the ground. Because these birds are migratory, there is the potential for new populations of ticks to spread across the province. Therefore, one does not necessarily have to be in a high-risk area to be at risk of encountering ticks and the disease. In 2015, two confirmed Lyme disease cases were reported in Peel; both were associated with travel (eastern Ontario and north east United States). Active tick surveillance was undertaken at three sites, two in Mississauga and one in Brampton. The tick dragging sessions did not identify any ticks. In 2015, Peel Public Health continued passive tick surveillance by examining ticks brought into Peel Public Health offices by the public. Thirty-three tick samples were submitted to Peel Public Health: 8 Ixodes scapularis - black-legged tick (one positive found in eastern Ontario, one pending PHAC testing for Borrelia burgdorferi) 19 Dermacentor variabilis - dog tick 1 Amblyomma americanum - Lone Star tick (found in North Carolina) 2 Ixodes cookei- groundhog tick 1 Ixodes marxi - squirrel tick 2 ticks awaiting identification results from Public Health Ontario laboratory (as of December 22, 2015). Specimens associated with human contact were submitted to the Central Public Health Laboratory (CPHL) in Toronto for species confirmation. Eight black-legged ticks were sent to the Public Health Agency of Canada s (PHAC) National Microbiology Laboratory in Winnipeg for Lyme disease testing. As of December 22, one black-legged tick was found to be positive for Borrelia burgdorferi. The positive tick was submitted by a resident that came in contact with the tick in eastern Ontario. Laboratory results for two additional confirmed black legged ticks that have been submitted to PHAC are pending as of December 22, Table 8 shows the number of Peel residents that have contracted Lyme disease since

22 Table 8: Lyme Disease Cases in the Region of Peel, Confirmed Year Cases There are concerns that changes of climatic conditions such as warmer seasons could lead to conditions that are favourable for the establishment of black-legged tick populations in many parts of the province. The expansion of the black-legged tick population would likely result in an increase in human cases in the province. Program Evaluation Peel s VBD team manager and supervisor meet at the end of each season to identify needs and program improvements. Some program key needs/improvements that were identified for 2015 include: The larviciding contractor should complete the treatment all catch basins in municipal parks and at regional facilities within the first two weeks of June, prior to the start of the roadside catch basin program. This will allow the larviciding contractor to dedicate more resources to the roadside catch basin program. The larviciding contractor should provide better quality marker paint that is resistant to wearing. This will assist VBD staff during roadside catch basins quality assurance inspections. 20

23 Conclusion Surveillance activities continue to indicate that WNV is endemic in Peel and it is reasonable to assume that the virus will return to Peel at some level in Peel Public Health will continue to conduct surveillance, public education and larval mosquito reduction activities as these are essential WNV program components in a jurisdiction where WNV has been detected in a previous season. Peel Public Health will also continue public and physician education on Lyme disease symptoms, testing and prevention activities in In addition, if an established tick population is identified or there is evidence of a confirmed case of Lyme disease that has been acquired locally, then active surveillance including tick dragging will be undertaken. In 2016, Peel Public Health will also continue to monitor the prevalence and distribution of EEE vector mosquitoes by using the regional mosquito trapping network. 21

24 Appendix A Provincial Surveillance for West Nile Virus Case Definitions Provincial Surveillance for West Nile Virus (WNV) Section A: Case Definitions The current Case Definitions were drafted with available information at the time of writing. Case Definitions and Diagnostic Test Criteria are subject to change as new information becomes available. 1) West Nile Virus Neurological Syndrome (WNNS): Clinical Criteria: History of exposure in an area where WN virus (WNV) activity is occurring 1 OR history of exposure to an alternative mode of transmission 2 AND onset of fever AND NEW ONSET OF AT LEAST ONE of the following: encephalitis (acute signs of central or peripheral neurologic dysfunction) viral meningitis (pleocytosis and signs of infection e.g. headache, nuchal rigidity) acute flaccid paralysis (e.g. poliomyelitis-like syndrome or Guillain-Barré-like syndrome 3 ) movement disorders (e.g., tremor, myoclonus) Parkinsonism or Parkinsonia like conditions (e.g., cogwheel rigidity, bradykinesia, postural instability) other neurological syndromes as defined in the note below 1 History of exposure when and where West Nile Virus transmission is present, or could be present, or history of travel to an area with confirmed WNV activity in birds, horses, other mammals, sentinel chickens, mosquitoes, or humans. 2 Alternative modes of transmission, identified to date, include: laboratory-acquired; in utero; receipt of blood components; organ/tissue transplant; and, possibly via breast milk. 3 A person with WNV-associated acute flaccid paralysis may present with or without fever or mental status changes. Altered mental status could range from confusion to coma with or without additional signs of brain dysfunction (e.g. paralysis, cranial nerve palsies, sensory deficits, abnormal reflexes, generalized convulsions and abnormal movements). Acute flaccid paralysis with respiratory failure is also a problem. Note: A significant feature of West Nile viral neurologic illness may be marked muscle weakness that is more frequently unilateral, but could be bilateral. WNV should be considered in the differential diagnosis of all suspected cases of acute flaccid paralysis with or without sensory deficit. WNVassociated weakness typically affects one or more limbs (sometimes affecting one limb only). Muscle weakness may be the sole presenting feature of WNV illness (in the absence of other 22

25 neurologic features) or may develop in the setting of fever, altered reflexes, meningitis or encephalitis. Weakness typically develops early in the course of clinical infection. Patients should be carefully monitored for evolving weakness and in particular for acute neuromuscular respiratory failure, which is a severe manifestation associated with high morbidity and mortality. For the purpose of WNV Neurological Syndrome Classification, muscle weakness is characterized by severe (Polio-like), non-transient and prolonged symptoms. Electromyography (EMG) and lumbar puncture should be performed to differentiate WNV paralysis from the acute demyelinating polyneuropathy (Guillain-Barré syndrome). Lymphocytic pleocytosis (an increase in WBC with a predominance of lymphocytes in the cerebrospinal fluid [CSF]) is commonly seen in acute flaccid paralysis due to WNV. Other emerging clinical syndromes, identified during 2002 included, but were not limited to the following: myelopathy, rhabdomyolysis (acute destruction of skeletal muscle cells), peripheral neuropathy; polyradiculoneuropathy; optic neuritis; and acute demyelinating encephalomyelitis (ADEM). Ophthalmologic conditions including chorioretinitis and vitritis were also reported. Facial weakness was also reported. Myocarditis, pancreatitis and fulminant hepatitis have not been identified in North America, but were reported in outbreaks of WNV in South Africa. Aseptic meningitis without encephalitis or flaccid paralysis occurring in August and September when WNV is circulating may be due to non-polio enteroviruses circulating at the same time. This should be considered in the differential diagnosis. [Sejvar J et al. JAMA (2003) Vol.290 (4) p , Sejvar, J. et al. Emerg Infect Dis (2003) Vol 9 (7) p and Burton, JM et al Can. J. Neurol. Sci. (2004) Vol.31 (2) p ] Suspect WN Neurological Syndrome Case: Clinical criteria IN THE ABSENCE OF OR PENDING diagnostic test criteria (see below) AND IN THE ABSENCE of any other obvious cause. Probable WN Neurological Syndrome Case: Clinical criteria AND AT LEAST ONE of the probable case diagnostic test criteria (see below). Confirmed WN Neurological Syndrome Case: Clinical criteria AND AT LEAST ONE of the confirmed case diagnostic test criteria (see below). 2) West Nile Virus Non-Neurological Syndrome (WN Non-NS): Clinical Criteria: History of exposure in an area where WN virus (WNV) activity is occurring 1 OR history of exposure to an alternative mode of transmission 2 AND AT LEAST TWO of the following 5 : fever, myalgia 6, arthalgia, headache, fatigue, 23

26 lymphadenopathy, maculopapular rash 1 History of exposure when and where West Nile Virus transmission is present, or could be present, or history of travel to an area with confirmed WNV activity in birds, horses, other mammals, sentinel chickens, mosquitoes, or humans. 2 Alternative modes of transmission, identified to date, include: laboratory-acquired; in utero; receipt of blood components; organ/tissue transplant; and, possibly via breast milk. 5 It is possible that other clinical signs and symptoms could be identified that have not been listed and may accompany probable case or confirmed case diagnostic test criteria. For example, gastrointestinal (GI) symptoms were seen in many WNV patients in Canada and the USA in 2003 and Muscle weakness may be a presenting feature of WNV illness. For the purpose of WNV Non- Neurological Syndrome classification, muscle weakness or myalgia (muscle aches and pains) is characterized by mild, transient, unlikely prolonged symptoms that are not caused by motor neuropathy. Suspect WN Non-Neurological Syndrome Case: Clinical criteria IN THE ABSENCE OF OR PENDING diagnostic test criteria (see below) AND IN THE ABSENCE of any other obvious cause. Probable WN Non-Neurological Syndrome Case: Clinical criteria AND AT LEAST ONE of the probable case diagnostic test criteria (see below) Confirmed WN Non-Neurological Syndrome Case: Clinical criteria AND AT LEAST ONE of the confirmed case diagnostic test criteria (see below) 3) West Nile Virus Asymptomatic Infection (WNAI) 7 : Probable WN Asymptomatic Infection Case: Probable case diagnostic test criteria (see below) IN THE ABSENCE of clinical criteria Confirmed WN Asymptomatic Infection Case: Confirmed case diagnostic test criteria (see below) IN THE ABSENCE of clinical criteria 7 This category could include asymptomatic blood donors whose blood is screened using a Nucleic Acid Amplification Test (NAT), by Blood Operators (i.e. Canadian Blood Services or Hema- Quebec) and is subsequently brought to the attention of public health officials. The NAT that will be used by Blood Operators in Canada is designed to detect all viruses in the Japanese 24

27 encephalitis (JE) serocomplex. The JE serocomplex includes WN virus and 9 other viruses, although from this group only WN virus and St Louis encephalitis virus are currently endemic to parts of North America. Blood Operators in Canada perform a supplementary WN virus-specific NAT following any positive donor screen test result. 25

28 Section B: West Nile Virus Diagnostic Test Criteria: Probable Case Diagnostic Test Criteria: AT LEAST ONE of the following: 8 Detection of flavivirus antibodies in a single serum or CSF sample using a WN virus IgM ELISA 8 without confirmatory neutralization serology (e.g. Plaque Reduction Neutralization Test [PRNT]) OR A 4-fold or greater change in flavivirus HI titres in paired acute and convalescent sera or demonstration of a seroconversion using a WN virus IgG ELISA 8 OR A titre of > 1:320 in a single WN virus HI test, or an elevated titre in a WN virus IgG ELISA, with a confirmatory PRNT result OR [Note: A confirmatory PRNT or other kind of neutralization assay is not required in a health jurisdiction/authority where cases have already been confirmed in the current year] Demonstration of Japanese encephalitis (JE) serocomplex-specific genomic sequences in blood by NAT screening on donor blood, by Blood Operators in Canada. Both CDC and commercial IgM / IgG ELISAs are now available for front line serological testing. Refer to appropriate assay procedures and kit inserts for the interpretation of test results. Note: WNV IgM antibody may persist for more than a year and the demonstration of IgM antibodies in a patient s serum, particularly in residents of endemic areas, may not be diagnostic of an acute WN viral infection. Seroconversion (by HI, IgG ELISA or PRNT assays) demonstrates a current WNV infection. Therefore, the collection of acute and convalescent sera for serologic analysis is particularly important to rule out diagnostic misinterpretation early in the WNV season (e.g. May, June) and to identify initial cases in a specific jurisdiction. However, it should be noted that seroconversions may not always be documented due to timing of acute sample collection (i.e. titres in acute sera may have already peaked). If static titres are observed in acute and convalescent paired sera, it is still possible the case may represent a recent infection. To help resolve this, the use of IgG avidity testing 9 may be considered to distinguish between current and past infection. The presence of both IgM antibody and low avidity IgG in a patient s convalescent serum sample are consistent with current cases of viral associated illness. However test results that show the presence of IgM and high avidity IgG are indicative of exposures that have occurred in the previous season. Immunocompromised individuals may not be able to mount an immune response necessary for a serological diagnosis. West Nile Virus diagnostic test criteria for these individuals should be discussed with a medical microbiologist. 26

29 9 Early in infection the immune system generates antibodies that bind relatively weakly to viral antigen (low avidity). As the infection proceeds, an increasing percentage of newly generated IgG antibody displays higher binding affinity to virus antigen and thus avidity also rises (Note: avidity is usually measured based upon the ability of IgG to dissociate from antigen preparations after incubation with a solution of urea). As long as high avidity IgG is not yet detected in the serum it can be assumed that the individual was exposed to the viral agent during a recent exposure. With respect to WNV infection it has not been precisely determined when (i.e. post-exposure) high avidity antibodies reach levels in serum that can be accurately detected by serological assays (there may be significant variation depending on the individual). However, it has been shown that greater than 95% of sera collected from individuals exposed to WNV 6-8 months previously will have IgG antibodies that bind strongly to viral antigen and will give high avidity scores using both IFA and ELISA testing formats. Note: Avidity testing will not replace confirmatory neutralization testing, non-wnv flavivirus IgG antibody (Eg. dengue, SLE, etc.) may bind to the antigen preparations used in avidity assays. Confirmed Case Diagnostic Test Criteria: It is currently recommended that health jurisdictions/authorities use the Confirmed Case Diagnostic Test Criteria to confirm index cases (locally acquired) in their area each year; for subsequent cases, health jurisdictions/authorities could use the Probable Case Diagnostic Test Criteria to classify cases in their area as confirmed, for the purposes of surveillance. Throughout the remainder of the transmission season health jurisdictions/authorities may wish to document PRNT antibody titres to West Nile Virus in a proportion of cases, to be determined by that health jurisdiction/authority, in order to rule-out the possibility of concurrent activity by other flaviviruses. [For further information on diagnostic testing algorithms for West Nile Virus, see the section entitled Laboratory Specimen Diagnostic Testing Algorithm in Appendix 4 of the National Guidelines for Response to West Nile Virus.] AT LEAST ONE of the following: A 4-fold or greater change in WN virus neutralizing antibody titres (using a PRNT or other kind of neutralization assay) in paired acute and convalescent sera, or CSF. OR Isolation of WN virus from, or demonstration of WN virus antigen or WN virus-specific genomic sequences in tissue, blood, CSF or other body fluids Demonstration of flavivirus antibodies in a single serum or CSF sample using a WN virus IgM ELISA 8, 9, confirmed by the detection of WN virus specific antibodies using a PRNT (acute or convalescent specimen). OR A 4-fold or greater change in flavivirus HI titres in paired acute and convalescent sera or demonstration of a seroconversion using a WN virus IgG ELISA 8, 9 AND the detection of WN specific antibodies using a PRNT (acute or convalescent serum sample). OR 27