Report No. 052-12

TO: Chair and Members of the Board of Health
FROM: Graham L. Pollett, MD, FRCPC, Medical Officer of Health
DATE:   2012 April 19

2011 Vector-Borne Disease Report: West Nile Virus, Lyme Disease And Eastern Equine Encephalitis Surveillance And Control Activities For 2011

Recommendation

It is recommended that Report No. 052-12 re 2011 Vector-Borne Disease Report: West Nile Virus, Lyme Disease and Eastern Equine Encephalitis Surveillance and Control Activities for 2011 (Full PDF Report(PDF 8.9MB)) be forwarded for information to London City Council, Middlesex County Council and the Councils of Middlesex Municipalities. 

2011 Vector-Borne Disease Program

In 2011, the Health Unit’s Vector-Borne Disease (VBD) Program was focused on facilitating a comprehensive program to address all VBD’s of significance in Ontario, including West Nile Virus (WNV), Lyme Disease (LD) and Eastern Equine Encephalitis (EEE). This comprehensive surveillance and control program was comprised of larval mosquito surveillance and identification, larviciding, adult mosquito trapping, dead bird collection, human surveillance, source reduction, public education, responding to public inquiries, tick surveillance and research into alternative treatment methods. The 2011 Final Report (Appendix A) outlines surveillance and control activities for the 2011 season. This Board Report summarizes the highlights of the 2011 Final Report.

Human Health

In 2011, the Health Unit had two reported human cases of WNV; one case was confirmed while the other case was considered probable. Appendix E of the Final Report contains criteria for WNV diagnosis. In Ontario, there were 72 confirmed cases of WNV in 2011. This was a significant increase from the past few seasons. The public submitted 73 ticks for identification, and two of the submissions were identified as blacklegged ticks. One tick was acquired within London; the other submission was acquired in Brockville, a known endemic area. However, both ticks tested negative for Borrelia burgdorferi, the causative bacteria of LD. There were two confirmed human LD cases in Middlesex-London, both of which were travel-related. One case was exposed during travel to Turkey Point and the other was exposed while at Rondeau Provincial Park.

Mosquito Identification, Control and Viral Testing

In 2011, the VBD Team collected approximately 148,599 mosquitoes by conducting weekly trapping at various locations throughout the London and Middlesex County. Cosray Laboratories identified 20,942 adult mosquitoes and performed 1,101 viral tests for WNV and EEE. Eighty-six percent (86%) of the adult mosquitoes identified were vectors, and only 14% were non-vector. There were eleven WNV- positive pools identified in Middlesex-London. In Ontario, 278 positive mosquito pools were identified, a significant increase over the 56 positive pools that were identified in 2010. There were no EEE-positive mosquito pools but trapping did show that EEE vector mosquitoes were present in large numbers in Middlesex-London. Province-wide, there were no EEE-positive mosquito pools identified but there were 4 confirmed equine cases of EEE. The VBD Team performed 919 treatments at 247 standing water sites.  Approximately 11.75 hectares of standing water were treated using a biological larvicide. As in previous years, approximately 33,000 catch basins were treated in 3 evenly spaced rounds throughout the season to ensure optimal control during the most crucial times of mosquito amplification. An additional 1,100 non-roadside catch basins located in rear yards of residential properties, in municipal green-spaces and catch basins located on sites such as hospitals, government buildings, social housing units, and long-term care facilities, were also treated.

Dead Bird Testing

This season, 143 dead bird sightings were made in Middlesex-London. Of the 143 sightings, only 26 birds were in a condition to be tested in the Health Unit lab where results yielded 9 WNV-positive crows. The positive samples were confirmed by the Canadian Cooperative Wildlife Health Centre.

Public Education and Promotion

Public education remained a vital component to the VBD program once again this season. Health Unit staff members participated in several community events, distributed promotional and educational resources and received frequent press coverage by local media. The WNV Reduce and Repel brochure and LD brochures were distributed to physicians’ offices, garden centres and municipal offices throughout London and MiddlesexCounty. The brochures contained basic information about the diseases, including preventing mosquito breeding and protecting against mosquito bites and tick exposure. A television commercial and transit shelter ads were developed to help increase awareness about LD and educate the public on how to protect against tick bites and exposure in endemic areas.

Planning for 2012

In 2012, the VBD program will continue to utilize an Integrated Pest Management approach to reduce the risk of WNV, LD and EEE to humans. Public education remains vital to reducing breeding sites, limiting transmission of these diseases and ultimately in preventing death and long-term side effects of the viruses. Staff will continue to utilize the Canadian Centre for Mosquito Management for mosquito control and Cosray Laboratories for adult mosquito identification and viral testing.

Conclusion

The risk of exposure to West Nile Disease, Lyme Disease and Eastern Equine Encephalitis is based on evidence that these vector-borne diseases are present in bird populations, equines, mosquito pools and humans. The Vector-Borne Disease Team strives to mitigate the risk of these diseases by conducting surveillance and control as well as developing new strategies to reduce the amplification of Vector-Borne Diseases. In 2012, the Team aims to inform, educate and reduce the risk of vector-borne diseases to the public.

This report was prepared by Mr. Jeremy Hogeveen, Coordinator, Vector-Borne Disease Program, and Mr. Iqbal Kalsi, Manager, Environmental Health.

Graham L. Pollett, MD, FRCPC

Medical Officer of Health

This report addresses the following requirements of the Ontario Public Health Standards:  
Section 7(c)(i) of the Infectious Diseases Protocol requiring the Board of Health to develop an integrated vector-borne management plan which shall be comprised of vector surveillance.
Section 8 of the Health Hazard Prevention and Management Standard requiring the Board of Health to develop a local vector-borne management strategy based on surveillance data and emerging trends in accordance with the Infectious Diseases Protocol, 2009.