Vector-borne Diseases in Ontario — Annual Update


26 July 2017

What are vector-borne diseases?

Vector-borne diseases are infections that are transmitted by a vector such as a mosquito, tick or flea. The most common types of vector-borne diseases in Ontario are:

  • West Nile virus: a virus transmitted through the bite of an infected mosquito. It was first detected in Ontario in birds in 2001, with the first human cases following in 2002. 
  • Lyme disease: an infection transmitted through the bite of an infected tick. In Ontario, the majority of these human cases have occurred in areas associated with the blacklegged tick populations.
  • Eastern equine encephalitis virus (EEEV): a virus that circulates between birds and mosquitoes, with bridge vectors (mosquitos) transmitting the virus to humans and horses. EEEV has been reported in Ontario’s horse population since the 1930s; however, the virus has been detected sporadically in the Ontario mosquito population since 2009.

Annual trends in vector-borne diseases

It’s important to monitor the trends in vector-borne diseases across the province. That’s why every year, with support and routine surveillance from the local public health units in Ontario, we publish our annual report on vector-borne diseases. We are happy to announce the release of the Vector-Borne Diseases: 2016 Summary Report, which provides an overview of the 2016 data on the vectors that transmit West Nile virus, EEEV and Lyme disease in Ontario.

Interesting findings from the report:

  • There was an increase in West Nile virus positive mosquito pools over the last two years – with 211 positive pools identified in 2016.
  • While human data are not included in this report, it was noted that Ontario had the first ever human case of EEEV reported in Canada.
  • There was an increase in the number of blacklegged ticks submitted to PHO from 1,903 in 2015 to 2,041 in 2016.

Please note that human data are not included in this report. However this information is still available on our website through the Infectious Diseases Query tool and Reportable Disease Trends in Ontario.

Additional resources 

We offer a number of great resources and tools on vector-borne diseases. Check out our interactive West Nile virus surveillance page (updated weekly) or our Lyme disease page for more information.

Stay tuned to our PHO in Action blog for more vector-borne disease posts in the coming weeks.

Questions about the report?

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Updated 26 July 2017