Lyme disease is on the rise, both provincially and in Wellington-Dufferin-Guelph.
Twenty cases of Lyme disease were reported in humans in 2023 – twice the annual amount reported from 2018 to 2020, according to a Wellington-Dufferin-Guelph Public Health report, compared to 17 in 2022 and 12 in 2021.
Just under half of those cases may have been transmitted by ticks found outside of Guelph, and in eight of the 20 cases, the exposure site was likely a residential property.
Lyme disease is the most common vector-borne disease in North America, the report says, with early symptoms like fever, fatigue and skin rash. If untreated it can spread and cause serious illness.
To transmit it, a tick must be attached to a person and feeding for at least 24 hours.
The best prevention is to avoid tick bites by using insect repellent, covering up, checking for ticks and safely removing them as soon as possible if bitten.
More frequent warm weather means tick populations are growing, and venturing into new areas.
WDGPH’s 2023 passive surveillance program saw 202 tick submissions in 2023. Ninety of them were blacklegged ticks, which are the primary carriers of Lyme disease and other rare but serious illnesses like Anaplasmosis.
Ticks are monitored through tracking and identifying ticks submitted by the public, and “tick dragging to collect ticks from their habitats,” which are then tested.
An online tool where community members could submit photos of and answer questions about ticks was also launched in May 2023 to improve data collection in WDG.
Most submitted ticks were blacklegged ticks or American dog ticks, and most blacklegged ticks were reported to be found already attached to a person, adult female ticks, and engorged, meaning it had been attached and feeding.
More than half of blacklegged ticks were suspected to have been found locally, and around 25 per cent of ticks found locally were suspected to have been picked up on residential properties.
WDG wasn’t identified as a risk area for ticks in 2017 in the Ontario Lyme Disease Map.
“Risk areas have quickly grown throughout Ontario and in 2023 estimated risk areas overlap with the southeastern and northeastern edges of Wellington-Dufferin-Guelph,” the report says. Infected ticks can still be found outside of the shown areas, though.
The report attributes the growing risk areas to rising temperatures that stick around longer.
“Ticks are expanding into regions where they were once uncommon and are expected to continue to expand northward,” the report says.
About half of the ticks submitted to the program are blacklegged ticks, and half of those are suspected to have been found locally.
The report notes data collection was not as comprehensive from 2020 to early 2023
because of the pandemic, so the number of locally required ticks are likely under-reported during that time.
Still, Lyme disease is becoming more common in humans, largely due to climate change, and cases are expected to continue to increase.
Warmer and wetter weather means more mosquitoes, too.
Last year three mosquito pools in Wellington-Dufferin-Guelph tested positive for West Nile virus, although no human cases were reported.
West Nile is transmitted through the bite of an infected mosquito, and typically causes mild and flu-like symptoms, although it can lead to more serious illnesses.
The number of positive mosquito pools and human West Nile infections have remained low in recent years. In 2023, there were three positive mosquito pools and no human cases. Since 2018 there have only been six positive pools and three human cases.
Public health is working with the Grand River Conservation Authority to potentially design and post educational signs at local trails and parks to raise awareness about ticks, and plans to launch a dashboard with live and historic data sets to keep the community informed on vector-borne diseases like West Nile and Lyme disease.
It is also potentially partnering with Conestoga College to pilot new testing technology for West Nile virus and other diseases.
“We will be piloting research collecting water samples from standing water sites to test for mosquito DNA to identify what types of mosquitoes are in our region,” said public health spokesperson Danny Williamson. “This will inform potential deployment of more traps, or movement of current trap locations to more suitable habitats.”
This type of DNA sampling will support public health in monitoring the community for specific mosquito species that can spread West Nile and other diseases like Eastern Equine Encephalitis (EEE), a serious illness with a high fatality rate, transmitted from birds to humans through mosquitoes.
A joint federal grant for environmental sampling with Conestoga has been submitted, and if approved, will be rolled out in 2025, he said.
