Tick-borne diseases: tracking anaplasmosis

Residents of the Eastern Townships have known about Lyme disease for years, but now they must be wary of another disease carried by blackleg ticks: anaplasmosis. Last summer, 35 cases of the flu-like illness were reported in Eastern Townships, the most in all of Canada.

Anaplasmosis may be becoming more prevalent in Quebec, in part because climate change is lengthening tick lifespans, accelerating their life cycle and thereby increasing human exposure to the ticks.

The upward trend has caught the attention of a research team at the University of Montreal School of Veterinary Medicine. This summer, professors Catherine Bouchard, Cécile Aenishaenslin, Patrick Leighton and Jean-Philippe Rocheleau, together with Raphaëlle Audet-Legault, veterinarian and master’s student in epidemiology at UdeM, are conducting research to identify which species of small wild mammals are reservoirs of anaplasmosis and therefore contribute to the transmission of the disease to humans.

“The tick is like a used syringe,” explains Bouchard. “Let’s say he bit a mouse for his previous meal. Suppose the bacteria responsible for anaplasmosis were circulating in the mouse’s bloodstream. Now, when the tick bites a human, it infects him with the blood of the mouse. If the mouse carried a zoonotic variant, the human will become infected with the disease.”

mapping distribution

With help from the City of Bromont, the Estrie Department of Health and the Brome-Missisquoi Regional Borough, the team will be capturing rodents of various sizes (mice, chipmunks, squirrels) in the Bromont area over the summer to see which are most prevalent of anaplasmosis . The vets also collect ticks from the field to measure the percentage of infected ticks in the area.

Half of the sampling sites are in areas where human cases have occurred and half where there have been no cases. “We want to compare the proportion of infected small mammals near human cases and further away, and also determine whether the prevalence of infection varies by species,” Audet-Legault said.

“We are interested in the extent to which the circulation of the bacterium is curbed,” Bouchard added. “I wouldn’t be surprised if there wasn’t a difference between the sites near human cases and the rest. We may find that there are more human cases where the population density is higher but the disease is equally present elsewhere. The residents would therefore have to exercise the necessary vigilance.”

education for prevention

With the explosion of human cases of anaplasmosis, efforts to promote safer behaviors in exposed populations – such as Such as full-length clothing and routine self-checks after being outdoors — should be stepped up, Bouchard said.

Education efforts should not only target local residents, but also healthcare professionals, who should look beyond Lyme disease when diagnosing patients from high-risk areas.

Anaplasmosis is not easy to diagnose as symptoms are generally non-specific and mild, such as fever, chills, headache and muscle aches. Unlike Lyme disease, the tick bite does not leave the skin red.

Audet-Legault also pointed out that most people infected with anaplasmosis are bitten near their homes while gardening or engaging in similar activities. “In the eastern townships, many people have houses on the hillside, under a canopy of old trees. So you literally live in the habitat of the tick. We need to increase our awareness efforts as all residents are potentially at risk.”

As a first step, the research team met with Bromont residents to present their research project. Interactive workshops are planned for the summer.