31% of ticks tested in a study carried anaplasmosis transmissible to humans

Nearly one in three ticks collected and analyzed by sequencing on white-tailed deer in southern Quebec by a team from the Public Health Agency of Canada is infected with the anaplasmosis variant transmissible to humans. This bacteriological infection can in particular cause a strong outbreak of fever and certain complications for more vulnerable people.

These recently confirmed laboratory data were sent to the veterinary epidemiologist at the Public Health Agency of Canada, Catherine Bouchard, and will soon be the subject of a scientific publication.

It was his team that collected hundreds of ticks, in 2023, from 246 white-tailed deer shot by hunters in several regions of southern Quebec, including Estrie, Montérégie and Centre-du-Québec. This is work carried out in collaboration with the University of Montreal.

It is not for nothing that we have human cases; This is because it is increasingly present in the environment.

Of 201 ticks tested by sequencing, 31.3% were infected with the zoonotic variant of anaplasmosis, that is, the one transmissible to domestic animals and humans. The team will also soon have new data from a second sampling campaign which concluded last weekend.

From 0% to 31.3% in a few years

The zoonotic variant had not been detected during a similar sampling campaign carried out by Catherine Bouchard in 2007 and 2008, also on ticks present on deer in southern Quebec.

Anaplasmosis therefore seems to be gaining ground. Not only in Quebec, but in Ontario, in the Maritimes, underlines the researcher. This has emerged more and more in the last four years.

Cases of citizens who have contracted the disease have been increasing since 2019. In 2023, 46 cases of anaplasmosis have been recorded in Quebec, including 27 in Estrie. According to the National Institute of Public Health of Quebec (INSPQ), it is in 2021 that a first peak with 45 cases was reported. In 2019, when anaplasmosis was added to the list of notifiable diseases, only one case was reported.

The risk is increasing especially for southern Quebec, but now it also extends north of the St. Lawrence River, which we did not see before.

According to research agent at the University of Montreal Élisabeth Dyre, who is part of Catherine Bouchard’s team, vigilance is essential during our walks in the forest. There are more and more risks. What we see is that the number of ticks increases in regions where there were already some, and that we find ticks where we did not find them before.

Anaplasmosis causes flu-like symptoms but can cause serious complications if left untreated. The blacklegged ticks that transmit this infection are also those that can carry Lyme disease.

The deer like sentinel

Catherine Bouchard explains that the choice to study ticks present on deer carcasses greatly facilitates the research work. No need to go to the forest, or even capture animals alive.

The team is stationed at different butcher shops in the region which receive the hunters’ catches during the hunting season and who agree to collaborate in the research. A sample of blood and tissue is then taken in a few minutes on site, in addition to the ticks present on the animal.

There is no need to stress living animals, emphasizes research agent Élisabeth Dyre. These animals, hunters will hunt them the same. This gives us an opportunity to sample them to take the pulse of the situation.

Since the location where the deer were killed is communicated by the hunters, the team will be able to map the presence of anaplasmosis in the territory. We see places we suspected like Haute-Yamaska [Réseau local de services en Estrie]La Pommeraie [Réseau local de services en Estrie]but also towards the northeast of Estrieunderlines Catherine Bouchard.

We will be able to paint a picture of how anaplasmosis emerges in Quebec.

The team’s objective is to communicate to decision-makers the sectors where anaplasmosis has been detected to promote an effective control strategy. I will have a list of municipalities to provide where I have found positive samples, explains Catherine Bouchard. It can be used to clearly design future surveillance programs for tick-borne diseases.

Could deer be reservoirs for the disease?

Research so far shows that rodents, such as the eastern chipmunk and the white-footed mouse, are vectors of the infection, according to Catherine Bouchard. Ticks that bite these infected animals can then transmit the disease to humans.

Catherine Bouchard today hypothesizes that deer could also be a vector of contamination. Tissues and blood taken from these animals in 2023 show that some deer also carry the infection. This would be the first time that this hypothesis has been publishedshe exclaims.

It’s a hypothesis we have. The deer would have a certain competence as a reservoir to retransmit the infection.

If this hypothesis were to be proven, this could partly explain why the proportion of ticks contaminated with this variant is so significant in the current study.

Such a situation would also invite reflection. It would change the way we look at epidemiological cycles in nature she underlines, while insisting on the fact that everything still remains to be demonstrated.

Catherine Bouchard would like to verify, as part of future work, whether deer can be a reservoir to maintain the infection and transmit it back to ticks in the environment.