As temperatures drop and nights grow cooler, another tick-borne threat is climbing alongside the more familiar Lyme disease — and health officials say it’s often harder to catch early and more dangerous once it takes hold. The black-legged (deer) tick, already known as Quebec’s top spreader of Lyme disease, is also spreading anaplasmosis at a growing rate. It’s the second most common tick-borne illness in the province, infecting humans, horses and dogs alike. “Anaplasmosis is transmitted by this bacteria called Anaplasma phagocytophyllum,” said Quebec Institute of Public Health (INSPQ) scientific adviser Kristen Crandall. “It’s very similar to Lyme disease in that it’s also a bacteria. It’s the same tick vector, but the symptoms tend to be a little bit different.” More severe than Lyme Crandall said that though it’s not nearly as prevalent as Lyme disease, it is “quite a bit more severe.” “Because it’s sort of not as pronounced, so it can take a little bit longer to get diagnosed, which can lead to those more late symptoms,” she said. “That’s why people tend to get onto their treatments a little bit later sometimes, and that’s why it can lead to more severe complications because their body is already trying to fight against a disease that can spread relatively quickly.” Early symptoms, Crandall explained, are flu-like: fever, chills, headaches, and muscle pains. Later symptoms can be more severe, including organ failure, respiratory failure and neurological manifestations. The Canadian Medical Journal reports that the disease’s effects can also include myocarditis, encephalitis, and acute renal failure. The INSPQ says that between 2019 and 2024, almost half (43 per cent) of the 101 human cases of anaplasmosis required hospitalization. However, the fatality rate is less than one per cent. Unlike Lyme disease, there is no preventative treatment for anaplasmosis and the transmission window is short. “The bacterium can be transmitted by an infected tick even if the tick is removed within 24 hours,” the INSPQ says. Rising in lock-step with Lyme disease So far in 2026, Quebec’s Health Ministry has reported 50 cases of the disease, meaning it’s on pace to increase from 2025, when 71 cases were reported in the province. In 2025, a total of 869 cases of Lyme disease were reported. The 2025 number was almost double the 37 anaplasmosis cases the year prior in 2024, the same year that 728 Lyme disease cases were reported. “We’ve seen much more recently in the past few years that that increase has been a little bit greater than previously,” said Crandall. The Health Ministry said that most cases were reported in the Eastern Townships and Montérégie areas. Quebec trails only Ontario and Nova Scotia in tick-borne disease numbers. American border states Maine, New York, and Vermont are three of the eight states in the U.S. reporting 90 per cent of anaplasmosis cases in the country. The disease was first identified in Scotland in 1932 and was detected in California in 1969. The first case in Canada was reported in Alberta in 2009 and it appeared in Quebec in 2019. Sixteen cases in horses and dogs were reported in five regions of Quebec. Get them off fast Experts agree that ticks are not going anywhere and the numbers show that the diseases they spread will only increase. “We have to learn to adapt, and that’s why putting in place those preventative measures, making them part of your routine, especially if you’re in high-risk areas,” said Crandall, who always has a case on hand with three sets of tweezers and a pill container to put the tick in. “The quicker the tick is off of you, the better chances you have of not being sick with any of these different tick-borne diseases,” she said. In addition, the following are good habits to develop: Though the numbers aren’t high for anaplasmosis at the moment, the INSPQ and other health and wildlife organizations are working to identify cases, understand the situation and make recommendations. “Eventually, those two (Lyme and anaplasmosis) will be coming in greater and greater numbers, and we just have to be very aware of it,” said Crandall. “We like to make sure that we’re aware of the situation, keeping our eyes on what’s going on, so that we can then make recommendations, or we can help the best that we can the population to ensure that they don’t get sick with these different diseases.”
