Anaplasmosis Second-Most Common Tick-Borne Disease in Canada

Anaplasmosis cases are increasing across Canada, establishing the infection as the second-most common tick-borne disease in the country ^[1].

This trend signals a growing public health challenge as the geographical reach of disease-carrying ticks expands. Because the symptoms of anaplasmosis can overlap with other infections, the rise in prevalence increases the risk of misdiagnosis or delayed treatment for those exposed to the outdoors.

The disease is caused by the bacterium Anaplasma phagocytophilum ^[2]. It is transmitted to humans through the bite of infected black-legged ticks, also known as deer ticks [1, 2]. These same ticks are responsible for spreading Lyme disease, which remains the most frequent tick-borne illness in the region ^[1].

Health officials have noted a rising trend in cases across eastern Canada ^[3]. Specifically, the increase is evident in Ontario, Quebec, and the Atlantic provinces, also known as the Maritimes [1, 2, 3]. Reports also indicate the presence of the disease in Manitoba [1, 2, 3].

The surge in infections is attributed to the expanding range of the black-legged tick [1, 2]. As these ticks migrate into new territories, more Canadians are coming into contact with the bacteria in wooded or grassy areas. This expansion has been particularly notable during the 2026 period [1, 2].

Public health guidance emphasizes the importance of tick prevention and early detection. Because the black-legged tick is the primary vector for both Lyme disease and anaplasmosis, the risk to the population grows as the tick's habitat widens across the Canadian landscape [1, 2].