Recent snapshot of ticks, pathogens, and mammalian hosts in Southern Ontario and Quebec

This study by Crandall et al. (2024) examines the factors influencing the presence of pathogen species in relation to its prevalence in Ixodes scapularis (the black-legged tick) and small mammal hosts in Ontario and Quebec. 

This new research highlights the importance of ongoing monitoring of ticks at all life stages and their hosts to better understand how tick-borne diseases are spreading in Canada.

Climate change and land use changes are spreading tick-borne diseases more widely across Canada. The spread of these diseases depends on the number and distribution of ticks and their animal hosts. In this study, relationships were examined between the pathogens found in black-legged ticks (Ixodes scapularis) and the mammals that host them in areas with varying levels of disease risk. Data was gathered from summer field surveys in 16 areas of southern Ontario and Quebec.

Statistical models were used to see how the number of ticks and the variety of mammal hosts influenced the presence and spread of five common pathogens. They found three types of pathogens in the ticks and small mammals using advanced testing methods: Borrelia burgdorferi (the Lyme bacterium), Babesia odocoilei, and Babesia microti.

The infection rates for these pathogens varied: from 0% to 25.4% in ticks and from 0% to 16.7% in small mammals. B. odocoilei was found in areas where it wasn’t previously known to exist, suggesting that it is spreading. Borrelia miyamotoi and Anaplasma phagocytophilum were also looked for but not found.

Interestingly, the number of ticks and the variety of mammal hosts didn’t affect the presence of the studied pathogens as they had expected. 

However, having a greater variety of mammal species was a good indicator of the number of different pathogens present. The authors note:

However, mammal species richness was a key predictor of the number of pathogen species. Our study demonstrates the need for future surveillance efforts that test questing and feeding I. scapularis of all life stages, as well as their hosts to better determine the spread, transmission, and co-occurrence of tick-borne pathogens in Canada. 

This study emphasizes the complex interactions between black-legged ticks, their mammalian hosts and the pathogens they carry.  Further surveillance studies will increase our understanding of pathogen transmission.  

In the meantime, tick vigilance is essential no matter where in the country Canadians are located.

Citation

Crandall, K. E., Kerr, J. T., & Millien, V. (2024). Pathogen Presence, Prevalence, and Diversity in Ixodes Scapularis and Mammal Hosts at Their Expanding Northern Range Limits. Frontiers in Parasitology, 2(11). doi:10.3389/fpara.2023.1272790.