Canadian dairy producers are encouraged to stay informed about the Asian longhorned tick, an invasive parasite spreading in U.S. states near the Canadian border. Although the tick has not been detected in Canada, experts say awareness is important.
This is because the parasite the tick can carry — Theileria orientalis Ikeda — was confirmed in an imported dairy cow in October 2025. As a result, the finding highlights the need for early awareness and prevention planning.
What is the Asian longhorned tick?
The Asian longhorned tick (Haemaphysalis longicornis) is a fast-reproducing tick that can build large populations in livestock environments. In regions where it has become established, it has caused heavy tick infestations and increased disease risk.
Most importantly for dairy producers, this tick can transmit Theileria orientalis Ikeda. This parasite infects red blood cells and leads to bovine theileriosis.
Why this matters for dairy herds
Infected cattle may show clear signs of illness. These include:
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Fever and low energy
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Anemia
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Reduced milk production
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Reproductive challenges
However, not all infections appear obvious at first. Even mild or hidden cases can affect long-term production and herd performance. For this reason, early detection matters in high-producing dairy systems.
New fact sheet now available
To support dairy producers, a new fact sheet explains how to recognize risks and take practical steps early. Specifically, it covers:
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What to watch for in your herd
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Key signs of bovine theileriosis
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Simple ways to reduce risk
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How and where to report ticks
The fact sheet was produced by Animal Health Canada in collaboration with the Canadian Animal Health Surveillance System (CAHSS) Longhorned Tick Task Force to raise awareness and support preparedness across the dairy sector.
📄 Access the fact sheet here
