Tick-borne risks are changing: What cattle producers should watch for

Ticks have long been part of livestock management in Canada, but the risk picture is changing.

The Asian longhorned tick has not been found established in Canada. However, Animal Health Canada reported that the parasite most closely associated with it — Theileria orientalis Ikeda — was confirmed in an imported dairy cow in October 2025. It was the first confirmed Canadian detection of the parasite and a reminder that tick-borne risks can move with animals before a new tick species becomes established.

At the same time, Canadian cattle already face tick-related risks closer to home. Native and established tick species can cause irritation, blood loss and production losses, and can transmit diseases such as bovine anaplasmosis. Some tick-borne diseases can also affect people, although T. orientalis Ikeda is not known to infect humans.

For producers, the message is not that a widespread new threat has arrived. It is that awareness, early detection and sound biosecurity matter as ticks, animals and the diseases they may carry continue to move.

Asian longhorned tick remains an emerging concern

The Asian longhorned tick is native to eastern Asia but has spread to Australia, New Zealand and a growing area of the United States. It has now been detected across much of the eastern U.S. and as far west as Missouri, with additional detections continuing to be reported.

Its ability to reproduce without mating makes it particularly difficult to control. A single female can establish a new population, and heavy infestations can involve hundreds or even thousands of ticks on an animal. In severe cases, the ticks themselves can cause significant blood loss, stress and reduced performance.

The larger animal-health concern is the tick’s ability to transmit Theileria orientalis Ikeda, a blood parasite that causes bovine theileriosis.

Clinical signs can include:

• Anemia and pale or yellow mucous membranes
• Weakness, lethargy and exercise intolerance
• Fever and loss of appetite
• Reduced weight gain or milk production
• Late-term abortions, stillbirths or other reproductive losses
• Collapse or death in severe cases

Young calves, pregnant animals and cattle under stress may be particularly vulnerable. Infected cattle can also remain carriers after recovering, creating the potential for the parasite to move with apparently healthy animals.

There is currently no treatment shown to reliably eliminate T. orientalis Ikeda from infected cattle. Early veterinary care and supportive treatment can help affected animals recover, but cattle that recover can remain carriers for life. This makes prevention, tick control and careful management of infected or potentially exposed animals especially important.

Modelling has also identified parts of Canada that may offer suitable habitat for the tick, including portions of Atlantic Canada, southern Ontario, southern British Columbia and potentially parts of the southern Prairies.

Anaplasmosis is already present in Canada

While the Asian longhorned tick draws attention as an emerging threat, bovine anaplasmosis is already known to occur sporadically in Canada.

Anaplasmosis is caused by Anaplasma marginale, a micro-organism that infects and destroys red blood cells. It is most often transmitted by ticks, but infected blood can also be transferred by biting flies or contaminated needles, dehorning equipment, tattoo tools and other instruments.

The disease can cause fever, severe anemia, weakness and respiratory distress. Its effects are strongly associated with age. Calves under six months of age rarely become seriously ill, while clinical disease can be severe in mature cattle. The Canadian Food Inspection Agency reports mortality ranging from 29 to 49 per cent among clinically affected cattle over two years of age.

Animals that recover remain infected for life and can serve as a source of infection for ticks, flies or equipment that later contact susceptible cattle.

Alberta lists anaplasmosis as a provincially notifiable disease. Producers and veterinarians should include it when investigating unexplained anemia, weakness, production loss or sudden death.

Theileriosis and anaplasmosis can look similar in the field. Laboratory testing is therefore important, particularly where cattle have travelled, new animals have entered the herd or ticks have been observed.

Ticks can affect cattle even without transmitting disease

Canada has three main tick species known to infest cattle: the American dog tick, Rocky Mountain wood tick and moose, or winter, tick.

Ticks can cause irritation, alter grazing behaviour and contribute to reduced performance. Heavy burdens can lead to blood loss and stress. Some populations of Rocky Mountain wood ticks can also cause tick paralysis in cattle in parts of British Columbia.

The distribution and activity of ticks are influenced by temperature, moisture, habitat, wildlife movement and animal movement. A changing climate is contributing to the expansion of some tick ranges and can lengthen the periods when ticks are active. That does not mean every tick carries a pathogen, but it increases the value of routine surveillance and accurate identification.

What producers can do

The same basic practices help reduce risk from both established and emerging tick threats:

• Inspect cattle regularly. Include tick checks when animals are being handled, particularly during warmer months and after grazing in brushy or wooded areas. Pay close attention around the ears, neck, brisket, udder, groin and under the tail.
• Check incoming animals. Isolate and inspect newly purchased or returning cattle before mixing them with the herd. Ask where they have been and whether they may have come from a tick- or disease-affected area.
• Avoid blood transfer between animals. Change needles between animals and clean and disinfect tattooing, dehorning, castration and other equipment that may carry blood.
• Know the warning signs. Contact a veterinarian promptly if cattle show unexplained anemia, pale or yellow mucous membranes, weakness, respiratory distress, fever, weight loss, reproductive losses or sudden death.
• Preserve unusual ticks for identification. Remove the tick carefully, place it in a sealed container or bag, and contact a veterinarian or animal-health authority for guidance. Photographs can help, but laboratory identification may be required because many tick species look similar.
• Use control products strategically. Work with a veterinarian to select products approved for the target pest and production class. Follow label directions and monitor whether the treatment worked. Broad environmental insecticide application is generally not recommended because of potential effects on non-target species and the environment.
• Manage habitat where practical. Reducing excessive brush and tall vegetation around high-use areas may help limit tick habitat. Management should be based on the tick species and local conditions rather than a one-size-fits-all approach.

If anaplasmosis or another provincially reportable or notifiable disease is suspected, producers should contact their veterinarian promptly. In Alberta, suspected or confirmed cases must be reported to the Office of the Chief Provincial Veterinarian within 24 hours.

Vigilance without alarm

The first Canadian detection of T. orientalis Ikeda did not signal that bovine theileriosis or the Asian longhorned tick had become established in Canada. It did, however, narrow the distance between a foreign threat and Canadian cattle.

For Alberta producers, anaplasmosis and the direct effects of ticks remain the more immediate concerns. But the practical response is much the same across all these risks: inspect animals, strengthen biosecurity, avoid transferring blood between cattle, investigate unusual clinical signs and submit unfamiliar ticks for identification.

As the range of ticks and tick-borne pathogens changes, early recognition will remain one of the cattle industry’s most effective lines of defence.