Know your ticks: Asian longhorned tick (Haemaphysalis longicornis)

The Asian longhorned tick (Haemaphysalis longicornis) is not native to Canada but it has started to cause concerns in this country.

Once confined to Australia, China, Japan, Korea, New Zealand, Russia and several Pacific islands, Asian longhorned ticks were detected for the first time in the wilds of New Jersey in 2017 after occasionally turning up on imported animals at American seaports. Thanks to some entomological detective work, we now know that Asian longhorned ticks have been making their home in New Jersey since as far back as 2013. And they’re spreading fast. Between 2013 and 2023, breeding populations went from non-existent to spanning at least 19 US states.

So far no Asian longhorned ticks have been detected in Canada but Quebec, Ontario, and Manitoba are all considered prime candidates for Asian longhorned tick establishment due to several factors, geographic location and favourable environmental conditions among them.

There are a few reasons why Asian longhorned ticks are a concern. First, they’re an important transmitter of vector-borne diseases. Asian studies have linked them to anaplasma, babesia, borrelia, ehrlichia, rickettsia, and Powassan virus, all of which occur in Canada. They're also potential transmitters of Heartland virus, which is currently restricted to the US.

No disease causing pathogens have yet been found in Asian longhorned ticks collected in the US and recent studies suggest that although their larvae can become infected by Lyme bacteria, it's unlikely this species is a competent transmitter of the bacteria. Research is still ongoing on how well Asian longhorned ticks can transmit other tick-borne organisms.

Another cause for concern is information that suggests Asian longhorned ticks can trigger the same red meat allergy experienced by some people bitten by lone star ticks. Also concerning is the fact that female Asian longhorned ticks can reproduce without mating, something that can cause both rapid population growth and massive infestations that can result in massive blood loss and wasting in hosts similar to what's seen in Canada’s moose populations thanks to the feeding habits of the winter tick (Dermacentor albipictus). Neither the meat allergy nor the wasting are the result of pathogens.

Veterinarians have been asked to keep an eye out for Asian longhorn ticks in the hope that an invasion can be identified before it becomes a serious health risk to humans, domestic animals or wildlife.

Diseases transmitted: Potentially anaplasma, babesia, borrelia, ehrlichia, rickettsia, Powassan virus and Heartland virus. They may also cause a red meat allergy and wasting in host mammals.

Where found: In at least 19 US states. Not yet in Canada but expected to arrive in Ontario, Quebec and Manitoba immanently.

Photo: James Gathany / U.S. Centers for Disease Control and Prevention, Public Health Image Library