Risks to livestock increasing as ticks expand their territory

Although media reports focus on the threat of tick-borne diseases on humans, owners of cattle and farmers should be aware of the risks they pose for livestock

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Livestock producers must be alert and become more aware of new disease pressures that might affect their animals as the tick population reaches into new areas.

Why it matters: Animal diseases carried by ticks aren’t well known in Ontario yet, as they are just arriving.

Many Ontario residents are aware of Lyme disease and other dangers ticks can pose to humans, but livestock can also be placed at higher risk in areas where ticks are common.

Livestock susceptible to Anaplasmosis

Jessica Gordon, assistant professor of ruminant health management at the University of Guelph, says Lyme disease largely does not affect livestock, and cattle are particularly immune.

Lyme disease infection can be very severe when it does occur, but such cases are extremely rare. Livestock acting as a vector for the pathogen and increasing exposure risk for humans is the more serious issue.

However, livestock are susceptible to Anaplasmosis, a parasitic bacterial disease originating in the southern United States, and one also borne by northward-migrating ticks.

Ticks are found in forests and grasslands, making them likely to interact with animals raised outdoors.
photo: Ticks are found in forests and grasslands, making them likely to interact with animals raised outdoors. Photo: Scott Bauer, USDA Agricultural Research Service, Bugwood.org

According to the Canadian Food Inspection Agency, this pathogen infects red blood cells of domestic and wild ruminants, including cattle, sheep, goats, and deer. In Canada, it is primarily a disease of cattle.

Blood cells infected with Anaplasmosis are attacked and broken up by the immune system. Consequently, Gordon says the most obvious sign of infection is blood or red colouration in urine. Weight loss, anemia, increases in heart rate, poor food consumption and other issues can also manifest.

Shaun Dergousoff, an Alberta-based research scientist with Agriculture and Agri-Food Canada, says Anaplasmosis is not common in Canada, but there have been confirmed cases, including one from Elgin County as recently as August 2019.

“It is a disease that is not going to disappear and some of us are concerned that it could continue to be reintroduced and become established somewhere in Canada,” says Dergousoff.

“In the United States they are not finding any males…. Females are reproducing on their own… The only limit to their reproduction is feeding.” – Shaun Dergousoff.

Currently, Anaplasmosis is considered an “immediately notifiable disease” by CFIA. This classification refers to diseases exotic to Canada for which there are no control or eradication programs. Control measures are enacted by CFIA when the agency is notified of individual cases, though provincial ministries and producer organizations also work in tandem on the problem.

Asian longhorn tick proliferating

An emerging tick species of concern is the Asian longhorned tick. This tick originated in eastern Asia, and has established populations as close as central Pennsylvania and New York. As of Aug. 1, Public Health Ontario indicates there are no reports of Asian longhorned ticks in Canada.

The Asian longhorned tick is not able to establish itself in all environments, says Dergousoff, but it can proliferate and appear in high densities in areas where a foothold has been gained. Single farm animals within these areas can be hosts to thousands of ticks at a time, which can take enough blood to seriously affect the animal’s growth and productivity.

Two Haemaphysalis longicornis ticks, commonly known as the longhorned tick. The smaller of the two is a nymph. The larger tick is an adult female. Males are rare. The United States dime in the background gives a sense of their minute size.
photo: Courtesy Centers for Disease Control and Prevention

He says there are even cases where highly infested animals have died from blood loss.

“In the United States they are not finding any males…. Females are reproducing on their own,” says Dergousoff. “The only limit to their reproduction is feeding.”

The Asian longhorned tick is also a vector for a variety of different human and livestock-specific diseases in countries where it has been long-established such as China, Japan and Australia.

However, what diseases it hosts depends on a variety of factors, including geography; whether it acts as a vector, or just a benign carrier of a pathogen, also varies considerably.

“The concern is we are not certain if that tick can transmit pathogens in places where it’s becoming established,” Dergousoff says. “When you start to see the potential pathogen and the vector occurring at the same place it becomes a bit more than a theory.”

Adult, nymphal and larval ticks attached to the ear of sika deer.
photo: Mat Pound, USDA Agricultural Research Service, Bugwood.org

Gordon says Anaplasmosis remains largely contained to the U.S., but it is “definitely moving north.” A major factor in how quickly it establishes itself in Canada is linked to changes in weather patterns, specifically the frequency and duration of freezing conditions.

“That’s why for a long time we didn’t think we had Lyme in Ontario,” she says, adding a “survival of the fittest” factor is also at work.

“The ticks that can survive are the ones that reproduce,” Gordon says.

Dergousoff adds the chances of establishment for ticks carrying new livestock pathogens also relates to response effectiveness. On the farm, that means being aware of how animals are doing, knowing what to look for as new pressures encroach and being in close contact with a veterinarian.

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“Producers and vets are on the forefront. They’re going to be the ones to see these things first,” says Dergousoff.

“If they’re not established yet we’re still ahead of the game… that awareness is also partially making the appropriate people aware to minimize the problems that might come out of this.”

About the author

Contributor

Matt is a freelance writer based between Essex County and Chatham-Kent. He is interested in all things scientific, as well as rock n' roll, hunting and history. He also works with his parents on their sixth-generation family farm.

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