Timely treatments key to tick control

The best time to treat cattle might occur after they are already out on pasture, requiring another trip through the chute

The mere mention of ticks seems to give people a case of the creepy-crawlies. The bite itself is nasty but some ticks can also transmit disease, notably Lyme disease.

“Ticks put the fear of God into people for some reason,” said Dr. Roy Lewis, an Alberta-based veterinarian.

But ticks are also an issue for cattle and large numbers of them can cause anemia and make the animals more susceptible to disease. In parts of British Columbia, ticks can cause tick paralysis which, as the name implies, paralyzes animals and can be fatal without intervention.

Lewis said there are three effective treatments for cattle to guard against ticks. Saber and Boss are pour-ons and Ectiban is mixed with water and used as a spray.

“The good news is that we’ve got some products to treat them. The bad news is you might have to treat them at a different time.”

Michael Raine photo

Depending on location and likelihood of tick load, the best time to treat cattle might occur after they are already out on pasture, which then might require another trip through the chute.

Shaun Dergousoff, a research scientist with Agriculture Canada based in Lethbridge, is studying ticks and the distribution of two types that frequent Western Canada: the Rocky Mountain wood tick and the American dog tick.

His research shows both species of the arachnid are expanding their range and those ranges are starting to overlap. In the past, Rocky Mountain wood ticks were most commonly found in parts of western Saskatchewan, Alberta and British Columbia, and the American dog tick was more common to central Saskatchewan, Manitoba and southern Ontario. The division between the species was at about 110 degrees latitude and in the 1950s and 1960s there was a gap of about 80 kilometres between them.

“What we’ve found out so far now is that the distribution of the American dog tick has changed quite a bit over the last 40 years,” said Dergousoff.

“It has now moved quite a bit further north in Manitoba and Saskatchewan and in Manitoba that could be at least 300 km north of previous reports and in Saskatchewan at least 200 km of those earlier reports. We’re also finding that it’s moving quite a bit further west.”

There are likely several reasons for that range expansion, he said. Warmer temperatures might account for some of the northern expansion but Dergousoff said that’s not the whole story.

“Definitely, the ticks themselves don’t move very far on their own. They really rely on their hosts to move them. So, these large range expansions probably have a lot to do with movement (of) all wild hosts, for example maybe coyotes or deer.”

People can also carry ticks, although they are more likely to discover them quickly and kill them. That is not necessarily true for livestock and for pets, however.

“Human activity is a big thing with movement of infested hosts, like dogs, cattle, horses,” said Dergousoff.

Adult ticks feed and then drop from their hosts, potentially far from their usual range. That doesn’t mean they will thrive in the new location but the potential is there.

In terms of cattle threats from ticks, B.C. ranchers in the Nicola Valley and Williams Lake regions have long had to battle the potential for tick paralysis by treating their cattle.

“It’s a huge problem and it’s a constant problem as long as the adult ticks are active,” said Dergousoff.

Ticks can also transmit bovine anaplasmosis. That illness is caused by blood-borne bacteria. Adult ticks take on a blood meal, drop off and then can spread that bacterium by biting another animal.

“The ticks are also special in that the bacteria will … actually grow inside the tick. The ticks are actually a host for the bacteria. That means that as long as the tick is alive, they can keep the bacteria alive and then transmit it at a later time,” Dergousoff said.

However, Lewis said he isn’t aware of any increase in anaplasmosis in cattle, though it is something to be aware of if importing cattle from southern states where the illness is more common. Infected cattle may not show symptoms but can still act as carriers.

Dergousoff said anaplasmosis is no longer a reportable disease in Canada. The Canadian Food Inspection Agency must be immediately notified if a case is found but there is no investigation, quarantine or eradication effort.

“A lot of the control is really going to be producers and their veterinarian,” he said. “One of the biggest concerns really is importation of infected animals and then the potential for transmission after that.”

It will remain tick season in Western Canada until about the middle of July, after which the ticks’ life cycle limits their quest to find hosts.

The other bit of good news for people and animals, said Dergousoff, is that most ticks don’t carry illness, however unpleasant their bites might be.

“In most places in Canada, both these species of tick rarely have these pathogens in them. Even in places where you do expect to find these pathogens, they might only be five percent of the ticks.”

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