Deadly horse virus prompts cancellation of equestrian events across N.S.

Equestrian events across Nova Scotia are being cancelled in an effort to prevent the spread of equine herpesvirus-1, after an outbreak a local veterinarian says has killed four horses.

Dr. Trevor Lawson, an equine practitioner in Nova Scotia and the president of the Canadian Veterinary Medical Association, says the four horses were all at the same barn one case was lab confirmed on Nov. 3, the other three are considered presumptive positives.

"I think any time that we see neurologic disease in horses, it's a very serious incident. Quite often it does not go well," said Lawson, during an interview at his home in Carrolls Corner, N.S.

He said half of all horses who get the disease will die.

It's also highly transmissible, spread through the air when an infected horse coughs, or by nasal secretion if horses are nose-to-nose or indirectly with water buckets or grooming equipment.

People can also spread it by coming into contact with a sick horse and then another.

The neurological strain of the virus first causes a fever and a nasal discharge, then the horse may show signs of weakness and start to stumble.

Lawson said a very high percentage of horses are carriers of the virus, but that doesn't mean they'll get sick.

"Most horses, including the ones that are here in my backyard, if we were to test them, have likely had herpesvirus from a young age," he said.

Just as humans who carry the herpesvirus tend to get cold sores when they are stressed, the immune systems of horses also get suppressed when they're stressed and that's when the disease shows up. Lawson said the stressor may be as simple as moving a horse by trailer, which is a normal activity.

WATCH | Viral outbreak in N.S. horses:

Equine herpes outbreak threatens horses in Nova Scotia

10 months ago

Duration 2:03

An outbreak of equine herpes a potentially fatal and highly transmissible virus found in horses is forcing equestrian events across Nova Scotia to be cancelled. Some are calling on the federal government to track cases to help prevent the spread.

Next 2 weeks critical

CBCNews has not confirmed the exact location of the barn where the outbreak occurred, but Lawson said it is in northern Nova Scotia.

Usually equine herpesvirus causes respiratory disease, or abortion in mares, and most horses are vaccinated against those forms. The vaccine does not work on the neurological form, but Lawson said keeping horses vaccinated will still reduce the shedding of the virus overall within the population.

He said the next two weeks will be critical, but if there are no new cases during that time, then the virus has likely been contained.He said he believes the outbreak has been contained to one barn, but it is difficult to know for sure.

Equine herpesvirus is not a federally reportable disease.

The Canadian Food Inspection Agency's website says reportable diseases "are usually of significant importance to human or animal health or to the Canadian economy."

In a statement, a spokesperson for the agency said the disease caused by equine herpes is not reportable because it poses no food safetyconcernsand cannot be transmitted to humans.

In Ontario, the provincial government has made it reportable, which means veterinarians must notify the Ontario Ministry of Agriculture if they diagnose an animal.

That is not the case in Nova Scotia, which Lawson said he believes is appropriate. He said one of the reasons Ontario does this is because the province has a significant equine industry based around racing, which involves a lot of horse movement year-round.

Horse owners say the virus should be reportable

But some Nova Scotia horse owners say they believe the virus should be reportable.

A spokesperson for the Nova Scotia Department of Agriculture says the department periodically reviews its list of notifiable diseases and equine herpesvirus will be included in an upcoming review.

"I feel that we should have been told by some higher-up," said Bruce Trenholm, who owns Creek View Farm in Northport, N.S. He found out there was equine herpes in the province by chance from a vet he called for an entirely different reason.

"I talked to a lady last night that had no idea it's even out there yet, and she's got a horse," he said.

Like many horse owners in Nova Scotia, Trenholm cancelled a clinic he planned to hold on his property last weekend in an effort to help prevent the spread.

He estimated he lost around $2,000 but said, "It's a bigger cost to start losing horses."

Nikki Porter, who helps run Rock'n Horse Ranch in Amherst, N.S., says she also thinks the disease should be reportable.

She cancelled a horse show and a clinic, which she figures cost her $5,000.

She also runs a tack shop on the same property and is asking everyone who comes to the shop to remove any clothing they've worn in their own barns. She also changes her own shoes when she leaves the barn and enters the tack shop to protect her customers' horses.

"It really is up to the equine community to just be as open and transparent and honest as possible," she said.