Producers urged to watch for pigeon fever, West Nile Virus

RED DEER — Horse owners must watch for flare-ups of pigeon fever and West Nile Virus this summer.

Dr. Kelsey Brandon, a veterinarian from Claresholm, Alta., who first diagnosed pigeon fever when it arrived in southern Alberta last August, said the first case was thought to be an accident in which a horse had been kicked.

The owner reported the horse was severely lame and had a sudden swelling in its chest.

“I thought I was going out to a trauma case,” she told the Alberta Horse Breeders Conference held in Red Deer Jan. 10-12.

She said horse owners should contact a veterinarian if disease is suspected and let the practitioner lance any abscesses because some go deep into the body.

“It is best to seek some advice.”

There is no vaccine.

The last case of pigeon fever was seen Jan. 10. It appeared in 20 horses and two miniature donkeys.

The disease causes painful swelling in the chest and may turn into an abscess that must mature before it can be lanced and drained.

It may also appear internally and affect the lungs, spleen and liver or infect the legs’ lymphatic system.

Pigeon fever is caused by corynebacterium pseudotuberculosis, a soil borne bacterium, and is spread by biting insects such as horse, house or stable flies. It may incubate for several weeks before swelling occurs, but then quickly spreads.

It can also affect cattle and sheep. Cattle can pick it up from sheep and horses but not the other way around. People are not affected.

Antibiotics are not recommended because then abscesses take longer to mature and draining is delayed. The drugs also have difficulty entering the infection.

Antibiotics may be recommended for internal abscesses and lymphangitis. Internal infections may require a six to eight week course of antibiotics and regular monitoring.

Infected horses should be handled with biosecurity measures, such as handling sick animals last and using separate equipment. If possible, isolate infected horses, wash hands and use disposable gloves.

When applying fly treatments, remember to spray under the belly because flies seem to bite there.

Producers are also being warned to stay alert for West Nile Virus, which may reappear this year after a hiatus, said Dr. Larry Friske, a veterinarian with the animal health company Zoetis.

“It is one of these diseases that never goes away. It is an endemic disease,” he said.

The mosquito culex tarsalis, which thrives in hot weather, bites infected birds and then transfers the virus to horses and humans.

West Nile has not been a serious problem for some years, so most birds have not been exposed.

The first case appeared in New York in 1999, and the virus spread across the continent in 2002.

The worst year was 2003, when Alberta had 170 confirmed cases in horses, Saskatchewan had 162 cases and Manitoba reported 47 cases. There were nearly 400 cases across the country that year.

It was followed by years of low incidences, but the virus reappeared in Saskatchewan and Alberta in 2012 and 2013. The incidence seems related to environmental conditions.

Effective vaccines are available.

Friske said horses should be vaccinated for West Nile as well as forms of sleeping sickness and other horse diseases.

West Nile requires two shots for immunity. Pregnant mares can receive a shot six weeks before foaling.

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