Horse falls seriously ill after eating caterpillars
Jul 13 2012
Dr. Nick Shaw treats Hanoverian mare Brandy by draining fluids from the sac surrounding the horse's heart. Caterpillars are posing a significant health threat, Shaw says.Photograph by: Bruce Stotesbury , timescolonist.com (July 2012)
A Central Saanich veterinarian is investigating what could be Western Canada's first case of a horse falling seriously ill after eating tent caterpillars. The insects have infested the mare's Saltspring Island farm.
Ten-year-old Hanoverian mare Brandy is undergoing intensive treatment at a Central Saanich animal hospital - having had 21 litres of fluid drained from her pericardium, a sac surrounding the heart, on Tuesday.
Veterinarians strongly suspect the animal is suffering from a syndrome linked to the ingestion of tent caterpillars, a syndrome that experts say has been reported in the Eastern United States, but not, to their knowledge, near the West Coast.
Veterinarian Nick Shaw called it a "very significant health threat."
He hasn't seen a case like this on Vancouver Island or the Gulf Islands, but his investigation is in its early stages.
"We're still looking into this, because it's a syndrome that's been reported in the Eastern States, especially Kentucky," said Shaw. "But everything seems to fit."
Mare reproductive-loss syndrome affects reproductivity and causes late-term miscarriages, as well as pericardium infections.
A particularly bad outbreak in 2001 affected several hundred mares in Kentucky and surrounding states - causing a loss of about $300 million to the equine industry, according to the American Association of Equine Practitioners.
Two mares from Brandy's southern Saltspring Island farm, which was "overrun with caterpillars," suffered miscarriages in the past month.
"The whole thing seems to fit, so we're pretty concerned about it," Shaw said.
Dan Fraser, who owns the farm with his wife Elaine, said he was aware of the syndrome and tried to keep his horses from consuming the caterpillars, but to no avail.
"We were literally inundated with caterpillars," he said. "Every fence post was crawling with a foot of them [...]. Every building had them falling off the roof."
Fraser breeds horses as a hobby and said the loss of the two foals was particularly devastating. They were the only two mares impregnated with semen ordered specially from Germany.
"We only breed every once in a while," he said. "So we had a lot riding on them. So not only has it been stressful emotionally, it's been stressful financially."
Typically, the foals would have been born before the explosion of tent caterpillars, but the Frasers bred them later in the season.
They also continue to be concerned about Brandy, who has lost weight since becoming ill. The mare remains in hospital, where a drain continues to remove fluid. Shaw said her condition is improving, but it's possible the fluid build-up will recur or the pericardium will be damaged.
"She's much better now," he said Wednesday afternoon. "She's breathing, her heart rate is normal, but we have to wait and see what happens over the next few weeks."
As a grazing animal, the horse may have eaten caterpillars that fell from trees onto the grass, he said. Bacteria carried in the caterpillars' hairs is most likely at the root of the syndrome.
Since the horse ingested western tent caterpillars, rather than the eastern tent caterpillars found in Kentucky, the case may provide new information about the syndrome.
This year marks the biggest spike in western tent caterpillar populations on Vancouver Island since 2005. However, the peak has already passed for the season, said Michelle Gorman, integrated pest-management co-ordinator for the City of Victoria Parks Division.
The reddish-brown critters, marked with red and blue dots, feed in groups on deciduous trees and their populations rise and fall in five-to 10-year cycles.
They're typically kept in check by natural predators.
For pest control, the City of Victoria recommends pruning nests in a way that won't cause structural damage to trees, as well as submerging them in soapy water or stomping on them prior to disposing of them in a compost bin.
Live caterpillars should not be placed in the garbage, as they may eat their way through the bags. email@example.com