Pregnant mare’s urine producers have shored up their defences in preparation to fend off west Nile virus.
“We’ve all vaccinated our horses,” said Rossburn, Man., PMU producer Fred Clement.
“Nobody should get taken by surprise this year. We’ve all had ample warning.”
That wasn’t true last summer, when west Nile virus unexpectedly showed up in Manitoba and Saskatchewan, moving across North America far faster than most experts predicted. Most Canadian media attention fell to human cases of the disease, but hundreds of horses also became sick and hundreds died.
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“I lost three darned good stallions,” said Clement, who lost three mares as well after late-August rains created excellent mosquito breeding conditions.
West Nile virus is brought into an area by migratory birds. Local mosquitoes suck blood out of infected birds and then spread the disease to other animals.
Most types of livestock are immune, but horses are susceptible. Veterinarians estimate that about 20 percent of horses can become very ill and possibly die from west Nile virus.
The horse vaccine is 94 percent effective. Clement, who has vaccinated his 32 stallions and 500 mares, said he feels confident that only a couple of his horses could still be susceptible to the disease.
Brandon veterinarian Ross McKague said he thinks that at least 50 percent of horses in Manitoba have been vaccinated for west Nile virus, and that virtually all horse owners know about the disease, which wasn’t the case last summer.
“People who vaccinated will be a lot more comfortable this summer,” said McKague.
“And if people have chosen not to vaccinate, they’ve obviously come to terms with the risk.”
McKague said a wet summer with many mosquitoes could produce lots of sick horses.
Clement said his outbreak followed heavy rains at the end of August, which produced swarms of mosquitoes.
His stallions suffered more than his mares, and he lost three of 35 males compared to three of 500 females.
Clement suspects the stallions wore themselves out in July when they were breeding the mares. Two of the stallions were four year olds in only their second year of breeding, and their ardour may have weakened their immune systems.
Clement said the young stallions came out of the pastures thin and tired, while the older stallions came out “just as fat as the mares.”
PMU producers will be watching their horses closely, but they’ll also be doing more bird watching than usual. Crows are especially susceptible to west Nile virus and dead birds can be the harbinger of the disease’s arrival.
That was the warning sign last summer, Clement said.
“Just in our yard here we found an awful pile of dead crows,” said Clement.
