Five horses are already infected and a growing stream of suspected
cases of West Nile virus are being tested in Manitoba.
“There are lots of suspect cases showing up around the province,” said
Allan Preston, Manitoba Agriculture’s director of veterinary field
services.
“The number changes pretty well every hour.”
There have also been signs the disease is moving westward with one
confirmed Saskatchewan case in a dead magpie found in Regina, and two
other suspicious tests in birds in that province.
Read Also
Anti-separatist movement targets rural Alberta
Former deputy premier Thomas Lukaszuk’s anti-separatism Alberta Forever Canada petition campaign expects to run full steam ahead into the province’s farming regions
West Nile is a viral infection that can affect horses, people, dogs and
some poultry. The virus causes central nervous system disorders that in
the worst case can lead to death in horses.
Preston said Manitoba is not in an epidemic and the risk of horses
contracting the virus remains low.
He encourages people who see signs of a central nervous system disorder
in their horse to contact a veterinarian who can help determine whether
West Nile is at play rather than a more likely disease.
A horse infected with West Nile virus has reasonable odds of survival,
especially if the diagnosis is made early.
Signs of infection in horses can include stumbling, weakness in the
hind legs, an inability to stand, limb paralysis, listlessness, head
shaking, fever and death.
Preston said the symptoms can be confused with other nervous system
disorders in horses such as rabies, sleeping sickness, equine viral
rhinopneumonitis, equine protozoal myeloencephalitis and tetanus.
The West Nile virus is spread by mosquitoes. It does not spread from
horse to horse, or from horses to other animals or people.
Many equine cases of West Nile virus have been confirmed in Minnesota
and North Dakota, two American states that border Manitoba.
All ages of horses are susceptible, particularly the very young and
very old, or those already ill from another disease.
Preston said the fatality rate among infected horses ranges from 35 to
40 percent. Early diagnosis and supportive therapy may improve the
chance of survival. The supports can include fluid therapy,
non-steroidal anti-inflammatory drugs, antibiotics and diuretics.
A conditional use vaccine is available for West Nile virus in horses.
It is available from veterinarians.
The vaccine is given in two doses, with an interval of three to four
weeks between the first and second dose. Protective immunity develops
two to four weeks after the second vaccination.
That means it would likely be several weeks after the first vaccination
before the horse would have immunity.
The Canadian Food Inspection Agency cautions horse breeders that
vaccinated horses may develop antibodies to West Nile virus.
Those antibodies could affect exports of the animals to countries that
require a negative blood test for the disease.
Preston advises horse owners concerned about the virus to consult with
their vet to decide whether vaccinations are warranted. Producers
should consider risk, costs, mosquito levels and time of year when
deciding whether to start a vaccination program.
Prevention can also include mosquito control, such as:
- Stabling horses at night in a barn with mosquito netting.
- Using insect sprays and repellents.
- Burning smudges in areas where permitted.
- Getting rid of sources of standing, stagnant water.
- Reducing the amount of tall vegetation around corrals and barns.
