Whitecourt Veterinary Clinic

PO Box 1769

Whitecourt, AB

T7S 1P5

Telephone: 780-778-5767

WEST NILE VIRUS UPDATE

 

West Nile virus isn’t just a concern for people. Since its discovery in the Northeast United States in 1999, the mosquito-borne virus has infected over 15,000 horses across North America. Approximately one in three clinically affected horses will die from West Nile, making the virus one of the deadliest disease threats to horses today.

The West Nile virus cycles between mosquitoes and birds, each infecting the other. Migrating birds have helped spread the virus northbound and westbound to nearly every province in Canada. Horses become infected when a mosquito carrying the virus bites them.

Once a horse has been bitten, it may take 5 to 15 days for signs of West Nile infection to appear. The virus attacks the brain and spinal cord, causing stumbling, muscle weakness, convulsions, coma or death. Infected horses may stagger in circles, or press their head against their stall. These symptoms can be confused with other serious neurological diseases of horses such as rabies and equine encephalitis, making prompt diagnosis and treatment imperative.

Vaccination with West Nile - InnovatorTM remains the best way to protect horses against the West Nile virus. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) says millions of doses of West Nile vaccine have been used across North America since the USDA granted its approval in 2001. More than 800,000 doses have been safely administered to horses across Canada.

However, equine statistics indicate thousands more horses remain at risk. It takes time for vaccinated horses to build immunity against the virus. Because of that, horse owners who intend to vaccinate need to move quickly and protect their animals now. APHIS asserts horse owners should be assured that the vaccine is safe and should be used as protection against the West Nile virus. The Alberta government also urges horse owners to continue to vaccinate for West Nile.

Statistics from Health Canada show provinces that actively began vaccinating horses due to early exposures in the fall of 2002 experienced a decline in equine cases in 2003, however human exposures continued to climb. Western Provinces had the highest exposures last year as a result of the virus spreading westward to new unprotected areas.

 

CANADIAN WNV INCIDENCE COMPARISON 2002 TO 2003

Human Horse Human Horse

Province 2002 2002 2003 2003

Atlantic

0

  

0

  

2* (NS)

  

1 (NS)

Quebec

9

  

3

  

17

  

8

Ontario

351

  

107

  

87

  

41

Manitoba

0

  

236

  

141

  

53

Saskatchewan

1

  

10

  

774

  

162

Alberta

2*

  

0

  

269

  

180

British Columbia

0

  

0

  

20*

  

0

Yuk./Nun.

0

  

0

  

1*

  

0

CANADA

362

  

356

  

1314

  

445

 

* Requires additional testing before it can be considered a confirmed result West Nile Virus Health Canada Statistics

 

Previously vaccinated horses will need booster shots according to your veterinarian’s recommendation. A common practice for veterinarians, as per American Association of Equine Practitioners’ vaccination guidelines, is to provide a 4-6 month West Nile virus booster for horses travelling to or in high-risk areas.

In addition to vaccinating with West Nile - InnovatorTM, other preventative measures recommended by health experts are the removal of stagnant water where mosquitoes can easily breed, and the use of insect repellents.

For more information about horses and the West Nile virus, horse owners may contact Whitecourt Veterinary Clinic at 780-778-5767, or visit the Health Canada website at www.hc-sc.gc.ca.