Zero cases of West Nile Virus in Ont. horses

By Gary Sliworsky
OMAFRA Rep.

Following is the latest Horse News and Views which is prepared by Dr. Bob Wright, Animal Health and Welfare, OMAFRA, in cooperation with the staff and researchers of the University of Guelph.
The monthly column highlights research topics, extension resources, reminders of common poisonings, disease or production concerns and coming events and is placed on our website, http://www.omafra.gov.on.ca/english/livestock/horses/news.html.
The number of horses identified as clinically infected with West Nile virus (WNv) in Ontario during 2006 and 2007 was zero. Complacency easily sets in with owners and they begin to question whether to continue vaccinating for West Nile. A study of the West-Nile-virus outbreak of 2003 in Saskatchewan reports that non-vaccinated horses were 23 times more likely to develop clinical disease than those that were vaccinated. The efficiency of the vaccine was reported to be 96%. The study demonstrates that vaccination was associated with prevention of clinical disease. (Ref: Waldner ET, Townsend HGG. Equine Vet J. 2007; 39:498-503).
The low incidence of WNv in Ontario horses is probably associated with the high level of protection to the virus that has been achieved in Ontario’s horse population, as well as that acquired by the wildbird population. However, this virus is still present in the environment and vaccination is still highly recommended.
The 6th revised edition of Nutrient Requirements of Horses, published in
2007 by the National Research Council, is now available from www.nap.edu/, by fax (202) 334-2451, or by contacting your local bookstore and requesting ISBN 10: 0-309-10212-X or ISBN 13:
978-0-309-10212-4 hardcover. The list price is $99.95. The 341 pages provide the most up-to-date summary and recommendations on equine nutrition. A free computer program for determining the nutrient requirements of horses was developed as a companion to the book and is available at http://nrc88.nas.edu/nrh/.
For further information, contact Dr. Bob Wright (519) 846-3412 or visit our website: http://www.omafra.gov.on.ca/english/