EquiPlanner Vaccination Guidelines

The basic or core vaccines are those vaccines that provide protection against the diseases that have significant health risk to the horse and/or to humans through contact. These are the “no-brainers.”

All horses should be vaccinated with these vaccines. They include rabies, tetanus and West Nile virus.

It could be easily argued that Eastern equine encephalitis should be added to this list, based on the occurrence of eleven cases of this disease in the mosquito season of 2003.

Rabies is a well-known cause of fatal disease in many mammals. The virus is transmitted through bite wounds by affected animals such as foxes, skunks, racoons and bats, though other mammals may transmit the virus.

In 2001, five cases of rabies in horses were diagnosed in Ontario. In 2002, one case of rabies in a horse occurred.

Rabies is a rapidly progressive disease that is preventable by vaccination. Rabies vaccines are licensed for use annually in horses and must be administered by a licensed veterinarian.

Tetanus or lockjaw is an often fatal disease caused by the anaerobic bacteria (grows in low oxygen conditions), Clostridium tetani. The spores of Cl. tetani are commonly present in the soil and can contaminate puncture wounds, crushing wounds, open lacerations, surgical incisions and the umbilici of foals.

Upon gaining entrance to the body, Cl. tetani produces a powerful neurotoxin, which blocks neurotransmission, resulting in unopposed muscle contraction and spasm (tetany).

All adult horses should initially be vaccinated for tetanus twice, three to six weeks apart, using tetanus toxoid and boostered annually or as recommended by their veterinarian.

It is present in mosquito pools and birds in every county of the province of Ontario. In 2002, 108 confirmed or probable cases of WNv in horses were reported. In 2003, only ten equine cases were diagnosed.

Since WNv is a fatal disease in 30% of horses showing neurological signs and up to 40% of survivors can have residual neurological deficits for a period of months to permanent disability, it is important to protect horses against this virus.

Depending on which vaccine is utilized, one or two vaccinations are required for primary immunization with a yearly booster recommended.

In high exposure areas, depending on which vaccine is chosen, some veterinarians recommend booster vaccinations every 4-6 months during the mosquito season. One modified live vaccines only requires a yearly booster to provide 12 months of protection. Three pharmaceutical companies now manufacture a WNv vaccine.

Eastern equine encephalitis (EEE) virus is spread by a mosquito that normally feeds on birds. People, horses, pigs and birds may become infected during periods of high mosquito populations.

The EEE virus has a range from southeastern Canada to the southeastern United States as well as the Carribean and South and Central America. Eighty to ninety percent of infected horses develop acute and lethal neurologic disease, with survivors often having persistant neurologic signs.

From 1938 to 2002, there were five outbreaks of EEE diagnosed in Ontario. During 2003, eleven equine cases were diagnosed in five locations.

EEE occurs sporadically from year to year but is thought to reoccur in the same general areas associated with its mosquito vector. There are vaccines available to prevent EEE.

Horses in eastern Ontario and the Muskoka-Bracebridge area would be at a higher risk based on the previous history of this disease in Ontario. (Check on the incidence rate in your province).