Vaccine Guidelines – Core

horse with trainer

Basic or Core Vaccines

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 and eastern equine encephalitis.



Rabies is a well-known cause of fatal disease in many mammals. The virus is transmitted through bite wounds by infected animals. The most common wildlife species to be diagnosed with rabies in Canada include foxes, skunks, raccoons and bats.

In 2008, two horses were diagnosed with rabies in Ontario. 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.

For information on rabies in Canada go to:

For information on rabies in Ontario go to:



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.

Tetanus antitoxin (technically not a vaccine) is administered to non-immunized horses (or ones where their immune status is unknown) that sustain a wound that has become contaminated. It is prepared from the blood of healthy, hyperimmunized horses and provides immediate passive immunity lasting 7-14 days).


West Nile virus (WNV)

West Nile virus (WNV) is spread by mosquitoes and causes encephalitis in humans, horses, llamas and alpacas.

It can be fatal in non-vaccinated horses and up to 40% of survivors can have residual neurological deficits for a period of months or permanently, therefore it is important to protect horses against this virus.

The initial vaccination is followed by a booster vaccine , usually in the spring to provide protection during peak mosquito season in mid to late August in Ontario.

In 2002, 101 horses were confirmed infected with West Nile virus and many of those horses died. Since then, positive test results for WNV infection are reported to the Ontario Ministry of Agriculture, Food and Rural Affairs.

horses in pasture

Eastern equine encephalitis (EEE)

Eastern equine encephalitis (EEE) virus is spread by a mosquito (Culiseta melanura) 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 Caribbean and South and Central America. Eighty to ninety percent of infected horses develop acute and lethal neurologic disease, with survivors often having persistent neurologic signs.

EEE occurs sporadically from year to year but is thought to reoccur in the same general areas associated with its mosquito vector which breeds in hardwood swamps. The vaccines to protect against EEE are very effective. The initial vaccination is followed by a booster vaccine , usually in the spring to provide protection during peak mosquito season in mid to late August in Ontario. In endemic areas, such as southern Florida, veterinarians recommend vaccinating young horses three times a year.

In 2014, at least 22 horses lost their lives to EEE in the eastern part of the province. To find out where EEE has been reported go here:

Please note: This information provides guidelines only and should never replace information from your veterinarian.


Guidelines for Vaccination of Horses. Guelph; Dr. Bob Wright (OMAFRA) and Dr. Dan Kenney (Ontario Veterinary College), 2004

Guidelines for The Vaccination of Horses. Lexington; AAEP, 2008

The Ontario Health Network

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