Vaccination for Horses

Vaccination for Horses


Vaccination has been a hot topic in human health recently and the debate is not new to the veterinary world either.  Some horse owners are concerned that their animals will experience dangerous side effects from the vaccines or that the vaccines may carry ingredients that will make their horses sick.  While there has been some evidence that the carriers in vaccines can cause tumors at the injection site, the benefits of vaccination far outweigh the risks.  Vaccinations protect your horse from dangerous, painful and often deadly diseases.  When the horse’s body is introduced to a small amount of dead or weakened antigen, it trains the horse’s body to produce antibodies.  These antibodies are specific to various diseases so if the horse comes in contact with that type of antigen again, it is prepared to fight it off, giving your horse its best chance for optimal health.


The traditional equine vaccine that most veterinarians recommend is a “core” mixed vaccine that protects horses from Eastern / Western Equine Encephalomyelitis, Tetanus and West Nile Virus.  All horses are legally required to be vaccinated for rabies, since it is a dangerous disease that affects people as well.  Additional optional vaccines include Rhinopneumonitis, Botulism, Equine Influenza, Potomac Horse Fever and Strangles, but they are typically only recommended for horses that live in highly susceptible areas.



Eastern / Western Equine Encephalomyelitis  (EEE / WEE)

Encephalomyelitis on its own means inflammation of the brain and spinal cord.  Eastern Equine Encephalomyelitis (EEE) and Western Equine Encephalomyelitis (WEE) are viruses that are spread by mosquitos.  If your horse contracts EEE they develop an acute fever, depression, loss of appetite and stiffness in their body.  As the disease progresses over the course of a few weeks symptoms become more severe and your horse will show neurological symptoms.  WEE starts out with similarly, with fever and stiffness, but the horse is more likely to fight it off and recover.



This bacteria is commonly associate with rusty, old farm equipment and is found in the feces of infected animals.  Horses can become infected if the bacteria gets into a wound.  It is a strong neurotoxin and can be fatal to horses and humans.


West Nile Virus

West Nile Virus is a form of encephalomyelitis.  Encephalomyelitis on its own means inflammation of the brain and spinal cord.  Humans and other mammals are also susceptible to the disease when bitten by an infected mosquito.  Symptoms of West Nile Virus include fever, depression and loss of appetite.  As the disease progresses the horse will show signs of neurological problems.



Rabies is a virus that can be transmitted to any mammal, including humans.  A bite from an infected animal deposits the virus into the bloodstream.  The brain and central nervous system are the main areas affected by rabies.  Symptoms include confusion, disorientation, erratic behavior (like nocturnal animals wondering about in the daytime), headache, fever, discomfort and production of frothy drool.  While the disease can potentially lay dormant for many months, once these advanced symptoms occur the animal typically only lives for a few days.


Equine Rhinopneumonitis

This virus is a type of herpes virus and can take a long time for horses to recover.  Symptoms are similar to those of a cold.  Another strain of the virus can cause pregnancy problems for mares.



Botulism causes paralysis and can be fatal to horses of all ages.  It is contracted when a horse grazes on forage that was contaminated by the carcass of a dead animal.


Equine Influenza

Highly contagious, but not fatal, this respiratory virus has cold like symptoms.  It is airborne and passed through coughing and sneezing.  The only way to treat horses with influenza is to give them rest from work for about 10 days and let the virus run its course.


Potomac Horse Fever

This disease causes severe diarrhea and can be fatal.  It is most common on the east coast so talk to your about whether it is common in your location.



Another respiratory disease, Strangles is highly contagious.  A key symptom to look for in infected horses is an abscess under the throat that can be difficult to clear up.



Foals receive antibodies from their mother’s milk which protect them as babies.  As the foals grow and they stop nursing, these maternal antibodies will wear off.  It is important to wait until the foals are around 4-6 months old before you give their first core vaccines, otherwise the maternal antibodies will address the vaccine antigen and the foal’s immune system will not learn to develop their own antibodies.  Boosters should be given at 3-4 week intervals.  Rabies vaccines are given at 4 months.  It is a good idea to make sure young horses are set with their vaccines before the start of mosquito season.  Adult horses typically need to receive their core vaccines every spring, but rabies laws vary from state to state.  Talk to your vet about their recommendations for vaccine schedules because every vet has their own recommendations based on the prevalence of disease in your area.  In some cases, senior horses who have received vaccines their whole life may have developed a strong immune system and vaccine schedules can be backed off in their geriatric years.






Duration of the protective immune response after prime and booster vaccination of yearlings with a live modified cold-adapted viral vaccine against equine influenza.


Current trends in west Nile virus vaccine development.


Validation of an improved competitive enzyme-linked immunosorbent assay to detect equine arteritis virus antibody.


What can mathematical models bring to the control of equine influenza?


Antibody responses to natural rattlesnake envenomation and a rattlesnake toxoid vaccine in horses.


Immunogenicity and clinical protection against equine influenza by gene-based DNA vaccination of ponies.


Immunological correlates of vaccination and infection for equine herpesvirus.


A new rabies vaccine based on a recombinant orf virus (parapoxvirus) expressing the rabies virus glycoprotein.