Vaccination Schedule for Horses

Key Takeaways

• Many combination vaccines are available to reduce injections while protecting horses from multiple high-risk diseases. Vaccination schedules vary by age and status (adult, broodmare, foal), with most core vaccines requiring annual boosters and initial 2-3 dose primary series.
• Core equine diseases–Tetanus, Encephalomyelitis (EEE,WEE), West Nile Virus, Rabies–carry high fatality rates, making timely vaccination essential. Risk-based vaccinations help protect against EHV (respiratory & abortion), Influenza, Potomac Horse Fever, and Strangles.
• Diseases spread through soil, insects, wildlife, or horse-to-horse contact, with symptoms ranging from mild respiratory signs to severe neurologic damage or sudden death. Vaccinationing according to AAEP guidelines help reduce these risks. 
• Safe vaccine administration relies on proper IM injection technique: using sterile needles, choosing correct injection sites (neck triangle, pectoral, hamstring), aspirating before injecting, and monitoring for soreness afterward.
• Understanding disease risks, following structured vaccine plans, and using correct injection methods ensures horses receive consistent, effective protection throughout their lives.

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Many combination vaccines are available, with protection against multiple diseases, to minimize the number of injections given.

Age	Tetanus	2-way or 3-way Sleeping Sickness	West Nile Virus	Rabies	RHINO (EHV) Respiratory	RHINO (EHV) Abortion	Influenza	Potomac Horse Fever	Strangles
Adult Horse Booster Series	annually or following injury	annually	annually	annually	annually	annually	semi-annually to annually	semi-annually to annually	semi-annually to annually
Adult Horse Primary Vaccinations	2-dose series	2-dose series	single dose or 2-dose series	single dose	3-dose series	3-dose series	1-dose, 2-dose or 3-dose series	2-dose series	2-dose or 3-dose series
Broodmare Booster Series	annually, 4-6 weeks pre-partum	annually, 4-6 weeks pre-partum	annually, 4-6 weeks pre-partum	annually, pre-partum or pre-breeding	3-dose series	3-dose series	semi-annually, with one dose given 4-6 weeks pre-partum	semi-annually, with one dose given 4-6 weeks pre-partum	semi-annually, with one dose given 4-6 weeks pre-partum
Broodmare Primary Vaccinations	2-dose series	2-dose series	Not recommended unless high risk.	single dose, pre-partum or pre-breeding	3-dose series	3-dose series	2-dose or 3-dose series	2-dose series	3-dose series
Foal	3-dose series	3-dose or 4-dose series	2-dose or 3-dose series	single dose or 2-dose series	3-dose series	3-dose seriess	2-dose or 3-dose series	2-dose series	3-dose series

Prepared using vaccination guidelines developed by the American Association of Equine Practioners Infectious Disease Committee, 2008.

Common Equine Diseases

Tetanus

Often referred to as “lockjaw”, tetanus is caused by a toxin-producing bacterium that is often found in the soil. It can enter the skin through cuts, wounds or a newborn’s umbilicus. Symptoms include muscle stiffness and rigidity, flared nostrils, prolapsed third eyelid and legs stiffly held in a sawhorse stance. As the disease progresses, muscles in the jaw and face stiffen, preventing the animal from eating or drinking. More than 80% of affected horses die.

Encephalomyelitis

More commonly known as “sleeping sickness”, this virus is transmitted to horses by mosquitoes that have acquired it from birds and rodents. Eastern (EEE) and Western (WEE) equine encephalomyelitis have been noted in the United States. Venezuelan (VEE) equine encephalomyelitis has not been seen in the U.S., however a recent outbreak occurred in Mexico. Symptoms vary, but all result from degeneration of the brain. Early signs include fever, depression and loss of appetite. As it progresses, staggering gait and paralysis may develop. Depending upon the strain, between 20 and 100% of infected horses die.

West Nile Virus

A virus transmitted by mosquitoes that have acquired it from birds or other animals. West Nile Virus infects the central nervous system, and presents with symptoms similar to Encephalomyelitis. Although it has been responsible for equine deaths, most infected horses can achieve full or partial recovery with supportive therapy.

Rabies

The rabies virus is most often transmitted through contact with the saliva of an infected animal. Rabies affects the central nervous system and leads to cerebral dysfunction, including excess salivation, abnormal behavior and aggression. Though horses are infected infrequently, it is always fatal. Rabies can be transmitted from horses to humans.

Equine Herpesvirus/Rhinopneumonitis (EHV)

Two distinct viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) cause two different diseases, both of which are known as rhinopneumonitis. Both types cause respiratory problems that may include fever, lethargy, loss of appetite, nasal discharge and coughing. EHV-1 may also cause abortion, foal death, neurological signs and paralysis. Rhinopneumonitis is spread by aerosol or direct contact with secretions, instruments or drinking water. The virus may not present any symptoms in carrier animals. Immune protection for pregnant mares requires vaccination with EHV-1 vaccine specifically labeled for abortion protection.

Influenza

One of the most common respiratory diseases in horses, influenza is highly contagious. The virus can be transmitted by aerosol transmission from horse to horse. Symptoms are similar to those in a human with a cold, including dry cough, nasal discharge, fever and loss of appetite. Horses that travel or are exposed to other horses are most at risk.

Potomac Horse Fever

An acute enterocolitis caused by ingestion of bacterial spores that may be found in pastures bordering creeks and rivers. Symptoms can include mild colic, fever, diarrhea and abortion. PHF is a seasonal problem with geographic factors.

Strangles

A highly contagious, yet rarely fatal, bacterial infection characterized by abscess of the lymphoid tissue of the upper respiratory tract. Strangles is transmitted through contact with infectious excretions and surfaces containing the resilient bacteria.

Resources: American Academy of Equine Practitioners, Bayer Animal Health, the Merck Veterinary Manual and the Centers for Disease Control and Prevention.

Equine Injection Guide

How and Where to Inject Neck Region

Most frequently used. Extreme care necessary to hit safe “triangle” of muscle – neither too high in the neck into the large ligament (ligamentum nuchae), nor too low in the neck close to the cervical vertebrae (neck bones). Avoid the jugular area.

Hindleg or Hamstring Region Easy to reach and large muscle area. Be aware horse may kick.

Chest or Pectoral Region Easy to reach. Be aware horse may strike, or possible swelling may make walking difficult.

Gluteal or Hip Region Easy to reach. Be aware that if a post-injection abscess forms here it is difficult to treat. Not a recommended area.

Step-by-Step Injection Guide

1. Use 20-22 gauge, 1.5-inch needle.
2. Use a new, sterile needle for each dose of vaccine and for each horse.
3. Keep needle sheathed until immediately before use.
4. Disinfect skin with alcohol. Tap skin a few times and thrust needle in quickly, deep into muscle, straight all the way to the hub.
5. Carefully attach syringe to inserted needle. Pull back plunger slightly to insure you are not in blood vessel. Blood will appear if you are. If so, withdraw and try again.
6. After withdrawing needle, massage site for 30 seconds after injection to distribute vaccine and help avoid soreness.
7. Allow horse to rest and get free exercise for 2 to 3 days following vaccination, during which time horse may experience slight soreness and lethargy.

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