Vaccinations – Mature Horses

Spring Vaccines

We recommend “Spring Shots” be performed mid-March to mid-April, to make sure that immunity is boosted before likely exposure to insect vectors and animal movement and activity.

Eastern/Western Equine Encephalomyelitis (“Sleeping Sickness”)

Arboviruses that cause neurologic signs due to swelling of the brain and spinal cord. The disease is nearly always fatal once clinical signs develop. Transmission of EEE/WEE is by primarily mosquitoes, and infrequently by other insects, ticks, or nasal secretion. Vaccination is nearly 100% effective in preventing the disease. The virus is considered endemic in New Jersey.

Vaccination: every six months in our area of New Jersey, after an initial series (in unvaccinated horses) of two inoculations spaced two to four weeks apart.


Rabies is an infrequently encountered neurologic disease in horses, but can occur in any mammal. While the incidence of rabies in horses is low, the disease is invariably fatal and has considerable public health significance. Exposure generally occurs through the bite of an infected (rabid) animal, typically from a wildlife source such as raccoon, fox, skunk, or bat.

Vaccination is recommended once yearly.


All horses are at risk of development of tetanus, an often fatal disease caused by a potent neurotoxin elaborated by the anaerobic, spore-forming bacterium, Clostridium tetani. Vaccination of horses against tetanus is particularly important as they was much more sensitive to the toxin than humans and other mammals.

Vaccination is recommended once yearly.

West Nile Virus

The virus is transmitted from avian (bird) reservoir hosts by mosquitoes (and infrequently by other bloodsucking insects) to horses, humans and a number of other mammals. West Nile virus is transmitted by many different mosquito species and this varies geographically. The virus is considered endemic in New Jersey. The vaccine is very effective.

Vaccination: every six months in our area of New Jersey, after an initial series (in unvaccinated horses) of two inoculations spaced two to four weeks apart.

Equine Herpesvirus (Rhinopneumonitis) / Influenza

Equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) infect the respiratory tract, the clinical outcome of which can vary in severity from sub-clinical to severe respiratory disease. There is also a neurologic form of Equine Herpes Virus 4. which is often fatal. There is no vaccine for the neurologic form of EHV.

Equine influenza, caused by the orthomyxovirus equine influenza A type 2 H3N8 subtype, is one of the most common infectious diseases of the respiratory tract of horses. Outbreaks remain sporadic however.

Vaccination is recommended every three to six months, depending on the level of movement of the individual horse. In unvaccinated horses, an initial series of two inoculations spaced two to four weeks apart is recommended.


Botulism occurs in adult horses from the ingestion of potent neurotoxins produced by the soil-borne, spore-forming bacterium of the anaerobic Clostridium spp. Botulinum neurotoxin is the most potent biological toxin known and acts by blocking transmission of impulses from nerves to muscles, resulting in muscle weakness progressing to paralysis, inability to swallow, and frequently, death, due to paralysis of the muscles of breathing. It is seen in the Mid-Atlantic States and vaccination is very effective in preventing the syndrome.

Vaccination is recommended once yearly, after an initial series, in unvaccinated horses, of three inoculations spaced three to four weeks apart.

Potomac Horse Fever

Potomac Horse Fever is caused by Neorickettsia risticii (formerly Ehrlichia risticii). The disease is transmitted by insects with an aquatic (water source) lifecycle, particularly Mayflies and Caddisflies. The vaccine reduces the severity of the disease markedly, but may not completely prevent a horse from getting sick.

Vaccination is recommended at least every sixth months, after an initial series, in unvaccinated horses, of two inoculations, two to three weeks apart. In high risk areas, vaccination is recommended every three months.

Fall Vaccines

We recommend that “Fall Shots” be administered from mid-August to mid-September to provide immunity through the warm, wet Fall.

  • Eastern / Western / Venezuelan Equine Encephalomyelitis
  • Tetanus
  • West Nile Virus
  • Equine Herpesvirus (Rhinopneumonitis) / Influenza
  • Potomac Horse Fever

Optional Vaccines


Equine leptospirosis (Leptospira inerrogans) has been found worldwide, with serovar prevalence varying by region. The leptospiral-associated equine clinical disease presentations include uveitis, placentitis, abortion and acute renal failure. Infection is acquired through exposure to the organism via the mucous membranes or abraded skin. The leptospiral organisms are shed in the urine and body fluids of infected animals (including wildlife hosts). Leptospira spp. and can contaminate water and soil

We generally vaccinate for Leptospirosis in selected, high-risk situations only.

Vaccination is recommended yearly, after an initial series, in unvaccinated horses, of two inoculations three to four weeks apart.


Streptococcus equi subspecies equi (S. equi var. equi) is the bacterium which causes the highly contagious disease Strangles (also known as “Equine distemper”). Strangles is characterized by thick mucoid nasal discharge and swollen lymph nodes around the throat which sometimes will abscess and open and drain. A horse that contracts Strangles generally develops life-long immunity. The disease is most prevalent in young horses as they are most susceptible. In our practice area, because the majority of horses are mature, vaccination is not part of our regular program. Vaccination is recommended in young horses bound for sales, auction or horse shows and in the face of an outbreak. There are two vaccines on the market; a killed vaccine product for intramuscular injection and a modified live bacterial vaccine for intranasal administration. There is a fairly high incidence of injection site complications with the intramuscular vaccine and we do not favor it. We typically recommend the modified live, intranasal vaccine, when appropriate.

Vaccination is a yearly booster after two initial inoculations, two to three weeks apart.