Guidelines for use of vaccines in horses are intended to be a point-of-reference, or a framework, to direct specific activities of veterinarians as they employ vaccines in their respective practices. These guidelines are neither regulations nor directives for all situations and should not be interpreted as such. It is the responsibility of attending veterinarians, through an appropriate veterinarian-client-patient relationship, to utilize this information coupled with available products to determine the best professional care for their patients. It is impractical to recommend a “standard” vaccination program for all horses because each individual situation must be evaluated based on risk of disease (anticipated exposure, environmental factors, geographic factors, age, breed, use, and sex of the horse), potential for adverse reactions to a vaccine(s), anticipated efficacy of the selected product(s), and cost. Cost should include expenses incurred due to time out of competition, labor and medication if or when horses develop clinical disease and need treatment, as well as expenses of time, labor and vaccine(s) to properly immunize the horses.
Programs for the control of infectious diseases are important components of good managerial practices directed toward maximizing the health, productivity, and performance of horses. Infectious disease in an individual horse or outbreaks of infection within a group of horses occur when sufficient quantity of an infectious agent overcomes the resistance acquired through prior natural exposure to the disease or through vaccination. Thus, programs for the control of infectious diseases should be directed toward:
- reducing the exposure to infectious agents in the horses’ environment (i.e., challenge),
- minimizing factors that diminish resistance, and
- enhancing resistance to those diseases by vaccination.
The incidence of infectious diseases in populations of horses tends to increase with increased number and concentration of susceptible horses at a facility, movement of horses on and off the facility, or with external environmental and managerial influences.
Conditions on breeding farms, in sales or boarding facilities, in barns of performance and show horses, or at racetracks are often ideal for introduction and transmission of infectious diseases, particularly infections of the respiratory tract. On breeding farms, introduction of horses from various origins, commingling of horses of different ages, and the high proportion of susceptible horses pose special problems and serve to demonstrate some important considerations in the practice of disease control. Managerial practices that reduce risks of exposure to infectious diseases, coupled with appropriate use of vaccines will, in time, lower the incidence or severity of infectious diseases. Different degrees of risk will result in different recommendations for vaccination. If managerial changes cannot or will not be implemented to optimize control of infectious disease, vaccination alone cannot be expected to be successful.
The client should have realistic expectations and understand that:
- vaccination serves to minimize the risk of infection but does not prevent disease in all circumstances:
- the primary series of vaccines and booster doses should be appropriately administered prior to likely exposure;
- each horse in a population is not protected to an equal degree nor for an equal duration following vaccination; and
- all horses in a herd should be appropriately vaccinated, and whenever possible, the same schedule should be followed.
This practice will simplify record keeping, minimize replication and transmission of infectious agents in the herd, and optimize herd-immunity by protecting those horses in the herd that responded poorly to vaccination. A properly administered, licensed product should not be assumed to provide absolute effective protection during any given field epidemic. Copies of the vaccination and health maintenance records should accompany horses entering or leaving sales, training, or breeding facilities. Similarly, owners of equine facilities should establish prerequisites for vaccination of all horses entering the facility and request that copies of their vaccinal records accompany those horses. Horses should be appropriately vaccinated at least one month before entering or leaving such a facility in order to produce adequate antibodies before the anticipated exposure.
Only federally licensed products should be used and strict attention should be afforded the manufacturer’s recommendations regarding storage, handling, and routes of administration of the vaccine to maximize efficacy of a vaccine without increasing adverse effects. Protection is not afforded the patient immediately after administration of a vaccine that is designed to induce active immunity. In most instances a series of multiple doses of an inactivated vaccine must be administered initially for that vaccine to induce protective active immunity. Two to three weeks are required to produce adequate concentrations of antibodies and before booster revaccinations can be protective. Foals with residual maternal antibodies generally produce a greater serologic response when an initial series of 3 doses is administered rather than the 2-dose series recommended by most manufacturers of vaccines for older horses without residual maternal antibodies.
It is important to vaccinate broodmares 4 to 6 weeks before foaling for their own protection, as well as to maximize concentration of immunoglobulins in their colostrum to be passively transferred to their foals. Simply vaccinating the mare is not sufficient. The foal must receive adequate amounts of high quality colostrum and absorb adequate amounts of specific colostral immunoglobulins before absorption of macromolecules ceases (generally 24 to 48 hours). Specific colostral immunoglobulins provide protection against field infections for several months but also may interfere with vaccinal antigens and prevent the active immunologic response by the foal; a phenomenon termed “maternal antibody interference.” Although protective concentrations of antibody decline with time, vaccination of a foal while these colostral antibodies are present – even at concentrations less than those considered to be protective – is of minimal to no value because of maternal antibody interference. Consequently, that foal may be susceptible to infection before the primary vaccinal series can be completed.
After receiving a vaccine intramuscularly, some horses experience local muscular swelling and soreness or transient, self-limiting signs including fever, anorexia, and lethargy. Severe reactions at sites of injection can be particularly troublesome requiring prolonged treatment and convalescence. These adverse reactions are not always predictable but are part of the inherent risks of vaccination. It is, therefore, recommended that horses not be vaccinated within 2 weeks of shows, performance events, sales or domestic shipment. That allowance of time should be sufficient for:
- production of antibodies to the vaccine prior to the time of major susceptibility
- recovery from unexpected adverse reactions that might otherwise interfere with the horse’s performance or health prior to, or during, shipment.
Though uncommon, the possibility always exists for adverse reactions (including anaphylaxis) associated with administration of a vaccine; therefore, vaccines should be administered by or under the direct supervision of a veterinarian. Adverse reactions should be reported to the vaccine’s manufacturer, and may also be reported to the USDA (1-800-752-6255) or the USP Veterinary Practitioners Reporting Program (Forms may be obtained or reports submitted by following the link or calling USP at 1-800-487-7776).
Vaccines are currently available in North America to aid in the prevention of the following equine infectious diseases: Tetanus; Eastern, Western, and Venezuelan Equine Encephalomyelitis; Equine Influenza; Equine Herpesvirus-1 and Equine Herpesvirus-4 infection (Rhinopneumonitis); Strangles (Streptococcus equi infection); Rabies; Equine Monocytic Ehrlichiosis (Potomac Horse Fever); Toxicoinfectious Botulism; Equine Viral Arteritis; Anthrax; Rotaviral Diarrhea. General guidelines for use of the most frequently indicated equine vaccines under various managerial conditions and in various geographic locations are provided in this report.
VACCINATION GUIDELINES – FOALS
Non-Vaccinated DAM
3 Months: 3- Way, Rabies, WNV
4 Months: 3-Way, WNV
5 Months: 3-Way, Rhino, WNV
6 Months: Influenza/Rhino
7 Months: Influenza/Rhino
8 Months: Influenza I/N
12 Months: Rabies
Strangles Injection: 6th, 7th, 8th and 12th month, then every 6 months (may want to use I/N 11th or 12th month).
Strangles I/N: 11th & 12th month, then every 6 months (start at 6th months for endemic areas).
3-Way: (E/W Encephalomyelitis, Tetanus Toxoid).
Rhinopneumonitis: (EHV-4 The form of this virus that causes respiratory disease).
Equine Herpes Virus:
- EHV-1: The form of this virus that primarily causes abortion.
- EHV-1: Certain strains can cause neurological disease.
De/Worming: Start at 2 months and de-worm every 30 days until 8 months of age. Then continue to de-worm every 60 days. Use Ivermectin, Strongid or Panacur.
Vaccinated DAM
6 Months: 3-Way, Rabies, Rhino, WNV
7 Months: 3-Way, Rabies, Rhino, WNV
8-9 Months: 4-Way, Rhino, WNV
10 Months: Influenza/Rhino
11-12 Months: Rabies, Influenza I/N
Strangles Injection: 6th, 7th, 8th and 12th month, then every 6 months (may want to use I/N 11th or 12th month).
Strangles I/N: 11th & 12th month, then every 6 months (start at 6th months for endemic areas).
3-Way: (E/W Encephalomyelitis, Tetanus Toxoid).
4-Way: (E/W Encephalomyelitis, Influenza, Tetanus Toxoid).
Rhinopneumonitis: (EHV-4 The form of this virus that causes respiratory disease).
Equine Herpes Virus:
- EHV-1: The form of this virus that primarily causes abortion. Start at 4 months if in high-risk area.
- EHV-1: Certain strains can cause neurological disease.
De-Worming: Start at 2 months and de-worm every 30 days until 8 months of age. Then continue to de-worm every 60 days. Use Ivermectin, Strongid or Panacur.
THIS IS A SUGGESTED VACCINATION SCHEDULE ONLY. THE VETERINARIAN MAY CHANGE THIS SCHEDULE BASED ON
INDIVIDUAL NEEDS, FARM/RANCH MANAGEMENT, OR CURRENT DISEASE OUTBREAK.