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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, occurs when a sufficient quantity of an infectious agent overcomes the resistance acquired through prior natural exposure to the disease agent or through vaccination. (View AAEP Infectious Disease Control Guidelines)

Infectious disease control programs should be directed toward:

  • Reducing the exposure to infectious agents in the horses' environment
  • Minimizing factors that decrease resistance or increase susceptibility to disease
  • Enhancing resistance to those diseases by vaccination

Consistent utilization of such management programs will, in time, lower the incidence and/or severity of infectious diseases. 

Occurrence of infectious diseases in populations of horses tends to increase with:

  • Increased population density of susceptible horses at a facility.

High population density situations as found 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.

  • Movement of horses on and off the facility.

The introduction of horses from various origins, commingling of horses of different ages, and the high proportion of susceptible horses pose special problems and demonstrate some important considerations in the practice of disease control.

  • Environmental and managerial influences.

Examples of external factors that can contribute to increased risk of infectious disease include:

  • stress
  • over-crowding
  • parasitism
  • poor nutrition
  • inadequate sanitation
  • contaminated water source/supply
  • concurrent disease
  • inadequate rodent, bird and insect control
  • movement of people, vehicles, and/or equipment on and off facilities during infectious disease outbreaks.

Copies of the vaccination and health maintenance records should accompany the movement of horses. Similarly, owners of equine facilities should establish health entry prerequisites, including, but not limited to, vaccinal history. Horses should be appropriately vaccinated prior to entering or leaving such a facility in order to produce an adequate immune response before the anticipated exposure.

Strict attention should be afforded to the manufacturer’s recommendations regarding storage, handling, and routes of administration of the vaccine to maximize efficacy and safety. However, results of research or clinical experience may support alternate protocols for vaccination that mayimprove the efficacy of a vaccine without increasing adverse effects.