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Biosecurity Is Best Defense Against Spread of Infectious Diseases

On Behalf of the Equine Research Coordination Group

Biosecurity is the outcome from implementing protocols to reduce the chances of introducing an infectious disease onto a farm by people, animals and equipment or vehicles, either accidentally or intentionally. A variety of approaches can help ensure the biosecurity of an equine facility and its horses. A plan should include the awareness of current and emerging diseases (and risks specific to a geographic area); the potential routes of exposure to disease agents; and the means by which they can be transmitted. A program that incorporates principles of biosecurity will reduce the risk of infectious disease and their associated costs enhance the well-being of horses and improve profitability.

Transmission of infectious diseases involves the transfer of disease-causing microorganisms from one location to another, particularly from an external environment to a susceptible animal. Exposure to disease-causing agents can occur in many ways, including:
•    Exposure to contaminated drinking water and/or feed;
•    Exposure to rodent or bird droppings;
•    Aerosols (infectious agents spread through the air);
•    Direct contact with other animals;
•    Fomites (inanimate objects), including contaminated equipment;
•    Contact with insect vectors (carriers of disease);
•    Breeding;
•    Contact with contaminated vehicle surfaces;
•    Human foot traffic; and
•    Contact with contaminated hands and clothing.

People who manage horses at a facility should know the health and nutritional status of each animal; maintain accurate and detailed health records; and have a vaccination protocol based on a veterinarian’s recommendations. Preventative measures that are low cost and easy to implement include written visitor policies, protocols for cleaning, and a plan of action if a horse develops an infectious disease.

Reducing exposure
The two major components of an infection control program are the reduction of the risk of exposure to disease agents and the optimization of resistance if exposure occurs. Enhancing horses’ resistance to infectious disease can begin by providing good nutrition, including supplementation of any needed micronutrients based on feed analysis; by providing housing and transport that has optimal air quality; and by reducing stressors where possible. Enhancing resistance to specific pathogens is often accomplished through vaccination. A vaccination plan can be optimized when it is tailored to the individual horse and herd by a veterinarian, who will consider the risk of exposure; the cost, effectiveness and safety of the vaccine; and the disease risk aversion level of the horse owner.

The most efficient method in which contagious infectious diseases are spread is direct horse-to-horse contact. Therefore, verifying the health status and vaccination requirements of horses that are newly introduced to the herd and isolating new arrivals can reduce the risk they pose. Creating an isolation area allows newly arriving or sick animals to be separated from the resident population for a designated period of time.

An additional precaution is to keep horses in small groups that are separated by disease risk status (susceptibility if exposed and likelihood for exposure). From the standpoint of controlling a contagious disease, horses ideally would be kept in a closed herd their entire lives. However, interaction with other horses often is necessary because of competitive events or breeding purposes. Thus, options to reduce risk include turning out horses in separate, dedicated turn-out facilities; keeping horses in established groups with a small number of horses that do not mix with each other; or keeping horses separate for at least a period equal to the average disease incubation periods before the animals join the resident population.

Protocols for visitors
Pathogens (any disease-producing agent or microorganism) can be transferred from one facility to another through the movement of people or equipment. They can be carried on clothing, footwear and hands and on equipment such as grooming utensils or tack. Protocols at an equine facility should be designed to assure clean hands, footwear, clothing and equipment for visitors to reduce the risk of introducing a disease agent. A sign to indicate that visitors should check in at an entry point to the facility should be used. Also a way to determine each person’s exposure to outside horses as well as having an associated hygiene protocol based on risk is recommended. Recording the movement of horses and people can assist in an investigation of a disease outbreak.

Disinfecting surfaces

The design of the equine facility also is important to biosecurity. Non-porous smooth surfaces are the easiest to clean and disinfect. Unfortunately, most stalls and barns are not conducive to thorough cleaning, as the walls are often made of porous materials such as wood or concrete block, and floors are often sand, dirt or compact clay. These types of surfaces cannot be sufficiently cleaned if contaminated with disease-causing agents such as Salmonella, and are impossible to thoroughly disinfect with commercial disinfectants because the action of most disinfectants is reduced by organic material that is not removed by prior thorough cleaning.

Roberta M. Dwyer, DVM, MS, of the University of Kentucky’s Gluck Equine Research Center suggests an option for improving an existing horse stall is to thoroughly clean walls, patch knots with wood filler, and seal walls with a varnish or polyurethane. The result is a smooth, waterproof surface that can be cleaned and disinfected easily.

When choosing a cleaning/disinfecting solution, consult an equine veterinarian to determine when application is indicated. The veterinarian should be able to provide guidance in the effectiveness of various disinfectants depending on the surface to be treated; the likelihood a product will be corrosive to surfaces; the pathogens of concern; and the precautions necessary in using various disinfectants.

More research and funding are needed to determine the effectiveness of various biosecurity protocols in specific situations. Research also would explore the most effective cleaning and disinfection methods, taking into consideration the pathogens of concern; the cost of the product; the time required and timing for application; the effectiveness on the surfaces; and the environmental impact of application. It would be beneficial to continue the study of such questions, in the hope of providing a clearer set of instructions for equine facilities to follow as they work to enhance biosecurity.
About the Author: By Alanna Kirby MS, Freshman Professional Veterinary Medical Student at Colorado State University, and Josie Traub-Dargatz DVM, MS, DACVIM, Professor of Equine Medicine at the Animal Population Health Institute at Colorado State University.