Strangles: Control and Containment Strategies

The American Association of Equine Practitioners (AAEP) has formulated practical recommendations and biosecurity measures for disease control. These specific protocols provide guidance for containment and cleanup. Work with your veterinarian to achieve best results.

Once a horse is identified with suspect or confirmed strangles, minimize horse movement and limit mingling of exposed and nonexposed horses.

"It is a good plan to separate a sick horse in an isolation area away from all other horses," recommends Josie Traub-Dargatz, DVM, Dipl. ACVIM, professor of equine medicine at Colorado State University's veterinary school. "But it's not a good idea to move exposed horses in with yet-unexposed horses just to get them away from a sick horse."

It is particularly important to protect pregnant mares and youngsters.

She also emphasizes that a single fenceline between horses might protect horses from injuring one another, but it does little to protect against disease. Primary means of disease transmission, such as nose-to-nose contact and shared water sources, can still occur.

"An isolation area must be located a sufficient distance from highly trafficked areas," says Traub-Dargatz. Contaminated pastures should be kept free of horses for at least a month. Water tanks should be cleaned and disinfected daily.

Check rectal temperatures twice daily on those horses not yet sick, and immediately isolate those showing any indication of illness.

These biosecurity measures should remain in effect at least three to four weeks following resolution of the last case of illness on a farm. Contact regulatory agencies and others whose horses might be affected by contact with the sick horses, for example, van companies, show barns, race barns, and sale barns. Apprise owners of incoming broodmares about the situation, and communicate about the steps being taken for control and eradication, while also updating owners whose horses are confined to the farm.

When possible, assign specific personnel to handle only the sick animals. Keep the number of these caretakers to a minimum to limit transfer of infective material around the farm. Supply disposable coveralls and foot covers or rubber boots that are to be worn only when in contact with sick horses, and provide footbaths with effective disinfectant solutions for use as people leave the isolation area. Arrange for specific changing areas for putting on protective clothing. Traub-Dargatz says color-coded protective clothing helps to identify which people are in charge of specific groups of horses and ensures contact only with their assigned group. Caretakers of ill animals should not contact other animals following care of sick and contagious horses unless they employ appropriate precautions to avoid spread of the bacteria. Protective barrier materials, such as disposable boot covers and plastic aprons or coveralls, should be disposed of on-site. Any clothing contaminated by a suspect horse should be put in a plastic bag before leaving the premises and laundered to remove disease agents.

Cleansing of hands after working with ill horses or handling contaminated equipment, along with disinfection of any equipment used with ill horses, are critical strategies in reducing the chance of spreading disease agents.

During an outbreak of contagious disease, all personnel in contact with any horses (exposed, sick, or nonexposed) on the farm should adhere to diligent hygiene, such as wearing gloves and washing hands (at least a 15-30 second scrub by the clock) immediately after handling any horse. Traub-Dargatz suggests singing "Happy Birthday" twice is about the right amount of time for hand washing.

In facilities with shared supplies, it is best to use liquid soap products from a squeeze bottle--liquefied soap does not come into direct contact with human hands, unlike bar soap, which tends to be readily contaminated with bacteria. Traub-Dargatz notes that some alcohol disinfectant hand gels might be effective, provided they contain at least 61% alcohol, but these are ineffective in the presence of gross contamination, such as pus.

Do not move equipment, buckets, grooming tools, or feed between the isolation barns and the well animals. Carefully dispose of or compost bedding that has been contaminated by sick horses, and restrict access of domestic or wild animals to contaminated materials and/or sick horses.

Traub-Dargatz reminds horse owners, "Things with legs move things around!"

Although the greatest sources of strangles transmission are carrier horses, the environment also provides opportunities for infection to travel through the property. Be conscious of animals you might not normally consider disease vectors, such as dogs, cats, pet goats, pigs, and rabbits that may wander the property. Traub-Dargatz relates an example of a companion dog that travels through the entire farm on a hot day, walking through infective material, then jumping into the water tank, thereby inoculating the water with an infectious agent, such as S. equi.

Good rodent and insect control limits these critters' potential as disease vectors.

Contaminated bedding should be composted beneath a layer of plastic so flies cannot access the bedding.

Traub-Dargatz mentions, "The high expense of tractors, horse trailers, and other wheeled equipment makes it tempting to use one machine for all horses at all locations on the farm, and this opens up endless possibilities for spread of disease."

She stresses that disinfection of such equipment is imperative--inside the trailers, and on the wheels and tires of tractors, wheelbarrows, and automobiles. Clean floor mats and walls of trailers as often as possible to remove contaminated organic debris that could get onto people, shoes, equipment, tires, etc., and then disinfect. Read and follow all label directions on cleaning and disinfectant products and ensure that all personnel understand instructions for safe use.

Once strangles has been contained on a premises, cleanup becomes a vital part of further reducing numbers of sick animals, and in allowing future movement of horses on and off of the farm without concern. Cleanup is a laborious and tedious process, but success is in paying attention to the details. All stall and barn walls, floors, ceilings, ledges, corners, aisleways, and wash racks should be disinfected, as well as any other surface that is exposed to horse traffic. Also, scrub down fences and anything that might have been contaminated by respiratory secretions, using disinfecting agents known to kill the streptococcal organisms, such as phenolic products, iodophors, chlorhexidine, or glutaraldehyde disinfectants. Most important is identifying the carrier animals so they don't enable persistence of strangles on the farm.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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