Farm Disinfection

Salmonella, Rhodococcus equi, strangles, rotavirus, and multiple other contagious disease outbreaks...these are the bane of horse owners, farm managers, and trainers. One strangles outbreak can wreck a show season, cause cancellations of breedings, sales, and racing dates, and tarnish the reputation of a farm. The horror stories are numerous, and we have to keep an important fact in mind--no vaccine for any disease of humans or animals is 100% effective. For some pathogens, such as R. equi (which causes pneumonia in foals) and Salmonella, no commercial vaccines are available, period. Preventive medicine rests not only on properly timed vaccinations, detailed farm management, deworming, and adequate nutrition, but also on disinfection.

Disinfecting stalls, aisleways, horse trailers, and equipment isn't fun, but it is a necessary part of reducing the risk of disease entering your farm and causing outbreaks. If nothing else, the outbreak of foot and mouth disease (FMD) in Great Britain and other countries has emphasized the necessity for thorough disinfection in controlling disease. (The virus that causes FMD is a tough, very contagious bug, but does not affect horses.)

Several factors need to be taken into consideration prior to disinfection. What types of surfaces do you need to disinfect, what pathogens are of primary significance, and what chemical is going to have a reasonable expectation of efficacy under these circumstances?

No disinfectants that can kill all of the equine pathogens are safe for use in horse facilities. It is critical to understand that the more porous the surface, and the more organic matter that is present, the less likely that any disinfectant will work!

Here's an outline for disinfecting a stall with non-porous surfaces such as varnished wood, painted concrete block, etc. WARNING: Allow 45-60 minutes for completion of the task, and expect major sweat production!

  1. Remove all buckets, feed tubs, and bedding from the stall.
  2. Sweep the walls and floor to remove as much organic matter as possible.
  3. Using a hose with a spray nozzle, wash down all stall surfaces using a detergent or a phenolic disinfectant solution that contains a detergent. For stubborn stains, keep the surface wet for 10-20 minutes, then scrub by hand. Rinse by starting at the top of the stall, then working from the edges of the stall toward the draining area. Remaining dirty areas might need a second cleaning (pay special attention to corners and drains). All manure caked onto walls and floors needs to be washed off!
  4. After all surfaces are cleaned and rinsed, remove as much excess water as possible, especially from floors, by using a broom or rubber scraper (squeegee). Since you'll dilute the disinfectant according to label instructions, you don't want the disinfectant further diluted by spraying it on standing water.
  5. Put on protective clothing, gloves, and goggles before working with the disinfectant. Follow label instructions and dilute it into an applicator such as a garden sprayer. Spray the walls (begin at the top) and floors, and allow to dry. DO NOT rinse!
  6. If an outbreak of infectious disease is currently on your farm or nearby, repeat the spraying and drying of the disinfectant.
  7. While you are waiting for the stall to dry, scrub all buckets, feed tubs, and other feeding equipment with a detergent, then rinse. Spray on the diluted disinfectant, allow it to stand for 10 minutes, then thoroughly rinse it with potable (drinkable) water. Anything that the horse will eat from needs to be completely rinsed of disinfectant! Dry these containers and return them to the disinfected stall.
  8. 8) All equipment such as pitchforks, shovels, and grooming tools should be cleaned, rinsed, then soaked in disinfectant solution for 10 minutes, followed by a final rinse. Any disinfectant will be tough on the leather handles of brushes, so these should be protected by taping plastic wrap or foil around the leather straps.
  9. 9) Towels, clothing, and other machine-washable materials should be rinsed of gross filth, soaked for 10 minutes in disinfectant solution, then washed.

It is impossible to adequately disinfect porous floors such as packed clay, sand, dirt, or other materials. Bedding should be completely removed, and wet areas should be limed and allowed to dry. In humid areas, fans may be needed for drying. This will eliminate some organisms that are highly susceptible to drying, such as Leptospira, but not many other major equine pathogens. Thickly bedding the stalls will place some distance between any pathogens in the soil and the horse.

Disinfection Challenges

The interaction of surface, pathogen, and disinfectant was studied by Susan Ewart, DVM, PhD, Dipl. ACVIM, and others from Michigan State University, and reported in the April 1, 2001, issue of the Journal of the American Veterinary Medical Association. Different surfaces (wood, stainless steel, galvanized steel, plastic, and others) were cleaned, contaminated with a culture of Salmonella in broth, then disinfected with different chemicals to determine their germicidal effects. The study pointed out the complex interactions between surfaces, Salmonella, and disinfectant, and concluded that bleach was effective on most surfaces. However, bleach is readily inactivated in the presence of any organic matter--such as feces or pus--which is where Salmonella would likely reside in the farm environment.

This study points out the multiplicity of factors that go into killing only one pathogen. Imagine the complexity of adding in other bacteria and viruses that infect horses! There are few easy answers, and research is ongoing on many fronts.

From personal experience with farm outbreaks of disease, as well as communication with several university clinicians who have dealt with outbreaks in clinics, the cleaning step is the most important when disinfecting any surface. If the organic matter isn't removed, or as with porous surfaces can't be sufficiently removed, disinfection might not kill the viruses and bacteria. The hardest step thus is also the most critical. Some bacteria can produce an outer film that protects them and helps them adhere to a surface. One example of a "biofilm" is plaque on your teeth. Just rinsing with an antiseptic (a "disinfectant" for skin and mucous membranes) won't sufficiently remove and kill oral bacteria. This is why brushing and flossing (scrubbing the surfaces with a cleanser) are so important. Biofilms are receiving much more attention by researchers, as antibiotic resistance (resistance of pathogens to commonly used antibiotics) is knocking at the doors of both human and veterinary medicine.

Phenolic disinfectants are used in Kentucky international quarantine stalls, and are commonly used on farms and equine hospitals. Phenols are not as readily inactivated in the presence of organic matter as is bleach, and they will kill rotavirus, a pathogen of significant importance on breeding farms. Further in-depth discussions about disinfectants and farm management techniques to contain infectious disease outbreaks can be found in "Disinfecting Stables" in the November 1999 issue of The Horse.

Staying alert for poor hygiene and regularly disinfecting your farm properly will help you avoid costly disease outbreaks.


Do Not Mix Chemicals

While on one farm, I asked the farm manager what was in the spray bottle next to the tack room sink labeled "Hand Rinse." He replied that it was a mixture of three different commercial disinfectants. "I figured if one didn't work on people's hands, one of the others would," he said. The three chemicals were labeled for use on surfaces, not human skin.

Mixing different chemicals is like playing with fire. Toxic gases can be produced causing respiratory failure, severe and/or permanent skin damage, and the list goes on. (Plus, attorneys would have a field day with civil liability for causing physical harm to your employees.)

A thorough scrub with liquid soap and warm water (if available), followed by drying with disposable paper towels, is adequate for skin cleansing. Besides, if you are working with highly contaminated bedding or materials, you should be using disposable gloves.

As far as disinfectants for stalls, foot baths, etc., never mix chemicals unless specifically told to do so by a professional who knows disinfectants. You might be instructed to clean a surface with one disinfectant, rinse, then apply another disinfectant, which is different than pouring two chemicals in your sprayer and spraying the walls with a potentially deadly mixture! Always read and follow label instructions. This is for your safety as well as that of the employees for whom you are responsible.


Rats! Mice!

According to poultry research, even the best and most thorough disinfecting program can be ruined by a barn mouse. As few as 20 Salmonella bacteria can multiply in a mouse's intestines to more than 200,000 per dropping! Those mice found in the feed sacks and munching uneaten grain in feed tubs can be a serious threat to the health of your horse!

Referring to the NAHMS Equine '98 Report, greater than 94% of operations used rodent control, which primarily consisted of cats. Carefully examine your barn for evidence of mice (usually mouse droppings), and take action. Not all cats are natural "mousers." Have a professional exterminator evaluate your barn facilities if necessary, and always store grain in solid rodent-proof containers.--Roberta Dwyer, DVM, MS, Dipl. ACVPM


FURTHER READING

Linton, A.H.; Hugo, W.B.; Russell, A.D. Disinfection in Veterinary and Farm Animal Practice. London: Blackwell Scientific Publications, 1987.

About the Author

Roberta Dwyer, DVM, MS, Dipl. ACVPM

Roberta Dwyer, DVM, MS, Dipl. ACVPM, is a professor within the University of Kentucky's Maxwell H. Gluck Equine Research Center and editor of Equine Disease Quarterly.

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