Aug 29 2010
by: Erika Street
Although few of us would let our horses miss their yearly tetanus shots, we often overlook another important aspect of disease prevention: Disinfection. While vaccines go a long way toward averting disease, none are guaranteed to be 100% effective. More importantly, none are even available for organisms such as Salmonella, even though the infectious disease it causes can spread quickly through a herd, wreaking havoc on a horse farm.
Fortunately, regularly disinfecting barns and equipment can help keep such flare-ups at bay. While regular disinfection might seem labor-intensive and costly, you must consider the consequences of not disinfecting.
Last year’s outbreak of Salmonella newport at the University of Pennsylvania’s New Bolton Center serves as a grim example. Sixteen horses had tested positive for Salmonella either before or at their time of death, but it was unknown how many of those deaths were caused by the bacterium as many of the animals were critically ill upon admission. To control the disease’s spread, the George D. Widener Hospital for Large Animals was forced to close its doors to new patients last May and to sandblast, disinfect, and repaint the facility.
As the saying goes, an ounce of prevention is worth a pound of cure. Routine disinfection is not just good horse management–it is a necessary component of an adequate disease prevention program.
Know How Diseases are Introduced
When planning a program to prevent infectious disease on your farm, you must first consider the most common ways diseases are introduced and transmitted. “Knowledge is power,” says John Poe, DVM, MPH, veterinary medical officer with the USDA, Animal and Plant Health Inspection Service (APHIS), and former medical epidemiologist with the Kentucky Department of Public Health.
Once you understand how a particular disease is spread, you can create a targeted strategy to control the relevant factors in the environment. For example, if a particular disease common to your area is spread via insect bites, you must focus on controlling the mosquito and fly populations on your farm. On the other hand, if the disease you are concerned about can be transmitted through contact with bodily discharges or other substances in paddocks and stalls, disinfection of your facilities is an indispensable method of control.
Diseases such as strangles and salmonellosis are caused by bacteria that can survive and multiply outside living animals, particularly on moist surfaces and in the presence of organic matter. “Therefore, in addition to being spread by horse to horse contact, strangles is also frequently transmitted by fomites (objects on which pathogens can stick and infect other animals) such as contaminated twitches, lead shanks, grooms, and common watering tanks,” says Poe.
“The most common routes of spread of respiratory viruses such as influenza, equine rhinopneumonitis, and equine viral arteritis (EVA),” he continues, “are direct nose-to-nose contact, contact with nasal secretions, and aerosol transmission.”
This clearly illustrates the need for surface disinfection. Eliminating viruses and bacteria that survive in barns and stalls keeps diseases from being spread by environmental contamination.
Challenges for Disinfecting
Because of the complicated interactions between pathogens, disinfectants, and surfaces, there are many variables to consider before disinfecting your barn. The concentration of the disinfectant, the duration of its contact with the surface, the ambient temperature, the characteristics of the surface being disinfected, the presence of organic matter, and the target organism’s resistance to the disinfectant all affect how successful the process will be.
“Non-porous, smooth surfaces are the most readily cleaned and disinfected,” says Paul Morley, DVM, PhD, director of biosecurity for the Veterinary Teaching Hospital at Colorado State University. “The more organic material such as dirt or manure that is present, the less effective your disinfectants are going to be, and the more you’re going to have to use good old-fashioned soap and elbow grease.”
The fact that many disinfectants are deactivated by organic matter explains why the cleansing step of the disinfecting process is so important. According to a review by V.J. Fotheringham (see Disinfection of Livestock Production Premises in the March 1995 issue of Revue Scientifique et Technique), cleaning alone removes about 90% of bacteria, while a further 6-7% is removed by disinfection. In other words, spraying a dirty wall or floor with disinfectant won’t be very effective at killing pathogens.
Unfortunately, the design of many barns is not conducive to thorough cleaning–most stalls are lined with porous raw wood and have sand, dirt, or compact clay floors. These types of floors cannot be sufficiently cleaned and are impossible to disinfect with commercial disinfectants. While you do not have many options for improving dirt floors short of pouring asphalt, you can take steps to make porous walls easier to disinfect.
Roberta Dwyer, DVM, MS, Dipl. ACVPM, of the University of Kentucky’s Gluck Equine Research Center, suggests that after thoroughly cleaning walls you patch knots with wood filler and seal the walls with a varnish or polyurethane. The result is a smooth, waterproof surface that you can easily clean and disinfect.
Choosing a Disinfecting Solution
First, consult your veterinarian to see what pathogens are of particular concern in your area. Then when you are evaluating a disinfectant, take into account its efficacy in the presence of organic matter and hard water, its germicidal activity against your target pathogens, and its cost, as well as how safe it is to use around animals and humans.
For routine disinfection, you will want to combat a wide array of organisms and will therefore need a disinfectant with a broad spectrum of anti-microbial activity.
“On the other hand, if you’re going after a specific disease or agent,” says Morley, “you have to consider what you’re dealing with. For example, rotaviruses are non-enveloped viruses and they are only susceptible to a few kinds of disinfectants–these may not be the ones that you’re using for general disinfection.”
Commercially available disinfectants fall into ten major categories: Aldehydes, iodophors, hypochlorites (bleach), alcohols, chlorhexidine, quaternary ammonium compounds (QACs), phenols, alkalis, chlorine dioxide, and peroxygens.
Aldehydes (e.g. formaldehyde) are highly toxic compounds and are therefore not recommended for use in horse barns. The 10% iodophors, which are virucidal and bactericidal, are generally used for washing hands and cleaning equipment, not disinfecting equine facilities. Bleach, alcohols, and chlorhexidine are readily available and effective on most surfaces, but are quickly inactivated by organic matter. Because most equine pathogens are found in some type of organic matter–be it feces, urine, or nasal secretions–this renders such disinfectants useless in facilities where there is a significant amount of dirt or manure. QACs, which have a moderate activity level in the presence of organic material and a good hard water tolerance, are therefore a slightly better option for surface disinfection. These are commonly used in restaurant dining room and kitchens.
Phenolic disinfectants, however, have an even higher level of activity in organic material. Because they also kill rotavirus and Salmonella, two of the most difficult-to-control infectious diseases, phenols are generally considered the best choice for disinfecting horse barns. Their biggest drawback, however, is that they are caustic to skin, mucous membranes, and even metals. Therefore, if you decide to use a phenolic disinfectant (and when working with any chemicals) make sure to wear protective clothing and eye goggles!
Peroxymonosulfate, a peroxygen, and sodium hydroxide, an alkali, are also very effective in the presence of organic material. While sodium hydroxide is highly caustic, peroxymonosulfate has a low toxic potential when it is diluted with water (the powder form is extremely caustic)–an important characteristic if you are working in the presence of animals.
No matter what disinfecting solution you ultimately choose, make sure that it is EPA-approved and read the label instructions carefully. Do not mix chemicals under any circumstances!
Proper Cleaning and Disinfection
When preparing to disinfect your barn, allow lots of time, as there are several steps and drying time involved. Don’t plan on finishing in an hour!
The first step is to dispose of any manure, feed, and debris. Then thoroughly scrape and clean all surfaces in buildings and on equipment.
Once you have removed as much organic matter as possible, completely clean all surfaces by scrubbing them with a detergent and spray-washing them with a low-pressure hose.
After cleaning, rinse carefully from the top downward, making sure that all traces of the detergent are rinsed away. Then allow the surface to dry completely. Thorough drying ensures that the cleansing agent and water will not mix with the disinfectant and dilute it.
Once the surfaces that you plan to disinfect are clean and dry, dilute your disinfectant according to its instructions. Spray the disinfectant on all non-porous surfaces and allow it to dry. Do not rinse it off! Allowing the disinfectant to dry maximizes the contact time of the chemical with pathogens.
Do not neglect your shovels, pitchforks, or grooming equipment. This type of equipment can be soaked for 10 minutes to loosen any organic material, then scrubbed clean, sprayed with disinfectant, and allowed to dry. All buckets and feed tubs should be cleaned, sprayed with disinfectant, and rinsed with potable (drinkable) water.
While annually disinfecting your barn can help control the spread of disease, it is also important to take steps to minimize your horse’s health risks on a daily basis.
Good separation procedures are vital to preventing disease on your farm. “All horse operations that board transient populations should have two groups of horses,” recommends Poe, “the resident population that never travels off the premises and the transient population that travels to shows, exhibits, and trail rides. These two groups should be housed, handled, and grazed separately–permanently.”
Lyda Denney, DVM, New York State Horse Health Assurance Program Coordinator, recommends that when introducing a new horse to your farm, you isolate him for 30 days. “A quarantine area should be established prior to the arrival of new animals that is well-separated from the other animals on the farm,” she says. “The area should contain separate utensils, and separate clothing and footwear should be worn while inside.” Visiting or sick horses should also be kept there so they do not come in contact with or share air space with resident horses.
Even if you don’t have enough space on your farm to create this type of quarantine area, you should still keep new and sick horses separate from the rest of the herd. The Ontario Ministry of Agriculture and Food suggests that if space is at a premium, you designate a stall near an outside door as the isolation area and feed and handle the animal there last. After a horse leaves the quarantine area, make sure to thoroughly clean and disinfect the stall and any equipment that was used on him.
While such biosecurity precautions are important, the general cleanliness of your barn is paramount. Because the survival time of a microorganism outside the host body is increased by the presence of organic soiling such as manure, the most effective way to keep disease from spreading throughout your farm is by keeping it clean and disinfecting it annually.
Cleaning After Infectious Horses
If you should ever have to clean up after an infectious horse, you will need to create a targeted plan to get rid of the disease in question. “First consider talking to an expert on infectious diseases like your veterinarian,” recommends Morley. “They can provide invaluable advice.”
Disinfection, although important on a routine basis, becomes urgent when you are caring for an infectious horse. During this time, the aisles must be swept, cleaned, and disinfected on a daily basis, and the stall of any diseased animal must be disinfected as soon as the horse has recovered.
Other horses in the barn must also be considered exposed and potentially incubating the disease. “You need to think very carefully about who you will expose by moving animals after they have developed signs of disease,” warns Morley. “What you could be doing is just spreading the disease around.”
While disinfection is effective at controlling the spread of disease, it cannot eliminate infections if carrier animals are continually added to susceptible populations.
It is also important to limit movement in and out of the isolation area. Footbaths containing a phenolic disinfectant should be placed outside each stall and at the entrance and exit of the barn, and all people who enter the isolation area should wear coveralls, caps, and rubber boots.
“Perhaps one of the most important–but overlooked–precautions is hand washing,” says Morley. “Sometimes your ability to wash hands in the field is limited, so I recommend using hand-sanitizing products and washing your hands both before and after handling a sick animal.
“You also need to be concerned about the potential for zoonotic infection,” cautions Morley. “Some agents like Salmonella can infect people. Make sure that you’re avoiding hand to face contact, and that people are not smoking or eating around these animals or their environments.”
Finally, Morley recommends that you think about the type of transmission when attempting to control the spread of disease. “Is it a respiratory disease, in which case you need to think about separating the air space? Or is it oral-fecal spread like rotavirus so you need to be concerned about where their feces go and the cleaning tools?”
By understanding how the disease in question is transmitted, you will improve your ability to control its spread.
By keeping your horses’ vaccinations up-to-date, maintaining a clean facility, instituting several simple biosecurity precautions, and regularly disinfecting your barns and stalls, you will be better able to prevent and control disease on your farm.
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