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Sanitation: Whats really important and has the biggest impact (Proceedings)
In the world of human health, prevention of hospital-acquired disease is the subject of scores of articles, journals, and textbooks.
In the world of human health, prevention of hospital-acquired disease is the subject of scores of articles, journals, and textbooks. Just a quick search on the subject of hand sanitation alone located a listing of over 650 articles. The challenge of preventing disease transmission in a veterinary or shelter setting is potentially even greater. Unlike most people, our patients roll around on floors and surfaces and subsequently lick themselves all over, effectively coating themselves with and ingesting a myriad of environmental and salivary pathogens. Caring for animals is a full-contact sport: we cradle animals against our bodies for restraint, for transportation and out of affection. Whatever is on their fur is readily transferred to our hands, arms and clothing, and if we're not careful, from there to the remainder of the animals we care for that day.
Even in veterinary clinics where many animals have a history of vaccination and good care, disease transmission is a concern. In recent years we've seen the emergence of significant infectious illnesses against which neither vaccination nor overall good health is protective, and we never know when yet another new disease will hit. This poignant email was posted on the Veterinary Information Network in May of 1998:
Every veterinary hospital owners nightmare: I will be composing a summary of now 12 cases, in the last 14 days, of a series of cats with only one common thread....they were in my facility at the time of or within 1 week of getting ill…My own cat that was visiting (boarding) died within 48 hours. But this is not your typical URI cat. This is a killer. First 8 cats....7 deaths.
In retrospect, this was diagnosed as one of the first known outbreaks of vaccine resistant virulent systemic feline calicivirus, a condition that attacks and kills even healthy, well vaccinated adult cats. Canine influenza is another example of a disease that does not discriminate by age, health or vaccine status. Both diseases have swept through veterinary clinics, causing widespread morbidity amongst patients, tremendous expense, and the heartbreak of having to tell clients their pet has died of disease acquired through a veterinary visit. Severe disease has been transmitted when a patient was brought in for something as simple as a weight check. Less dramatic (so far) but still troubling diseases with high potential for transmission include potentially zoonotic conditions such as Salmonella, ringworm, and Giardia.
The challenge of disease control in most shelters is even greater than that faced by veterinary clinics. Many animals enter shelters in poor health, malnourished, stressed and with no history of vaccination. Some animals will already be shedding various harmful pathogens, with or without showing any signs of disease. With all this disease around and so many opportunities for transmission, one might think that ubiquitous disease spread is nearly inevitable. However, there is reason for hope. Even if infection control is less than perfect, we can support animals' own immune response through attentive vaccination practices, stress reduction, wholesome food and clean water and other measures to support well-being. And a well thought out, comprehensive plan for sanitation can reduce the dose of exposure to one the animals' immune response can handle in many cases.
Thinking through a plan
Clearly, the last thing we want is for animals that come to us for care and a safe haven to acquire illness while in our facility. A well-crafted plan is needed to guard against such disasters. Consider everything that goes into the decision to choose a particular antibiotic regimen for a patient: the antibiotic has to be effective against the suspected pathogen; it must be administered by the correct route; it must penetrate to the location of the infection; it must be given with adequate frequency for a sufficient time period; and measures are sometimes taken to verify cure. There is no “one size fits all” antibiotic choice. Similarly, when choosing a disinfectant, we must consider the spectrum of effect; constraints against efficacy (such as presence of organic matter); method of delivery; time to effect; and periodic verification that the disinfection program is working as intended. Cleaning and disinfecting agents must be safe, cost effective, and practical given constraints in staff training or facility design. We need to consider numerous objects and areas that require sanitation: hands, surfaces, cages, clothing, and the role of other animals all must be addressed.
So, what products should be used?
There is no single answer to this question. Just as a single antibiotic is insufficient for all circumstances, no single sanitizing product is appropriate for every situation. Factors to consider include cleaning (detergent) versus disinfecting activity; the spectrum of effect for disinfection; activity in the face of organic matter; speed of action; method of application; cost and safety. As with choosing an antibiotic, scientific research should be consulted as well as claims of manufacturers or venders.
Un-enveloped viruses are among the most common and challenging small animal pathogens requiring our attention. These include the notorious parvoviruses (canine and feline), as well as feline calicivirus and canine adenovirus. These viruses provide an interesting illustration of the perils of choosing a disinfectant based solely on label claims.
Back in 1980, researchers at Cornell noticed that feline calicivirus seemed to spread in their research facility in spite of using a disinfectant labeled effective against that virus. This triggered a research study testing the efficacy of quaternary ammonium and other commonly used disinfectants against enveloped (e.g. canine distemper, feline herpes) and un-enveloped viruses (e.g. canine parvovirus, feline panleukopenia, feline calicivirus)1. Disappointingly enough, the quaternary ammonium compounds - labeled effective against un-enveloped viruses - utterly failed to inactivate feline panleukopenia and only partially inactivated the troublesome calicivirus. The authors concluded that “A 0.175% sodium hypochlorite solution was the most effective and practical broad- spectrum virucidal product used alone or in combination with other disinfectants/detergents”. Good old household bleach diluted at ½ cup per gallon outperformed the others in this study.
Over the years, subsequent studies continued to disprove label claims of quaternary ammonium compounds against un-enveloped viruses, in 19952, more recently in 20023, and again in 20094. It may be that a quaternary ammonium disinfectant will eventually be independently proven reliable against the un-enveloped viruses, but until then it is probably wise to at least follow these products with another, independently documented product when these viruses are about.
Even the mighty bleach is not without its flaws. It has no cleaning properties what-so-ever and is significantly inactivated by organic matter. Application of bleach to a contaminated surface is unlikely to have the desired effect. Although stable when stored in light proof containers for at least 30 days5, heat and exposure to light can substantially compromise the disinfectant properties of bleach solutions. Bleach-related compounds, such as calcium hypochlorite (e.g. Wysiwash®) and Sodium dichloroisocyanurate(e.g. Bruclean®), are frequently used in shelters and have the same limitations.
More recently additional disinfectants have become available that share bleach's reliability against un-enveloped virus, with reportedly better cleaning activity, better activity in the face of organic matter contamination, and more rapid action. These include potassium peroxymonosulfate3 (e.g. Trifectant®, Virkon®) and accelerated hydrogen peroxide6 (Accel®).
Each veterinary clinic should have a small arsenal of disinfectants on hand for various eventualities. Ringworm is a particular challenge to eradicate through disinfection. As for the un-enveloped viruses, product label claims have not always been supported by independent studies. For instance, potassium peroxymonosulfate is labeled effective against ringworm, but in one study it was only 87% effective (translating to 9/70 contaminated hairbrushes still containing viable spores after treatment)7. Another study found that of the commonly used disinfectants, only bleach at 1:10, applied twice at an interval of 24 hours, was reliably effective8. Given the importance of ringworm as a zoonotic and infectious agent in shelters, the backbone of decontamination must be thorough mechanical cleaning followed by verification via environmental culture9.
A time for everything
Most of us are familiar with the general idea that disinfectants require ten minutes of contact time for best effect. In fact, it's not quite as simple as that. Some disinfectants, such as accelerated hydrogen peroxide and potassium peroxymonosulfate, will be substantially effective in as little as a minute or less under ideal conditions6, while factors such as low temperature and organic matter contamination will increase the amount of time needed for any disinfectant. Ten minutes contact time at room temperature on a clean surface remains a good general rule, but it's not a bad idea to leave disinfectant in contact for up to an hour or more when organic contamination cannot be removed or at very low temperatures (e.g. cleaning outdoor runs in the winter time).
The timing of application is also important: disinfectant will work best when applied to a freshly contaminated surface. For instance, disinfectant applied to an exam table immediately after use is likely to work better than disinfectant applied just prior to the next use when what-ever has been sneezed, smeared or otherwise left on the table has had time to dry.
Finally, consider the “expiration date”, the time the disinfectant will lose its efficacy after mixing. Some disinfectants have quite a long shelf life, while others need to be remixed as often as once a week. Check with the manufacturer regarding recommended shelf life and make sure disinfectants are discarded properly if the shelf life is passed; not only can they become ineffective, some can become quite noxious.
Getting the "drug" to the bugs
Put a disinfectant that's inactivated by organic matter in a bucket with a mop or rag, mix in some dirt and feces, and you've got a recipe for disaster. The method of application is just as important as choice of disinfectant. When at all possible, avoid mops and buckets. For small cleaning jobs, bottles with “squirt tops” rather than spray tops are ideal to decrease the amount of disinfect aerosolized into the environment (this is important to protect animal and human respiratory health). Opaque containers should be used for bleach. All bottles should be labeled with the identity of the disinfectant; all required safety information; and the date and initials of the person who made up the solution.
For larger cleaning jobs, hose-end foamers, specially designed or built-in dispensing systems are preferred. Some disinfectants, such as calcium hypochlorite (e.g. Wysiwash®) and Sodium dichloroisocyanurate (e.g. Bruclean®) come with specially designed dispensing equipment. For large facilities, built in central systems are ideal. Disinfectants that come in liquid concentrate, such as quaternary ammonium compounds or accelerated hydrogen peroxide, are ideal for this use. For in-between jobs or where use of a hose is impractical, a hand-held or back-pack style pesticide applicator can be used. If buckets MUST be used, contamination of the disinfectant can be minimized by rinsing the mop or other applicator in a clear water bucket between each application of disinfectant. Two sided buckets are available from janitorial supply houses, or you can simply use two buckets. Separate cleaning supplies should be used for each area to be cleaned.
Whatever disinfectant and method of application is used, one key decontamination step – the importance of which is often underestimated - is drying the environment. Most pathogens prefer a moist environment, and if they happen to have slipped past your chemical disinfectant and mechanical removal, they will happily persist for hours or days in a damp corner. Fatal bacterial pathogens have been cultured from pools of water lingering in kennels that had been completely cleaned and disinfected, and even from the disinfectant dispensing system itself in one shelter outbreak. Attention to drying is especially important when the surface to be cleaned is uneven or in humid climates where air drying may not occur.
Quick note on hands, feet and clothing
Cleaning contaminated environmental surfaces is less than half the battle. Even if we put an animal onto a perfectly clean exam table, if the hands that hold the animal are dirty, the animal will soon take in whatever was on those hands. Hands also make their way into human mouths (and noses). So, keeping hands clean is important for protection of human as well as animal health. There are basically three methods for managing hands: gloves; washing with soap and water; and hand sanitizers.
Gloves are the most fool-proof choice for preventing germ transfer on hands, provided they are actually changed before and after every animal. Although gloves can be a nuisance, time consuming and relatively costly, there are times when it's clearly worth the effort. A change of gloves between every animal is indicated when handling animals that may be infected with particularly environmentally resistant germs; when a zoonotic infection is suspected; or during any outbreak of unknown disease. Always wash hands after removing gloves
It was believed that hand washing was the next best choice when gloves are impractical. However, current research suggests that hand sanitizers are preferable in many circumstances10. It is true that proper hand washing has the significant advantage of removing even the most resistant pathogens, and is therefore required under certain circumstances (e.g. when hands are contaminated with feces, blood or bodily fluids; are visibly soiled; or after suspected exposure to a durable pathogen such as parvovirus or ringworm). But it's surprisingly hard to wash hands correctly, and compliance may not be all one could wish for. Ineffective hand washing may actually be less helpful than correct use of a good hand sanitizer11. As with environmental decontamination, the drying step is especially important. Moisture on hands may actually facilitate pathogen survival and transfer12. Clients and staff should have ready access to hand washing stations stocked with soap and paper towels at all times13.
The third strategy for dealing with contaminated hands are those convenient hand sanitizer gels. Even though the spectrum of effect may be limited, a slightly less effective method, used consistently and correctly, will provide better results than the theoretically-ideal choice. In one study that compared the bacterial levels on vet students' hands after performing an exam on a horse, bacterial counts were actually lower on the hands of those who used a hand sanitizer compared to those who washed and dried11. The best hand sanitizers for veterinary use should contain 60-80% ethanol or isopropyl alcohol. Hand sanitizers should also contain an emollient to protect skin.
In human health care, feet are not generally a route of disease transmission. Our patients – especially dogs – often sit on the floor of the waiting or exam room. Luckily, if the basic environmental cleaning program is effective, the risk of transmitting disease via footwear is probably not all that high. While it's true that some pathogens may get tracked into a room when staff enters to clean it, if the last step is application of a good disinfectant, whatever was tracked in will be inactivated. If staff change footwear after cleaning and wear separate footwear for isolation areas, this risk will be further reduced. Foot sanitation should be a greater concern under a few special circumstances: before entering areas where vulnerable animals (puppies and kittens) are housed on the ground; when entering and exiting isolation areas where animals are being treated for conditions caused by particularly durable pathogens (such as parvo or ringworm); and during an outbreak of unknown cause.
Dedicated boots/shoe covers are best for reducing disease transmission by feet. The disadvantage of foot baths, however, is a big one: they just don't tend to work very well. All disinfectants require some amount of contact time for optimal effect, and this will not be achieved with a quick dip in a foot bath. Often disinfectant foot baths are not of sufficient depth or used in such a way as to remove gross organic matter contamination of shoes, further compromising efficacy.
So now we've dealt with hands and feet, leaving us only with that troublesome expanse of clothing in between. This risk of disease transmission on clothing is enhanced by our patient's propensity to shed hair onto our clothing - hair that is potentially coated with everything from the animal's saliva and environment.
One of the most important - and reasonably easy – infectious disease control procedures is to have staff change clothing or wear protective garments for “dirty” activities such as cleaning and treatment of sick animals. Although it is obviously not practical to indulge in a full change of outfit with every animal, spare scrub tops or protective smocks should be freely available and used whenever interacting with a potentially infectious or high risk animal. Discarded surgery gowns are ideal for this purpose, as the long sleeves provide full covering for arms which can otherwise escape both hand-washing and gloves.
Finally, we come to the matter of laundry. Good news here: the vast majority of the time, all that's required is washing in either a regular or commercial washing machine with hot water and bleach, and drying on heat cycle. No more bleach than the usual amount for a given size of washing machine is needed (half a cup for an average household washer). Although myths persist about bleach being inactivated by laundry detergent or hot water, this is not the case. As long ago as 1938, high temperature laundering with bleach was found to be an effective method of sanitizing hospital linens, and subsequently it was found that bleach used with water temperatures as low as 48 degrees C (118 degrees F) was sufficient14,15. An additional measure of safety is provided by the heat and desiccation of drying; hanging laundry to dry not ideal, especially if not in an area exposed to direct sunlight.
Putting it in writing
One of the most important and often-overlooked parts of any infection control program is to ensure training and compliance. Many times shelters have excellent procedures in theory, but in reality the practice is quite different. The process for disinfectant dilution and application should be clearly written out, posted, periodically reviewed, and every step observed. Measurements should be clearly marked on containers as well as posted. Staff should be signed off after training, periodically re-evaluated, and all members of the veterinary team should be encouraged to reward good disinfection control behavior when they see it as well as report any problems.
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Eleraky NZ, Potgieter LN, Kennedy MA. Virucidal efficacy of four new disinfectants. J Am Anim Hosp Assoc 2002;38:231-234.
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