BUSINESS OF PRACTICE: STRENGTHENING THE FOUNDATION OF YOUR PRACTICE


primary healthy horse circulation paths. Place the containment dumpster downwind of all facilities. Plan traffic flow so that the containment dumpster is the last to be picked up with the trash service.


4. Aerosol Transmission


Aerosolized particles can be inhaled, deposited on mu- cus membranes or contaminate surfaces. Pathogens transmitted via this route include influenza or equine herpesvirus-1.2 Methods for management of these diseases include physical isolation and careful air sys- tem design. Note that diseases that spread via aero- solized particles also spread via other means such as fomite transmission, and so all previously discussed practices apply.


Isolation Barns


Infectious disease can spread via fomites or aero- sol over long distances. For example, equine in- fluenza virus spreads effectively as an aerosol over distances up to 50 yards.10 Isolation facilities for horses should be placed at a distance from other buildings on the site. While recommendations vary, a minimum of 60 feet is a useful guideline to minimize spreading of infectious diseases. Con- trolling the spread of diseases via aerosols within the isolation building requires several steps, in- cluding the following:


● Providing a solid barrier between patients and between patients and the human access areas. Windows are acceptable for looking into stalls but maintain a solid front on the stalls.


● Providing direct exhaust for each equine isola- tion stall. This ensures separated ventilation and negative pressure. The largest hospitals go to great lengths to ensure that ventilation systems are highly cleanable so they may be regularly purged of reservoirs of microbes.


● Differentially pressurize the isolation stalls, which should be negative, to the surrounding spaces, which should act as buffers, to prevent air from isolated patients from flooding into the surrounding areas.


● Consider properly designed air treatment sys- tems within the isolation facility. These sys- tems are not intended to replace proper air handling and exhaust systems, but to treat air that is in the surrounding partial-recirculated zones, such as nursing stations. The most ef- fective systems utilize a combination of filtra- tion and ultraviolet (UV) light and can be effective in eliminating 90% or more of aero- solized viruses and bacteria in laboratory conditions.a


Methods for Ventilating Hospitals Outside of the Isolation Zone


Equine hospitals tend to be less rigorously condi- tioned and ventilated than their small-animal hos- pital counterparts. Some ideas, however, should


always be implemented to reduce the risk of aerosol transmission and for basic healthy indoor air:


● Surgery rooms should be positively pressur- ized and highly filtered. MERV 13 filters pro- vide 80% to 90% filtration, which contains and controls droplet nuclei. If using a filter like this, ensure the engineer who is designing the HVAC system is accounting for the pressure drop across the filter. HEPA filters are un- necessary for most hospitals, except ones with very heavy orthopedic caseloads.


● Ventilate conditioned medical areas at least to 8 to10 air changes per hour and 40% to 60% outside air. Medical barns can be vented at four to six air changes per hour and may not need to condition the air except in very hot or cold weather.


● Control and reduce humidity. Humidity has a tremendous impact on the growth of micro- organisms in the built environment. Humid- ity should not exceed 60%, which is the level past which American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) deems the growth of molds on sur- faces to be inevitable.9


5. Cleaning and Disinfection


Cleaning is defined as the removal of visible soil (e.g., organic and inorganic material) from objects and surfaces. Normally it is accomplished man- ually or mechanically using water with detergents or enzymatic products. Thorough cleaning is es- sential before disinfection because inorganic and organic materials that remain on the surfaces inter- fere with the effectiveness of these processes.11 Cleaning is a very important step that assures the removal of organic and inorganic materials from surfaces and devices, hence allowing for maximal disinfection efficacy.11 The microbicidal efficacy of disinfectants is inversely proportional to the degree of soiling on the targeted surface.12 It has been shown that experimentally, cleaning can eliminate approximately 90% of bacteria on concrete surfaces, hence the importance of physically removing patho- gens from surfaces prior to disinfection.13 Disinfection describes a process that eliminates


many or all pathogenic microorganisms, except spores, on inanimate objects.11 Objects and sur- faces are normally disinfected with liquid chemi- cals.11 There are several factors that affect the efficacy of disinfectants such as prior cleaning, or- ganic and inorganic load, type and level of microbial contamination, concentration and contact time of the disinfectant, physical nature of the object, pres- ence of biofilm, and temperature and pH of the dis- infection process.11 It is well established that environmental contam-


ination leads to hospital-associated infections. Therefore, implementing a well-designed disinfec- tion protocol reduces the risk of acquiring pathogens


AAEP PROCEEDINGS  Vol. 66  2020 191


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