Stabled horses are exposed to numerous respiratory and GI pathogens, including viruses, bacteria, mold spores, dust mites, and parasites. Stable environments affect disease transmission in terms of air quality and ventilation, population density, and general cleanliness. Barns should be constructed to optimize ventilation and light, minimize exposure to dust and molds, provide temperature regulation, facilitate cleaning and disinfection, and provide ample space for each horse. Windows and skylights provide sunlight and natural ventilation. Sunlight is a potent killer of many bacteria and viruses; it also promotes coat shedding and regular estrous cycles. Eight air changes per hour is considered adequate ventilation for temperate climates and average humidity. (Also see Ventilation.) Ceiling or wall-mounted fans can be used to increase air circulation on hot, humid days. Stall doors open at the top or made of heavy mesh screening provide better ventilation. Stalls should have nonslip flooring and walls or partitions that prevent direct contact between horses in adjacent stalls. Suggested stall dimensions for adult horses and for mares with foals are 3.6 × 3.6 m and 5 × 5 m, respectively. Doorways should be at least 2.4 m high × 1.2 m wide.
Recurrent airway obstruction(chronic obstructive pulmonary disease [see Recurrent Airway Obstruction in Horses]), and noninfectious inflammatory airway disease are associated with airway hypersensitivity to environmental allergens and irritants and exposure to organic dust. The most commonly incriminated allergens are fungal spores and pollens, but barn dust is also rich in dust from shavings, sawdust, manure, hay, animal hair and dander, silica from dirt in indoor arenas, and endotoxin. The amount of air contaminants increases with the dustiness of the barn, bedding, and forage. Management techniques that help prevent this condition include substituting wood chips, peat moss, or shredded paper for dusty straw bedding; avoiding dusty concentrates; using shallow rather than deep feed containers; and soaking hay before feeding at ground level. Air quality can be improved further if bedding and feed are not stored above the stalls. Riding areas and the dust they generate should be situated away from stalls to reduce exposure to dust.
Feeds should be stored in dry containers to reduce contamination with molds and animal excreta. Moldy hay and silage feeding have been associated with cases of equine botulism. Opossum feces can transmit infective sporocysts of Sarcocystis neurona, the causative agent of equine protozoal myeloencephalitis (see Equine Protozoal Myeloencephalitis). Contamination of feeds by deer urine has been incriminated in the spread of certain strains of Leptospira (see Leptospirosis).
Regular disinfection of stables and feed and water buckets helps reduce persistence of infectious agents in the environment. Organic debris inactivates most chemical disinfectants; therefore, disinfection should begin with physical cleaning (ie, hosing, scrubbing) of all surfaces followed by chemical disinfection. Phenols, quaternary ammonium compounds, and chlorine are the most commonly used disinfectants. (Also see Antiseptics and Disinfectants.)
To further reduce spread of infectious disease, stalls should have walls or partitions to prevent direct contact between horses in adjacent stalls. Pregnant mares, mares with foals, and weanlings should be kept separate from yearlings and adult horses. Ideally, new arrivals should be isolated from the resident horse population for 30 days to reduce introduction of contagious respiratory diseases, including respiratory viruses (eg, equine influenza virus and equine herpesviruses 1 and 4) and bacterial infections (eg, Streptococcus equi). Alcohol-based hand sanitizer gels are very effective against most infectious respiratory viruses and bacteria. Wall-mounted hand gel dispensers can be placed strategically throughout barns and tack rooms to improve hand hygiene and to reduce transfer of infectious diseases.