ABSTRACT
The relationship between air hygiene within two types of identically managed horse housing and the incidence of covert respiratory disease (as revealed by endoscopic examination) of their inhabitants was assessed. The horses were all under the supervision of the same trainer. In one yard the design ensured the boxes were well ventilated in still air conditions. In the other yard the boxes were insulated and there was little provision for natural ventilation in still air conditions. There was heavy fungal and actinomycete contamination of wood shavings in the heavily insulated, poorly ventilated housing but not in the shavings of better ventilated boxes. There was increased incidence and severity of mucopus in the tracheas of horses stabled in the contaminated environment over that seen in the other group. There was no such association between the incidence or degree of pharyngeal lymphoid hyperplasia and the two environments or between the degree of tracheal mucopus and PLH found in the 72 horses examined in this study.
