In Practice 8: 49-57 (1986)
© 1986 British Veterinary Association

Differential diagnosis of nasal discharge in the horse

It is very important to determine precisely the location and cause of a nasal discharge in order to provide appropriate therapy and an accurate prognosis. The majority of clinicians in practice must depend on obtaining a reliable history and combining this with a thorough clinical evaluation. In particular it is important to consider the nature of the discharge (ie, its colour and smell and whether it contains blood or food). Consistently unilateral discharges usually originate from the nasal passages and bilateral discharges from the respiratory tract caudal to the nasal septum.

Flexible fibreoptic endoscopy provides a valuable method of examining the airway, even in the presence of profuse exudates, because the distal objective lens can be flushed clear of debris. The flexible nature of the instrument permits inspection of some of the more inaccessible regions such as the middle nasal meatus, guttural pouches and trachea.

Portable X-ray machines, particularly when combined with fast rare earth screens, are powerful enough to allow radiographic evaluation of the head and neck of most horses and even the thorax of foals. Selected laboratory tests may be valuable in certain cases but interpretation of bacteriological examination of respiratory exudates can be difficult, particularly if the only sample collected is a nasal swab. Clinicians may therefore feel justified in treating suspected bacterial infections with broad spectrum bactericidal antibiotics or penicillin (the equine respiratory tract is frequently infected by Gram-positive organisms).

The high incidence of equine respiratory diseases ensures that veterinary surgeons dealing with horses will encounter respiratory problems frequently. In most cases a logical approach to the case will result in a diagnosis or at least produce a platform for appropriate treatment and a satisfacory outcome.