What does rhinopneumonia describe in horses?

Rhinopneumonia in horses refers specifically to a viral respiratory disease caused by equine herpesvirus types 1 and 4. This condition is characterized by severe nasal discharge and inflammation of the upper respiratory tract, along with associated symptoms such as fever, coughing, and lethargy. The presence of significant nasal discharge indicates that the horse's respiratory system is actively fighting off the virus, which is a hallmark of the infection.

The other options do not accurately describe rhinopneumonia. For instance, while a chronic cough may be a symptom associated with respiratory illnesses, it does not encompass the full picture of rhinopneumonia's clinical manifestations. Weight loss and dietary changes pertain to metabolic or gastrointestinal issues, and a digestive disorder would also be unrelated since rhinopneumonia primarily affects respiratory health rather than digestive function. Therefore, the selection that indicates severe nasal discharge related to an upper respiratory infection accurately captures the essence of rhinopneumonia in horses.