Many horses with nasal discharge do not require antimicrobial treatment, according to a recent study into infectious and non-infectious respiratory disease in horses.
Knowing whether the disease is caused by infection or is an inflammatory condition resulting from environmental factors helps guide treatment and management. Infectious diseases may require additional measures to prevent spread of the disease to other animals.
In some cases, the involvement of infection may be obvious. Disease affecting more than one horse might suggest infection but could be the result of common environmental factors. Fever would be a good indication of infection, although it may be missed if transient.
Research by Dr Molly Viner and colleagues suggests that Serum Amyloid A (SAA) is a reliable marker for infectious respiratory disease.
SAA is an acute phase protein - a group of serum proteins that are produced early in the body’s response to inflammation. Very low levels are found in healthy horses, but they rise dramatically in animals with severe inflammation.
SAA is a useful marker of inflammation as it increases rapidly in the early stages of inflammation and falls rapidly once the inflammation subsides.
The researchers found that SAA values greater than 52 μg /ml correctly differentiated infectious from non-infectious respiratory disease 98% of the time.
Although horses with bacterial disease tended to have higher SAA levels than did those with viral diseases, the difference was not as distinct as that between infectious and non-infectious disease.
They conclude: “SAA is more reliably elevated with infections of the respiratory tract rather than noninfectious airway conditions. This can facilitate early detection of respiratory infections, help track disease progression, and aid practitioners in making recommendations about proper biosecurity and isolation of potentially contagious horses.”
For more details, see:
Comparison of Serum Amyloid A in horses with infectious and noninfectious respiratory diseases
Molly Viner, Melissa Mazan, Daniela Bedenice, Samantha Mapes, Nicola Pusterla.
Journal of Equine Veterinary Science (2017) 49, Pages 11–13
For a video of Dr Viner discussing her findings, go to: