In horses, signs of cancer can be vague and nonspecific, such as weight loss or failure to gain weight, exercise intolerance, fever, and apathy. | Photo: iStock

By Lucia Unger, DrMedVet, Dipl. ECEIM, of the Swiss Institute of Equine Medicine (ISME); and Vince Gerber, DVM, PhD, Dipl. ACVIM, ECEIM, FVH, of ISME, WEVA treasurer and junior vice-president

Aside from skin tumors, cancer is a rare diagnosis in horses compared to humans and small animals. However, the true prevalence of many types of cancers in horses might be underestimated, because definite antemortem (in the live horse) diagnosis is challenging and often requires referral to a clinic.

In horses, signs of cancer can be vague and nonspecific, such as weight loss or failure to gain weight, exercise intolerance, fever, and apathy. Veterinarians should suspect neoplasia (tumors) in cases where they’re ruled out common differential diagnoses, such as severe parasite burden, dental or digestive problems, or infection, or in horses that do not respond to common therapeutic measures