Discussion

Weight loss in horses is a common, nonspecific presenting clinical sign that may indicate literally dozens of medical conditions involving most organ systems. It is also one of the most common complaints tied to cases of animal cruelty and neglect. Distinguishing between disease and neglect can be difficult, and lines can be blurred further when the two are superimposed. A thorough post mortem examination is the single best procedure to definitively diagnose disease, and is essential if cause of death is to be attributed to abuse or neglect.

In this presentation a review of the types of medical conditions commonly associated with weight loss will be presented from the perspective of the post mortem examination and recognition of pathological changes. The lesions discussed from medical cases will then be contrasted with those typically found in uncomplicated cases of neglect. We will conclude with some examples of overlap and discuss the questions that should be considered.

For example, parasitism is a common clinical condition leading to weight loss that can prove difficult to combat; horses are continuously re-infected, there are a number of views on appropriate deworming strategies and protocols, encysted cyathostomes are difficult to treat, and there is even evidence for resistance to parasiticides. Failure to treat horses for parasites can lead to heavy worm burdens that can cause significant weight loss. At some point parasite-associated weight loss moves from a medical condition to neglect. To establish at what point this may be the case, the following key questions should be addressed (Anon 2006):

- Was an action or failure of an action linked to the animal suffering?
- Is it reasonable to assume that the action or lack of action would cause suffering?
- Was the suffering necessary?
- Were the needs of the animal met: suitable environment, diet, ability to exhibit normal behaviour, protection from pain, suffering, injury and disease?

If the horse had a history of sporadic de-worming, developed significant weight loss over a period of time (weeks to months), and was found on examination to have a high faecal egg count, would this be sufficient to meet the criteria for neglect? If the horse dies and a post mortem examination reveals that the horse did have a very high worm burden, but also had undiagnosed lymphoma, would this change the case for neglect?

Post mortem examination can play an important role in clinical practice beyond clarifying neglect vs. disease. Chronic weight loss can be frustrating for owners and clinicians, and may progress to death or the need for euthanasia, leaving both parties with questions. While owners and insurance companies may simply want to know - why the horse died information gained from a post mortem can inform future diagnostic and treatment strategies for the clinician, may influence recommendations for other horses in a shared environment, and is also critical in identification of emerging and reportable diseases.

Chronic weight loss in horses can prove challenging diagnostically and may be the result of neglect, disease, or both. The nature of the information a clinician can obtain about his/her cases from a post mortem examination (diagnoses, aetiology and pathogenesis) make it one of the most valuable continuing education tools available.