Multisystemic eosinophilic epitheliotrophic disease (MEED) is a rare, chronic wasting disease of horses characterized by development of granulomas (nodules or masses) in numerous organs. These granulomas are composed of large numbers of inflammatory cells, especially eosinophils (a type of white blood cell that responds to allergic and parasitic stimuli).

Although the cause and pathogenesis are unknown, possibilities include an exaggerated Type 2 hypersensitivity response involving helper T-lymphocytes and a hypersensitivity response to nematode parasites. MEED has also been reported in cases with concurrent lymphoma.

Affected horses rarely present with acute disease and veterinary attention is not usually sought until chronic signs are apparent, which can take several months. Younger horses are predominantly affected and there is no sex or breed predisposition or specific geographic incidence, with sporadic cases reported from the United States, United Kingdom, Canada, and Australia.

Presenting signs vary according to the body systems involved, with the skin and gastrointestinal tract most commonly affected. Dull demeanor, inappetance, severe weight loss, diarrhea, and dermatitis are frequently reported. Skin lesions start with dry, scaly cracks and inflammation at the coronary bands and oral mucosa, then develop into widespread crusting and exudation over the face, limbs, and ventral abdomen. Lesions may initially be pruritic (itchy) and progress to hair loss and thickening and cracking of the skin. Rarely, respiratory signs, nasal and ocular discharge, swollen submandibular lymph nodes, chronic cough, and respiratory distress can predominate