Eosinophils play a crucial role in the inflammatory response in conjunction with both innate and adaptive immunity. Eosinophils have long been recognized as inflammatory leukocytes that are particularly important in patients with parasitic infestations. However, recent studies in veterinary medicine demonstrate a number of canine eosinophilic gastrointestinal (GI) disorders unrelated to a parasitic infestation. Although the underlying pathophysiology behind eosinophilic infiltration of the canine GI tract remains uncertain, medical intervention aiming to decrease the activation of eosinophils seems effective in reducing symptoms and preventing organ damage. This review focuses on the biology of eosinophils and their products. It describes, the composition of eosinophil granules, mechanisms of eosinophil activation, and eosinophil-related disease processes leading to organ damage. Even though the main clinical signs of canine eosinophilic gastroenteritis, vomiting and diarrhea, are similar to those of other types of gastroenteritis, the clinical response and prognosis are worse for this condition. The clinical signs and diagnostic approach for eosinophilic GI disorders are described and compared between canine and human patients for each region of GI tract, from the esophagus to the colon. Moreover, the current treatments for this syndrome in canine and human patients are summarized and paralleled. The comparative study of canine and human patients with eosinophilic gastroenteritis will advance the understanding of this syndrome in both species and may lead to the development of novel treatment strategies.
