Investigation of hypereosinophilia and potential treatments.

Hypereosinophilia is excessive eosinophilia and has been defined in dogs and cats as eosinophils greater than 5 x 10(9)/L (> 5000/microL). Canine breeds with a predisposition to higher eosinophil counts or certain eosinophilic diseases include the Rottweiler, German Shepard, Siberian Husky, Alaskan Malamute, and Cavalier King Charles Spaniel. Two of the more common causes of canine hypereosinophilia are pulmonary infiltrates with eosinophils (PIE) and gastrointestinal disease. The highest eosinophil counts are expected in dogs with pneumonia or PIE. The most common cause of eosinophilia in cats is flea allergy. The greatest eosinophilia occurs in cats with flea allergy, feline asthma, and eosinophilic granuloma. Innovative recent treatments for human patients with asthma have been successful in reducing eosinophil numbers but have had a confusing and disappointing lack of reducing symptoms. The role of eosinophils in many eosinophilic diseases remains a mystery.