Fistulous withers and eosinophilia in a horse

Fistulous withers is a chronic inflammatory disease of horses in the supraspinous bursa and associated tissues. The referred horse had a fistulous tract in the withers area with presence of purulent material accumulation under the ligamentum nuchae. The radiographic examination of the lesion showed an osteomyelitis involved area. The hematological examination revealed eosinophilia. Long-term antibiotic therapy reduced the eosinophilic reaction to normal. It was assumed that osteomyelitis was the cause of eosinophilia in this horse.