RESUMO
Recurrent eosinophilic granuloma (EG) in two captive eastern black rhinoceros ( Diceros bicornis michaeli) was effectively managed with glucocorticoids and antihistamines. The first case was a female and the second case was a male. The animals were housed at separate institutions and initially presented with hemorrhagic oral lesions. Multifocal lesions occurred in the second case. Multiple biopsies were taken from each animal, all of which were consistent with EG. Each animal was anesthetized multiple times for surgical treatment but experienced frequent recurrence. Due to lack of response to therapy and the risks and adverse events associated with repeated anesthesia, medical treatment was initiated in both cases using a tapering dose of oral dexamethasone. The lesions dramatically improved, but would recur frequently after treatment. Hydroxyzine, an oral antihistamine, greatly reduced the incidence and severity of the lesions. Medical management with glucocorticoids and antihistamines minimized stressful anesthetic events in both cases and contributed to the successful management of this recurrent disease. The exact pathogenesis of EG in black rhinoceros remains unknown but response to antihistamines suggests an allergic etiology.