Pituitary pars intermedia dysfunction (PPID), also known as equine Cushing's disease, is widely reported in middle-aged to older domestic equids but to date reported in only one nondomestic equid, the onager ( Equus hemionus onager). This case series reports clinical, hematological, and pathological findings consistent with PPID in two further equid species: one Chapman's zebra ( Equus quagga chapmani) and five Przewalski's horses ( Equus ferus przewalskii). The case series reports basal adrenocorticotropic hormone (ACTH) testing as a method to diagnose and monitor PPID in zoological equids and the use of pergolide mesylate to reduce basal ACTH concentration and reduce clinical signs associated with PPID. Gross and histopathological examinations of the pituitary gland in four of these cases revealed either pars intermedia adenomas or adenomatous hyperplasia, similar to pathological findings in domestic equids affected by PPID. These findings suggest that clinicians working with nondomestic equids should be aware of this condition and consider screening for it routinely, particularly given that improvements in management and veterinary care for exotic animals are resulting in a more aged captive population. Early diagnosis and treatment of PPID may prevent the development of painful clinical sequelae and therefore improve the welfare of zoo equids.
Keywords: ACTH; Chapman's zebra (Equus quagga chapmani); Cushing's; PPID; Przewalski's horse (Equus ferus przewalskii); pituitary.