Not just for domestic horses – The horse

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If you think pituitary pars intermedia (PPID), also known as equine Cushing’s disease, is unique to our modern domestic horses and ponies, think again. Recent study results suggest that even wild equines can develop a debilitating metabolic disorder.

Plains zebras, Przewalski’s horses and even evening primrose are susceptible to PPID, at least in captivity, said Justine Shotton, BSc, BVSc, MSc, MRCVS, head of veterinary services and zoo veterinarian at Marwell Wildlife in Winchester. , UK.

While scientists had previously reported a case of PPID in a captive evening primrose in 2009, Shotton and his colleagues identified six other cases in two equine species in captivity. These included five Przewalski’s horses aged 7 to 29 and a 17-year-old Chapman’s zebra (a subspecies of plains zebra), living at Marwell Zoo in Hampshire, UK . All six animals had excessively high plasma levels of ACTH, the hormone responsible for the disorder, which can cause abnormal hair growth, poor body condition, and laminitis, among other problems.

Five of the six animals died or were euthanized during the study, at least two of which – and possibly three – were due to the progression of PPID, Shotton said. One was euthanized for unspecified unrelated reasons and the other, Przewalski’s 7-year-old mare, was euthanized after injury and before she showed signs of PPID. Out of curiosity and given the scope of their study, Shotton said she asked for ACTH levels on the deceased mare and found them 10 times higher than normal. Histological (microscopic) examination of its pituitary pars intermedia (the brain tissue involved in PPID abnormalities) showed changes consistent with the onset of PPID.

“I didn’t expect to find anything, but it was surprising that she also had pathological and blood changes reflecting the development of PPID,” Shotton said. “PPID is now quite often diagnosed in young horses (under 10 years of age), so it may start earlier in life than we previously thought. “

It is important to study PPID in captive wild equines in order to treat them early and thus improve their health as well as their well-being, she added.

“The treatment of PPID itself is non-invasive and relatively easy; it can be given in a handful of pony nuts (feed) for example, ”she said. “The treatment for laminitis is obviously much more intensive. At the zoo, our management of laminitis must be balanced with the welfare needs of the equine. For example, we would limit movement from a large enclosure but not isolate a herd of equines to rest as this could be very stressful for the individual. We can give oral pain relief and other medications, but the possibility of regular conscious farriering and corrective shoeing is much less practical in a zoo environment.

“One of the main reasons I posted this was to educate the zoo vets about this disease, so they can test it early and treat it if necessary, before laminitis develops, thus dramatically increasing the disease. well-being, ”she continued.

It remains to be seen whether the disease would occur in free-range equines, Shotton said.

“I think it’s hard to say if this is something that all equines have (and always have) or if it is related to domestication or captivity,” she said. “I doubt anyone has looked for it in wild equines yet, although it would be fascinating research.

“It is also likely that even if this was a ‘natural’ disease process, wild equines could be predated or die of something else before they are old enough to develop this disease. It would be great to study older wild equines and see if PPID is present in those populations. “

The study, “Pituitary gland dysfunction pars intermedia (equine Cushing’s disease) in non-domestic equines at Marwell Wildlife: a case series.” A Chapman’s zebra (Equus quagga chapmani) and five Prewalksi horses (Equus ferus przewalksii) ”, Was published in the Zoo Journal and Wildlife Medicine.


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