Summer 2004
Mystery Condition

 



Strange foreign bodies, roundworms, or a blockage in the bile duct – truth is, vets in the Northern Territory
aren’t sure what killed one of Australia’s four captive spectacled hare wallabies

 The loss of a small, rare resident of the Northern Territory Wildlife Park has left staff saddened and a little puzzled.

Stuart Little, a four year old spectacled hare wallaby, became acutely ill in June 2003.    Veterinarians did everything they could to save him, but were unable to diagnose the mystery condition before he died.   

This is Stuart’s story.

The Spectacled Hare Wallaby (Lagorchestes conspicillatus) is a small, nocturnal mammal, common in some parts of Queensland, but scattered in tropical grasslands in the Northern Territory and Western Australia.

According to expert Sandy Ingleby from the Australian Museum, the species is well adapted to arid or seasonally arid environments due to a low metabolic rate and an ability to produce a highly concentrated urine.

In the wild, the spectacled hare wallaby lives off grasses, herb foliage, fruit and seeds.    Stuart’s diet in captivity consisted of native grasses, pelleted feed, fruit and vegetables.

According to the Australian Museum Management Program Regional Census, there are only four spectacled hare wallabies in captivity in Australia.    Prior to Stuart’s death, the Northern Territory Wildlife Park was home to three of them.

The species, which is listed as near threatened, is usually quite timid but Stuart had been hand-raised since birth and enjoyed occasional physical contact.

At the end of June, a keeper noticed Stuart had been off his food for about three days.    Veterinarian Jamin Farebrother examined Stuart.

“His temperature was normal but he seemed to be in pain.    We thought it might be neurological so we decided to X-ray his spine,” Dr. Farebrother says.

 Strange foreign bodies

Stuart was placed under a general anaesthetic and radiographs were taken.    The radiographs revealed some radiopaque pebble like substances in the anterior abdomen and distal intestine.    They were easily palpated in the stomach

Dr Farebrother prescribed canola oil to promote passage of the objects through the gut and instructed keepers to examine Stuart's faeces daily.

According to locum veterinarian Stephen Cutter, Stuart soon perked up and began to pass soft faeces – unfortunately, he crashed within a week.    When Dr. Cutter examined Stuart on June 30, he had collapsed.

“He was looking neurologic – he’d fall on his face, he was twitchy and hypermetric,” Dr. Cutter says.

Intravenous fluids were given via Stuart’s tail vein and blood was taken for investigation.    Stuart was given a course of enrofloxacin and protexin, and a tetanus antitoxin was administered as a precaution.

The blood test revealed an elevation in white blood cells, particularly neutrophils.

Stuart fortunately tolerated hospitalisation and treatment very well.

“Even when he was really sick he wanted to be held.” Dr. Cutter says.    The treatment appeared to be working – by mid-July Stuart seemed well on the road to recovery.

Ten day later keepers reported that Stuart’s skin appeared very yellow.

“He was actually canary yellow.   He was the most yellow animal I have ever seen, especially his mucous membranes and his eyes.” Dr. Cutter says.

The previous procedure was repeated – blood sample were collected and Stuart was placed under a general anaesthetic and radiographed to determine whether the mysterious foreign bodies had dissipated or whether they might be obstructing the bile duct.

“It was confirmed that the foreign bodies had moved, but they didn’t appear to be situated in a manner that hamper the bile duct.” Dr Cutter says.

The veterinary team decided against a laparotomy at this stage, continuing to opt for medical management of the problem.    Stuart was placed on a course of enrofloxacin and amoxicillin/clavulanic acid, as well as flunixin for the pain.    His condition improved once again, but this time the improvement was short-lived.

During the first week of August, Stuart crashed again.

“He was less jaundiced, but he’d gone right off his food and wasn’t drinking.    He literally collapsed,” Dr Cutter says.

A laparotomy revealed a gut full of gas and blood clots in the pelvis.     There were also worms present in the thoracic and abdominal cavities, but nothing that corresponded with the foreign bodies seen on earlier radiographs.

“He hadn’t passed anything that could be construed as what we saw on the radiographs,” Dr. Cutter says.

The team decided to euthanase Stuart and conduct a full post mortem.     Histopathological examination of the liver revealed evidence of biliary hyperplasia and biliary stasis, consistent with the clinical finding of jaundice, as well as evidence of increased red cell destruction, suggested by haemosiderin present in both Kupffer’s cells in the liver and in the spleen.

Clearly Stuart had had some form of blockage of the bile duct that was resolved by the time of death, but the cause of the blockage and the nature of the foreign bodies remains a mystery.

A parasitology report revealed the worms were filaroid nematodes Breinlia boltoni.    A similar species is known to cause peritonitis in pademelons.

“It is possible a worm could have become entangled in the bile duct, but we will never know,” Dr Cutter says.

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This article is reproduced with the kind permission of the Veterinarian Magazine as is taken from their October 2003 issue.    Copyright remains with them and cannot be reproduced without written consent.    We also offer our thanks to the author.

Further information can be found at www.theveterinarian.com.au  

 
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