A female rhinoceros exhibiting symptoms of a condition which claimed the lives of four of her conspecifics appears to have overcome her illness, despite exhaustive testing failing to identify the aetiological agent.
The mystery illness claimed the lives of four adult White Rhinoceros at Taronga Western Plains Zoo within a period of weeks in March, sparking an international investigation. Affected rhinos exhibited a range of signs, particularly neurological signs including stumbling and ataxia prior to their deaths.
The female also exhibited these signs, but survived the illness along with two other males which remain unaffected. Last month the zoo reported that the female White Rhino had improved and was assessed to have a good prognosis following intensive monitoring and supportive care after exhibiting neurological signs. All other affected animals had died despite intervention. The two remaining males, neither of whom have exhibited symptoms, remain healthy. No other animals at the zoo – including the black rhinoceros – have experienced the illness.
The intensive, eight-week-long investigation, lead by the Zoo, involved collaboration with Rhinoceros specialists in Africa and North America, Government virologists and veterinary services as well as multiple pathology laboratories.
A Working Group, consisting of the State’s most experienced veterinarians and pathologists including the Department of Primary Industries Chief Veterinary Officer was established to assist with the investigation.
Despite performing a battery of tests to isolate a bacterial, viral or environmental causes – a process which ruled out numerous possibilities – the results remain inconclusive. What investigators do know is that the deaths are unlikely to be due to bacterial infection, snake bite, organ failure, environmental toxins, food contamination and a suite of viruses including West Nile Virus and Hendra Virus.
According to Senior Veterinarian Benn Bryant, the Working Group is confident that the remaining White Rhinos pose no health risk and that quarantine restricts could be eased.
“The Working Group is confident that every possible avenue has been explored and that the full resources available to the Zoo and the Department of Primary Industries have been utilised,” he said.
“It’s not unusual in biomedical investigations that a cause for an illness cannot be categorically confirmed,” he added. “However, we have the ability to re-open the investigation at any time if new information comes to hand and to provide tissue samples for further testing.”
Bryant said staff continued to grieve for the lost animals. Despite the lifting of quarantine restrictions, the White Rhinos will be off exhibit for a period of months to facilitate scheduled maintenance.
Director of the Taronga Conservation Society Australia, Cameron Kerr, committed to ensure “that all aspects of the investigation including the extensive test results are reported and published to add to the global knowledge of this species.”