University of Sydney researchers have reported the first case of tuberculosis in a juvenile Australian sea lion that died on a beach at Kingscote, Kangaroo Island in 2017.
Scientists have pointed to the case as an example of the dangers of animal diseases being transferred to humans who handle wild animals.
The COVID-19 coronavirus could have been one of these animal diseases that transferred to humans, while zoonotic diseases have been responsible for other pandemics.
"This finding is significant because tuberculosis is a zoonotic disease, which means it is transferable to humans, so there are public health risks to consider," Dr Gray said.
"There is risk of transmission for researchers handling the animals, as well as anyone involved in animal rescue or washed-up carcass disposal, or those working at rehabilitation centres and involved in the disease diagnostic process."
The type of disease found in the juvenile sea lion was not the typical presentation of tuberculosis, as this was not found in the animal's lungs, but in its abdomen.
The discovery has been published in the Journal of Wildlife Diseases.
The discovery was made after a three-year-old juvenile male Australian sea lion died in 2017 shortly after hauling itself onto Kingscote beach.
During an autopsy, the animal was determined to have small intestinal perforation and partial obstruction due to a strangulating fibrous mass.
"This unusual finding means we need to maintain constant vigilance around zoonotic disease risk for any person in close contact with free-ranging pinnipeds [seals, sea lions and walruses] of juvenile age or older, independent of presenting signs," Dr Gray said.
Dr Gray conducted the study with Mr Scott Lindsay, a veterinary pathologist at the University of Adelaide and a PhD candidate at the University of Sydney.
The diseased sea lion was found not far from the Seal Bay breeding colony on the south coast of KI where the animal likely was born, he said.
"A review of tuberculosis in Australian sea lions and other pinniped species suggests the disease is likely endemic in the population and is now confirmed in a geographical region contributing to the majority of pup births in this endangered species," Mr Lindsay said.
"Increased serological surveillance of the population is recommended to assess the species' risk from this and other endemic diseases."
Dr Rachael Gray and her team of scientists have been conducting world-class research in South Australia in order to save the endangered sea lion.
The Australian sea lion is the only pinniped species endemic to Australian waters, ranging from the Houtman Abrolhos islands off the west coast of Western Australia to the Pages Islands in South Australia.
The species is endangered, with a decreasing population trend (International Union for Conservation of Nature Red List) from a low baseline attributed to 19th century commercial sealing.
The small population size increases the species' risk of catastrophic disease impact, as seen in the New Zealand sea lion where Klebsiellapneumoniae-associated neonatal septicaemia and meningitis contributed to 58 percent of pup deaths between 2006 and 2010.
The Australian sea lion population in SA is also being impacted on by hookworm infection of its pups, providing an existing disease pressure.
In another COVID connection, an innovative research program being undertaken by Dr Gray and the SA Department for Environment and Water was treating the Seal Bay pups with veterinary treatment Ivermectin.
Ivermectin was also investigated as a treatment for coronavirus in humans.
Further recovery from a significant disease impact would be limited by the species' low reproductive rate, Dr Gray said.
About 86 percent of pup births occur in South Australia, where there is dependence on just eight large breeding colonies, including Seal Bay, Kangaroo Island.