Crocodiles may not be as highly resistant to infections as previously thought, as a newly released study shows a deadly bacterium was responsible for killing two saltwater crocs in the Top End.

Key points: The last report of a saltwater crocodile being infected with melioidosis was over 30 years ago

The last report of a saltwater crocodile being infected with melioidosis was over 30 years ago Darwin has the highest recorded rates of the deadly bacteria in any city in the world

Darwin has the highest recorded rates of the deadly bacteria in any city in the world An expert in the NT has said they are on the forefront of research into crocodile antibodies

The research, from Menzies School of Health Research and published in the Microbial Genomics journal, investigated the deaths of two hatchling saltwater crocodiles at Crocodylus Park in Darwin.

The two hatchlings, who died in 2016, were found to have contracted a north Australian strain of Melioidosis in the hatchling incubator.

Highest rate internationally

Melioidosis is a disease of humans and animals endemic to South-East Asia and northern Australia caused by the bacterium Burkholderia pseudomallei.

Infection is normally acquired through cuts, ingestion of contaminated soil or water and inhalation, particularly during severe weather events.

Lead author and Menzies researcher Ms Audrey Rachlin said Darwin has the highest recorded rates of melioidosis in any city in the world.

"It's ubiquitous, this disease is everywhere within our environment here in the Northern Territory," she said.

"It's called 'the great mimicker' because the infection can take many different forms, for some it can lead to pneumonia, septicaemia, neurological disease and death, depending on the host."

Researchers discovered melioidosis within crocodile hatchlings. ( Supplied: Menzies )

Although melioidosis has been identified in a wide array of animal species, the last report of a saltwater crocodile being infected by the disease in the Top End was over 30 years ago.

"Prior to this investigation, there is only a single report of infection of a crocodile in the Top End, and that was a limb wound occurring around 30 years ago," Ms Rachlin said.

"Our investigation into the two juvenile crocodiles combined epidemiological findings with high-resolution comparative genomics to determine the source of infection.

"It is possible these animals are getting this infection in the wild, but it's clearly rare as this species is very resilient."

Resilient Crocs may lead to medical advancements

According to Menzies' Tropical and Emerging Infections Diseases team leader Professor Bart Currie, collaborative studies with veterinary colleagues have been essential to gaining a better understanding of melioidosis and the danger of the disease to humans.

"Fortunately, improvements in prevention, diagnosis and treatment have led to mortality rates reducing to 10 per cent, compared to 30 per cent in earlier years," Professor Currie said.

Study collaborator and wildlife park owner Professor Grahame Webb said the NT has played a pioneering role in the technical challenges of developing a crocodile farming industry, with this sometimes involving issues related to human health.

Menzies researcher Ms Rachlin said the bacteria is "ubiquitous" throughout the Top End environment. ( Supplied: Menzies )

"The key issue here is that although we have found two hatchlings with the disease, the Territory breeds tens of thousands of crocs who are resistant, that is an exciting prospect," Professor Webb said.

"There is pharmaceutical and medical research into crocodiles and their antibodies happening all over the world … we are blessed here in the territory to be at the forefront of that research as the species is so prevalent."

Professor Webb said there is more to be discovered in relation to the disease.

"Working with Menzies has resulted in the crocodile industry implementing new operating procedures, which has helped both the health of the crocodiles and staff working with them," he said.

"We are in a unique position here in the Northern part of the country to conduct some interesting research and learn more about our wildlife, we have a wealth of expertise now and made inroads regarding this disease."

