Credit: Parks Australia.
The numbers of native reptiles on Christmas Island have seen a sharp decline with two species, the Lester gecko and the blue-tailed eagle, have completely disappeared from the wild. While previously the main driver of this decline was the potential predation of invasive species and habitat destruction, the silent killer now threatens to wipe out the species altogether.
And those bred in captivity in the Australian Territory of the Indian Ocean are dying mysteriously, leaving the two species – which number only around 1,000 – in danger of extinction. Veterinarians from the University of Sydney, the Australian Register of Wildlife Health and the Taronga Conservation Society of Australia have now discovered the cause of these deaths: Enterococcus lacertideformus (E. lacertideformus).
The bacterium was discovered in 2014 after captive reptiles developed facial abnormalities and lethargy, and some even died. Samples were collected and analyzed using microscopy and genetic testing.
Researchers’ results published in Frontiers in Microbiology, Will inform antibiotic trials on reptiles to see if the infection can be treated.
Bacteria grow in the animal’s head, then into its internal organs, before eventually causing death. It can spread by direct contact – including through reptile mouths, or by reptiles biting each other – often during breeding season fights.
“This means that healthy captive animals should be kept away from infected animals and they should also be kept away from areas where infected animals have been infected,” said Jessica Agios, associate researcher and doctoral candidate at the Sydney College of Veterinary Sciences.
Not only did Agios and the research team identify the bacteria, but they decoded their genetic makeup using whole genome sequencing.
Certain genes have been identified that are likely related to the bacteria’s ability to infect its host, invade its own tissues, and evade the immune system.
“We also found that bacteria can surround themselves with a biofilm – a ‘community of bacteria’ that can help them survive,” Agios said.
“Understanding how E. lacertideformus is produced and maintained may provide insights into how to deal with other types of biofilm-forming bacteria.”
Research into the genetic code indicates that the deadly bacteria were susceptible to most of the antibiotics.
“This indicates that infected animals can be treated successfully. This is what we need to define now,” said Professor David Fallen, co-head of research and PhD supervisor at Ms Agios.
In another effort to protect the endangered Christmas Island reptiles, a group of blue-tailed sausages have been established in the Cocos Islands. An important role in the transport was played by Ms. Agios, who tested reptiles in the Cocos Islands for E. lacertideformus bacteria.
“It is critical that we act now to ensure the survival of these native reptiles,” said Ms. Agios.