Christmas Island reptile killer identified

One of Australia’s critically endangered lizard species: Lister’s gecko. Credit: Parks Australia.

Christmas Island’s native reptile populations have experienced a severe decline with two species, Lister’s gecko and blue-tailed skink, having completely disappeared from the wild. Whereas previously the main driver of this decline was probably predation by invasive species and habitat destruction, now a silent killer threatens to wipe out the species altogether.

Those bred in captivity on Australian territory in the Indian Ocean are also mysteriously dying off, leaving the two species – which number only around 1,000 each – in danger of extinction. Veterinary scientists from the University of Sydney, the Australian Registry of Wildlife Health and the Taronga Conservation Society Australia have now discovered the cause of these deaths: a bacterium, Enterococcus lacertideformus (E. lacertideformus).

The bacteria was discovered in 2014 after captive reptiles showed facial deformities and lethargy, and some even died. Samples were taken and analyzed by microscopy and genetic testing.

The researchers’ findings, published in Frontiers in microbiologywill inform antibiotic trials on reptiles to see if the infection can be treated.

The bacterium develops in the animal’s head, then in its internal organs, before causing its death. It can be spread by direct contact, including through the mouths of reptiles or by reptiles biting each other, often during breeding season fights.

Christmas Island reptile killer identified

Infected gecko showing severe head and facial swelling associated with Enterococcus lacertideformus infection. Credit: Jessica Agius.

“This means that healthy captive animals should be separated from infected animals and should also be kept away from areas where infected animals have been,” said Jessica Agius, co-principal investigator and Ph.D. Sydney School of Veterinary Science.

Agius and the research team not only identified the bacterium, they decoded its genetic structure using whole genome sequencing.

Specific genes that may be associated with the bacterium’s ability to infect its host, invade its tissues and evade the immune system have been identified.

“We also found that the bacterium can surround itself with a biofilm, a ‘community of bacteria’ that can help it survive,” said Agius.

“Understanding how E. lacertideformus produces and maintains biofilm may provide insight into how to treat other species of biofilm-forming bacteria.”

Christmas Island reptile killer identified

PhD researcher Jessica Agius shines a light on critically endangered lizards on the ground on Christmas Island to find out if they are infected with Enterococcus lacertideformus. Credit: Jessica Agius.

Research of the genetic code suggested that the killer bacteria was susceptible to most antibiotics.

Professor David Phalen, Co-Head of Research and Ms. Agius’ Ph.D. supervisor, said: “This suggests that infected animals could be successfully treated. This is what we need to determine now.”

In another effort to protect endangered reptiles on Christmas Island, a population of blue-tailed skinks has been established on the Cocos Islands. Ms Agius played a vital role in the translocation, testing reptiles on the Cocos Islands to ensure they were free of E. lacertideformus.

“It is essential that we act now to ensure the survival of these native reptiles,” said Ms Agius.

Save the Reptiles of Christmas Island

More information:
Jessica Esther Agius et al, Genomic insights into the pathogenicity of a new biofilm-forming Enterococcus sp. Bacteria (Enterococcus lacertideformus) identified in reptiles, Frontiers in microbiology (2021). DOI: 10.3389/fmicb.2021.635208

Provided by the University of Sydney

Quote: Christmas Island reptile killer identified (2021, March 18) Retrieved February 15, 2022 from

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