The killer of a critically endangered reptile from Christmas Island has been identified

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

Bacteria responsible for the death of critically endangered species.

Because wild populations are decimated, Lister’s gecko and blonde skink exist only in captivity. Researchers at the University of Sydney have discovered a bacterium that could cause their potential extinction.

Reptile populations on Christmas Island are in serious decline with two species, Lister’s gecko and blue-tailed skin, which have completely disappeared from the wild. Although previously the main driver of this fall was probably the looting of invasive species and the destruction of habitats, the silent killer now threatens to wipe out the species completely.

Those bred in captivity on Australian territory in the Indian Ocean are also mysteriously dying, leaving two species – of which there are only about 1,000 – in danger of extinction. Veterinary scientists from the University of Sydney, the Australian Wildlife Health Registry and the Taronga Conservation Society Australia have discovered the cause of this death: Enterococcus lacertideformus (E. lacertideformus).

Infected gecko

An infected gecko showing severe swelling of the head and face associated with Enterococcus lacertideformus infection. Credit: Jessica Agius

The bacterium was discovered in 2014 after reptiles in captivity had facial deformities and lethargy, and some even died. Samples were collected and analyzed using microscopy and genetic testing. The findings of the researchers, published in Boundaries in microbiology, will report antibiotic tests on reptiles to see if the infection can be treated.

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

“This means that healthy animals in captivity should be kept separate from infected ones, and they should also be kept away from areas where infected animals have been,” said Jessica Agius, co-lead researcher and PhD candidate at the Sydney School of Veterinary Science.

Jessica Agius

Doctoral researcher Jessica Agius pointing out critically endangered lizards in the field on Christmas Island to find out if they are infected with Enterococcus lacertideformus. Credit: Jessica Agius

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

Specific genes have been identified that are likely to be associated with the ability of a bacterium to infect a host, attack its tissue, and evade the immune system.

“We also discovered that a bacterium can be surrounded by biofilm – a‘ community of bacteria ’that can help it survive,” Ms Agius said.

“Understanding how E. lacertideformus Producing and maintaining a biofilm can provide insight into how to treat other types of bacteria that make up a biofilm. “

A search of the genetic code suggested that the killer bacterium is susceptible to most antibiotics.

Professor David Phalen, co-leader of the study and supervisor of Ms. Agius, said: “This suggests that infected animals can be successfully treated. That is what we must establish now. ”

In another effort to protect endangered reptiles on Christmas Island, a population of blue-tailed skunks has been established on the Cocos Islands. Ms. Agius played a crucial role in the translocation, testing reptiles in the Cocos Islands to make sure they were released E. lacertideformus.

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

Reference: “Genomic insight into the pathogenicity of creating a new biofilm Enterococcus sp. Bacteria (Enterococcus lacertideformus) Identified in reptiles ”from
Jessica Esther Agius, David Norton Phalen, Karrie Rose and John-Sebastian Eden, March 2, 2021, Boundaries in microbiology.
DOI: 10.3389 / fmicb.2021.635208

Statement: The authors thank the Westmead Institute for Medical Research, the Sydney School of Veterinary Science – University of Sydney, the Australian Registry of Wildlife Health – Taronga Conservation Society Australia, and Christmas Island National Park – Parks Australia for their logistical and financial support.