Scientists Identify 'Last Chlamydia-free' Koala Population

The long-term survival of the iconic koala—a plant-eating marsupial native to Australia—is under threat from the spread of the bacterial infection chlamydia, which was first identified in the north of the country in 1970.

Alongside other factors such as habitat destruction and road deaths, the disease is playing a significant role in the population declines that the species is experiencing in this region. In fact, koalas are classified as "Vulnerable" by the International Union for Conservation of Nature's Red List.

Now, a team of researchers from the University of Adelaide, South Australia, has identified what may be the last large population of koalas that is free from chlamydia, according to a study funded by the Morris Animal Foundation which has been published in the journal Nature Scientific Reports.

The scientists say the population—located on Kangaroo Island just off the Adelaide coast—could hold the keys to ensuring the survival of the species.

"This is a very important finding because chlamydial disease is so prevalent and efforts to fight it have so far been unsuccessful," Natasha Speight, from Adelaide's School of Animal and Veterinary Sciences, said in a statement. "These koalas could potentially be used as a disease-free breeding colony in the future."

For their study, the team investigated the prevalence of the Chlamydia pecorum bacterial species—the most common strain to infect the marsupials—among the two largest koala populations in the state of South Australia, found in Kangaroo Island (KI) and the Mount Lofty Ranges (MLR).

While chlamydia is common in koalas, those living in the south of Australia appear to be faring slightly better than their northern counterparts, in part, because rates of the infection seem to be lower there. To understand the prevalence of the disease, the team captured and released a total of 245 koalas from KI and MLR and tested them for chlamydia.

They found that around 47 percent of the MLR population tested positive for the bacteria, although only 4 percent showed signs of the clinical disease. On the other hand, the researchers found that the KI population was entirely free of the bacteria—a conclusion they made with "95 percent confidence."

Furthermore, the team also looked through more than 13,000 historical veterinary records from the island, founding no mention of the disease.

"Chlamydia is the greatest disease threat to koalas and has significantly contributed to population declines of koalas in parts of Australia," Speight told Newsweek. "It causes conjunctivitis that can lead to blindness, and urinary tract and reproductive tract disease that can cause infertility. Severe infections can cause death of koalas."

"South Australian koalas, particularly those on Kangaroo Island could be used as an insurance population for the koala species for the future," she said.

This article was updated to include additional comments from Natasha Speight.

A koala rests in the rehabilitation ward at The Australian Wildlife Hospital on September 19, 2008 in Beerwah on The Sunshine Coast, Australia. Lisa Maree Williams/Getty Images