Kangaroo Island koalas hold key to population health

South Australia’s Kangaroo Island koala population may hold the key to ensuring the continued survival of koala communities on the mainland after it was discovered the island’s population are free from the disease ravaging their mainland brethren.

Scientists from the University of Adelaide discovered that, unlike every other large population in the country, koalas from Kangaroo Island are free from infection by Chlamydia percorum, the disease ravaging the mainland population.

“The impact of Chlamydia on populations of koalas in Queensland and New South Wales is devastating, with high levels of severe disease and death, and common infertility,” says researcher Jessica Fabijan, PhD candidate with the University of Adelaide’s School of Animal and Veterinary Sciences.

“This last large, isolated Chlamydia-free population holds significant importance as insurance for the future of the species. We may need our Kangaroo Island koalas to re-populate other declining populations.”

The researchers captured and released 75 wild koalas from the Mount Lofty Ranges and 170 koalas from Kangaroo Island (KI). Each koala was checked by a veterinarian and tested for Chlamydia pecorum and koala retrovirus. On KI, historical veterinary records of koalas were searched for incidence of chlamydial disease. There were over 13,000 records collected over 22 years by DEW.

The researchers found that 46.7% of koalas from the Mount Lofty Ranges were positive for Chlamydia, although the vast majority not showing signs of disease. All Kangaroo Island koalas tested negatively for Chlamydia and no disease was observed. There were no definitive cases of chlamydial disease in the 13,000 past records of koala examinations on KI. “This is a very important finding because Chlamydial disease is so prevalent and efforts to fight it have so far been unsuccessful,” says project leader Dr Natasha Speight, also from the University of Adelaide’s School of Animal and Veterinary Sciences. “Although, South Australian and Victorian koala populations are stable, this is believed to be at least partly due to current lower prevalence and severity of Chlamydial disease.”

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