A Chlamydia Vaccine Sparks a Koala Baby Boom in Queensland

For Australia’s koalas, chlamydia has long been a quiet catastrophe. The bacterial infection causes blindness, infertility and painful illness, and in some populations it has spread so widely that it threatens the animals’ very survival. At Elanora, on Queensland’s Gold Coast, the disease had infected an estimated 70 percent of the local koalas — a population on a grim trajectory. But a five-year vaccination project has turned that story around so dramatically that conservationists are now describing a koala baby boom.

Led by the Queensland University of Technology and Currumbin Wildlife Hospital, with support from WWF-Australia and the furniture brand Koala, the project vaccinated more than 500 koalas over five years. The results have exceeded even the team’s hopes. Chlamydia-related hospital admissions from the area dropped by more than 75 percent, and the infection rate among the Elanora koalas fell from around 70 percent to roughly 17.5 percent — a transformation in the health of a whole community of animals.

“The bacterial infection causes blindness, infertility and painful illness, and in some populations it has spread so widely that it threatens the animals’ very survival.”

With the disease in retreat, the koalas have begun doing what healthy koalas do best: breeding. The project has documented the birth of 41 joeys and 13 “grand-joeys” — the offspring of vaccinated animals’ own young — compelling evidence that protecting the adults has rippled out into a thriving new generation. As senior vet Dr Michael Pyne put it, “Chlamydia is a horrible disease; it’s devastating for koalas… vaccinating these koalas has achieved far more than we could ever have hoped.”

The team isn’t stopping there. QUT researchers are developing a biodegradable, controlled-release implant that would allow a koala to be fully vaccinated in a single capture rather than two, making the program far easier to scale across the wild. As WWF’s Tanya Pritchard observed, the Elanora koalas “have gone from severely diseased to now experiencing a baby boom — it’s remarkable.” For one of the world’s most beloved and most threatened animals, a small vaccine is proving to be a powerful tool for hope.