Yes, unfortunately, you read that right. According to David Wilson, professor of infectious diseases at the Burnet Institute in Melbourne, about half of the koalas in Australia are infected with chlamydia. In some areas, the spread is significantly worse. “In closed populations, the majority can be infected – sometimes up to 80 percent,” Wilson recently told BBC.
Among humans, chlamydia (or “the clap,” as it is colloquially known) is considered a painful, embarrassing, but curable sexually transmitted disease. However, the STD often causes no symptoms at all, and if untreated can lead to serious health problems, including permanent damage to a female’s reproductive system. In nature, the chlamydia pathogen is tens of thousands of years old, and one of the strains that is currently infecting Australia’s koalas (Chlamydia pecorum) is painful and can be lethal. Its effects include blindness, respiratory infection, infertility and what’s known as “dirty tail.”
In his interview with BBC, Professor Wilson described the infection in gruesome detail: “Dirty tail is actually really awful. The urinary tract gets inflamed and expands substantially; it’s incredibly painful. They get discharge and many koalas die.”
Another strain of the disease, Chlamydia pneumoniae, has also been detected in koalas and can spread to other species, though it is less common.
The rampant spread of this disease has exacerbated the koala’s vulnerable status in the wild. Because of their near exclusive diet of eucalyptus leaves, koalas (Phascolarctos cinereus) have been greatly impacted by human development in the Australian bush. Professor Corey Bradshaw, an ecologist at the University of Adelaide, has reported that 40 percent of this land has been cleared for agriculture, logging, mining and urbanization. Now in closer contact with humans, the slow and perpetually drowsy koalas are dying in large numbers. An estimated 4,000 are killed by cars and dogs every year, with populations dropping 40 percent in Queensland and 33 percent in New South Wales. The marsupial is also very sensitive to climate change, which is expected to hit Australia the hardest in terms of temperature rise and drought.
But this cavalcade of disasters is not yet complete. The chlamydia epidemic that is devastating koala populations – spread through fighting, mating and from mother to infant – has been accelerated by an HIV-like retrovirus that suppresses koala’s immune systems. The retrovirus is untreatable, though a vaccine developed for the chlamydia has shown to be effective in females. Unfortunately, as Peter Timms, professor of microbiology at Queensland University, told the New York Times, “It’s going to be impossible to vaccinate all wild koalas.”
Professor Wilson has suggested a controversial solution to stopping the disease: A strategic cull of the continent’s koalas. “They’re transmitting chlamydia to each other and many of them can’t be healed. These koalas are in a lot of pain and if they’re out of the time-range of antibiotics being effective; the humane thing to do is probably to euthanize them,” he told BBC.
However Australia decides to assist one of its most iconic species, one thing is clear: The koala is very sick, and it’s running out of time.