To Kill or Not To Kill

Within the last 20 years the koala population has decreased by 40% in Queensland and 33% in New South Wales. There are various causes for this decline including habitat loss, predation, car accidents, and disease, particularly Chlamydia. Approximately 50% of the wild koala population is infected with chlamydia, with an increase of 80% in closed populations. It infects males, females and juvenile koalas causing blindness, infertility, “dirty tail” or inflammation of the urinary tract, and death. The strain of chlamydia is different from the strain that afflicts humans, however it can still be transmitted via exposure to koala’s urine. Unlike the human strain, simple antibiotic distribution is not a viable option. The treatment eliminates the natural gut flora essential for digestion of eucalyptus leaves, koala’s primary diet. In addition, if the disease is too severe the antibiotic will have little to no effect. So what can be done to eradicate chlamydia in the koala population?

Dr. David Wilson, from the Burnet Institute in Melbourne, proposed a radical strategy, in which the infected koala population should be euthanized. Using a simulation model on a well-studied koala population, Dr. Wilson demonstrated population growth occurring in 4 years; by the 7-year mark the population would surpass the current koala population. While this solution is quite extreme, it would help alleviate the koala’s excruciating symptoms, and halt the transmission of chlamydia to uninfected individuals. Australia is also known for drastic resolutions to their wildlife complications e.g. the eradication of feral cats and purposeful infection of an invasive species of rabbits. However a model cannot always predict the unexpected; an opportunistic species could push the remaining koalas into extinction. It is therefore important to ask: Is there another solution for these diseased koalas?

Scientists are currently sequencing the koala genome in hopes of finding clues to combat the virus. With the discovery of the IFN-g gene, scientists will acquire an understanding of the koala’s immune response. Trials of the developing vaccine have proven to be successful, showing a decrease in infection rate in koalas. This in conjunction with the newly acquired genetic information will lead to a vaccine in approximately 3 years.

Do we wait 3 years for a vaccine and risk losing the koala population? Or do we bring koalas to the brink of extinction now, in the hopes of proliferation? As it stands now the severity of individual cases vary. While waiting for the vaccine we can still distribute antibiotics to the less severe cases. With the rise of severe chlamydia cases, we must consider euthanizing these koalas.



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