The Analysis Of Koala's Life
Australia’s iconic furry friend, the Koala, is facing many challenges making it vulnerable to extinction. Amidst recent bushfires destroying its habitat, they also face the devastation of the bacterial animal pathogen Chlamydia Pecorum (C. Pecorum). Although two chlamydia species are reported to infect Koalas (C. Pecorum and C. Pneumoniae), C. Pecorum is found to be more pathogenic and thus will be the focus of this article (McCallum, H. et al. 2017). In the Koala, infectious diseases caused by this pathogen are one of the key threats to its long term-survival and conservation (Jelocnik, M. 2019). To prevent further decline of Koala populations, methods of disease control such as vaccines, antibiotics and quarantine centres are being applied. Ensuring the survival of the koala population is important to Australian tourism but also identity. Can we imagine an Australia without the koala?
The problem for our koalas
Almost all of Australia’s mainland koalas spanning from Queensland to New South Wales are infected by C. Pecorum (Polkinghorne, A. et al. 2013). Infection by this bacterial pathogen significantly impacts koala health affecting their conjunctiva and urogenital tract resulting in respiratory, ocular and urogenital disease. This then further leads to sterility, cystitis, pneumonia, blindness and arthritis (Phillips, S. et al. 2019). As these problems overwhelm the koalas, a reduction in reproductive output and increased mortality manifests the population.
On top of the unreliable natural environment Koalas experience in Australia - such as bushfires - the burden of C. Pecorum on their health becomes an added complication for the survival of the species. Environmental factors leading to a loss or reduction of habitats sees fewer living spaces, seeing koalas isolated into smaller areas, making it harder to reproduce with healthy mates. Thus, the resulting overpopulation increases the likelihood of the disease spreading.
So, is C. Pecorum putting Koalas at risk of extinction? Yes and No.
In conjunction with other risk factors such as habitat loss and overpopulation, infection by the disease is supported due to more contact between Koalas. Therefore, the disease is capable of bringing Koalas closer to extinction, IF additional factors are present which contribute to an increase in the rate of transmission.
Alike humans, koalas can appear symptomatic or more commonly asymptomatic when infected (Jelocnik, M. 2019), making it challenging to accurately assess the health of the species’ population. Although there isn’t a cure for C. Pecorum, there are a number of ways to control its spread once detected. One way being quarantine, as isolation will reduce the spread of disease as most are familiar with in today’s Covid-19 outbreak. Other methods which can assist in reversing population decline due to C. Pecorum include habitat modification and protection, culling and euthanasia, antibiotics, and vaccines.
The habitat of koalas is closely linked to their survival. Habitat protection and modification is a common control method to reduce pathogen transmission (McCallum, H. et al. 2017). As the disease manifests in stress such as habitat destruction (Jelocnik, M. 2019), to ensure the reduction of C. Pecorum, habitat protection is needed to allow for a healthy growth which sees a maintenance in nutrition and genetic variability.
Culling and euthanasia are possible control methods for the spread of C. Pecorum. Culling of infected koalas is suggested to enable rapid population recovery and disease elimination (McCallum, H. et al. 2017). In extreme cases, if there are significant clinical signs of the koala having the disease and is tested positive, it may be euthanised. For example, this is the case for older female koalas with detectable cysts or those rendered sterile (McCallum, H. et al. 2017). Further, However, both methods are disputed regarding its ethics.
In treating chlamydial infection, antibiotics are used extensively, though they aren’t always successful. There are two types available – enrofloxacin and chloramphenicol which is primarily used (Polkinghorne, A. et al. 2013). Daily administration for at least a month in quarantine and appropriate management is needed to avoid the side effects such as how it affects the koala’s gut microflora; which can contribute to antibiotic resistance (McCallum, H. et al. 2017). In some cases, koalas may not be suitable for antibiotic treatment if they are already chronically diseased, have poor body condition or if they are already associated with Koala Retrovirus where they experience immunodeficiency. However, it must be noted that antibiotics are only for the early stages of the disease and don’t prevent reinfection.
Alike the human strain of chlamydia, a successful vaccine is yet to be made for C. Pecorum. A published field trial has shown that in vaccinated koalas, there is no significant reduction in the incidence of new infections (McCallum, H. et al. 2017). In comparison to those unvaccinated and positively tested koalas, the vaccinations are reported to alleviate the burden of the disease. Moreover, a modelling study has proposed that a vaccine with a success rate of 75% provided to 10% of koalas annually could see a reversal of koala population decline within 5 years (McCallum, H. et al. 2017). Thus, the creation of a successful vaccine could be the key to save the Australian furry icon from extinction. However, there are negative aspects to the process of vaccination from the capture, associated stress and handling of the koalas which could set back stopping further decline of their population.
How does it impact us?
Imagine Australia without the Koala. The prevalence of C. Pecorum in koala populations pose the risk of extinction which brings about the social cost of the partial loss of Australia’s social identity. It also economically impacts the country in eco-tourism. The Australian Koala Foundation (2016) found that $3.2 billion per annum is earned through koala tourism, where 75% of tourists say they would like to see a koala. Thus, it can be argued that the survival of koala populations is prime to Australian identity and tourism.
The future for our koalas
Despite efforts to control and eliminate the disease, a great deal of progress is still to be made in research; particularly in relation to vaccinations. It is worthwhile to note that a safe and effective vaccine against the human strains of chlamydia has yet to be developed despite over 50 years of research (McCallum, H. et al. 2017). Continuing the efforts to control the spread of the disease can increase the chances of survival for the Koala. However, these chances are without taking into account natural disasters and human actions which cause stress in the population, therefore increasing the prevalence of C. Pecorum in populations. Essentially, the development of an effective vaccine to provide Koalas immunity to the disease could bring them farther from extinction. Alike other diseases in which a cure is yet to be developed, the future of the iconic Australian Koalas’ chlamydia and its prevention remains ambiguous.