Epidemics, economics and extinction

The arrival of horse flu provides an instructive case-study into the threats posed by animal borne-disease—Australia’s vulnerability to them and the strength and scale of response required to deal with them. 

As with emergency medicine, the speed of response is critical—in many cases, a delayed response is often too late to make any difference.  Rather than being a chance occurrence, epidemiologists and veterinary researchers have been anticipating epidemics like this, so the events of recent months provide a useful opportunity to gauge our preparedness.  In particular it is useful to contrast the response to horse-flu in Australia with the reaction to other animal-borne diseases, notably the facial-tumour disease affecting Tasmanian Devils.  Are threats of economic and ecological disaster treated differently, and what are the short and long-term repercussions for Australia if we get it wrong?

Twelve years ago, reports emerged of an unknown disease affecting Tasmanian Devils, leading to the growth of large tumours on their face and upper body.  In addition to disfiguring the animals, the disease is both fatal and incurable, infected animals dying within several months of first showing symptoms.  Biologists were quick to realise the implications of this epidemic, warning of potential ecological disaster if immediate action wasn’t taken.  In the decade since this disease first appeared, despite concerted efforts from biologists, pathologists, epidemiologists, veterinarians and other researchers, we still don’t know exactly what the disease is or how it can be treated.  Devils are dying at unprecedented rates in the wild, with declines of 90 per cent reported in the north-east during 2002–05, compared to baseline numbers in 1992–5. 

At a scientific forum in Hobart in 2007, researchers agreed that it represented a previously unknown and highly virulent form of transmissible cancer: where it originated and whether it can be cured remain unknown and are the focus of current research.  Many people involved in this work consider it likely that devils will become extinct in the wild, and have already established “insurance” populations on other islands and in captive facilities like Healesville Sanctuary, taking precautions to ensure all individuals are disease free.  The future prospects are not good, and a world without Tasmanian Devils in the wild seems a very real possibility.

To make matters worse, in 2001 foxes were deliberately introduced to Tasmania.  The response to this well-publicised act was painfully slow, despite being likened to terrorism by some of Australia’s leading biologists. Indeed, it was late 2006 before the Minister for Primary Industries finally announced funding for the ten year Fox Eradication strategy, far too late to make any real difference according to many biologists.

The combined effects of an introduced predator and an unchecked disease is truly an alarming prospect for Tasmania’s native fauna.  Researchers are already drawing parallels with the extinction of Thylacines early last century, begging the question of whether we’ve learned anything about environmental management over the past century.  The implications extend well beyond devils, with Australia’s next largest predatory marsupial (eastern quolls) and all manner of other native species threatened with imminent extinction.  Will predatory foxes replace the scavenging devils, and how will that affect the many Tasmanian bird species that nest on the ground?  Only time will tell, but international attention is focused on this matter, made all the more shocking by the fact that it was both intentional and avoidable. 

Another animal-borne disease that has appeared on our shores recently is equine influenza.  Neither fatal nor disfiguring and having no effect on native fauna, the speed and scale of the response to this disease were unprecedented.  Within two days of being reported, all movement of horses within New South Wales was halted, large-scale testing of all suspected infections was conducted and all infected animals were held in tight quarantine conditions (extending to all horses and even zebras and rhinoceroses in zoos).  Within nine days of the first case, the Prime Minister announced a full judicial inquiry to find out how Australia’s famed quarantine protocols were breached and determine how best to ensure the disease is restricted, controlled and ultimately eradicated. 

The worst case scenario if this disease actually took hold in Australia is that vaccines would need to be imported and distributed to ensure no more horses became infected, and Australia would lose its status as a horse flu-free country.  From an animal welfare point of view, there would be remarkably few implications.  Very young and older horses are more vulnerable to the disease, increasing the likelihood of premature mortality, typically through complications arising from secondary infections.  Otherwise, it would be back to business as normal. 

Likewise, there are few implications from a conservation point of view.  Horse flu may infect wild populations of horses which, if anything, would be a positive outcome, diminishing the damage done to our sensitive native habitats by brumbies. 

From an economic point of view, there would be serious short and medium term implications, leading to real hardship for many of the 249,000 people employed in Australia’s racing industry, exemplified by the recent situation in NSW where a complete standstill on the movement of horses was enforced.  Yet, once the Australian horse population had been vaccinated, the racing industry could return to normal, just as in South Africa, after the horse flu in 1986.

Reflecting on these two examples, several points are clear.  Australian society—as evinced by the action (or lack thereof) of its representative governments—is far more concerned about economic issues than environmental ones.  While this is hardly surprising, the consequences of this disparity are alarming.  We have the capacity to act rapidly and decisively in a coordinated and measured way to halt virulent animal-borne diseases.  Considerable resources can be mobilized; state and federal governments can work together to ensure the risks associated with animal-borne disease are contained and minimized.  Yet, when we choose to do so depends on the circumstances, and the possibility of economic loss far outweighs the possibility of extinction in catalysing action. This raises the question: what are the economic implications of extinction of large numbers of native species?  As native animals go, the Tasmanian Devil is more charismatic than most, inspiring cartoon characters and acting as a poster child for conservation, sustainable development and environmental management.  Would Tasmania continue to attract as many domestic and international tourist dollars if there were no devils left?  It is well within our power to ensure this question remains unanswered. 

By marshalling the considerable expertise currently focused on this issue and matching the scale of the threat with the magnitude of response, these extinctions can be averted.  More broadly, we need to re-evaluate efforts currently being directed towards similar threats elsewhere in Australia.  Invasive species like Cane Toads and Buffel Grass, continued land-clearing and poorly-regulated development continue to march across Australia, laying waste to native habitats and threatening entire ecosystems. 

If history has taught us anything, regardless of whether it’s a tumour, the flu or a thousand cuts: death is permanent and extinction is forever.

Dr David M Watson, Associate Professor in Ecology, leads the Ecology and Biodiversity group at the Institute of Land, Water and Society at Charles Sturt University, Albury. 

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