Tag Archives: Australia

A New Vector for Leishmania

It isn’t every day that we learn about the discovery of an entirely new vector for an important vector-borne disease. A new report by the Australian Department of Agriculture and Fisheries has identified a new species of Leishmania that is transmitted by midges, not the usual vector, sandflies. Leishmania is a vector-borne protozoan parasite that causes an ulcerative disease known as Leishmaniasis or Kala-azar. Leishmaniasis is a disease primarily of the tropics and subtropics and is considered one of the most neglected infectious diseases in the world. The usual vectors are phlebotomine sandflies.

Australia (along with Antarctica) was thought to be the only continent free of Leishmania when locally-acquired infection was detected in kangaroos in Northern Territory in 2003.  Researchers investigating this infection thought that the local sandflies (Sergentomyia spp.) seemed highly unlikely vectors because they show a strong preference for feeding on reptiles. Indeed, screening for Leishmania in 3046 Sergentomyia sandflies yielded none infected with Leishmania. This led the researchers to expand the vectors tested. What they found was an unnamed species of day-feeding midge (Lasiohelea sp.) that was infected with a prevalence of up to 15 percent. This is the first identified vector for Leishmania that is not a phlebotomine sandfly. Not much is known about this midge.  The researchers were unable to find breeding sites, for example. The presence of prolegs on the midge larvae suggest that it is not aquatic but is terrestrial or semi-acquatic.  The authors suggest looking for midge breeding sites in the moist soil near water troughs where kangaroos drink.

Finding a totally new vector for a disease carries with it implications for eradication and control. One possibility raised by this work is that the difficulty some control programs have experienced may reflect the fact that Leishmania is being transmitted by multiple vectors. This is an hypothesis well worth investigating in areas other than Australia.

This work formed the basis of the Ph.D. dissertation for Annette Dougall at Charles Darwin University, Menzies School of Health Research.  Nice work, Annette!

Some Thoughts on the Fires Down Under

I recently received some comments on my post describing our PNAS paper from the end of 2008 in which we demonstrated that aboriginal burning increases grassland biodiversity.  The comments were very angry — and a little incoherent.  Clearly, emotions were (and are) running high in Aus following the the tragic bushfires in Victoria that have killed at least 181 people. An interesting, though rather vague, editorial appears in today’s The Australian in which foreign editor Greg Sheridan argues it’s time to get serious about preventing future tragedies of this kind.  He rightly notes that all the hysteria over global warming is of little practical consequence for managing wildfires. Global warming is, in my opinion, a reality and the best evidence we have suggests it is driven by human action.  Nonetheless, we can not attribute any one event, however dramatic, to global climate change.  Furthermore, blaming the fires on global warming does nothing to mitigate the effects of future fires (which are inevitable both in Aus and here in the American West). If anything, I fear that the linking of these fires to global warming disempowers people for action because they feel like they have no control over forces so much larger than themselves.

One of the comments on Sheridan’s editorial really struck me (and I thank Brian Codding for bringing this to my attention).  “Steve from Hobart” wrote quite eloquently on the topic (I have attempted to edit some of the characters that didn’t translate from Steve’s word processor to The Australian):

The call for controlled burning has long been sounded in this country without being seriously implemented by State and Commonwealth governments of either political persuasion. The Royal Commission after the 1939 fires clearly indicated that such land management practices should be diligently implemented — long before there were any “greenies”. Similar calls came after 1967 in Tasmania, 1983 in SA and Victoria, and more recently in NSW and certainly in Canberra. Conclusion: the inaction on implementation of a systematic, cyclical prescribed burning regime is not new, so be careful about laying the blame on any particular group. Issue 2.: controlled burns a threat to biodiversity??? Perhaps it might be if such burns are only carried out when the fuel load reaches ridiculous proportions, and/or it’s allowed to cover very large areas. Controlled burning is something that the ecology and biodiversity of this country thrives on, and it would appear that it has actually evolved to take advantage of a cyclical fire regime. Ask the indigenous people, they practised it for millennia. We need to make a serious effort to revisit that strategy, and not just on the urban fringe. We need to do the ecology and biodiversity of our magnificent and unique country a favour, and try to develop a modern-day fire-stick farming regime for our forests. Regular patchwork burning of smaller areas, repeated on a regular cyclical basis. And, in so doing, we’ll protect human life and property.

Well said, Steve!

Here, I will copy what I wrote in response to the heckling I received regarding my previous post because the points are, I think, worth emphasizing. I was responding to extreme skepticism that ecology had anything to do with fire control and that human agency has anything to do with ecology. Again, I will edit slightly.

The tragic fires currently devastating large tracts of Victoria actually highlight the need for carefully done fire ecology. The recent events in Australia dramatically underscore this as do the enormous wildfires that have beset us here in California and the American West more generally over the past decade. So far, we have not experienced the degree of human tragedy that you are seeing in Victoria, but I fear it is just a matter of time.

Following the classic definition by Andrewartha and Birch, ecology is the scientific study of the distribution and abundance of life. If human burning affects either the distribution or abundance of plant or animal species — which it certainly does — then it is the proper subject for ecological analysis. Furthermore, ignoring human agency in such a case would yield a trivial and incomplete ecology.

In our paper on the fire-stick farming hypothesis, we actually make no claims of relevance to contemporary problems. We are trying to understand the dynamics of this particular system. That said, I nonetheless think there are findings of policy relevance embodied in this work. Fire needs fuel and the fuel for wildfires is the vegetation in “wild” areas. As you note, there are no parts of the world untouched by human influence either directly or indirectly. By setting many, small, low-intensity fires through their subsistence hunting, the Martu alter the landscape and make it less flammable. In effect, the successional mosaic that arises from this practice creates a landscape of firebreaks. This is precisely what back-country fire-control teams do in battling wildfires. The Martu just do it preemptively.

How to manage highly flammable landscapes in more densely settled areas like coastal Australia and the American West is an enormous problem and I don’t claim to have the answers. However, ideas informed by landscape ecology are clearly part of the solution. Engineering human-dominated landscapes with greater structural heterogeneity seems essential for dealing with this emerging chronic problem of arid temperate and sub-tropical climates.

Doug Bird, Rebecca Bliege Bird and I are working on longer essay that addresses these vital problems of contemporary human ecology.  I will, no doubt, write about that again here soon.