Zoonosis — a word of the future

When a pathogen leaps from some nonhuman animal into a person, and succeeds there in making trouble, the result is what’s known as zoonosois. It’s a word of the future.

Deadly Contact — How Humans and Animals Exchange Disease’, 
National Geographic, October 2007

Too many words have been written about flying foxes, horses and the Hendra Virus for me to add many more about the whole thing here. This is a serious issue, and while I like humans, I also like flying foxes. They are interesting, important animals. Unfortunately the voices of reason and research have been largely buried by dodgy reporting and public ignorance — about the virus and about flying foxes. One thing seems clear — flying foxes, which carry the Hendra Virus and somehow transmit it to horses, from where it is passed on to humans, are in trouble.

Four species of flying-fox are native to mainland Australia. The Little Red (left) and the Grey-headed (right) are two of those found in south-east Queensland. Flying foxes make a significant contribution to maintaining healthy ecosystems as essential pollinators and seed dispersers for native forests. Our eucalypt woodlands rely heavily on these pollinators, producing most of their nectar and pollen at night to coincide with the time when bats are active. Photos  (left – Gatton, right – Allora) R. Ashdown.

There has been little information in the media about the link between human-caused disruption of ecosystems and the emergence of zoonotoc diseases, despite ongoing research overseas and in Australia. Flying foxes are mammals whose ecology has been greatly affected by human impacts on the environment, and this has almost certainly been a link in the emergence of this disease. The National Geographic article from which the quote at the start of this post was sourced gives an excellent look at the complex and poorly understood history of the transfer of viruses between humans and non-human animals. This is too important an issue for people to be mindlessly calling for the destruction of wildlife without looking at the big picture — which includes why these diseases are occurring and how our impacts on the environment are part of the cause.

If you’ve read this far you’re probably a wildlife-person, so it’ll be no surprise if I say that culling flying foxes is probably not going to help.

Although Hendra virus infection occurs naturally in flying foxes, these animals should not be targeted for culling. Flying foxes are protected species and are critical to our environment, as they pollinate our native trees and spread seeds. Without flying foxes, we wouldn’t have our eucalypt forests, rainforests and melaleucas. Any unauthorised attempt to disturb flying fox colonies is illegal. Disturbing flying fox colonies to reduce the risk of Hendra virus transmission to horses is ineffective because:

  • flying foxes are widespread in Australia and are highly mobile
  • there are more effective steps people can take to reduce the risk of Hendra virus infection in horses and in people
  • attempts to disturb or cull flying foxes could worsen the problem by stressing them and potentially causing Hendra virus excretion.

Department of Primary Industries and Fisheries

This is part of a larger story for all of us  — for humans and for other species of life.

Our safety, our health, isn’t the only issue. Another thing that is worth remembering is that disease can go both ways: from humans to other species as well as from them to us. Measles, polio, scabies, influenza , tuberculosis and other human diseases are considered threats to non-human primates. Any of them might be carried by a tourist, a researcher, or local person, with potentially devastating impacts on a tiny, isolated population of great apes with a relatively small gene pool, such as the mountain gorillas of Rwanda or the chimps of Gombe.

That’s why the Wildlife Conservation Society label their program with the slogan “One World, One Health.” The guiding principles come from ecology, of which human and veterinarian medicine are merely sub-disciplines. “It’s not about wildlife or human health”,  Billy Karesh told me. “There’s really just one health” — the health and balance of ecosystems throughout the planet. 

Deadly Contact — How Humans and Animals Exchange Disease’, 
National Geographic, October 2007

 

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