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    Scientists Placed Electric Cages over Dead Zebras to Study the Spread of Anthrax

    Written by

    Derek Mead


    Yes, that headline is serious. Via Steve Bellan

    Ecologists studying the spread of anthrax in wildlife populations have previously found that scavengers may play a role in its spread. By opening (eating) carcasses of animals killed by anthrax, scavengers thus allow anthrax spores to more easily spread throughout an environment while avoiding competition with the bacteria that cause decomposition, as studies have found. But according to a new study, that relationship may not be as strong as once thought.

    Anthrax is a disease caused by Bacillus anthracis bacteria, which persist in wild environments by creating tough-shelled endospores. Anthrax deaths of large herbivores, whether they be wild or livestock, are fairly common and well-studied. Essentially, grazing animals are susceptible to consuming anthrax spores that persist in soil.

    When an animal dies, the anthrax spores within its body can seep out into the soil, occasionally aided by scavengers, which completes that cycle. Anthrax outbreaks can be extremely costly for conservationists and wildlife managers, who sometimes focus efforts (and thus budgets) on preventing the spread of outbreaks by trying to prevent scavengers from eating infected carcasses.

    Mmm, tasty. Via Steve Bellan

    “The hypothesis is that when a carcass is intact, the anthrax bacteria are forced into a kind of death match with putrefying bacteria from the gastrointestinal tract,” lead author Steve Bellan of UT Austin said in a release. “But when the body is opened to the air, either by a scavenger or the hemorrhaging from all bodily orifices that occurs at death, the anthrax bacteria can escape that competition and more successfully produce spores.”

    The study, whose results are published in Applied and Environmental Microbiology, utilized pretty fascinating methods. Think for a second: How does one test whether or not scavengers help spread disease? Why, by finding some carcasses and preventing half of them from being scavenged, of course. 

    In this case, the research team found seven zebra and one wildebeest that had died of anthrax in Etosha National Park in northern Namibia. Without moving any of them, the team placed electrified cages over four of the carcasses to prevent scavenging, while leaving the others be to be nibbled on by scavengers, which include hyenas, jackals, vultures and even  the enormous Maribou stork. (If you're wondering, all four of the previous have been studied to show some degree of anthrax resistance, but they're not totally immune.)

    Vultures going hog-wild at an anthrax buffet. Via Steve Bellan

    I'd be remiss if I didn't note that such a small data set isn't conclusive, especially with a fairly large body of work published in this area. Regardless, the team found that anthrax spore production was similar in the control and experimental groups, which suggests that anthrax spores can survive in a dead carcass even as it's decomposing, and then can still escape without a scavenger's help.

    So while it's not conclusive, the study does suggest that focusing management efforts on preventing scavengers from eating anthrax-infected carcasses may not be beneficial enough to spend time and money on. At the very least, the study suggests that the practice needs more study to determine if it really is worthwhile. Regardless, it's not every day that you see a dead zebra in an electric cage.