Why a decline in scavenger populations could impact human health : NPR

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Animals that eat carcasses from other animals may seem a little coarse. But a recent study shows that scales, such as vultures or hyenas, can actually be good for human health. Unfortunately, this same study shows that treasure populations are decreasing. Jonathan Lambert de NPR reports that this could mean more disease for humans.

Jonathan Lambert, byline: growing up in India, the environmental economist Annant Sudarshan remembers Vulture.

Annant Sudarshan: When I went to school, we crossed this river, and you have always seen these vultures in large quantities, partly because they feed on carcasses along the river.

Lambert: But in the mid -1990s, Vultures almost disappeared, decreasing by more than 95%. The culprit? An analgesic given to cattle that was just toxic to vultures. Millions less vultures meant many more carcasses. Sudarshan, now at the University of Warwick, published a study last year that had fatal implications for humans.

Sudarshan: We find a kind of important effects on the mortality of around 100,000 additional deaths per year and, above all, effects that are maintained for many years after the disappearance of the vulture.

Lambert: animal carcasses are foci of bacteria that can cause human diseases. Without vultures to choose them quickly, the rotten flesh rises. It can spread diseases by close contact or by rising in the water. And all this additional meat meant more calories for wild dogs, which increased in number. Here is Chinmay Sonawane, biologist in Stanford.

Chinmay Sonawane: millions of wild dogs, millions of additional people bitten by these dogs, and it is estimated that something like 50,000 additional people died of rage.

Lambert: In Sonawane, vultures illustrate the huge but often hidden advantages that the hinges offer. And it’s not just vultures. Researchers have found that African hyenas choose clean livestock carcasses that can spread anthrax, and chat type ceremonies in Malaysia can reduce bacteria causing diarrhea by rancing rancid meat.

Sonawane: In the last one, like about five years, there had been a burst of case studies by examining this relationship between recovery species and human health.

Lambert: Sonawane and his colleagues analyzed all these case studies and left with a disturbing image. They found that 36% of recovery species are down or threatened with extinction. Greater scavengers were particularly threatened.

Sonawane: When we lose this large fauna, the small fauna tends to replace them.

Lambert: The study, published in the journal Pnas last month, revealed that if these smaller tramps, such as rats or dogs, can pick up part of the soft, they are simply not as good for cleaning a carcass.

Sonawane: Therefore, there is more carcass waste, therefore more pathogens in the environment. And then, therefore, people are more likely to take the disease from these sources.

Lambert: People are also more likely to collect diseases of small scavengers themselves, which tend to transport more pathogens. Although there is still a lot to learn about the links between scavengers and specific diseases, the biologist of the University of Maastricht, Christopher O’Bryan, says that this study represents a good start.

Christopher O’Bryan: The message to take away is that we must always take into account nature in the human health equation. And we cannot ignore it.

Lambert: Indian Vultures offer an edifying story. Even after restricting the medication that sparked their decline, vultures have still not recovered. Jonathan Lambert, NPR News.

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