That’s one of the reasons why the Hendra virus in Australia spread from bats to horses to humans: Bats used to live in forests where there are no horses, but we cut down those forests, and now the bats take refuge in other areas that bring them into closer contact with horses. So a lot of it’s not about necessarily controlling a disease in wildlife. It’s about being more conscientious about our impact on wildlife and when we’re encroaching on their habitats, and modifying our behaviors around them.
I know when SARS disappeared from the human population that some scientists did call it eradication, when in reality, viruses that are relatives of the SARS virus were still present in bats. A lot of it relates to semantics in some ways. The whole reason why pathogens are able to jump species relates to their evolutionary history, and they might evolve to acquire the ability to spill over into these new hosts. So whether or not you can say it’s been eradicated is debatable. Some people say, yes, that virus with that exact makeup has been eradicated. But on the other hand, the risks still exist, in my opinion, because you still have viruses that are potentially the precursor to another type of infection.
Romm: So when people talk about eradicating diseases, like with rabies, they're really talking about putting up a barrier between domesticated animals and humans?
Mor: Or between the wildlife and the livestock—decreasing contact between wildlife and livestock, and also reconsidering some of the ways in which we’re raising livestock. We’re now raising livestock in very densely populated conditions—feed lots, for instance—and this is why pigs are so important, because in many system they’re raised on contact with a large number of other pigs. Poultry is similar. In some ways it’s sort of the animal equivalent of a slum, and we all recognize on the human side that when you put lots of people together, that sort of condition is very conducive to transmission of infection. So when we put animals in that condition, that’s exactly what happens. The part about strategy, in addition to preventing contact between wildlife and domestic animal species, is also trying to determine how to better raise livestock in conditions that don’t favor disease transmission.
Romm: Among the zoonotic diseases you studied, what determines which ones get more attention than others?
Mor: One thing we found in our research was how much the perception of a problem was really driving the research. So in our paper we give two examples, one being avian influenza and one being bovine tuberculosis. In both cases, we have the perception that they have a large potential to cause harm to humans, and therefore there’s a lot of research investment.
But if we look back and think about the actual impact to animal health, production, and welfare, those two diseases are not quite so important. On the avian influenza side, there’s a lot of investment around wild-bird surveillance, even in very resource-poor countries that don’t have the best surveillance systems for a whole range of diseases that actually have more impact from an animal-health point of view, as well as from a human-health point of view. And yet the investment was on this perception of risk. So we need better ways in the future to identify and prioritize diseases based on actual risk to animal health and public health.