A few weeks ago, I went spelunking for the first time. Since then, I’ve had bats on the brain! And that means that for a few weeks, Parasite Ecology is going to be all bats, all the time.
In a previous post, I discussed potential characteristics of bats that might make them “good” at “sharing” novel viruses with humans. There are many hypotheses out there, and probably all of the proposed important bat characteristics play a role for spillover of some viruses in some places at some times. There’s still a lot of research that needs to be done there, so investing in bat research is still a high priority. For today, we’ll just talk about one characteristic: for whatever reason, bats are hosts for a huge diversity of viruses, so there are a lot of viruses for them to potentially transmit to humans.
Even if bats are highly likely to share novel viruses with human populations, that sharing could never happen if bats and humans didn’t directly or indirectly interact. Therefore, there are also lots of hypotheses out there about which anthropogenic activities lead to high rates of interaction between humans and bats. For instance, areas with many people, areas with many domesticated animals that interact with bats and people, and areas where people are particularly likely to encounter bats (e.g., by eating them as bushmeat) might be especially likely to experience spillover of bat viruses into human population.
So, wouldn’t it be awesome if we had a map that showed where these drivers of bat virus spillover were particularly prominent, so that we could predict areas where spillover is most likely to occur? Why yes, yes it would be awesome. And just such a map was recently created by Brierley et al. (2016).
Here’s the just of it: using spatial regression techniques, Brierley et al. (2016) came up with a list of drivers that were good at predicting the total number of viruses shared between humans and bats in 1 decimal degree-sized grid blocks all over the world. They found that bat host diversity and annual rainfall were important drivers, and they suggested that these were links between virus diversity and the potential for virus spillover. They also found that things like human population sizes, the number of domesticated pigs, and the use of bats as bushmeat were important drivers, suggesting that anthropogenic activities are also important to spillover.
Interestingly, the areas where risk is high due to the high diversity of bat viruses (South America) are not the same as the areas where the risk is high due to high human-bat interaction rates (Sub-Saharan Africa). This suggests that when we think about preventing spillover of bat viruses into human populations, we probably need different plans for regions with different drivers. That’s not necessarily a new idea, but now we have a great map to show us which areas need which kinds of prevention!
This cartoon is not intended for people eating bats because they have few sources of protein in their lives. Obviously, eating bats isn’t a decision for them, it’s a necessity. But those of us in positions of relative power can work towards alleviating the socioeconomic situations that push people towards the consumption of bushmeat. And if you do have a choice, don’t eat bats!!
Brierley, L., M.J. Vonhof, K.J. Olival, P. Daszak, and K.E. Jones. 2016. Quantifying global drivers of zoonotic bat viruses: a process-based perspective. The American Naturalist.