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Citizen Scientist: You Gave Me Bed Bugs First

March 16, 2012

The Citizen Scientist is a segment aiming to communicate the latest science news to you. In surveys, Americans perpetually show an interest in science, yet display a lack of basic science knowledge. This lack of knowledge can lead people to make poor decisions about the education and health of themselves and their children. Lets understand more about the world around us.

Let me clear the air first: I do NOT have bed bugs. I mean I do, but I don’t. I very carefully work with them in a lab and they are under maximum security conditions. There is no chance of escape, no chance I will bring them home, and no chance anyone that meets me will get them (from me). So with that said lets get on to the research.

(c) Kevin Ulrich

In a paper published this month in Parasitology Research entitled Mitochondrial DNA and morphology show independent evolutionary histories of bedbug Cimex lectularius (Heteroptera: Cimicidae) on bats and humans (woah, what a mouthful), researchers attempted to figure out where bed bugs came from. When I say, “where they came from” I’m not talking about where the bed bugs in your friends apartment came from or even where the current scourge of bugs originated from. We’re talking further back, much further – like when we lived in caves.

The traditional theory is that we picked them up from bats when we shared caves in Africa. Following human’s migration to Europe, Asia, and beyond, the bugs tagged along. However, the same species of bed bug that plagues us is still found in bat roosts (and will feed on a bunch of other animals too).

The authors wanted to trace the evolutionary migration of bed bugs. So, how did they do this? First, they needed a lot of samples. Easy right, just go to any US city?  Well, if you want to compare the human bed bugs to bat bugs, we need to find bugs on both sets of hosts, from all over the world. 189 bed bug samples later, they were ready to do some data crunching.

First, they did morphological analysis. How? With lots of tiny rulers (kind of).  They measured legs, mouthparts, leg hairs, and a lot of other features. They used this data to see how human bed bugs and bat bed bugs changed appearances from each other over time (i.e. are bat bugs smaller, longer legged, have stronger sucking mouth parts?).

Second, they compared DNA. DNA is a long code that makes us who we are. Over time, this code can change in a population due to who’s doing the breeding, mutations, and other Darwinian-type stuff. Comparing the two different bed bugs, we can see how similar parts of that DNA code are. If the portion of DNAs are nearly identical that means human and bat bugs still breed with each other (meaning bats could still be giving us bed bugs and the bugs readily swap hosts). If the DNA codes are different, we can then determine how long ago these two pest sets separated from each other based on how much the code varies (i.e. when bat bed bugs stop breeding with human bed bugs).

(c) kevin ulrich

The researchers found that the DNA was very different. In fact, their estimates have the bed bug population diverging way before modern humans left Africa. It raises a possibility that modern humans acquired the bed bug from earlier inhabitants of the area, like the Homo neanderthalensis or Homo erectus. What’s more is that the time estimate of the split of bat- and human-associated bugs suggests that our human relatives gave the pest to European and Asian bats right after leaving Africa.

So here are your takeaways:

  1. Originally, it wasn’t bats that gave us bed bugs but probably us who gave it to them (and it was the Neanderthals that gave the bugs to us).
  2. Based on the difference is DNA codes, it’s unlikely that your friend’s bug infestation came from a bat nest in the attic – so don’t go around destroying bat roosting sites please.
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