VCU news

By Madeline Reinsel

Nothing strikes fear into the hearts of home dwellers and hotel guests quite like the bedbug. The tiny, blood-sucking pests are notoriously difficult to exterminate, competing with cockroaches, mice and lice for the title of humanity’s least favorite roommate.

But when did the bedbug’s bite truly become entwined with our hope to sleep tight?

While bedbugs have been feeding on humanity since time immemorial, they’ve largely been haunting our nightmares for just the last 13,000 years or so, according to new research led in part by Virginia Commonwealth University Life Sciences professor Brian Verrelli, Ph.D.

That’s because humans first moved into cities around that time, giving bedbugs an opportunity to thrive in their new, closer quarters, according to the new research. That could make bedbugs the earliest known urban pest, whose rise has tracked the movements of our species over millennia.

Verrelli, who is part of VCU’s Center for Biological Data Science, worked on the study with colleagues from Virginia Tech, including his former doctoral student and lead author, Lindsay Miles, Ph.D., as well as senior author Warren Booth, Ph.D. VCU News spoke with Verrelli to find out more about the origins of what may be humanity’s oldest nuisance.

What are bedbugs, and where did they come from?

The bedbug is a small, flightless insect that feeds exclusively on blood for its nutrition and primarily uses humans as its host. It comes from an insect group that is composed of over 100 species that first appeared over 100 million years ago. The bedbug is most closely related to the “bat bug,” which is a lineage of the insect that uses bats as its host. Based on genetic evidence, it is believed that the bat bug lineage is the ancestral one, from which the bedbug lineage sprang about 245,000 years ago.

What caused bedbugs to jump from bats to humans?

Our early human ancestors likely shared caves and other dwellings that bats also inhabited. In those close quarters, these bat bug insects successfully jumped to humans as a new host over time. We know from genetic and other data that bedbugs today have multiple differences that have enabled them to adapt well to humans as their host, so much so that the bedbug species is now specifically adapted to humans over bats.

Why did bedbug populations surge when humans moved into cities?

Bedbugs had become well-adapted to their hosts by this time (having made the jump to human ancestors over 245,000 years ago), so once humans started moving around and adapting to different environments, the bedbugs went with them. Since we see that bedbugs sustained this close relationship with modern humans during this entire time, it means that this global dispersal was successful for them – the bedbug lineage did not “die out” or jump to another host.

How did you trace bedbug populations back over thousands of years?

We used a sample of modern-day bedbug populations, analyzed their genome sequences and built “family trees” of them – just like how we can compare human DNA today to figure out who is most closely related to whom. Bedbug genomes hold their historical family relationships, too.

We simulated many different bedbug population scenarios and looked at what the patterns of genetic diversity were in those simulated family trees. Then we estimated the bedbug family tree from the genetic data that we collected, and compared the observed and simulated patterns to see which simulated scenario, and thus history, the current bedbug population most closely matched.

What did your study find?

When we compared the genetic patterns in the observed bedbug population with the simulated populations, we found that the pattern most resembled a history where the bedbug population underwent a rapid increase in size about 13,000 years ago to get to where it is today. This timing is coincident with the timing of humans expanding their populations geographically into what most have called the first cities in our history.

Given we know that bedbugs have been associated with human ancestors for over 200,000 years prior to this time, it makes sense that when the human population expanded, so did the bedbug population. This is very interesting, as it supports the idea that once bedbugs had become well-adapted to humans, they then stayed with them and continued this long relationship that now mirrors what humans did over time. 

Could this research change how we combat bedbugs in our modern lives?

Through other studies of pest genomes, we have learned what genes and different biological pathways have changed over time to help pests better adapt to humans and city environments, including traits like insecticide resistance. With this study, we can now also understand when these genes and pathways evolved, which helps us figure out how better to coexist with them.

Unlike other fleeting relationships that humans have with our natural world – such as viral infections or pest invasion – we can instead design long-term behavioral and pest resistance strategies to help us coexist for the long haul.