The Unexpected Link Between Bed Bugs and Malaria

“How do you eat an elephant?” I vividly remember this question being posed by my professor in a graduate level global health course during my time at Duke University. I also vividly remember my internal sarcastic response — “one bite at a time.” I had heard this saying for much of my life, and typically it just frustrated me. Big problems were just that, BIG, and of course they take time and multiple “bites” to solve them. Little did I understand that this old adage would soon guide the next six years of my life, and despite my sarcasm, I would learn that each of those “bites” was harder than the previous ones.

It was a few weeks following this lecture that I landed in my project and was partnered with my mentor. Suddenly, a new elephant was put in front of me, one that at first glance looked just like others I had seen in my life. Malaria. A disease nearly as old as time, found in humans and many animals alike, and that to this day is re-sponsible for over half a million deaths per year — mostly in children. At one point it was found globally, including in the Unit-ed States, and is a disease that thrives in war and poverty.

Human malaria begins following infection with tiny Plasmodium parasites from the bite of an infected Anopheles mosquito vector. Once inside of your body, the tiny parasites travel to your liver, then into your bloodstream where they weaponize your red blood cells against you. Each infected cell becomes a factory, producing new malaria parasites until it is bulging like an over-filled balloon. These cells rupture simultaneously, fevers and chills follow, and if it makes its way to your brain … death is a possibility. Even today, malaria claims more than 600,000 lives annually. This was my new “elephant.” A REALLY big elephant.

My first “bite” was to help develop and lead a mosquito monitoring and identification program in rural Myanmar (Burma) — an area of ongoing military conflict. I spent two years chewing on this project. Two years trying to finish this bite. In the end, I wasn’t satisfied. The elephant was still huge, looming, and every year lives were lost. I wanted more bites, more chances to have an impact.

I found my chance in an unsuspecting place, or rather an unsuspecting pest, the bed bug.

THE SURPRISING ENEMY. Bed bugs are part of the human experience. From metros in Paris to hotels in New York, these tiny insects have made their home within some of the most intimate spaces of our lives. These tenacious and highly resistant pests are small, brown in color and feed on only a single thing their entire lives — blood. Within the structural pest management industry, they can be some of the most challenging accounts to handle. They are cryptic. They are resistant. They are a headache.

But what do they have to do with malaria control? Its simple — beds. I learned during my work that the primary method for disrupting malaria transmission is through the deployment and use of long lasting pesticide treated nets (LLINs). Years ago, nets were woven and then dipped in pre-mixed pesticides, impregnating them, but requiring retreatment periodically. Thanks to modern technology, these nets are now woven with pesticide-impregnated materials, increasing their durability, and helping remove the human error component. This intervention was so successful that their use has been relied upon globally since the early 2000s, and they are credited with saving hundreds of millions of lives. Despite this success, initial uptake was rocky.

Many communities already struggling with poverty were tasked with purchasing and maintaining the nets out of their own pocket. This took precious resources away from family, food and futures — at least it felt that way. So what was the golden ticket that made it worth the cost? Well, put simply, evidence shows that early on, communities actually valued the use of LLINs for controlling urban pests like bed bugs and cockroaches beyond their use for disease prevention. After all … no one wants to sleep with bed bugs.

As the years went by, the uptake of LLINs continued, and communities began to see the generational value of reducing and preventing malaria transmission. As with any pesticide, resistance from overuse followed quickly, and the arms race against pesticide resistant malaria mosquitoes continues to this day. However, that isn’t the bite of the elephant that this story is concerned with. Instead, lets focus on what happened with the crawling insects — especially those bed bugs that make their home and livelihood where we lay our heads at night.

Fast forward just over a decade and reports of LLIN abandonment begin to surface in the literature. Whispers have begun to spread, and communities have begun to make a horrible association — where LLINs have been used for a long time, bed bugs are increasing in numbers. They aren’t dying like they used to, and the easiest culprit to blame are the life-saving LLINs that controlled them for so long. Put bluntly, people began believing that LLINs were making their bed bugs worse. That’s impossible though … right?

Certainly LLINs are designed to target mosquitoes — flying blood suckers that land on the fabric as they struggle to reach you, absorbing the pesticide through their cuticle and meeting a grisly demise. But when used correctly, the net should be tucked under the mattress on all sides, directly into favored aggregations of bed bugs. Researchers didn’t know what was at work.

Call it Schrödinger’s bed bug if you will.

Bed bugs in these spaces could be living directly on and within the LLINs, with easy access to the host, but returning to aggregate on the fabric. They could be harboring outside of the LLIN and confront the unexpected barrier as they approach for their midnight snack; unable to fly to another host, they must attempt to navigate it or risk starving to death. In both of these scenarios there remained questions: Could bed bugs actually fit through these nets? Would bed bugs actually attempt to navigate a pesticide-impregnated material? Should bed bug pesticide resistance be considered in the development of future LLINs?

These were all valid and essential questions, and each one was massive bite of the elephant that is malaria. So I started chewing.

FACING THE ELEPHANT. We decided to run a series of behavioral assays to see if bed bugs of various life stages, pesticide resistance profiles and feeding status were able to navigate some of the most widely distributed LLINs in search of a bloodmeal and an aggregation. When given only an hour to pass through and feed, we saw an average success of ≥60% across all life stages, but <30% mortality even in the best-case scenario. This is the perfect storm for developing pesticide resistance.

Surely though, especially since these LLINs contained pyrethroids, if given the choice to pursue a host away from pesticides they would prefer that route. After all, what good is dinner if it kills you?

To test this theory we took bed bugs and placed them into a vertical y-shaped glass tube, with air flowing from the top downward. We would place host odors on both sides of the “Y” — I swabbed my arms and legs a lot for this project — along with supplied CO2. Finally, we would pass the air in one arm of the “Y” over large pieces of the LLIN we were testing, collecting the volatilized pyrethroids and in theory repelling the bed bugs from that host. Only a single panel (the roof) of a single LLIN worked. Otherwise, they didn’t care! The bed bugs were just as likely to feed on someone sleeping under an LLIN as they were someone sleeping out in the open. The pesticides didn’t stop them.

They say what doesn’t kill you makes you stronger, and by this point we certainly hadn’t been able to kill 100% of bed bugs using the LLINs we had. So we brought out the big guns. We used the latest in LLIN technology and decided to leave the bed bugs trapped on the nets until they died … or until I got tired of coming in and checking them. If you’re reading this and you’ve ever dealt with pesticide-resistant bed bugs, you know what came first. In our field-collected bed bugs, we were only able to kill 80% after 96 hours of continuous and uninterrupted exposure to LLINs containing a pyrethroid + PBO combination. This section of the LLIN was on the roof, functionally out of reach for most bed bugs in the field, but still woefully ineffective. Despite my best efforts, and the best LLIN technology out there, the bed bugs weren’t going anywhere.

So, what did I take away from this? Are LLINs useless? Certainly not! Instead, I took away the fact that the biggest elephants in the world are often the most complex. Even if my plan is to eat that elephant one bite at a time, not all bites are easy to chew, and sometimes the bite is too big. Bed bugs are a challenging pest to eliminate even in the best conditions, and when resources are limited and patience is thin, communities rely on what they have in hand. This is the reality in malaria- endemic regions of the world, and while my work sheds a depressing light on the current status, it also serves as a call to action. More must be done to better understand the origins of bed bug pesticide resistance and its impact on a global scale. While my work alone doesn’t stand as the cure for malaria I can move forward knowing that I have joined countless others who have taken their own bite out of this massive elephant.

Today, malaria control efforts continue, and LLIN distributions save millions of lives each year. They endure despite the resurgence and persistence of urban pests like bed bugs and cockroaches that have the potential to derail these life saving programs. Similarly, you persist in your day-to-day battles with pests infesting structures and impacting livelihood. It could be an account overrun with German cockroaches, a property riddled with fire ants, or a persistent and complex rodent infestation — each of these standing as an elephant in its own right. So, how do we beat them? How do we get ahead of the enemy? How do we continue to help people?

Well, I’ll leave you with what I was asked years ago in that classroom, unaware of how impactful it would be in my own life. How do you eat an elephant? One bite at a time.

How do you tackle the largest challenges in your career? One bite at a time. So get chewing!

The author is a Ph.D., and urban extension entomologist at North Carolina State University.