No Tropical Vacation

By Kierra Sondereker

At NPMA PestWorld 2017 in Baltimore, researchers from the University of Florida discussed how consumers and PMPs, especially those living and working in warmer regions of the United States, now may have to deal with two species of bed bugs. University of Florida researchers recently discovered tropical bed bugs (Cimex hemipterus) on the eastern coast of Florida. At PestWorld, they reviewed how these pests could lead to changes in how humans deal with bed bugs, including how PCOs manage and control them.

HISTORY. The common and tropical bed bugs are the two primary bed bug species that feed on humans, and both are distributed globally. Tropical bed bugs, however, prefer warmer climates. Documentation from the 1960s showed that tropical bed bugs were almost exclusively found in areas 30 degrees north and south of the equator.

“But then again, most of this was done before we heated and air conditioned buildings,” said Brittany Campbell, staff entomologist for the National Pest Management Association (NPMA) and University of Florida doctoral student. “So, we have no idea how far the spread of the tropical bed bug will be.”

Earlier, in the 1930s and ’40s, the first record of tropical bed bugs in the United States occurred when entomology professors from the University of Florida had students studying entomology collect bed bug samples. The tropical bed bugs collected came from five different areas throughout Florida. “We know we had tropical bed bugs back then; what we don’t know now is if they disappeared completely,” said Campbell.

While tropical bed bugs went undetected for more than 60 years, the pests were rediscovered in Florida in 2015 by the University of Florida’s research team.

RECURRENCE. In 2015, Dr. Phil Koehler’s team received a sample of bed bugs at their University of Florida lab. “Instantly I knew these bugs looked different than the common bed bug I was accustomed to,” said Campbell.

The sample came from a house located in Brevard County. Upon closer examination, the researchers realized they had a sample of tropical bed bugs, a species that hadn’t been seen for decades. “We wanted to share this to raise awareness of this new bed bug species that had been reintroduced into the state of Florida,” said Campbell, who began writing a paper on the subject in 2016.

She contacted pest control firms operating throughout Florida to see if they had any recent experiences with

tropical bed bugs. She received around 50 samples of beg bugs from Florida-based pest control companies. After examining them all, the research group determined that only the original sample from Brevard County contained tropical bed bugs.

During this time, Campbell’s research and the revelation of a new bed bug species began to receive national media attention. “It wasn’t surprising, because as soon as you start talking about bed bugs and a new invasive species that can be reintroduced, or potentially was already in small populations in Florida, it gets a lot of attention because bed bugs tend to freak people out,” said Campbell. “There were a lot of crazy stories that said they could spread more quickly and reproduce at really fast rates; there were some crazy numbers out there. But that’s actually not something to be alarmed about. We don’t really see this species reproducing any more quickly than any other species.”

However, Campbell’s research revealed that tropical bed bugs could potentially spread to parts of Texas, Louisiana and all of Florida. All these areas fall within 20 to 30 degrees north of the equator. “I don’t think it’s something that we should necessarily be alarmed about,” said Campbell. “I just want to make (PMPs) aware that there is this species. Currently, they don’t seem to be dominant in the state of Florida.”

STUDY. After receiving the sample of tropical bed bugs, Koehler’s team visited the home where the pests were found. The team took several live samples back to their lab for testing.

“We wanted to establish a tropical bed bug colony, so we could begin to conduct research on this species,” said Campbell. “In the United States, we really haven’t done a lot of research. In other tropical areas, some research has been done with tropical bed bugs, but there’s still a lot of unknown research about this species.”

Campbell and other team members collected eight bed bugs that day and began growing a colony of tropical bed bugs in the lab. “I would say, by now, we have thousands of tropical bed bugs in our lab at the University of Florida,” she said.

One of the primary goals of breeding this colony was to determine whether tropical bed bugs could hybridize with common bed bugs. But first, Campbell wanted to devise an easy way to tell the difference between the two species.

While one major difference is that tropical bed bugs are often darker in color, Campbell said this couldn’t be a true identifier because all bed bugs become darker in color after feeding.

“The body part you’re really going to focus on is the pronotum,” Campbell said. The pronotum is located behind the head and can be roughly referred to as the bed bug’s “neck.” Campbell notes the common bed bug has a much more pronounced and U-shaped pronotum than the tropical bed bug. However, she added that unless you view these bed bugs under a microscope, you would have a hard time telling them apart.

Campbell then took measurements of each species, looking for a measurement that would be different enough to act as a distinguishing characteristic. She discovered that tropical bed bugs are often smaller in size for both males and females compared to the common species. The pronotum of tropical bed bugs is also much smaller in almost every life cycle stage.

Once the size differences were determined, the team went back to see if tropical and common bed bugs could breed and create a hybrid species. In their University of Florida lab, they attempted to mate the two. Campbell said that hasn’t happened yet, however, and it appears that they may never be able to because of genetic variances between the species.

“The tropical bed bug species that we have, if we look at their DNA, they are very different,” said Campbell. “There are basically 47 different steps genetically between the different species, showing that these are two entirely different species.”

TREATMENT OPTIONS. Campbell’s next step was to find a way to control and eliminate tropical bed bugs using insect growth regulators (IGRs). She decided to test the bed bugs against two different chitin synthesis inhibitors (CSIs), which affect the molting process and the formation of chitin in the exoskeleton. She tested novaluron and lufenuron by applying a small amount to the abdomen of individual tropical bed bugs.

She added, “Another result that I saw was the sublethal effect. Sometimes the CSIs would not outright kill the bed bugs, but they would prevent the bed bugs from being able to walk well. The bed bugs that were treated with the CSI could not even grip a surface. If a bed bug can’t walk in someone’s home, they can’t go host searching and ultimately they can’t reach a host to take a blood meal. That’s going to be just as important as killing these bed bugs.”

TREATMENT VS. PREVENTION. With the reemergence of the tropical bed bug, Koehler said PCOs need to make a clear distinction between bed bug guarantees and warranties. He said companies should offer two different services: one for bed bug elimination, which would come with a guarantee that your service will eliminate bed bugs for a set period of time, and another prevention service with a legally binding warranty saying that if re-infestation occurs over a set period of time, the company will compensate the customer with no cost to the buyer.

“I’m kind of challenging the industry to take a look at two different services instead of one, which is not just an elimination service, but also a prevention service,” Koehler said. “Each service would use different methods, be invoiced separately or be invoiced together as a package when you do the process.”

Koehler compared bed bug IPM to a food pyramid. The top features food that should be eaten minimally, while the bottom contains what should be eaten most often. “Bed bug education and prevention should be at the bottom of the pyramid and treatment or elimination of bed bugs from people’s homes should be the least amount of work that you do,” he said. “Right now, the pyramid is inverted. Most of what you do is treatment and elimination and there’s very little prevention that’s part of your program. And we’ve been backwards on that for most of the bed bug work that’s been done in the past 10 years or so.”

He added, “You have to remember that times are changing. Bed bug IPM can be put together for your company to really profit from being able to sell a service to all of your customers, not just the ones that need a treatment or elimination. It’s going to be based on prevention.”

The author is an Ohio-based writer.