SCIENCE

Bedbugs: scientists are close to winning the war

Chemicals found in insects' dung will be used against them in traps, writes Sunory Dutt

PUBLISHED : Monday, 09 February, 2015, 6:04am
UPDATED : Monday, 09 February, 2015, 6:04am

For five years Regine Gries welcomed 180,000 bedbug bites with open arms, quite literally. She was assisting her fellow biologist and husband Gerhard Gries at Simon Fraser University, Canada in his search to conquer the global bedbug epidemic.

Since Regine is immune to the bites and suffers just a slight rash instead of the ferocious itching and swelling most people suffer, she became the "host".

After years of research, the Gries, along with Robert Britton, a chemist at the university, and a team of students, have found the solution: a set of chemical attractants, or pheromones, that lure the bedbugs into traps and keep them there.

The Gries and their students initially found a pheromone blend that attracted bedbugs in lab experiments, but not in bedbug-infested flats.

After two years of false leads, they finally discovered that the molecule histamine signals "safe shelter" to bedbugs. Once in contact with histamine, the bedbugs stay put whether or not they have recently fed on a human host.

Yet, to everyone's disbelief, neither histamine alone, nor in combination with the previously identified pheromone components, effectively attracted and trapped bedbugs in infested flats.

So Regine began analysing airborne volatile compounds from bedbug faeces as an alternate source of the missing components.

Five months and 35 experiments later, she found three new volatiles previously unidentified for bedbugs. These three components, together with two components from their earlier research and, of course, histamine, became the highly effective lure they were seeking.

 

As of now, our prototype traps only trap - we are working on the 'kill' part
Marianne Hooper

They're now working with Victoria, Canada-based Contech Enterprises to develop a bait and trap for detecting and monitoring bedbug infestations. Marianne Hooper, director of innovation and engineering at Contech Enterprises says the trap containing the lure would be available in the next six to nine months.

It will be a small trap that can be placed between the mattresses of the bed or in close proximity to the bed, which are areas that bedbugs frequent.

Hooper says: "As of now, our prototype traps only trap - we are working on the 'kill' part as well. Our intent is for it to be very inexpensive, so as to be available for both commercial and household use. Initially, we will target the commercial market, but plan to follow up quickly with a retail product."

It will help landlords, tenants and pest-control professionals detect bedbug infestation at an early stage to treat it quickly as well as monitor the effectiveness of the treatment.

The biggest challenge today is finding how to attract bedbugs other than mimicking human conditions - which is by using carbon dioxide and heat. The most successful traps in the market use these along with a sort of sticky pad device that creates heat, has a carbon dioxide generator and a lure to draw in the bedbugs.

This works well and is used by pest controllers to monitor bedbug infestations after treatments. But since it mimics humans, when it's used in a room with occupants, it may not work due to competing sources.

Stuart Morton, manager technology and entomology, BioCycle (Hong Kong), says: "To have an attractant specific to bedbugs would be a distinct advantage. We have lures and traps using pheromones for a wide range of insects within the industry, but we do not have one for bedbugs.

"If we can solve this problem, we are a long way down the road to being able to detect and manage the problem," he says.

Contrary to popular belief, bedbugs do not only infest densely populated public housing estates. They also show up in expensive hotels and flats, and public venues such as stores and cinemas, and on public transport.

In Hong Kong, statistics provided by the Food and Environmental Hygiene Department show that the number of complaints of bedbugs decreased from 80 in 2013 to 33 in 2014.

The prevalence of these small, wingless, blood-sucking insects worldwide declined with the widespread use of DDT in the mid-20th century. But there seems to have been a recent resurgence around the globe.

International travel, more immigration, changes in pest control practices, and insecticide resistance may have contributed to the resurgence in developed countries, say researchers from the University of Mississippi Medical Centre, who published a report in the journal JAMA on the health and medical effects of bedbugs, and control and eradication strategies.

BioCycle says it receives between 10 to 15 bedbug inquiries a week during the summer, and an average of five to seven inquiries a week during the rest of the year.

Bedbugs are difficult to treat because they live and lay eggs in the cracks of bed frames and skirting panels on walls, and burrow inside mattresses. Most insecticides won't kill the eggs, which have a 14-day life cycle.

Eradicating them is a meticulous, labour intensive and time-consuming process that normally comprises three to four treatments conducted at weekly intervals. It involves the use of industrial type steaming equipment and insecticide application to cracks, crevices and perimeter areas.

It requires the participation of the home occupants, who have to clean up and pack and treat clothing and goods.

Bedbugs live only on human blood and tend to feed at night. Their bites can itch for days and cause rashes. But not everyone is affected by their bites. Like Regine, Morton also isn't bothered by them.

He even says he bred some by having them feed on his hand to keep them alive for testing.

There's the misconception that getting rid of the bed will get rid of the bug too. Throwing your mattress away changes nothing. Bedbugs not only infest mattresses, but also bed frames and any hiding place within a two-metre radius of the bed. They can be transported to other areas of the home and it is not uncommon to find them infesting sofas.

Morton recollects one case of bedbug infestation in a public housing estate where the situation was so bad that he had to tell them to demolish the entire interior and throw away all their furniture.

Scientists have recently discovered that these blood-sucking pests can transmit the pathogen that causes Chagas disease, which is prevalent in Central and South America. But there's no known evidence which shows that bedbugs are disease vectors.

That said, the Food and Environmental Hygiene Department has been closely monitoring the bedbug situation in Hong Kong and advises the public to maintain a clean domestic environment, clean premises regularly, wash bedding and clothing thoroughly, replace worn-out wallpapers, and seal cracks and crevices on walls and floors.

In addition to these guidelines, Morton cautions against taking in second-hand sofas and mattresses. If you do, he suggests treating them before bringing them into your home.

A lot of infestations are carried in luggage, too. Always quarantine your luggage when you return from a trip. Be very careful when you travel, as you could be bringing back more than you bargained for.

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