MEDICAL MATTERS:Homes experiencing an upsurge in infestations, writes MUIRIS HOUSTON
HOW WOULD you feel if someone close to you died from “surfet” or the “King’s Evil”? According to an exhibition at the Royal Society in London, these causes of death were relatively common in 17th-century Britain. Compiled in a 1662 work by pioneering statistician John Graunt, the now-strange diagnoses appeared in Bills of Mortality, official weekly lists of deaths in the City of London.
One poor unfortunate died from “itch”, which is most likely a reference to scabies, a skin infection caused by microbes burrowing under the skin. While still with us, the notion of someone dying from a scabies itch is difficult to comprehend some four centuries later.
But bugs, whether parasites, bacteria, viruses or fungi, are incredibly resilient. Take bedbugs as an example. Thought to have been around since the time of the Pharaohs, in the 1950s public health authorities in the US thought they had all but eradicated the common bedbug (Cimex lectularius).
However, as Dr Peter Hotez, president of the American Society of Tropical Medicine and Hygiene, observed last week: “Just as with other global diseases once thought under control and then neglected, bedbugs have shown the ability to resurge in great numbers once our vigilance wanes.”
He was speaking at the society’s annual scientific meeting in Philadelphia, which heard about research offering new insights into how the bugs infest apartment buildings and homes. While the main problem is their resistance to insecticides, it has emerged bedbugs enjoy a high level of inbreeding. Normally inbreeding in a species results in weaker offspring which are more likely to die young; in the case of the common bedbug, however, the opposite applies.
Researchers examined the genetics of bedbugs from three multi-story apartment buildings in North Carolina and New Jersey, and found high levels of relatedness within each apartment and very low genetic diversity within each building, indicating that infestations start from just one or two introductions of the insect. Being able to withstand a very high level of inbreeding allows the bedbug infestation to expand to other apartments.
A number of speakers said the massive upsurge in bedbug numbers was also the consequence of multiple repeated bug introductions from all over the world. In the past 10 years, the majority of humans have moved to urban areas, creating the perfect setting in the form of a high density of mammal nests for bedbugs. As one speaker noted, “bedbugs do not have wings; they are nest parasites, so our own population density has helped them to thrive”.
Previous studies have shown that turnover of residents is one of the biggest indicators for the presence of bedbugs and that increased domestic and international travel is one of the main factors driving bedbug infestations.
Bedbugs also feed on chickens, and industrial production of poultry is providing the perfect breeding grounds for them. But researchers also attribute the spread to the increased introduction of used furniture into homes.
In terms of treatment and control, research is now focusing on identifying and understanding the function of chemical compounds secreted by the pests. Scientists hope it might be possible to develop a trap with a “cocktail” of these bedbug compounds to attract the pests. And they are working to see if chemicals – newly identified on the bedbug’s outer skeleton – can enhance the ability of dogs, used by pest management professionals, to sniff out the microbes.
At present, bedbug infestations are treated with either insecticide or heat. Applying heat treatment involves heating the whole home, or packing all furniture and belongings in a box and heating the objects at a high temperature for one hour, but both are expensive options and not ideal for chronic infestations.
Meanwhile, back in 17th-century England, the “King’s Evil” was the moniker given to TB of the neck. As for “surfet”, let’s hope no one dies of “vomiting from overeating” this festive season.