There are plenty of reasons to hate bed bugs. These parasitic insects pop up unexpectedly in even the cleanest locations, are tough to get rid of and have a voracious appetite for human blood.
New research suggests another reason to hate these members of the cimicid family: the large amounts of histamine they defecate pose a medically important threat.
The research shows that histamine levels are about 20 times higher in homes infested with bed bugs compared with pest-free abodes. The study results also show that treating the infested homes with heat and insecticides did not decrease histamine levels — even three months after treatment.
Bed bug dust contains large amounts of histamines. Produced by basophils, histamine is part of the immune system and serves as the major mediator of the acute inflammatory and immediate hypersensitivity responses.
Histamines can have a deleterious effect on human health, though. Contact exposure to histamines can cause skin rashes, for example, and inhalation of histamines can cause respiratory problems. The response to histamines is so reliable that it is used as a positive control in allergy skin testing.
According to the National Pest Management Association, the top three locations for bed bugs are:
Apartments and condominiums
Hotels and motels
Bed bugs also commonly take up residence in college dorms, schools, offices, daycare centers and even in public transportation. The pests also frequently infest medical institutions, such as nursing homes and hospitals.
Roughly 1 in 5 Americans has suffered a bed bug infestation in their homes or they know of someone who has encountered them.
Researchers from North Carolina State University collected bed bug dust in 140 apartments located within a single nine-story, multi-unit building in Raleigh, North Carolina. The building had been plagued with infestation for several years, despite pest control efforts. The scientists analyzed the homes for histamine before bug eradication and again three months later.
The researchers acknowledge that some of the seemingly uninfested residences could have been infested with bed bugs in the past, and that some apartments may have had too few bed bugs to detect. The investigators offset these limitations by sampling five additional homes in Raleigh that were not associated with the apartment building to serve as external negative controls.
The scientists divided the homes into groups according to infestation status. In all, 14 units had bed bugs, 10 units did not have bed bugs, and five were negative controls. The researchers further divided the group infested with bed bugs into treatment groups: infested-control and infested-treated.
Intervention included chemical and heat treatments. The homes remained occupied during the study.
The investigators sampled the infested-treated homes at baseline and at 2, 4 and 12 weeks after the intervention. They found that histamine levels in bug-infested homes were at least 20 times higher than in units without bed bugs.
Bed bug-infested homes averaged more than 54 μg histamine/100 mg dust. Histamine levels in control uninfested homes in the same building averaged less than 2.5 μg/100 mg of dust; levels in uninfested sample homes in Raleigh were less than 0.3 μg/100 mg of dust.
The researchers also found that the levels did not decrease appreciably three months after treatment.
"A combination of heat treatment to eradicate bed bugs and rigorous cleaning to eliminate some of the household dust could be a way to reduce these histamine levels; we'll do future testing to bear that out," said NC State post-doctoral researcher Zachary DeVries and lead author of the study. "We'll also further investigate the effects of histamine in an indoor environment, including chronic exposure to histamine at low levels."