Cockroach infestations can worsen allergies and asthma in children, especially in low-income urban homes. One particular species of cockroach is known to carry bacteria in their guts that release harmful substances called endotoxins into their droppings.
Researchers at North Carolina State University have now found that the more cockroaches there are in a home, the higher the levels of allergens and endotoxins. When pest control reduced the number of cockroaches, levels of these harmful substances also dropped significantly.
Indoor allergens can raise the risk of asthma and allergic reactions, especially in children. In inner-city homes, cockroach allergens are found in 85% of US residences, and up to 80% of children with asthma show sensitivity to these allergens in skin tests.
Cockroaches produce over 20 types of airborne allergens. Unlike other common allergens (like those from cats or dust mites), no single cockroach allergen dominates the immune response. In fact, about 1 in 5 people who react to cockroaches don’t respond to any of the known allergens. Scientists aren’t sure why, but it may be due to how cockroach allergens are spread, their stability, or their molecular makeup.
In this new study, researchers presented evidence that cockroaches don’t just scatter allergens as they scurry; they also leave behind bacterial toxins called endotoxins.
Think of endotoxins as microscopic smoke signals released when certain bacteria die. These invisible irritants float through the air and can trigger inflammation throughout the body. Breathing them in may lead to fever, headaches, wheezing, and irritation of the nose, throat, and lungs.
Cockroaches are not picky eaters, and their guts reflect it. Packed with a broad mix of microbes, their digestive systems churn out feces rich in endotoxins. While pets and people also shed endotoxins, this study found that cockroach droppings were a significant source of these toxins in household dust.
Conducted in North Carolina over two years, the study examined homes in low-income apartment communities, some with cockroach infestations, others without. Researchers compared estimated cockroach infestation sizes with allergen and endotoxin levels in cockroach-infested homes.
They found high levels of endotoxins in homes with cockroach infestations, especially from female cockroaches. Female cockroach droppings contained about 2,900 endotoxin units per milligram – more than twice the amount found in male droppings (1,400 EU/mg). On average, each female released around 5,000 endotoxin units per day in her feces, while each male released about 750 EU/day.
Co-corresponding author of the paper, Madhavi Kakumanu explained the unusual gender difference, “Female cockroaches eat more than males, so more endotoxins are shed from their fecal matter. More endotoxins were found in kitchens than in bedrooms, as more cockroaches live in kitchens where they find more food.”
Researchers then split cockroach-infested homes into two groups: one received pest control treatment, and the other did not. They also included a control group of homes with no cockroaches.
To track changes, they measured cockroach numbers and collected dust samples from floors and the air after three and six months. The findings were clear: homes with untreated infestations had consistently high levels of both allergens and endotoxins throughout the study.
In most cases, homes that received pest control successfully eliminated cockroaches and their allergens. These homes also showed a sharp drop in endotoxin levels, making the indoor environment much healthier.
“When you eliminate cockroaches, you eliminate their allergens,” added Coby Schal, co-corresponding author on the study. “Small decreases in cockroaches don’t lower allergen levels because the remaining live cockroaches deposit more allergens. Endotoxins significantly decreased in homes where cockroaches were eliminated. This paper shows that the cockroach is the most important depositor of endotoxin in infested homes.”
A little more work is needed to understand the implications of this finding. The researchers will now look to investigate the direct relationship between these endotoxins and asthma in mouse models.
The study is published in the Journal of Allergy and Clinical Immunology: Global.
Source: North Carolina State University
