Cockroaches & Allergies: The Clinical Connection

An important correlation has been established between cockroach infestations. Meanwhile the pest control industry, working in tandem with other industries, is well-equipped to provide solutions.

Cockroaches are considered pests in the urban environment for several reasons. For one, they are annoying. They can transmit diseases when crawling on food or over kitchen counters. People don’t want to become exposed to the pesticides used to control them. And, we now know, cockroaches are one of the most important causes of allergies, including allergic asthma, especially in children.

Allergic disease is now recognized as a major health problem in the United States. A recent review of arthropod allergens in the urban environment, as well as results from a pilot study on environmental conditions in the home, shows that in the United States, allergic disease affects about 37 million people, or about 17% of the population. Overall, asthma occurs in about 3% of the population (3 million people), and both the frequency and severity of asthma episodes has risen steadily during the past 25 years. In fact, annual deaths from asthma have been rising since the 1970s.

Asthma is the most frequent reason for emergency room visits in children: Three million children under the age of 15 have asthma, another 6 to 9 million have allergic rhinitis (chronic runny nose), and another 2 million have atopic dermititis (skin rashes).

INSECTS AND ALLERGIES.Insects and other arthropods are a very important element in allergic diseases in the urban environment. House dust mites are constant nuisances because of their rapid spread and resistance to extermination. But in many homes, particles originating from cockroaches make up the bulk of the dust. These particles may come from cockroach feces, shed skins, oral secretions, egg cases and body parts of dead cockroaches. And exposure to cockroach allergens can result from ingestion, by eating food exposed to cockroach feeding activities overnight, or by using dishes contaminated with cockroach feces. Exposure may also occur from dermal contact; and by inhaling aerosolized cockroach allergens.

Cockroach allergens in house dust or in the house air are said to be "aerosolized." In a 1993 U.S.D.A. experiment by R.M. Helm, Wesley Burks, Larry W. Williams, David E. Milne and R.J. Brenner, the air from containers of German and American cockroach colonies was filtered through membranes to collect aerosolized cockroach materials. The researchers learned that the molecules collected were acidic proteins, although they were not identified further. These proteins do not degrade quickly and remain in the house for long periods, which can exacerbate the symptoms of allergic individuals. In fact, significant levels of cockroach "aero-allergens" have been found in homes in which no visible evidence of infestation was found. Laboratory studies indicate that cast skins are the most important source of the clinically relevant allergens that affect sensitive individuals.

THE COST OF ALLERGIC ILLNESS. Allergic consequences range in severity from irritating to life threatening. Allergies, in general, result in huge economic losses in the United States, costing billions of dollars per year. Costs arise either directly, from the purchase of medications, medical visits, and hospitalizations, and indirectly, due to lost work time. An important goal of research, therefore, is to help prevent the development of cockroach allergy, especially because developing allergy to one species of cockroach may result in cross-reaction to other cockroach species. Researchers have found that individuals sensitive to the German cockroach are also sensitive to the Asian cockroach, and also that chemical extracts from the American and Oriental cockroaches elicit similar allergic reactions, although to a lesser extent, to those elicited by extracts of the Asian cockroach.

Unfortunately, allergy to cockroaches within the United States is becoming more common due to the construction of more insulated and air tight houses, which are attractive to cockroaches, as air drafts dessicate them. These allergies are more frequent and severe in low-income housing due to high level of infestations, primarily of German cockroaches. The infestations are usually the result of improper garbage disposal plus the availability of food for the insects on places such as stoves and sinks.

Allergies to cockroaches also occur in higher income homes, which are characterized by low outdoor air flow through the house which allows the accumulation of airborne allergens. Also, central heating and cooling systems tend to recirculate the allergens; and wall-to-wall carpeting captures the allergenic particles or molecules, not only of cockroaches, but of other bugs and of molds, dogs and cats.

Health hazards associated with exposure to cockroaches may be reduced by limiting contact with them, which can best be accomplished through a combination of improved house design, novel pest control methods, increased sanitation, the use of protective equipment if working in insectaries, and education.

WHAT CAN BE DONE. Architects must design energy-efficient houses with resistance to insect infestations. Researchers R.J. Brenner, K.C. Barnes and R.M. Helm recommend that architects design houses with enhanced ventilation that allow for the exchange of indoor air with outside air and that remove by efficient filtration small particles from the air, reducing allergen loads.

The pest control industry must also design repellents to be used at the time of house construction. And baiting technology should be employed to eliminate existing infestations and prevent subsequent recolonizations.

Education is the key to the prevention and elimination of cockroach infestation. Public urban sanitation programs, such at the collection twice per week of tightly closed bagged garbage, have already been successful in lowering house fly infestations. A highly intensive public education program needs to be designed and implemented as soon as possible through radio, television, newspaper and broad distribution of flyers for the reduction of cockroach infestations and the concomitant reduction of cockroach allergies, especially allergic asthma in children.

Sidebar: ALLERGIC DISEASE IN THE UNITED STATES

Allergic disease affects 17% of the population, 37 million people. Asthma occurs in 3%of the population, or 3 million people.

3 million children under the age of 15 have athsma

Julieta Brambila, an entomologist, is a doctoral candidate with the University of Florida’s Tropical Research and Education Center in Homestead, Fla.

References

Brenner, R.J., K.C. Barnes, and R.M. Helm. 1990. Arthropod allergens in the urban environment. Proceedings of the National Conference on Urban Entomology, held on 25-28, Feb., 1990, in College Park, Md., pp. 57-66.

Brenner, R.J. 1992. Implications of cockroach behavior, allergens and pathogenic associates to the food supply and human health. Proceedings of the 3rd World Congress of Foodborne Infections and Intoxications, held on 16-19 June, 1992, in Berlin, Germany, pp. 1,111-1,114.

HayGlass, K.T. 1995. Allergy: who, why and what to do about it? Immunology Today, 16(11): 505-507.

Helm, R.M., W. Burks, L.W. Williams, D.E. Milne, and R.J. Brenner. 1993. Identification of cockroach aeroallergens from living cultures of German or American cockroaches. International Archives of Allergy and Immunology, 101: 359-363.

Helm, R.M., D.L. Squillace, R.T. Jones, and R.J. Brenner. 1990. Shared allergenic activity in Asian (Blattella asahinai), German (Blattella germanica), American (Periplaneta americana), and Oriental (Blatta orientalis) cockroach species. International Archives of Allergy and Applied Immunology, 92: 154-161.

Kang, B. and N. Sulit. 1978. A comparative study of prevalence of skin hypersensitivity to cockroach and house dust antigens. Annals of Allergy, 41: 333-336.

Massicot, J.G. and S.G. Cohen. 1986. Epidemiologic and socioeconomic aspects of allergic diseases. Journal of Allergy and Clinical Immunology, 78(5) part 2: 954-958.