[Public Health] Allergic Asthma

The evidence of a relationship between allergic asthma and domestic exposure to cockroaches, mice and dust mites is strong.

Here’s what you need to know about these pests in urban environments.
 

Editor’s note: This article was excerpted from "Public Health Significance of Urban Pests." Pest management professionals may download the book from NPMA’s Web site at www.npmapest world.org/ftp/WHO-Urban%20Pests.pdf at no charge.

In addition, a summary of the book and its main messages has been prepared by the Chartered Institute of Environmental Health (CIEH) in the United Kingdom. This publication can be accessed at www.cieh-npap.org/documents/Urban-pests-publichealth-significanceJULY08.pdf or in various languages at www.urbanpestsbook.com.

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Asthma is a major urban disease and a substantial burden from the standpoint of both the quality of life for the many suffering from the disease and the economics of health care. The global increase in the prevalence of asthma in the last half of the 20th century has affected urban communities in many countries disproportionately. Asthma is an allergic disease for more than 50 percent of adults and 80 percent of children. The evidence for a relationship between allergic asthma and domestic exposure to cockroaches, mice and dust mites is strong. These pests are common in urban environments, especially impoverished communities, and play a significant role in the pathogenesis of urban asthma.

Cockroaches and asthma. In many areas of the world, sensitization to cockroach allergens has been associated with asthma. In inner cities in the United States, more asthmatic children with cockroaches reported or observed in their home were sensitized to cockroach allergens than those without exposure to cockroaches. A study of urban, suburban and rural atopic patients found a higher prevalence of cockroach sensitivity among patients with a primary diagnosis of asthma (49.6 percent) than among those with a primary diagnosis of allergic rhinitis (30.3 percent). Also in this study, no difference was observed between the prevalence of sensitivity to cockroach allergens in urban and rural environments. This finding is in contrast to previous studies in Poland and the United States, which reported a high degree of sensitization to cockroach allergens among urban dwelling asthmatics. Nonetheless, sensitivity to cockroach allergens appears to be important in the pathogenesis of asthma in areas with cockroaches.

Exposure to cockroach allergens in early life has been associated with recurrent asthmatic wheezing in children with a family history of atopy. This was also observed in the first year of life, when allergy-specific IgE to inhaled allergens typically cannot be detected, suggesting a potential role for a non-allergic mechanism of airway inflammation due to exposure to cockroach allergens. Also, the combination of exposure and sensitization to cockroach allergens has been shown to increase rates of hospitalization, missed school days and days with wheezing among asthmatic children. Moreover, recent evidence suggests that the combination of exposure and sensitization to cockroach allergens is a stronger risk factor for asthma morbidity in the inner cities of the United States than is exposure and sensitization to allergens produced by dust mites, cats or dogs.

Rodents and asthma. Most of what is known about allergic reactions to mice and rats originates from occupational studies. Symptoms of allergy, including rhinitis, conjunctivitis and asthma, have been reported by workers in animal laboratories, notably those that work with rats and mice. In the 1970s, British researchers reported that five people who worked with laboratory animals developed asthma within two weeks to two years of starting to work with mice and rats. Within a year of developing asthma, all five workers experienced asthma symptoms after only a few minutes of exposure to the animals.

These studies were among the first to show that urinary proteins from rats and mice, rather than fur, elicited stronger positive skin prick tests and bronchial hyperreactivity. In a multi-site study of 650 people who worked in animal laboratories in the Netherlands, Sweden and the United Kingdom, researchers found that 9.7 percent of the workers were sensitized to rat urinary allergens. They also found a higher risk of sensitization to rats associated with high exposure to rat allergens. Recently, researchers realized that mouse and rat allergens also might contribute to the development or exacerbation (or both) of childhood allergic asthma. Polish researchers found that 61 percent of inner-city children exposed to detectable levels of mouse allergen were skin prick positive to these allergens, whereas only 14 percent of children with levels below the limit of detection were sensitized to mice.

While the terms "urban" and "suburban" are somewhat subjective, it is of interest to report that mouse allergens measured in suburban homes in the United States have also been associated with sensitization to mouse allergen, as judged by a skin prick test. Even low levels of mouse allergen can pose a risk of developing allergic sensitization. Furthermore, Polish researchers found that children of workers in animal laboratories were also allergic to mice and rats, suggesting that passive transfer of rodent allergens from work to the home might be a biologically relevant exposure pathway.

Conclusions. Asthma is a major disease of the urban environment and a substantial burden from the standpoint of both the quality of life for the many suffering from the disease and the economics of health care. The global increase in the prevalence of asthma in the last half of the 20th century has disproportionately affected urban communities in many countries. The evidence that relates asthma and domestic exposure to cockroaches, mice and dust mites is clear. These pests are common in urban environments and play a significant role in the pathogenesis of urban asthma. Removing these pests and their allergens is a logical tactic for preventing disease and reducing symptoms, but this tactic needs improved efficacy. Results from studies on avoiding allergens suggest cautious expectations about the ease with which long-term clinically relevant allergen reductions can be accomplished. However, the burden of asthma in urban communities may be effectively reduced through more broadly defined asthma interventions that include allergen reduction tailored to an individual’s specific allergy, education about effective methods for sustained Integrated Pest Management and general education about asthma.

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CDC EXPERT TRAINS ORKIN SPECIALISTS ON PETS AND PESTS

Late last year, a specialist from the Centers for Disease Control and Prevention (CDC) educated hundreds of Orkin residential and commercial pest control technicians across the country on pets and parasites, associated diseases and prevention mechanisms during a live broadcast. Dr. Susan Montgomery of CDC’s Parasitic Diseases Branch led an in-depth seminar on parasites that pets and humans share using Orkin’s interactive satellite television communications network.

Facilitated by Dr. Ron Harrison, technical director for Orkin, the broadcast was the second session offered in 2009 by Orkin and the CDC. The organizations expanded their formerly once-a-year, fall program to include a spring and fall training session, four live broadcasts per session and Continuing Education Units (CEUs) for participating technicians in 2009. More than 260 of the company’s 400 field locations participated in the live broadcast; remaining locations viewed the program through a video-on-demand feature in the weeks that followed.

Montgomery explained how pets can carry parasites that can infect humans, including tapeworm and heartworm infections. Technicians learned what parasitic diseases people and pets can share and how to reduce the risk of exposure to these diseases.

"Orkin’s collaboration with the CDC is unique in the industry, and we are proud to host the fall session of our fourth annual training program," said Glen Rollins, president and chief operating officer of Orkin. "The CDC training sessions are an important tool for keeping field employees, and in turn, customers, armed with the information they need to help protect their families, including household pets, from pests and related diseases."

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Dust Mites And Asthma

Dust mites are found in the bedding, pillows, mattresses, carpets and upholstered furniture of homes, where they feed on scales from human skin. They absorb water from the air, and therefore require a relative humidity above 50 percent to survive. This restricts the environments inhabitable by mites and is a major controlling factor in the geographical distribution of dust mites. Reducing indoor air humidity has recently been used with some success as a mite eradication strategy. In major cities of the Northeastern United States, multi-family buildings are often overheated during the winter, which leads to low humidity air indoors and precludes the proliferation of dust mites. Mite genera vary geographically, with Dermataphagoides being more common in temperate climates and Blomia being found only in tropical climates.

Source: "Public Health Significance of Urban Pests"