Pests And Humans: An Allergic Relationship

The National Pest Control Association and members of our industry have repeatedly proclaimed that we are protectors of food, health, property and the environment. But how well are we able to fulfill this claim as protectors of health?

The relationship between human allergies and arthropod infestations (house dust mites) was demonstrated nearly 40 years ago. Since that time many studies have been conducted in Europe and the U.S. which further demonstrate the significant impact that arthropods have on allergic individuals, especially asthmatics. In fact, diagnostic and clinical studies conducted by allergists have found house dust mite and cockroach allergens to be the most common allergens implicated by asthmatics.

HISTORY. House dust was identified as a significant allergen in predisposed individuals as early as 1920. In the 1960s, European researchers identified house dust mites as one of the “house dust” allergens. For the next 20 years, most of the research in the United States focused on house dust mites as the principal household pest associated with arthropod allergies. It wasn’t until the early 1970s that researchers began to focus attention on allergies associated with cockroaches.

This was most likely because, in comparison to house dust mites, cockroaches represent a substantially different threat to human health, and allergy is but one aspect. Cockroaches have been associated with several hundred pathogenic organisms including bacteria, fungi, viruses, protozoans and helminths. Granted, much of this information has been generated through laboratory studies and isolation of these disease-causing organisms from field-collected cockroaches. However, there is strong circumstantial evidence linking cockroaches to several disease outbreaks of hepatitis, typhoid and dysentery.

Direct disease transmission, which is easily demonstrated in blood-feeding arthropods, is much more difficult to prove in mechanical disease vectors such as cockroaches. However, it is easy to appreciate the possibility of these filth-feeding and inhabiting cockroaches infecting food, preparation surfaces, utensils and plates with disease-causing organisms.

While evidence of cockroach-transmitted pathological diseases is mostly circumstantial, there is unequivocal evidence that cockroaches are directly associated with human allergies. Studies as early as the 1960s implicated cockroaches as a source of allergens.

THE COST OF CARE. The New England Journal of Medicine recently published a study of 476 children, ages 4 through 9, with asthma from eight inner-city areas in the U.S. The study concluded that of allergens associated with cockroaches, mites and cats, cockroach allergens produced more hospitalization and clinical visits. Another report estimated that in 1991, the cost of managing asthmatic episodes in the United States was $3.1 billion and there were 5,000 deaths. As many as 80% of childhood deaths from asthma occurred in urban children. African-American children were four to six times more likely to die from the disease than were white children.

It is not simply the presence of cockroaches that can precipitate an asthmatic or other allergic response, but anything associated with cockroaches, including their skin casts, dead bodies, pheromones, excreta and secretions. Thus, the significance of cockroach infestations, their mitigation and removal of allergen becomes important.

Our industry faces several issues regarding the reduction of this threat to human health. The following risky assumptions are those at the top of my list:

• Believing that killing cockroaches removes all allergens from the environment; it does not.
  
  
• Knowing that conventional treatments with sprays and aerosols may stir up cockroaches and allergens, thereby disbursing them into the environment.
  
  
• Promising something one cannot deliver at this time; for example, allergen removal and allergy prevention.
  
  

What we can do is:

• Know that technicians are at risk of occupational exposure to cockroach allergens.
  
  
• Minimize allergen production by eliminating cockroach infestations.
  
  
• Reduce allergen exposure by vacuuming (with HEPA filters) and using baits to eliminate cockroach infestations.
  
  
• Reduce exposure by caulking and sealing harborages, which can also seal off allergens in wall voids and similar areas.
  
  
• Provide advice on cleaning processes (as they are developed) that reduce the allergen load in the human environment.

Research to be conducted:

• Development of a rapid allergen detection system to determine when removal is below the clinical threshold.
  
  
• A method for denaturing and/or isolating allergens in deep harborages.
  
  
• Quick and economical methods for removing allergens.

QUESTIONS REMAIN. Despite the many studies examining the relationship between arthropods and human allergies, questions still remain. For instance, it is still unknown what level of cockroach mitigation and allergen removal is clinically significant. Presently there are several studies underway throughout the United States focusing on ways to reduce the impact of cockroach and other arthropod allergens to human health.

The most important point we can take away from our knowledge of emerging cockroach management strategies and allergen mitigation process is that we, the pest control industry, can make a difference.