Submitted to: Journal of Allergy Clinical Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/1999
Publication Date: N/A
Citation: Interpretive Summary: Inner city asthmatic children are at high risk of cockroach-induced asthma resulting from exposure to allergenic cockroach proteins. Medical practitioners have theorized that exterminating the cockroaches will reduce exposure to allergens. However, because allergenic cockroach proteins may persist for many years in a structure; eliminating cockroaches may only prevent further accumulation of allergens, but would not address allergens that had accumulated over time. Therefore, we hypothesized that eliminating cockroaches would not reduce allergen loads significantly. Scientists at Duke University and the USDA Agricultural Research Service's Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL tested this hypothesis. Sticky traps were used in 8 homes, and revealed substantial German cockroach (Blattella germanica) populations. These traps were used to guide placement of bait stations containing hydramethylnon. Although populations were reduced by 95% over the 6 month of the project, there was no significant change in allergen load measured in dust vacuumed from several areas of each home at two month intervals. Researchers concluded that elimination of existing allergens must be accomplished concurrent with cockroach control measures. Currently, the extent of cleaning required to effect an immediate drop in allergen is not known, and additional research is underway.
Technical Abstract: The impact of cockroach management on allergen load was studied in 8 homes near Durham, NC over a 6 month period. Sticky traps left in place overnight were used to measure populations of German cockroaches, Blattella germanica. Multiple dust samples from 1m 2 square vacuumings (2 min. each), taken at 2 month intervals, were analyzed using monoclonal antibodies (units per ml of Bla g 1 and Bla g 2 were converted to units of allergen per gram of dust). The location of the traps and baits were plotted on diagrams of the rooms. Homes with 10 or more trapped cockroaches continued in the study and were visited again at 2, 4, and 6 months. Homes were assigned to active intervention (n=5) or to placebo (n=3) in a single blind fashion. We placed 2% hydramethylnon bait trays (Combat Superbait, Clorox Company, Pleasanton, CA) in actively-treated houses and identical -appearing placebo bait stations in placebo-treated houses. Occupants of homes were not asked to do any cleaning. Baits were replaced at the 4 -month visit. At 2 months, 4 of 5 treated homes showed a greater than 95% reduction in cockroaches trapped (p<0.05, Wilcoxon rank-sum test), and this was sustained through the 6 month follow-up. Sufficient dust for analysis was obtained from all the rooms. At 2 and 4 months, no significant difference was seen between active and placebo homes for either Bla g 1 or Bla g 2 content in the dust. At 6 months, in the treated homes, there was a statistically significant decrease in Bla g 1 (p=0.048, Wilcoxon rank-sum test) but not Bla g 2. We conclude that despite the reduction in cockroaches present, there was not a correspondingly impressive decrease in allergen in the dust.