Detection and quantification of pharaoh ant antigens in household dust samples as newly identified aeroallergens

The widespread house ant, Monomorium pharaonis (pharaoh ant, PA), was recently identified as a potential cause of respiratory allergies. However, there are no reports of the distribution of PA allergens in various environments. We developed specific ELISA inhibition assays and measured the distribution and amount of PA antigens in household dust samples.

Floor dust was collected at 3-month intervals from 56 homes in Seoul over a 1-year period. PA antigens in fine dusts were quantified by ELISA inhibition assays using rabbit anti-PA sera, and specific IgE to PA antigens in residents' serum was measured by ELISA.

In 18 of the 56 homes (32.1%), PA antigen was detected in at least 1 floor dust sample either from the living room or the kitchen. Levels of PA antigens showed seasonal variations with peaks in autumn and winter. The detection rate of PA antigens was significantly higher in homes with visual evidence of PA infestations (70%) than in homes without such infestations (23.9%; p < 0.05). However, a significant amount of PA antigens was still detected in uninfested homes. Thirteen of 113 (11.5%) residents were positive for PA-specific IgE. PA-specific IgE was detected more frequently in residents living in PA antigen-positive homes (19.6%) than in antigen-negative homes (4.8%; p < 0.05).

A considerable level of PA antigens is distributed in the indoor environment. Therefore, inhalant exposure to PA antigens can occur during domestic activities. These results suggest that PAs might be a significant source of aeroallergens in households.