Prevalence of sensitization to Tetranychus urticae in greenhouse workers

Background Tetranychus urticae (TU) is a macroscopic mite which infests a l arge number of plants of economic interest worldwide. It has recently been described as a cause of occupational allergic disease in greenhouse workers . However, there are no epidemiological data concerning the prevalence of T U allergy in an unselected exposed population. Objective The aims were to study the prevalence of TU sensitization among g reenhouse workers and its relationship to the working environment and to pe rsonal factors. Methods We studied 246 consecutive greenhouse workers, recruited directly f rom the field. A clinical and epidemiological questionnaire, a skin-prick t est (SPT) to TU and common allergens and TU-specific IgE (RAST) determinati ons were performed. Seventy-five healthy volunteers and 152 atopic patients were used as a control group. Results The prevalence of a positive SPT to TU was of 25%. Forty-five worke rs (19%) were TU-allergic, occurring more often in atopic greenhouse worker s (P < 0.0001). Seven per cent showed asymptomatic sensitization. The time of exposure to TU was significantly greater in the TU-allergic patients (P < 0.05). The probability of sensitization to TU was 3.7 times greater in ex posed than in non-exposed subjects (P < 0.0001). Conclusions In this study, the prevalence of TU sensitization was 25%. Ther e were significant associations with TU allergy and atopy and the time of e xposure to TU.