Respiratory symptoms in arable farmworkers: role of storage mites

Storage mites (acarid mites) are related to the house dust mite but are usually found in agricultural environments. They have been shown to cause allergic symptoms in Scottish farmworkers exposed to stored hay, but whether farmworkers who grow and store grain are also at risk is unknown. One hundred and one farmworkers on 22 Essex farms with grain storage facilities (88% of the available workforce) participated in a survey of respiratory symptoms, with skin tests and determination of serum levels of IgE specific for mite species, including storage mites. Of the 101 workers, 21 reported attacks of cough, wheeze, or breathlessness after exposure to stored grain and 15 reported nasal symptoms after grain exposure. Storage mite specific IgE was found in 59% of farmworkers with work related respiratory symptoms, in 60% with work related nasal symptoms, and in only 9% of symptomless farmworkers. Work related respiratory and nasal symptoms were also significantly associated with atopy, and with positive skin test responses and serum IgE specific for Dermatophagoides pteronyssinus. Storage mites were found in grain samples from 16 farms in which grain was sampled, whereas D pteronyssinus was not found in any. The close association between serum storage mite specific IgE and occupational respiratory symptoms suggests that storage mites may be responsible for respiratory symptoms in these Essex farmworkers exposed to grain.