High prevalence of immunoglobulin E (IgE) sensitization among sisal (Agave sisalana) processing workers in Tanzania

Allergic sensitization among workers exposed to sisal is scarcely documented. We examined whether sisal processing is associated with IgE sensitization and its relationship to the prevalence of respiratory symptoms among Tanzanian processors.

138 sisal exposed workers and 78 non-exposed controls were skin prick tested (SPT) using dry sisal extract and fresh sisal sap. Sera from a subset of 43 participants were analyzed for total and sisal specific IgE. SPT wheal size, prevalence of positive SPTs and adjusted relative risk (RR) for sisal sensitization were determined and compared between exposed and controls. Prevalences for respiratory symptoms were compared between sensitized and non-sensitized sisal workers.

Significantly higher prevalence of positive SPTs to sisal was found among 74 % of sisal workers compared to 17 % among controls. Compared to controls, the RR of sensitization to sisal was 4 times higher (95 % CI; 2.4-6.7) among exposed workers. All exposed workers had elevated IgE levels (>100 kU/l) and 27 % of tested sera had elevated sisal specific IgE. A high prevalence of respiratory symptoms was found in both sensitized and non-sensitized sisal workers.

Sisal processing is associated with increased risk of IgE sensitization, but its clinical implication is not obvious.