Tetanus seroprevalence among farmers: a preliminary study

Farmers are at increased risk of contracting tetanus. However, no difference in immunity to tetanus has been reported between rural and urban dwellers in large epidemiological studies. We hypothesized that tetanus antibody concentrations would be lower in farmers than in nonfarmers within the rural population.

We recruited 102 adult subjects attending an agribusiness trade show who identified themselves as farmers in Wisconsin. The nonfarmer group (n = 120) was composed of adults attending the agribusiness show who were not engaged in farming or were participating in another research study. Concentrations of antibody to tetanus toxin (antiTT) in sera were measured by an enzyme-linked immunosorbent assay (IBL, Hamburg). AntiTT levels of >0.15 IU/mL were considered protective.

The antiTT concentrations for the farmer population (median = 2.74 IU/mL) were much higher than those for the nonfarmer group (median = 1.82 IU/mL) (P<.008). As in other studies, being male, being younger, and having a history of military service were positively correlated with protective antiTT concentrations. However, only farming, age, and the farming-sex interaction term were significantly associated with antiTT concentrations in the multiple-regression model.

The farmers we studied had high antiTT concentrations and a high tetanus seroprevalence rate. Occupation may be an important consideration in the development of immunization policies. A broader seroepidemiological study of farmers must be undertaken before any such considerations can be made.