The epidemiology of tuberculosis among North Carolina migrant farm workers

Although tuberculosis (TB) has been recognized as a significant health problem of migrant farm workers, the nature and extent of the problem have been poorly defined. We report the first population-based study of TB in a random sample of farm workers (n = 543) and the first use of recall antigens in an epidemiologic study of TB. Purified protein derivative positivity ranged from 33% in Hispanics to 54% in US-born blacks and 76% in Haitians. Active tubercular disease occurred in 3.6% of US-born blacks and 0.47% of Hispanics. Among US-born blacks, risk factors associated with farm work were most significant. Blacks born in the United States also had the highest prevalence of anergy. The use of recall antigens made possible a better description of the epidemiology of TB by excluding false negatives and clarifying associations between infection and risk factors. We conclude that TB among farm workers represents a serious public health problem with previously unrecognized risk factors. Additional resources for migrant health care, improvements in health care access, and fundamental changes in the system of migrant labor are all necessary to reduce the transmission of TB.