The epidemiology of tuberculosis among North Carolina migrant farm workers
S. D. Ciesielski, J. R. Seed, D. H. Esposito and N. Hunter
Department of Parasitology and Laboratory Practice, School of Public Health, University of North Carolina, Chapel Hill 27599.
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.
