Skin-test studies with a series of tuberculins have been carried out in close contacts of multibacillary (MB)
leprosy patients around three
leprosy centers in India, and casual contacts of the disease around two centers. The results show that the rate of acquisition of
leprosin A positivity is associated with age and the closeness of contact with MB
leprosy. At the age of 15 years, the differences between the two types of contact were highly significant (p less than 0.00001). Many responses to
leprosin A are directed toward the group iv species-specific,
antigens of the
leprosy bacillus, and the significance of positivity is discussed in relation to protective immunity from
leprosy. The differences from Iran show that positivity to
leprosin A is not solely the effect of the degree of contact with the disease, but must also have a genetic or environmental
element, the latter being favored. The results from Miraj show that the high levels of
tuberculin,
scrofulin, and
vaccin positivity seen in Fathimanagar, and to a lesser extent in Karigiri, are not a consequence of contact with
leprosy. BCG vaccination made little difference to the
leprosin A positivity of close contacts of
leprosy patients, although it significantly enhanced positivity among casual contacts around Miraj (p less than 0.002). BCG vaccination significantly increased
tuberculin positivity in Miraj and Karigri, and in those under 11 years of age in Fathimanagar. It made no difference to the already high level of positivity found in older persons around Fathimanagar.(ABSTRACT TRUNCATED AT 250 WORDS)