Immuno-epidemiological studies on subclinical infection in leprosy, II. Geographical distribution of seropositive responders with special reference to their possible source of infection.

The percentage of positive fluorescent leprosy antibody absorption (FLA-ABS) tests showed significant differences among the inhabitants of different regions in Okinawa. Provided that this percentage indicates the frequency of subclinical leprosy infections, the numbers of inhabitants with subclinical infection per new case with leprosy in the same region ranged from 723 to 3,039. The FLA-ABS test was positive in 16.2% of adults in Minami daito Island where no new case with leprosy was found during the survey for seven years. The differences in the percentages could not be explained by the different prevalence and incidence rates of leprosy in each region nor by the differences in age and sex of the individuals examined. A significant correlation between the FLA-ABS tests and neural signs or symptoms was found in 3 regions. None of adults in Minami daito Island showed such signs or symptoms. The distribution of FLA-ABS positive and negative responders in two hamlets where the incidence of leprosy was relatively high suggested the localization of positive responders surrounding houses in which a leprosy case had recently been found and also the distribution of positive responders in the remote houses. These facts seem to indicate that a possible source of infection to the majority of positive responders might be from the environment rather than from direct contact with leprosy patients.