Epidemiology of mycobacteria other than tubercle bacilli in South Africa

The findings of the last two decades in the area of the epidemiology of mycobacteria other than tubercle bacilli are reviewed. The veterinary problem of cross-reactivity in cattle to the tuberculin test was overcome by comparative use of avian purified protein derivative (PPD). Outbreaks of mycobacterial lymphadenitis in swine occur sporadically and are due to Mycobacterium intracellulare. The reservoir for nontuberculous mycobacteria appears to be in the environment, especially on growing fodder plants; water cannot be incriminated. In humans very few cases of mycobacteriosis have been found. However, countrywide surveys of random sputum cultures have shown that exposure of rural people to Mycobacterium avium-intracellulare is either continuous or frequent. Ten percent of African children react specifically to avian PPD tuberculin. No direct influence of this exposure on the incidence of tuberculosis can be seen. No protective effect by mycobacteria other than tubercle bacilli is postulated.