The effect of desert conditions on the reactivity of Libyan schoolchildren to a range of new tuberculins.

This study was carried out to investigate the effect of desert conditions on the pattern of delayed hypersensitivity to mycobacteria in school children aged 6-10 and 11-18 years. A new range of tuberculins prepared from ultrasonic lysates of living mycobacteria belonging to 12 different species was employed. Three centres were chosen for study, a sea port and two desert towns differing greatly from each other. The results obtained were compared with those of a previous study using the same reagents in Kenya. As expected both the range of mycobacterial species to which the children reacted, the rate of acquisition of specific hypersensitivity with age and the total percentage of children reacting to individual reagents differed from centre to centre. The harsh desert conditions of Ajdabia produced the least, and the proximity of the people's dwellings to those of their farm animals in Kufra produced the most positive reactors to essentially environmental species. The greatest number of reactions to our Tuberculin were found in Benghazi where the cosmopolitan urban conditions probably lead to a high contact with open cases of tuberculosis. As assessed by skin test reactivity, immunization with BCG in Libya was much less effective than in Kenya. The interpretation of the differences between the results from the different test centres and between those for Libya and Kenya are discussed.