Malaria, leprosy and dapsone.

Although the preventive action of dapsone against P. falciparum malaria was known for many years, there was no report about the incidence of P. falciparum malaria in leprosy patients treated with dapsone, especially from areas of Southeast Asia where both leprosy and malaria are endemic. Therefore, two clinic-based malaria surveys were undertaken at a gap of 12 years, comprising 506 lepromatous leprosy patients and 499 febrile nonleprosy control subjects. Both the surveys showed that the lepromatous patients treated with MDT had only P. vivax malaria (incidence comparable to the febrile nonleprosy controls) with complete freedom from P. falciparum. On the contrary, control sujects not taking any-leprosy drugs and staying with the leprosy patients at the same beggars' home, had both P. vivax and P. falciparum malaria. It is postulated that dapsone provided protection against P. falciparum among leprosy patients.