Prevention and morbidity of malaria in non-immune subjects; a case-control study among Italian troops in Somalia and Mozambique, 1992-1994.

The impact of malaria on Italian troops taking part in 1992-1994 in the United Nations Organization humanitarian missions in Somalia and Mozambique is discussed. In Somalia, 18 cases of Plasmodium falciparum malaria occurred among 11,600 soldiers; the overall attack rate was 0.4 cases/1000/month of exposure and the risk of malaria was effectively reduced by chemoprophylaxis with chloroquine plus proguanil (C+P) (odds ratio [OR] = 0.05, 95% confidence limits [95% CL] 0.02-0.16). In Mozambique, 119 cases of P.falciparum malaria occurred among 4800 soldiers; most cases (100) occurred in the first months of deployment (late March-June 1993), with an attack rate of 17 cases/1000/month, when C+P was the recommended chemoprophylactic regimen; the remaining 19 cases occurred subsequently, with an attack rate of 1.8 cases/1000/month, after C+P was replaced by mefloquine in July 1993. Protection achieved by C+P was unsatisfactory (OR = 0.37, 95% CL 0.21-0.67), while chemoprophylaxis with mefloquine effectively reduced the risk of malaria in Mozambique (OR = 0.03; 95% CL 0.01-0.10). A significant number of malaria infections was also detected among soldiers following their return home from Somalia (147 cases) and Mozambique (40 cases); these were due mainly to P. vivax. Fifteen of 113 P. vivax primary infections imported from Somalia (13.3%) relapsed 2-13 months after the primary attack. Because of the small proportion of relapsing P. vivax tropical strains, primaquine may be limited to radical treatment of relapses or, more extensively, of all P. vivax infections, but it should not be necessarily given to all asymptomatic subjects returning from tropical endemic areas, as is generally suggested for particular groups at risk.