MALNUTRITION, AGE AND THE RISK OF PARASITIC DISEASE - VISCERAL LEISHMANIASIS REVISITED

Children are said to be at greater risk of developing visceral leishma niasis (VL) when they are younger and more malnourished. If malnutriti on really is associated with VL, this potentially fatal and visible di sease may be a general indicator of community health among the rural a nd suburban poor. Previous conclusions reached about the roles of maln utrition and age in VL epidemiology are questionable because they may have been confounded by transmission rate, because they have not been able to distinguish between different mechanisms of acquiring immunity , and because empirical observations have not been compared with theor etical expectations. Here we offer a framework with which to investiga te these questions quantitatively, and do so with published data from endemic areas of Brazil. We conclude that children are indeed more sus ceptible to VL when they are younger and more malnourished, but it rem ains unclear whether the immunity to VL acquired with age is always ac quired as a result of infection. The significance for leishmaniasis co ntrol, and for the control of other diseases associated with malnutrit ion, will depend on underlying mechanisms, which are not yet understoo d.