Konzo and continuing cyanide intoxication from cassava in Mozambique

In Mozambique, epidemics of the cassava-associated paralytic disease, konzo, have been reported in association with drought or war: over 1100 cases in 1981, over 600 cases in 1992-1993, and over 100 cases in 2005. Smaller epidemics and sporadic cases have also been reported.Large epidemics have occurred at times of agricultural crisis, during the cassava harvest, when the population has been dependent on a diet of insufficiently processed bitter cassava. Konzo mostly affects women of child-bearing age and children over 2. years of age.When measured, serum or urinary thiocyanate concentrations, indicative of cyanide poisoning, have been high in konzo patients during epidemics and in succeeding years. Monitoring of urinary thiocyanate concentrations in schoolchildren in konzo areas has shown persistently high concentrations at the time of the cassava harvest. Inorganic sulphate concentrations have been low during and soon after epidemics.Programmes to prevent konzo have focused on distributing less toxic varieties of cassava and disseminating new processing methods, such as grating and the flour wetting method. Attention should be given to the wider question of agricultural development and food security in the regions of Africa where dependence on bitter cassava results in chronic cyanide intoxication and persistent and emerging konzo

Rising African cassava production, diseases due to high cyanide intake and control measures

Cassava is the staple food of tropical Africa and its production, averaged over 24 countries, has increased more than threefold from 1980 to 2005, and the population has more than doubled over that time compared with a 1.5 times increase worldwide. Agriculturally, cassava performs very well but the roots and leaves contain cyanogenic glucosides that are dangerous to human health. These cyanogens sometimes produce acute intoxication leading to death, they exacerbate goitre and cretinism in iodine-deficient regions, cause konzo and are implicated in the occurrence of tropical ataxic neuropathy and stunting of children. Konzo is an irreversible paralysis of the legs with many thousands of cases, mainly amongst children, in Mozambique, Tanzania, Democratic Republic of Congo, Cameroon, Central African Republic and probably other tropical African countries. Attempts to alleviate cassava cyanide toxicity have included the development of an information network and distribution in developing countries of picrate kits, which measure total cyanide in cassava and urinary thiocyanate. A simple wetting method that reduces total cyanide in cassava flour three- to sixfold has been successfully field tested and is being introduced in Mozambique. Transgenic technology shows promise in increasing the rate of loss of cyanide from roots during processing. World health and agricultural bodies should pay more attention to emerging health problems associated with toxicity of cyanogens in cassava