Using a matched case-control design, we sought to determine whether the odds of konzo, a distinct spastic paraparesis associated with food (cassava) cyanogenic exposure in the tropics, were associated with lower cyanide detoxification rates (CDR) and malnutrition. Children with konzo (N= 122, 5–17 years of age) were age- and sex-matched with presumably healthy controls (N = 87) and assessed for motor and cognition performances, cyanogenic exposure, nutritional status, and cyanide detoxification rates (CDR). Cyanogenic exposure was ascertained by thiocyanate (SCN) concentrations in plasma (P-SCN) and urine (U-SCN). Children with a height-for-age z-score (HAZNCHS) < −2 were classified as nutritionally stunted. CDR was measured as time required to convert cyanide to SCN, and expressed as ms/μmol SCN/mg protein or as mmolSCN/ml plasma/min. Mean (SD) U-SCN in children with konzo was 521.9 (353.6) μmol/l and was, significantly higher than 384.6 (223.7) μmol/l in those without konzo. Conditional regression analysis of data for age- and sex- matched case-control pairs showed that konzo was associated with stunting (OR: 5.8; 95% CI: 2.7–12.8; p <0.01; N = 83 paired groups) and higher U-SCN (OR: 1.1; 95% CI: 1.02–1.20 per 50-μmol increase in U-SCN; p = 0.02; N = 47 paired groups). After adjusting for stunting and U-SCN, the odds of developing konzo was reduced by 63% (95% CI: 11–85%, p = 0.03; N = 41 paired groups) for each 5 mmol SCN/(ml plasma/min)-increase in CDR. Linear regression analysis indicated a significant association between BOT-2 or KABC-II scores and both the HAZNCHS z-score and the U-SCN concentration, but not the CDR. Our findings provide evidence in support of interventions to remove cyanogenic compounds from cassava prior to human consumption or, peharps, enhance the detoxification of cyanide in those relying on the cassava as the main source of food.

No abstract

Traditionally, cassava (Manihot esculenta Crantz) is transformed by fermentation in water (retting) or in the open air (dry fermentation) in the DRC. In the east of the country (North Kivu), dry fermentation is the main technique for processing cassava for its detoxification and conservation. The Congolese farmers ferment the cassava to the open air using a preselected microferment contained in the scrapings of the fermented cassava previously called "MUSIYIRO". These fermentations are spontaneously directed by the microorganisms of the uncontrolled autochthonous flora. Unfortunately, toxinogenic molds are often more active in the fermentation process during which they also produce aflatoxins. This study was undertaken to help prevent the production of aflatoxins in cassava during this process. To do this, we substituted the traditional ferment with a strain of Rhizopus oryzae used as starter (microferment). Six successive replications, in controlled fermentation and uncontrolled fermentation, in a peasant environment (Beni, North Kivu) and fermentation directed by the strain of R. oryzae were carried out. Aflatoxins were then dosed in both groups of cassava flours. The results of the assay revealed an absence of aflatoxins in cassava fermented by scrapings from fermentation led by R. oryzea, while the non-directed fermentation controls were all contaminated with aflatoxins. These results show that it is possible to prevent the production of aflatoxins in cassava during fermentation when an aflatoxin-inhibiting microbial biomass is used which can progressively invade and colonize the fermentation site and thereby control the fermentation activities of cassava.