Revisiting Konzo Risk Factors in Three Areas Differently Affected by Spastic Paraparesis in Eastern Democratic Republic of the Congo Discloses a Prominent Role of the Nutritional Status—A Comparative Cross-Sectional Study

Abstract

This comparative cross-sectional study aimed to better understand the respective contributions of protein malnutrition and cassava-derived cyanide poisoning in the development of konzo. We compared data on nutritional status and cyanide exposure of school-age adolescent konzo-diseased patients to those of non-konzo subjects of similar age from three areas in the Eastern Democratic Republic of the Congo. Our results show that konzo patients had a high prevalence of both wasting (54.5%) and stunting (72.7%), as well as of cyanide poisoning (81.8%). Controls from Burhinyi and those from Idjwi showed a similar profile with a low prevalence of wasting (3.3% and 6.5%, respectively) and intermediate prevalence of stunting (26.7% and 23.9%, respectively). They both had a high prevalence of cyanide poisoning (50.0% and 63.0%, respectively), similar to konzo-patients. On the other hand, controls from Bukavu showed the lowest prevalence of both risk factors, namely chronic malnutrition (12.1%) and cyanide poisoning (27.6%). In conclusion, cassava-derived cyanide poisoning does not necessarily coexist with konzo outbreaks. The only factor differentiating konzo patients from healthy individuals exposed to cyanide poisoning appeared to be their worse nutritional status. This further suggests that, besides the known role of cyanide poisoning in the pathogenesis of konzo, malnutrition may be a key factor for the disease occurrence.

Impact of Seasonal Variation and Processing Methods on the Cassava-Derived Dietary Cyanide Poisoning, Nutritional Status, and Konzo Appearance in South-Kivu, Eastern D.R. Congo

“…However, our data did not show differences between Burhinyi and Idjwi regarding processing shortcuts, in contradiction with Banea JP et al, who found an association between konzo outbreak in Bandundu (western DRC) and frequent shortcuts in cassava processing, especially a shorter fermentation [18]. Thus, Burhinyi and Idjwi appeared, once more, to undergo similar cassava-derived cyanide exposure, regardless of their differences in the occurrence of konzo, as previously observed [28].…”

“…This study showed high uSCN levels in participants from Idjwi and Burhinyi, witnessing persistent dietary cyanide poisoning in both areas [27,28]. As stated above, growing bitter cassava (and to a lesser extent, also sweet toxic varieties), as well as shortening or skipping heap fermentation during the processing, prominently contributed to cyanide exposure, although our results could not show a significant correlation between the cyanide content of cassava flour and uSCN (the study was not specifically designed for this type of analysis).…”

“…This study was conducted in Burhinyi and Idjwi, two rural areas of South-Kivu province, in the eastern DRC. Detailed information on these areas is presented elsewhere [28]. In brief, Burhinyi is a mountainous area located in the territory of Mwenga, ~65 km southwest of Bukavu (the capital city of the province), where konzo cases were first and solely reported in eastern DRC [27].…”

“…As elsewhere in the DRC, cassava products are predominant in the population's diet of both areas. As stated above, dietary cyanide poisoning from cassava prevails in both regions [28], associated to konzo in Burhinyi [27], contrary to Idjwi, where no konzo case has been so far reported, rather, a high prevalence of endemic goiter [21,31].…”

“…Furthermore, cassava-derived dietary cyanide poisoning was already reported in Idjwi, another rural district of the province, in the 1970s, and was suspected to contribute to the high prevalence of endemic goiter in this region [21]. A recent survey confirmed the persistence of cassava-derived cyanide poisoning in Idjwi [28], while no case of konzo has been observed there so far. The same study pointed out that the most discriminating factor between Idjwi and Burhinyi was the nutritional level, which was by far worse in Burhinyi than in Idjwi, hence the hypothesis that nutritional status would be more determinant in the appearance of konzo in Burhinyi.…”