Control of Konzo and Kits to Determine Cassava Cyanide and Urinary Thiocyanate

Prevention of Konzo

Konzo is an upper motor neuron disease that causes irreversible paralysis of the legs and occurs mainly in children and young women of child-bearing age. The paralysis occurs quite suddenly, does not progress over time and is irreversible. It is associated with the consumption of a monotonous diet of high cyanide (bitter) cassava, (see Cassava: agriculture, rising African production and cyanogens), by poor rural people in Africa, many of whom suffer from malnutrition. Specifically, konzo is associated with a high cyanide diet of bitter cassava consumed over a period of several weeks combined with a low intake of protein, particularly a shortfall of essential S-containing amino acids that are needed to detoxify cyanide to thiocyanate in the body.

Konzo occurs in the Democratic Republic of Congo (DRC), Mozambique, Tanzania, Cameroon, Central African Republic and Angola. The incidence of konzo is greatest in the DRC; the total number of cases is unknown but one estimate is 100,000 cases. Konzo epidemics occur during drought when the cassava plant is stressed and produces much larger amounts of cyanide compounds (cyanogens) than usual and also as a result of war when people are displaced from their homes and forced to eat bitter unprocessed cassava from the bush (Nhassico et al., 2008). Konzo was first reported by Dr Trolli, in the then Belgian Congo in 1938, in Popokabaka Health Zone in Bandundu Province and we have prevented konzo for the first time ever in the same Health Zone (Banea et al, 2012a). 

In all our studies in DRC we find that konzo has increased greatly since 2009, due to smaller amounts of cassava being grown, which has resulted in short-soaking of cassava roots for only 1-2 days, instead of the 3-4 days required to completely remove cyanogens from the root.

Wetting method. In 2005 we discovered a new wetting method that reduces greatly the cyanide content of cassava flour. Water swells the flour and allows contact between linamarin and the enzyme linamarase that catalyses the breakdown of linamarin to acetone cyanohydrin, which breaks down spontaneously to liberate hydrogen cyanide gas. The process requires standing in the sun for two hours or in the shade for five hours (Bradbury, 2006; Cumbana et al., 2007; Bradbury and Denton, 2010). The wetting method is a gift from God. The detailed wetting method is as follows:

The cassava flour is placed in a bowl and its height is marked on the inside of the bowl. Water is added with mixing and the volume of the flour initially decreases, but then increases and more water is added until the flour reaches the mark. The evenly wet flour is spread out on a mat or basket in a thin layer not greater than a fingernail thick (about1 cm) and left in the sun for 2 hours or the shade for 5 hours to allow hydrogen cyanide gas to escape. The wet flour is then added to boiling water in the traditional way to make a stiff porridge called fufu, which is eaten with something to give it flavour such as beans or a sauce.

SAWBO wetting method - Video

Methodology to prevent konzo. The procedure that is used to prevent konzo involves first a visit to the Health Offices in the District and the Health Zone to identify the konzo villages which most require an intervention followed by a visit to these villages. A second visit of the full team is made one month later, in which a census is taken, all konzo cases examined and cassava flour samples and urinary thiocyanate from school children are analysed, see Kits available to measure total cyanide in cassava and urinary thiocyanate. Urinary thiocyanate levels give the best measure of intake of cyanogens over the previous week or so. The senior women are then taught the wetting method for removing cyanogens from flour, using illustrative posters in their language (Kiyaka), see Posters available on wetting method to remove cyanide. They in turn each teach 12-15 women to use the wetting method and a bowl, knife and a mat is given to each woman. The women readily accept the wetting method, particularly as it improves greatly the flavour of the traditional thick porridge (fufu), which loses the bitter flavour due to the removal of the cyanide compound (linamarin) from the flour. The fufu also stores better than fufu made from untreated flour.

A third and fourth visit are made at four month intervals to the village to teach the wetting method to those unfamiliar with it, and to obtain the urinary thiocyanate contents of school children and cassava flour cyanide results. Between these major visits there are visits every month of a team of women from Caritas to check on the use of the wetting method by the women. In all cases we find no new cases of konzo after the intervention commences and urinary thiocyanate and cassava flour cyanide levels are greatly reduced.

We returned to four villages more than one year after the interventions had ceased to see whether the wetting method was still being used. In all cases there were no new cases of konzo, the great majority of women were still using the wetting method and urinary thiocyanate and cassava flour cyanide levels were low. Best of all, the wetting method was popular with village women and had spread by word of mouth to nearby villages (Banea et al., 2014a).

The total time of an intervention has decreased from 18 months in the first intervention (Banea et al., 2012a) to 12 months (Banea et al., 2013) and then to 9 months (Banea et al., 2014b) and the cost reduced to $16 per person.

Konzo related to high cyanide intake and malnutrition. We surveyed 22793 people with 172 konzo cases in Kwilu District, Bandundu Province, DRC and found that there was less konzo in those villages where there was a better diet and less malnutrition (Banea et al., 2015a). We have now studied six villages with 4588 people and 144 konzo cases and obtained food consumption scores from which the percentage malnutrition (%M) for each village was calculated. The percentage of children with high urinary thiocyanate content (%T) was obtained, which is a measure of high cyanide intake. It was found that the percentage of konzo prevalence (%K) for each village was related by the simple equation

%K = 0.06 %T + 0.035 %M,

which does not apply if either %T or %M is zero. This is a first attempt to relate mathematically konzo prevalence with high cyanide intake and malnutrition, which are both necessary together for konzo to occur.

In total, interventions to prevent konzo have now been made in 13 villages involving nearly 10000 people in Kwango District, Bandundu Province DRC, funded by AusAID, but this support has ceased. We are greatly in need of financial support to continue this work.

We believe that the wetting method should be widely adopted by public health authorities in those countries in Africa that use cassava flour as a food source (Bradbury et al., 2015).