By Prof. Dr. Sampson Binyason
It is sad to learn from the Article “Cassava leaves kill two in a family,” published in No. 1, Citizen Daily Newspaper, issue 929, Vol. 4, page 3, of July 24, 2023. The incident occurred in Barmayen Payam, Aweil Centre County, Northern Bahr El Ghazal State.
According to Lino Panjaap, Medical Officer, the deceased Aweng Ayok Deng and her son “ate the half-cooked cassava leaves as they lacked any other food to survive on, which was claimed as the cause of their demise and probably was the medical report. However, diagnostically, with a critical look at the cassava plant leaves shown in the picture, they tend to exhibit luxuriant growth of palmate turgid and a healthy appearance, with no common symptoms of any insect damage.
A typical characteristic of plants rich with preventive or toxic elements that usually pose natural resistance to an assault, such as cyanide acid. The deaths of Aweng Ayok and her son were most probably due to Cassava cyanide poisoning, as speculated. Hydrogen Cyanide, sometimes called prussic acid (HCN), is commonly found in the leaves, stems, and roots of cassava varieties.
There are two groups of cassava, the sweet and the bitter, with varying levels of hydrogen cyanide acid. HCN is colorless and extremely poisonous. It partially ionizes water. Cassava toxicity may be Acute or Chronic. Acute toxicity results from indigestion of the lethal dose and death is caused by the inhibition of cytochrome oxidase of the respiratory chain by the cyanide.
Death, therefore, comes when the cyanide level exceeds the limit and an individual is not able to detoxify. Acute cyanide poisoning for humans is between 0.5 and 3.5 mg/kg of body weight. Children are particularly at risk because of their smaller bodies. And this is what probably caused the deaths of Aweng Ayok and her son. The level of cyanide might have exceeded the levels above, and hence the leaves were not thoroughly cooked to expel most of the toxicity.
On the other hand, chronic cyanide intoxication may lead to the development of certain conditions, including disturbances of thyroid functions and neurological disorders that eventually result in death. The cyanide poison tends to affect those individuals who have regular, long-term consumption of cassava and poor nutritional status. The husband of Aweng Ayak was also affected in the same way by the cyanide poisoning, but his body seemed to show some resistance by detoxifying it, or probably the level taken was below the limits mentioned, and I hope he has recovered. That saved him.
The known symptoms of cassava poisoning are rapid respiration, drop in blood pressure, rapid pulse, dizziness, stomach pain, and headache.
Lino Panjaap, the medical officer, might have observed some of the symptoms. As a common experience among people living in the Green Belt Zone (the native home of cassava). Cassava leaves are a special diet of the people and are eaten on a daily basis, for instance, in areas of Yambio, Tombora, Yei, Maridi, Western Bahr El-Gazal, and even now, cassava leaves are abundant in Juba markets as one of the most liked vegetables.
It is cooked in different styles with ingredients like palm oil, “Dakua” (peanut paste), and appetite-inducing (very delicious) The people in these areas usually plug leaves of sweet cassava and not of bitter cassava. When cooked with palm oil or any of the ingredients, the source is known as “Gadia in Zande and “Pundu” in Bari.
The leaves of bitter cassava, Karanbgwa,” are not cooked because of the known poisoning effect. For the cassava tubers, those of the sweet varieties can be eaten fresh or boiled, while those of the bitter varieties are peeled, shocked in water, or ratted to ferment for 3–4 days, washed, dried, and made into flooring to avoid the poisoning effect.
They cannot be eaten fresh before the procedures mentioned to avoid poisoning. What had happened in Barmayen Payam appears to be that the cassava crop has been recently introduced to the Payam in Aweil, and not many women know what variety of leaves are to be cooked. Otherwise, Aweng should have known how cassava leaves were usually cooked.
It appears she has no experience with what types of cassava leaves are cooked but knows or has probably heard that cassava leaves are edible and was compelled by hunger to have something to cook and eat.
What should have happened when introducing a new crop variety into a locality is that the researcher and extension personnel should start with demonstration plots to propagate the variety or varieties in collaboration with the local community.
The local community then learns how to grow it or them, what variety parts are eaten, how to prepare them for cooking, the taste of the varieties, and whether the people accept or dislike the variety or varieties.
This basic information is very vital to the researchers, scientists, and extension personnel and gives a full information package for growing and cooking the cassava varieties. It also gives awareness to the farmers and the entire community to know that there are two groups of cassava: sweet cassava and bitter cassava.
The experts should demonstrate to them how to grow and prepare cassava as food, whether fresh, boiled, or cooked. And how to harmonize the bitter varieties with high levels of hydrogen cyanide when processing them for food, especially the leaves and tubers.
As a National Volunteer Research Consultant, I wish to have the following information sent to me by any volunteer from the area of the incident: 1. Name of the cassava variety or varieties 2. Origin of the variety or varieties 3. Pictures or photos of cassava plants, leaves, and tubers, 4.
If possible, put portions of leaves, stems, and tubers of each variety into polythene or nylon bags for analysis and identification purposes through some regional and international Research Institutions in collaboration with the volunteer.
In 1982, seven local cassava varieties, including some Nigerian varieties under propagation, were sent for hydrogen cyanide analysis from Yambio Research Station to Shambat Research Station, Department of Food Technology of the Agricultural Research Corporation (ARC), Wad Medani. Professor Dr. Paul Lado Bureng, the former Head of Food Technology who is currently around, speedily sent back the results of the analysis with the variety Karanbgwa, predominantly a bitter variety.
This work of food analysis can be easily done here in Juba if we have a good, functional, established research Institution with a well-equipped biolaboratory. There are trained graduates who can do the job; unfortunately, they are not cared for. We just need a functional research facility with a good biolaboratory for some of these graduates to volunteer to work in and help recuperate the plight of the nation.
Finally, I hope the husband of the late Aweng has fully recovered. My condolences to the family of the late Aweng Ayok and his son. May their souls rest in eternal peace! Amen.
The writer is a Private National Volunteer Research Consultant-Munuki Juba. He can be reached via Email: sampsonalai@gmail.com; Phones:+211924543460/211917924674