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Konzo is a form of food-borne illness. The cassava plant forms part of the diet of people in certain countries in Africa, but the plant naturally contains cyanide. When improperly processed, the cyanide content can cause permanent leg paralysis and other symptoms that are indicative of konzo.
The roots of the cassava plant are the edible parts, and people in places like Tanzania, the Democratic Republic of Congo, and Mozambique grind up the roots into cassava flour. From this flour, they make a porridge, which is known as ugali. Traditional processing methods of cassava remove cyanide content.
In situations where food is scarce due to drought, cassava is an important source of energy, as the plant is resistant to low water availability. Hunger may also encourage cooks to cut corners in processing the cassava. Konzo risk can also be heightened in times of drought as the concentration of cyanide in the roots can increase.
Cyanide poisoning can be lethal. It can also cause diarrhea and vomiting, along with headaches and dizziness. The form of cyanide poisoning that konzo takes is a permanent paralysis of the legs due to damage to the motor neurons of the central nervous system. Other symptoms may also be present.
Paralysis appears a few weeks after the person eats cassava with a high cyanide content. He or she may also experience problems with vision or difficulties speaking or moving the arms and hands. The legs may also feel tingly and the feet cold. Some symptoms may improve over time, with a risk of relapsing episodes, but the paralysis is permanent. Konzo patients, may, however, be able to walk with the help of crutches.
One illness that may be confused with konzo is Tropical Spastic Paraparesis. It causes a similar paralyzing condition but has no relation to cassava ingestion. It is actually caused by the T-cell lymphotrophic virus type 1 (HTLV-1).
A form of processing that reduces the cyanide content of cassava efficiently is promoted by the Cassava Cyanide Diseases & Neurolathyrism Network (CCDNN) in Africa. This processing involves the addition of water to the cassava and leaving it spread out in a thin layer for two hours in the sun, or five hours out of the sun, before using it to make cassava porridge. The cyanide in the plant evaporates off as hydrogen cyanide gas, after which the CCDNN says the cassava is then fit to eat.