Konzo, an Epidemic Upper Motor Neuron Disease Studied in Tanzania

Abstract

An epidemic of spastic paraparesis was studied in a drought-affected rural area of Tarime district in northern Tanzania. The uniform clinical findings in 39 cases, aged 4-46 yrs, indicated abrupt symmetric isolated and permanent but not progressive damage to the upper motor neurons. Due to the failure of other food crops, the diet at onset consisted almost exclusively of bitter cassava roots, a drought-tolerant starchy root crop widely cultivated in Africa. The drought increased the natural occurrence of cyanogenic glucosides in the cassava roots, and the processing procedure normally applied in order to remove cyanide before consumption was shortened because of food shortage. The resulting high dietary cyanide exposure was confirmed by very high serum levels of thiocyanate, the detoxification product of cyanide. Tests for HTLV-1 antibodies were negative and no other findings supported an infectious aetiology. The clinical findings and the associations with cassava toxicity are almost identical to those reported from outbreaks of spastic paraparesis in Mozambique and in Zaire, where this disease was first reported under the name 'konzo'. We thus conclude that konzo constitutes a distinct upper motor neuron disease entity, probably caused by a toxic effect from insufficiently processed cassava under adverse dietary circumstances.

Cassava: The Drought, War and Famine Crop in a Changing World

“…Acute intoxication symptoms, which occur within hours of consumption of insufficiently processed cassava, include dizziness, fatigue, headache, nausea and diarrhoea [97]. Too much cyanide over a relatively short time interval (i.e., weeks), and insufficient protein, can cause irreversible spastic paraparesis (i.e., weakness of the legs, [107]) due to upper motor neuron damage, resulting in konzo [47,106]. Interestingly, in South and Central America, where cassava has been cultivated for thousands of years, cassava toxicity is rare and konzo is unknown [25,108,109].…”

Toxic and Metabolic Myelopathies

“…It is characterized by the abrupt onset of spastic non-progressive paraparesis. 69 Years of cassava consumption have also been implicated in a syndrome of slowly progressive ataxia, peripheral neuropathy, and optic atrophy seen in parts of Africa. 1,70 The diagnosis is based on a history of exposure and measurement of serum thiocyanate levels.…”

Health factors associated with persistent konzo in four villages in the Democratic Republic of Congo (DRC)

“…Konzo is a spastic paraparesis that causes irreversible paralysis of the legs mainly in children and young women, associated with intake of large amounts of cyanide from a diet of bitter cassava that also causes malnutrition (Cliff et al, 1985;Howlett et al, 1990;Nzwalo and Cliff, 2011). It is worst in the Democratic Republic of Congo (DRC), also occurs in Mozambique, Tanzania, Cameroon, Central African Republic, Angola and there are reports of its recent spread to Uganda (Diasolua-Ngudi, 2015) and Zambia (Mbewe, 2015).…”