ProMEDmail, 12/3/07:  Most of the 45 000 Central African Republic (CAR) refugees living in
eastern Cameroon are diseased, malnourished, and generally in bad
health, non-governmental organisation (NGO) and UN workers say.

The refugees arrive “very weakened, after long days of walking and a
lot of stress and they live in very difficult conditions,” Eric
Grimaldi of Medecins Sans Frontieres (MSF) told IRIN. Once settled in
some 60 villages in eastern Cameroon, their health does not improve
significantly. For every 10 000 people, there are between 3 and 7
deaths per day among the refugees. According to MSF, the situation is
particularly bad in the village of Ngaoui in Adamaoua Province, home
to 5000 refugees and receiving 100 new refugees a month.

According to the UN Children’s Fund (UNICEF), 17.2 percent of refugee
children under 5 are malnourished. MSF has registered several cases
of tuberculosis and about 50 cases of a rare paralytic disease called
“konzo.” Known as “the disease of the poor,” it results from
exclusive consumption of the bitter manioc plant, which, though
inexpensive, is poor in vitamins and nutrients.

 Cassava marketplace

Manioc also contains salt cyanide, which can be toxic if improperly
cooked. The result can be irreversible paralysis of the lower limbs,
as well as hearing and sight problems.

“We have met families where several children are now paralysed,”
MSF’s Grimaldi said, adding that the Cameroonian authorities do not
have the material or human resources to prevent the disease and very
few doctors know how to treat it.

The nutritional situation was “so alarming” according to MSF, that in
July [2007] the UN Refugee Agency (UNHCR), the World Food Programme
(WFP), MSF, and another aid agency, CARE, in collaboration with the
Cameroonian Public Health Ministry, began monthly food distributions.

[Some of the following regarding konzo was derived from
:

Konzo is characterized by an acute isolated and symmetrical
hypertonic paraparesis, which is permanent but non-progressive. To
date, 2 large epidemics have been reported, each of more than 1000
cases. The 1st was in the Bandundu region in Congo (1936-37) and the
2nd in the Nampulla province of Mozambique (1981). Small outbreaks
have been reported from Congo, Mozambique, Tanzania, and the Central
African Republic. Sporadic cases of konzo also occur. The majority of
cases of konzo occur in the dry season, chiefly during a long
drought. Familial clustering is common.

Cassava (_Manihot esculenta_, Crantz) is a root crop widely consumed
in Africa and South America. Although it originated in Brazil (where
it is called manioc), it was brought to Africa by Portuguese
colonists, and it is now an important crop there and in Indonesia and
Southeast Asia. It is the principal source of nutrition for about 500
million people. Its leaves are edible, but the prize is its starchy
root, rich in protein, minerals, and vitamins A, B, and C.

Cassava is used in a vast variety of cakes, snacks, and desserts and
grows wild in many places, being tough and drought-resistant. In
countries where hunger is an overt reality for many poor households,
cassava is among those food crops that can make the crucial
difference between starvation and survival. The cassava plant is the
world’s 3rd most important crop. Cassava enters the North American
diet also, as it is made into tapioca.

Surprising for an important edible plant, cassava is quite poisonous
without proper preparation. The toxin in cassava is called linamarin.
When eaten raw or inadequately prepared, the human digestive system
will convert this to cyanide. Even 2 cassava roots contain a fatal
dose of poison. While the bitter variety (white cassava) of the plant
has larger concentrations of cyanide than the sweet variety (yellow
cassava), the sweet cassava is not without risk.

To prepare cassava, it should be peeled, grated, and soaked in warm
water for several days. This allows the cassava’s own natural enzyme
(linamarase) to convert the cyanogen linamarin to sugar and cyanide
gas, and the volatile gas disperses usually harmlessly. However,
women — who are usually charged with processing the plant — can be
sickened by inhaling cyanide gas. What remains after processing can
be boiled and eaten, or more usually, dried and ground.

The shelf life of a cassava root is quite short once it is removed
from the stem, so there is an urgency to get the food to market.
Roots can turn to mush in less than a week. The rush to get cassava
to the market may keep some batches of cassava from being processed properly.

Cyanide is normally converted in humans to the less toxic thiocyanate
by the enzyme rhodanase, a mitochondrial enzyme which is widely
present throughout the human body, with the highest concentrations in
the liver and kidneys. Thiocyanate is the chief metabolite of
cyanide. Thiocyanate itself has a goitrogenic effect if there is a
shortage of iodine in the diet. The body uses sulphur-containing
amino acids to render cyanide harmless. If the diet is deficient in
protein, cyanide will be converted to cyanate, which induces
neurodegenerative disease in both animals and humans. The cells which
are most affected are Betz cells in the motor cortex. Tropical ataxic
neuropathy can also be produced.

Konzo begins abruptly, without prodromal signs. In 90 percent of
cases the onset of symptoms takes less than a day. The initial
symptoms are described as tremor, cramps, a heavy feeling, and/or
weakness in the legs, a tendency to fall down, and difficulty
remaining upright. There is a visible hypertonic gait when walking or
running. Occasionally there will be lower back pain, blurred vision,
speech difficulties, and/or paresthesia of the legs, but they
disappear within a month. During the 1st 2 days the majority of
patients have general muscular weakness and are confined to bed.
Hypertonicity is present from day one. Flaccid paralysis of the limbs
does not occur. Later there is a slight partial improvement. Finally
the affected person develops a stable hypertonic paraparesis, which
persists for the remainder of life, or might improve a little. After
onset the neurological signs remain constant or improve minimally if
no further cyanide is ingested.

Prevention of konzo therefore involves avoiding a farming system
dominated by bitter cassava (which contains higher cyanide levels),
insufficient cassava processing, and a protein deficient diet.

In an effort to avoid this toxicity, it has been reported by
Siritunga and Sayre (1) that transgenic cassava free of cyanogens can
be produced. The investigators generated transgenic plants in which
cytochrome oxidase enzymes that catalyze the 1st step in linamarin
synthesis are inhibited. The plants showed a 94 percent reduction in
leaf linamarin content and a 99-percent decrease in root linamarin
levels. Additionally, the same group (2) has reported that transgenic
cassava plants can be produced that overexpress the gene for
hydroxynitrile lyase, facilitating cyanogenesis during processing and
producing a final product with less risk. The tubers of cassava do
not have this enzyme, and processing relies on spontaneous
conversion. Combining these methods could further decrease the risk
of cyanide poisoning from cassava.

References:
1. Siritunga D, Sayre RT: Generation of cyanogen-free transgenic
cassava. Planta 2003; 217:367-73.

2. Siritunga D, Arias-Garzon D, White W, Sayre RT: Over-expression of
hydroxynitrile lyase in transgenic cassava roots accelerates
cyanogenesis and food detoxification. Plant Biotechnol 2004; 2: 37-43. – Mod.LL