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Eighty Kenyans have succumbed to aflatoxin poisoning in Makueni, Kitui, Mbeere and Thika districts, but few know exactly what it is.
Aflatoxins are extremely poisonous to humans and livestock. However, because they are odourless, tasteless and colourless, they are difficult to detect. Maize is especially infected when stressed under such conditions as drought, but sorghum, groundnuts and cotton are also at risk.
Aflatoxins are poisonous by-products from soil-borne fungus Aspergillus, which is responsible for the decomposition of plant materials. And their consumption by humans results in a disease called aflatoxicosis.
Aflatoxin is a naturally occurring fungal toxin produced by two types of mould – Aspergillus flavus and Aspergillus parasiticus. The former is common and widespread in nature and is most often found when certain grains are grown under stressful conditions such as drought.
It is a poisonous mould that grows mostly on cereals harvested or stored under damp conditions, says Nairobi food technologist Jane Ngigi.
She says that maize contaminated by aflatoxins has some black coloration, is bitter and has an offensive smell.
Aflatoxin poisoning is characterised by vomiting, abdominal pain, swelling of the lungs, convulsions, coma and death from the swelling of the brain, the liver, the kidneys and the heart.
The districts involved have experienced grain shortages, which often leads to using grain from other areas. Prolonged storage enhances the growth of the moulds.
The mould occurs in the soil, decaying vegetation, hay and grains undergoing microbiological deterioration.
Favourable conditions include a high moisture content and high temperatures. At least 13 different types of aflatoxin are produced in nature, with aflatoxin B1 considered the most toxic.
The presence of Aspergillus flavus does not always indicate harmful levels of aflatoxin, but this does not mean that the potential for aflatoxin production is present.
Aflatoxins are acutely toxic and have been shown to be carcinogenic in some animals.
All living organisms metabolise aflatoxins in the liver, but high concentrations can lead to acute liver disease or death within 72 hours. Lower aflatoxin concentrations result in various symptoms, including bleeding in muscles and suppression of the immune system.
Accumulation of aflatoxins depends on weather conditions. A dry growing environment or drought tends to favour the development of aflatoxins in maize. When soil moisture is below normal and temperatures are high, the number of Aspergillus spores in the air increases.
During pollination, these spores infect maize kernels through either pollination tubes or areas of damage caused by insects, birds and weather.
There is no procedure for eliminating an aflatoxin after it is produced, but irrigation has been shown to reduce the levels of Aspergillus infection when carried out during pollination.
Harvesting maize early when moisture is above 20 per cent and then quickly drying it to a moisture level of at least 15 per cent will also keep the Aspergillus fungus from completing its life cycle, resulting in lower aflatoxin concentrations. The addition of ammonia to aflatoxin-contaminated grain stabilises the level of concentration, but does not eliminate the problem.
Eating grain contaminated with any level of aflatoxin carries a considerable amount of risk. Therefore, testing for aflatoxin concentrations should be the first step in reducing the risk of poisoning. | 
