Aflatoxins

Aflatoxin is a poison produced by the ubiquitous fungus Aspergillus flavus that infects various crops in the fields and stores making food and feed unsafe. Women, children and the poor are most vulnerable to food made unsafe by aflatoxins. Aflatoxin contamination is pervasive in the food and feed production systems in sub-Saharan Africa leading to unknown but significant social and economic cost with respect to impaired health and productivity of people and animals, increased food spoilage, and inability to market agricultural products internationally.

Aflatoxins are potent human carcinogens and have great acute toxicity causing death. It is also reported to be associated with stunting in children and suppression of immune system. The extent of aflatoxin contamination is high in food and feed in sub-Saharan Africa. The population is exposed to unacceptable aflatoxin levels throughout their lives including prenatal exposure of the fetus and the consequences have been largely ignored. Poultry and fish are particularly vulnerable to aflatoxins and their productivity is significantly curtailed.

Aflatoxins are regulated at parts per billion (ppb) levels ranging from 4 ppb for processed food in Europe to 300 ppb in finisher beef cattle feed in the US. Exported goods have to comply with food safety and quality requirements of importing countries, and quality plays an important role in increasing trade volumes and assuring the competitiveness of African food products in markets. In countries with widespread aflatoxin occurrence, best quality foods are exported and poor quality foods are consumed locally, harming the health of local people.

A study estimated that crop losses (corn, wheat, and peanuts) from mycotoxin contamination in the United States amount to $932 million annually, in addition to losses averaging $466 million annually from regulatory enforcement, testing, and other quality control measures.

Compliance to meet aflatoxin standard is a worthwhile investment. In Senegal, a World Bank has been estimated that US$ 4.1 million added capital investment cost and 15% recurring cost would attract 30% price differential to groundnut oil cake. Export would increase from 25,000 tons to 210,000 tons. Increased export volume and price differential would annually add $281 million value to groundnut export for the capital investment. For confectionary groundnut, adherence to Good Management Practices would increase export value by US$ 45 million annually.

Aspergillus flavus infects the crops in the field and the fungus is carried from the field to the stores. Aflatoxins form both in the field and in storage in maize and groundnuts. High temperature and drought induced plant stress, further aggravated by climate change, accentuates aflatoxin contamination. Insect damage is a significant predisposing factor for entry and colonization of grains by Aspergillus. Wet or moist conditions at and after harvest and during storage increase grain colonization and aflatoxin production.

Visual inspection cannot provide a good estimate of aflatoxins since clean-looking grains are often contaminated by aflatoxins. Chemical analysis of crop products is the most reliable way to determine the level of aflatoxins in food and feeds. Several methods, from simple Thin Layer Chromatography to sophisticated LC-MS/MS, are available for analysis of aflatoxins, but sampling prior to analysis must be appropriate to obtain accurate and reliable data.

There are various methods to control aflatoxins from field to fork. These include good practices before harvest (e.g., use of stress and aflatoxin tolerant cultivars wherever available, irrigation and water conservation practices, management of insect pests that predispose grains to Aspergillus colonization and aflatoxin contamination), at (timely harvest) and after harvest (avoiding direct contact of grains with soil after harvest, rapid grain drying to safe levels for minimizing fungal colonization and sorting), and during storage (moisture and insect proof). Certain dietary practices have been recommended but are not practical at smallholder level.

Biological control is a practical and effective method of reducing aflatoxin in the field.

unaffected chickensaffected chickenBirds raised with feed containing aflatoxins (bottom) had 40% live weight than bird fed on a diet without aflatoxin (top).