Aflatoxins, major contributions to harvest loss - what do we know and not know?

In high-income countries, contamination of crops pre or post-harvest with mycotoxin-producing fungi cause substantial financial losses, with mega-tons of crops every year exceeding the allowed limits and therefore being disregarded as human and animal food. It is estimated that applying the US and the EU regulatory limits to corn would cause losses of 40 to 124 million USD respectively, only in the three most important corn exporting countries. To this is added costs of destroying crop, which may amount to 50% of the corn harvest in some years. In low-income countries, limited food resources and lack of awareness, prevents many smallholders from discarding damaged, and infected food products. A climate that promotes fungal growth and suboptimal storage procedures contribute to the extensive aflatoxin contamination in these countries. Aflatoxins are mycotoxins produced by Aspergillus fungi, mainly Aspergillus flavus and Aspergillus parasiticus. These toxins are capable of causing acute poisoning, which has been the case in Kenya, where outbreaks has caused hundreds of fatalities. However, the large outbreaks are not the biggest concern for aflatoxins. Aflatoxins are potent carcinogens and cause hepatocellular carcinoma, especially in association with hepatitis B virus infections. The annual number of fatal cases of liver cancer attributed to this reaches ten thousands of cases. In addition to this, scientists have found associations between chronic aflatoxin exposure and childhood stunting. Since aflatoxins are metabolized in the body after consumption of contaminated food, and excreted in milk as a metabolite, there is a fear that children fed on breast milk, and then weaned on cereal-based food and dairy products, are at a high risk of chronic early exposure. At the International Livestock Research Institute in Nairobi, Kenya, a number of projects regarding aflatoxins are on-going, with special focus on dairy products. In one of these, a risk mapping exercise was undertaken to create a basis for finding high and low risk areas, and participatory rural appraisals were carried out in different villages, in order to comprehend the knowledge, attitudes and practices of farmers. The next step is to develop a framework for assessing the risks of aflatoxins and the economic costs, with special focus on the dairy production chain. In the participatory rural appraisal almost all farmer groups reported maize getting spoiled, and 31 out of 54 groups sometimes gave this maize to the cows. All groups stated that eating mouldy feed is harmful to humans, but only 48 out of 54 believed it was harmful to animals. Results of the risk mapping exercise showed that much basic data on risk food consumption was lacking for risk maps to be reliable. Since outbreaks of acute aflatoxicosis are much more notable than chronic exposure, reports of clinical cases are mainly based on these, and adding historical outbreaks to a risk map may do little to predict chronic exposure. The conclusions are that much more basic data is needed in order to create a complete risk assessment and predictive maps, and to fully understand the impact.