Aflatoxins: detecting the danger
A simple, cost-effective, tool which analyses and estimates aflatoxins
in foods and feeds has been developed to help reduce the risks to human
health and to promote the potential of high value export crops, such as
nuts, in developing countries. Trade restrictions on contaminated food
or feeds have the greatest effect on those countries which currently have
limited, or no available means of monitoring aflatoxin levels. The commercial
kits which are available, use analytical methods, but these are time consuming
and expensive: each test sample costs a minimum of US$12. 
However,
ICRISAT is one of several organisations developing cheaper techniques
to detect aflatoxins levels of highly dangerous toxic residues produced
by certain fungi, such as Aspergillus flavus and A.parasiticus,
which especially affect oilseeds, edible nuts and cereals in
subtropical and tropical regions throughout the world.
The toxins are particularly carcinogenic in humans and eating contaminated food often results in liver cancer, amongst other diseases. Liver cancer takes time to develop but the aflatoxins also act an immuno-suppressant so that affected individuals become susceptible to a wide range of diseases. Livestock are also at risk and poultry are particularly susceptible: over 200,000 chickens died in 1994, in Andhra Pradesh, India, after eating contaminated feeds. Cattle are not so susceptible but, if they are fed on contaminated feed, the toxin 'Alflatoxin M' passes into the milk.
Export potential
Besides endangering human health, aflatoxin contamination seriously affects the export potential of high-value commodity crops, such as edible nuts (groundnut, pistachio, cashew and almond) and spices (turmeric and chillies), which could provide an important source of income for farmers in the semi-arid tropics. Pistachio is a particularly important commodity for countries like Iran: more than US$550 million of nuts are exported each year to European countries. Yet exports could be higher if aflatoxin contamination could be avoided. It is hoped that with the transfer of technology for diagnosing, or even preventing, aflatoxin contamination that more subsistence farmers will be able to benefit from increased trade. It will also contribute to an improvement in the general health of people, often the poor, who consume contaminated foods.
Aspergillus antibody kit
ICRISAT has already produced antibodies for aflatoxin B1 found in grain products. "What we have done is to develop inexpensive immuno-chemical based methods which can be adapted to different situations in developing countries," says Dr D.V.R. Reddy, Principal Virology Scientist at ICRISAT. "The process is relatively simple and involves the use of antibodies in an enzyme-linked immuno-sorbent assay and, within four hours, it is possible to produce quantitative results which can be used to estimate the amount of toxin present in the tested sample." The test will be used as the basis for designing practical kits for use at district level by National Agricultural Research Services (NARS), NGOs, food quality professionals and health administrators to ensure safer foods and feeds. Several training courses in these techniques have already been conducted by ICRISAT as part of their aim to transfer this technology to countries in Asia and Africa.
Preventative measures
Prevention is undoubtedly better than cure and avoiding fungal infection is more advisable than trying to combat the problems of aflatoxin contamination. However, climatic factors, crop management and the genetic vulnerability of the plant all play a role in the susceptibility of the crop to Aspergillus. It has been realized therefore, that solutions are best provided through an integrated approach. The consortium of global, regional and national institutions, which are now collaborating in combating this complex problem, demonstrates the significance of aflatoxin contamination.
In Mali, ICRISAT, the Peanut Collaborative Research Support Programme and IER (Institut d'économie rurale) have conducted surveys of groundnut storage practices on-farm in different climatic zones. The results will be used to develop models for predicting and assessing the risk of aflatoxin development under particular conditions. The great majority of farmers have been found to be unaware of the problems of aflatoxin contamination so information dissemination will be critical. Once awareness has increased, preventative measures can be taken. For instance, it is important to avoid drought, particularly just before harvest as this can cause cracking of the groundnut pod, which enables the fungus to get inside the pod and invade the seed. Correct storage after harvest is also important and it is vital that crops are dried to a 'safe' moisture level as quickly as possible.
Further information: http://www.icrisat.org/
Mycotoxins - the silent threat to human and animal health by R.Coker,
1999, 52pp, ISBN 1861661274
