July 30, 2007 African farmers and agriculture enterprises now have a fast and inexpensive way to detect and manage a costly, naturally occurring and potentially deadly poison (aflatoxin) that infects their crops via a common fungus that makes them unfit for consumption or export.
Scientists at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), supported by the Consultative Group on International Agricultural Research (CGIAR), have devised a fast, simple and affordable test kit for detecting the poison, which is known as aflatoxin. Aflatoxin is produced by a fungus that can easily grow on many crops including common food crops like maize, groundnut, sorghum, and cassava. It can infect them both in the field and after harvest, while they are being stored in grain bins and elevators.
Many countries reject agriculture imports exceeding certain levels of aflatoxin, costing African farmers millions of dollars each year in lost sales. Meanwhile, people who inadvertently consume a large quantity of the contaminated food can get very sick, as the toxin can cause potentially fatal problems in the liver and intestines. For example, in 2004, 300 people in Kenya were sickened by aflatoxin and 125 people died. Even consuming lower quantities can, over the long term, cause cancer.
Since the aflatoxin contamination is invisible in commodities, the key is detection. In developed countries, farmers routinely use detection technologies to manage outbreaks. But in developing countries, the tests have in the past been too expensive and too difficult for most farmers to implement. The new detection kit developed by ICRISAT has changed the situation by cutting the cost of testing crops from US$25 to $1 per sample. It's available as a small, simple kit that can be used even for most remote rural farms to monitor grains and nuts and improve storage techniques to avoid serious contaminations. The end result is safer products for consumers and higher returns for African farmers.
"We have put another strong weapon in the hands of poor farmers to fight a problem that was making it particularly hard for African agricultural products to get fair treatment in international markets," said Dr. William Dar, director general of ICRISAT.
The test uses what scientists call an enzyme-linked immunosorbent assay or ELISA test to rapidly detect the presence of aflatoxin.
In Malawi, which saw its status in the 1970s as a major groundnut exporter eroded by aflatoxin outbreaks, the National Small Farmer Association of Malawi (NASFAM) has successfully used the new aflatoxin detection kit as part of a broader effort to regain and re-establish itself with its once-lucrative European export markets. Several years ago, there were fears that new standards in developed countries for acceptable levels of aflatoxins in groundnuts could cost African countries $670 million in lost exports.
"Testing groundnuts has worked as a monitoring tool to ensure that buyers do not get produce with higher aflatoxin concentrations than their market requirements or specifications," says Moses Siambi, an ICRISAT scientist based in Lilongwe. "We've seen a very positive impact. Malawian groundnuts are now available on the Fair Trade market and also in some of the biggest supermarkets in the UK."
Aflatoxin is the toxic waste product of two fungi, Aspergillus flavus and Aspergillus parasiticus, which occur naturally in air and soil. They especially infect crops weakened by droughts, when pest activity is higher. Poor harvest and post-harvest handling techniques open up another route for contamination. Storage of grains and nuts before they are properly dry, or in damp conditions, also creates an opportunity for contamination.
Several CGIAR-supported centres, including ICRISAT, the International Maize and Wheat Improvement Center (often referred to by its Spanish language acronym CIMMYT), and the International Institute of Tropical Agriculture (IITA), are putting into place a range of innovative practices to combat aflatoxin contamination in maize, groundnut, sorghum, cassava, pistachio, almonds, and chilli peppers. In addition to the detection test, the techniques include efforts to control the toxin using bacteria as a bio-control agent, breeding crops that are resistant to aflatoxin, and changing cultivation practices to limit opportunities for contaminations.
For example, recent field trials led by Dr Ranajit Bandyopadhyay, an IITA plant pathologist, have employed strains of atoxigenic Aspergillus to eliminate their highly toxic relatives, and in doing so to reduce aflatoxins. "The atoxigenic strains were able to reduce aflatoxin contamination by up to 99.8% in field trials," says Ranajit.
More than 5 billion people in developing countries are constantly exposed to aflatoxins by unknowingly consuming contaminated foods. So reducing aflatoxin contamination of African crops could offer considerable health benefits, particularly to African children.
Rodomiro Ortiz, a plant geneticist at CIMMYT, says, "Children exposed to aflatoxin can suffer from poor growth and immune suppression, making them susceptible to HIV and malaria." CIMMYT researchers have been working at combining biotic and abiotic stress resistance to identify stress-tolerant maize lines or hybrids that have a reduced incidence of A. flavus. This approach to reducing mycotoxin load has been successful. Now the efforts aim to breed maize source populations and synthetics against the maize weevil and larger grain borer, which further serve as vectors and create portals of entry for fungi.
Since the problem is a complex one, ICRISAT is developing resistant groundnut cultivars through breeding and biotechnological methods. Trials on an integrated management approach using bio-control agents, application of calcium, and farmyard manure, showed a 99 percent reduction in aflatoxin, says Farid Waliyar.
The CGIAR Centers have also established strong linkages with several universities and advanced research institutions in several developed countries to bring a long term solution to combat aflatoxins.
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