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How to stop a deadly fungus affecting billions

Scientists at an ILRI lab in Nairobi
(Kenneth Odiwuor/IRIN)

The UN World Health Organization (WHO) estimates that billions of people in the developing world are chronically exposed to aflatoxin, a natural poison on food crops which causes cancer, impairs the immune system, inhibits growth, and causes liver disease as well as death in both humans and animals.

According to the International Food Policy Research Institute (IFPRI) aflatoxins contaminate one-quarter of the global food supply and over half the world’s population; 4.5 billion people are exposed to high, unmonitored levels, primarily in developing countries. In sub-Saharan African alone, an estimated 26,000 people die annually of liver cancer associated with aflatoxin exposure.

Aflatoxins not only pose serious health risks, but are believed to be detrimental to efforts to improve food security and international food trade.

According to the UN Food and Agricultural Organization (FAO), an estimated 25 percent of the world’s food crops are affected by aflatoxins.

This briefing looks at some of the efforts to combat aflatoxins, as well as the remaining challenges.

What are aflatoxins?

Aflatoxins are a naturally occurring carcinogenic by-product of common fungi on grains and other crops, particularly maize and groundnuts. They are a kind of mycotoxin, a highly toxic product of moulds that occurs on almost all agricultural commodities worldwide.

Aflatoxins are one of the most potent naturally occurring toxic substances; they are produced by fungi known as Aspergillus flavus.

Aflatoxin is not always obvious, and even grains that appear normal could actually be infested with high levels of the toxin-producing fungus, which thrives under poor storage conditions.

While the presence of moulds might be an indicator of the toxin, “it is a highly imperfect indicator of aflatoxin contamination,” according to the Consultative Group on International Agricultural Research.

The occurrence of aflatoxins is largely dependent on “geographic location, agricultural and agronomic practices, and pre- and post-harvest handling. If crop drying is delayed or storage is not properly handled, the effects can be greater, with insect and rodent infestations facilitating the invasion of fungal-producing aflatoxins and contaminating stored products.”

Which foods are most susceptible to aflatoxin contamination?

A variety of foods are susceptible to aflatoxin contamination, including maize, peanuts and tree nuts.

According to IFPRI, “Maize and peanuts are the main sources of human exposure to aflatoxin because they are so highly consumed worldwide.” Unfortunately, they are “the most susceptible crops to aflatoxin contamination.”

According to Gro Intelligence, an agricultural data and analytics company, “Maize and nuts are more susceptible to toxin contamination because they grow in climatic conditions suitable for the growth of aflatoxins-causing agents.”

Animal products such as milk and cheese, as well as cottonseed, spices and some feeds, are also prone to contamination from aflatoxins.

According to Johanna Lindahl, an epidemiologist at the International Livestock Research Institute (ILRI), “Very few know about the harm aflatoxins have on animals or even that animal food products can be contaminated with it as well.”

For instance, a study carried out in Nairobi by ILRI revealed that only 50 percent of those who had heard about aflatoxins believed it could be present in milk.

ILRI’s Lindahl, however, told IRIN that “milk and other dairy products can add to the total exposure of aflatoxin in humans,” and that it is necessary to accurately assess the risks.

Increased urbanization, coupled with an upsurge in urban livestock rearing, could increase the vulnerability of animals and animal products to aflatoxin contamination, said Lindahl.

What are the main health risks?

When food crops are colonized by the fungi that produce aflatoxins in the field or during storage, they are rendered unsafe both for human and livestock consumption.

In Africa, where aflatoxin contamination is most widespread, it “is a major cause of post-harvest losses and constitutes a significant threat to food security and livelihoods. It also poses a major public health challenge to consumers all over the continent,” says a US government food security programme.

Acute exposure to high levels of aflatoxins leads to aflatoxicosis, which can result in rapid death from liver failure.

According to IFPRI, “Aflatoxins pose both acute and chronic risks to health. Exposure to aflatoxins is particularly high for low-income populations in the tropics that consume relatively large quantities of staples such as maize or groundnuts. Consumption of very high levels of aflatoxins can result in acute illness and death, as observed in Kenya in recent years.”

Aflatoxin contamination has also been associated with childhood stunting.

Erastus Kangethe, food safety expert at the University of Nairobi, told IRIN, “It would be detrimental to ignore the long-term effects of aflatoxin, because unless we can control it, then we are going to witness a generation of stunted population very soon.”

Its effect on commerce is equally devastating. Globally, about US$1.2 billion in commerce is lost annually to aflatoxin. African economies lose about $450 million worth of crops to it each year.

According to Davesh Roy, a research fellow in the markets, trade and institutions division of IFPRI, standards on acceptable levels of aflatoxin in food crops set by the European Union “remain a potentially important barrier to trade, and meeting them is a necessary, but not sufficient, condition for market access for many exporters in low-income countries.”

According to the World Bank, “The EU’s tightening of the Maximum Allowable Levels (MALs) of aflatoxins to four parts per billion cost African countries $670 million in annual export losses of cereals, dried fruits, and nuts.”

Experts say that toxin contamination causes other losses as well, “including reduced yields, lower crop values and a decline in animal productivity”.

What efforts are being used to control toxin contamination?

In 2011, the US government, through its global hunger and food security initiative, announced in Lusaka, Zambia, that it was committing an estimated $12 million to support an African-led aflatoxin control programme. A year later, the African Union Commission announced the formation of the Partnership for Aflatoxin Control in Africa to spearhead toxin contamination control programmes on the continent.

There are bio-control studies taking place in various African countries to help combat aflatoxin contamination in crops and animal products. Biological methods such as aflasafe - a biological control agent against aflatoxins - have shown to be effective.

In Nigeria, where field testing of aflasafe has already been done, Charity Mutegi, a scientist at the International Institute for Tropical Agriculture (IITA), told IRIN, “The efficacy results have been very positive. Aflatoxin contamination was reduced by between 80 to 90 percent both in maize and in groundnuts.”

According to the International Maize and Wheat Improvement Centre (CIMMYT), “Aflasafe works by ‘pushing out’ harmful, toxin-producing strains of A. flavus (the aflatoxin-causing fungi) from the field, through the deliberate introduction of indigenous but non-toxic, harmless strains - a process known as ‘competitive exclusion’.”

Apart from Nigeria, other African countries carrying out bio-control research include Burkina Faso, Ghana, Kenya, Mali, Senegal, Tanzania, and Zambia. Already, aflatoxin bio-control laboratory infrastructure has been created in Burkina Faso, Kenya and Zambia.

CIMMYT is working on double-haploid (DH) technology “to rapidly develop inbred lines combining A. flavus and aflatoxin-resistance with other important agronomic traits. These DH lines are now being evaluated to identify new superior lines combining aflatoxin resistance, drought and heat tolerance, and good agronomic performance.”

IFPRI says, “Because aflatoxins are a pervasive environmental risk, control will require a multifaceted approach. Many different efforts will be required to move toward higher quality food and reduced food safety risk.”

In some countries such as Kenya, measures like the introduction of metal silos are being promoted to help farmers with the storage of their farm produce.

Recently, scientists have developed a smart phone-based technology to help farmers detect aflatoxins. The application measures the level of aflatoxin contamination in a phone image by studying the change in color strips on affected crops. The technology can be used anywhere.

According to Mobile Assay, the company that developed the technology, “Software allows anyone with a camera equipped device to take an image of a Rapid Diagnostic Test Strip and get back instant quantifiable results.”

What challenges exist in controlling aflatoxins?

The lack of knowledge about aflatoxin detection among smallholders and the absence of widely available detection tools remain some of the biggest challenges in the control of aflatoxins.

Many African countries lack “enhanced post-harvest handling facilities such as warehouses, processing plants and information systems to address the problem,” according to the Gro company.

IITA’s Mutegi says, “Gathering data to meet the bio-control regulatory requirements is always expensive.”

Experts have recommended more investments in scientific research to develop aflatoxin-resistant crop varieties, and say there is a need to create awareness among farmers about its dangers and how to detect the fungal poison.

Experts believe overreliance on aflatoxin-prone food crops such as maize and ground nuts has also made the toxin difficult to control, and they are calling on farmers to diversify to non-susceptible food crops.


This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions

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