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Aflatoxins – Saving African Food from Contamination

Vongai Musembwa’s eyes light up as she scoops up healthy white grains from a metal bin she uses to store newly harvested maize. Happily, they’re free of a naturally occurring poison — aflatoxin — that can contaminate crops in the field, before or after harvest and during storage.

The metal silo protects the grains from aflatoxin — produced by certain fungi that grow on food crops like maize, millet, sorghum, groundnuts, cassava and rice.

 Farmer, Vongai Musembwa from Makoni District in Zimbabwe stores her maize grain in a metal silo, an effective method in preventing aflatoxin contamination, Photo credit, Busani Bafana


Farmer, Vongai Musembwa from Makoni District in Zimbabwe stores her maize grain in a metal silo, an effective method in preventing aflatoxin contamination, Photo credit, Busani Bafana

Ms. Musembwa is one of more than 260 smallholder farmers in Makoni District, east of Zimbabwe’s capital Harare, who have switched to non-chemical hermetic storage to prevent food from contamination. Musembwa received her metal silo from a local organization, under a multi-partner project seeking to prevent aflatoxins contamination of maize grain.

The Makoni District farmers are participants in a two-year project worth $1.6 million supported by the Cultivate Africa’s Future programme, an initiative funded by Canada’s International Development Research Centre and the Australian Centre for International Agriculture Research. Under the project, Zimbabwean farmers are given access to metal silos and thick plastic “superbags” to determine if improved storage can reduce aflatoxin contamination in local maize grain.

Crops contaminated by aflatoxins develop moulds and acquire a dark colour. Livestock and humans can fall sick or die after eating contaminated food grains. It has also been linked to childhood stunting, liver cancer and immune suppression in adults.

 Scientists warn that extreme weather is increasing the level of health-damaging toxic chemicals in crops, including staple foods which are key to food, nutrition and trade security in Africa. To protect themselves against extreme weather, plants generate aflatoxins, according to the United Nations Environment Programme.

“Aflatoxins are pervasive in African food systems negatively impacting health of women and children, income from agriculture value chains, and food safety and security of nations,” says Ranajit Bandyopadhyay, a senior plant pathologist at the International Institute of Tropical Agriculture (IITA), where he guides research and development activities on crop diseases and poisonous chemicals produced by certain fungi known as mycotoxins.

Bandyopadhyay, said people fall sick, farmers lose income, grains are destroyed, food prices soar, profitability of animal industries declines, reputation of African exports are tainted and nations become less food secure due to aflatoxin contamination.

“Aflatoxin contamination presents a barrier to trade and economic growth and is a serious obstacle to programmes designed to improve nutrition and agricultural production while linking smallholder farmers to markets,” Bandyopadhyay said. “The extent of contamination varies by seasons, crops and regions and can be anywhere from none to 100% and often hovers around 25%.”

Rhoda Peace Tumusiime, the AUC’s commissioner for rural economy and agriculture said curbing the menace of aflatoxin contamination was critical to improving child and maternal nutrition and health as well as achieving Africa’s goal to transform its agriculture.

Farmers are particularly vulnerable to fungal poisons, according to a 2015 baseline study to reduce maize-based aflatoxin contamination and exposure in humans in Zimbabwe by researchers from the University of Zimbabwe and the international humanitarian organization, Action Contre la Faim.

Dr. Loveness Nyanga, the project principal investigator and researcher at the University of Zimbabwe, notes that the high-level of aflatoxin contamination is a public health concern because Zimbabweans eat maize and legumes on a daily basis.

The existence of aflatoxins has other consequences to Africa’s economy. The continent is losing more than $450 million annually when its commodities are rejected on global markets because of high contamination levels, says the Partnership for Aflatoxin Control in Africa (PACA), an initiative of the African Union Commission (AUC) whose aim is to protect crops, livestock and people from the effects of aflatoxins.

The United Nations Food and Agriculture Organization (FAO) confirmed that aflatoxins affect 25% of the world’s food crops and hurt trade. About US$1.2 billion is lost in global commerce annually as a result of aflatoxins, according to IITA. While the International Food Policy Research Institute (IFPRI) notes that the World Food Programme has sharply reduced the quantities of maize it has been able to buy locally in Africa since 2007 because of aflatoxin contamination.

Africa also faces a health burden associated with humans’ exposure to contamination.

Harming our health

An estimated 26,000 people die annually in sub-Saharan Africa from liver cancer resulting from chronic aflatoxin exposure, according to a 2013 research by IFPRI.

Globally, 5% to 30% of all liver cancer cases are linked to aflatoxin exposure, with the highest incidences occurring in Africa, according to the Platform for African-European Partnership on Agricultural Research for Development (PAEPARD), an eight-year project sponsored by the European Commission.

In Mozambique, a high prevalence of liver cancer in southern part of the country has been associated with consumption of aflatoxin contaminated food, especially from groundnuts.

Sustainable solutions

Cultivate Africa’s Future is one of several ongoing efforts to contain aflatoxin contamination. If experiments with the plastic “super bags” are effective against contamination, they will be a highly sought after item by Zimbabwean farmers who lose up to 30% of harvested maize every year to pests and poor post-harvest handling.

More than $50 million worth of maize, the staple food, is lost annually during storage alone, says Ringson Chitsiko, the permanent secretary in Zimbabwe’s ministry of agriculture.

To fight aflatoxins contamination and maintain food quality and safety, scientists recommend an integrated approach, including, among other techniques, timely planting and harvesting, proper plant density and managing insects. This is in addition to crop rotation, shelling, enhancement of proper plant health and nutrition, rapid drying of grains in the sun for days, or with driers to reduce the moisture content and proper storage.

Bandyopadhyay leads Africa-wide efforts on the development and scaling-up of the aflatoxin biocontrol technology known as Aflasafe, a novel biological product developed by the IITA to fight pre-and post-harvest aflatoxin contamination.

Already the IITA has a programme to develop Aflasafe in Malawi where between 40% and 100% of the country’s groundnut-based commodities contain unsafe toxin levels. Aflasafe has also been tested in Burkina Faso, Gambia, Kenya, Nigeria and Senegal since 2009. About 30,000 farmers in Nigeria, Senegal, The Gambia and Kenya are using Aflasafe and getting 200 to 500% return on investment, Bandyopadhyay said.

Tanzania in June 2016 announced that it was undertaking field trials in the use of Alfasafe targeting four regions. A 2012 study in Tanzania established high incidents of aflatoxin contamination in maize and groundnuts in the country.

The Africa Aflatoxin Information Management System platform spearheaded by PACA is creating a “one stop shop” database for aflatoxin-related information in the health, trade and agriculture sectors as a way to raise awareness and prevent contamination.

The Aflasafe product has been registered in Senegal and Gambia where aflatoxin contamination is a major deterrent for groundnut exports. Bandyopadhyay said aflatoxin exposure in humans is rampant in West Africa with the toxin found in the body fluids of 100% Senegalese and The Gambian people in a few instances.

In 2005 the World Bank estimated that investments in aflatoxin control can add $281 million to the Senegalese economy from increased export volume and price differential of aflatoxin-safe crops.

A key impediment is the level of aflatoxin awareness among farmers and consumers. Because of poor policing of food safety standards in many African countries, researchers say that many people eat contaminated foods, especially the staples such as maize, legumes and groundnuts, without checking for signs of aflatoxins.

Researchers at the International Crops Research Institute for the Semi- Arid Tropics (ICRISAT) in  June 2016 announced the decoding of the DNA of the ground nut or peanut (Arachis hypogaea), an oil and protein rich crop of global importance with the annual production of 42.3 million metric tonnes.

Rajeev Varshney, the Research Programme Director- Genetic Gains at ICRISAT said in an online interview that groundnuts, though an important crop in terms of nutrition and income in Asia and Africa, face low productivity as compared to Americas. The current pace of developing improved peanut varieties and their productivity may not be able to meet the demand of ever increasing global population, especially in Asia and Africa where in some countries productivity is less than one tonne per hectare. According to the FAO, the world average productivity of groundnuts is 1, 6 tonnes per hectare.

Varshney said the gene resources generated through this breakthrough provide an opportunity for scientists to prepare an efficient road map for developing improved groundnut varieties with increased productivity and quality.

“Peanuts produced from African countries and India have high level of aflatoxin contamination,” said Varshney. “This makes peanut produce unsuitable for export to Europe and Americas. Therefore it is really important to work in the direction of producing varieties with minimal aflatoxin contamination.”

Manish Pandey, a groundnut genomics Scientist at ICRISAT said the availability of the DNA sequence will accelerate basic research to answer important biological questions about groundnuts and help crop improvement programmes around the world.