Aflatoxin Contamination of Maize in Africa

Aspergillus flavus
Aspergillus flavus seen under an electron microscope. (Credit: Cornell University Dept. of Animal Sciences)

2.3 million bags of maize are contaminated with aflatoxins this year in Kenya, according to afrol News.  Aflatoxins are produced by the Aspergillus species of fungus, most notably Aspergillus flavus and Aspergillus parasiticus, and are highly carcinogenic and damaging to the liver.  This natural outbreak in Kenya has made a large portion of “maize unfit for human and livestock consumption and trade, to the dismay of the millions of small-scale farmers that depend on the crop for food and income.”   Government officials in Kenya are offering to buy the contaminated maize in effort to keep it off the market. Aflatoxin contamination cannot be seen without the aid of UV light, leading some farmers to doubt that their crops are contaminated.  With the aid of a black light, one can see the presence of the B1 and B2 aflatoxins, which fluoresce blue, and the G1 and G2 aflatoxins, which fluoresce green. 

Aspergillus fungi are found throughout the world and can infect a variety of crops, leading to aflatoxin contamination of both human and animal feed.  Aflatoxins have also been investigated for bioweapons use because of the devastating economic effects observed from natural outbreaks.  In the 1990s, the Iraqi government produced at least 2,000 liters of an aflatoxin anti-crop biological weapon.  It was loaded into bombs and field tested, but not used.

Plant pathologists from Africa and the United States are advocating spraying atoxigenic (non-toxin producing) strains of Aspergillus on crops in Kenya to help limit the growth of toxic strains.  Past use of these strains in the US and Africa have been effective in reducing aflatoxin contamination.  In 2009, the use of atoxigenic strains on crops in Nigeria reduced contamination by 80%.  These efforts to control Aspergillus, along with methods to protect other staple crops including cassava, will likely increase food security in Africa in the years to come.

0 thoughts on “Aflatoxin Contamination of Maize in Africa

  1. Couldn’t we use xylitol in the fertilizer or water supply? It is a natural derivative that starves bacteria and fungal agents by virtue of it’s chemical construct.

    1. Michael DesJardins: Interesting idea. But, if xylitol could be used to inhibit Aspergillus growth, it is likely expensive to purchase in large quantities. It would also need multiple applications throughout the growing season. These costs are likely too much for small farmers, or for government subsidization in a developing country. The atoxigenic strains of Aspergillus would only need to be once a year, and not every year. Another benefit of this method is that over time, the toxigenic strains could become less common, benefiting all farmers (and consumers) in the region.
      I couldn’t find the per kg cost of the biocompetitive, atoxigenic strain, but you can read more about it here –

    1. Warren Lewis: It is technically possibly (I found small UV keylights, $750 for 1,000, ), but there are some considerations that would likely increase cost. One UV LED may not be intense enough to adequately fluoresce the toxins, and would defiantly not be visible in bright sunlight. Another problem would be LED light degradation over time. Both of these issues could lead to false negatives, making UV screening for aflatoxins worthless. More high quality LEDs would be required to increase intensity, which also requires more battery power and UV protective goggles. To monitor LED bulb degradation, a UV control strip could be provided with the flashlight to indicate when the LEDs are no longer effective. I roughly estimate this to increase the cost to ~$8-10 per light. Given a few thousand dollars, proper distribution and education, I think an effort of this type could make an impact and save lives.

  2. My concern is the introduction of a toxin to fight a toxin. What will we have in 10 years? Mutation of aflatoxin seems likely over time. Then what?

    I understand that it will be dealt with it then, but is there something chemically that can be introduced into the soil itself,for instance a mineral that the negative cannot flourish on that would feed the cassava?

  3. @Michael – good point. It’ll be a heck of a slippery slope if we keep going up the food chain introducing toxins to kill toxins. And of course you eventually have to deal with resistance – just like we are seeing with MRSA in hospitals.

    @Warren – While a great idea, I don’t expect the lights will be strong enough to help much. We need to give the tech a few more years to mature to give us something that is both strong and cost effective.

  4. @Michael

    “My concern is the introduction of a toxin to fight a toxin.”

    That is an incorrect view of what is being proposed. The article states, correctly, that:

    “Plant pathologists from Africa and the United States are advocating spraying atoxigenic (non-toxin producing) strains of Aspergillus on crops in Kenya to help limit the growth of toxic strains.”

    In other words: a non-toxin producing ‘version’ of the fungus Aspergillus is introduced to the soil in large quantities to out-compete the toxin producing ‘versions’ already in the soil. The point is that Aspergillus flavus itself is not harmful to humans, only the toxin it produces.

  5. Can aflatoxins growth be contained at the storage level of maize, by inhibiting environmental conditions that propagate it growth? Temperatures , humidity and light intensity can be controlled to ensure minimal growth of aflatoxin

  6. What about the impact of using storage insecticides. They will probably reduce insect damage to the grains and help to suppress fungal growth

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