Toxin-producing Aspergillus flavus mold is the greenish powdery growth on this ear of corn damaged by corn rootworms. Image courtesy A. Robertson, Iowa State University.

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Fungus Responsible for Africa's Deadly Maize Identified

By Erin Peabody
April 26, 2007

It's now clear that a poisonous strain of the fungus Aspergillus flavus, known as the "S" strain, is to blame for causing 125 food-related deaths in Kenya in 2004, according to research by an Agricultural Research Service (ARS) plant pathologist and his colleagues.

The fungus, which produces invisible toxins that are known to be carcinogenic, had contaminated portions of the country's maize crop. This is the third time since 1981 that the so-called "Kenyan death fungus" has tainted the African nation's primary food staple with deadly levels of poisons.

Peter Cotty, an ARS scientist based in the Department of Plant Sciences at the University of Arizona in Tucson, and Claudia Probst, of the University of Arizona, worked with Henry Njapau of the Food and Drug Administration in College Park, Md., to investigate which Aspergillus strain was the culprit. Cotty is administratively part of the ARS Southern Regional Research Center in New Orleans, La.

The scientists' findings, reported in the current issue of Applied and Environmental Microbiology, will be critical to researchers who are trying to devise methods for preventing future cases of fungal poisoning, or aflatoxicosis, in African maize.

Aflatoxins are natural poisons produced by certain fungi that belong to the genus Aspergillus. Health consequences related to consuming aflatoxin-contaminated foods include impaired growth, cancer and death.

These toxins can contaminate an array of crops including corn, cottonseed, peanuts and tree nuts. To ensure public safety, many countries, including the United States, have established maximum allowable levels for aflatoxin in farm products. Unfortunately, these standards do little to reduce the ingestion of locally grown, fungus-infested crops in small rural communities in Africa.

Through a special permit, the researchers were able to obtain samples of contaminated maize from affected Kenyan villages. After grinding the corn, they isolated the fungi and grew them in culture. Surprisingly, they found the "S" strain of A. flavus, a potent aflatoxin producer not previously known in Africa, to be the most prevalent source of toxins in the maize.

ARS is the U.S. Department of Agriculture's chief scientific research agency.