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