Mycotoxins are small compounds found contaminating several plant products.  They are toxic to animals and humans in small doses and poisonings are often difficult to diagnose.  Symptoms of many mycotoxicoses are similar to each other and to those of other food poisonings and viral or bacterial diseases.

The story of aflatoxin, the first described mycotoxin, begins around 1960 in the United Kingdom.  A mysterious disease was running rampant through poultry farms, leaving upwards of 100,000 turkeys dead.  Veterinarians could not easily diagnose this new affliction labeled “Turkey X Disease”.  After ruling out known parasites, focus shifted to a common food source – a Brazilian peanut meal. The peanuts were found to be contaminated with a toxin they dubbed aflatoxin after the fungus found to produce it, Aspergillus flavus.

Aspergillus flavus fungus colonizing field corn (image: Maize Breeding Program at TAMU)

Aspergillus flavus fungus colonizing field corn (image: Maize Breeding Program at TAMU)

A. flavus colonizes oil-rich seeds, such as peanuts, maize (corn), cotton, ground nuts and pistachios.  Unlike many fungi, A. flavus and aflatoxin production are favored by hot and dry conditions.  In the United States, aflatoxin is a sporadic concern primarily for pets and livestock who consume corn and cottonseed products (See: 2006 and 2010 outbreaks in dry pet food).  However, it is a serious concern for human health in other parts of the world, most notably Kenya.  Highly toxigenic (produce high levels of aflatoxin) strains of A. flavus are native to regions in Kenya.  This combined with a maize-based diet and poor storage facilities (A. flavus can continue to grow and produce more aflatoxin after harvest if the grain is not kept dry) leads to aflatoxin poisonings every year in Kenya (even if they aren’t reported).  Aside from acute poisonings (involving liver failure and death), chronic exposure to aflatoxin can lead to liver cancer, jaundice, weight loss and immune system problems.  Aflatoxin can also pass from mother to baby through breast milk.  2004 marked the worst reported aflatoxicosis outbreak in Kenya and the world with 125 documented deaths.

A maize flour mill in Kenya (image: CDC).

A maize flour mill in Kenya (image: CDC).

What can be done?  Researchers have been focusing on understanding the populations of A. flavus in Kenya.  Atoxigenic (naturally produces no aflatoxin) strains of A. flavus have been identified and are being used as a biological control (A product called “aflasafe”) against more toxin strains.  The goal is for the toxin-free strains to outcompete the poison-producing ones in the maize fields, resulting in a less contaminated crop.  Extension and outreach programs have emphasized aflatoxin awareness for those who grow (management strategies, including the new bio control), store (keep it dry, inspect the grain) and sell maize (inspect before sale and production).

Please take a look at this slide show on aflatoxin management in Kenya.

Up next in this series, I’d like to discuss quantitative and qualitative testing methods for mycotoxins.  Testing is easier said than done (accurately), especially in a field setting.

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