Mycotoxins

A Biological Perspective

What is a Mycotoxin?

• Secondary metabolites (chemicals) of a fungus that produce toxic results in another organism.

• Cytotoxic: disrupt cell structures such as membranes, and processes such as protein, DNA, and RNA synthesis.

• Lack of visible appearance of fungus does not negate presence of mycotoxins. Toxins can remain in the organism after fungus has been removed.

• Less selective in organism selection, can cross plant species barrier.

• Can be heat stable, not destroyed by canning or other
processes.

Information About Fungus

• Range from single cells to fruiting bodies that form molds, mushrooms, smuts, and yeasts.

• Absorb nutrients from living or deceased organisms, contain no chlorophyll.

• If multicellular, they have tubular filaments called hyphae that branch out.

• Reproduce using spores.

Modes of Spore Transmission

• Airborne, wind or indoor ventilation systems.

• Attachment to insects of birds, thus transmitted from plant to plant, or animal to animal, etc.

• Via transportation mechanisms such as trucks, crop machinery, etc.

Fungal Infection

• Can occur at any stage in crop production.

• While in the field.

• During harvesting.

• While in silage and storage.

• Spores can lay dormant for months to years, waiting for positive conditions for germination.

Conditions to Encourage

Fungal Growth

• Relative humidity over 70%.

• Temperatures over 30 degrees Celsius for a period of a few days to a week.

• Stress to the affected plant, such as drought, flood, or insect infestation.

• High moisture content of crop (20% or higher).

• Must occur in conjunction, or fungal growth cycle will cease.

Mycotoxin Chain of Events

Locales of Mycotoxins

• In North America, grain producing areas spread from central Canada to the southern parts of the US.

• These grains are then exported to Asia, the Pacific Islands, South and Central America, Europe, the Middle East, India and Africa.

Brief History of Mycotoxins

• Mycotoxin contamination has affected humans for thousands of years.

• In 7th and 8th century, festival for Roman God Robigus, protector of grain and trees was celebrated to stave off rust and mold.

• Middle Ages had outbreaks of ergotism.

• Only in last 30-40 years have scientists been able to isolate specific toxins from their fungal source.

• Research ideas and methodologies, in this field, change frequently, and data from 20 years ago are considered questionable.

Mycotoxin Statistics

• 300-400 mycotoxins presently identified, with more becoming evident as new isolation techniques are used.

• Most frequent toxins present are aflatoxin, DON, ZEN, fumonisin, and T-2 toxin, to name a few.

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