What are mycotoxins and why should we care?
With corn and soybean harvest approaching, it is time for a reminder of factors that can affect grain quality, and today’s column will be dedicated to mycotoxins.
Mycotoxins are toxic substances produced by certain molds (fungi) on the different substrates where they grow.
What kind of substrates
are we talking about?
The fungi that produce mycotoxins affect a wide range of plants and plant products; however, they are most commonly found in corn, peanut, wheat, barley, rye, oats, and rice, and they can also be present in spices, dried fruit and edible seeds.
Mycotoxins can be very toxic when inhaled, absorbed through the skin, or consumed at very low concentration levels, which means that even a few milligrams or even micrograms in food or feed may pose a risk for human and animal health.
Are mycotoxins just
an issue in raw grain?
Given that mycotoxins are heat-tolerant, they will not be affected by most food and feed processing operations.
What are the effects of
mycotoxins on human
and animal health?
Diseases caused by mycotoxins are called mycotoxicosis. The effects of mycotoxicosis can either be acute, leading to severe symptom development after a short exposure to high doses, or chronic, which is the result of long-term exposure to small quantities of the toxins.
Chronic exposure may lead to immunosuppression and cancer development. However, the degree of susceptibility to mycotoxins in humans and animals is complex and impacted by many factors including the toxicity of the mycotoxin, age, nutrition, and interactions with certain diseases, other mycotoxins, and/or substances.
When do mycotoxin
Typically, outbreaks are seasonal, and will occur under favorable weather conditions for disease development, the presence of a host crop at a stage that is susceptible, and the presence of the mycotoxin-producing fungus.
One of the first cases of widespread human mycotoxicosis occurred in Europe during the Middle Ages when an epidemic of a disease called Saint Anthony’s Fire occurred, leading to the death of thousands of people in France alone.
The symptoms of Saint Anthony’s Fire included convulsions, spasms, a burning sensation in the extremities and in some cases, gangrene and the loss of body parts.
Many years later, it was discovered that the disease was caused by the consumption of ergot, small rock-like structures found in the spikelets of rye plants, produced by the fungus, Claviceps purpurea. The disease was later called ergotism, and the toxic substances associated with it were identified as ergoline alkaloids.
What has been the more
recent history of mycotoxins?
Interestingly, mycotoxins did not take center stage as a human and animal health threat until the 1960s, when 100,000 turkeys died of a mysterious disease in England called the “Turkey x disease” (sidenote, have you noticed that scientists have never been creative at naming diseases?).
Anyways, researchers discovered that the disease was linked to the consumption of groundnut meal that had been affected by a fungus called Aspergillus flavus. Later research showed that this fungus produces a potent mycotoxin that was named Aflatoxin, where the “A” comes from Aspergillus, and the “fla” from flavus.
Aflatoxins are considered the most potent naturally- occurring carcinogen known to humans. Fortunately, public health agencies have published guidelines on maximum permitted levels of these toxins in food and feed.
How many mycotoxins
After aflatoxins were discovered, more than 400 mycotoxins have been described. However, most research and regulations around the world have focused on the group of the most toxic and prevalent mycotoxins, including, ochratoxin A, fumonisins, vomitoxin and its derivatives, zearalenone, patulin, T-2, and HT-2, along with aflatoxins.
The fungal organisms that produce these mycotoxins come from the following genera: Aspergillus, Fusarium, and Penicillium.
In the past, it was believed that mycotoxigenic fungi affected grain only during the postharvest stage, particularly when stored under suboptimal conditions like hot and humid weather, and high grain moisture content.
Currently, it is well known that some of the mycotoxigenic fungi infect corn ears and small-grain-spikes during the growing season, and grain sorting and drying become key operations to limit further fungal growth and mycotoxin contamination during storage.
We are frequently asked if grain drying gets rid of mycotoxins, and the answer is no. Grain drying to optimal moisture contents will limit deterioration and fungal growth, however, if the grain has already been contaminated with mycotoxins, drying will not reduce their levels.
In upcoming articles, we will address the effects of specific toxins on animal and human.
If you have questions or concerns about this topic, please contact us: Adriana Murillo-Williams can be reached at email@example.com, 814-355-4897 (phone), or 814-360-5517 (text messages). Paul Esker can be reached at firstname.lastname@example.org.
Adriana Murillo-Williams is an Agronomy Educator with Penn State Extension. Paul Esker, Ph.D, is an assistant professor of Epidemiology and Field Crop Pathology at Penn State University.