By Tristan Wang, ’16
During the 1930’s, horses in Ukraine began to suffer odd and mysterious symptoms. Peculiarities began with cracking skin at the corners of the mouth and the swelling lips to produce a comical yet unfortunate appearance of a hippopotamus. Inflammation of the eyes and nose would occur followed by fever, vascular defections, and death in many cases (Money 2004). Today, we know this as stachybotryotoxicosis, one of the the first well-documented case of veterinary mycotoxicosis (diseases caused by mycotoxins) but the mysterious disease struck fear for many Soviet officials. Initially called neizvestnoe zabolevanie “illness of unknown cause,” the economic impact quickly resulted in a name-change to massovie zabolivanie “mass illness” to reflect the gravity of horse loss in transportation and agriculture (Money 2004). Nikita Khrushchev even wrote in his memoirs about his concerns of the extensive losses of horses (Ciegler and Bennett, 1980).
From infected rye that caused St. Anthony’s Fire to Turkey X disease from contaminated peanut meal to alleged uses of biological warfare with Yellow Rain, the real threat of mycotoxins belie the seemingly innocuous appearance of molds. Tendrils of fungal hyphae reach even indoor environments and have prompted creative solutions including fungistats and special diets to counter the effects of these toxins. Mycotoxins may be one of the overlooked threats people face on a daily basis.
What are Mycotoxins?
Mycotoxins are toxic secondary metabolites produced by molds that are deleterious upon ingestion, inhalation, or direct contact (Ciegler and Bennett 1980, Ginemo and Martins 2006). Specifically, mycotoxins are polyketones and are chemicals that are produced during condensation reactions when specific biotic and abiotic conditions are met (Ginemo and Martins 2006). Mycotoxins are usually formed during the start of the stationary phase of the mold’s growth after the mold’s exponential phase of growth (Gimeno and Martins 2006).
Scientists have detected more than 250 mycotoxins but they do not know how many are in existence (Carlson and Ensley 2003). For the purpose of improving human lives and economy, scientists have predominantly studied mycotoxins dealing with severe mycotoxicosis (diseases caused by mycotoxins) originating from food. The most common contaminants to human and animal foods include aflatoxins, ochratoxins, zearalenone, fumonisins, and trichothecenes toxins (Gimeno and Martins 2006).
Likely the most well-known mycotoxin, aflatoxins are secondary metabolites created by particular strains of the genus Aspergillus, particularly Aspergillus flavus and Aspergillus parasiticus (Ciegler and Bennett 1980). These highly oxygenated and heterocyclic compounds first caught the attention of scientists in the early 1960’s during an epidemic of the Turkey X disease in South Eastern England (Ciegler and Bennett 1980). Just in the spring of 1960, more than 500 outbreaks affecting thousands of turkeys occurred (Wannop 1961). Nervous symptoms, comas, and high mortalities (sometimes 100%) in turkeys ultimately galvanized veterinary research workers to meet in August that same year (Wannop 1961). Possible pathogens were observed as likely culprits until scientists ultimately agreed on contaminated peanut meal by Aspergillus flavus as the culprit (Wannop 1961).
One aflatoxin, aflatoxin B1, may even cause cellular transformation as the mycotoxin may cause point mutations with DNA. The movement of DNA, GC to TA transversions if the DNA remains unrepaired, may cause swaps between purine and pyrimidine nucleic acids (Muro-Cach et al. 2004) Not surprisingly, DNA-changing mycotoxins became the talk of popular culture. One breaking headline even claimed “Moldy Peanut Poison Breaks Chromosomes” (School Science and Mathematics 1965).
Unlike many of the other mycotoxins, fumonisins are water-soluble and at least in animal testing, are not absorbed well and quickly eliminated in animal subjects (Muro-Cach et al. 2004) This lesser-severity may explain why the mycotoxin was one of the later chemicals studied (Muro-Cach et al. 2004) However, mycotoxicosis due to fumonisin exist in the forms of lesions, depression, and anorexia in swine, horses, and other ruminants (Carlson 2003). Mycotoxins of the fumonisin variety are typically created by Fusarium moniliforme and Fusarium proliferatum contamination of yellow and white corn (Carlson 2003).
Discovered in 1965 and obtained from corn stuffs in the US, ochratoxins are well known to cause acute tubular necrosis (ATN), a condition stemming from the death of tubular epithelial cells of the kidney, in all animals so far studied (Muro-Cach et al. 2004). Ochratoxins are produced from Aspergillus and Penicillium species and can be found on cereals, bread, and coffee (Peraica et al.) Ochratoxin A in particular has carcinogenic, immunosuppressive, and teratogenic properties (Peraica et al. 1999)
Consisting of at least 148 compounds, trichothecenes are typically produced by species of Fusarium, Trichoderma, Trichothecium, Myrothecium, and more infamously by Stachybotrys, a genus known as “black mold” (Peraica et al. 1999). Mycotoxicosis stemming from trichothecenes was initially observed in 1932 in the USSR due to cases of alimentary toxic aleukia but the toxin was brought into the limelight during the “Yellow Rain” incident (Peraica et al. 1999). Yellow rain refers to reports by South East Asian refugees claiming that aircraft carrying toxic chemicals (likely T-2 trichothecene toxins) poisoned people below (Garmon 1981). Mycotoxins used by counterinsurgency warfare supplied by the Soviet Union at that time would have violated the 1972 Biological Weapons Convention. However, reports from several studies have shown that yellow rain actually consisted of large quantities of pollen likely dropped from wild honeybees (Garmon 1981).
Zearalenone toxins are less toxic than its counterparts and can be more accurately described as a nonsteroidal estrogen due to its estrogenic-like properties (Muro-Cach et al. 2004) Estimates have suggested that people living in the US consume about 80 ng/kg/day (Muro-Cach et al. 2004)
Given the ubiquity of molds and mycotoxins, researchers and industrial hygienists have observed the possibility of mycotoxins entering our daily lives. One possible area of research is the effects of molds in indoor and outdoor air. Most outdoor fungal substances originate from the genus Cladosporium in addition to other mushroom species, Aspergillus, and Penicillium. Indoor building molds depend on the nutrients and water availability but species from Stachybotrys and Aspergillus can be commonly found (Jarvis and Miller 2005). Although molds are present in most environments, molds pose their greatest threat not particularly through mycotoxins but through allergic reactions like asthma and hypersensitivity pneumonitis (Jarvis and Miller 2005).
To help control mycotoxins, at least in foods, researchers have been looking into possible chemicals to use. Fungistats for example are chemicals that act as inhibitors to the growth and production of various enzymes in molds—sorbic acid, sodium salts, and formic acid to name a few (Gimeno and Martins 2006). These chemicals are often used instead of fungicides, chemicals that kill fungi by destroying their cellular membrane, due to the fungicides toxic nature to people (Gimeno and Martins 2006). In addition, some research has looked into absorbing additives like hydrated sodium and calcium aluminosilicates to help absorb mycotoxins when eaten although more research needs to be done to increase the effectiveness and prevent absorption of other nutrients (Gimeno and Martins 2006).
Something as common as mold can pose a serious threat to humans and animals given constant exposure. While deaths from mycotoxins are not as flashy as deaths from deathcap mushrooms or large carnivorous animals, studies into the field may yield applicable and relevant information to the daily lives of people.
Author Unknown. “Moldy Peanut Poison Breaks Chromosomes.” School Science and Mathematics 65.9 (1965): 761-845.
Carlson, Michael P., and Steven Michael Ensley. Understanding fungal (mold) toxins (mycotoxins). Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, 2003.
Ciegler, Alex, and J. W. Bennett. “Mycotoxins and mycotoxicoses.” Bioscience 30.8 (1980): 512-515.
Garmon, Linda. “Yellow Rain Riddle.” Science News 120.16 (1981): 250-251.
Gimeno, Andres, and Maria Ligia Martins. “Mycotoxins and mycotoxicosis in animals and humans.” Special Nutrients, Inc. USA (Ed.). Victor Mireles Communications, Mexico City (Mexico) (2006): 1-127.
Jarvis, Bruce B., and J. David Miller. “Mycotoxins as harmful indoor air contaminants.” Applied microbiology and biotechnology 66.4 (2005): 367-372.
Money, Nicholas P. Carpet monsters and killer Spores: A Natural History of Toxic mold. Oxford University Press, 2004.
Muro-Cach, Carlos A., et al. “Mycotoxins: Mechanisms of toxicity and methods of detection for identifying exposed individuals.” Journal of Land Use & Environmental Law 19.2 (2004): 537-556.
Peraica, M., et al. “Diseases caused by molds in humans.” Bulletin of the World Health Organization 77.9 (1999): 754-766.
Wannop, C. C. “The histopathology of turkey” X” disease in Great Britain.” Avian Diseases 5.4 (1961): 371-381.