Mycotoxins and mycotoxicoses and its types.

1. MYCOTOXINS AND MYCOTOXICOSES:
One of the more important effects of postharvest decays of fruits and vegetables,
especially of seeds (Fig. 11- 112), is the induction of diseases in animals and humans
caused by the consumption of feeds and foods invaded by certain common fungi.
These fungi produce toxic substances called mycotoxins. The diseases they cause
are called mycotoxicoses. Ergotism (St. Anthony’s fire) of humans and animals,
caused by eating ergot containing wheat and rye bread and feeds, and poisoning of
humans from eating poisonous mushrooms, are classic examples of mycotoxicoses
and have been known for a long time. The magnitude of the mycotoxin problem
began to be appreciated during World War II when it was noted that the
consumption of moldy grain led to necroses of the skin, hemorrhage, liver and
kidney failure, and death in numerous humans and animals. Similar symptoms also
appeared in horses fed moldy hay. In 1960, a large number of young turkeys died
in England after they were fed contaminated peanut feed. That led to intensive
research on mycotoxins, which established that they are a global problem.
Mycotoxins pose an ever-present threat to the health of humans and animals. When
they are present in relatively high concentrations they cause acute disease symptoms.
Perhaps even more serious are the chronic effects on health and productivity caused
by the constant presence of subacute dosages of mycotoxins in the food and feed
consumed throughout the world, particularly in developing countries.
Most mycotoxicoses are caused by the widespread fungi Aspergillus, Penicillium,
and Fusarium. Some may result in severe illness and death. Aspergillus and
Penicillium produce their toxins mostly in stored seeds and hay, but also in
commercially processed foods and feeds, including meats, cheeses, and spices.
Infection of seeds usually takes place in the field. Fusarium produces its toxins
primarily on corn and other grains infected in the field or after they are stored. Many
other common fungi that infect agricultural commodities or contaminate food
produce several mycotoxins.
Mycotoxins differ in their chemical formula, the products in, and conditions under
which they are produced, their effects on various animals and humans, and their
degree of toxicity. Several different fungi, however, produce some of the same or
closely related toxins. The main, but not all, mycotoxins and some of their properties
are listed here.

2. ASPERGILLUS TOXINS — AFLATOXINS:
Aflatoxins are produced by Aspergillus flavus and several other species of
Aspergillus. Aflatoxins are produced in infected cereal seeds and most legumes, but
they often reach a rather low and probably nontoxic concentration (about 50 ppb).
During some years, a rather high percentage (30% or more) of the corn harvest over
large areas contains more than 100 ppb aflatoxin, which is five times that allowed in
food for humans and feed for sensitive animals such as chickens. However, in
peanuts, cottonseed, fishmeal, Brazil nuts, and probably other seeds or nuts grown
in warm and humid regions, aflatoxin is produced at high concentrations (up to 1000
ppb or more) and causes mostly chronic or occasionally acute mycotoxicoses in
humans and domestic animals. Aflatoxins exist in a variety of derivatives with
varying effects. When ingested with the feed by dairy cattle, some toxins are
excreted in the milk in still toxic form.
The symptoms of mycotoxicoses caused by aflatoxin in animals, and presumably
humans, vary widely with the particular toxin and animal species, dosage, age of the
animal, and so on. Young ducklings and turkeys fed high dosages of aflatoxin
become severely ill and die. Pregnant cows, calves, fattening pigs, mature cattle, and
sheep fed low dosages of aflatoxin over long periods develop weakening, intestinal
bleeding, debilitation, reduced growth, nausea, refusal of feed, predisposition to
other infectious diseases, and may abort. Moreover, most of the ingested aflatoxin is
taken up by the liver, and, in some experiments, animals given feed containing even
less than the permissible amount of aflatoxin (20 ppb) almost invariably developed
liver cancer.
FUSARIUM TOXINS:
Three groups of toxins, zearalenone, trichothecenes, and fumonisins, are
produced by several species of Fusarium, primarily in moldy corn.
Deoxynivalenol, also known as vomitoxin or DON is produced by the fungus
Gibberella zeae (anamorph Fusarium graminearum), the cause of Gibberella ear rot
of corn and head blight (scab) of wheat. The mycotoxin at first causes reduced
feeding by the animals and, thereby, slower gain or loss of weight. At higher
concentrations of mycotoxin, the animals are induced to vomit and refuse to eat.

3. Zearalenone seems to be most toxic to swine, which causes abnormalities and
degeneration of the reproductive system, the so-called estrogenic syndrome. Female
swine-fed zearalenone-containing feed develops swollen vulvas bearing bleeding
lesions and atrophying nonfunctioning ovaries. They are susceptible to abortion, and
the piglets that are born are small and weak. Male swine show signs of feminization,
namely atrophy of the testes and enlargement of the mammary glands.
Fumonisins are produced by Fusarium moniliforme, which causes Fusarium ear
rot of corn that affects as much as 90% of the corn fields. Fumonisins are the cause
of blind staggers (equine leukoencephalomalacia) in horses, donkeys, and mules,
pulmonary edema in swine, and, possibly, cancer in humans.
Trichothecenes (or trichothecenes), of which there are more than 100, are
produced by species of Fusarium and by several other fungi. They are most toxic
when fed to swine, in which they cause, among other symptoms, listlessness or
inactivity, degeneration of the cells of the bone marrow, lymph nodes, and intestines,
diarrhea, bleeding, and death. Other animals, however, such as cows, chicks, and
lambs, are also affected.
Other Aspergillus Toxins and Penicillium Toxins:
In addition to aflatoxins, species of Aspergillus also produce other toxins in infected
grains. The same or similar toxins are also produced in grains infected by species of
Penicillium. The most important such toxins are ochratoxins, which cause
degeneration and necrosis of the liver and kidney, along with several other
symptoms, in domestic animals. Some ochratoxins can persist in the meat of animals
fed contaminated feed and can be transmitted to humans through the food chain.
Yellowed-rice toxins, primarily citreoviridin, citrinin, and luteoskyrin are all
produced by species of Penicillium growing in stored rice, barley, corn, and dried
fish. They cause toxicoses associated with various diseases, nervous and circulatory
disorders, and degeneration of the kidneys and liver.
Tremorgenic toxins cause marked body tremors and excessive discharge of
urine, followed by convulsive seizures that often end in death. They are produced by
species of both Aspergillus and Penicillium infecting foodstuffs in storage and also
in refrigerated foods, grains, and cereal products. Patulin is produced by Penicillium
and Aspergillus. It causes edema and bleeding in the lungs and brain, damage to

4. kidneys, and paralysis of motor nerves and it also induces cancer in higher
organisms. It is commonly found to occur naturally in foodstuffs such as fruit or
juices made with fruit partly infected with Penicillium, in naturally molded bread
and bakery products, and most commercial apple products. Thus, patulin may
constitute a serious health hazard for humans as well as for animals.
Ergotism is the oldest known mycotoxicosis. It is caused by several toxic
substances in the ergot fungus's sclerotia (ergots) (Claviceps) when they
contaminate grain crops, such as rye, barley, sorghum, millet, wheat, and wild
grasses, and are ingested by humans and animals. Ergotism is expressed as
convulsions and limb swellings, followed by gangrene of body extremities and
burning sensations (St. Anthony’s fire). Ground-up ergots have been used in the
past to stop heavy bleeding, as happens, e.g., during labor or accidents.
Fescue toxicosis affects cattle and horses feeding on plants of the perennial grass
tall fescue infected systemically with the fungus Acremonium. The fungus is an
endophyte growing internally through the plant without invading its cells. The
fungus seems to make the infected plants more resistant to stress, particularly
drought. Horses eating tall fescue plants infected with the fungus show only
reproductive disorders. Cattle feeding on such plants, in addition to reduced calving
and lower milk production, show reduced weight gains, elevated body temperature,
and rough hair coat; moreover, as in ergotism, feet or other body extremities may
develop gangrene and drop off (“fescue foot”).