Etiology and conditions of toxin accumulation
The main etiological factor in the development of mycotoxicoses is mycotoxins (which include, for example, aflatoxins). These are specific secondary metabolites that are products of the normal vital activity of phytopathogenic and saprophytic soil fungi.
The process of accumulation of these hazardous substances is directly related to the growth of fungal colonies on various food raw materials and agricultural products. Key risk factors contributing to massive contamination and toxin production include errors in the agricultural cycle:
- Gross violations of crop harvesting agrotechniques.
- Improper storage of agricultural crops under unsuitable conditions.
- Errors during the processing and transportation stages of food raw materials.
Epidemiology and transmission routes
Infection of the organism and subsequent development of intoxication can occur via two main routes, making the control of mycotoxin spread an extremely difficult task in preventive medicine and veterinary science.
- Direct route. Occurs through the direct consumption of plant products contaminated with fungi and their metabolites.
- Indirect route. Implemented through livestock products. If farm animals are fed feed contaminated with mycotoxins, the poisons are metabolized and accumulate in their tissues. As a result, humans develop intoxication by consuming meat, milk, or eggs from such animals.
> Important epidemiological rule: The presence of mycotoxins in feed or food products is not necessarily accompanied by visible mold growth. The product may look completely wholesome while containing a lethal dose of fungal secondary metabolites.
Seasonality and resistance of mycotoxins
Mycotoxicoses in animals are characterized by a distinct seasonality, which is important to consider when taking an anamnesis and assessing the epidemiological situation. Mass poisoning cases are most frequently recorded in autumn when animals graze on stubble, or in early spring when grazing on grass that has survived frosts.
Properties of mycotoxins (resistance factors): A distinguishing feature of mycotoxins is their unprecedentedly high resistance to aggressive environmental factors. They demonstrate resistance to:
- Freezing (low temperatures preserve the poison but do not destroy it).
- High temperatures (pronounced thermostability makes classic thermal processing of food ineffective).
- Ultraviolet irradiation.
- Ionizing radiation.
Briefly: answers to topical questions
Which specific genera of microscopic fungi are the main causative agents of human mycotoxicoses?
The main causative agents of human mycotoxicoses are microscopic fungi of the genera Fusarium, Penicillium, Aspergillus, and Claviceps.
- Genus Fusarium — develop on plants, causing fusariotoxicoses.
- Genus Penicillium — develop on vegetative or harvested plants, producing hazardous toxins.
- Genus Aspergillus — parasitize cereal crops and peanuts, producing aflatoxins.
- Genus Claviceps (specifically, Claviceps purpurea) — infects cereals (rye), forms sclerotia, and causes ergotism.
Which classes of mycotoxins, besides aflatoxins, have the greatest medical significance?
In addition to aflatoxins, the sources indicate the following common and toxic mycotoxins:
- Ochratoxins: ochratoxins A, B, C; ochratoxin A is listed among the most common and toxic representatives.
- Ergot alkaloids: ergotoxin, ergotamine, ergometrine; producer is Claviceps purpurea.
- Trichothecenes: the group includes about 100 types of toxins, e.g., deoxynivalenol; produced by Fusarium and other genera.
- Other indicated mycotoxins: zearalenone, patulin, sterigmatocystin, fumonisins, moniliformin, fusarochromanone, aurofusarin.
Which target organs are primarily affected in acute and chronic aflatoxicosis?
In aflatoxin poisoning, the sources indicate the following lesions:
- Liver — aflatoxins exhibit pronounced hepatotropism; consumption of foods containing aflatoxin is described as causing severe poisoning with necrotic liver damage.
- Kidneys — necrotic kidney damage has been described.
- Digestive tract — hemorrhagic inflammation of the digestive tract has been described; aflatoxins also have a carcinogenic effect and cause gastrointestinal tumors.
Which nosological forms belong to classic human mycotoxicoses?
The main nosological forms of classic human mycotoxicoses include:
- Ergotism — occurs in convulsive, gangrenous, or mixed forms.
- Fusariotoxicoses — include alimentary-toxic aleukia (septic angina), sporotrichiellotoxicosis, fusarium graminearum toxicosis, and fusarium nivalenol toxicosis.
- "Drunk bread" poisoning — occurs upon consumption of grain infested with Aspergillus flavus or Fusarium sporotrichiella.
- Aflatoxicoses — severe food poisonings caused by Aspergillus toxins.
What laboratory diagnostic methods are used to detect and quantify mycotoxins in food products?
To detect and identify mycotoxins in food products, the following methods are used:
- Physicochemical methods — chromatography and spectrophotometry.
- Immunological methods — enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay (RIA).
- Biological methods (bioassays) — using chicken embryos, cell cultures, laboratory animals (rats, mice, guinea pigs), birds (ducklings, pigeons), and sensitive microorganisms.
The investigation is preceded by the extraction of the mycotoxin from the sample using an organic solvent.
To memorize the factors to which mycotoxins are resistant, use the acronym I-FRU: Ionizing radiation, Freezing, Ultraviolet light, Thermostability.
Class and exam questions
Can mycotoxins be eliminated by thoroughly boiling the product?
No. Mycotoxins are highly thermostable and retain their toxic properties even after prolonged exposure to high temperatures.
If animal feed shows no visible mold, does it mean it is safe?
Absolutely not. A crucial feature of mycotoxicoses is that toxins can be present in raw materials and feed even without visible, naked-eye growth of fungal mycelium.
How can a human become infected indirectly?
Humans become infected by consuming meat, milk, or eggs obtained from animals whose diet included feed contaminated with mycotoxins.
What else to study on this topic
- Mechanisms of secondary metabolite synthesis by saprophytic and phytopathogenic fungi
- Specific effects of aflatoxins on the human and animal organism
- Veterinary and sanitary inspection of meat and milk for mycotoxins
- Impact of agricultural violations on the epidemiology of food intoxications
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