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Deadly Molds Toxin : Trichothecene

Trichothecenes are a large family of chemically related mycotoxins produced by various species of fungi living in diverse habitats throughout the world. Important fungi associated with the production of these toxins are Fusarium, Myrothecium, Trichoderma, Acremonium, Cylindrocarpon, Statchybotrys and Verticimonosporium. They include both saprophytic and plant parasitic species of fungi. Like other mycotoxins, trichothecenes are also produced without obvious benefit to the organism. The toxins are produced by these organisms mainly in response to environmental stresses.

They are highly toxic at the sub cellular, cellular as well as organic system levels. Trichothecenes are powerful inhibitors of protein synthesis by affecting polyribosomes. They easily penetrate cell lipid layers and attacks cellular organelles and nucleic acids. In sub lethal toxic doses they are immune suppressive and affects the function of T-cells, B-cells and Macrophages. This results in secondary infection by other organisms including bacteria and virus. Irritation of the skin and gastroenteritis are another symptom of trichothecene toxicosis. High concentration of trichothecenes often lead to feed refusal by farm animals resulting in reducing weight gain. Excessive salivation and vomiting may occur in extreme cases. The name Vomitoxin was given to DON due to this vomiting symptom. But now it is an established fact that other Trichothecenes can also induce vomiting in farm animals.

Occurrence and Outbreak
Earlier record of the incidence of Trichothecenes poisoning is around 1900 when thousands of people died in erstwhile USSR due to the consumption of mould infected grains. A trichothecene producing fungus (T-2 toxin) Fusarium graminiarum (Gibberella zeae) was later identified as the cause of this infection. Later similar poisonings were also reported from Japan, China and other Eastern Countries due to the consumption of mouldy grains especially wheat and barley. Now this toxin is known from other parts of the world including U.S.A, Canada, South America and Europe.Today there are about 150 derivatives of trichothecenes known. They belong to a family of closely related chemical compounds called Sesquiterpenoids. They are classified as Group A and Group B compounds depending on their chemical structure.
 
Group A Trichothecenes are the most commonly reported ones and they include T-2toxin, HT-2toxin, neosolaniol, monoacetoxyscirpenol (MAS) and Diacetoxyscirpenol (DAS).Group B trichothecenes are Deoxynivalenol (DON – Also called Vomitoxin), Nivalenol, 3-15 acetoxynivalenol, fusarenon X, etc.
In addition another group of trichothecenes are also known as Macrocyclic ones, produced by Stachybotrys atra, a saprophytic fungus associated with damp surroundings especially on wooden walls, pillars, mats, etc. These toxins are also referred as Satratoxins. Airborne spores of this fungi thus contribute to the health problems among building occupants where this saprophytic fungi are grown. Stachybotryotoxicoses has also been reported from farm workers in Russia and neighbouring countries. They got infection due to their association with hay- fed dosmestic animals. A macro cyclic Trichothecenes was later identified from Stachybotrys atra infected hay samples.

Unlike the much known Aflotoxins, trichothecenes does not require metabolic activation and hence has strong impact on the health of man and animals. These lipophilic mycotoxins are easily absorbed through skin, gut and pulmonary mucosa. They enter the body by dermal application as well as by oral ingestion.They are highly toxic at the sub cellular, cellular as well as organic system levels. Trichothecenes are powerful inhibitors of protein synthesis by affecting polyribosomes. They easily penetrate cell lipid layers and attacks cellular organelles and nucleic acids. In sub lethal toxic doses they are immune suppressive and affects the function of T-cells, B-cells and Macrophages.

This results in secondary infection by other organisms including bacteria and virus. Irritation of the skin and gastroenteritis are another symptom of trichothecene toxicosis.High concentration of trichothecenes often lead to feed refusal by farm animals resulting in reducing weight gain. Excessive salivation and vomiting may occur in extreme cases. The name Vomitoxin was given to DON due to this vomiting symptom. But now it is an established fact that other Trichothecenes can also induce vomiting in farm animals.

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