VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

GENERAL FEATURES OF MYCOTOXIN FORMATION

• Many of the toxigenic fungi, over 100 known species, are capable of elaborating mycotoxins.
• The same mycotoxin can be produced by different fungi and the same fungus can produce different mycotoxins.
• Toxin production occurs only under specific conditions of moisture, temperature, suitability of substrate and appropriate oxygen tension.
• The optimum conditions for toxin production are relatively specific for each fungus.
• For e.g. Fusarium elaborates its toxin at freezing temperature, while A. flavus requires a temperture of 25⁰C.
• The susceptibility of different crops to mould infection is goverened by the presence of suitable substrates.
• Damage to the seed coat by insects, mechanical harvesting, severe frost or other factors may predispose crops to fungal attack.
• Insects may also serve as carriers of fungal spores.
• The fungi associated with cereal grains have been divided mainly into two types.
  • Field fungi which invade the grains before harvest and required greater water activity for growth
    • e.g. Fusarium, Helminthosporium and Cladosporium
  • Storage fungi which invade the grains after harvest during drying and in storage
    • e.g. Aspergillus, Penicillium
• The main types of toxigenic fungi, which produce mycotoxins of animal/ poultry importance, are

Species	Toxins
A.flavus and A.parasiticus	Aflatoxins
A. ocheraceus	Ochratoxin
Fusraium roseum	Trichothecane (t-2) toxin
Penicillium citrinum	Citrinin
A.nidulans and A.versicolor	Sterigmatocyosin