Chapter 14 Flashcards
What are mycotoxins?
- secondary metabolites produced by filamentous fungi
Mycotoxins are most common in:
- cereal grains
- corn
- peanut and tree nuts
Common characteristics of mycotoxins
- can be very toxic to humans and animals at low concentrations
- lack of visible appearance of fungus, does not negate presence of mycotoxins
- toxins can remain in the organism after the fungus has been removed
- can be heat stable, not destroyed by canning or other processes
Where are mycotoxins found?
- in food and feed
What kind of affect do mycotoxins have on animal health?
- detrimental effect on animal health and performance
- the impact on animal health and productivity depends on the interactions between the toxin, the animal and environmental factors
What are mycotoxins important?
- because they can be costly when they effect
- the food and agriculture organization of the United nations (FAO) states the cost of mycotoxins in canada and US is approximately 5 billion dollars a year
1. animal productivity
2. human health
3. international trade
Human symptoms from mycotoxins
- immunosuppression
- irritation of the mucus membrane and the CNS
- symptoms related are varied, but may include headaches, respiratory stress, dizziness, nausea, fatigue and diarrhea
- carcinogenic
Symptoms in animals from mycotoxins
- economic loss due to impaired health of stock animals
- feed refusal
- impaired animal health resulting in reduced production of eggs, milk, weight gain, etc
- metabolites are passed through the milk in cheese, dry milk and yogurt
- disease
- death
Mycotoxin Health hazards
- generally lower risk in well developed countries due to improved standards of living
- high intake of affected product, usually in conjunction with limited amounts of other food sources
- greatest threat comes from long term exposure due to eating contaminated food or meat from animals fed contaminated feed
Why mycotoxins in the past?
- food eaten right away, or dried and stored in short term
Why mycotoxins in the present?
- large amounts of food produced at once
- large amounts stored (silo, warehouse, stores)
- shipped great distances, over a long time
- cultural differences
- fermented flavors
- animals will eat it
- may be contaminated even if you do not see mold
Brief history of mycotoxins
- mycotoxin contamination has affected humans for thousands of years
- festival for roman god Robigus, protector of grain and trees was celebrated to stave off rust and mold
- middle ages had outbreaks of erogtism
- only in the last 30-40 years have scientists been able to isolate specific toxins from their fungal sources
Turkey X disease
- formal study of mycotoxins began with the investigation of the deaths of more than 100,000 turkeys in England
- linked to aflatoxins in the grains they were being fed
Aflatoxins
- linked to Turkey X disease
- in England thousands of turkeys sickened rapidly, hemorrhaged subcutaneously and died
- were found in Brazilian peanut mill in feed
- potent carcinogen
Major groups of mycotoxins
- Alfatoxins
- Ochratoxin A
- T-2 Toxin
Alfatoxins are produced by what species?
- produced by Aspergillus flavus, A parasiticus
where are alfatoxins found?
- wheat, corn, peanuts, tree nuts, cottonseed, spices
- in milk, eggs, cheese, meat because of the animal consumption of contaminated feed
What do alfatoxins affect?
- immunosuppressive, mutagenic, and carcinogenic
- main target is the liver
What food is the greatest concern with alfatoxins?
- corn because it is grown in climates that are likely to have perennial contamination with alfatoxins
- corn is the staple food in many countries
- procedures used in the processing of corn help to reduce contamination
In what type of climate do alfatoxins thrive?
- in warm climates
- on substrates with low water contents
- storage mold and advantageous pathogens
What are major determining factors in mold infestation and toxin production?
- water stress
- high temp stress
- insect damage of the host plant
Ochratoxin A is produced by what species?
- produced by species of only two genera of fungi: Penicillium and Aspergillus
What does Ochratoxin A contaminate?
- cereals, fresh grapes, dried vine fruit, wine, beer, coffee and cocoa
What is the affect of Ochratoxin A
- damaging to kidneys and liver
- suspected carcinogen
- evidence that it impairs the immune system
Which mycotoxin is one of the most potent naturally occurring carcinogens known to man?
- Alfatoxins
- most have been classified by type 1 carcinogens
T-2 Toxins (trichothecene) produced by what species?
- Stachybotrys and Fusarium
What is the affect of T-2 Toxins?
- damage is often permanent
- can severely damage the entire digestive tract and cause rapid death due to internal hemorrhage
- studied extensively due to toxic and immunosuppressive effects and its potential as a biological weapon
Fusarium
- a T-2 Toxin producer
- most are plant pathogens and can be found in the soil
What plants are affected by Fusarium?
- corn, wheat, barley, beans
- lesser contamination in rye, triticale, millet and oats
What do Trichothecene toxins target?
- circulatory, alimentary, skin and nervous systems
What percentage of the worlds food crops are significantly contaminated by mycotoxins?
- according to the Food and Agricultural Organization 25% of the worlds food crops
- significant economic losses are associated with their impact on human health, animal productivity and both domestic and international trade
How does food staple contamination and consumption affect populations?
- result of morbidity and premature death
What factors influence mycotoxin occurrence in the food chain
- biological factors
- environmental factors
- harvesting
- storage
- distribution processes (animals-> animal products->humans)
How to minimize mycotoxin contamination
- preharvest
2. post harvest
How to minimize mycotoxin contamination in pre-harvest?
- genetically enhance resistance via transgenic and conventional methods
- good agronomic practices
- biocontrol methods
- chemical methods via fungicides and antioxidants
How to minimize mycotoxin contamination in post-harvest?
- physical methods such as sorting and improved storage and transportation conditions
- chemical methods such as ammoniation
Fight against mycotoxins
- regulatory control, considered unavoidable so monitor levels 10-20 ppb
- detoxification strategies
- have farmers select strains resistant to contamination
- genetically engineer plants resistant to fungal infection
- use feed additives that sequester the toxins and prevent absorption from the gastrointestinal tracts
Maize Quality Improvement Project
- launched in north ghana to make farmers, traders and government officials aware of the health risks of mycotoxins
- involves the whole upstream supply chain
- planting, drying, harvesting, storage and milling
Ergotism
- poisoning produced by eating food affected by ergot (rye)
- results in headache, vomiting, diarrhea, and gangrene of fingers and toes
Ergot (sclerotium)
- probably attributed to salem witch trials because ergot contains alkaloids which led to people behaving oddly
- alkaloids produced by Claviceps purpurea that infects rye and other cereals
Symptoms of convulsive ergotism
- nervous system dysfunction
- painful seizures and spasms
- mental effects
- gastrointestinal effects (diarrhea)
Gangrenous ergotism symptoms
- lose parts of extremities such as toes, fingers, ear lobes
- in more serious cases arms and legs
