Mycotoxins and their importance for public health Essay

Mycotoxins and their importance for public health

Mycotoxins and their importance for public health

Ahmed Ali - 20178050

Mycotoxins (Myco = of fungal origin)

· toxic substances produced by fungi (molds) growing on crops/grains in the field or in storage.

· Secondary metabolites (chemicals) of a fungus that produce toxic results in another organism.

· Unlike bacterial toxins, fungal toxins (mycoatoxins) are not proteins and therefore are not usually detectable by the immune systems of humans and animals

· Lack of visible appearance of fungus does not negate presence of mycotoxins. Toxins can remain in the organism after fungus has been removed.

· Cytotoxic: disrupt cell structures such as membranes, and processes such as protein, DNA, and RNA synthesis.

· Can be heat stable, not destroyed by canning or other processes.

Most fungi do not produce Mycotoxins

· Many fungi are edible

· Mushrooms are fungi

· Moldy feeds may be degraded without presence of mycotoxin, or may be unaffected in value.

· Some material courtesy of Mark Diekman

How was the concept of Mycotoxins developed?

· An outbreak of an unknown disease killed poultry birds in 1960s

· This was named Turkey X disease

· After investigations it was finally traced to mycotoxins in groundnut meal feed imported from Brazil

· The feed was shown to contain a compound that could cause cancer

· Today we know this mycotoxin by the name of AFLATOXIN – A CLASS I CARCINOGEN

Brief History of Mycotoxins

· affected humans for thousands of years.

· Middle Ages had outbreaks of ergotism.

· Only in last 30-40 years have scientists been able to isolate specific toxins from their fungal source.

· Research ideas and methodologies, in this field, change frequently, and data from 20 years ago are considered questionable.

· Alimentary toxic aleukia-killed over I lakh people

· Stachybotryotoxicosis-killed thousands of horse

[image: ]Information About Fungus

· Range from single cells to fruiting bodies that form molds, mushrooms, smuts, and yeasts.

· Absorb nutrients from living or deceased organisms, contain no chlorophyll.

· If multicellular, they have tubular filaments called hyphae that branch out.

· Reproduce using spores

How many mycotoxins are there?

· Today 300 - 400 mycotoxins are known

· Mycotoxins of human concern based on toxicity:

· Aflatoxin

· Deoxyniva-lenol (DON) or Vomitoxin  Zearalenone

· Fumonisin  T-2 toxin  Ochratoxin A

Mycotocins “Factors causing variation on effects”:

Some Mycotoxins are formed in the field, some in storage:

· Storage conditions that favor production of mycotoxins:

· Temperature (40 - 90o F ; 4 - 32o C)

· Relative Humidity (> 70%)

· Moisture (22-23% in grain)

· Oxygen (1-2%)[image: ]

Common toxigenic fungi

[image: ]

Mycotoxin Chain of Events

[image: ]

Modes of Spore Transmission

· Airborne, wind or indoor ventilation systems.

· Attachment to insects of birds, thus transmitted from plant to plant, or animal to animal, etc.

· Via transportation mechanisms such as trucks, crop machinery, etc.

Route of infection

Mycotoxins in corn

Common Mycotoxins

· Cool, wet weather Fusarium Toxins

· Deoxynivalenol (DON or Vomitoxin)

· Considered a “marker”

· T-2 toxin (T-2)

· Zearalenone (F-2)

· Fumonisin

· Hot, humid weather

· Aflatoxin

[image: ]

Toxicity of Mycotoxins

· Acute

· Chronic

· Mutagenic

· Teratogenic

Acute toxicity

· Deterioration of liver and kidney functions, leading to death in extreme cases

· Interference with protein synthesis

· Skin sensitivity affected

· Necrosis of skin

· Immunodeficiency

· Neurotoxins cause trembling in small doses and brain damage or death in slightly higher doses

Chronic toxicity

· Induction of cancer (Liver, oesophagus)

· Induction of tumors

· Induction is never detected at the time of ingestion and remains undetected till the disease is advanced

Mutagenic & Teratogenic toxicity

· Replication of DNA is affected producing mutagenic and teratogenic effects

Determination of mycotoxins

Potential uses of mycotoxins

· Medical application –

· Trichothecenes are known to possess antileukaemic activity;

· zearalenone derivatives have been considered as potential treatment for menopausal syndrome in women;

· Agriculture application – derivatives of zearalenone as growth promoter in sheep and cattle; otherhave been considered for use as herbicides and insecticides.

Effects of Molds/Mycotoxins

· Molds - Decrease digestibility (5%)

· Decrease production (5-10%)

· Mycotoxins – Impact on milk production, weight gain greater than molds

· Mimic other herd health problems

· Depressed immune system

· Off-feed

· Diarrhea

· Hemorrhaging

· Abortions

· Reproduction issues

Health effects of mycotoxins

· Acute and chronic effects on both humans and livestock

· Mycotoxins are believed to be among the most potent known carcinogens

· Effect range from immediate toxic responses & immunosupression to potential long-term teratogenic, estrogenic, & carcinogenic effects.

· Possible health effects due to airborne exposure (exposure to airborne spores with mycotoxins)

Human mycotoxicosis

In 1967, 26 Taiwanese in a farming community became ill after eating contaminated rice; 3 children died.

Cause of death: Contaminated rice showed >200 µg aflatoxin B1/kg.

In 1974, an outbreak of hepatitis in India affected 400 people resulting in 100 deaths;

Cause of death: aflatoxins in corn ( >15 mg/kg)

In 2004, one of the largest aflatoxicosis outbreak occurred in rural Kenya resulting in 317 cases and 125 deaths.

Cause of death:

corn contaminated with 4",400 µg/kg of aflatoxin B1, 220 times higher than Kenyan regulatory limit for food.

Mycotoxin Toxicity: Effect on Humans

· Physiological and pathological changes

· Food poisoning

· Inhibition of protein synthesis & Alteration of capacity of cells to proliferate

· Increase of tryptophan in blood and brain (affects appetite, muscular co-ordination and sleep

· Nausea ",Vomiting

· Headache

· Abdominal pain, Diarrhoea Giddiness

· Convulsions

· Reproductive and mammary changes

· Role in hormonal balance and breast cancer

· Precocious pubertal changes in children

· Breast enlargement in boys

· Role in cancer

· Immunosuppressor

Symptoms of Mycotoxicosis

1. Drugs and antibiotics are not effective in treatment.

2. The symptoms can be traced to foodstuffs or feed.

3. Testing of said foodstuffs or feed reveals fungal contamination.

4. The symptoms are not transmissable person to person.

5. The degree of toxicity is subject to persons age (more often in very young and very old), sex ( more often in females than males)and nutritional status.

6. Outbreaks of symptoms appear seasonally.

Mycotoxin Effects on 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 in animals.

some important [image: ] mycontoxins

F. graminearum in Maize (Corn)

· Produces the toxins: DON & zearalenone (ZEN), and T-2 toxins.

· [image: ]Have damaging effects on plants, humans, and other animals with monogastric digestive processes.

F. moniliforme-corn

· Plant pathogen most associated with corn. Also found in rice, sorghum, yams, hazelnuts, pecans, and cheeses.

· Diseases

· “crazy horse disease” in horses",

· pulmonary edema in pigs",

· liver cancer in rats",

· bone malformation in chicks and pigs.

· esophageal cancer in humans.

· Other toxins produced include fusaric acid, fusarins, and fusariocins.

· Advisory levels are 5 ppm in animal feed.

DON and T-2 Toxin

· trichothecenes of wheat, grain, and barley.

· necrosis and hemorrhage of the digestive tract, decreased blood production in the bone and spleen, and changes to reproductive systems.

· In poultry, causes reduced egg production, beak lesions, and abnormal feathering

· Optimal temperature range is between 70 and 85 degrees Fahrenheit.

· Advisory level of DON is 1 ppm.

Alimentary Toxic Aleukia (ATA)

· During World War II, in Soviet Union, corn grain left to over-winter becomes contaminated with T-2 toxin.

· Severe mycotoxicosis occurs.

· burning in the mouth, esophagus, tongue & stomach.

· Bone marrow formation is halted & anemia develops.

· Hemorrhage of nose, gums, mouth and stomach occurs.

Zearalenone

· Species : Fusarium roseum, F.graminearum, F. poae, F. culmorum

· Food affected: corn, wheat, barley, oats

· Interesting facts:

· Zearalenone has estrogenic effects.

· Mimics the body’s production of estrogen.

· Lengthened or absent estrous cycle

· Causes feminization of male animals.

· Prepuberal gilts show enlarged, swollen vulva as if in estrus

· Interrupted reproductive cycles infemale swine

· Prolapse of the vulva possible

· Little or no effect on growth

· Pigs are especially sensitive, poultry and cows show little sensitivity

Alternaria Toxins

· wheat, sorghum, and barley.

· Also fruits and vegetables that can cause spoilage in refrigeration.

· Toxins include: alternariol, alternariol monomethyl ether, altenuene, tenuazonic acid, and altertoxins.

· Little is know of these toxins; but, toxic effects are seen in rats, chicks, ducklings, and turkeys.

Claviceps Toxins

· Earliest recognized mycotoxicosis caused by C. purpurea, with ergot mold.

· Outbreaks have been reported since 857 A.D.

· [image: ]Humans consumed bread baked with grain containing ergot spores, which produced lysergic acid diethylamide (LSD) symptoms and hallucinations.

Ergot Poisoning (St. Anthony’s Fire)

Species: Claviceps purpurea, and Aspergillus and Penicillium

Affected foods :- rye, barley, wheat, and oats

Interesting facts:

· First documented case of ergot poisoning was in 857. [5]

· Ergot contains a chemical precursor to lysergic acid (LSD).

•Disease of barley, oats and wheat.

•Grains are replaced by ergot sclerotia that contain toxins.

•Main toxin is called ergotamine.

[image: ]•Named for the belief that a pilgrimage to the shrine of St. Anthony would

alleviate the symptoms.

Animal symptoms:

Human symptoms:

· Dry gangrene",

· Internal bleeding",

· Vomiting",

· Constipation",

· Diarrhea, and

· In pigs: abortion of fetuses.

· Gastrointestinal;

· stress; convulsions;

· Fetal abortion;

· Extreme burning and Cold sensations in Fingers, hands, & feet;

· Gangrene of extremitie

·

Aspergillus Toxins

· more than 100 species, 50 of which are known to produce mycotoxins.

· Aspergillus niger is used to make artificial citric acid; one use is in soft drinks.

· Miso, soy sauce, and sake use strains of A. oryzae.

Cotton, peanut, maize, spices, pistachoos

Aspergillus and Aflatoxin

· Aflatoxicosis: caused by high doses in short intervals or low doses in high intervals.

· 1961, caused the deaths of over 100",000 turkey poults: “Turkey X disease”.

· Toxin was traced to contaminated Brazilian peanut meal in poultry feed.

· Grows best between 80-90 degrees Farenheit.

· Damage to grain increases

Aflatoxin

1. Sources :Corn, peanuts

2. Factor favoring production of aflatoxins

1) Temperature : 25-30 c

2) Grain moisture

highly toxic carcinogenic secondary metabolites produced by fungi namely:-

1. 1.Aspergillus flavus

2. 2.Aspergillus parasiticus

3. 3.Aspergillus nomius

Types of Aflatoxins

· Naturally produced Aflatoxins –B1, B2, G1, G2

· They undergo modifications during cellular metabolism and processing of foods to produce several derivatives such as M1, M2, P1, etc.

· International limit 15mg per kg food

Aflatoxin B-1

· most potent aflatoxin

· Classified as Class I Human carcinogen

· selectively targets human gene

· p53 described as ‘Guardian of the genome’

· Definite link to cancer in animals.

· Primarily attacks the liver, in cases of cirrhosis, necrosis",& carcinomas with a secondary affect immune suppression.

· Risk factor for neonatal jaundice, in areas of maternal consumption.

· Does not stay in the body for long periods of time, usually excreted within 96 hours, in animals.

· In milk, for human consumption, advisory level is .5 ppb.

AFLATOXIN EFFECTS

· Inhibits protein synthesis

· Poor gain

· Liver damage

· Susceptibility to Infection

· Residues / carcinogenicity

· Reproduction in swine not

· primarily affected

Penicillium Toxins

· Large genus with over 150 species.

· Discovered antibacterial properties within genus, causing production of penicillin.

· 100 species have mycotoxins.

· Nine specific toxins affecting human health are citreoviridin, citrinin, cyclopiazonic acid, ochratoxin A, patulin, penitrem A, PR toxin, Roquefortine C, and, Secalonic acid D.

· Separated into two groups: those that affect liver and kidneys, and those that are neurotoxic.

· Liver and kidney toxins are asymptomatic and cause overall animal debility.

· Neurotoxins cause visible trembling.

Ochratoxin A and Citrinin

· Affects kidney function.

· Causes Balkan nephropathy and Yellow Rice Fever in humans.

· Chickens, turkeys, and ducklings are affected by

· ochratoxicosis, causing poor weight gain, egg output, and poor shell quality.

· Ochratoxin sources are peanuts, pecans, beans, dried fruit and dried fish.

· Citrinin sources are in wheat, rice, corn, and flour.

· Citrinin is most associated with horses, pigs, dogs, and poultry.

[image: ]

Ochratoxin A

· Species: P. Verrucosum and A. ochraceus

· Food affected: Cereals, coffee beans, and grapes.

· Interesting Facts: Ochratoxin can be transmitted from pork to humans by eating pork that is fed with contaminated food.

Cyclopiazonic Acid (CPA)[image: ]

· Found in corn and peanuts in Georgia.

· Chief species from Penicillium causes cheese spoilage.

· Causes fatty degeneration in liver and kidneys in animals, chickens are very susceptible.

· May act synergistically with aflatoxin

[image: ]

Types of Tests for Mycotoxins

· Quick Test (Qualitative)

· Immunoassays (Elisa tests)

· Thin Layer Chromatography (TLC)

Use: (Detect Specific Mycotoxin)

· Confirmatory Tests (Quantitative)

· High Pressure Liquid Chromatography(HPLC)

Use: Determine level of mycotoxins, Detect several mycotoxins

Managing Moldy/Mycotoxin Problems

· Ensure adequate levels of vitamins (A",E",B-1) and minerals (Se",Cu",Zn",Mn).

· Include aluminosilicate or bentonite in ration

· Dilution is the solution.

· Reduce intake of contaminated feeds.

· Eliminate highly contaminated feeds.

· Remove moldy layers of feed before feeding.

Quick Toxin Review

[image: ]

Future Fight Against Mycotoxins

· Have farmers select strains resistant to contamination.

· Scientists hope to genetically engineer plants resistant to fungal infection.

· Use feed additives that sequester the toxins and prevent absorption from the gastrointestinal tract.

Species, breed

Age

Sex

Nutritional status

Other diseases

other mycotoxins

Extent of exposure

Ingestion/skin contact/ in halation

Blood stream & lymphatic system

Inhibit protein synthesis

Damage macrophages system

Inhibit particle clearance of the lungs

Increase sensitivity to bacterial endotoxins

Aflatoxins

Tricothecenes

Fumonisins

Presumptive tests

Biological assays

Chemical analysis

Fusarium

plant pathogens à in soil

graminearum- Wheat

Causes scab damage to kernels and head blight. Produces deoxynivalenol (DON), also called vomitotoxin.

corn, wheat, barley, beans",

Trichothecene toxins target the circulatory, alimentary, skin, and nervous systems.

pg. 1

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