Mycotoxins Flashcards
What are mycotoxins?
- Metabolites of fungi, recongized as toxic to other life forms
- 400+ mycotoxins based on experimental or field conditions
- relatively stble once formed
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How are mycotoxins formed?
environmental & crop stress + genetic effect turns basic nutrients into secondary metabolites for survival or defense
What are the major mycotoxins from grains in North America
- Aflatoxins
- Trichothecenes (DON)
- Zearalenone
- Ergot
- Fumonisins
- Ochratoxin
- Citrinin
- Penitrem A
- Roquefortine
- Patulin
- Mycophernolic acid
- Penicillic acid
- Wortmannin
- Gliotoxin
- Sterigmatocystin
- Verruculogen
- Alternariol
What are the major mycotoxins from foragess in North America
- Ergovaline (fescue)
- dicoumarol (sweet clover)
- Slaframine (red clover)
- Paspalitrem (dallis grass)
- lolitrem B (ryegrass)
- Sporodesmin
- 2-bromo-alpha-ergocryptine
- Ergometrine/ergonovine
- Ergotamine
- Lysergol
- Methylergonovine
What factors influence mycotoxin production?
- Plant varieties
- Climate and Wather
- Crop monoculture
- Seed coat damage
- Insect transport
- Storage quality
- Milling practices
What are the mycotoxins of most concern?
- Aflatoxin
- Deoxynivalenol
- T2
- Ergot
- Fumonisins
- Ochratoxin
- Zearalenone
Where does Aflatoxin come from?
- Aspergillus flavus
- A. parasiticus
What are the common substrates for aflatoxin?
- Corn
- milo
- cotton seed
- peanutes
What are the factors that favor aflatoxin formation?
- Temperatures 78-90F
- Drought stress, insect damage
- High relative humidity or grain moisture
What is the MOA of Aflatoxin?
- Metabolized to epoxide that binds to nucleic acids
- Inhibit protein synthesis ⇢ liver damage
- Carcinogen in laboratory animals
What is aflotoxin’s affect on immune function?
- Both humoral and cell-mediated
- Reduces resistance to several infectious diseases
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What are the effects of Aflatoxin?
- Reduced growth & productivity
- hepatic lipidosis & necrosis
- chronic hepatic damage
What are Trichothecene mycotoxins?
- Complex sesquiterpenes with an epoxide ring
- Fusarium spp. produces 60 toxins, mainly T-2, diacetoxyscirpenol, deoxynivalenol (DON)
- Favored by cool temperatures or alternating cool and warm temperatures, higher moisture
- Fusaria in storage require >20% moisture for optimum growth and toxin formation
What are the effects of Trichothecene?
- Radiomimetic Syndrome (pancytopenia, diarrhea)
- Irritant and necrotizing to mucosae and skin
- Lymphoid depletion - GI tract
- Thymic involution/suppression
- Some aspects of immunosuppression - mainly cell mediated immunity
- Rapidly metabolized and excreted
What mycotoxins come from Fusarium spp?
- Deoxynivalenol (DON) - F. graminearum and culmorum
- Fumonisins
- Zearalenone
What affect does Deoxynivalenol (DON) have?
- Vomitoxin
- Neurochemical effect (serotonin)
- increased levels of serotonin are responsible for the anorexic effect
- Swine most sensitive
- Vomiting @ 5-8 ppm
What are the effects of Zearalenone?
- F-2 toxin or Giberella Toxin
- Hyperestrogenism @ > 1ppm
- Anestrus - retained CL @ > 3ppm
- Embryonic Loss by failed implantation
- luteotropic - NOT abortive in sows
- Decreased libido/fertility in boars
- Infertility in heifers @ >12 ppm
- negative effects on semen quality
What are Fumonisin Mycotoxins?
- Recently discovered (1988)
- FB1, FB2, FB3
- Water soluble toxins
- Swine and Horses most affected
What are the effects of Fumonisins?
- Liver toxicosis is common lesion
- Leukoencephalomalacia in horses
- Pulmonary Edema in swine
- Recently reported as carcinogens
What are the clinical signs of Fumonisin mycotoxin in horses?
(moldy corn poisoning)
- Stumbling
- blind
- ataxia
- depression
- anorexia
- high mortality
What are the clinical signs of Fumonisin mycotoxin in swine?
- Dyspnea
- Cyanosis
- weakness
- death in 3-4 hours
What is the clinical chemistry associated with Fumisin mycotoxin in swine?
- Increased Sphinganine
- Increased Cholesterol
- Elevated LDH
- Increased AST
- High GGT levels
- Increased serum bilirubin
What are sphingolipids
- cell membrane lipids
What molds produce Ochratoxin?
- Aspergillus ochraceus
- Penicillium viridicatum
What are the effects of Ochratoxin and Citrinin?
- Nephrotoxic
- Often accompanied by gastric ulcers
- Depression early
- Urine - low specific gravity
- PD/PU
- Primary lesion - toxic tubular damage
- Survivors may have chronic renal scars
Why are monogastrics more sensitive to Ochratoxin
inactivated in the rumen
What common substrates are sources of Ergot?
- Caused by Claviceps purpurea
- Rye
- Barley
- Wheat
- Oats
- Brome other grasses
What factors favor the production of Ergot?
- humidity
- moderate temperatures
What is the MOA of Ergot?
- Sclerotia containt ergopeptide alkaloids
- Similar in action to ergovaline from tall fescue
- Alkaloids are related to LSD
What affects does Ergot poisoning have?
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Classic lesion - peripheral gangrene
- Peripheral vasoconstriction with dry gangrene, sloughing of feet, tail, ears
- Abortion unlikely
- Inhibit Prolactin release
- Non-inflammatory agalactia
- Neonates starve
- Hyperthermia, heat intolerance in cattle
- Hyperexcitability tremors
How is Ergot poisoning diagnosed?
- Hx, clinical signs
- Lesions
- Examine hay/grain
- sclerotia on wt/wt basis - 0.3% allowed
- Assay for alkaloids in feeds or urine -
- excreted rapidly -need samples within 48 hours after exposure stops
What is Slaframine?
- Formed by Rhizoctonia leguminicola infested Red clover
- causes “black patch”
- Favored by cool wet weather
- Found on clover in fresh pasture, hay, silage
What is the MOA of Slaframine?
- Bio-activated by liver microsomes to a parasympathomimetic quaternary amine vary similar to acetylcholine
- “slobber factor:
What are the clinical affects of Slaframine?
Profuse salivation ~30min post ingestion
What are the Tremorgenic Mycotoxins? sources?
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Penitrem A
- moldy cream cheese, bread, macaroni & cheese, walnutes
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Roquefortine
- Moldy blue cheese, cream cheese, decaying organic matter (compost)
- From Penicillium fungi
What is the MOA of Tremorgenic Mycotoxins
- Indole structure similar to lysergic acid
What are the clinical signs of Tremorgenic Mycotoxins?
- Acute:
- restlessness, panting, excessive salivation, vomiting
- Progressive mild to whole body muscle tremors
- Advanced:
- looks like strychnine
- Tremors more severe
- Hyperresponsiveness to external stimuli
- Seizures
- Hyperthermia, exhaustion, dehydration
How is Tremorgenic Mycotosis diagnosed
- Hx of eating moldy foods
- Compatible clinical signs
- Chemical detection of penitrem A or roquefortine
- vomitus, stomach content, suspect material
How is Tremorgenic Mycotoxicosis treated?
- Control agitation, tremors and seizures
- Diazepam / methocarbamol
- Decontamination with activated charcoal and saline cathartic
- IV fluids
- Revocer in 24-48 hours w/ aggressive treatment
How is Mycotoxicosis diagnosed?
- Circumstantial or hx information
- Mold cultures and spore counts
- Clinical signs
- Lesions and clinical shemistry
- Chemical detection of mycotoxins
- Test feeding of suspect ration
What is the Black light test? (Mycotoxins)
- Visualize grain under UV light
- Useful only for aflatoxin screening
- Measure non-aflatoxin metabolite
- kojic acid
- Not quantitative
- Best if grain is cracked
- Firefly or bright green-yellow fluorescence (BGYF) is positive
How can Mycotoxin formation be prevented?
- Survey weather and crop conditions
- Remove damage grain by screening
- Keep storage facilities clean
- Keep grain cool
- Avoid moisture in storage
- Use feed promptly after milling
- Use mold inhibitors / adsorbents
What are Mold inhibitors?
- Primarily organic acids
- Suppress mold growth
- Do NOT destroy mycotoxins
- Will NOT restore grain quality
What are adsorbents for Mycotoxins?
- Calcium Aluminosilicates are effective for aflatoxins
- Mycosorb alternative adsorbent for aflatoxins and others
- Bentonite is effective for AF
- Sodium metabisulfite & diatomaceous earth limited effectiveness
- Activated charcoal and 25% alfalfa meal effective for zearalenone
What are mycotoxin binders?
- Zeolites and clays
- Cell-wall fraction B-glucan of yeasts
- Glucomannans
- Labels call them:
- preservatives
- Antioxidants
- Amino Acid
- Direct-fed microbials
What are the strategies for preventing mycotoxins?
- Know contaminant levels
- Test suspect feeds
- dilute damaged grain
- Feed to alternative species
- supplement with high quality nutrients
