Mycotoxins Flashcards
1
Q
What are mycotoxins?
A
- 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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2
Q
How are mycotoxins formed?
A
environmental & crop stress + genetic effect turns basic nutrients into secondary metabolites for survival or defense
3
Q
What are the major mycotoxins from grains in North America
A
- Aflatoxins
- Trichothecenes (DON)
- Zearalenone
- Ergot
- Fumonisins
- Ochratoxin
- Citrinin
- Penitrem A
- Roquefortine
- Patulin
- Mycophernolic acid
- Penicillic acid
- Wortmannin
- Gliotoxin
- Sterigmatocystin
- Verruculogen
- Alternariol
4
Q
What are the major mycotoxins from foragess in North America
A
- Ergovaline (fescue)
- dicoumarol (sweet clover)
- Slaframine (red clover)
- Paspalitrem (dallis grass)
- lolitrem B (ryegrass)
- Sporodesmin
- 2-bromo-alpha-ergocryptine
- Ergometrine/ergonovine
- Ergotamine
- Lysergol
- Methylergonovine
5
Q
What factors influence mycotoxin production?
A
- Plant varieties
- Climate and Wather
- Crop monoculture
- Seed coat damage
- Insect transport
- Storage quality
- Milling practices
6
Q
What are the mycotoxins of most concern?
A
- Aflatoxin
- Deoxynivalenol
- T2
- Ergot
- Fumonisins
- Ochratoxin
- Zearalenone
7
Q
Where does Aflatoxin come from?
A
- Aspergillus flavus
- A. parasiticus
8
Q
What are the common substrates for aflatoxin?
A
- Corn
- milo
- cotton seed
- peanutes
9
Q
What are the factors that favor aflatoxin formation?
A
- Temperatures 78-90F
- Drought stress, insect damage
- High relative humidity or grain moisture
10
Q
What is the MOA of Aflatoxin?
A
- Metabolized to epoxide that binds to nucleic acids
- Inhibit protein synthesis ⇢ liver damage
- Carcinogen in laboratory animals
11
Q
What is aflotoxin’s affect on immune function?
A
- Both humoral and cell-mediated
- Reduces resistance to several infectious diseases
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12
Q
What are the effects of Aflatoxin?
A
- Reduced growth & productivity
- hepatic lipidosis & necrosis
- chronic hepatic damage
13
Q
What are Trichothecene mycotoxins?
A
- 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
14
Q
What are the effects of Trichothecene?
A
- 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
15
Q
What mycotoxins come from Fusarium spp?
A
- Deoxynivalenol (DON) - F. graminearum and culmorum
- Fumonisins
- Zearalenone
16
Q
What affect does Deoxynivalenol (DON) have?
A
- Vomitoxin
- Neurochemical effect (serotonin)
- increased levels of serotonin are responsible for the anorexic effect
- Swine most sensitive
- Vomiting @ 5-8 ppm
17
Q
What are the effects of Zearalenone?
A
- 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
18
Q
What are Fumonisin Mycotoxins?
A
- Recently discovered (1988)
- FB1, FB2, FB3
- Water soluble toxins
- Swine and Horses most affected
19
Q
What are the effects of Fumonisins?
A
- Liver toxicosis is common lesion
- Leukoencephalomalacia in horses
- Pulmonary Edema in swine
- Recently reported as carcinogens
20
Q
What are the clinical signs of Fumonisin mycotoxin in horses?
(moldy corn poisoning)
A
- Stumbling
- blind
- ataxia
- depression
- anorexia
- high mortality
21
Q
What are the clinical signs of Fumonisin mycotoxin in swine?
A
- Dyspnea
- Cyanosis
- weakness
- death in 3-4 hours
22
Q
What is the clinical chemistry associated with Fumisin mycotoxin in swine?
A
- Increased Sphinganine
- Increased Cholesterol
- Elevated LDH
- Increased AST
- High GGT levels
- Increased serum bilirubin
23
Q
What are sphingolipids
A
- cell membrane lipids
24
Q
What molds produce Ochratoxin?
A
- Aspergillus ochraceus
- Penicillium viridicatum
25
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
26
Why are monogastrics more sensitive to Ochratoxin
inactivated in the rumen
27
What common substrates are sources of Ergot?
* Caused by *Claviceps purpurea*
* Rye
* Barley
* Wheat
* Oats
* Brome other grasses
28
What factors favor the production of Ergot?
* humidity
* moderate temperatures
29
What is the MOA of Ergot?
* Sclerotia containt ergopeptide alkaloids
* Similar in action to ergovaline from tall fescue
* Alkaloids are related to LSD
30
What affects does Ergot poisoning have?
* **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
31
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
32
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
33
What is the MOA of Slaframine?
* Bio-activated by liver microsomes to a parasympathomimetic quaternary amine vary similar to acetylcholine
* "slobber factor:
34
What are the clinical affects of Slaframine?
Profuse salivation ~30min post ingestion
35
What are the Tremorgenic Mycotoxins? sources?
* **Penitrem A**
* moldy cream cheese, bread, macaroni & cheese, walnutes
* **Roquefortine**
* Moldy blue cheese, cream cheese, decaying organic matter (compost)
* **From** ***Penicillium*** **fungi**
36
What is the MOA of Tremorgenic Mycotoxins
* Indole structure similar to lysergic acid
37
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
38
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
39
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
40
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
41
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
42
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
43
What are Mold inhibitors?
* Primarily organic acids
* Suppress mold growth
* Do NOT destroy mycotoxins
* Will NOT restore grain quality
44
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
45
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
46
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
