lecture #3: Fungus Flashcards
what is fungus?
a plant like organisms which grow by continuous extension and branching (hyphae)
why are fungi difficult to kill?
because they are eukaryotes and are similar to host cells, which makes it difficult to kill them without causing host cell damage
Most pathogenic fungi are ___________.
dimorphic
what are some types of fungi morphology? give an example of each.
- some grow only as yeasts (Cryptococcus)
- some grow only as molds (Aspergillus)
mold growth is favored by ________ temperatures and ________ moisture content.
HIGH, HIGH (>13% in corn, >12% in soy beans)
what are some examples of fungi toxins or mycotoxins?
- Aflotoxicosis: aflotoxins (Ex: Aspergillus flavus and Aspergillus parasiticus)
- Estrogenism: zearalenone or F2 toxin (Ex: Fusarium graminearum)
- Leukoencephalomalacia: fumonisins (Ex: Fusarium moniliforme and Fusarium proliferatum)
- Ergotism: ergot alkaloids (Ex: Claviceps purpurea)
what are some qualities regarding Alflatoxicosis?
- growth on peanuts, cottonseed meal, soybeans, sorghum, corn (high moisture and temp)
- susceptible: poultry, pigs, cattle, sheep, dogs,
- adult cows, sheep and goat are more resistant to the acute form
- dietary lvls of aflotoxins< 50ppb are tolerated
- aflotoxin metabolites can be excreted in milk of cattle
what is the pathogenesis of alflatoxicosis?
- aflotoxins bind to nucleic acid and nucleoproteins
- liver is the primary organ affected
what are some toxic effects of aflatoxicosis pathogenesis?
- mutagenesis
- affect protein synthesis and function (metabolic enzymes and structural proteins)
- decrease lipid metabolism
- mitochondrial respiration
- cause immunosuppression
what do high doses (acute toxicity) of aflotoxins cause?
hepatocellular necrosis with fatty accumulation, icterus and hemorrhages. Death can occur after a short period of inappetence (>1000ppm)
what do low dosees (chronic toxicity) of aflotoxins cause?
- liver enlargement with fibrosis
- edema of gallbladder
- tubular degeneration in the kidneys
- decreased feed intake and feed conversion, reduce weight gain, eggs or milk production reduced, immunosuppression
What do Zearalenone or F2 toxin typically contaminate?
growing plants and stored feeds (corn, wheat, barley, sorghum)
what is a characteristic of Zearalenone (F2 toxin)?
it is a potent estrogen and binds to estradiol receptors
what are some other toxins binding to estradiol?
- vomitoxin
- fumosin
- moniliformin
- DAS
what can Zearalenone (F2 toxin) cause in pigs?
- vulvovaginitis,
- hypertrophy of mammary gland and uterus,
- reduce fertility and litter size,
- cause fetal mortality and anestrus,
- affect spermatogenesis (testicular atrophy),
- reduce feed intake
what can F2 toxin cause in cattle?
- affect fertility
- cause abortion
- vaginal discharge
- nymphomania
- weight loss
what can F2 toxin do to chicken?
- can cause digestive problems
- reduce feed intake
- mucosa lesions
- affect bone marrow and lymphoid organs
what causes Equine leukoencephalomalacia?
- Fumonisins toxins (B1, B2,& B3)
- feeding of moldy corn for several weeks
which animals are effected by leukoencephalomalacia? what happens to them?
horses, mules and donkeys.
neurological disorders: muscle tremors, blindness, paralysis or facial and pharyngeal muscles (Can’t swallow), circling, hyperesthesia, ataxia, depression, recumbence,
leukoencephalomalacia also affects pig, cattle and sheep and poultry. what happens to them?
pig: pulmonary edema, dyspnea (shortness of breath), cyanosis of mucosa membrane, weakness, abortion , death
cattle, sheep & poultry: inappetence, weight loss, liver damage
what is the characteristic lesion of equine leukoencephalomalacia?
lesion that is liquefactive necrosis of white matter of the cerebrum. some horses have hepatic necrosis
What causes Ergotism?
ingestion of sclerotia of the parasitic fungus Claviceps purpurea, which replace the grain of rye and other small grains or forage plants (bluegrasses, ryegrasses) the black sclerotia may contain varying quantities of ergot alkaloids (ergotamine and ergometrine)
what animals can ergotism affect?
cattle, sheep, pigs & poultry
what does ergotism cause?
- arteriolar spasm (vasoconstriction)
- endothelial cell injury and restrict circulation
- blood stasis can lead to necrosis of extremities due to thrombosis (mainly in a cold environment)
