Ergot-Related Toxicosis

Ergot-Related Toxicosis



Basic Information image



Definition


Claviceps fungi (“ergot”) produce a variety of toxins that can adversely affect the reproductive, circulatory, nervous, and musculoskeletal systems of horses. Claviceps fungi are visible as sclerotia or ergot bodies on susceptible grasses (Table 1) and small cereal grains such as wheat, barley, and oats (but not corn).



TABLE 1 Common Grasses Susceptible to Claviceps Infection

image


Synonyms




• Ergot, ergot poisoning, or ergotism


• Indole alkaloid mycotoxins


image Ergot alkaloids (eg, ergocornine, ergocristine, ergocryptine, ergosine, ergotamine, ergovaline) and compounds related to lysergic acid (LSD) produced by C. purpurea

image Indole-diterpene tremorgenic mycotoxins (ie, paspalinine; paspalitrems A, B, C) produced by Claviceps paspali and other species producing tremorgens


Epidemiology



Species, Age, Sex




• Except for agalactia and pregnancy abnormalities, horses are much less susceptible to ergotism than are cattle.


• The species and age of exposed horses may influence the amount of toxin ingested.


• Aged animals, especially mares, may have concurrent disease that is exacerbated by toxin exposure.


• Age influences the likelihood of mares cycling or becoming pregnant.


• Mares are particularly susceptible to the reproductive effects of ergopeptine alkaloids.



Genetics and Breed Predisposition




• Anecdotal reports suggest that individual animal differences in susceptibility exist.


• Possible differences in breed disposition might reflect influences of risk factors and geography.



Risk Factors




• Claviceps ergopeptine alkaloids:


image Subacute to chronic consumption of the seed head stage of susceptible grasses or ergotized small grains or grass seed

image Concurrent exposure to endophyte-infected tall fescue (see “Fescue-Related Toxicosis” in this section)

image Early and particularly late gestation in mares

image Mares in the spring transitional phase before the onset of normal cyclicity

image “No till” farming practices

image Cool, damp spring weather

image Rye and triticale in horse rations

image Pelletized rations, especially those incorporating screenings

image History of laminitis

image Hot or cold environmental temperatures

image Forced exercise under hot and humid conditions

• Claviceps indole-diterpene tremorgenic mycotoxins


image Several days’ consumption of ergotized Dallisgrass (Paspalum dilatatum) or Bahiagrass (Paspalum notatum) in pasture or hay

image Damp or wet disturbed soils favoring growth of C. paspali and related species

image Concurrent exposure to endophyte (Neotyphodium lolii)-infected perennial ryegrass (Lolium perenne) hay or pasture or other tremorgenic mycotoxins

image Forced exercise


Contagion and Zoonosis


Between grasses but not between animals and/or humans



Geography and Seasonality




• Claviceps ergopeptine alkaloids


image Seen worldwide, but predisposing weather conditions are common in the northern Great Plains and Pacific Northwest regions of North America (more sporadically in Midwestern and Atlantic coastal regions of the United States)

image Cool, wet weather in the spring favors the C. purpurea life cycle.

image Reproductive ergotism is most common in spring when mares are being bred and are foaling.

image Hyperthermic ergotism is most common during hot and humid summers.

image Gangrenous ergotism is most common during extremely cold winters.

• Claviceps indole-diterpene tremorgenic mycotoxins


image Southeastern United States, Central and South America, parts of Europe, Africa, Australia, and New Zealand

image Clinical signs of nervous ergotism or “grass staggers” are most common when rainy or humid summers and autumns favor the C. paspali life cycle


Associated Conditions and Disorders




• Claviceps ergopeptine alkaloids: Fescue toxicosis


• Claviceps indole–diterpene tremorgenic mycotoxins


image Other “grass staggers” syndromes

image Other tremorgenic mycotoxins


Clinical Presentation



Disease Forms/Subtypes




• C. purpurea ergopeptine alkaloids


image Reproductive ergotism: Most common form in horses; observed at low dosages of toxins

image Hyperthermic ergotism: Less common in horses; observed at higher toxin doses than reproductive ergotism

image Gangrenous or cutaneous ergotism: Less common in horses; observed at higher toxin doses than reproductive ergotism

• C. purpurea LSD-like ergot alkaloids, especially C. paspali indole-diterpene tremorgenic mycotoxins: Nervous or convulsive ergotism



History, Chief Complaint




• Generally, multiple animals are affected in instances of ergotism.


• Reproductive ergotism (indistinguishable from most common form of equine fescue toxicosis)


image Agalactia or dysgalactia (may be observed in absence of any other clinical signs)

image Prolonged gestation

image Retained fetal membranes

image Dystocia, premature placental separation (ie, “red bag”)

image Fetal dysmaturity/overmaturity

image Abortion/stillbirth
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  4. Black Widow Spider Toxicosis

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Ergot-Related Toxicosis

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