Hoary Alyssum Toxicosis

Hoary Alyssum Toxicosis



Basic Information image



Definition


Characterized by limb edema and laminitis, hoary alyssum toxicity occurs primarily in horses grazing the plants in pastures or eating the plants when incorporated in hay.



Synonym(s)


Hoary alyssum (Berteroa incana), hoary false madwort



Epidemiology



Species, Age, Sex


Horses are the only domestic animals affected by hoary alyssum.



Risk Factors


The plants are toxic when green and remain toxic for months when dried in hay. Overgrazing favors the invasiveness of this weed.



Geography and Seasonality


B. incana, a member of the Brassicaceae family, is an annual, biennial, or perennial introduced weed that has become naturalized in most areas of North America. Stems are gray-green, hairy (hoary), 1 to 3 feet tall, with many branches near the top. Leaves are gray-green, hairy, alternate, oblong, narrow, 0.5 to 3 inches long, with smooth edges. Flowers are white with four deeply divided petals. Seed pods are hairy and oblong with short beaks on the end (Figure 1).


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FIGURE 1 Hoary alyssum (Berteroa incana).



Clinical Presentation



History, Chief Complaint


Edematous swelling of the legs, lameness and, in severe cases, laminitis



Physical Exam Findings


Lameness caused by distal limb edema and laminitis is a typical sign of hoary alyssum poisoning. Experimentally horses fed hay containing 30% hoary alyssum develop pyrexia, an increased digital pulse, and limb edema within 24 hours. Severe laminitis with rotation of the third phalanx may occur in severe cases. Red-colored urine (hemoglobinuria) as a result of red blood cell hemolysis and hemorrhagic diarrhea have been reported in pregnant mares fed alfalfa hay containing hoary alyssum. Late-term abortion is reported in pregnant mares. Death may occur in 1% to 2% of natural cases of hoary alyssum poisoning.

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Hoary Alyssum Toxicosis

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