VPT 421: Veterinary Toxicology (2+0)

SIGNS AND TREATMENT 

Signs

• In the horse
  • Horses generally must consume bracken fern for 1 - 2 months before the onset of clinical signs occurs. Clinical signs can also occur even when horse is no longer on bracken fern.
  • Emaciation.
  • Loss of weight occurs despite maintenance of appetite until the late stages of the disease.
  • Lethargy.
  • Incoordination, especially when forced to walk.
  • Severe tremors, unable to arise, injuries from attempts to get to feet; most pronounced when attempt to work animal.
  • Bradycardia with arrhythmias seen early in disease course. Weak and fast pulse
  • Convulsions, recumbency, and opisthostonus terminally. Hyperthermia also observed terminally.
  • Hemolytic crisis rarely reported.
  • If not treated, death in 2 - 10 days (occasionally survive up to 30 days or more after onset).
• In cattle
  • Thiamine production in the rumen results in resistance to the thiaminase syndrome seen in horses.
  • Disease develops as a result of bone marrow suppression.
  • Early fever (106 - 108º F).
  • Loss of condition, anorexia.
  • Anemia (late).
  • Bracken fern-induced hematuria in cattle is called bovine enzootic hematuria.
  • Leukopenia.
  • Thrombocytopenia, blood-tinged nasal discharges, bloody or "tarry" feces, blood clots in feces, hematuria. Prolonged clotting times, defective clot retraction.
  • Edema of larynx and dyspnea.
  • Differential diagnosis in cattle includes: septicemia, anaplasmosis, moldy sweet clover ingestion, and leptospirosis.

Treatment

• In horses
  • Use of saline cathartic activated charcoal and thiamine hydrochloride administration
• In cattle
  • Blood transfusions, use of broad spectrum antibiotics, d,1-batyl alcohol, protamine sulfate (1%), a heparin antagonist administration as an injection, in conjunction with blood transfusions may be of benefit.