Acute toxicity of tri-ortho-cresyl phosphate in sheep and swine

Tri-ortho-cresyl phosphate (TOCP) was given orally or by subcutaneous (SC) injection to sheep and swine. Sheep given oral doses of 100, 200, or 400 mg of TOCP/kg of body weight developed an acute intoxication characterized by diarrhea dehydration, metabolic acidosis, and death within 6 days. Daily SC injections of TOCP in sheep caused either death or delayed neurotoxicosis depending upon the dosage. Increase of aspartate aminotransferase activity approximately 24 hours before the animal died and histopathologic changes confirmed that liver injury had occurred. Swine dosed with 100 to 1,600 mg of TOCP/kg had minimal signs of acute toxicosis, but developed severe delayed neurotoxicosis in approximately 15 days. Those given a 800 mg/kg dose by the oral route or SC injection had severely decreased serum acetylcholinesterase activity. In the swine which were euthanatized at 7 days after treatment, histopathologic examinations revealed no lesions (although the nervous system was not examined, because clinical neurologic signs were normal).