Delayed organophosphate neurotoxicosis in four heifers.

Oil-containing triaryl phosphates induced delayed organophosphate neurotoxicosis in 4 dairy heifers. Clinical signs developed 10 to 14 days after exposure and included dyspnea, dysuria, polyuria, tympanites, incoordination, hind limb weakness with knuckling of the metatarsophalangeal joints, and flaccid paralysis. Triaryl phosphate concentrations were high in a specimen of fat from 1 heifer, and the fat and 2 waste oil samples used to periodically lubricate a feed bunk motor chain had similar triaryl phosphate-like chromatographic profiles. The diagnosis of delayed organophosphate neurotoxicosis requires history of exposure to a potential toxicant, appropriate histologic evaluation of the CNS and, ideally, identification of the toxic agent from appropriately selected animal tissues.