Poisoning can be seen in swine due to an overdose of organo-
arsenicals, which are often used as feed additives to promote
growth and to control swine dysentery. With
3-nitro-4-hydroxyphenylarsonic acid (“3-nitro”) poisoning, there
is degeneration of the spinal cord, optic nerve, and peripheral
nerves. Clinical signs consist of tremors and paraparesis.
Mildly affected animals can recover after withdrawal of the
offending feed. (Also see Arsenic Poisoning.) Delayed
Organophosphate Intoxication Intoxication can be seen after oral
or topical administration of organophosphate-containing
insecticides or anthelmintics, including haloxon. In addition to
the acute signs, delayed paralysis can develop 1–4 wk after
exposure. Suffolk sheep have an inherited predisposition to this
neurotoxicity because they have low levels of plasma
arylesterase activity. Affected animals have progressive,
symmetric paraparesis and occasionally become tetraplegic.
Diagnosis is based on clinical signs and history of exposure. On
histopatho