Arsenic exists as both inorganic and organic compounds. Inorganic arsenicals are little used today except in a few rodenticides, insecticides and weed killers.

Organic arsenicals are less toxic than the inorganic ones and are used in some countries to control swine dysentery, to treat eperythrozoonosis or as growth promoters. The common chemicals are arsanilic acid, sodium arsanilate, roxarsone (3-nitro - 4-hydroxyphenyl arsonic acid) and carbasone.

Clinical signs

Poisoning with inorganic compounds results in acute illness with severe damage to the intestinal tract. Clinical signs include vomiting, acute diarrhoea and colic, dehydration, convulsions, collapse and death.

The onset of clinical signs in organic arsenical poisoning vary according to the level of intake. At low levels nothing may be seen for two to three weeks, when mild signs of incoordination and possibly blindness occur. With high doses clinical signs may be seen within two to three days, as incoordination, paralysis of the hind legs and blindness. The blindness is often irreversible. Affected animals continue to grow if they can get to feed and water. Very high doses of organic arsenicals may cause gastro-enteritis.

This is determined by the history, availability of arsenical compounds and analysis of feed or suspect substances.

Treatment

There is no effective antidote but if the compounds are removed immediately most pigs recover.