Delayed neuropathy in pigs induced by isofenphos

In 1990 an outbreak of ataxia occurred in over 700 pigs in the north of England. Epidemiological studies demonstrated that the disorder was associated with the consumption of feed from a particular supplier and that one component (wheat screenings) was common to the batch of feed with which the ataxia was associated. An analysis of the feed demonstrated the presence of an organophosphorus pesticide, later identified as isofenphos, a pesticide not approved for use in the United Kingdom. The wheat screenings had been imported from France and the warehouse in which they had been stored was contaminated with isofenphos, which is approved for restricted use in France. Isofenphos is known to cause delayed neuropathy. The dose to which the pigs were theoretically exposed would be expected to have resulted in neuropathy (manifested as ataxia).