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Diazinon toxicity in sheep and cattle arising from the misuse of unlicensed and out-of-date products
  1. R. T. Sharpe, BVETMED, BA, BSC, MSC, MA, MRCVS1,
  2. C. T. Livesey, BVSC, MSC, MRCVS2,
  3. I. H. Davies, MA, VETMB, MRCVS3,
  4. J. R. Jones, BVSC, MRCVS4 and
  5. A. Jones, BSC, MSC5
  1. 1 Veterinary Laboratories Agency — Penrith, Merrythought, Calthwaite, Penrith ca11 9rr
  2. 2 Veterinary Laboratories Agency — Weybridge, Woodham Lane, New Haw, Addlestone, Surrey kt15 3nb
  3. 3 Veterinary Laboratories Agency — Shrewsbury, Kendal Road, Harlescott, Shrewsbury sy1 4hd
  4. 4 Veterinary Laboratories Agency — Carmarthen, Job's Well Road, Johnstown, Carmarthen sa31 3ez
  5. 5 Central Science Laboratory, Sand Hutton, York yo41 1lz


Two incidents involving the misuse of unlabelled or out-of-date diazinon products are described. In the first incident, 81 of a group of 210 five-month-old lambs died within 12 hours of being dipped with the contents of a partly used tin of 15-year-old sheep dip. Analysis showed that the diazinon had decomposed by hydrolysis into a range of breakdown products, including tetraethyldithiopyrophosphate (sulfotepp) and monothiono-tetraethylpyrophosphate (monothiono-tepp), which are much more toxic to mammals than diazinon. In the second incident, four yearling bulls were affected within 48 hours of being treated with a liquid that the farmer believed to be a lice treatment but was actually old diazinon sheep dip. Three of the bulls recovered but one died four days after the treatment. Analysis of the dip confirmed the presence of diazinon but in this incident no breakdown products were detected.

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