Organophosphorus Sheep Dips

A number of more specific issues also arose. These included adverse reactions to products containing imidacloprid, sprays containing dichlorvos and, as already mentioned, the organophosphorus sheep dips. 

Figure 15.2 Suspected adverse reactions to organophosphorus sheep dips.

The labelling for organophosphorus sheep dips in the UK has been strengthened. These are now required to carry a skull and crossbones symbol and the words TOXIC IF SWALLOWED. There is also advice on suitable... 

T. C. Marts and P. Edwards, Medicines used to control and treat external parasites of sheep - toxicology and the phenomenon of reported adverse human responses to organophosphorus sheep dips, in Veterinary Phar-macovigilance. Adverse Reactions to Veterinary Medicinal Products, ed. K. N. Woodward, Wiley-Blackwell, Chichester, 2009, pp. 518-527. 

Veterinary Products Committee, Report on Organophosphorus Sheep Dips, VPC, November, 1999. 

The numbers of adverse reactions in humans reported to the VMD is shown in Figure 15.1 for the period 1985 to 2010. The increase in reactions in the early 1990s is probably due to a number of factors including the greater publicity given to the scheme and to its applicability to human adverse reactions. In addition, at about the same time, there was an increased interest in a specific topic, namely suspected adverse reactions to organophosphorus-containing sheep dips, and the numbers of reports for these rose dramatically. This will be discussed later in this chapter. 

The OP dips (and sprays) have long been used for the treatment and attempted eradication of sheep scab. This disease has major animal welfare implications for the sheep and major economic implications for the farmer. The disease can result in loss of the fleece and severe lesions on the animal that are then open to secondary infection by bacteria and parasites. The disease is caused by the sheep scab mite Psoroptes ovis. Organophosphorus-based dips have long been used for the treatment and attempted eradication of the disease. In this process, animals are submerged in the dip bath fluid so that the entire body surface, including the head, is submerged. They then exit the bath and in... 

The numbers of environmental incidents are shown in Table 16.1. The vast majority of these involved the deaths of aquatic vertebrates and fish, frequently because of contamination of water courses with sheep dip formulations. The ingredients in these are synthetic pyrethroids (e.g. cypermethrin) and, to a lesser extent, organophosphorus compounds, notably diazinon. The remaining incidents involved poisoning in birds of prey, possibly deliberately. ... 

Mackness, B., Durrington, P.N., Povey, A., et al, 2003. Paraoxonase and susceptibility to organophosphorus poisoning in farmers dipping sheep. Pharmacogenetics 13, 81-88. 

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