11 April 1997

STRATEGY FOR SHEEP SCAB

Sheep scab is one of the most serious welfare problems producers may encounter in their flocks and it is now widespread.

Human health concerns over the use of OP dips have seen many producers switch to using non-OP, safer alternatives, such as the synthetic pyrethroids, to control the mite. But dealing with scab using non-OPs has added to flock costs and new evidence regarding dip disposal suggests the bill could increase further. It is now apparent that pyrethroid dips such as Bayticol are 100 times more toxic to insect life in water courses than OPs.

The governments preferred method of disposing of dips to avoid pollution of watercourses is through a licensed waste disposal contractor – but this is prohibitively expensive. Neutralising dips before disposal to land would be the cheaper of the two options. Clearly, care is needed when disposing of used sheep dip, whatever its active ingredient. Stricter controls are likely to be imposed on siting and drainage of dips and dip disposal – and, from July, tougher rules will be in place to control scab. Local authorities will, for example, have power to clear open land so scab outbreaks can be treated. This is welcome news given that common grazings provide dangerous reservoirs of scab infection.

Resistance is another big threat to control of external parasites such as scab and also internal parasites. Failure to treat as instructed can lead to incomplete control of the parasite and cause resistant scab mites, or worms, to develop. It is essential, therefore, to read the makers instructions carefully before treating stock or, better still, buying the product.

This supplement reviews the products available to control both internal and external parasites of cattle, sheep and pigs. All can make a useful contribution to stock health provided they are used correctly.