12 March 1999

Lice infections on the increase

CHEWING lice infections in sheep are becoming more common since compulsory dipping regulations were lifted.

Peter Bates, parasitologist at VLA Weybridge, Surrey, says this is due to lack of dipping and the fact that some endectocides and pour-ons used to control scab do not kill lice. "Many producers are unaware of this and fail to ask a vet to diagnose the condition because of cost.

"But having a vet diagnose the condition correctly will actually save money by avoiding wrong treatments."

New groundwater disposal regulations are likely to cut the popularity of plunge dipping further, perhaps leading to more lice problems, he says.

Dipping with an organophosphate or pytheroid dip will kill both scab and lice, but where dipping is not possible do not rely on injectibles to control the parasite.

In Australia, which has a louse problem, lice are controlled by treating after shearing. "Removing wool will kill 90% of lice and then applying an insecticide pour-on will help kill the remaining few."

But the present lack of control over supply of endectocides is causing concern for some vets. In a letter to Vet Record, Mar 6, vet John Dennis, Kington, Herefordshire, calls for greater veterinary control over supply.

Mr Dennis says it appears that merchants are happy to supply products without any confirmation as to the diagnosis. On several occasions spot-on products for sheep with lice have wrongly been used to treat sheep suffering from scab and vice versa, he says. &#42