5 April 1996

Nematodirus – high risk

YOUNG lambs will be exposed to a high risk of nematodirus larvae infection at grass this year due to the late spring.

Symptoms are violent scouring. It can be fatal unless treated quickly. Any of the main anthelminitic groups are suitable.

As a general rule late March born lambs need treating in early May, with a second treatment a month later. April-born lambs should be treated late May and again at the end of June.

When the ambient temperature averages 10C (50F) nematodirus larvae hatch out. This season the event will coincide with many young lambs weaning themselves onto a predominantly grass-based diet. Outbreaks will occur in lambs over six-weeks-old.

which producers now consider to be free of coccidiosis infections," says Keith Hunt of the Central Veterinary Laboratory.

Any emergency anthelminitic treatment will pre-empt the farms worming routine which usually kicks off mid-May. This should not be adjusted in the light of earlier treatments.

Peak infestations will be late April/early May in the north-east; later in Scotland, but late March in the south.