Moredun warns of Nematodirus risk in young lambs

Scientists from the Moredun  are warning sheep farmers to be alert to scouring in young lambs due to Nematodirus and have produced a free guide for farmers to help better understand, control and prevent this problem.

Nematodirus parasites live in the intestine of sheep and infection can lead to profuse watery yellow-green scouring and ill thrift. The concern is that the performance of young lambs that receive an early season check in growth due to nematodirosis may be compromised for the rest of the grazing season and lambs will take longer to reach market weight as result.

Parasitologist and co-authro of the Nematodirus guide Dr David Bartley warned, “Nematodirus can be a major threat to productivity and survival in young lambs. Most losses in the UK occur in the spring when lambs start to graze pastures contaminated with parasite larvae”. He added, “Once temperatures begin to rise in the spring like we have seen in the last week or so, Nematodirus eggs deposited on the pasture from last year’s lambs will hatch into infectious larvae en mass, posing a significant risk to this season’s lambs.”

Nematodirus parasites have a simple lifecycle; eggs pass out of the host in faeces, develop to infective larvae within the egg, and hatch onto pasture. Nematodirus eggs deposited during one spring/summer will develop to infective larvae within a few weeks, but generally don’t hatch until the following spring, when temperatures are greater than 10°C after a cold spell. Larvae are then ingested by lambs with pasture, travel to the small intestine, develop into adults and lay eggs which are then pass out in the faeces to complete the life cycle.

Dr Bartley from Moredun stressed the importance of farmers getting a clear diagnosis of Nematodirus. He commented, “This disease is commonly diagnosed on the basis of large numbers of Nematodirus eggs in faeces – these faecal sample tests are relatively inexpensive and can be carried out either by your own vet or a suitably trained SQP.” Strategic treatment with an appropriate (and effective) anthelmintic is then key. He added “Until recently there had been no reports of anthelmintic resistance in UK Nematodirus populations; however anecdotal evidence suggests there is a possibility that white drench resistance may arise. Under these circumstances farmers using white drenches should, ideally, perform a drench check to confirm that their treatments have been effective.”

Moredun suggest that, in high risk seasons, a total of three treatments with an effective anthelmintic given three weeks apart should suffice to control disease. The timing of the first dose depends on the prevailing temperatures and will vary seasonally but would generally be given sometime in early to mid May. On farms with a reduced risk of nematodirosis, only two treatments may be necessary. Recently nematodirosis has been recorded in older lambs later in the grazing season. The reasons for this remain unclear and as no two farms are the same, Moredun strongly recommend that farmers talk to their vet or sheep advisor and develop a specific strategic parasitic control programme for their own farm.

If you would like a free eight page guide on controlling and preventing Nematodirus please send your address details to Maggie Bennett at Moredun Tel: 0131 445 5111 or email info@moredun.org.uk