Warning of dire effects on lambs of nematode worms

Nematodirus worms are the first parasites that will affect young lambs. Lambs 5 - 10 weeks of age will be affected generally in April/May.

The worm infection is carried over on grassland from the previous year and is triggered by cold weather followed by warm spell.

The Department of Agriculture, Food and the Marine have recently issued a warning in relation to the risk of infection in lambs based on the advice received from the national Nematodirus Advisory Group.

Symptoms of nematodirus include diarrhoea, wasting, dehydration and in severe cases mortality. It can be associated with lambs congregating around drinkers while ewes continue to graze.

Flocks where lambs are already grazing pastures grazed by last year’s lambs are at most risk of infection. In general these will be flocks where lambs are five to six weeks of age and older. However twin or triplet lambs are likely to be grazing from a younger age as may flocks with high stocking rates.

White drenches (benzimidazoles) are the recommended treatment. While there is resistance to white worm doses by roundworms in the later grazing season there is no resistance to nematodirus.

White doses have the advantage of being among the cheaper worm doses. There are no drenches available with residual activity against nematodirus. Because of this lambs can be re-infected again and may need further treatments at two to three week intervals.

Lambs will get immunity to nematodirus once they have come in contact with it and generally it will not be of significance to performance from mid-summer. At this point strongyle worms will be the more infective parasites and may need to be treated.

It is important to note that coccidiosis in lambs can be confused with nematodirus as the symptoms are very similar. Lambs with coccidiosis will also exhibit acute diarrhoea but this may be accompanied with a black/ bloody scour.

Coccidiosis can be suspected if scouring is still occurring after dosing for nematodirus. Coccidiosis will require different control measures and medication to nematodirus.

As with all livestock health issues consult your veterinary practitioner if in any doubt. He/ she can provide a diagnosis and advise on appropriate medication if lambs with diarrhoea are observed.

This is especially the case where there has been little or no response to an initial nematodirus treatment.

Both nematodirus and coccidiosis infections can occur at the same time in the same lambs, so treatment may need to be targeted at both pathogens.