Nematodirus - The Accidental Smallholder

Nematodirus are parasitic worms that cause nematodirosis in lambs (and sometimes calves). The species usually associated with this is N, battus. Since the worm eggs can survive overwinter, and the development of the eggs is triggered by cold and moisture, the lifecycle can be broken by not using the same lambing ground in successive seasons.

Heavy infection generally results in watery yellowy-green diarrohea, although this can also be associated with other bacterial / viral / protozoal (coccidian) infections. The diarrhoea can result in severe dehydration and even death.

Other symptoms include dull, rough fleece and a “tucked-up” appearance. Infection can be identified by faecal sampling but onset can be so rapid that fatalities occur before eggs appear in the faeces.

Less heavy infestations can manifest themselves as “ill-thrift” or “poor doers”. The highest risk of disease occurs in the spring in young lambs (4-8 weeks old), although outbreaks of the disease have been seen in older lambs later during the grazing season.

Risk of disease forecasts can be found at the National Animal Disease Information Service.

If you think you have a problem with nematodirosis on your smallholding, discuss it with your vet who will be able to advise on control measures.