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Spring 2007 - Parasitic Disease Forecast

Nematodirosis in lambs:

Nematodirosis is a severe disease of 6-12 week old lambs, which can become infected through ingesting large numbers of infected larvae present on contaminated pasture. Infection is characterised by profuse diarrhoea and wasting. Mortalities in untreated lambs can be high. Nematodirus larvae invade the intestinal mucosa and in some cases death may occur before signs of diarrhoea are observed. This disease is best prevented by keeping the current year's lambs off pasture that was grazed by lambs last year.

Meteorological information and soil temperature data for March indicate that in south, southwest, west and northwest coastal areas, pasture contamination with infective larvae has already occurred. Further inland and in the east it is estimated that peak hatching of eggs occurred during the period April 1st to April 9th. However, in all these areas hatching in pastures on high ground will be delayed by a few days.

The mild winter may have reduced the synchronisation of the egg hatch and in some areas hatching may have occurred earlier and may continue for a longer period than normal. Therefore, farmers should err on the side of caution, especially those with intensive sheep units where safe pasture is not available and on farms where the nutritional status of the ewe is less than optimal. Lambs should be dosed with a suitable anthelmintic in late April or early May to decrease the likelihood of clinical problems later in the season and also to lower pasture contamination for the next year.

Coccidiosis in lambs:

It is also important that farmers are aware that other parasites cause diarrhoea in young lambs and require different control measures and medication. Nematodirus can be confused with coccidiosis, which can also cause severe scour in lambs. Rotation of pasture and frequent movement of feeding troughs and watering points help prevent coccidiosis in young lambs as localised poaching creates moist conditions suitable for the spread of this parasite.

It is advisable to consult a private veterinary practitioner for an accurate diagnosis and advice on appropriate medication if lambs with severe diarrhoea and straining are observed. Faecal samples can be submitted to the Central and Regional Veterinary Laboratories for testing. This service is available through veterinary practitioners and can be used to assess the level of parasite infection on farms and also to assist in the development of parasite control programmes.

12 April, 2007


This press release is prepared in conjunction with the Nematodirus Advisory Group. This group comprises representatives from the Department of Agriculture and Food; Agri-Food and Biosciences Institute, Northern Ireland; Teagasc; Met Eireann; University College Dublin and the pharmaceutical industry.

Date Released: 12 April 2007