AFBI issues Nematodirus Warning – Spring 2011
The Agri-Food and Biosciences Institute (AFBI) Veterinary Sciences Division wishes to advise sheep farmers of the likely risk of Nematodirus worm infection in young lambs this spring.
Nematodirus infection results from the ingestion of large numbers of infective worm larvae present on contaminated pasture. Lambs grazing the same pasture last year are the source of this contamination. Nematodirus eggs passed out by these lambs have a tendency to undergo mass hatching in the spring, under suitable conditions of moisture and temperature, resulting in an annual high risk period for lambs. Affected lambs develop profuse scour and can die rapidly.
Young lambs can be at risk from Nematodirus worm infection
Hatching of Nematodirus eggs has already commenced and current meteorological readings indicate that peak hatching will take place in early-April.
Nematodirus normally only affects lambs between 6 and 12 weeks of age and clinical signs usually appear two weeks after ingestion of large numbers of larvae. Although rare, Nematodirus infection can occasionally cause problems in young calves. Therefore, farmers should be on the alert for signs of scour in lambs (and possibly young calves) from mid-April into May.
Farmers should be aware that Nematodirus infection can be confused with coccidiosis, another disease which can cause severe scour in young lambs. As the treatment for each of these conditions is different, accurate diagnosis and treatment, through your veterinary surgeon, is essential.
Nematodirus disease can be avoided or reduced in lambs by:
not grazing lambs on the same fields as those grazed by lambs of a similar age last year.
using anthelmintic drenches every 2 to 4 weeks. The interval between doses depends on both the particular anthelmintic used and the severity of infection. To date, limited evidence has been found of drug resistance in Nematodirus to any of the available classes of anthelmintic.
Your veterinary surgeon should be consulted at an early stage. He or she is in an ideal position to provide advice on the prevention and /or treatment strategy best suited to your particular circumstances. AFBI’s Veterinary Sciences Division can test faeces samples from sheep or cattle to determine the level of worm eggs present.
A minimum of 5 grams of faeces from each animal is required for this test.
Hillary Edgar and Bob Hanna
Agri-Food and Biosciences Institute