PA066/A/14 Nematodirus warning for sheep farmers

24 April 2014
Sheep farmers must be vigilant, and on the lookout for infection. The milder temperatures through March and April have been welcomed. However, it brings along with it a higher risk of Nematodirus infection.  As cold spells followed by warmer weather creates ideal conditions for the parasite.
The Agri-Food and Biosciences Institute (AFBI) Veterinary Sciences Division have advised that hatching of Nematodirus eggs has already commenced and current meteorological readings indicate that peak hatching took place during the last week of March and first week of April. Lambs are most at risk from infection from six weeks of age which coincides with consuming significant amounts of grass until around 12 weeks when they tend to develop resistance. Clinical signs normally appear two weeks after ingestion of large numbers of larvae, be on the lookout for lambs with watery yellow-green scour or ill thrift.
Farmers need to anticipate the risk of infection as the parasite acts quickly and mortality is high. The following factors need to be considered
  • Sudden cold weather followed by a period of warm weather
  • Lambs old enough to be eating significant amounts of grass normally six weeks and older
  • Lambs grazing pasture that was grazed by lambs last spring
  • Heavy stocking density
  • Lambs under stress such as twins or triplets who may be consuming more grass, or suckling ewes with less milk, these lambs may be at risk from a younger age.
If farmers feel their lambs are at risk they should consult their vet or local CAFRE Beef and Sheep advisor about the various treatment options available. SCOPS advise farmers to use a white (1-BZ) drench. These are highly effective against this parasite and suitable for young lambs. It may be necessary to treat lambs more than once depending on the spread of ages in a group and subsequent weather conditions.
Faecal egg counts (FEC) are a useful way to establish if there is a worm burden throughout the season. However, it is important to note that low counts are not always reliable at this stage when checking for nematodirus infection, as it is the immature larvae which cause the damage and these are not yet producing eggs. At this time of the year, observe lambs closely and treat those that are at risk of infection.

Notes to Editors:

  1. Photo caption: Ewes and lambs from the KTT flock grazing at the Abbey Farm, Greenmount.
  2. All media enquiries to DARD Press Office, or tel: 028 9052 4619.