The Agri-Food and Biosciences Institute has warned sheep farmers in Northern Ireland of elevated Nematodirus infection risk in young lambs. The parasite spreads when lambs ingest larvae from pasture contaminated by previous grazing.

AFBI stated that Nematodirus eggs require cold winter followed by warmer spring conditions to hatch. Current moisture and temperature levels triggered mass hatching. Forecasting based on climate data showed 10% of annual hatch in mid-March 2026 and peak in early April 2026.

Lambs aged 6 to 12 weeks face highest risk, with symptoms appearing two weeks after heavy larvae intake. Signs include severe diarrhea leading to quick deaths. Farmers must watch young calves too, as infection occurs rarely in them.

AFBI noted possible confusion with coccidiosis, which causes similar diarrhea but needs different treatments. Veterinary diagnosis is required for proper care.

To lower risk, farmers should avoid grazing lambs on fields used by similar-aged lambs last year. Regular anthelmintic treatments every two to four weeks help control it.

AFBI also flagged potential Haemonchus infections in growing lambs over summer. Recent mild wet weather increased cases, leaving pastures with surviving eggs and yearlings carrying dormant larvae. This parasite causes anemia and bloody diarrhea, leading to rapid flock losses.