Nematodirus threat forecast to be 'extremely variable' this year

Animal health experts are predicting that the threat to lambs from nematodirus will be extremely variable across the UK in 2024.

A sudden increase in temperature after a period of cold weather can trigger a mass hatch of Nematodirus battus worms, from eggs that have laid dormant since the previous season.

If this coincides with the time when lambs are starting to take in significant amount of grass, the result can be devastating, the Sustainable Control of Parasites in Sheep (SCOPS) warns.

Experts at the group are urging farmers to use the Nematodirus Forecast tool, as it will be important to help prevent flocks being caught out, as well as checking the pattern of temperatures to decide if lambs are at risk.

Lesley Stubbings, independent sheep consultant and SCOPS spokesperson, says: "Producers cannot afford to have a ‘wait and see’ policy, nor one that simply assumes the danger period will be the same every year.

“Nematodirosis is caused by large numbers of immature larvae that lambs take in off pasture. These immature larvae are not producing eggs, so this is the one time of year when faecal egg counts (FECs) aren’t as useful.

"Instead, producers need to keep an eye on the forecast – which is a free, online resource – and consider their individual risk factors.”

The Nematodirus Forecast is updated daily using data from 140 weather stations around the UK, with colour-coded dots providing a guide to the risk level in any given area.

Ms Stubbings explains: "Find the dot that is nearest to you or most representative of your farm. The height above sea level of each weather station is provided, as every 100m increase in altitude delays hatching by about seven days.

"If your nearest station is at 200m above sea level but your farm is at 100m, for example, hatching could be around seven days earlier than the forecast. South-facing fields also tend to have an earlier hatch.”

Although FECs are not useful for monitoring the nematodirus risk level, experts at SCOPS are still urging farmers to use them.

They will help monitor other roundworm species and, if they identify nematodirus eggs, this can indicate what the level of contamination is going onto a pasture.