Animal health experts are once again offering their nematodirus forecast tool to help farmers, vets and advisers identify when lambs might be at risk.
The online tool, now available to use, aims to ensure timely and effective interventions when dealing with the parasitic roundworm.
Created by the Sustainable Control of Parasites in Sheep (SCOPS) group, it particularly looks at the role of temperature on the larvae.
This year, experts at SCOPS have seen some significant fluctuations in temperatures, making the time of hatching difficult to predict without the forecast.
Currently, the map indicates there are some very high risk areas, as marked by black dots, which is earlier than in previous years.
Lambs born from mid-February onwards that are old enough to be grazing are currently at the highest risk, SCOPS says, while most March-born lambs are currently too young to be affected.
Analysis of historic forecast data from 2019 to 2024 highlights the variation in the timing of the nematodirus hatch, corresponding to temperature fluctuations.
Speaking on behalf of SCOPS, independent sheep consultant Nerys Wright says: "The forecast helps to pinpoint the timing of any treatment given.
"The range between the earliest and latest onset of very high-risk varies by six to seven weeks over a five-year period, highlighting that treatment at set times is unlikely to be effective.
"Neither can we risk a wait-and-see approach because when an outbreak occurs, as Nematodirus can rapidly cause severe harm or even death to a large number of lambs."
Nematodirus eggs already on the pasture from last year’s lambs typically require a period of cold weather followed by warmer temperatures of 10°C or more to hatch, SCOPS says.
If these conditions occur in quick succession it can trigger a mass hatch, and if this coincides with lambs beginning to consume significant amounts of grass, the group warns that the impact can be devastating.
“It's important to note that faecal egg counts (FECs) are not a reliable indicator of current risk," Dr Wright continues.
"The damage is caused by immature larvae that do not produce eggs and will not be found in samples.”
The SCOPS forecast predicts the hatching of Nematodirus battus based on local weather conditions.
The interactive map, updated daily with data from 140 weather stations provides a guide to the risk level in any area.
