Sheep farmers must be on guard against nematodirus now the weather has warmed up to avoid devastating losses, warns independent sheep specialist Lesley Stubbings.
“Such a sudden change from cold days and frosty nights is when nematodirus is at its most dangerous, with a mass hatch of over-wintered parasites forecast.”
Ms Stubbings, who is a member of the Sustainable Control of Parasites in Sheep Group (SCOPS), is urging farmers to consider the risk factors and consult their vet or adviser with regard to local risks and treat lambs at risk.
“Because this disease strikes so quickly, we can’t afford to have a ‘wait and see’ policy with nematodirus.
“The damage is done by large numbers of immature larvae that are not producing eggs, so faecal egg counts are also not reliable,” she says.
“Cold weather delays hatching, so when we get a sudden change in temperature, like this year, it can trigger a mass hatch. When this coincides with the time when lambs are starting to take in significant amounts of grass (more than about six weeks old), the result can be devastating.”
The main difference in the life-cycle of nematodirus compared with other parasitic worms, is that development to infective larvae takes place within the egg and infection passes from one lamb crop to the next year’s crop.
Ms Stubbings adds: “Cold weather delays hatching, so when we get a sudden change in temperature, like this year, it can trigger a mass hatch. When this coincides with the time when lambs are starting to take in significant amounts of grass (more than about six weeks old), the result can be devastating.”
SCOPS are asking farmers to consider the following factors and take action when they are at risk:
- A sudden, late cold snap followed by a period of warm weather
- Lambs grazing pasture that carried lambs last spring
- Lambs that are old enough to be eating significant amounts of grass (generally 6-12 weeks old, but this year may be younger with ewes struggling to milk)
- Groups where there is likely to be a challenge from coccidiosis
- Lambs that are under other stresses such as triplets, fostered, on young or older ewes.
When farmers believe their sheep are at risk SCOPS advises farmers to use a white (1-BZ) drench.
“These are highly effective against this parasite and suitable for young lambs, says Ms Stubbings.
“However, it may be necessary to treat lambs more than once, depending on the spread of ages in a group and subsequent weather.”
Forecasts warn of higher parasite risk