Sheep farmers should keep an eye out for signs of nematodirus and coccidiosis over the coming weeks, as tight grazing will make lambs more susceptible to infection, says vet Matt Colston, Frame Swift and Partners, Penrith.
“The first 2-3 weeks of April are a potential risk for nematodirus infection, with earlier infection possible in the south of the country.”
Nematodirus eggs are likely to hatch when a cold spell is followed by a period of warm weather. “Nematodirus infection is a big risk for 3-4-week-old lambs – grazing lambs can easily consume large quantities when eggs hatch all together on highly contaminated pastures.”
And often, the only obvious sign of infection will be sudden death. “Death may be the first think you see – when any lamb dies or lambs are scouring, it is essential to test these individuals to identify the cause of infection.”
Because there is no recorded resistance to nematodirus, infection can be easily treated with a white drench. However, timing of treatment is crucial, explains Mr Colston.
“These treatments do not have persistent activity, so it is important to drench lambs as soon as eggs begin to hatch – speak to your adviser to discuss when the best time for treatment is on your farm.”
And because grass is short, lambs are grazing tighter, meaning coccidiosis could be more of a problem this season, he says.
“Farmers are relying on supplementary feeding at grass, increasing contamination around the feeders and the likelihood of infection.”
Deciding to dose for coccidiosis will depend on individual systems and identified risk, says independent sheep vet Paul Roger.
“Preventative dosing of lambs aged between four and six weeks may be relevant on some farms but, when treating, it is essential to diagnose the cause of the problem before.”
Scouring could be a sign of coccidiosis and/or nematadirus so it is important to make a diagnosis and treat accordingly, agrees Mr Colston.
And reduced grass growth could mean ewes are experiencing extended post-lambing stress, he says. “When ewes are not receiving enough supplementary feed at grass, protein levels may not be sufficient and immunity could be compromised, increasing the likelihood of spreading eggs at pasture.”
But any treatment should be administered as part of a flock anthelmintic strategy. “Ad hoc worming is a waste of money and potentially dangerous in terms of increased resistance to wormers – any treatment must be part of a farm-specific flock health plan.”
Farmers should implement targeted dosing of narrow-spectrum drugs for nematodirus, Mr Roger continues.
“To treat successfully, you want to implement a strategy that will not increase the rate of anthelmintic resistance and target specific, problematic worms.
“This is where taking faecal samples is essential – not only to look at egg counts, but also to identify species.”
And this will vary year on year, depending on a number of factors. “Depending on stocking rates and weather, for example, the emphasis of different worm burdens will vary, which is why any regime must be specific for individual farms and individual years,” he says.
This further heightens the importance of quarantining any animals which have been away from the farm. “All these animals should be dosed sequentially with two wormer drugs with the least resistance spectrum. They should then be held for 48 hours before they are put onto ‘dirty’ pasture.”
For an indication of nematodirus risk in your area, look at the parasite forecast at www.nadis.org.uk