Nematodirosis update

APHA have diagnosed 2 cases of Nematodirosis from different regions of the UK, and we expect cases to rise as we see more warm weather. Susan Carr, BSC BVetMed MRCVS, part of the team at Severn Edge explains more:

High Risk Factors for Nematodirus Battus: 
If any of the following apply your lambs will be at greater risk of nematodirus and you must be more vigilant:
•    Lambs grazing pasture that carried lambs the previous spring
•    A sudden, late cold snap which is followed by a period of warm weather
•    Lambs that are old enough to be eating significant amounts of grass (6–12 weeks old)
•    Groups where there is also likely to be a challenge from Coccidiosis
•    Lambs that are under other stresses e.g. triplets, fostered, on young or older ewes

“Nematodirus battus is a roundworm that causes severe disease in young lambs, with high levels of mortality and a severe check in growth rates. The infective larvae develop inside the eggs left on the pasture by last year’s lamb crop, which are then present to infect the following years flock. Hatching of these larvae requires a period of cold weather followed by temperatures of 100C and above. South-facing pastures will see an earlier hatch and 100m rise in altitude will delay the hatch by around a week. 

To be at risk of infection lambs need to be grazing significantly, around 6 weeks of age onwards. The worms cause most of their damage as immature larvae so waiting for a rise in faecal egg count number or clinical signs can be too late. It is best to act quickly and ideally move lambs to clean pasture, or pasture that has just been grazed by adult animals. If this is not possible then treating with a white (BZ) drench may be indicated. Resistance to white wormers is fairly widespread in the UK but they are generally still effective against Nematodirus.”

Thankfully treatment with an appropriate white drench is highly effective and is endorsed by SCOPS, who comment in their 'Nematodirus in Lambs' literature; 'If farmers feel their lambs are at risk and they need to treat for Nematodirus, then SCOPS advises farmers to use a white (1-BZ) drench.' These are normally highly effective against this parasite and suitable for young lambs. This includes 2.5% albendazole, which is highly effective, relatively inexpensive and appropriate for lambs.
It is extremely important to dose for the correct weight of lamb to ensure we do not select for resistance. A FWEC is recommended 7-10 days after anthelmintic drenching to ensure that the treatment has been effective. It must be noted that severely affected lambs may require multiple treatments which you vet will be able to advise you on. Usually, for lambs born from the second week of March onwards, treatments are given 3 weeks apart in May. In greater risk years, three anthelmintic treatments are given extending the drenching period into June. Remember this can vary from year to year depending on the weather so please speak to us for further advice. 

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