Sheep farmers told to be on guard for nematodirus

Sheep farmers are being urged to be vigilant against nematodirus following the warm, wet winter.

The lack of cold, frosty weather over the past couple of months means the nematodirus parasite is likely to have survived better than normal on pasture, the National Animal Disease Information Service (Nadis) warns.

Unlike other parasites that are transferred from adult sheep to lamb, nematodirus is passed to lambs from the previous year’s crop via pasture.

See also: Top 5 tips to tackle coccidiosis this lambing season

Lambs become infected by ingesting large numbers of infective larvae.

It causes severe diarrhoea, which leads to dehydration and in some cases death.

Veterinary drug manufacturer Bimeda has warned if the “unpredictable temperature fluctuations” continue farmers could be caught off guard by nematodirus.

“The risk is possibly greater this year, due to the unpredictable weather patterns we have been experiencing,” says Rachel Mallet, professional services vet at Bimeda.

“An initially mild January, was followed by sudden Arctic blasts, with a return to double digit figures only days later, and if these sudden and unpredictable temperature fluctuations continue the appearance of nematodirus may surprise farmers and leave their lambs vulnerable.”

Risk factors?

Lambs grazing pasture that carried lambs the previous spring are at greatest risk of infection.

The mass hatching of parasites that survive the winter on pasture begins with the sudden change from cold winter frost to warmer spring weather.

See also: Farmers warned about nematodirus drench resistance

This can be particularly devastating if it coincides with lambs beginning to eat grass at between six and 12 weeks of age.

Groups where coccidiosis is likely to be an issue and lambs under other stresses, such as triplets, fostered, or young or older ewes, are also at greater risk.

What actions can you take?

Where possible, avoid grazing lambs on the same pasture on consecutive years.

“Winter is a good time to review your parasite control plan for the next grazing season, especially for those flocks and herds with large areas of permanent pasture grazing,” says vet Peers Davies, who gave the advice during a Nadis online seminar.

“Integrating your grazing management and treatment plans for cattle and sheep on holding can reduce the need for treatment for both roundworms and also liver fluke parasites and allow stock to perform better if this is done well”
Peers Davies, vet

“For example, using safe grazing after lambing pastures which were grazed last year by cattle or reseeded pastures will avoid the risk of nematodirus in young lambs.

See also: Scotland exposed to ‘very high’ liver fluke risk

“And in midsummer, silage aftermath can be utilised to reduce the reliance on anthelmintics to control internal parasites in weaned lambs in conjunction with faecal egg counting.

“Integrating your grazing management and treatment plans for cattle and sheep on holding can reduce the need for treatment for both roundworms and also liver fluke parasites and allow stock to perform better if this is done well,” he adds.

Worst case, treatment with an appropriate white drench is highly effective with nematodirus.