Managing Nematodirus Battus

APRIL is the month farmers must be conscious of an outbreak of Nematodirus Battus in their flocks.

The Department of Agriculture normally gives advice to farmers in relation to the predicted risk of infection in lambs, so watch out for the Nematodirus forecast and dose lambs approximately two weeks out from forecast dates.

Nematodirus worms affect lambs aged five to 12 weeks of age who become infected through ingesting large numbers of infective larvae present on contaminated grass.

There is a mass hatching of larvae in springtime when soil temperatures increase after a period of cold weather. Lambs will begin to show clinical signs of infection two or three weeks from the date of peak hatching.

The date of peak hatching will vary depending on what part of the country you are located in, due to land type and weather.

Symptoms of Nematodirus include diarrhoea, wasting, dehydration and in severe cases mortality. Where an outbreak occurs, lambs can be seen congregating around water troughs as they develop a thirst, while ewes continue to graze.

Flocks, where lambs are already grazing pastures grazed by last year’s lambs, are at most risk of infection.

So as a prevention method, keep the current year’s lambs off pastures that were grazed by lambs and young calves the previous year.

Twin lambs or single lambs born to a ewe of poor milking ability may be at a greater risk of developing Nematodirus as they consume greater amounts of grass earlier in life.

In the west of Ireland, lambs should be dosed with a suitable wormer by the second week of

April, while lambs in the rest of the country should be dosed in the third week of April, but again watch the Department of Agriculture forecast for Nematodirus and seek advice before treatment.

White drenches (Benzidimidazoles) are the recommended treatment for Nematodirus infections as these drenches are effective against both larval and adult stages.

As reinfection can occur, lambs may require repeated treatment at two-to-three-week intervals. Lambs will get immunity to Nematodirus once they have come in contact with it, and generally it will not affect their performance in mid-summer.

It is important to know the symptoms of Coccidiosis in lambs as the symptoms are very similar to Nematodirus.

Coccidiosis can be suspected if scouring is still occurring after dosing for Nematodirus. If you have a difficulty in diagnosing or deciding on treatment, it is important to consult your veterinary surgeon as they will provide a correct diagnosis and give recommendations on the best products to treat for both Nematodirus and Coccidiosis.

To help prevent both Nematodirus and Coccidiosis in young lambs, use a rotational grazing system, and frequent movement of feeding and water troughs to drier areas should be carried out as localised poaching creates moist conditions suitable for the spread of parasites. Aim to keep young lambs off heavily contaminated pastures.