Wet weather followed by a sudden increase in temperature is causing a high Nematodirus and roundworm risk on farms nationwide, according to reports from Parasite Watch.

Nematodirus has been reported on farms in the North East as well as further south. A farm in Stockton on Tees last week reported a Nematodirus count of 350 eggs per gram (epg) and a roundworm egg count of 560 epg. 250 epg is the threshold over which treatment is recommended.

Vet, Maarten Boers of the Livestock Partnership, West Sussex, says he is starting to see problems in lambs that are between four and six weeks old.

He said: “These lambs are of an age where they are really starting to consume grass.

"Apart from Easter weekend, the temperatures have been quite cool keeping worms at bay. However, now it is starting to warm up we are seeing some high worm egg counts and reports of Nematodirus. One client phoned up on Friday saying he’d lost some big lambs suddenly to Nematodirus.”

Faecal egg counts will not always highlight Nematodirus as it is the immature larvae causing the losses. Mr Boers recommends farmers only use a white drench for Nematodirus if they can be sure there are no roundworms present.

He said: “Nip Nematodirus in the bud and after that monitor worm burdens using faecal egg counts."

Nematodirus can strike very quickly in lambs under three-months-old that don’t have immunity to the parasite, starting with the sudden onset of diarrhoea. They will often appear dull and depressed stopping suckling and will lose condition.

When left untreated, death can occur rapidly due to dehydration. Those that do survive will often take two to three months longer to reach acceptable market weights.

Zoetis vet Dr Dave Armstrong says it’s important farmers not only keep an eye out for Nematodirus, but are also aware of which other worms may be challenging stock on their farm.

He said: “If you’ve got a mixed infestation, you need to be confident the treatment you are using is effective against both Nematodirus and stomach worms.”

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