Sheep farmers are being urged to monitor Nematodirus risks on their farm with hatching expected to start.

Warm spring-like weather has finally arrived and will bring with it a mass hatch of the infective larval stage of Nematodirus. These will have overwintered on pastures waiting for temperatures to regularly exceed 10oC.

Nematodirus is the most commonly diagnosed disease in growing lambs in May, according to the Animal and Plant Health Agency (APHA).

Farmers involved in the Parasite Watch scheme, run by Zoetis, expect to start picking up egg counts in the next couple of weeks, with results reported in almost real-time at www.parasitewatch.co.uk.

Here, the 18 farms involved in the scheme, have faecal samples taken every two weeks to detect major stomach worms and Nematodirus. Information is then uploaded within hours of the test result coming back, giving a real-time picture as to what is happening on the ground.

Symptoms and risks

Nematodirus can strike very quickly in lambs under three-months-old that don’t have immunity to the parasite, with the sudden onset of diarrhoea. They will also often appear dull and depressed, will stop 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 markets weights.

Risk factors include:

• Lambs grazing pasture that carried lambs last spring

• Lambs younger than three-months old that don’t have immunity to the parasite, but are consuming grass (generally, 6-12 weeks of age)

• A sudden cold snap followed by a period of warm weather

• Lambs under other stresses such as triplets, fostered, on young or older ewes.

Treatment

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.

“If you’ve got a mixed infestation, then you need to be confident the drug you are using will treat against both Nematodirus and stomach worms.

“Traditionally, if farmers have Nematodirus they will treat using a white wormer; which is fine, as long as there’s not a mixed worm burden.

“If you’ve got a mixed worm burden and you use a white wormer, which you may have resistance to, it is a dangerous situation,” he warns.

“When a wormer is only 60-90% effective you won’t see any visual resistance issues in your lambs, but you won’t be maximising their growth potential. You will also be allowing resistance to build up on your farm.”

He adds: “You need to find out what worms are on your farm and what drugs are working on your farm and what are not in order to protect the farm for future generations,” he says.

How to use Parasite Watch

The aim of Parasite Watch is to show what is happening across the UK using an interactive map found at www.parasitewatch.co.uk. Parasite data from each of the farms will be updated regularly, which will allow farmers to see if there are spikes in certain parasites throughout the year in their area and enable them to take appropriate action.

To use the map, click on a farm in your area and details of any parasites that have been found as well as when they were detected will be displayed. Test results will be online within hours of the test being taken.