Warnings issued as faecal egg counts soar in drought areas

Farmers are being warned to test their stock after unexpectedly high worm egg counts were recorded in areas worst affected by the current drought.

The warning is based on data from 26 farms across the country which are regularly taking faecal egg count tests, as well as testing for fluke, for the Zoetis Parasite Watch Scheme.

See also: Faecal egg count trial cuts wormer use on Welsh sheep farms

Zoetis vet Ally Ward says results from the scheme show a varied picture – highlighting the need for regular testing. “The expectation would be on those farms experiencing drought to have low egg counts, but that is not what we are seeing,” she says. 

“This reinforces the need to regularly test stock every couple of weeks to help build a picture of what is happening on your farm.”

Specifically, the Sustainable Control of Parasites in Sheep (Scops) group is warning that farmers should be aware of Haemonchus contortus (Barber’s pole worm) as this species survives well in hot conditions. This worm can affect both ewes and lambs and feeds on blood, so clinical signs include anaemia and bottle jaw.

High counts in Devon

Among those with flocks suffering higher worm egg counts is Devon farmer Peter Baber, who lambs 900 Exlana, Suffolk, SufTex and Texel ewes. He takes faecal egg counts from each group every two weeks and conducts tests 10-14 days post-drenching to check if the product has worked.  

His farm near Exeter, which is all permanent pasture, is being hit hard by the drought, with early-born April lambs weaned prematurely at the beginning of July, enabling grass to be prioritised for the lambs. As a result, ewes are now being fed on a full winter ration.  

When he last tested his lambs, on 30 July, the results revealed 2,240 worm eggs per gram (EPG) of faeces – despite the ground being “burnt to a cinder”. The suggested threshold for treatment is 250 EPG and above.

He believes worms eggs must have been building over time, with lambs drenched six weeks previously due to high counts.

‘Quite a shock’

Mr Baber says: “It was quite a shock to see such high worm egg counts. Lambs are performing relatively well, considering the lack of grazing, and we’ve had no signs of scouring. However, with such a high burden, we expect there has been some production loss.” 

He assumes he has not seen symptoms in his lambs because of their breeding. He has been performance-recording and selecting his replacement stock for 30 years.  

“We think our sheep have developed a level of worm resilience, so they can now perform with such a high burden,” he explains.  

Treatment plan

Lambs on the farm have since been drenched and he will continue monitoring stock, expecting that worm egg counts may rise again, with increased challenges, when wet weather arrives.  

“Treating lambs now will hopefully reduce the worm egg output in the next few weeks and maximise performance on the limited grazing currently available,” he says.

His advice to other farmers is to test regularly, as diagnosis by eye is impossible. Ideally, growth rates should be measured as well as faecal egg counts. There is an added complication as some species of worm are more pathogenic than others, so they can have different impacts on lamb performance.