Farmers “must” be on high alert for worms in their lambs according to animal health company, Zoetis.

The alert comes after a break in the weather that is expected to cause a “dramatic rise” in the risk of worm larvae on pastures.

Fiona Lovatt, independent sheep vet said the risk is usually a week or two following rain after a dry spell, with current warm and wet conditions creating perfect conditions for worms to ‘get going’.  

Worms warning

Lovatt warned sheep farmers that following rain, the risk to lambs can “rise dramatically”, but she added it may take longer for the faecal egg counts (FECs) to catch up. 

She said: “If you saw high FECs earlier in the spring, there will have been contamination. The FECs may have gone low in the dry, but the chance is high they will suddenly spike again after rain. 

“When it’s been incredibly dry, faeces remain compact when they fall and are not dispersed by rain, so the risk to lambs from worms is relatively low as the larvae are hardly able to escape onto the pasture.

“However, as soon as the rain arrives and it breaks up the faeces, it provides the perfect conditions for infective larvae to emerge from the dung and complete their life-cycle.”   

According to Lovatt, there isn’t always time for farmers to see a rise in faecal egg counts before there is a clinical problem as it can happen so suddenly, “especially if they just took a count as the rain arrived”.

The independent vet explained this is because there will be a lot of infective larvae but not yet adult worms laying eggs.

“It’s essential to be alert after rain and to take good advice, as the challenge could be sudden and devastating,” she warned.

Parasite watch

Zoetis Parasite Watch scheme has reported low worm egg counts on most of the farms in dry regions involved, although Zoetis pointed out there are regional differences.

However, it is a situation that Zoetis vet, Patricia van Veen expects will “change suddenly”. The Zoetis Parasite Watch scheme monitors worms and fluke every couple of weeks throughout the “risk period” on a network of 26 farms.

Lovatt advised that due to the sudden change in weather making it “optimum conditions” for flies and maggots, that people should speak with healthcare professionals about the most appropriate parasite control for both worms and flies.