Farmers warned of potential worm explosion in lambs as rainfall arrives
22nd June 2023
Sheep farmers are advised to be on high alert for a spike in the worm burden of lambs as recent wet weather is expected to cause a dramatic rise in the number of worm larvae on pastures.
Independent sheep vet Fiona Lovatt said the risk is usually greatest a week or two following rain after a dry spell, with current warm and wet conditions creating the perfect environment for worms to emerge.
“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,” she explained.
“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 lifecycle.”
Farmers should also be aware that there might be a slight delay to the increased worm burden showing up on Feacal Egg Counts (FECs), and close monitoring is advised to get an accurate picture.
“The challenge can happen so suddenly there isn’t always time for farmers to see a rise in faecal egg counts before there’s a clinical problem, especially if they took a count just as the rain arrived,” Ms Lovatt said. “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. “Generally, I like farmers to be both monitoring growth rates and taking general condition into account alongside relying on FEC tests.”
Low worm egg counts are currently being reported on most of the farms in dry regions involved in the Zoetis Parasite Watch Scheme, which comprises a network of 26 farms spread across the UK. Worm and fluke counts are being conducted every couple of weeks throughout the risk period, with results uploaded in real-time.
However, Zoetis Vet Patricia van Veen expects the current situation will change suddenly.
“As Fiona explained, worm egg counts are expected to rise quite dramatically over the next fortnight, especially on farms where high FECs were seen earlier in the year,” she noted.
“The sudden change in weather will also provide optimum conditions for flies and maggots. You should speak with your health care professional now about the most appropriate parasite control for both worms and flies,” she advised.
To keep up to date with the latest parasite data in your area, consult the Parasite Watch forecast at www.parasitewatch.co.uk
