Farmers using faecal egg count (FEC) analysis to monitor the need to treat lambs for worms are being cautioned about the possibility of a spike in worm egg counts where rain follows a prolonged period of dry weather. UK-based sheep vet Fiona Lovatt says farmers in such situations need to be in a position to act quickly.

“[The] worm risk will spike within a week after the rain. This means if you are monitoring worm egg counts on a fortnightly basis and have only just taken a count before rain arrived, don’t assume that all is OK and wait for another couple of weeks before checking again, as it could be too late then.”