Liver fluke a real cause for concern for farmers.
Scops - the Sustainable Control of Parasites in Sheep organisation made up of industry groups - said the condition is causing havoc in parts of the UK.
Reports suggest a tenfold increase in the number of cases of acute fasciolosis in the last quarter of 2012 compared with 2011 and a fourfold increase in the number of cases of chronic disease.
There were 69 new cases of acute fluke diagnosed in October to December 2012 compared to seven over the same period the previous year, the Animal Health and Veterinary Laboratories Agency (AHVLA) said.
There were also 73 incidents of chronic fluke diagnosed in sheep in the same time period in 2012 compared to 19 in 2011. The AHVLA data is backed by reports from vets, who have found a growing number of fasciolosis cases at postmortem examinations.
Only a spell cold weather - minus 18 degrees centigrade for several days - will kill off the fluke metacercarieae parasites and this has not been forecast.
Lesley Stubbings of Scops said: "If sheep have suffered any liver damage they will also need good quality feed, to maintain body condition up to lambing."
She advised farmers to monitor flocks for signs of the disease and treat with an appropriate flukicide.