"Frightening" levels of liver fluke infection in sheep in Scotland could be just the "tip of the iceberg", according to vets from Scotland’s Rural College.

Infection by the fluke parasites causes ill health, decreased fertility, lower productivity and even death. With wet weather causing a dramatic rise in reported cases this year, farmers and crofters are urged to act now to ensure the safety of their flock.

Between October and December last year there were over 200 cases of liver fluke recorded by SAC Consulting, Veterinary Services provided by SRUC. In the same period in 2011 there were just 57 cases. Brian Hosie, Veterinary services Group Manager believes many more cases were dealt with by farmers who did not bother to report them.

He said on Wednesday, "These cases are probably only the tip of the iceberg. This massive increase in liver fluke is a consequence of the wet summer and mild winters we have had in recent years. It is impacting on the viability of many sheep farms through reduced productivity and high death rates in flocks."

The liver fluke parasites attack the liver of many mammals but mostly affect sheep and, to a lesser extent, cattle. Eggs from infected stock fall onto pasture and once hatched find a mud snail in which to live and multiply. On leaving the snails they climb onto grass, are eaten by livestock, migrate to the liver and cause tissue damage. Acute cases can kill, while even milder cases can adversely affect condition and fertility. The parasite also makes infection by other conditions, like Blacks Disease, more likely.

The extremely wet Scottish weather of the last two years has provided ideal conditions for fluke larvae to spread and the mud snails (Galba) to flourish and multiply.

Brian Hosie urged farmers to act quickly to firstly diagnose and then treat any cases of liver fluke. He said "Failure to take action in the next few weeks could result in serious losses at lambing time through weak ewes dying or having insufficient colostrum to feed their lambs. These lambs may die of starvation or from diseases such as joint ill or severe diarrhoea."

Already early pregnancy scans have detected significant numbers of barren ewes, without lambs, something that could be linked to the rise in fluke infections. SRUC Sheep Specialist John Vipond warned farmers to look out for signs that ewes are unfit, which could indicate infection. Sheep may have a poor quality fleece, break back when walked up a hill, or not come forward for feeding.

Dr Vipond also suggested farmers take preventative measures like fencing off particularly wet areas which will host more snails, improving field drainage or moving flocks to drier fields, where possible.

Another worry for sheep farmers is the reported resistance to medicines that some animals seem to be developing. However, specialist Vet, Heather Stevenson argued drug resistance may not be to blame. She said, "It is rarely as straightforward as that. Ask whether this is right dose for the size of sheep or is the wrong product for adult fluke. It is actually worth doing a post treatment test on between six and ten sheep to check for fluke eggs. Also autumn conditions often meant that sheep were re-infected almost as soon as they had been treated."

While many farmers and crofters are very worried about their stock, and the SRUC experts emphasized that the statistics must boost preparedness and awareness of the danger posed by fluke, they offered assurance that most animals will recover completely after treatment. However they will need some extra care and attention, such as an earlier move indoors and good nutrition.