A CLEARER understanding of the life cycle of liver fluke combined with knowledge of how the active ingredient in flukicide treatments affects the liver fluke, could dramatically cut sheep illness or losses due to the pathogenic parasite.

A recent survey undertaken by animal health specialists Elanco, in conjunction with the Moredun Research Institute, highlighted that while many sheep farmers regularly treat for fluke, only a small percentage of the 220 questioned in the UK and Republic of Ireland recognised all seven stages in the parasite's life cycle.

And while it was promising that 63% of farmers rotate their flukicide year on year, only 8% chose the active ingredient suitable to the time of year and stage of fluke.

While many producers may not suspect a liver fluke problem in their flock until they witness symptoms such as a drop in liveweight gain, reduced ewe scanning rates or, ultimately, fatalities, they will be too late in treating the problem as the fluke has already made its way into the infected animal's liver.

Instead, actions need to be taken from the beginning of the year to determine whether there is actually a problem on the farm as, according to the survey, while 70% of those questioned recognised that the autmumn/winter season is when they can expect the greatest impact on the flock's health, some 72% did not was to start targeting treatment dates earlier in the season to prevent the infection of the mud snail host.

Farmers should be testing for liver fluke - via faecal egg counts or blood tests - in order to determine whether there is a problem or not.

Ruth Zodaks, professor of molecular epidemiology at Moredun, pointed out: "If a farmer tests 10 sheep and discovers there's no infection, this is far more cost effective than treating 200+ sheep. The correct diagnostic is also key depending on the time of year and life stage of the fluke, as if you treat adult sheep in the spring time, it will prevent the fluke affecting the offspring in the autumn."

The survey also highlighted that 56% of those questioned had liver fluke in their flock in the last five years, but 81% admitted not testing, which means many of those who said that hadn't experienced liver fluke likely had.

What is promising, however, is the fact that 63% of producers actively rotated their flukicide annually, but a disappointing 8% of these only choose by the active ingredient and stage of fluke.

Eugene Smyth, Elanco ruminant marketing manager, said: "Changing the active ingredient throughout the year depending on the season is important to avoid overuse and, potentially, resistance. We need to be careful how we proceed as there are current no new active ingredients coming on to the market so we need to look after the ones we've got and avoid overuse and resistance."

He said that during autumn and early winter, all stages of fluke are present and so triclabendazole of closantel are the active ingredients of choice, whereas in the spring when the number of immature larvae on pastures is declining, either closantel or albendazole should be used. In late spring/summer albendazole should be used to hit adult flukes to reduce eggs reaching the pasture.