Finding new strategies to tackle liver fluke

By Country News

It is estimated about six million cattle graze Australian pastures where liver fluke is endemic.

With the arrival of autumn, which brings an increased prevalence of liver fluke disease, cattle producers are encouraged to look at the best strategies to protect their livestock.

Liver fluke is a parasite, transmitted by an aquatic snail, that infects pastures near irrigation channels, dams and drains.

Livestock typically consume the infective cysts on the pasture, and then contract the parasite.

The parasite migrates through the liver for a period of six to eight weeks causing extensive damage, resulting in significant production losses.

The impact depends on the industry, but for beef cattle it can result in reduced weight gain, particularly in young cattle, while also creating fertility problems.

Jane Kelley is a La Trobe University PhD student working on liver fluke control and management in the Victorian dairy industry.

‘‘The biggest concern for Australian beef producers is that liver fluke can cause excessive weight loss by as much as 20 per cent per head depending on the number of flukes and the nutritional status of the animal,’’ Ms Kelley said.

That figure translates to a substantial hit on profit margins, especially for larger producers — and while it’s difficult to be sure exactly how widespread a problem liver fluke is across Australia, Ms Kelley reports that in Victoria, for instance, liver fluke is now as prevalent and widespread as it was before triclabendazole was introduced as the main treatment 30 years ago.

‘‘The problem is that triclabendazole-resistance is now very prevalent, and in many cases triclabendazole has actually become redundant,’’ she said.

‘‘Farmers have relied on triclabendazole for the past 30 years, but the lack of product rotation has created a perfect storm for drug resistance.

‘‘In Victoria alone, 43 per cent of dairy farms are infected, and areas with irrigation will generally have higher rates of infection than that.’’

Liver fluke fecal egg count tests are one of four main methods used to detect the liver fluke infection, and Ms Kelley reveals that during one triclabendazole resistance study, some young cattle that had been treated with triclabendazole had egg counts averaging 98 after treatment, with some as high as 300.

‘‘Considering that any count higher than five is cause for concern, these are very extreme infection and resistance levels.’’