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 6-8 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 LaTrobe 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 head depending on the number of flukes and the nutritional status of the animal,” she reveals.
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, Jane 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. 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% of dairy farms are infected, and areas with irrigation will generally have higher rates of infection than that. In the Macalister Irrigation district located in Gippsland, we found liver fluke in 71% of the 400 cows tested. That’s a real problem, because wherever you have more than 25% of cows with the infection, you’ve reached an economic threshold where you’ll be getting significant production losses.”
Liver fluke fecal egg count tests are one of four main methods used to detect the liver fluke infection, and Jane 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 5 is cause for concern, these are very extreme infection and resistance levels.”
Jane describes some key steps to take when attempting to reduce liver fluke in cattle: “Liver fluke tends to be more of a problem with regions that have high rainfall – around 600 mm per year, or around 450 mm per year for farms with irrigation systems. These are the highest risk regions, because there’s more water to keep the snails alive that transmit the parasite. If you’re in one of those regions, it is important for you to regularly test your stock.
“We also recommend ensuring good fencing to limit stock exposure to infected habitats, as well as improving drainage and cleaning out troughs. But most importantly, farmers should consult a vet to work out the best diagnostic method for their situation, and then begin an eradication program. The ideal time to do that is during the autumn, this treatment will clean out fluke prior to animals facing the stresses of winter. For this treatment to be most effective, it should be administered following the onset of frosty weather. Fluke will begin to do the most damage from the 2-week stage onwards, so it’s vital to treat now, to limit production losses.”
Jane recommends the use of an alternative to triclabendazole that can still target both immature and adult stage flukes in Autumn. Animal health company Virbac offers two treatments for beef cattle which do exactly that – and most importantly they’re also effective against triclabendazole-resistant strains of all stages of liver fluke including the dangerous 2-week old fluke. NITROMEC® is the world’s first triple active injectable that uses the synergistic effect of clorsulon and nitroxynil to provide best-practice control of 2 week old fluke.
For Jane, the benefits of these types of control programs are clear: “In herds with triclabendazole-resistance, we’ve switched to other alternatives, and we’ve seen marked improvements for stock, including improved milk production, weight gain, fewer fertility problems and healthier coats. Now we’re into autumn, this is the right time to introduce a treatment program that can eradicate this costly infection, and safeguard your livelihood.”
For more information on Virbac’s liver fluke control programs call 1800 242 100.