It's a parasite with a very complex life cycle and requires the mud snail as an intermediate host. Due to this, it's normally found in wet, humid environments, which is why it is only really prevalent in New Zealand here on the West Coast and up in Northland.

Once the immature fluke leaves the snail it waits on vegetation (like grass) to be ingested by its final host. It then breaks out of the intestine and heads to the liver, where it finally matures into its adult form in the bile ducts – causing a lot of damage. It's here that it lays its eggs, which then pass into the intestine and spread back onto the pasture in the faeces. Those then are picked up by mud snails and the cycle keeps going!

There aren't a huge amount of options for effectively treating liver fluke. Currently Triclabendazole is the only commercial drug that kills all stages of the fluke in their life cycle. There are a few other drugs available, but they only kill the adult fluke and do nothing to the immature stage that are in the intestine or reaching the liver.

There are several products containing these drugs. We recommend oral products as the best option, as they allow for more accurate dosing which makes them more effective. All the injectable products only kill the adult fluke – however, they do also have some effect on other parasites like worms and lice. There are various pour-on products too, but these are our least preferred option as they require an extremely high concentration of the drug and the watery solution can easily run off the animal or be washed off by rain.

There has only been one study* of Triclabendazole and resistance in New Zealand, which was completed way back in 2009. At the time, this study only found one resistant location. However, anecdotally this has increased since then. A lot of these resistant properties have been linked to the use of pour-ons, which reinforces our belief that they are not the best way to deliver drugs.

It is important to note that all liver fluke products have milk withholds. The oral product Flukecare has a 35-day milk withhold and 28-day meat withhold, the injectable product I-con F is 14 days for milk and 28 days for meat, and all the pour-on products (such as Cydection and Reflex F) have a very extended 91-day milk withhold timeframe. Please be aware of these withhold times, particularly if you are milking right to the end of the season and wanting to start supply in July or the start of August. In this case, pour-ons would not be a viable option.

If liver fluke has been identified as an issue through bulk milk screening or if it's popping up on kill sheet reports, please talk to one of our vets about the right option for liver fluke control on your property.

*Hassell C – Publication: Proceedings of the Society of Sheep & Beef Cattle Veterinarians of the NZVA, p 4.14.1-4.14.2, Jan 2012.