Treating liver fluke in cattle

When treating liver fluke in cattle it is important to select a product that will kill the stages of liver fluke that we expect to be in the animal at that time. Stages of liver fluke present at any given time will vary from farm to farm and year to year, so a fixed time treatment protocol is unlikely to give reliably effective results. Different active ingredients are needed at different times of year to target the different stages of fluke that will be present in the animals (see table below). To target these treatments effectively, we need to know when the fluke challenge starts in any field or farm.

Pasture risk refers to the risk of animals being infected with fluke and the stated months are for guidance only as these timings will vary considerably from year to year.

There are many approaches to managing liver fluke on-farm and working with your RAMA or Vet to implement a parasite management plan following the principles discussed here will help reduce the economic and production losses associated with liver fluke.

: In the autumn/early winter, we get the highest number of early immature fluke and so need a product that kills these. The only active to kill early immature fluke - ie fluke that is under 5 weeks old is triclabendazole, the active in Combinex for Cattle™ and Fasinex 240™. Oral triclabendazole kills liver fluke down to 2 weeks old in cattle.
However, where triclabendazole resistance has been confirmed on a farm, an alternative active should be used, eg closantel. As no fluke products are long acting, re-infection will occur if animals are allowed to continue grazing the same area. When pasture challenge is high, it is therefore essential to move animals to a lower risk area or consider housing.
: The decision made at housing for fluke treatment depends on multiple factors, but with fluke having a significant impact on growth rate and time to finishing¹ we need to ensure what we do is effective. This means using the right product, at the right time, using the correct dose and administering it in the right way. Unfortunately, no one treatment in isolation will kill all stages of fluke present without consideration of timing of dose.
Why treat animals for fluke at housing
There are two main aims for treating animals for fluke around housing:
to remove the burden picked up from the pasture during the months before housing, when the pasture levels of infectious stages of fluke are likely to be increasing. By removing this burden when housed, it will help the cattle to perform well over winter and achieve their potential growth and productivity
to prepare for the following grazing season: by correctly removing these immature fluke they will not develop into egg laying adults and contaminate pasture next year
Treatment options
For best treatment results, the number and age of fluke likely to be present needs to be considered. The NADIS fluke forecast and farm history will help guide this; generally in late summer/autumn, there will be increasing levels of fluke on pasture thus many newly acquired (immature) fluke within the cattle liver.
At the time of housing:
If infection pressure is high, it may be more beneficial to treat at the time of housing with a triclabendazole drench. Treating now offers convenience of handling at the same time of housing, which minimises handling stress. Triclabendazole drench removes most of the fluke as early as possible. However, any fluke under the age of kill at the time of treatment may survive and go on to affect the cow, meaning the cow will then need a second treatment (ideally with a different active) to remove any remaining fluke.
After the start of housing:
If infection pressure is low, and animals have been grazed on low risk pasture, it may be better to carry out testing to see if treatment is necessary or delay treatment to after the start of housing and use the appropriate flukicide. The benefits of this are that all stages of fluke present in the cattle would be treated by the correct flukicide; however growth rates may suffer initially until treatment is carried out. The flukicide of choice will depend on the timing of treatment:
2 weeks after housing - triclabendazole drench
6-8 weeks after housing - triclabendazole pour on
7 weeks after housing - closantel
8 weeks after housing - nitroxynil
NB An adulticide fluke treatment - e.g. oxyclozanide or albendazole - would be an inappropriate choice at housing as we expect the majority to be immature or early immature fluke, so an adulticide would be ineffective given at housing and delaying treatment by 10-12 weeks would risk a significant impact on growth rate.
When selecting the appropriate treatment, it is important to consider resistance to any flukicide previously diagnosed on farm and meat/milk withdrawal periods.
: The treatment of choice for beef cattle at this time will depend on if the cattle are housed or outside over winter.
Housed cattle
If the cattle were housed in the autumn, then they will not have been able to pick up new infective cysts. If they WERE NOT treated at housing, then a faecal sample can show if any infections are present. Alternatively you can monitor any signs of fluke from abattoir returns. If the cattle WERE treated at housing, it will depend on what they were treated with, and when:
If the cattle were treated at the start of housing with a product that eg only kills fluke from 7 weeks of age, some fluke will still be in the cattle and could be affecting performance. If these cattle are going out in the spring, they will be carrying adult fluke that will be producing eggs that will contaminate the pasture.
If cattle have been housed for 10 weeks or more then a product that kills adult fluke would be appropriate.

Outwintered cattle
If cattle are out during the winter, they may require a treatment as they may have potentially ingested more fluke cysts from the pasture after their autumn fluke dose. However, as the number of infective larvae on pastures will be declining, treatments should target both immature (from 8 weeks) and adult liver fluke, or adults only depending on the local risk.
The active ingredients of choice would be:
For immature fluke: triclabendazole pour on, closantel or nitroxynil
For adult fluke: albendazole, oxyclozanide or clorsulon
: By the summer, we would expect any surviving liver fluke to be adults. A targeted adulticide treatment (clorsulon, albendazole or oxyclosanide) at this time of year will remove any remaining adults and minimise the number of fluke eggs reaching pasture.

When to treat for liver fluke again

As treatments for liver fluke are not long acting, they will only remove the target age range of liver fluke that are present at the time of treatment. Follow up treatments will be necessary if animals continue to graze known fluke risk pasture. However, this should be targeted on evidence of infection.

Post treatment checks

As even a few liver fluke can have a significant impact on the performance of livestock, it is always worth checking that any treatment for fluke has been effective. This can be done using the coproantigen test or composite fluke egg counts following advice from your herd health advisor.