Treating cattle for liver fluke this winter

How do I know if I need to treat my cattle for liver fluke this winter? 

‘Because I’m in Kaitaia’ or ‘because I’m in Greymouth’ are quite reasonable answers to this question! That said, it is worth noting that liver fluke does not affect every animal, or every farm, the same, even in high-risk areas. 

New Zealand research has highlighted that there is high variation between farms, and variation between individual cattle on a farm (and even within a mob) for levels of fluke infection. It would be neat if there was a really accurate and cost-effective test that could detect which those animals are, but unfortunately, we don’t currently have that capability. 

So, we rely on district history, farm history, and what we know about each mob of cattle, alongside some imperfect diagnostic tests, to make decisions. 

But first, a bit about fluke. 

How does fluke affect cattle? 

Immature flukes spend about eight weeks grazing their way through the liver, causing damage and bleeding, before arriving in the main bile ducts. Here they settle as adults. ‘More than a few’ adult fluke can cause thickening of the bile ducts and ongoing disturbance to liver function. 

Liver fluke can be a cause of poor weight gain, and in severe cases, even illness and death of individual cattle. Pregnant cows do not do well if made to share their livers with high numbers of fluke.  

‘Failure to thrive’ and anaemia (pale membranes of eyes, gums, vulva, and in advanced cases, fluid swelling under the lower jaw) are common signs. But these are also signs of other diseases and are not specific to fluke. Farmers sometimes report cattle showing signs of abdominal pain and salivation – this may be caused by the immature fluke moving across the wall of the intestine on the way to the liver, or when they are roaming around in the liver tissue (ouch). 

Young cattle are more susceptible to fluke infection than adult cattle. As cattle mature, they develop some resistance to fluke. A scarring reaction in the liver reduces new fluke establishment and shortens the lifespan of existing fluke. So, fluke scarring on kill sheets at slaughter doesn't necessarily mean live fluke are present.  

If you are a finisher, it’s possible that ‘fluke’ on kills sheets originated from a previous property. 

Cattle that are underfed, or under pressure from other disease challenges, have less ability to mount an effective immune response to liver fluke. As with all internal parasites, good nutrition and management is extremely helpful. 

How do cattle pick up liver fluke? 

The life cycle of liver fluke in New Zealand involves a freshwater snail. However, it’s not the snail itself that causes fluke disease. The infective stage is a cyst that forms on grass blades after a mobile stage of the life cycle that has wriggled out of the snail’s body (ugh!) to settle on the grass blades. These cysts can last for many months on pasture but are susceptible to freezing and drying. 

So, your cattle must graze grass near or within waterways, to become infected. They don’t pick up fluke directly from drinking water, or from consuming snails. 

After a well-fed summer with good pasture cover, cattle are more likely to have grazed away from those wet margins, meaning fluke exposure is likely to be lower than in a dry year. The opposite can be true in flat areas in wet summers where snails may have spread further across pasture in free-lying water - especially if pasture cover is short. 

How do I know if fluke is a problem in my cattle? 

‘District’ and ‘farm history’ are important risk factors, with the Far North, East Coast, Northern Hawkes Bay, and the South Island’s West Coast historically being the bigger fluke risk areas.  

That said, not all farms in these areas may be equally affected, with access to waterways, presence or absence of a reticulated water system, and general level of feeding being key factors. 

A large slaughter study of Scottish cattle highlighted that while livers from some farms had high levels of fluke scarring, days from birth to slaughter on these farms could be shorter than on farms where livers had less fluke scarring, meaning that nutrition and management probably have a large role to play in animals’ ability to tolerate fluke infection. 

Data is always good for making decisions, and here are the diagnostic options for liver fluke: 

Post-mortem examination: On mixed farms, autopsies of tail-end ewes in early winter is a very practical option. If these ewes are not infected with fluke, it's highly unlikely cattle on the same property will be affected. Autopsies of tail-end cattle can be useful on cattle-only properties. 

Fluke blood test: Can indicate an antibody reaction to fluke – although these antibodies can remain raised in blood for 2-3 months after fluke have been kicked out by the immune system. 

Fluke egg count: Looks for fluke eggs in dung samples – a bit ‘hit and miss’ as fluke don’t consistently pass eggs every day. 

Faecal antigen ELISA test: A newer option that can detect fluke in the bile ducts even when eggs are not present in the faecal sample. 

When should you treat in winter? 

If you have confirmed fluke is present at a level that requires treatment, timing in winter depends on where you farm:  

In areas with cold winters - fluke activity tends to stop over winter. A single treatment in early winter may be all that's needed, as no further infection is typically picked up from pasture until the following season. By winter, any existing fluke infection will mostly be mature - and mature flukes are generally easier to treat, with a wider range of effective products available.  

In areas with warm winters - the fluke life cycle may continue through winter, so an additional late-winter or spring treatment may be required to clear infection accumulated over winter. 

Which products are registered for cattle? 

There are four anthelmintics currently registered in New Zealand for treating liver fluke in cattle: 

Treating calves requires special consideration. Most of the drugs above are included in a combination product with another active to give ‘roundworm control’ as well as fluke treatment. However, none of them contain levamisole, which is important for treating Cooperia on most cattle properties. If calves have been under regular or semi-regular treatment with a product containing albendazole, they may not need a specific fluke treatment. It is wisest to consider fluke treatment and worm treatment separately in calves, ensuring that the ‘most effective’ oral product is used for both.