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The wet summer has meant that there is an increased risk of liver fluke in cattle and sheep this winter, particularly on farms in the west where there were highest levels of rainfall.
However, a liver fluke issue can exist on farms regardless of whether grazing conditions have been wet or dry. Where dosing against fluke took place at grass, liver fluke may not be a huge issue. But where cattle have received no treatment, it is time to assess the fluke challenge.
Testing for fluke
Cattle with a heavy fluke burden may require a two-dose strategy to control the problem, while for most cattle types a single dose should suffice. There are various different methods of testing for liver fluke – this can be done in dairy herds by having milk samples analysed and through blood serum samples. These tests detect the presence of antibodies.
Analysis of faecal samples can show if fluke eggs are present. In the last few years, laboratories have started to differentiate between liver fluke eggs and rumen fluke eggs – allowing farmers to be informed if rumen fluke could also be an issue on the farm. However, faecal egg count tests do not necessarily give the complete picture.
Fluke at acute or immature stages can cause serious damage to the livers of cattle and sheep – more so sheep, where large volumes are present – while faecal samples done at the time can show little to no eggs if the fluke is not mature.
Symptoms of fluke damage
Winter fluke issues are most common during early winter. Sub-acute fluke is most common before December, while chronic fluke is most common from December onwards. During the sub-acute stage, immature fluke migrate to the liver, causing damage and bleeding. The mature stage sees fluke migrate up the bile duct, causing chronic liver damage and anaemia as they feed.
The most common signs of fluke in cattle are poor thrive, loss of condition and, in very advanced stages, bottle jaw and anaemia during the chronic phase. Acute fluke is rare in cattle, but a serious risk in sheep, while sub-acute fluke is generally only seen in calves and sheep. In sheep, sub-acute fluke causes sudden death, and can be seen through poor thrift, poor fleeces and anaemia. Chronic fluke in sheep can be seen through poor thrive, bottle jaw, and anaemia.
Table 1 shows the active ingredients which are effective against early immature, immature and mature liver fluke. Products containing oxyclozanide are effective at killing both rumen and liver fluke, but only mature stages – they will not kill 100% of the fluke in the animal.
Triclabendazole-based doses are the only product that can kill early immature, immature and adult liver fluke with an effectiveness of between 90% and 100%. These have been widely used in cattle herds and sheep flocks. However, in sheep flocks where there has been widespread usage of the product over several years, resistant fluke have emerged, which means that the efficiency of the product is diminished.
Dairy farmers should note that albendazole- and oxyclozanide-based products can be used on cows intended for milk production. Pay particular attention to withdrawal periods. Some triclabendazole products may be used on animals intended for milk production, but consult your vet or agent.
Timing of dosing
To maximise thrive and reduce the risk of liver damage, we want to limit the fluke burden. Where cattle have not been treated for fluke during the summer months and faecal samples suggest a heavy burden, then a two-dose strategy may be required.
Where resistance is not an issue, using a product that is active against immature and mature, or early immature, immature and mature, may be beneficial. These cattle can then be treated post-housing.
Remember that mature fluke are over eight weeks of age, so if you are using a product that is only active against mature fluke, animals must be housed for at least eight weeks to get high efficiency. Where the fluke burden is low and resistance is not an issue, often finishers will use a triclabendazole-based dose at housing. When dosing, ensure that you know the weight of the animals being dosed to ensure there is no under-dosing or overdosing taking place.
Rumen fluke
Liver fluke can decrease cattle thrive and can be fatal. Rumen fluke, although they will affect thrive, will generally not kill an animal. However, they can cause damage to the small intestine at the larval stage as they migrate to the rumen.
There are only two products on the market that will kill rumen fluke: Zanil and Levafas Diamond. Both contain the active ingredient oxyclozanide. Vets are telling farmers to be very careful with the use of both products as they are the only means to control rumen fluke.
It is advised that where farmers think there is a specific problem with rumen fluke in an animal, to treat just that animal. Blanket treatment is not advised due to the risk of resistance emerging.
Farmers should also be aware that oxyclozanide is only effective against rumen fluke and mature liver fluke. If there is a rumen and liver fluke problem, a dosing strategy should be devised to tackle each separately and your vet should be consulted before doing so.
Lice control
Lice affect all cattle, especially during the winter period. Signs of lice activity are cattle scratching and/or licking, poor coats, excess hair loss and, in some cases, anaemia.
There are two types of lice that affect cattle: biting and suckling lice. Mange mites may also be an issue. One thing that farmers need to be aware of is that not all products that will kill suckling lice will kill biting lice. Pyrethroids and externally applied endectocides are the only two active ingredients that will kill both biting and suckling lice, and mange mites.
Timing of treatment is crucial. When animals are in close proximity, lice can transfer quickly and easily from one animal to another. The life cycle of lice takes just over 34 days, so fast replication can be an issue. Treatment for lice will only kill hatched lice, not the eggs.
For that reason, the need for secondary treatment will depend on the number of eggs laid and the severity of the problem. It is advised that animals are treated for lice at housing to keep them under control. Where lice are not treated at housing, more severe issues can occur in November and December as lice populations grow quickly.
Under-dosing a big risk in fluke control
Inadequate liver fluke control is an issue on a high percentage of suckler and beef farms. The main problem stems from farmers underestimating the weight of animals, especially cows, and as a result administering a lower dosage rate than required to achieve a satisfactory kill of liver fluke parasites.
Farmers are advised to try to get an accurate estimate of animals, ideally by weighing a sample of animals, to get an accurate weight of cows of varying size or condition. Lower than recommend dose rates administered can be often be as a result of issues with dose guns (guns drawing air) or flawed dosing techniques.
When selecting products, products identified for providing the best treatment contain the active ingredient trichlabendazole (for example Fasinex, Endofluke, etc) and Trodax (active ingredient nitroxyil). Caution should be given to selecting combination products as many of these are average in their efficacy against liver fluke.
Where animals are being treated with Trodax, there may be merit in delaying treatment until all fluke parasites enter the immature and adult stage, but this should only be done where the risk of liver fluke is not seen as very high.
Liver fluke control is highly important in autumn-calving cows, as the presence of liver fluke parasites adds to nutritional stress and has the potential to reduce animal performance and add to delayed resumption of cyclicity.
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