Managing Fluke in Cattle & Sheep

Author: Kaisa Velstrom BVM&S MRCVS vet in St Columb for Westpoint Farm Vets, part of VetPartners.

It's the time of year where fluke can pose a higher risk to your sheep and / or cattle. This can occur at all ages as no natural immunity develops during their lifetime. There is evidence that due to climate change, changing management practices and livestock movements fluke habitats are spreading into new areas of the country. 

This year's grazing season has been quite warm, and generally wet, which means the risk might be considerably higher than that in 2018. It is advised to actively follow the fluke forecast to see what the current situation in your area which you can do on the NADIS website (https://www.nadis.org.uk/). Subscribe and you'll get notifications straight to your Inbox.

Compared to cattle, acute outbreaks are more common in sheep, with signs including sudden death, general dullness, anaemia, shortness of breath, rapid weight loss and 'bottle jaw'.

Diagnostic testing

There are a wide array of diagnostics available to detect farms / animals at risk, and also to support treatment decisions.

For sheep and cattle, faecal egg counts (FECs) are used widely as an aid to diagnose infection. Unfortunately, they cannot detect pre-patent* infection and should not be relied upon for the diagnosis of acute disease. Post treatment samples should be taken a minimum of 6 weeks post treatment as there is prolonged shedding of fluke eggs (up to 3 weeks), even after successful treatment.

In sheep, post-mortem in acute outbreaks is probably the best approach. A copro-antigen detection ELISA has become available for sheep as well (individual animal and drug resistance testing) but appears to be less sensitive in cattle. It is useful for detecting infection two to four weeks before eggs are detected in faeces but appears unsuitable for composite faecal samples in either sheep or cattle antigen testing. Also, blood samples can be taken to see exposure.

An ELISA for cattle that detects antibody in serum and milk samples can detect early, from 2-4 weeks after infection, but serum antibodies are known to persist for 4-10 weeks after treatment, so a positive result does not prove that an active infection is present.
In beef cattle, best practice is to combine feedback from the abattoir, faecal egg counts and animal performance. Composite faecal egg counts can be informative, though only provide information about whether fluke is present.

With dairy cattle, ELISA bulk milk sample three or four times a year will monitor levels of infection and efficiency of control programmes.

Treatment strategies

The products (1,2) available on market target different ages of fluke, so it is important to use the flukicides according to your farm risk and also make sure you are dosing correctly. Therefore, it is strongly advised that farmers discuss product choice and timing of treatment with their vet.

None of the products have prolonged activity, so animals can pick up infection immediately after treatment if left on liver fluke infested pasture. It is also strongly recommended to follow up the efficiency of treatments as there is increasing evidence of resistance to triclabendazole in UK.

When buying in new stock, it is important to remember that any animals coming onto your farm could be a potential source of new parasites and/ or drug resistance. As a consequence, quarantine measures should always be undertaken.

Control

Prevention strategies including quarantine and targeted treatments, which will vary between farms depending on whether there is known history of fluke infection, and/ or if animals are grazing on potentially infected pastures. A realistic aim should be to know your risks and have a control program in place with your vet to reduce the level of infection.

1 See the COWS ‘Flukicide Products for Cattle' guide for more information.


2 See the list of flukicide products for sheep on the SCOPS website


*prepatent period: the period between infection with a parasite and the demonstration of the parasite in the body especially as determined by the recovery of an infective form (as oocysts or eggs) from the blood or faeces.