Cold snaps haven’t been enough to remove fluke risk for cattle and sheep
Although, as forecast, cases of disease due to liver fluke have remained relatively low so far this winter, there are reports of both acute and chronic disease in some areas of the UK. This means livestock farmers must not drop their guard, warn experts in the Sustainable Control of Parasites in Sheep (SCOPS) and Control of Cattle Parasites Sustainably (COWS) groups.
Philip Skuce of Moredun sits on both groups. He says: “Testing is critical to make sure farmers don’t treat too soon, or unnecessarily, or get caught out and miss a vital treatment. The cold snap in December will not have killed off all the liver fluke on pasture, so animals could still be picking up infection that could go on to cause disease. Livestock farmers must continue to test if they are to ensure any treatment is both necessary and given at the right time and with the most appropriate product.”
Diagnostic reports from APHA and SRUC underline the value of using blood testing for fluke in sentinel calves.
Heather Stevenson, a vet with SRUC, explains: “In September and October, less than 1% of the animals tested were positive, showing the majority of farms did not need to treat at that stage. This rose to 10% by mid-November and 13% in December, which is still a small proportion of farms and highlights the potential to treat unnecessarily or too early if traditional timings are followed.
“In January, 30% of samples tested for coproantigen (a faecal test) were positive, which underlines the need to keep checking sheep that have not yet been treated.”
John Graham-Brown from the University of Liverpool stresses how important it is to repeat testing until the risk period is over. He says: “A negative test does not mean you can sit back and relax. Plan to repeat tests in three to four weeks’ time to make sure you don’t get caught out.”
This is echoed by Rebecca Mearns, Vice President of the Sheep Veterinary Society and vet with Biobest. She says: “We are seeing some faecal samples that are positive for fluke eggs this winter, but with infections tending to be later, farmers must not assume one negative test means there are no liver fluke, it may be because the fluke are not mature enough to lay eggs.”
Now is a good time for housed cattle to be tested for fluke, using a composite dung test to check for fluke eggs. If cattle are positive, choosing a treatment that targets adult fluke and avoiding products containing triclabendazole, will reduce resistance selection pressures on the parasite. Reducing eggs going onto pasture in the spring can help reduce challenge this coming autumn. Fluke figures in FEC results, say SCOPS and COWS experts The inclusion of rumen fluke figures in faecal egg count sample results isn’t necessarily a cause for concern, according to experts in the Sustainable Control of Parasites in Sheep (SCOPS) and Control of Cattle Parasites Sustainably (COWS) groups.
SCOPS and COWS has been working hard to encourage livestock producers to use FECS to monitor liver fluke burdens in cattle and sheep, particularly as this internal parasite becomes increasingly unpredictable – and this has brought rumen fluke under the spotlight too.
Diana Williams of the University of Liverpool sits on COWS. She says: “Many farmers and their advisers are, quite rightly, looking at FEC sample results at the current time. This is an important element within active liver fluke monitoring. But within the SCOPS and COWS industry groups, we are keen to ensure this does not lead to unnecessary treatment of rumen fluke in sheep and cattle.
“Increasingly, laboratories will record the incidental presence of rumen fluke eggs in faecal samples, but this does not indicate a need to treat.
“A positive egg count only indicates the presence of adult rumen fluke in the rumen. On the very rare occasions that disease is caused by rumen fluke, it is due to large numbers of immature rumen fluke in the duodenum (duodenitis). There are no specific diagnostic tests for immature rumen fluke, and they would be negative on faecal egg count.”
SCOPS and COWS provide these facts about rumen fluke.
The detection of rumen fluke eggs only indicates the presence of adults in the rumen. In the majority of cases, it does not indicate any production loss or need to take action.
Liver fluke remains the more important of the two fluke parasites. Co-infections of liver fluke and rumen fluke are common, but any treatment should focus on the presence of liver fluke.
Disease due to rumen fluke is not typically caused by adults in the rumen. It is due to a large build-up of immature rumen fluke in the duodenum and is the result of a very high challenge on pasture, leading to large numbers of immature parasites in the intestine.
If you are concerned about rumen fluke, discuss results with your vet. There are no licensed treatments for rumen fluke and the only active that can kill them (oxyclozanide) has a low safety margin and must be used carefully. Cases of toxicity, resulting in blindness, have been reported
Oxyclozanide can only be prescribed by a veterinary surgeon for use against rumen fluke and should only be used where there is conclusive evidence that an infestation of rumen fluke is likely to be causing a health/ welfare issue.
It is the opinion of SCOPS and COWS experts that anecdotal reports of production and/or health benefits in response to treatment of rumen fluke are unlikely to be due to removal of adult rumen fluke and much more likely to be as the result of removing a co-infection of liver fluke that may not have been reported.
Farmers should talk to their Vet/RAMA to discuss whether any treatment is necessary.