Wednesday, 31 October 2018

It’s the season to test your livestock for parasites

Lis King, AHDB Sheep Scientist, gives a timely reminder for sheep and beef farmers to monitor their livestock for worms and liver fluke 

Internal parasites (worms and liver fluke) pose a significant threat to animal health and performance. Farmers are encouraged to plan their grazing strategies to reduce the risk of infection and use available monitoring tools. Autumn is a high risk period for liver fluke, and this coincides with some of our Challenge Sheep farmers finding high worm egg counts in their flock’s faecal matter.

Fit mature stock should not require worming but young or thin stock may require a wormer. Look out for risk forecasts on the National Animal Disease Information Service (NADIS), Sustainable Control of Parasites in Sheep (SCOPS) and Control Of Worms Sustainably (COWS) websites and speak to your vet for advice.

The peak fluke season is predicted to be later and shorter this year following the hot dry weather. In spite of this, high snail numbers have been observed in some areas of the country. Fields with a lower risk of fluke infection are drier, better drained with no persistent wet patches. Those that have been re-seeded, contain brassicas or were not grazed earlier in the year are also lower risk. Sheep are more likely to die from liver fluke infection during autumn than cattle. Symptoms of the disease in cattle are less obvious, including reduced feed intake, loss of body condition and slower growth rates. 

Testing for worms and fluke will help to avoid unnecessary treatments and checks whether treatment has been effective. It can also inform decisions about which stock to treat, what to treat them with and when. Importantly, it will allow you to differentiate between liver fluke and worms, particularly as infection with liver fluke can produce similar symptoms to haemonchus (worms).

Testing tools include: faecal egg counts (FECs), the coproantigen test, blood (ELISA) test, post-mortems of dead animals and abattoir liver returns. When using FECs it is important to remember that the results need to be considered with other information such as age, stocking density, time of 
year and performance levels.

In cattle, treatment decisions should be based on the likelihood of cattle having grazed infected pasture that season and on their treatment history. Using FECs to test for gut worms at housing is not useful because treatment needs to be targeted at the immature stage of the lifecycle when eggs have not yet been shed.

Top tips given by SCOPS and COWS include:

· Don’t get caught out by treating too early. Monitor to determine the need and timing of treatments

· In lower risk situations, consider treating sheep with closantel or nitroxynil rather than triclabendazole. Re‐infection (when treated animals are put back on to contaminated areas) is still a concern.

· Worms (including haemonchus, which can produce signs similar to liver fluke disease) may be the problem.

· Investigate losses. A post mortem is still the best way to establish whether liver fluke is present.

· Monitor abattoir returns carefully for evidence of liver fluke.

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