Meeting re liver fluke and the new schmallenberg virus
EVENT REPORT NORTH WEST LIVESTOCK PROGRAMME ALLERDALE LIVESTOCK GROUP AND HERDWICK DEVELOPMENT GROUP JOINT MEETING Liver Fluke and the new Schmallenberg Virus Hundeth Hill Hotel near Cockermouth March 5th 2012 7.30pm
Thirty one farmers were present at this meeting with presentations given on Schmallenberg virus by Amanda Carson MRCVS and by Rebecca Mearns of the VLA on liver fluke which is an increasing problem particularly in West Cumbria. Starting with a report on the new Schmallenberg virus, Amanda Carson MRCVS explained that in October 2011 fever and poor condition was observed in 80 dairy herds in the Netherlands, showing clinical signs of dysentery, fever and milk drop. Salmonellosis, BVD and parasitism were ruled out as causes and at the time no symptoms were noted in sheep. Soon after a similar condition was also noted in Germany and after extensive blood testing a new virus was identified in late December, both countries having shared their findings. The UK was alerted to this new disease in December and all veterinary practices in the UK were informed by letter. In December 2011, 30 flocks in the Netherlands reported lambs born with deformities, including twisted necks, fused joints and abnormal brains, and the virus was found in these lambs. At the same time Germany identified the virus in a deformed calf. The first case of the virus was detected in Southern England at the end of January and it is suspected that midges blown over the Channel in August were the carriers. No cases in the UK so far have been related to imported animals. It has been noted that the disease often occurs in twin births with only one lamb (often male) affected. Deformities include twisted limbs or fused joints making lambing difficult; some lambs are born with nervous signs due to brain deformities. Laboratories across Europe are working to develop a blood test for antibodies to detect if animals have been infected - currently the only test available is for the detection of the virus at post-mortem of dead animals. Presently there are 85 holdings affected in the UK mostly in the South East and farmers are being asked to think carefully before importing animals as it appears the virus is spreading across Europe. It is not yet known how cows will be affected as they have a longer pregnancy and as spring calving approaches more cases in cattle may be seen. There is no suggestion that the virus can affect humans. Animals infected by viruses in the same family of Orthobunya viruses appear to develop immunity, though long term effects of Schmallenverg virus are as yet unknown. A vaccine is currently being developed though this could take 18 months. Rebecca Mearns from the Veterinary Laboratories Agency at Penrith followed on with a presentation on liver fluke, which has been a big problem among sheep in Cumbria and South-West Scotland due to the very mild, wet conditions experienced in the North- West. In the South of England where drought conditions have been experience, fluke is virtually absent.
Rebecca Mearns explained that the culprit was a flat worm which thrives in mild wet conditions, affecting cattle, sheep, horses, deer and man, though the main problem was in cattle and sheep. A small mud snail is the intermediate host, fluke having a long, complicated life cycle and loving wet areas, particularly around feeding troughs, and is ingested from animals grazing infected pastures. Once ingested the liver fluke migrates through the gut into the liver tissues and into the bile duct, each adult producing 50,000 eggs a day into the dung contaminating the pasture with the eggs turning into a small snail-like parasite within a few weeks. The eggs form cysts on the grass and animals ingest these and the life cycle is complete within a three month period. The snails hibernate in the mud during the winter months ready to emerge in Spring and Summer, the disease manifesting itself in Autumn. Fluke cases can be:-
1) Acute – appearing in Autumn-Winter with damage from immature fluke.
2) Sub-acute – late Autumn and Winter with damage caused by immature and
3) Chronic – Damage by adult fluke over some years (one inch long in the tubes
of the liver) during Winter and Spring. Symptoms are weakness, poor reproductive performance, poor fleece quality, bottle-jaw and anaemia.
1) Examining faecal sample for eggs – needing 40 grams of dung. The process
only needs to identify one egg to know the sheep has fluke and if eggs are present then need to treat intermittently and retest until clear.
2) Post mortem - opening of gall bladder. Adult fluke spill out of a pale liver with
a correlation of age to the size of flukes (7mm or less – early immature, 7-19mm immature flukes, over 20mm – adult flukes). Acute livers are wasted and this is an increasing concern from abattoirs. If the whole liver is examined at P.M. then it is possible to correlate the age and size of fluke and decide what type of treatment is required.
3) Histology – Research tool to identify whether flukes survived post treatment
with Triclabendazole (TCBZ), but expensive as need several examinations.
4) ELISA Test – detects fluke secretions in sheep faeces.
5) Blood tests – liver enzymes – can measure damage of liver cells and bile
ducts – useful for diagnosis of acute fluke.
Rebecca listed the five different types of drugs available on the market under different trade names, suggesting a rotational use of TCBZ , Closantel or Nitroxynil to avoid TCBZ resistance, and repeating treatment every six weeks to get rid of immature flukes. The other flukanides are Oxyclizanide and Albendazole. She further explained that TCBZ was the only drug to treat immature flukes; this is effective from 2 days of age and available in combi-wormers. It is therefore the best drug to use in Autumn although may be traced in the milk of dairy cattle. Closantel and Nitroxynil are effective from 6 – 8 weeks and are better to treat adult fluke. Oxyclizanide and Albendazole are best used in Spring and kill mature
fluke (advised not to use the latter at tupping time as can cause abnormality in lambs). Another factor for farmers to consider is land management avoiding grazing risky pastures at different times of year and there is the suggestion that acidic ground may be less prone to fluke infestation. Rebecca also warned that sheep wintered on dairy farms may carry the worms and infect these pastures. There is interest amongst the farmers in conducting fluke trials and Amanda Carson MRCVS as Secretary of the Herdwick Sheep Breeders Association is looking into this. For more information on this event please contact [email protected]
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