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Sheep update

24 February 2015

The number of diagnoses of parasitic gastroenteritis (i.e. worms) made during December was 70% higher than any of the previous three years. The mild November may have had a part to play as could the high levels of cobalt and selenium deficiency found during the autumn. Good grass availability and consequent reductions in supplementary feeding may have lead to this poor trace element status.  Any investigation of poor growth rates in lambs should consider both worms and trace elements.  Remember that long acting wormers containing moxidectin have poor or no persistence against some types of worm found at this time of year.

Looking forwards to lambing it is interesting to note that more cases of swayback than usual were diagnosed in 2014. Historically it has been said that reduced feeding of concentrates (and therefore lower copper intakes during pregnancy) in mild winters leads to increased problems with swayback.  Winter 2013/14 was mild and if 2015 continues in a similar vein swayback will be something to look out for.  Enzootic abortion (EAE) was diagnosed in December for the first time this lambing season and serves as an important reminder to isolate aborted ewes and collect foetuses and placentas for investigation.  Over the last 10 years EAE and Toxoplasmosis have accounted annually for between 50 and 65% of all ovine abortion diagnoses despite being preventable by vaccination.

Winter is always the peak time for diagnoses of sheep scab with five cases confirmed in December. Diagnosis of scab relies on examination of skin and wool samples under the microscope and is carried out free of charge at all 8 SAC Veterinary Laboratories.  The test will also detect lice if they are present.  Unless you plan to dip, treatments for the two conditions are different so the cause of itchy sheep should investigated before any products are used.

As a result of the dry summer one problem we are not seeing much of is deaths from liver fluke. Fluke infection is still out there but at a generally lower level.   A large flock collected faecal samples from three different groups of sheep to check whether triclabendazole was working correctly.   Fluke infection was confirmed and following treatment the same sheep were sampled again two weeks later.  All samples tested positive for a second time with the coproantigen ELISA test confirming triclabendazole resistance.  In the future, in high risk fluke years, it may be difficult to control losses due to fluke in this flock.  Late winter/early spring is a good opportunity to carry out this testing particularly if ewes are housed for lambing making sampling quick and easy.


Heather Stevenson, Veterinary Investigation Officer, SAC Consulting

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