What problems are cropping up regularly in the vet labs?

SHEEP

Investigation of sheep abortion kept the labs busy during spring. With lambing over for many people the top three diagnoses were EAE – 79, Toxoplasmosis – 62 and Campylobacter – 34.   EAE and Toxoplasmosis take the top two places year after year bringing home how many lambs could be saved if ewes were vaccinated.

The second week of May saw lamb deaths due to infection with Nematodirus worms. St. Boswells again had the dubious honour of reporting the first case of the season but in the same week Ayr and Dumfries found large numbers of Nematodirus eggs in dung samples from scouring lambs.   Remember that scours and deaths can occur before eggs can be found in dung and a postmortem can be required for diagnosis.  A mid May hatch of nematodirus can lead to problems as by this time main season lambs are eating enough grass to pick up large numbers of worms.  The highest risk fields are those grazed by young lambs in spring year after year.

Ayr diagnosed Pieris sp. poisoning in sheep from three different flocks during March.  All were accompanied by a history of straying or access to hedge clippings with typical leaves being found within the rumen content.  These cases followed an earlier episode of Pieris sp. poisoning in February which resulted in the death of eight ewe lambs at wintering.  In that instance the sheep had strayed from their original field along a roadside.  Secure fences and checking for fly tipping of garden waste can prevent unnecessary deaths.

Despite the fluke risk being low this year both Thurso and Dumfries diagnosed chronic liver fluke as the cause of multiple ewe deaths in flocks around lambing time. Ewes were thin and lambs were born with low body weights.  Fluke treatments had been given and it was advised to first of all check that best dosing practice had been followed.  Welfare considerations based on impending lambing and poor body condition meant that it was more appropriate to re-treat with a different flukicide and postpone screening for possible resistance until a later date.  Ideally monitoring for flukicide resistance should be carried out when ewes are healthy and mature infection is present.  Late winter or early spring can be a suitable time.

Listeriosis was diagnosed on 12 occasions during March with Inverness confirming the condition on five occasions.   This total is higher than usual with between two and five diagnoses being recorded in March during the previous four years.  The reason for this is not clear.  Listeria bacteria are present in the soil and can be found in high numbers in silage particularly where the pH is too high and/or bales have been punctured allowing air to enter.

CATTLE

SAC C VS have been busy investigating cases of bovine abortion this spring. Diagnosed bacterial causes included Bacillus licheniformis, Salmonella Dublin, Listeria monocytogenes, Pseudomonas aeruginosa, Campylobacter fetus, Histophilus somni, Trueperella pyogenes, Escherichia coli, Streptococcus dysgalactiae and Streptococcus pluranimalium. The fungi Aspergillus fumigatus and Scedosporium proliferans were also diagnosed. Outbreaks of abortions due to B. licheniformis, Listeria spp. and fungi are often associated with contaminated or spoiled silage. Salmonella Dublin and venereal strains of Campylobacter fetus infection are commonly involved in abortion storms while the abortions due to the other bacteria tend to be one-offs. Bovine viral diarrhoea virus (BVDV) was detected in foetuses from nine farms so far this year. As the national BVD eradication programme progresses, examination of aborted or stillborn foetuses will become an increasingly important method in surveillance.  Nesopora caninum, a protozoan organism, has also bee responsible for outbreaks of abortion. An abortion may be the first indication of an infectious disease entering a herd.  Testing of abortions is therefore a key part of herd health monitoring.

Cattle have been calving in good condition and have potentially been overfit. On some farms this has lead to slow or traumatic calvings resulting in stillborn or weak calves. In one case, the carcase of a two-day-old Aberdeen Angus-cross bull calf was submitted for postmortem examination. Its dam was from a batch of 22 Aberdeen Angus-cross heifers that were bought in at five months in-calf. Six out of eight of the heifers that had calved so far had required assistance and calves born were lacking vigour. At postmortem examination extensive subcutaneous swellings were evident over the limbs, neck and chest consistent with dystocia. Extensive haemorrhages were present in the muscles over the left ribs and over and into the joints. There were six fractured ribs on the left side resulting in infection in the chest.

Heather Stevenson & Helen Carty, Veterinary Investigation Officers, SAC Consulting