Veterinary Services

Nutritional and metabolic disorders

Carbohydrate overload and ruminal acidosis following consumption of excessive creep feed was confirmed in a three-month-old lamb which died after a period of bloat. Two lamb deaths were reported in a group of 21 ewes and lambs on this Aberdeenshire holding.

SAC VS recorded eleven cases of pregnancy toxaemia.  The carcase of a two-year-old mule gimmer submitted to Edinburgh came from a group of 500 in which four were found dead and another three were recumbent and blind.   Necropsy revealed hepatic lipidosis and two large foetuses within the gravid uterus.  Blood samples received from two other affected animals had elevated serum beta-hydroxybutyrate (BOHB) values (3.1 and 5.0 mmol/l; reference range <1.3 mmol/l).  Dumfries also received blood samples taken from three ewes in late pregnancy, described as dopey and ataxic.  In that case BOHB values were 2.6, 1.3 and 2.6 mmol/l respectively.

Hypocalcaemia was diagnosed in two flocks in Ayrshire and Renfrewshire. In one case the diagnosis was made from a sample of vitreous humour obtained from the carcase of a ewe that died suddenly, ten days prior to lambing.  The same diagnosis was made in a recently lambed anorexic ewe that died despite treatment.  No mineral supplements or concentrates were being fed on the latter farm. 

Hyposelenosis was recorded in a lowground flock near Ayr in which seven lambs died over one week shortly after the start of lambing.  Affected lambs were born weak and unable to stand or suckle.  Neuropathology revealed extensive spongy change throughout the white matter and a paucity of myelin in the occipital lobe, suggestive of swayback.  However the liver copper content of an affected lamb was within the reference range, while liver selenium was found to be low.  SAC VS considered the clinical and pathological signs were due to selenium deficiency and immaturity. 

Parasitic diseases

Fasciolosis was again the commonest diagnosis made during the month, with acute and chronic disease continuing to cause deaths in ewes and hoggs in flocks in Ayrshire, Stirlingshire and Argyll.  This was despite flukicide treatment in January in some cases.  Re-treatment and continued monitoring was advised on farms on which flukicide resistance was suspected. 

Chronic fasciolosis was diagnosed by demonstration of liver fluke eggs in a faeces sample from a three year-old Saanen nanny-goat.

Nematodirosis

In Scotland the majority of incidents of nematodirosis are recorded during May and June, coinciding with the emergence of large numbers of infectious third stage larvae on pastures.  In these outbreaks most of the affected lambs are less than three months of age.  They are at a stage when they are consuming significant amounts of grass, but have not yet developed an age-related immunity to the worm.  Most outbreaks are associated with infections by Nematodirus battus worms, tens of thousands of which may be seen when gut washes are carried out on affected lambs (figure 4 - see top right-hand side). In Great Britain in 2008, 175 incidents of nematodirosis were reported in the second quarter of the year, a figure significantly greater than that recorded by VIDA over the same period in 2007.  In Scotland alone, 97 outbreaks were recorded in May and June 2008, compared to 43 over the same period in 2007. 

The benzimidazole class of anthelmintic (Group1) is regarded as the drug of choice in cases of nematodirosis. This is due to the wide safety margin in younger lambs and the lack of recognised resistance to these drugs in N. battus.   However, resistance to the benzimidazoles is becoming increasingly common amongst other nematode intestinal parasites of sheep.  SAC VS consider this can be significant since N. battus may be seen in mixed parasite infections, particularly in older lambs. In these cases of mixed infection it may be advisable to check anthelmintic efficacy by submitting faecal samples for worm egg counts 10 to 14 days post-treatment. 

Generalised and systemic conditions

A mule ewe submitted to Edinburgh was submitted from a unit where both ovine pulmonary adenocarcinoma (OPA) and chronic fasciolosis were identified in the last month.  However on this occasion there was acute udder congestion and gas infiltration of the uterine mucosa. Both the foetus and placenta appeared grossly normal.  Clostridium sordellii was isolated from the udder, uterus and spleen. SAC VS decided that the culture results and gross lesions, combined with subsequent histopathology findings, were sufficient to make a diagnosis of malignant oedema due to C. sordellii infection.  Similar outbreaks have been reported affecting ewes at parturition, with bloody discharge and swelling of the pelvic tissues and perineal area reported, followed by toxaemia and death.

Alimentary tract disorders

Low numbers of cryptosporidia were the only enteropathogen detected in a ten-day-old Texel cross lamb submitted to Aberdeen for postmortem examination with a short clinical history of scour.  Six other deaths were reported. The diagnosis was confirmed following the sampling of other live affected lambs, when moderate numbers of cryptosporidia were detected.

Respiratory tract conditions

Three ewes and three hoggs were submitted from a Perthshire flock experiencing a high prevalence of ill thrift and respiratory signs.  Necropsy revealed remarkably similar findings in all six cases. An extensive grey coloured consolidation of the lungs with a marked anteroventral pattern was present.  In several cases the affected lung was adherent to the chest wall via fibrous tags and the lesions accounted for up to 60 percent of the total lung volume.   Lung tissues from all six sheep were examined histologically when ovine pulmonary adenocarcinoma (OPA) was confirmed.  It is unusual to see such extensive and severe OPA in both ewes and hoggs, and this case is being investigated further.

Reproductive tract conditions

Abortion due to Chlamydophila abortus (enzootic abortion of ewes) was diagnosed in 38 Scottish flocks this month.   Abortion due to Yersinia enterocolitica, a cause of sporadic abortion, was diagnosed on a farm on which three Scottish mule ewes aborted over a period of three days, approximately two weeks prior to lambing.  Foetopathy due to Streptococcus dysgalactiae was diagnosed in another flock approximately two weeks before lambing.  Toxoplasmosis was diagnosed in a flock where six of 30 purchased hoggs aborted over a short period.

Multiple abortions with and without ewe deaths were reported in a group of 117 cross-bred gimmers approximately two weeks before lambing.  These animals were all from the same field, which received its water supply from a stream, in contrast to the mains supply to other fields.  Multiple abortions occurred in this field last year due to Pasteurella multocida.  However, this year Salmonella Montevideo was isolated from the placenta of retained autolytic foetuses on postmortem examination of a gimmer that died while trying to abort, and from two further sets of aborted foetuses.   Salmonella Montevideo was also isolated from two aborted Scottish blackface lambs from another farm that had suffered eight abortions in the past two weeks.  The associated placenta was grossly inflamed with a thick surface exudate, but no acid-fast organisms suggestive of Chlamydophila abortus were seen in MZN smears.

Bacillus licheniformis was isolated in pure culture from the stomach contents of an aborted foetus.  A severe fibrinous pleurisy and peritonitis were seen at necropsy (figure 5 - see top right-hand side).

Nervous system disorders

Louping-ill was diagnosed in a Cheviot ewe found dead on an Argyllshire farm, on which several ewes presented with nervous signs varying from mild trembling of the head to ataxia.  Affected hill ewes were known to be grazing tick-infested pasture.