Veterinary Services

Nutritional and metabolic disorders

A Berwickshire flock of 600 Scottish Mule ewes suffered ten deaths during the penultimate week before lambing. The clinical history was of depression, recumbency and death, and since silage was being fed the owner feared listeriosis might be responsible.

When one carcass was submitted for examination the condition score was estimated to be 1.5 and necropsy revealed a grossly enlarged and pale liver. Subsequent histopathology confirmed dramatic periportal fatty change, typical of pregnancy toxaemia.

The same diagnosis was made on some 23 other occasions this month, usually on the basis of betahydroxybutyrate (BOHB) analysis of submitted blood samples. This was the case when staff at the Edinburgh Centre investigated a lowland flock, in which ewes showed clinical signs of pregnancy toxaemia despite body condition scores being an acceptable 2.5-3.0. The aetiology in this case was felt to reflect the excess condition carried by many ewes during early pregnancy and the poor energy content of the diet currently fed. Calculations based upon the metabolisable energy (ME) of the feed and the likely late pregnancy consumption of silage, confirmed that it could not meet the ewes’ energy requirements and an additional concentrate feed was recommended.

Hypocalcaemia was diagnosed in a moribund ewe submitted for post mortem examination at the Perth Centre. The serum calcium level was found to be 0.9 mmol/l (reference range 2.0-3.0 mmol/l), while serum magnesium, inorganic phosphate and BOHB were within reference ranges. Ten older ewes from this flock were reported to have become ataxic and recumbent, three of which subsequently died.

Parasitic diseases

Two Scottish Greyface ewes were submitted to the St Boswells Centre after dying a month before lambing. Both animals had a body condition score of no more that 1.0, with one ewe carrying twins and the other triplets. Abomasal worm burdens of 4,500 and 5,500 Haemonchus contortus adults and larvae were evident, while one of the ewes showing mucoid ileitis, also had 9,700 adult and larval Trichostrongylus spp, No evidence of any other disease process was apparent. When a triplet-bearing ewe was submitted to the Centre from another local flock suffering from ewe deaths, a total of 7,600 adult and larval H.contortus worms were recovered from the abomasum. In each of these cases the burden of worms was considered to be significant, with the demands of multiple foetuses and the possibility of poor nutrition thought to have accentuated the effect of the nematodes.

Sub-acute fasciolosis was diagnosed in a small pedigree Border Leicester flock in the Edinburgh area, in which a number of ewes had died around the time of parturition. The owner reported that affected ewes were not seen to be lambing, but were subsequently found dead with a fresh foetus in the birth canal. Following necropsy of a typical case in which fasciolosis and pregnancy toxaemia were confirmed, it was suggested that some ewes were unable to endure protracted parturition. Along with treatment for fluke, the urgent blood sampling of ewes bearing multiple lambs was recommended to assess the risk of pregnancy toxaemia. Chronic fasciolosis was also diagnosed in a two-year-old Scottish Mule ewe from a Fife farm, one of ten that had become recumbent in the later stages of pregnancy. This flock of 350 had received no treatment for fluke over the autumn or winter.

Alimentary tract disorders

Two, four-week-old Lacaune lambs were submitted from a dairy flock. On this unit near Edinburgh lambs are artificially reared on machine-fed milk replacer from 12 hours of age, before creep feed and water are introduced. It was reported that two lambs were dying each day from a group of 750, with the majority being recorded as sudden deaths. Both lambs submitted had crusty lesions around the prepuce and anus. Internally one showed signs of intestinal haemorrhage syndrome or "red gut", while in the other the upper gut contained only digested creep feed and the large intestine was distended with fluid and gas. These findings suggested that a proportion of lambs were taking little or no milk replacer, and that the early consumption of large quantities of creep feed by some had led to an acute digestive disturbance. Chronic bacterial dermatitis, possibly with underlying orf infection, was diagnosed as the cause of the crusty skin lesions noted.

A six-year-old Scottish Blackface ewe was submitted for necropsy following a poor response to therapy for suspected pregnancy toxaemia. On post mortem examination there was evidence of fibrinous pleurisy and sub-acute fasciolosis. In addition there was an area of mucosal thickening and an annular stricture, partially occluding the lumen of the ileum. Neoplasia was suspected and histopathology confirmed the lesion as an intestinal adenocarcinoma.

A three-week-old lamb with a history of chronic intermittent pyrexia of unknown origin was submitted to the Aberdeen Centre. There was evidence of a mild scour, and necropsy revealed an organising haematoma in the liver, presumed to be of traumatic origin. Subsequent histopathology identified cellular inclusion bodies within the caecal mucosa and kidney. These were suggestive of adenovirus infection, a recognised cause of enteritis and interstitial nephritis in lambs.

Reproductive tract conditions

During March infection by Chlamydophila abortus, enzootic abortion of ewes (EAE) remained the most common diagnosis in cases of ovine abortion, being recorded on 50 separate occasions during the month. Amongst these diagnoses was an outbreak on an Aberdeenshire unit, involving ewes purchased in October 2004 from a flock that was accredited EAE free. Diagnosis was confirmed following the identification of typical acid-fast organisms on smears from placentae supported by positive serology in several aborted ewes. Investigations to ascertain the source of the infection are ongoing, although this is most likely to have been acquired after the purchased ewes left the accredited holding.

The abortion suffered by a ewe was initially thought to be associated with EAE on the basis of placental lesions recorded at necropsy. However, modified Ziehl Neelsen (MZN) stained smears proved negative for acidfast organisms and subsequent bacterial culture on selective media yielded Yersinia pseudotuberculosis. Bacterial placentitis associated with Gram negative coccobacilli was duly confirmed on histopathology.

Bacterial abortion associated with E. coli infection was identified in a 500 ewe commercial flock near Edinburgh. The organism was isolated in pure profuse growth from the stomach contents of freshly aborted foetuses and histopathology confirmed suppurative placentitis with fine Gram negative bacilli, consistent with E. coli. No other infectious cause of abortion was identified. This organism was also recovered from the first abortion in a flock of Cheviots in Ross-shire.

In an outbreak recorded at the Thurso Centre, Salmonella montevideo was isolated from a flock in which 75 out of 600 ewes aborted over a three week period. The infection was first diagnosed in sheep kept outside, before spreading to housed animals. The first abortion to occur in a group of 200 Swaledale ewes from a flock in Inverness-shire was associated with infection with Salmonella arizona. The group was due to start lambing in one week.

Twin foetuses were submitted from the first abortion to occur amongst a group of sixty Suffolk-cross ewes on an Inverness-shire unit. Campylobacter sputorum subspecies bubulus was isolated as a profuse growth from the foetal stomach contents and placenta. This organism is commonly isolated from sheath washes in bulls but is usually considered to be non-pathogenic.

Musculo-Skeletal conditions

A shepherd from a Selkirkshire farm reported lameness and swollen joints amongst his 700 Texel cross lambs. Affected lambs were aged between two and four weeks and overall prevalence was around 9%. When two affected lambs were sacrificed for post mortem examination one was found to have a chronically enlarged and purulent hock joint. In the other lamb the hocks and stifle joints were affected. A pure growth of Streptococcus dysgalactiae subspecies dysgalactiae was isolated from the affected joints. An atlanto-occipital joint infection associated with the same organism was confirmed in a three-week-old lamb from an Aberdeenshire unit. This lamb had shown ataxia of approximately four days duration and three other lambs were similarly affected. On another premises near Inverness Streptococcus dysgalactiae subspecies equisimilis was isolated from the hock joint of a three-week-old lamb from a housed Texel flock. Five lambs had been similarly affected with joint ill, despite treatment of navels and care with environmental hygiene.

Renal diseases

A young Texel ram from a flock in Morayshire was found to have died following urethral obstruction, secondary to posthitis. A profuse purulent discharge from the prepuce was evident, from which Corynebacterium pilosum and a Corynebacterium renale-like organism were identified on bacterial culture. Another ram from the same flock had scabby lesions at the preputial orifice, from which the same organisms were isolated. Two other animals from the group of 25 were reported to be similarly affected.