Veterinary Services

Metabolic disease in ewes and neonatal lamb deaths associated with inadequate colostral antibody intakes were confirmed. Pregnancy toxaemia was diagnosed at Dumfries when blood samples were received from two ewes described as wandering aimlessly.  Serum beta-hydroxybutyrate (BOHB) was measured at 4.8 and 3.0 mmol/l (reference range of <1.2 mmol/l).  On a different farm many of the leaner ewes were reported to be pushing at the pen sides and twitching their heads.  Following the necropsy of one ewe periportal fatty change was found in the liver and brain histopathology indicated a possible hepatic encephalopathy.  Despite these significant pathological findings, the elevation in serum BHOB was relatively modest at 2.0 mmol/l.

A large crossbred flock in Aberdeenshire consisting solely of gimmers (two-year-old ewes) reported the deaths of 50 to 60 neonatal lambs.  Examination of five lambs found that the most significant problems were hypogammaglobulinaemia and starvation, with no evidence of infectious disease. The problem was probably exacerbated by poor forage quality, as some sick and downer gimmers were also reported.

Two neonatal lambs were submitted from a farm where large numbers of deaths were recorded in this age group.  Both were small for Texel cross lambs, weighing only 2.3 and 2.1kg.  The brown fat around the heart and kidneys had been metabolised and there was no milk in the abomasum or intestines.  Starvation and hypothermia were diagnosed.

Generalised and systemic conditions

A comparison was made of the diagnoses reached from postmortem examinations of lambs less than four months old at the eight SAC Disease Surveillance Centres (DSCs) during the first four months of 2007 and 2008 (figures 2 and 3). In 2008, colisepticaemia, at times combined with hypogammaglobulinaemia, and Mannheimia haemolytica pneumonia were the most frequent causes of death. Clostridial diseases and coccidiosis were also diagnosed in a significant proportion of the 177 lamb carcases examined. In contrast, systemic pasteurellosis and mannheimiosis, clostridial disease and Streptococcus dysgalactiae polyarthritis were all more common diagnoses during 2007. Cryptosporidiosis and Fusobacterium necrophorum infections, both of which were identified as causes of death this year, were not recorded last spring.   

Septicaemia following a skin infection introduced with orf vaccination was believed to have caused the death of a two-day-old Scottish blackface lamb submitted to Edinburgh.  Streptococcus dysgalactiae was isolated on culture of tissues from the lamb, including an area of marked cellulitis in the hind leg. 

A three-day-old lamb was submitted to Perth after being found dead.   Lesions recorded at necropsy suggested a septicaemic condition and E.coli was isolated from a range of viscera.  A zinc sulphate turbidity test carried out on serum gave a result of three units.  Test results of less than five units are associated with a complete failure of passive transfer of immunity due to an insufficient intake of colostrum.              

Alimentary tract disorders

Dumfries diagnosed Johne’s disease on the basis of a positive ZN-stained smear from a faeces sample submitted from a goat.  The condition was also diagnosed at necropsy in a three-year-old Shetland ewe that lost weight before death.  The faeces were pelleted and there was no obvious pigmentation or thickening of the intestines.  However, the serosa separated from the mucosa as the intestines were washed out for a total worm count.  This finding is often a feature of Johne’s disease cases and the subsequent ZN-stained smear identified acid-fast bacilli, confirming this diagnosis. 

Six ewes were found dead on a farm in Sutherland in the course of a month, following administration of a trace element drench and flukicide.  Chronic inflammation of retropharyngeal and oral tissues with periostitis and osteomyelitis of the hyoid and the right mandible was noted on necropsy of one of these ewes. A profuse mixed growth of anaerobes, including Fusobacterium necrophorum, was isolated on culture of the affected tissues.  A dosing gun injury was suspected as the underlying cause of the pathology in this case.

Seven incidents of lamb dysentery were diagnosed by SAC in April, all in lambs less than one-week-old.  There were six incidents in April 2007. 

A one-week-old lamb was submitted to Perth after being found dead.  It showed signs of dehydration and had a bloated abdomen.  The abomasum was grossly distended and showed marked mucosal thickening and emphysema.  A zinc sulphate turbidity test carried out on serum gave a result of two units and consistent with an insufficient intake of colostrum.  Subsequent culture of the affected areas of abomasum produced a pure growth of Clostridium sordellii

Respiratory tract conditions

Pneumonia due to Mannheimia haemolytica was diagnosed in a year-old Scottish blackface hogg from a group of 750 in which 35 deaths had been reported.  This group was purchased to run on tick-affected ground and the hoggs were reported to have been in poor condition when they arrived on the premises.

A live five-year-old Scottish blackface ewe submitted for necropsy showed signs of profound weakness, tachypnoea and increased lung sounds, particularly on the right side.  At necropsy the right lung was enlarged compared to the left and was composed almost entirely of neoplastic tissues, while in the left lung the areas of neoplasia were confined to the cardiac lobe.  Little fluid was present in the airways, although it was reported that the sheep had earlier been positive on the”wheelbarrow” test.  The diagnosis of ovine pulmonary adenocarcinoma (OPA) was confirmed by histopathology.  This was the first case to be diagnosed on the farm, where unexplained weight loss in the ewes was assumed to be due to Johne’s disease.

Reproductive tract conditions

Two foetuses were received at Dumfries from a flock that had experienced abortion two to three weeks pre-lambing during the previous three years.  Only housed ewes were affected and aborting ewes often died 24-48 hours later.  This spring four ewes had aborted and three had died before samples were submitted.  The foetuses were autolysed and pure growths of E. coli were cultured from the foetal stomach contents of both.  These isolates were typed as 0149 and 0174.   The E. coli 0174 isolate was verotoxin positive.  Verotoxin positive E. coli 015 was previously reported as a cause of abortion in sheep and 0174 was probably also significant in this case.  Infection may have been spread by carrier ewes or could have been present in the building which had previously been used for calves.  The SAC VS advised that the building should be thoroughly cleaned and disinfected and that verotoxin positive strains of E. coli can cause severe zoonotic disease.

The local Animal Health Office was informed when Salmonella Arizona was isolated from aborted twin foetuses from a farm in Ross-shire.  Abortion due to Arcanobacterium pluranimalium was identified as the cause of abortion in another submission from Ross-shire.  A full review of the abortions in Scotland will be published in the next report.

Musculoskeletal conditions

Septic polyarthritis due to infection with Streptococcus dysgalactiae was confirmed in three live lambs submitted to Aberdeen from a 475-ewe flock. In the preceding week, lameness progressing to recumbency had affected seven lambs. All the submitted lambs had evidence of adequate colostral antibody absorption but had multiple infected joints.

At Dumfries two housed lambs were necropsied after failing to respond to treatment for joint ill.   In each case the carpal joints were swollen and filled with pus (figure 4) from which S. dysgalactiae was isolated. 

Skin diseases

Chorioptes spp mites were observed in a skin sample submitted to Aberdeen from a merino sheep with non-pruritic dried serous scabs affecting the lower limbs.

Samples of scab were collected from a flock where 40 per cent of the ewes had crusty lesions at the base of their teats.  Orf virus was detected by PCR.