Veterinary Services

Comparative figures for the diagnoses of Pneumonic Pasteurellosis due to Mannheimia haemolytica and systemic Pasteurellosis due to either Pasteurella trehalosi or Mannheimia haemolytica between 1993 and 2005 are shown in figure 1 (click on PDF link on right). This shows a significant rise in the number of cases of systemic Pasteurellosis in 2004 and 2005 to approximately twice that of the mean for 1993-2003. The number of diagnosed outbreaks reached a peak of 52 in November 2005. Mortality rates of between 1% and 30% were recorded for affected farms.

Toxic conditions

Four deaths were reported to have occurred during the last week of lambing on an Aberdeenshire unit, leading to the private veterinary surgeon performing an on-farm necropsy. The carcass of the four-years-old Texel cross ewe was reported to be severely jaundiced, with adult flukes present within the liver, and black kidneys. The copper concentration in submitted portions of liver was 21,900 umol/kg dry matter (normal range 314-7850 umol/kg). As this level is equivalent to a copper concentration of 348 mg/kg wet weight in the liver, it did not exceed the threshold of 500 mg/kg wet weight at which there is a requirement to notify the Food Standards Agency of a potential food safety incident.

The carcass of a ewe was submitted to the Dumfries DSC for necropsy, as part of an investigation into a suspected abortion problem in a group being fed silage and a proprietary sheep cake. This was the second death amongst the lambing ewes, with both animals reported to be found with a bloody discharge immediately behind the carcass. The submitted ewe was jaundiced and had a pale liver, dark red kidneys and brown urine. A partially eroded trace element bolus was present in the reticulum. Subsequent tissue testing indicated that the liver copper level was 26,900 umol/kg dry weight and kidney copper 7,490 umol/kg (normal range <787 umol/kg). The farm had previously recorded an outbreak of copper poisoning, associated with feeding cattle cake.

Evidence of copper poisoning was also identified at the Edinburgh Centre, in a one-year-old North Ronaldsay ewe hogg. Serum copper in this animal was found to be 40.9 umol/l (normal range 9.0 – 20.0 umol/l). No history was provided to explain this finding, although the North Ronaldsay breed is known to be particularly susceptible to copper toxicity.

Parasitic diseases

Parasitic gastroenteritis was confirmed in a group of 60 Suffolk-cross lambs, reported to be underweight with watery diarrhoea. The group had last been treated with levamisole and triclabendazole in October. Trichostrongyle worm egg counts of 1,450, 3,400 and 2,850 eggs per gram of faeces, were recorded in samples submitted from three affected lambs.

Lungworm infection was confirmed in a nine-month-old lamb submitted to the Aberdeen DSC with a history of coughing. Examination of the lungs from the animal confirmed the presence of Dictyocaulus species lungworms in the terminal bronchioles. A total of 50 lambs from the same housed group of 300 were also reported to be coughing and pyrexic.

Generalised and systemic conditions

A Poll Dorset ewe that had previously been used as a donor for embryo transfer was submitted to the Edinburgh Centre for necropsy, with a history of chronic ill thrift. Internally there were fibrous adhesions between the abomasum and body wall. Further adhesions ran between the right horn of uterus and the body wall, with associated caseous purulent cores. This focal peritonitis was deemed to be due to previous laparoscopic procedures. However there was additional evidence of a dramatic fibrinous pleurisy and suppurative pneumonia, with Dictyocaulus lungworms present in small airways.

Alimentary tract disorders

Five Scottish Blackface barren ewes from two farms were submitted to the Dumfries Centre with a history of ill thrift. Body weights ranged from 26 to 38kg, and in all cases a marked thickening of the lower small intestine was seen on necropsy. In two cases Zeihl Neelson-stained smears of the ileum were positive for clumps of acid-fast organisms, confirming a diagnosis of Johne's disease. Fixed samples of intestine from the remaining three ewes were then submitted for histopathology to assess the likelihood of paucibacillary Johne's disease. However, results from this examination were consistent with pathology due to chronic parasitism.

The Thurso Centre reported a diagnosis of Johne's disease in a four-year-old Cheviot ewe, the twentieth case to occur over the past two years in a flock of 1,100. Analysis of breeding records on the affected farm has indicated that in many diagnosed cases the affected sheep were genetically related - consistent with transmission of infection from dam to offspring in utero or via faeces.

Respiratory tract conditions

A ten-month-old ewe lamb was submitted to the Edinburgh Centre with a history of dyspnoea and of hanging back from the rest of the group. Body condition was poor and the right side of the thorax was found to contain a turbid serosanguinous fluid. Both lungs were consolidated and hepatized, with adhesions running between the pericardial sac and parietal pleura. Lung cultures yielded a growth of a Pasteurella species and Mycoplasma ovipneumoniae. Histopathology confirmed the presence of type II pneumocyte proliferation, typical of ovine pulmonary adenocarcinoma (OPA, Jaagsiekte) with secondary bacterial and mycoplasma-type pneumonia.

Reproductive tract conditions

Streptococcus dysgalactiae was cultured from the stomach contents and placenta of an aborted foetus from a Borders flock. Several abortions and stillbirths had occurred at approximately two weeks before term.

The owner of a ewe flock reported losing lambs within the first 24 hours of life. The flock was reported to be vaccinated against both Enzootic abortion and toxoplasmosis. Although there had been no abortions or stillbirths, there was frequently a difference in size between twins and many lambs were said to lack vigour. When a typical case was submitted for necropsy no significant gross lesions were noted. However, subsequent histopathology of the brain confirmed lesions consistent with a diagnosis of toxoplasmosis.

Toxoplasmosis was also diagnosed following the submission of three sets of foetuses and placentae from a single farm. This case also involved a vaccinated flock, with the shepherd reporting 80 abortions, stillbirths and non-viable lambs. The abortions occurred mainly amongst gimmers that were vaccinated nine months earlier. Diagnosis was confirmed on the basis of foetal serology and histopathology, while maternal serology indicated high positive titres to Toxoplasma gondii, suggestive of recent natural infection. No other infectious causes of abortion have been identified in this full investigation. The possibility of vaccine failure is now being examined. This will include the storage and handling of the vaccine and the possibility that concurrent immuno-suppression may have had an influence in the lack of vaccine efficacy.

A Cheviot gimmer died suddenly in a flock in Inverness-shire, some two months prior to lambing. On necropsy the uterine wall was found to be thickened, oedematous and emphysematous. The organ was so friable that the right uterine horn had ruptured leading to an associated peritonitis, with foul-smelling pink coloured turbid peritoneal fluid and fibrin tagging. A growth of E. coli and Clostridium septicum was isolated from the uterus.

Nervous system disorders

A Scottish Blackface ewe was submitted alive to the Edinburgh Centre with a history of a slight head tremor. The carcass was jaundiced with a mild suppurative bronchopneumonia. However, brain histopathology revealed a mild non-suppurative meningoencephalitis with a meront, typical of Sarcocystis species, present in the midbrain. A further three, seven-months-old ram lambs from the same farm subsequently presented as either sudden deaths or with a progressive recumbency. In these cases histopathology identified a severe widespread non-suppurative meningoencephalitis, with merozoite-like forms present within the cerebral cortex. Protozoal tissue cysts were also seen in large numbers in skeletal and cardiac muscle. Specialised staining suggested sarcocystiosis is the most likely cause, however tissue has been sent to the USA for electron microscopy to confirm the diagnosis. The farm of origin is known to have a large fox population, which may have a role in the epidemiology of this unusual case.