Veterinary Services

Two Limousin cross calves aged one to two days were euthanased and submitted to Ayr for postmortem examination. Both calves were unable to rise and displayed nervous signs including nystagmus and head tremors. Another two calves on the farm showed similar signs.  The herd was vaccinated against bovine viral diarrhoea virus (BVDV) but the BVDV vaccine course for the heifers was not completed prior to service. Three of the four affected calves were from heifers. At necropsy of both calves  cerebellar hypoplasia was evident (Fig 1 - see top right-hand side) and the cerebral tissue of both hemispheres was replaced by fluid filled cavities (Fig 2 - see top right-hand side). Gross examination of the brain from one calf identified severe hypoplasia of the cerebellum, a bifid septum lucidum and rarefaction of the occipital cortex. Histological examination confirmed the gross findings and showed a paucity of myelin throughout the cerebral cortex and several porencephalic lesions. Only a small amount of cerebellar tissue was present and the Purkinje cells were either absent or disorganised. Two large glial foci were present in the deformed cerebellum. Glial foci are typically associated with protozoal infections but immunohistochemistry failed to confirm the presence of Neospora antigen. Gross examination of the second brain showed abiotrophy of the cerebellum, paucity of myelin and some porencephaly. These findings and the majority of findings in the first brain suggested pestivirus infection. However, screening for BVDV and border disease virus by PCR proved negative. Immunohistochemistry of both brains also proved negative for pestivirus. Cerebellar hypoplasia was also confirmed by Inverness in a four-day-old suckled calf showing neurological signs. Again screening for BVDV by PCR and immunohistochemistry proved negative despite neurohistopathology, again suggesting exposure to a pestivirus. In this case the dam was in contact with a calf persistently infected with BVDV. In both outbreaks described above, serum collected at postmortem examination was positive for BVDV antibody, although this could be due to maternally derived antibody. Neuropathologists at Moredun Research Institute consider that the lesions could have arisen as the calves were becoming immunocompetent and therefore the calves did not become persistently viraemic. Further investigation is proceeding.

Generalised and systemic conditions

A Simmental heifer was submitted to Perth for postmortem examination following on-farm euthanasia. It was the third in the group to show signs of malaise, recumbency and paralysis. The farm of origin has a large poultry enterprise. Necropsy revealed haemorrhagic abomasal contents and dark fluid intestinal contents. No other abnormalities were noted.  Pooled intestinal contents for Clostridium botulinum toxin was positive for type C toxin and consistent with a diagnosis of botulism.   

Further cases of bovine neonatal pancytopenia were diagnosed across Scotland.  A typical case in a two-week-old calf was submitted to Thurso. Gross findings included petechiae on the subcutaneous tissues, abomasal mucosa and serosal surface of the rumen and extensive haemorrhage into the lumen of the gut. Bone marrow histopathology confirmed the diagnosis.

Alimentary tract disorders

Salmonellosis was diagnosed in a three-week-old, Simmental cross bull calf submitted to Edinburgh for necropsy as a suspected case of bovine neonatal pancytopenia.  It became ill eight days previously with pyrexia, bleeding from inside the ears and melaena.  Examination of a blood sample taken at that time confirmed adequate platelets and red blood cells, but identified as marked neutropenia. Antibiotic treatment reduced the pyrexia but the calf then deteriorated rapidly and died.  At necropsy the calf was well grown and in good bodily condition.  The tip of the caecum was necrotic and attached to the abdominal wall by dry, inspissated fibrin. Associated loops of jejunum were congested with mucosal necrosis and diphtheresis.  There was no evidence of significant haemorrhage.  Salmonella Dublin was isolated from abdominal fluid and spleen.  No BVDV was detected in the spleen.  Histology of the bone marrow revealed that it was hyperplastic with all cell lines represented but there were scattered clumps of bacteria and foci of necrosis.  Salmonellosis explained the melaena and death but no cause for the aural haemorrhage was determined.

Abomasal ulceration and exsanguination were found to be the cause of death in a three-year-old dairy cow submitted to Ayr.  The cow appeared unwell for a week and was bloated prior to death. Necropsy revealed pallor of the mucous membranes and melaena. The spleen was enlarged and the liver showed multiple fluke tracts with biliary thickening and adult flukes present. There was blood in the reticulum and large blood clots in the abomasum. Clotted and free blood was present in the small intestine and caecal contents were black.  A single deep circular ulcer was evident around the blood vessels in the pylorus.  Histopathology revealed a severe subacute fibrino-necrotising and suppurative abomasitis. No fungal elements were seen but moderate numbers of variably Gram positive bacilli were evident at the deep margins of the inflammatory infiltrate suggesting clostridial organisms may have contributed to the development of the lesion.

Respiratory tract conditions

The lungs from a ten-month-old beef heifer were submitted to Perth as part of an investigation into a pneumonia outbreak. The lungs were heavy and oedematous. Dissection of the lung parenchyma revealed multiple interlobular bullae present in the dorsal region. Froth was present within the airways with acutely congested mucosal surfaces. Fluorescent antibody testing (FAT) was positive for both bovine herpesvirus 1 (BHV1) and respiratory syncitial virus (RSV). Mycoplasma bovis was also recovered from affected tissue.

A seven-month-old Holstein bull was submitted to Dumfries after dying with signs of a  respiratory disease.  Necropsy revealed a necrotic tracheitis, anteroventral consolidation of the lungs with emphysema and interlobular oedema. The FAT for BHV1 was positive and again M. bovis was recovered.  Recently bought fattening animals were housed with older cattle and were suspected to have introduced the problem. 

A four-year-old Jersey cow lost condition over a four month period.  After turn out the animal  was noted to be breathless and was found dead the following morning.  Necropsy revealed a large abscess between the liver and diaphragm which appeared to occlude the caudal vena cava. Fusobacterium necrophorum was isolated from the abscess.  A large amount of fresh blood was found in the rumen and a blood clot six centimetres in diameter was identified in the right diaphragmatic lung lobe (Fig 3 - see top right-hand side) allowing a diagnosis of pulmonary thromboembolism and fatal haemorrhage to be made.