Veterinary Services

Generalised and systemic conditions

The seasonal increase in the number of navel ill cases diagnosed associated with the start of the spring suckler calving period was noted. In a typical case, the second of two neonatal calves to die was submitted to Dumfries for necropsy. The two-day–old Charolais calf had not passed any faeces. The navel was enlarged and there was a generalised peritonitis with fibrin tags on the abdominal viscera. This had resulted in loops of intestine becoming fused together which would have interfered with gut motility.

In another case suppurative meningoencephalitis was diagnosed in an 11-day-old Highland heifer calf that died following a history of recumbency and panting. Postmortem examination revealed an inflamed navel and enlarged lymph nodes. Polyarthritis was noted, as were multiple subdural haemorrhages and severe congestion of the meningeal vessels. Escherichia coli was recovered in septicaemic distribution and from joint and meningeal swabs.

Tissues from a six-month-old Simmental-cross calf were submitted to Ayr for histopathology. This calf was ill-thriven and was noted kicking at its abdomen. It was pyrexic, auscultation of the right thorax suggested fluid was present and the superficial lymph nodes were grossly enlarged. It became recumbent and appeared to have neurological deficits of the hind limbs. An onfarm postmortem confirmed that the internal lymph nodes were also enlarged and the kidneys were very firm with thick capsules. Histopathology confirmed multicentric lymphoma with involvement of the liver and kidney. The clinical history suggested that infiltration of the spinal cord may also have occurred.

Parasitic diseases

Fasciolosis was a common diagnosis with 49 confirmed cases during the month. Four of the dairy cows submitted to Ayr for postmortem examination that showed signs of fluke damage also had low calcium levels detected by analysis of vitreous humour. Johne’s disease was confirmed in another two cows with extensive liver damage due to Fasciola hepatica.

Alimentary tract disorders

K99 positive E coli was detected in a faeces sample from a two-day-old scouring calf from an Aberdeenshire unit. Colisepticaemia due to infection with K99 positive E coli had previously been confirmed in neonatal lambs on this unit.

A faecal sample was received by Dumfries from a three-year-old Holstein cow that developed a watery scour one week after undergoing a caesarean section. Salmonella Typhimurium was isolated. Three weeks later a five-day–old calf was submitted for postmortem from the same farm. The calf was born in the box where the sick cow had been housed and had not thrived since birth. At necropsy the mesenteric lymph nodes were massively enlarged and there was necrosis of the intestinal mucosa affecting the distal jejunum, ileum and colon with liquid faeces (figure 1 - see top right-hand side). Salmonella Typhimurium was also isolated from this case. The SAC advised that the box was thoroughly cleaned and disinfected. Previously it was only cleaned out with no disinfection.

Respiratory tract diseases

Chronic active broncho-interstitial pneumonia was confirmed in a five-month-old suckled calf from an Aberdeenshire unit. Initially it responded to treatment for pneumonia but then collapsed and died. The unit reported an ongoing problem in autumn born calves. Although Mycoplasma bovis was isolated the SAC considered that the primary aetiological agent was probably viral. Bovine virus diarrhoea (BVD) virus was detected in a blood sample from the calf and persistent viraemia was suspected.

Reproductive tract conditions

SAC Veterinary Services examined 713 foetuses during 2007 and the diagnostic rate was 47 per cent based on established diagnostic criteria. The confirmed bovine abortion diagnoses as a percentage of foetuses received are shown in figure 2 (see top right-hand side).

The main causes of loss were to Bacillus licheniformis and dystokia. Every year Bacillus licheniformis is a consistent cause of fetal loss. Feed, mainly forage, contaminated with this bacterium is assumed to be the main reservoir of infection. The importance of feeding high quality forage, particularly to late pregnant cows has to be emphasised to producers. Many submissions were of stillborn calves at or near term and this is reflected in the high percentage of dystokia diagnoses with no evidence of infectious disease. Control through the management of cow body condition score and the use of "calving ease" estimated breeding values for bulls is important.

Blood samples were submitted from an Ayrshire suckler unit to investigate a high barren rate among cows. All eight cows sampled were seropositive for bovine herpes virus type 1 (BHV1). The heifers on this farm had shown good conception rates. Clinical signs of infectious bovine rhinotracheitis became apparent when the barren cows joined the group of heifers. Three heifers died and eight aborted. Two aborted foetuses were submitted along with maternal sera for serology. Both dams were seropositive for BHV1 and histopathology of one foetus showed hepatic necrosis and myocardial damage consistent with infection with BHV1.

Nervous system disorders

An 18-month-old, Blonde D’Aquitaine bull submitted for necropsy had a history of nervous signs followed by acute onset recumbency, abdominal pain and death. Necropsy revealed a large, thick walled cavity in the thorax full of altered blood. It was attached to the sternum and diaphragm and appeared to involve adhesions to the accessory lobe of the lung that was necrotic, fibrosed and collapsed. A clot of blood and pus was present in the trachea along with much stable foam. The abomasum contained a large amount of altered blood that extended anteriorly along the oesophageal groove and into the proximal duodenum. Arcanobacterium pyogenes was isolated from the brain and from the thoracic mass. Histopathlogy revealed that the thoracic mass was composed of lung and fibrous tissue and inflammation and haemorrhage within the rest of the lung. The haemorrhage into the lung and lack of an alimentary source for the haemorrhage suggested that the abomasal blood originated in the lung mass and was coughed up and swallowed. Being protein it remained in the oesophageal groove and bypassed the rumen. Neurohistopathology was carried out because while the findings were sufficient to explain death, they were not entirely consistent with the history. This revealed severe, suppurative meningoencephalitis that was possibly secondary to the necrotic, inflamed mass in the thorax or was possibly unrelated.

A nine-year-old dairy cow was submitted to Ayr with a history of staggering, then recumbency leading to death approximately 36 hours later. Haemothorax was present with extensive unilateral pulmonary haemorrhage, pleurisy and necrosis of the diaphragmatic muscle. Malignant oedema type lesions were evident in the overlying thoracic musculature and intercostal muscles. Neurohistopathology was conducted after BSE screening proved negative. This showed scattered neutrophils within the brainstem and thick cuffing of the vasculature. These findings are consistent with a diagnosis of listeriosis. The SAC postulated that listeriosis caused the nervous signs noted and that perhaps trauma to the thorax occurred because the cow was in-coordinated.

Nervous signs were also reported in two Charolais bullocks being fed poor quality silage. One apparently responded well to marbofloxacin; however, another showed no improvement and was euthanased. A postmortem examination was performed and under UV light, fluorescence of the cut surface of the brain was noted. Neurohistopathology confirmed severe and extensive cerebrocortical necrosis (CCN).

An organic dairy farm in Dumfries and Galloway in which 20 per cent of the cows had developed sores on their teats over the previous three months was visited. Two different conditions were observed. Twenty cows were affected with raised scabs on the body of the teat (figure 3 - see top right-hand side). These scabs developed over a few days and usually involved multiple teats. They were not painful and did not interfere with milking. They healed over the following 2-3 weeks. Samples of scabs from these lesions were positive for pseudocowpox on electron microscopy. Six cows introduced to the herd two months before the first case were a possible source of the problem although the incubation is generally short at around one week. The second condition was more serious and affected ten cows. Deep ulcerated lesions affected the whole of the teat end. These were painful causing the cows to resent being milked and a secondary mastitis developed in several cases. Two cows had to be culled. These lesions appeared to be acute in onset and affected only a single teat. Staphylococcus aureus and Arcanobacterium pyogenes were isolated from swabs. Serology for bovine herpes mammillitis was negative as were tests for pseudocowpox. A diagnosis of blackspot was made on the basis of the clinical findings and mixed bacterial growths. A thorough investigation was undertaken to identify factors that may have pre-disposed to the condition. There were no changes to the cubicle management or milking routine that could have predisposed to this problem. However although the teats were sprayed following milking, this was carried out inconsistently and teat coverage was variable. Some cows were missed. The SAC recommended this aspect of management was improved.