Veterinary Services

A seasonal increase in the incidence of lungworm infection was noted, particularly in the west of Scotland, with the weather ideally suited to the development and spread of lungworm larvae on pasture.  In one example, a four-year-old Holstein cow was submitted to the Dumfries centre for postmortem.  This was the third death in a group of 70 cows purchased from Lincolnshire in February.  Twenty others were showing signs of tachypnoea, pyrexia and nasal discharge.  The other 70 homebred cows on the farm were unaffected.  At necropsy there was evidence of pleurisy and consolidation of the anteroventral lung lobes (figure 1 - please see top right-hand side).  There were also isolated areas of consolidation in the caudal diaphragmatic lobes.  Large numbers of adult Dictyocaulus viviparus worms were seen in the airways and Mannheimia haemolytica was isolated from the lung.  Although the bacterial type pneumonia was severe and the likely eventual cause of death, the SAC considered that it was secondary to a severe lungworm challenge in cattle with limited previous exposure to the parasite.

Lungworm larvae were demonstrated in the faeces of three of six dairy cows from an Ayrshire herd in which a few cows had developed a dry cough.   Young stock on the farm were treated with an anthelmintic but not vaccinated against lungworm.  The patent infection suggested that these cattle had limited previous exposure and little immunity to the parasite.

Three cases of ill thrift in adult cattle due to chronic liver fluke disease were diagnosed in the north of Scotland.  The affected animals were not treated since housing in late 2006.  The cattle became infected since they were turned out to pasture in May. 

Generalised and systemic conditions

Two yearling, Charolais cross bullocks died with different histories on the same farm in the space of one week and were submitted to Dumfries.  One animal had an oculonasal discharge and was reported to show fitting behaviour before death.  A haemorrhagic scour and enlarged lymph nodes were found at postmortem.  In addition there was corneal oedema, conjunctivitis, oral ulceration and reddening of the muzzle.  Histopathology and PCR testing for ovine herpes virus type two confirmed a diagnosis of Malignant Catarrhal Fever despite there being no history of contact with sheep.  A second animal died after scouring profusely for 48 hours.  Oral ulceration especially of the hard palate was evident in this case also and there were numerous ulcers in the oesphagus (figure 2 - please see top right-hand side).  Positive tests for bovine virus diarrhoea (BVD) antigen confirmed this as a case of mucosal disease.

Alimentary tract disorders

Aberdeen and Perth diagnosed necrotic enteritis syndrome of suckled calves. The Perth case was a three-month-old Simmental calf that was found collapsed, dehydrated and cold.  Necropsy revealed patches of haemorrhage evident on the luminal surface of the abomasum. The small intestine was thickened, pale and empty while the large intestine was thickened and pale but contained watery contents.  No significant organisms were isolated however histopathological examination of the kidney revealed a patchy, chronic, interstitial nephritis with marked fibrosis but minimal inflammation. There was extensive, acute tubular degeneration and necrosis, and interstitial congestion with proteinaceous debris in the damaged tubules. Examination of the small intestine showed dramatic mucosal distortion with dilation of the glands, attenuated epithelium and fibrosis. There was a mild interstitial lymphocytic infiltrate.  The large intestine showed collapse of the mucosa into the submucosal lymphoid deposits. These changes were typical of necrotic enteritis.

A four-year-old Holstein cow, one of three cases in late lactation, presented clinically with no milk, rumen stasis and a right dilated abomasum.  It was euthanased after failing to respond to treatment and submitted to Dumfries for necropsy. The contents of the forestomachs were liquid and the anterior duodenum appeared to be constricted by fibrous tissue within the gut wall and in the surrounding mesentery.  The bile ducts were severely calcified although no flukes were seen.  Histopathology showed an active chronic duodenitis with evidence of fungal hyphae present.  A diagnosis abomasal dilatation and outflow obstruction secondary to duodenitis was made. As the affected area was where the common bile duct enters the duodenum The SAC speculated that there was an association between the very severe biliary tract pathology and the duodenitis and surrounding fibrosis seen. 

A six-year-old Holstein cow was found dead with evidence of melaena.  Necropsy revealed that the anterior jejunum was dilated with fluid while the intestine was empty distal to this point.  A 20cm blood clot was present causing an obstruction.  The mucosa appeared ulcerated and histopathology revealed lesions that suggested mesenteric thrombosis and infarction.   Large numbers of adult fluke were present in the bile ducts of the liver, which showed little fibrosis.  This was surprising given that the cow had been housed and zero grazed for the previous nine months.

Respiratory tract disorders

A three-year-old cow died after a short period of severe dyspnoea.   Severe interstitial emphysema was found at postmortem examination, and the area about the larynx was dark red to black and haemorrhagic.  No significant pathogens were demonstrated, but histopathology showed acute haemorrhage and degeneration within the muscles of the larynx, probably traumatic in origin.

Reproductive tract disorders

Perth received stillborn calves from five unrelated beef suckler farms in Perthshire and Angus. Each farm had experienced an unusually high number of stillbirths and the histories were similar in each case.  The calves were born at full term and were either dead when the cow was first identified by the farmer as peri-parturient or were alive when the cow was found but died during calving.  Postmortem findings indicated dystocia or delayed calving in each case, and some farmers reported that the cows did not push during parturition.  No infectious cause of stillbirth was identified on routine screens of stillborn calves and there was no evidence of goitre.  The SAC suspected that these stillbirths were due to Slow Calving Syndrome, where reduced appetite or anorexia in fat cows prior to calving leads to fat mobilisation, which reduces the available magnesium and in turn impacts on calcium mobilisation. Reduced calcium levels reduce the ability of the uterus to contract properly and proceed quickly through second stage parturition. Further investigations into this problem are underway on one unit where losses were particularly high.

Nervous conditions

Louping ill was confirmed on histopathological examination and serology in a three-month-old Simmental-cross calf from a beef suckler farm in Perthshire.   It was the third calf on the farm to show similar clinical signs. The calf was live when presented but was recumbent and moribund. Examination revealed a small number of ticks on the belly and inner thighs.

Renal diseases

A seven-year-old Simmental cow lost condition, developed haematuria and died.  In 2005 the herd had investigated a problem with cystitis and pyelonephritis.  Postmortem examinations were not carried out at that time and the problem appeared to resolve.  The ureters were inflamed, the bladder wall thickened and bloodstained urine and a gravel deposit were present in the renal pelvis.  The kidneys were fibrosed and histopathology confirmed that the nephritis was chronic in nature.  The SAC suspected that ascending infections occurred during the winter housing period, possibly related to a poor water supply.