Veterinary Services

Hypomagnesaemic tetany was a common diagnosis during the month, particularly in the north of Scotland. The Thurso centre diagnosed three cases in beef cows with calves at foot causing death and recumbency. The adverse weather conditions with persistent rain were considered to pre-dispose to the problem.

Staggers was suspected at necropsy of a dry dairy cow at the Ayr centre that had been housed for three days before being found dead. Necropsy revealed that the right lung was very congested, blood splashing was present beneath the parietal pleura of the right thorax, the tracheal lining contained ecchymotic haemorrhages and the dorsal ligament of the trachea was haemorrhagic. Vitreous humour magnesium was 0.50mmol/l. A diagnostic marker of hypomagnesaemic tetany is considered to be a vitreous humour magnesium level of less than 0.55mmol/l (McCoy and others, Veterinary Record 148, 268-273). The case submitted was the second fatality in 24 hours.

Parasitic diseases

Dictyocaulosis was diagnosed commonly across Scotland during the month with varying disease histories and clinical presentations. The disease was suspected by the Ayr centre as the cause of respiratory disease in dairy cows at grass on the basis of serology, eosinophilia and response to treatment. Faeces samples were negative for lungworm larvae, as is often the case where adult cattle are partially immune to lungworm. However dictyocaulosis was confirmed in another dairy herd by detection of larvae in faeces. Half the herd were reported to have a persistent cough and a herd ‘milk-drop’ had occurred.

Histopathological examination of the lungs confirmed reinfection husk in a 13-month-old heifer from Aberdeenshire with a short clinical history of coughing and slight salivation prior to death. Two deaths occurred in a group of 38. The cattle had grazed the same pasture since mid-July and were treated with an avermectin approximately two weeks prior to death but returned to the same pasture.

In Dumfriesshire the carcase of an ill thriven three-month-old Holstein cross heifer had lungworm visible at its nostrils with many more in the airways (figure 1 - see Related Documents at top right-hand side). In addition it had a strongyle egg count of 20,600epg.

Toxic Conditions

A presumptive diagnosis of bracken poisoning was made on the basis of the history and gross pathology seen in the carcase of an Aberdeen Angus cross calf. It was one of six calves that died from a group of 25 still with their dams in Galloway. Most were found recumbent and pale but died the next day. One had been seen to bleed from the rectum. The submitted carcase had petechiation of the gingiva with echymotic haemorrhages on the peritoneum and pleura. Larger areas of haemorrhage were seen on the intestinal serosa (figure 2 see Related Documents at top right-hand side). There were also haemorrhages on the intestinal mucosa with punched out ulcers lying beneath the blood clot. Haematology was not possible from the samples collected at the necropsy and no BVD virus was isolated from the case. Bracken was freely available in all the fields that had been grazed recently. The farmer reported that he had seen adult cattle actively eating it despite there being no shortage of grass and the provision of ad lib straw and minerals.

Generalised and systemic conditions

The cardiac form of blackleg was confirmed at necropsy of a four-month-old suckled calf from Ayrshire. Only the heart was affected and showed a fibrinous pericarditis. Clostridium chauveoi was detected in the lesion by fluorescent antibody test (FAT) and culture and also in systemic distribution by culture. This was the first death in the group of 10 cow/calf pairs.

A 16-month-old Aberdeen Angus cross bullock was submitted for necropsy at the Perth centre from a group of 30 that had suffered four deaths believed to be related to pneumonia over a period of four weeks. On necropsy the animal was found to be dehydrated and in very poor bodily condition. There was ulceration of the nares and hard palate, and extensive necrosis of the soft tissues of the larynx. Mucosal ulceration was also noted within the abomasum and rectum, and blood clots and mucosal casts were evident within the gut contents. When tissues were submitted for histopathology these changes were identified as being consistent with an underlying Bovine Virus Diarrhoea Virus (BVDV) infection. Subsequently virus identified as BVDV type 1 was isolated from the animal’s tissues.

A three-month Holstein heifer was submitted to the Dumfries centre from a farm with a known ongoing BVD problem. Eight persistently infected calves had been identified during routine sampling of heifer replacements. The heifer had a significant pneumonia and erosions of the coronary band and inter-digital space (figure 3 see Related Documents at top right-hand side). Type 1 BVD virus was isolated from this case in cell culture.

Respiratory tract diseases

Infectious Bovine Rhinotracheitis was confirmed in a group of 120 fourteen-month-old feeding cattle. Following several sudden deaths both at pasture and following housing, a pluck was submitted for examination. Severe tracheal pathology was present. Bovine Herpes Virus type 1 was detected by FAT and virus isolation in cell culture.

Reproductive tract conditions

Antibody to BVD virus was demonstrated in a stillbirth from a suckler herd in Ayrshire where calves delivered by three of the first six heifers to calve were either born dead at term or were weak at birth and died soon afterwards. No pathological or histopathological lesions of BVD virus infection were detected. Thus foetal infection was confirmed but may not have been the cause of the abortion/stillbirth. The group of 14 heifers had proved difficult to get in-calf and was expected to have an extended calving period. The farm acquired replacements as neonatal calves from dairy farms and bucket reared them. The farm boundary biosecurity was poor. A BVD vaccination program is to be implemented.

In Dumfriesshire BVD virus was isolated from a full term stillborn calf. There had been no other problems in the herd. The dam was a second calver who had tested antibody negative earlier in the year. It was advised that she should be tested for antigen.

Nervous system disorders

A three-year-old Simmental cross cow from a small herd in Skye exhibited nervous signs and tended to knuckle when walking. Her front limbs were worst affected and she would often be found in lateral recumbency. Her appetite was normal and she was about five months in calf. There was a high antibody titre to louping-ill virus at 1/1280. IgM antibody was 1/640.