Veterinary Services

Parasitic conditions
Chronic fasciolosis was again a common diagnosis this month as illustrated above, principally in the south-west and far north of Scotland.

The Ayr Centre confirmed chronic fasciolosis at necropsy of an ill-thriven fattening stirk aged 20 months that had gone down and was euthanased in extremis.

In the far north chronic fasciolosis was diagnosed in seven herds mostly affecting cows but in two herds young stock at grass for the first time were affected. Many other groups of cattle have been checked for fluke eggs in faeces on housing and will be re-tested in late January/February 2005.

Fasciolosis was also confirmed in three dairy herds in Ayrshire by examination of faeces for fluke eggs. Problems reported included poor milk production, scour and ill-thrift.

Coccidiosis was confirmed in a four-week-old dairy calf by histopathology of the large intestine. Five similarly aged, individually penned calves had died in one week after showing acute onset abdominal pain and diarrhoea. Gross pathology consisted of gelatinous yellow intestinal contents but little abnormality of the intestinal mucosa. No coccidial forms were detected in intestinal contents.

Generalised and systemic conditions
One of a group of 12, two-month-old Limousin-cross stirks was presented for post mortem examination at the Edinburgh centre. No coughing, diarrhoea or other evidence of disease was reported in the group. At necropsy an eight centimetre length of necrosis was present in the trachea. The cranial lung lobes were congested and collapsed and the caudal lobes congested with a distinct lobular pattern. Fibrin was evident over the left lung. Multiple foci of necrosis were evident in the liver and in the antimesenteric aspect of the small intestines, these coalesced to form a solid band in the ileum associated with fibrinous adhesions between loops of bowel. There were single areas of necrosis in the rumen and rectum. Analysis of a heart blood sample revealed the presence of antibody to bovine viral diarrhoea (BVD), but no evidence of antigen, precluding mucosal disease. Histopathological examination of the tracheal lesion revealed a well-established fungal plaque composed of septate branching hyphae consistent in morphology with Aspergillus fumigatus. Similar hyphae were present in blood vessel associated necrotic foci in other tissues, which all proved to be infarcts. Fibrin thrombi, but no hyphae, were seen in blood vessels in the lung suggesting terminal disseminated intravascular coagulation (DIC). Systemic mycosis is uncommon in immunocompetent animals but no underlying cause was found in this case.

Salmonella Typhimurium DT193 was isolated from the faeces of a four- year-old Luing cow on the Isle of Skye, which had lost its calf in the spring and subsequently failed to thrive. Liver fluke eggs were also detected in its faeces. In total two cows and one bull from the herd of 29 were affected. One cow died despite treatment and another was in poor condition. The same Salmonella Typhimurium phage type has since been isolated from the burn from which the cows had been drinking.

Alimentary Tract conditions
An increase in enteritis cases associated with E coli K99 infection was recorded this month.

Acute enteritis and death in a two-day-old dairy calf, one of four calves to have died recently was found to be due to E. coli K99 infection. At necropsy at the Edinburgh Centre the calf was diarrhoeic and dehydrated. The gut contents were strongly positive for E. coli K99 by enzyme linked immunosorbent assay (ELISA). No other potential pathogens were detected.

On another dairy farm in Ayrshire five two-day-old calves died in 48 hours with scour. K99 E. coli enteritis was confirmed in one calf necropsied and abomasitis due to Clostridium sordellii and cryptosporidiosis in another.

Necropsy of a ten-day-old calf revealed abomasitis and enteritis. Clostridium sordellii was demonstrated by fluorescent antibody testing (FAT) and isolated from the abomasal lesions. Histopathology confirmed clostridial abomasitis. Three other calves had died under similar circumstances following a short period of scour. It is noted that this presentation of Clostridium sordellii abomasitis has hitherto been recorded more commonly in sheep and that the pathology seen in these cases was identical.

A ten-week-old dairy calf was submitted for necropsy with a history of “blowing up” and death soon after. This was the third mortality over a six week period, the previous two calves were found dead and appeared bloated. Necropsy revealed that the swollen abdomen was due to massive distension of the entire small intestine with bloody fluid and gas with an associated dark red intestinal mucosa. Large intestine contents were fluid and brown in colour. No enteric pathogens or clostridial enterotoxins were detected. Histopathology of intestine was suggestive of a pathogenic E. coli infection.

Respiratory tract diseases
Pneumonia cases were commonly diagnosed across Scotland this month.

An eight-month-old Belgian Blue heifer calf died suddenly, some three days after the group of 35 spring-born calves was housed. The owner suspected that this animal had failed to adapt to the barley-based ration and developed a fatal ruminal acidosis. However, on post mortem examination the pH of the rumen liquor was found to be within the normal range, but pneumonia was extensive, with widespread emphysema and the formation of large bullae. Acute respiratory syncytial virus (RSV) infection was confirmed by FAT and subsequent bacterial and mycoplasma cultures failed to identify the involvement of any other respiratory pathogen.

In another outbreak in Ayrshire, RSV virus antigen was detected in lungs by FAT from a five-month-old calf from a unit which reported a severe pneumonia problem with 100% morbidity in a group of housed suckler calves but only one death.

Bovine Herpes Virus type 1 (BHV1) was detected in a broncho-alveolar lavage (BAL) sample from a four-month-old calf with a history of pyrexia, dyspnoea and coughing. The owner reported one death and five affected calves in the group of 30.

Antibody to the virus of malignant catarrhal fever (MCF) was detected in a blood sample from an 18-month-old fattening animal. Clinically the animal presented with corneal oedema, purulent conjunctivitis, diphtheritic plaques in the nares and a pyrexia, but no oral lesions.

Diseases of the locomotor system
Examination of the forelimbs of two feeding bulls from Aberdeenshire confirmed digital dermatitis. The owner reported chronic lameness in feeding bulls for the preceding 12 months. 25-30% of larger animals more than eight-months-old were affected. All four limbs examined had large ulcerated granulating lesions in the anterior interdigital cleft. Although the heel area is the most common site and affected cattle are more likely to have lesions on the hind feet, lesions of digital dermatitis can occur in the interdigital space adjacent to the coronary band, and may occur in the front feet.

Nervous disorders
Perennial ryegrass staggers was suspected as the cause of neurological signs in four, 8-month-old Charolais-cross stirks. A batch of 300 stirks had been purchased two months previously and kept on ryegrass, without supplementary feeding. Four calves had shown ataxia, weakness and collapse and had appeared “drunk”. Two that were able to walk were housed and fed silage and made a full recovery. One which was transported inside, because it was too weak to walk showed ruminal distension and profuse watery scour before dying overnight. Post mortem examination confirmed ruminal distension due to the presence of gas, fluid and lush grassy material and fluid intestinal contents. Multifocal areas of mycotic rumenitis were present in the anterior rumen. There was a limited anteroventral pneumonia. Aqueous humour magnesium was adequate (0.9 mmol/l), but calcium was low (1.6 mmol/l). Pasteurella multocida was isolated from the lungs. Histopathological examination of the brain and spinal cord showed only congestion and occasional mature, mixed perivascular cuffs in the cerebrum. Mild suppurative pneumonia was confirmed in the lungs but no significant abnormalities were detected in the ganglia or other tissues. The neuropathological changes were considered to be mild, non-specific and of questionable significance. The lack of significant changes supports a diagnosis of perennial ryegrass staggers because it is most likely to be a functional derangement, possibly of neurotransmitters, and does not cause changes detectable by light microscopy. Perennial ryegrass staggers would explain the signs in all four animals and recovery in the two simply removed from the pasture early in the course of the disease. Mycotic rumenitis and bloat are likely to have contributed to the fatality.