Veterinary Services

As cattle were housed and winter feeding commenced sporadic cases of ruminal acidosis were diagnosed. The Ayr Centre confirmed two cases, in one acidosis (rumen pH 4.9) was confirmed in a ten-month-old purchased beef bullock, the first death in a group of 42. The diet was grass silage and a mixture of maize gluten and citrus pulp – the latter is an acidic feed unless limestone has been added to it. Acidosis (rumen pH 5.0) was also confirmed at necropsy of a six-month-old heifer on another farm. This animal had been housed three weeks previously and fed ad-lib concentrate.

Parasitic conditions
Coccidiosis was diagnosed in a three-month-old dairy bull calf submitted for post mortem examination at the Dumfries Centre. The calf had lost condition and become recumbent, although it was still bright. Histopathology suggested that coccidial damage was the most likely cause of the clinical signs with degenerate crypts and a moderate interstitial lymphocyte infiltrate alongside immature coccidia.

Generalised and systemic conditions
Salmonella Dublin associated disease was again common this month with the majority of cases with varying clinical presentations being diagnosed by the Ayr centre.

A dairy cow was submitted for necropsy after going down on concrete and dying soon after. Salmonella Dublin infection was confirmed after isolation of the organism in septicaemic distribution from the case. Salmonella Dublin enteritis and infectious bovine rhinotracheitis (IBR) were confirmed at necropsy of a 12-week-old dairy calf. The group of calves, weaned two weeks previously, were coughing and had chronic scour and wasting. The clinical presentation was one of ‘peri-weaning scour syndrome’, however Salmonella Dublin was isolated from the intestine and Bovine Herpes Virus type 1 (BHV1) was identified in the lungs by fluorescent antibody testing (FAT).

Abortion due to Salmonella Dublin infection was confirmed by isolation of the organism from foetal stomach contents, lung and liver of a foetus from a dairy herd where three of 180 heifers at grass had aborted in three weeks. Although herd vaccination was carried out in response to this diagnosis, a further five heifers and eight cows subsequently aborted. Affected cattle were noted to be ill and in one case a heifer died after aborting. Although the source of the infection was not confirmed, a group of calves which developed scour and joint-ill during the summer, which was not investigated further, was suspected. Salmonella Dublin arthritis of the stifle joint was confirmed by post-mortem examination of a calf aged around three months from a dairy farm with an on-going problem of joint-ill.

Salmonella Dublin was also isolated in pure growth from a mastitic milk sample from a dairy cow. This bacterium is an uncommon cause of bovine mastitis. No previous or subsequent isolations of Salmonella Dublin have been made from this farm.

Alimentary tract conditions
Salmonella Typhimurium DT40 was isolated from a suckler cow in the Western Highlands. A group of eight cows all had sudden onset of scouring and some had dysentery. The same phage type of Salmonella Typhimurium was isolated a fortnight later from a 28 year old horse which was weak and had profuse diarrhoea.

Outbreaks of neonatal enteritis in autumn calving dairy herds were investigated frequently in south-west Scotland. One severe outbreak occurred in a herd where 180 cows and heifers were calving in a two month period. Calves were reared in group pens and a severe scour was reported in calves at two to three weeks of age with approximately 50 calves affected. Type A rotavirus was the only significant pathogen identified in 4/5 scour samples examined. Unfortunately, owing to the tight calving pattern it was too late to vaccinate dry cows against rotavirus this season and advice on hygiene and colostrum administration was given. Another dairy herd with a neonatal enteritis problem in calves from three-days-old submitted one affected calf for necropsy. Scour due to Cryptosporidium and E.coli K99 infection and E.coli septicaemia and joint-ill were diagnosed. A serum zinc sulphate turbidity (ZST) test result was 6 turbidity units (TU) (reference range > 14) suggesting that colostral antibody absorption was poor.

Respiratory tract diseases
Pneumonia outbreaks were again common this month with the common risk factors of housing, transport / marketing and mixing of cattle identified in most cases.

Transit fever was confirmed at necropsy of purchased beef cattle on four farms by the Ayr Centre. Lung pathogens demonstrated were Mannheimia haemolytica, Histophilus somnii, Arcanobacterium pyogenes and Mycoplasma bovis.

Two bullocks aged twelve and eighteen months from a fattening unit in Inverness-shire died suddenly. The animals had been purchased less than two weeks previously and were in a group of 65 in a shed with inadequate ventilation. Mannheimia haemolytica and Pasteurella multocida were isolated from lung lesions from both animals. Fluorescent antibody testing (FAT) for respiratory syncytial virus (RSV) and parainfluenza type 3 virus (PI3) proved negative and there was no evidence of viral involvement on histopathology.

In Caithness a sixteen-month-old calf found dead was found to have an acute tracheitis and severe pneumonia post mortem. The trachea was not narrowed but the surface was red and inflamed. FAT examinations proved positive for PI3 on sections of trachea and lung lobe. No other pathogen was identified.

A six-month-old Limousin cross calf was submitted for post mortem examination after an acute death while clipping. Severe bruising was present in the cervical region and the trachea was occluded by a haematoma lying between the tracheal rings and tracheal mucosa completely blocking the tracheal lumen.

Reproductive tract conditions
An increase in the number of abortion investigations carried out was noted this month. Investigation of two abortions on consecutive days on a beef farm in northern Aberdeenshire confirmed infection with Aspergillus fumigatus. In the first submission the organism was recovered from the placenta and from foetal stomach contents of the second foetus. There was a history of recent introduction of poor quality hay. The case highlights the requirement for submission of the placenta to enable a comprehensive investigation in cases of bovine abortion.

A stillborn Simmental calf, the fourth similar case, was submitted for investigation from a herd of 100 suckler cows. All affected cows had calved with assistance, but without difficulty. The meconium-stained heifer calf weighed 53kg, meconium had been ingested and inhaled and there was a large volume of amniotic fluid in the airways. The findings were consistent with foetal stress and delayed second stage labour. The dam was blood sampled shortly after calving and had a calcium level of 2.1mmol/l (reference range 2.2-2.6mmol/l) and a phosphate level of 1.3mmol/l (reference range 1.7-2.2mmol/l).

A fetus of approximately eight months gestational age, submitted from a suckler unit, had features of an achondroplastic or bulldog calf, with short limbs, short neck and ascites. Blood samples were submitted from a five-year-old Holstein cow being used for embryo transfer, reported to be on a good plane of nutrition and milking well, but with poor egg viability. Plasma inorganic iodine was profoundly low (14.0 ug/l, reference range 101-300) and copper slightly low (8.5 umol/l, reference range 9.0-24.0).

Diseases of the locomotor system
Cellulitis of the left hind leg due to Arcanobacterium pyogenes was confirmed at necropsy of a seven-month-old suckled calf housed on slats two weeks previously. Traumatic injury associated with housing was suspected as the primary cause.

A one-day-old Charolais calf submitted for post mortem examination to the Perth Centre was unable to stand with grossly distorted limbs, the third case to be born with similar clinical signs. Reflexes were intact and rectal temperature normal. Post mortem examination revealed an undershot jaw and all joints demonstrated extreme laxity with joint dislocation easy to produce. The right hind leg was rotated laterally up to 180 degrees and both acetabular fossae were shallow with minimal cover of the femoral heads. Bone measurement and histopathology proved inconclusive for congenital chondrodystrophy. It is unusual to see cases of congenital chondrodystrophy so late in the year, however the dams of affected calves had been fed an all- silage diet during the critical fourth month of pregnancy.

Nervous disorders
A suckler herd in Argyll experienced a nervous disorder in 11 cattle, eight of which died, over a six week period. Eight cows, two heifers and the stock bull were affected. The affected cows often showed signs similar to hypomagnesaemia and several animals were found dead. One cow showed a “goose stepping” gait and one heifer tremor and a “louping” gait as well as aggression. Pyrexia was detected in some individuals examined. Two affected cows and a heifer all showed very high titres to the virus of louping-ill (1/1280) most of which was IgM, indicative of recent infection. A further affected cow and a heifer proved seropositive for the virus of louping-ill but significant amounts of IgM could not be demonstrated. Seven out of 10 unaffected in-contact cattle blood sampled also proved seropositive for louping-ill, several with high titres (>1/640). No carcasses were submitted for necropsy to confirm the diagnosis, however, the serological evidence was highly suggestive of louping-ill being the cause of the problem. The cows were treated with an ectoparasiticide and moved to low ground for wintering where one further cow was lost probably within the incubation period for louping-ill.