Veterinary Services

A high number of pneumonia outbreaks were investigated this month. This was consistent with trends reported by practitioners and disease surveillance centres (DSC’s) over recent years with more pneumonia cases reported in the winter, rather than immediately after autumn housing. One outbreak was amongst a group of nine-month-old weaned, housed Limousin-cross calves on a Berwickshire farm. One calf was found dead, after appearing unwell some 24 hours earlier. Other animals were then also seen to be unwell and a decision was made to treat the group with antibiotic. When the dead calf was submitted for post-mortem examination it was found to be in poor bodily condition, with oedema of the brisket and an abscess draining through the skin at this site. Examination of the lungs revealed acute consolidation, accounting for some 70% of the tissues and with an anteroventral pattern. There was evidence of interlobular oedema, and of alveolar and interlobular emphysema, most prominent in the diaphragmatic lobes. Respiratory syncytial virus (RSV) was detected by immunofluorescence on impression smears from lung lavage fluid, and the cut surface of the affected lung tissue. Subsequent paired serology carried out on calves in the same group, confirmed seroconversion to RSV in five of the ten animals sampled.

A four month old suckled calf presented as a sudden death and was submitted to the Thurso DSC for post mortem. It was housed on straw with its mother in mid November when two weeks old and the cows were fed hay and silage with some concentrate. The calf had large numbers of adult Dictyocaulus Vviviparus worms present in the mainstem bronchi whichbronchi, which had caused a severe pneumonia. RSV was also detected by fluorescent antibody test (FAT) examination of lung tissue. It is presumed that this calf either picked up lungworm larvae in the two weeks of life prior to housing or that the infection came from contaminated straw or hay inside or on the bedding. Infection at grass would seem unlikely given the low solid food intakes in two week old calves and husk has previously been described by SAC Veterinary Services in housed calves (Crawshaw and Smith (2003) Veterinary Record 153, 149-150)

Alimentary tract diseases

A three-month-old dairy calf was submitted for necropsy from a Berwickshire farm. The history was of weight loss and scouring of a week's duration, despite treatment for coccidiosis. This animal was one of 20 prospective replacement heifers, housed in a straw-bedded court and fed barley and maize gluten based meal. Examination confirmed poor bodily condition and marked dehydration. Mucosal erosions were noted on the nares and the gums. Multiple punctate ulcers were also seen on the abomasal mucosa, leading to suspicions of Bovine Virus Diarrhoea (BVD) involvement. Changes in the lower small intestine, caecum and colon included marked mucosal thickening and a roughened appearance. Although very few coccidia were seen on smears from the affected gut, subsequent histopathology confirmed chronic changes associated with intestinal coccidiosis. The erosions noted within the abomasum were described as chronic, reactive changes to a previous insult and BVD virus isolation proved negative.

Reproductive tract conditions

There was the usual increase in bovine abortion submissions in February with sixteen cases of Bacillus licheniformis identified at the Thurso DSC making this the most common diagnosis in the area, and in Scotland as a whole. Poor quality winter feed may be responsible for the high number of Bacillus licheniformis associated abortion cases. Bacillus licheniformis was also isolated from two abortions from a pedigree Simmental herd in Morayshire. The abortions occurred at eight months gestation in a group of 40 cows whichcows, which were outside and being fed silage, straw and minerals.

Nervous system disorders

A 2.5 month old Simmental cross calf was submitted to the Perth DSC for post mortem examination. The calf had been dehorned three weeks previously and was found recumbent with all four limbs in extensor rigidity. At post mortem, the calf was dehydrated but otherwise in good condition. There was localised inflammation at the dehorning site and evidence of injection site necrosis in the gluteal muscles (following several antibiotic injections). However, no cause for the rigidity could be determined with bone Calcium / Magnesium ratio, kidney Llead and brain histopathology all within expected limits or normal. A presumptive diagnosis of tetanus due to Clostridium tetani infections was made. There are no specific laboratory tests that can be used to diagnose tetanus, and, as such, a diagnosis is based predominantly on the clinical picture, ruling out such conditions as hypomagnesaemia, cerebrocortical necrosis and lead poisoning, all of which are potential differential diagnoses.

Generalised and systemic conditions

A five-day-old Charolais calf whichcalf, which had been born without assistance but became ill shortly afterwards was submitted for post mortem to the Perth DSC. There was evidence of navel ill, peritonitis and septicaemia with fibrin tags overlying most organs,organs; excess discoloured joint fluid and small bubbles overlying the surface of the brain. Despite milk in the abomasum, a Zinc sulphate turbidity test result of 2 was recorded (RR >14) indicating failure of transfer of maternally derived antibody. E. coli was isolated from a range of organs with Pasteurella species isolated from the brain.