Veterinary Services

St. Boswells considered that above average rainfall and grazing management contributed to an outbreak of parasitic bronchitis in a herd of 50 spring calving suckler cows. The affected group was rotated between two fields of rough grazing every two weeks. In late July two cows were clinically affected and one died. An on-farm postmortem examination identified adult lungworm in the trachea and the surviving cow was treated with an anthelmintic. No other animals were treated and no further clinical signs were noted until two months later when five animals were affected.  One of these, a three-year-old cow, died and necropsy revealed that 80 percent of the lung volume showed consolidation, fibrosis, collapse and interstitial emphysema. Numerous lungworm eggs containing larvae were detected in fluid obtained from the small bronchioles. This confirmed the diagnosis although no adult Dictyocaulus viviparus were observed grossly. Histopathology revealed both chronic bronchopneumonia due to the presence of adult and larval helminth parasites and acute interstitial lung damage due to larval migration and emergence. SAC C VS considered that sub-clinical infection was present in the group throughout the summer and this was responsible for the chronic lesions. The cows were then exposed to very high numbers of lungworm larvae when they moved field causing reinfection syndrome. There were no further cases following treatment of the group with a pour-on ivermectin.

Dumfries identified a high coccidial count of 108,500 oocysts per gram in a faecal sample from a three week old dairy calf with diarrhoea.  Although speciation of the oocysts was not performed, this count was considered significant and suggested infection very early in life.  A second dairy herd with a history of wasting in 10 to 21-day-old calves submitted faeces from two-week-old calves.  Coccidial oocysts counts were 72,000 and 50,000 oocysts per gram.  Speciation showed that 80-90 percent were Eimeria ellipsoidalis and up to 10 percent E. zuernii.  Although considered less pathogenic SAC C VS suspected that the E. ellipsoidalis was probably significant in this case.  This species has a short pre-patent period of eight to 13 days.  The cows calved outside in an unhygienic paddock and the calves remained with them for one to two days.  SAC C VS considered this contaminated environment was the probable source of infection.

Generalised and systemic conditions

Three outbreaks of salmonellosis due to Salmonella Typhimurium were diagnosed across Scotland. Inverness recovered phage type 110 from faecal samples from two recently calved Belgian blue-cross heifers with diarrhoea. One had a stillborn calf. This phage type is only occasionally recovered from bovine samples but is often associated with human illness. Unfortunately on this farm there was a report of a sick child. Further investigation, in collaboration with AHVLA and Highland Council Environmental Health, recovered phage type 120 from ten further samples from the child, further dog, bird and cattle faeces collected from the farm and water samples. The Scottish Salmonella Shigella and Clostridium difficile Reference Laboratory (SSSCDRL) considered that , based on further genotypic testing,  it was not possible to exclude a close relationship between the twelve recovered isolates from this outbreak. Perth diagnosed phage type 193 as the cause of profound milk drop and haemorrhagic diarrhoea. Approximately 20 percent of the herd was clinically affected and several deaths occurred. Ayr identified phage type 104 as the cause of death of a 12-year-old dairy cow that had diarrhoea since calving one week previously. The same agent had caused diarrhoea in calves earlier in the year and the cows were vaccinated against Salmonella spp.

Alimentary tract disorders

Further cases of jejunal haemorrhage syndrome (JHS) were diagnosed by Edinburgh and Perth. The Edinburgh case was in a high-yielding two-year-old Holstein Friesian dairy cow with a history of sudden-onset recumbency prior to death. At necropsy a 60 cm length of distal jejunum was dark red/purple in colour. This and the preceding three metres of intestine were filled by a cast of clotted blood (Figure 1 - please see top right-hand side).  Blood was also present in caecum and rectum.  No histological changes were found in the intestine to explain the haemorrhage and a gross diagnosis of JHS made. Perth diagnosed the condition in a 34-month-old Charolais bull that died after displaying signs of colic and developing melaena. A Hereford cow from the same premises was necropsied three weeks previously when intestinal rupture and haemorrhage of unknown aetiology were diagnosed. SAC C VS now considers that these findings may have been secondary to JHS.  This emerging condition appears to occur more commonly in dairy cattle than beef cattle. The cause is, as yet, unknown although some workers have suggested that Clostridium perfringens type A may be implicated. None of these cases showed evidence of clostridial involvement.

Musculoskeletal conditions

The carcase of a seven-month-old Charolais-cross castrated calf submitted to Ayr was one of five calves from a group of 48 affected by swollen joints or limbs a few days after castration. Severe septic arthritis was noted in all the joints. The lesions were most severe in the hind feet with toe necrosis evident and pus discharging at the coronary band (Figure 2 - please see top right-hand side). Severe extensive pneumonia, likely due to haematogenous spread of infection, was also seen. Despite the history of recent castration the wound was clean and it did not appear to be the source of infection. In the following weeks another male calf and five heifer calves also became lame. An on-farm investigation found that the calves had to cross rivers and walk through poached gateways whenever they were gathered. In addition there were many sharp stones in the walkways as a result of recent building work. SAC C VS considered that soft hooves from the wet under-foot conditions and sharp stones predisposed to white line disease and subsequent ascending and haematogenous spread of infection.

St. Boswells identified an acute myopathy of unknown aetiology in an adult dairy cow that became recumbent. Histopathology revealed acute myofibre degeneration at several sites, including the diaphragm, quadriceps and gluteal muscles. Hepatocellular swelling and fine vacuolation within hepatocytes was also observed. The liver copper value was 13,200 umol/kg DM (reference range 314-7,850 umol/kg DM) and abnormal accumulation of copper within hepatocytes was confirmed with rhodanine staining. Five of six liver biopsies subsequently collected from clinically normal cows in the herd also showed raised liver copper values.  SAC C VS considered that the high copper level might be unrelated to the myopathy but investigations continue to determine the source of the copper. The copper level was not sufficiently high for the FSA to be informed.