Cases of interest
As 2024 draws to a close it is not long now before we pass the shortest day and move into 2025, and we wish you all some time off to enjoy at least part of the festive season. Please note that the laboratory in Edinburgh is closed on the 25th & 26th December and the 1st & 2nd of January.
The weather continued to be variable across the UK with the North of Scotland recently emerging relatively unscathed after storm Darragh. Looking at the Met office data our area appears to have had a warmer and dryer autumn (compared to 1991 to 2020 mean) and less rainfall in November. However, complacency is not advised as seasonal disease risks are increasing:
- SCOPS and COWS recently issued a warning of an increased fluke challenge. The unpredictable weather patterns seen mean that it is likely that snail habitats, and therefore liver fluke, will be more widespread. Four diagnoses of acute fluke were made through our Dumfries PM room last month which supports the predicted increase in risk. Advice is to keep testing; you may wish to consider making use of coproantigen which can detect up infections earlier than FECs.
- Bovine respiratory disease (BRD) diagnoses are increasing across the PM centres with a variety of viral and bacterial causes detected. Investigation of a BRD outbreak is often requested by farmers and ideally is multifaceted including the environment. Laboratory testing maybe useful to assess; is BoHV-1 involved; is antimicrobial treatment indicated; and/or if current (if any) vaccination policy is effective.
When considering laboratory testing:
- Selection of animals to sample is important – acute cases which are febrile with a clear nasal discharge are the most useful and ideally sample these before treatment.
- Consider how many animals to test – a single case may not be representative.
- What testing can be done:
- In live animals
- Deep naso-pharyngeal swabs for respiratory PCR and or culture. Use a guarded swab to reduce contamination by commensal organisms and remember the swab must not have a wooden handle as this can interfere with PCR testing. Using viral transport medium and mycoplasma transport medium may improve the diagnostic rate.
- Blood sample acute animals and send to lab for storage, resample the same animals three weeks later. It is important that these paired samples are tested at the same time to allow comparison of the titres.
- Postmortem sampling
- Fresh lung for PCR testing – take a 1cm cube of tissue from the top of the right middle lung lobe.
- Microbiology: Swabs taken after searing the surface are the best but otherwise submit fresh tissue for culture in a pot with limited air space remaining.
- Fixed tissues for histology – take 3 pieces from the left and right lung covering the differing lobes and at the junction of normal and abnormal tissue (see image below). Trachea, larynx and papillary heart muscle are also useful tissues for examination.
Please do not hesitate to contact us if you have any queries regarding sampling and we always appreciate photographs to assist in the interpretation.
An interesting case of respiratory disease in sheep was seen in the Thurso PM room and is worth bearing in mind if called to dyspnoeic or sudden death in Texel sheep.
A two-year-old Texel ewe from a cohort of 150 ewes’ part of an organic flock was submitted having been found dead that morning. The ewe had been recently treated with a commercially available florfenicol and flunixin combination product to address clinical signs of respiratory disease including a purulent nasal discharge.
The submitted ewe was in very good body condition score. Within the abdomen there was a scant dark blood noted alongside some small blood clots through the omentum. A large area that appeared to be a blood clot was seen covering the caudal surface of the liver and the spleen.
Photo one: Liver with the large mass consistent with blood clot removed. Photo 2: Tissue/blood clot removed from liver surface
Exploration revealed that this blood had not originated from the liver or spleen but from an 8cm long by up to 3cm long solid mass from the diaphragm, caudally and below the spinal column on the left side (see photo below). On opening the thoracic cavity through the diaphragm, a significantly sized mass appearing to be consistent with a blood clot was detected in the left caudal chest along with dark liquid blood. This mass appeared solid, possibly of muscle type tissue, with an internal haemorrhagic "sac"/lining.
Photo 3: Diaphragmatic “mass”. Photo four: Open mass with “blood clot” removed and seen middle right
Samples were sent to VSA for culture, PCR and histology. Cultures from the lung were sterile and the extended respiratory PCR did not detect any pathogens.
Histological examination of the lungs detected granulomas suggesting previous parasitic infection and areas of compressed tissue. Severe haemorrhage and muscle necrosis within the diaphragm was seen with large, multifocal areas of extensive haemorrhage and fibrin accumulation recorded. These haemorrhagic inflammatory changes extended into the interstitial area dissecting between muscle fibres. Evidence of previous muscle necrosis and attempted repair was also noted - likely giving the thickened appearance similar to neoplasia grossly. This is similar to diaphragmatic rupture that has been reported in Texel rams previously*.
The previous case report detailed twelve cases that had occurred over a period of two and a half years and concluded that this differential should be considered in cases of dyspnoea and sudden death. More investigation into the underlying cause and suspected breed disposition is required.
* Waine, Ket al, Diaphragmatic lesions and fatal haemorrhage in Texel sheep (in Veterinary Record Case Reports)
Posted by SRUC Veterinary Services on 17/12/2024
