Veterinary Services

Parasitic Diseases

Staff at the Edinburgh DSC reported a case in which three out of 700 grazing lambs from different fields on a local farm became ill-thriven. There was a regular worming programme in place for this flock and there was no evidence of diarrhoea or coughing in the affected animals. One lamb died and the other two were submitted alive for postmortem examination. Both were found to be weak and anaemic, and demonstrated bruxism and a green, watery discharge from the mouth. The lambs, which weighed 12.7kg and 12.0kg, were in very poor condition with no visible internal body fat. The main finding in each case was very large numbers of adult Haemonchus contortus worms on the abomasal mucosa and within the watery abomasal content. An investigation of possible anthelmintic resistance was advised.

Two cases of deaths associated with acute fasciolosis were recorded at the Thurso DSC. In one case sudden deaths were reported amongst ewes and gimmers, while on another occasion a Suffolk ram that died unexpectedly was found to have suffered severe liver damage as a result of fluke migration, causing massive haemorrhage into the abdomen.

Alimentary tract disorders

A five-month-old Lleyn lamb from a group of 200 died after an acute scour and was submitted for postmortem examination. The epsilon toxin of Clostridium perfringens was detected in intestinal contents and neuropathological examination confirmed the presence of focal symmetrical encephalomalacia. In addition there was a significant coccidial oocyst burden and associated evidence of previous parasite damage in the intestine.

A five-year-old, Scottish Blackface ewe was found dead with no history of recent illness. Her lambs had been weaned two weeks previously. At necropsy the ewe was in very poor bodily condition with extensive faecal soiling of the perineum. From the middle of the jejunum the intestinal wall became progressively thickened and the contents reduced. The mucosa here and along the large intestine, appeared thickened and showed diffuse congestion. In addition there was a 6 cm diameter area of necrosis and haemorrhage at the tip of the caecum. Bacterial culture of the ileum and caecum yielded a profuse pure growth of Pasteurella trehalosi. Histology of the mesenteric lymph nodes, ileum, caecum and large colon revealed severe, extensive Johne’s disease, with secondary bacterial enteritis and underlying parasitism. While Johne’s disease and parasitism explained the ill thrift, Pasteurella trehalosi appeared to be the cause of the secondary, acute erosive enterotyphlocolitis, an unusual finding.

Respiratory tract conditions

A four-month-old, Suffolk-cross, ewe lamb was submitted to Edinburgh DSC for postmortem examination following a period of ill -thrift. At necropsy the lamb was found to be in moderate to poor bodily condition, with a mucous nasal discharge and diarrhoea. There was marked fibrinous pleurisy, the trachea contained mucus and foam, and approximately 60% of the lung field was consolidated with caseous abscesses throughout. The right atrioventricular heart valve appeared thickened and there was an excess of synovial fluid in the atlanto-occipital and left elbow joints. Pasteurella trehalosi and Mannheimia haemolytica were isolated from two areas of lung and Arcanobacterium pyogenes was isolated from the lung and left elbow. Histology of the lung confirmed a diffuse suppurative pneumonia and endocarditis.

Two Scottish Blackface shearling rams, purchased on to a holding near Inverness, developed respiratory signs that failed to respond to treatment with antibiotics or anti-inflammatory treatment. It was reported that neither animal had grown as well as others in the same group. When one of these two sheep was submitted for postmortem examination the wheelbarrow test was found to be positive. The lungs were found to weigh 2.6kg, with around 80% of the cranial lung lobes and 50-60% of the diaphragmatic lung lobes appearing grey and indurated. Several abscesses up to 3cm in diameter were scattered throughout the lung tissue and Fusobacterium necrophorum was isolated from these on culture. Ovine pulmonary adenocarcinoma was confirmed on subsequent histopathology, when evidence of mycoplasma infection was also apparent.

Reproductive tract conditions

The owner of a Suffolk ram reported that the animal had been purchased on to an Inverness-shire unit as a shearling and run with a group of 20 ewes in autumn 2005. The animal was seen to serve ewes and all the females in the group were marked; however no lambs were born this spring. On examination of the ram the testes and epididymides were soft on palpation. Two semen samples were collected using the electroejaculator, both of which were watery and showed no evidence of sperm motility. Microscopic examination of the semen smears confirmed that all spermatozoa were dead, with evidence of detached heads and distorted or tightly coiled tails. Such primary abnormalities indicate a major defect of spermatogenesis.

Mammary diseases

The carcass of a Texel ewe was submitted to the Dumfries DSC where it was found to have a severe mastitis affecting the left side of the udder. In addition the lungs were deeply congested and petechiated. Mannheimia haemolytica was isolated from both the mammary gland and the lungs; although it was thought more likely that the udder was the primary source of infection

Musculo-Skeletal conditions

A group of approximately 550 single Cheviot lambs were gathered for weaning from hill ground on a farm in the Dumfries area. These lambs appeared normal until confined in the handling pens, when several became severely lame. A total of 15 were euthanased due to long bone fractures. Three lambs were submitted for postmortem examination where each was found to have suffered fractures of the proximal tibia. In the three submitted lambs the bone cortex, measured at mid-shaft in the tibia, was found to be some 2-3mm thick. This compared to a thickness of 4-5mm in a Blackface lamb of the same age (Figure 2; use the link on the right). Bone ash content of the affected lambs was 10.4%, 15.2% and 15.6% respectively. The equivalent figure for the normal lamb was 23.1%. Bone calcium to phosphorus ratio was normal, as was liver copper, cobalt and lead. A diagnosis of osteoporosis was made on the basis of gross findings. These lambs had been dosed once at the beginning of June, with a combined praziquantel and levamisole oral drench. However, worm counts at necropsy revealed surprising large populations of Teladorsagia and Nematodirus species, given that these were hill lambs. However, no Trichostrongylus worms were identified; these being the parasite species previously associated with osteoporosis. It was suggested that in this case a chronic nematodiriasis might have predisposed the lambs to the condition.

Nervous system disorders

Severe cerebrocortical necrosis was confirmed as the cause of death in a four-year-old Greyface ewe in good body condition. A single animal was affected on this Aberdeenshire unit.