Veterinary Services

Parasitic diseases

The owner of an 800-ewe South Country Cheviot flock near the English border reported an unusually high proportion of lean animals in the final month before lambing. When a live ewe was submitted for examination it was found to be condition score 1. Both lateral incisors were lost and the remaining teeth were loose, while an abomasal worm count revealed the presence of 7,900 Haemonchus contortus. This is an unusual finding for hill sheep in Scotland and represents a significant worm burden, which if reflected in the rest of the ewe flock, would explain a rise in cases of ill thrift.

Generalised and systemic conditions

A two-week-old North Country Cheviot male lamb from an organic flock in Inverness-shire had been treated for meningitis but failed to respond to antibiotic. It was submitted in lateral recumbency and was paddling intermittently. The cerebrum and cerebellum were swollen and on neuropathology there were clearly demarcated and widespread areas of haemorrhagic malacia, infiltration of neutrophils and perivascular serum leakage. The findings were consistent with a diagnosis of enterotoxaemia due to the epsilon toxin of Clostridium perfringens.

Alimentary tract disorders

Coccidiosis was diagnosed in a Lleyn flock in Easter Ross where a large number of four to six week old lambs were scouring. The oocyst counts were up to 346,800 per gram of faeces with around 50% of the coccidia identified as pathogenic species. In addition there was evidence of infection by trichostrongyle species and Nematodirus battus. When two six-week-old lambs were submitted from the flock for necropsy one was diagnosed with pneumonia due to Mannheimia haemolytica, while the other was diagnosed with intestinal torsion/redgut syndrome.

The owner of a Greyface flock in the Scottish Borders reported that over the course of three to four weeks, 15 ewes had developed discharging sinuses on the side of the neck and cheek. Blood had also been noted at the mouths of several of these animals. Initially a sample of the purulent discharge from one ewe was submitted and a mixed bacterial population, including a heavy growth of Arcanobacterium pyogenes was isolated from this on culture. When one of the affected ewes died and the carcase was submitted for examination, bodily condition was found to be very poor. A bloody fetid discharge was noted in the oral cavity and on the cheeks. Within the pharynx there was a large necrotic sinus on the right side from which the discharge exuded. Dissection of the sinus revealed a broad tract that extended from the pharynx to the thoracic inlet, and from there into the chest itself where there was a severe suppurative pneumonia and pleurisy. No abnormality was noted on the surface of the neck, the oesophagus or the trachea, suggesting that the damage present in the pharynx had been the origin of the extending infection. When a second ewe carcase was submitted a sinus was once again found within the pharynx, although on this occasion the tract extended up into the nasal cavity, where extensive damage had been done to the structure of the turbinates. In addition there was aspiration of much necrotic debris into the trachea and from there into the lungs, where pneumonia was well established. Following both necropsies, a heavy growth of Arcanobacterium pyogenes was isolated on culture from the sinus tract and affected organs. Consultation with the owner confirmed that most (but apparently not all) of the affected sheep had received an oral drench prior to the first case being noticed. The dosing equipment used was new and the procedure had been completed with no particular concern from the experienced shepherd nor noticeable distress to the ewes. Nonetheless, a diagnosis of infection following a dosing gun injury was made - although no explanation for either the high incidence rate or the unusual presentation could be provided.

Reproductive tract conditions

A one-day-old Texel cross lamb was submitted alive from a flock in Ross-shire, after it was unable to stand and demonstrated a body tremor. The submitted lamb was recumbent and paddled intermittently. Five similar cases were said to have occurred recently. The clinical history indicated that only the lambs born to mule ewes in the flock were affected and that none of the offspring from the Cheviot or Scottish Blackface ewes were involved. While homebred tups had been used on the flock the previous autumn, two groups of replacement females had also been purchased. Following necropsy, the lamb was found to be negative for antibody to border disease (BD) virus but positive for the virus itself. Further testing of the isolated virus identified it as BVDV-1, suggesting that cattle were the likely source of the virus. Further investigation confirmed that each of the five mule dams of the affected lambs was antibody positive for BD.

A shepherd on a Borders holding, reported that three ewes had recently produced stillborn or non-viable lambs, with one of the latter showing signs of hairy shaker syndrome. Blood samples were submitted from two of the affected ewes, along with a pre-colostral blood sample from the live lamb with the tremor. All three samples were found to be positive for antibody to BD virus.

Other abortion outbreaks this month were associated with Campylobacter fetus subsp. fetus, Bacillus licheniformis, Streptococcus dysgalactiae, Streptococcus uberis and Staphylococcus aureus infections, as well as the most common causes in Scotland, Chlamydophila abortus and Toxoplasma gondii.

Musculo-Skeletal conditions

A total of eight cases of polyarthritis due to infection with Streptococcus dysgalactiae were confirmed in Scotland this month. The Aberdeen Centre reported the condition on two units, affecting lambs in the 10-14 day age range. Clinical signs included inco-ordination and crawling on forelimbs, with lambs often progressing to recumbency. Affected individuals were born to homebred ewes and infectious arthritis had been confirmed on both units in previous years.

Myopathy associated with infection by Clostridium septicum was identified in ewes from a lambing flock kept in unsanitary conditions on a farm in the Thurso area. Necropsy also revealed evidence of past chronic liver fluke infection, although no live parasites were found.

Nervous system disorders

Neuropathological examination confirmed listeriosis in a 12-month-old feeding hogg presented at the Aberdeen Centre in sternal recumbency, depressed and with drooping of one ear and salivation. Four deaths were reported in the group of 350 that had been fed silage, barley and turnips. Listerial encephalitis was confirmed on a second unit following isolation of Listeria monocytogenes from the brainstem of a ewe lamb with a history of nervous signs. Eight other deaths were reported in this group of 900 lambs, which had access to pit silage.

A live two-week-old lamb was presented with intermittent bruxism, salivation, weak horizontal nystagmus, intact reflexes but proprioceptive deficits. Two nymphal stages of the sheep tick, Ixodes ricinus, were identified on the lamb. Louping ill was confirmed serologically and histopathologically in the lamb. This was the first confirmation of the condition on this particular unit, although the disease had previously been diagnosed on an adjacent unit.