Veterinary Services

The owner of a holding in Aberdeenshire reported scouring amongst a group of 300 three-month-old lambs, despite anthelmintic treatment three weeks earlier.  Morbidity was around 20 per cent and nine deaths had occurred.  Examination of a pooled faeces sample confirmed the presence of 1,100 Nematodirus species epg.  On a second unit in the area, parasitic gastroenteritis was confirmed in a group of 250 lambs where six deaths had been recorded.  Again the lambs had been treated 13 days previously with a benzimidazole anthelmintic. A faecal worm egg count of 4,700 trichostrongyle epg and 400 Nematodirus spp epg was recorded.  In both these cases the owners were advise to check the accuracy of the dosing gun and bodyweight of the lambs as part of the further investigation of anthelmintic efficacy.

Generalised and systemic conditions

Nine diagnoses of lamb mortality attributable to pasteurellosis were made around Scotland this month – the same figure as was recorded in July 2006.  Most were due to pneumonia associated with Mannheimia haemolytica infections.  In one typical case two, dead Scottish blackface lambs were submitted from a flock in Ross-shire.  Other lambs in the group were reported to be scouring, despite recent anthelmintic treatment.  Pleuropneumonia, pericarditis and septicaemia due to Mannheimia haemolytica was diagnosed in both lambs.  In another case, ulcerative oesophagitis was the predominant lesion, while in yet another the initial infection was judged to be mastitis.  Mannheimia haemolytica  was also isolated from a case of acute bacterial abomasitis in an eight-week-old Cheviot lamb.

Alimentary tract disorders

Three, well grown two-month-old lambs died over the course of a week on a farm in the Aberdeen area. Examination of a carcase revealed a necrotic and malodorous pharyngeal lesion, and large blood clots within the reticulum and rumen.  The lambs received an oral drench some ten days earlier and a dosing gun injury was suspected as the cause of death.  At Edinburgh a live six-week old lamb was presented with a swollen head and was euthanased on welfare grounds.  Necropsy confirmed necrotising pharyngitis with associated abscessation. Subsequent histopathology also revealed marked spontaneous lymphoid tissue development within the lung parenchyma. This was judged to have originated from the pharyngeal lesions, possibly as a result of dysphagia and the resulting repeated aspiration of food.  The origin of the pharyngeal lesion was not ascertained in this case.

A six-year-old Scottish blackface ewe was submitted from a Borders farm where 17 of 720 ewes of a similar age had wasted and died since the beginning of the year.  Johne’s disease had been diagnosed within the flock previously and was confirmed again in this case.  Two thirds of the jejunum and the whole of the ileum showed thickening and yellow pigmentation.  Ziehl-Neelsen stained smears from the affected areas of gut were found to be positive for acid-fast organisms. Vaccination is being considered for this flock.

Dumfries reported on a three-year-old Suffolk ewe that had progressively lost condition since lambing in February.  The ewe had not reared any lambs, but had continued to eat and remained bright until shortly before dying. The ewe was in poor body condition and the abdomen appeared distended due to massive enlargement and impaction of the abomasum (see Figure 3 - please see top right-hand side).  The aetiology of abomasal emptying defects are unknown, but they may be an acquired dysautonomia with an hereditary predisposition.  The problem has been seen in Suffolk and Hampshire sheep and it often occurs after lambing.

Respiratory tract conditions

A well-grown Texel ewe lamb that died suddenly was submitted to Perth.  Necropsy identified oedema of the mucosa in the region of the larynx, which reduced the lumen of the airway considerably.  The trachea was filled with a thick foam, while there was peracute congestion and oedema of the lungs.  No significant bacteria were isolated from the lungs and subsequent histopathology identified acute interstitial pneumonia, which taken along with the laryngeal oedema, led to suspicions of an allergic aetiology.

Cardiovascular diseases

Three adult mule ewes developed a joint associated lameness over a period of one week on a Dumfriesshire farm.  All three animals were euthanased and necropsied, with suppurative arthritis and endocarditis recorded in each case.  A pure growth of Streptococcus dysgalactiae was confirmed on culture.

Nervous system disorders

Severe suppurative meningitis due to Mannheimia haemolytica was diagnosed in a three-month-old lamb from a flock in Inverness-shire.  The lamb had been in lateral recumbency, and showed signs of opisthotonus and paddling of the legs.  It had not responded to treatment.

Louping ill was confirmed in a two-month-old Scottish blackface lamb found in a moribund state on hill grazing.  This diagnosis was made despite a rigorous tick control programme on this Highland farm, with pour-on alpha-cypermethrin applied approximately every six weeks.  The last application was three weeks prior to the carcase submission.

Three good lambs died on an upland holding in Perthshire after they were found in a recumbent state the day before and failed to respond to antibiotic treatment. When one lamb was submitted for necropsy there was no bacterial growth on culture of the brain, but subsequent histopathology revealed evidence of extensive suppurative meningitis and encephalitis consistent with a diagnosis of listeriosis.

Skin diseases

Caseous lymphadenitis (CLA) was confirmed on bacteriology in 12 flocks in Scotland this month the same figure as was recorded in the previous four months combined and three times as many as were diagnosed in July 2006.  Included in this total were eight outbreaks in the area served by Thurso.  A Staphylococcus species organism was isolated from a skin abscess from a ram in Ross-shire when a pus sample was submitted in order to rule out CLA.