Veterinary Services

Parasitic diseases

The owner of 56 Suffolk ram lambs on a Borders farm reported a general failure to thrive over several months and intermittent diarrhoea. The rams had been grazed on second and third season pasture and also received a daily ration of home-mixed concentrate. Four weeks earlier the group had received an oral trace element supplement and an avermectin anthelmintic. When one of the rams was submitted for necropsy evidence of chronic parasitic damage was noted within the abomasum. A subsequent gut worm count identified 5,200 Teladorsagia adults and larvae in the abomasum and a mass of Nematodirus battus adults and larvae within the small intestine too numerous to count accurately. The owner was advised to re-examine his anthelmintic treatment regime, grazing management and investigate the possibility of anthelmintic resistance.

A three-month-old lamb found dead on an Aberdeenshire unit was in very poor body condition and had evidence of a significant gut worm burden and a heavy infestation of keds (Melophagus ovinus) on the skin. Several puncture wounds were present on the left hind leg, thorax and neck, and reflection of the skin revealed numerous areas of extensive subcutaneous haemorrhage and puncture of the thoracic cavity. The distribution of skin puncture wounds and associated subcutaneous bruising were suggestive of ante-mortem trauma such as that inflicted by a dog or fox.

The owner of a hill farm in the Thurso area reported a total of seven deaths in a group of 60 ewe hoggs during a two-week period. A diagnosis of acute fasciolosis and necrotic hepatitis due to black disease (Clostridium novyi type B infection) was made at necropsy.

Respiratory tract conditions

A nine-year-old ewe was submitted to the Aberdeen Centre with a history of progressive dyspnoea and loss of condition of two weeks duration. Necropsy identified pleural effusion and ascites, likely to be secondary to lymphatic blockage due to a metastasising intestinal adenocarcinoma.

Two cases of deaths following the plunge dipping of sheep were reported this month. Eight deaths were reported in a group of 250 Cheviot ewes and lambs in the week following dipping with an organophosphate (OP) product. When one ewe carcass was submitted for examination evidence of acute fibrinous pleurisy and associated bronchopneumonia of suspected bacterial aetiology was found consistent with inhalation pneumonia. In the second case an eight-month-old Suffolk ram died following a period of respiratory distress. This animal was one of a group of 60 housed lambs that had been dipped two days earlier. Following dipping this and another lamb had died and further two others were clinically affected. Necropsy identified severe pulmonary congestion and several areas of lung consolidation - these lesions being sterile on bacterial culture. Subsequent lung histopathology confirmed a diagnosis of acute interstitial pneumonia in the reparative phase. This diagnosis is considered unusual in sheep, but again has been recorded as occurring shortly after plunge dipping.

Laryngeal chondritis was confirmed at necropsy of a five-month-old Texel ram lamb from a Selkirkshire farm. The lamb was reported to have shown a progressively worsening respiratory stridor, which failed to respond to antibiotic treatment and led to death after two days. Oedema, necrotic ulceration and a thick purulent discharge on the laryngeal mucosa, combined to completely occlude the lumen of the airway in this region.

Musculo-Skeletal conditions

A two-year-old Meatlink ewe was submitted to the Edinburgh DSC after it suffered sudden collapse and death. This animal was one of a group of ewes at grass after their lambs had been weaned some three weeks earlier. One other ewe from the group was also said to have died suddenly during the same period. At necropsy the submitted ewe was in good bodily condition, with pulmonary and hepatic congestion, petechial haemorrhages over the right ventricle of the heart and a small quantity of pericardial fluid. Histopathological examination of the heart revealed extensive, acute myodegeneration. A diagnosis of acute degenerative cardiomyopathy and circulatory failure was made. A nutritional cause was initially considered unlikely because of the age of the animal, and possible toxic and genetic causes were discussed. However, the liver selenium was subsequently found to be inadequate (0.43mg/kg DM, reference range 0.9-3.5), consistent with a nutritional aetiology. Screening of the selenium status of the group was advised to determine the extent and significance of the problem.

High titres to the bacterium Erysipelothrix rhusiopathiae were detected in a group of lame, five-month-old Suffolk lambs. All five serum samples submitted produced titres of greater than 20,480 in the slide agglutination test (SAT).

A group of lambs aged three to four months were presented as lame following a move to clean grazing after weaning. Synovial fluid samples collected from the joints of two severely affected lambs were submitted to Thurso DSC, where bacterial cultures yielded a pure growth of Streptococcus dysgalactiae.

Alimentary tract disorders

Paratuberculosis (Johne’s disease)

In contrast to the situation in cattle, Johne’s disease remains a low prevalence disease in sheep (figure 2). However in the past two years the number of outbreaks recorded has increased from 46 to 64, an increase of 39%. With such small numbers of diagnoses relatively large fluctuations from year to year are to be expected. During that period the number of sheep submissions screened for Johne’s disease increased from 1265 to 1406, an increase of 11%. It should be recognised that the majority of the submissions in this category represent necropsies of adult sheep submitted for varied reasons and does not indicate an increased screening for Johne’s disease of the sheep population.

Nervous system disorders

A four-month-old Scottish Blackface lamb was submitted from a Berwickshire farm after failing to respond to treatment for a suspected pneumonic condition. While there were no specific lesions within the lungs, the meninges appeared cloudy and a bacterial meningitis was later confirmed on histopathology.

Skin diseases

The bacterial culture of swabs taken from skin lesions in two rams produced a pure growth of Corynebacterium capitovis. The skin lesions took the form of several subcutaneous nodules in the area of the lower jaw discharging a thick purulent material. Reports indicate that these lesions responded well to treatment with parenteral antibiotics. Corynebacterium capitovis was first named and characterised in 2001, after being isolated in a mixed bacterial growth from a skin lesion on the head of a sheep (International Journal of Systemic and Evolutionary Microbiology, 51, 857-860). Although gross lesions in this recent case were similar to those of caseous lymphadenitis, the biochemical characteristics of C. capitovis differ from C. pseudotuberculosis in several respects, enabling clear differentiation of the organisms in the laboratory.