Veterinary Services

Toxic conditions

A total of six ewes from a group of 100, and a further six of their 190 lambs, died at grass following the inappropriate use of a copper-containing pasture treatment. The land in question was sprayed with copper oxychloride, a compound used principally to correct copper deficiency on ground producing cereal crops. In this case permanent grass was treated at the end of February, and was then grazed for the first time by ewes and lambs from mid March.

In addition, the ewes received a concentrate ration throughout this period. The first deaths were recorded in May and were initially attributed by the farmer to pasteurellosis. However, when further deaths occurred in June, carcasses were necropsied and a diagnosis of chronic copper poisoning was established. Further investigation carried out at the direction of the Food Standards Agency, Scotland (FSA), confirmed that the pasture was providing potentially toxic levels of copper. Further blood testing and necropsies confirmed that both the lambs and the ewes demonstrated elevated serum and tissue levels of copper. Specific advice was then given to reduce the likelihood of further deaths and to ensure that affected animals did not enter the human food chain.  

Parasitic diseases

A diagnosis of nematodirosis was made on 40 occasions this month. In an outbreak reported by the St Boswells Centre, five lambs aged between six and eight weeks had died and a further 30 were seen to be scouring. When two of the casualties were submitted for post-mortem examination, Nematodirus battus adults and larvae identified in washes from small intestine were too numerous to count accurately.

Similarly in 2004 (figure 1: click on link in right hand column) outbreaks of nematodirosis in lambs occurred most commonly in Scotland in June causing deaths and ill-thrift with scour in Scottish flocks. A steady increase in the number of outbreaks of nematodirosis has been recorded in Scotland since 1995 (figure 2: click on link in right hand column).

Significant numbers of Nematodirus spp worm eggs were demonstrated in a pooled faeces sample from 12-week-old lambs on an Aberdeenshire unit. Black scour was reported in a large proportion of the 450 lambs in the group and two deaths had also been recorded. The farm had a previous history of nematodirosis and coccidiosis. Benzimidazole resistance had also been recorded in trichostrongylids on the farm and the affected lambs had been dosed with levamisole four weeks previously.

Generalised and systemic conditions

Tick pyaemia was diagnosed in a two-month-old Cheviot lamb from a flock in Inverness-shire, in which 12 out of 90 lambs were reported to be ill-thriven. Although a topical ectoparasiticidal treatment had been administered some three days previously, ticks were present on the carcass. Numerous small abscesses were present throughout the lungs, liver, kidneys and spleen, from which Staphylococcus aureus was recovered on culture, confirming the diagnosis.

A flock in Inverness-shire reported problems of ill-thrift and deaths amongst lambs at six to eight weeks of age. A total of nine deaths had occurred in the group of 40 and another three lambs were in poor condition. Most of the affected lambs were said to have joint swellings. Staphylococcus aureus was isolated from affected joints and other tissues of two affected lambs at necropsy. Ticks were present on one of the lambs, while both carcasses showed evidence of mild parasitic gastroenteritis (PGE) and coccidiosis. The liver selenium in one lamb was found to be subnormal, at 0.64mg/kg DM (reference range 0.9-3.5mg/kg DM). The final conclusion in this case was, that although tick pyaemia was likely to be the main cause of the problem, a combination of other factors had contributed to the reported clinical signs and deaths.

Alimentary tract disorders

Six lamb deaths were reported in a Scottish Blackface flock in Banffshire when one carcass was submitted for post-mortem examination. The only significant finding was of a coccidial oocyst count of 38,600 per gram, of which 66% were identified as the pathogenic species Eimeria ovinoidalis.

Cardiovascular diseases

A two-month-old Suffolk-cross lamb in good bodily condition, was found dead at grass on a Roxburghshire farm. On necropsy the carcass showed evidence of acute pulmonary congestion and oedema, and marked pleural effusion - all findings suggestive of a left-sided heart failure. Examination of the heart confirmed the presence of a large vegetative lesion on the left atrio-ventricular valve, from which group C streptococci were subsequently isolated.

Reproductive tract conditions

The Thurso Centre reported the isolation of Clostridium sordellii associated with a fatal emphysematous metritis in a four-year-old ewe. This late-lambing ewe was reported to have a prolapsed vagina before and after parturition.

Mammary diseases

A hill ewe was submitted to the Edinburgh Centre for necropsy, after dying suddenly some four weeks after producing a single lamb. The ewe had a swollen and hard left mammary gland, which produced watery fluid and clots on stripping. Other findings were mucous membrane cyanosis and pulmonary congestion. Mannheimia haemolytica was cultured in pure growth from the mammary tissue. A second ewe from the same farm was also found to have suffered an acute toxic mastitis. On this occasion a pure growth of E. coli was cultured from the right mammary gland, which was hard, swollen and congested with multiple cavitations containing a turbid fluid.

Musculo-Skeletal conditions

Recent surveillance reports from SAC VS have highlighted an increase in recorded cases of Streptococcus dysgalactiae polyarthritis in lambs during 2005. In June the Ayr Centre recorded the same organism as a cause of septic arthritis in a mule gimmer. This animal was presented for post-mortem examination with a history of hind-leg weakness. While no gross lesions were seen in the spinal cord at necropsy, subsequent histopathology demonstrated lesions likely to be associated with an old abscess. In addition, septic arthritis of the right shoulder and right tarsal joints and a severe chronic mastitis were demonstrated. In each case S. dysgalactiae was isolated on bacterial culture. Interestingly, the group from which this gimmer came had earlier in the year suffered S. dysgalactiae arthritis amongst neonatal lambs. The owner reported that five of these 100 gimmers, had then gone on to develop joint swellings, usually affecting the forelimbs. It is highly unusual for S. dysgalactiae to be associated with arthritis in adult sheep and this report provides further evidence of an emerging disease problem worthy of closer scrutiny.

Nervous system disorders

Louping-ill was confirmed by brain histopathology in a four-year-old Scottish Blackface ewe from Argyll. The condition was also suspected in a five-year-old Scottish Blackface ewe exhibiting tremor and ventriflexion of the neck, on another farm in Argyll. Where brain material is not available in a particular case, the use of serology may assist in the diagnosis of the condition. On this occasion an antibody titre of 1/2560 was detected in blood from the affected ewe, using the HI test. This titre was shown to be wholly due to an IgG antibody fraction, rather than the IgM normally associated with recent infection with the virus. However, by the time clinical signs of louping-ill are identified in sheep, IgM is often replaced, partially or wholly, by IgG.

Two cases of listerial encephalitis were diagnosed in a group of 300 Scottish Blackface gimmers from a flock in Inverness-shire. There was a history of the sheep having access to poor quality silage. In contrast, the same diagnosis was made in a group of gimmers that had eaten only grass for more than two months. Two animals from a large Berwickshire flock were submitted for necropsy following a period of ataxia, leading to recumbency and extreme depression. Listerial encephalitis was confirmed on bacteriology.

Skin diseases

Psoroptes ovis mites were identified in samples from an Aberdeenshire unit. This confirmed sheep scab in a group where a partial, but incomplete, response to treatment with doramectin had been noted three weeks previously.

Skin scabs were submitted to the Inverness Centre from a four-year-old Suffolk ram, suffering from wool loss, scabbing and pruritis on areas of the face, ears, legs, axillae and scrotum. It was reported that there had been no response to systemic tetracycline antibiotics or doramectin. Examination revealed no evidence of ringworm, lice or mites. A profuse growth of Staphylococcus chromogenes was isolated on culture - although it was felt that this represented an opportunistic invader. Similar lesions have been reported over the face and ears of sheep, following extensive midge bites and secondary allergic reaction.