Veterinary Services

A pedigree Texel ewe showing dullness and anorexia was presented at Ayr for postmortem examination. This was the only animal in a group of around 50 ewes to be affected. Necropsy revealed jaundice, splenomegaly, black kidneys and hepatic necrosis.  Copper poisoning was suspected and confirmed by demonstration of liver copper values of 32,300 umol/kg DM (reference range 314 to 7850 umol/kg DM).  The Food Standards Agency Scotland (FSAS) was informed as this value exceeded the statutory limit for notification.  The animal reportedly had not received concentrate feed for four weeks. 

Aberdeen reported a similar diagnosis in a two-year-old Lleyn ewe submitted for postmortem examination from a local organic unit.  Three other ewes had died in the preceding six days.  In this case the liver copper was 37,100 umol/kg and the FSAS were again advised of the case as a potential on-farm food safety incident.  Postmortem findings in another ewe submitted for examination three days later were also consistent with copper poisoning.  The ewes have been fed an ad lib powdered mineral since the start of the year, which some ewes were observed to gorge on.  Although thought to be copper free, analysis of this mineral mix revealed a copper content of 22 mg/kg.

Parasitic diseases

Disease surveillance figures produced by SAC C VS show the increase in the prevalence of fasciolosis in sheep and cattle in Scotland over the last sixteen years to unprecedented levels in 2008 (figure 2 see top right-hand side).  This rising trend is associated with climate change causing increasing temperatures and higher rainfall. The summer rainfall between April and August 2009 has been more than 25 per cent higher than the same period in 2008 relative to the expected mean, and the temperature has been 0.25 Celcius higher. This has produced ideal conditions for snails and intermediate fluke stages.  SAC C VS anticipate that the number of recorded cases of fasciolosis in sheep and cattle during the forthcoming autumn and will be as high, if not higher, than 2008.  The 2009 figures to date already show an increase of four per cent in percentage diagnoses in cattle compared with 2008 and of five per cent in sheep.  This is likely to result not only in deaths, clinical disease, poor growth rates and liver condemnations, but also in higher levels of subclinical disease in sheep and cattle.

The mild wet conditions prevalent this summer also favoured development of nematode larvae on pasture, and parasitic gastroenteritis (PGE) was easily the most common diagnosis made in sheep during August.  On one organic farm in Ayrshire, PGE was confirmed in four-month-old Scottish blackface and Texel lambs on the basis of elevated trichostrongylid egg counts.  Large numbers of coccidial oocysts and tapeworm (Moniezia spp) eggs were also demonstrated in the faecal samples received. 

Very high trichostrongylid egg counts were also found in samples received from an Argyllshire hill flock despite treatment with a benzimidazole wormer.  Anthelmintic resistance was suspected and appropriate advice given.  Similar high trichostrongylid egg counts and the presence of large numbers of coccidial oocysts consistent with PGE were recorded in a group of lowland lambs grazing lush pasture in Ayrshire.     

Generalised and systemic conditions

Four three-month-old lambs died in an organic flock of 700 ewes in the Scottish Borders during one week.  The lambs were neither vaccinated nor treated for worms, despite their grazings being used by ewes and lambs during the previous year.  At necropsy, a total worm count of 2,400 Teladorsagia species and 3,500 Nematodirus species worms were detected.  This worm burden was considered significant, but not likely to be the cause of death.  Epsilon toxin was detected in the intestinal contents and a diagnosis of Clostridium perfrigens type D enterotoxaemia (pulpy kidney) was made.  In addition liver tissue analysis revealed a deficiency in selenium.

Clostridium perfringens type D enterotoxaemia was also the cause of death in a two-year-old Scottish blackface gimmer examined at Edinburgh.  There were a number of sudden deaths in the group over the previous month.  The flock was fully vaccinated as lambs and boosted pre-lambing.  Although no epsilon toxin was detected on this occasion, neuropathological findings were indicative of focal symmetrical encephalomalacia.

Alimentary tract disorders

Thirteen ewes died suddenly in a flock of 900 Cheviot ewes on a Borders holding.  All the deaths occurred in the group of ewes grazing improved pasture, with none within the hill group.  A three-year-old ewe and a four-month-old lamb were submitted to St Boswells.  Similar lesions were detected in both animals with the intestine dilated by gas and blood-stained fluid.  These lesions were consistent with sporadic intestinal hemorrhagic syndrome or ‘red gut’.  Sheep grazing on readily fermentable herbage such as very lush pasture are susceptible due to the rapid transit of digesta through the stomach.  This allows fermentation in the large intestine, which increases in size and becomes unstable and in some sheep sudden complete torsion results in rapid death. Prevention may be achieved by limiting the grazing of sheep on such pastures, although this may run counter to the production objectives of the flock.

Three deaths occurred in a group of pedigree border Leicester ram lambs wormed at three weekly intervals.  The lamb submitted became recumbent and died despite antibacterial therapy.  All the affected lambs that died were seen to have submandibular swelling for a few days prior to death.  Postmortem examination revealed a necrotic sinus on the left side of the pharynx consistent with a dosing gun injury. 

Respiratory tract conditions

Ovine pulmonary adenocarcinoma (OPA) was diagnosed in a gimmer in good body condition. Necropsy revealed lung infiltration with neoplasic tissue and pneumonic consolidation of caudal areas. Mannheimia haemolytica  was isolated from the lung tissue and histopathology confirmed OPA with extensive acute secondary pneumonic pasteurellosis.  Although classically associated with dyspnoea and chronic loss of condition in older ewes, it is not uncommon for ewes of any age to die from pasteurellosis secondary to relatively mild OPA changes within the lungs.

Nervous system disorders

Two similar deaths were reported in five-month-old lambs from a lowground Ayrshire flock.  The affected animals became recumbent, showed paddling of all four limbs and circled when lifted upright.  Neuropathology revealed extensive meningo-encephalitis as denoted by micro-abscesses and thick mixed inflammatory cell perivascular cuffs centred on the cerebellar peduncles and hind-brain, consistent with listeriosis.

A three-month-old lamb from South Uist was submitted for postmortem examination. It displayed progressive neurological signs for a period of two weeks prior to euthanasia.  On neurohistopathology, the neurological signs were attributed to delayed swayback, although the liver copper level at necropsy fell within the normal reference range.

Cerebrocortical necrosis (CCN) was diagnosed in a three-month-old Suffolk cross lamb found dead. The Aberdeenshire unit reported six lamb deaths in the preceding ten days out of a total of approximately 150 lambs.

Skin diseases

Samples were received from a farm where 15 of 100 lambs were reported to have scabby lesions on their muzzles and ears.  While Dermatophilus infection was suspected, a pure growth of Staphylococcus aureus was isolated and the presence of orf virus confirmed by PCR.