Veterinary Services

Nutritional and metabolic disorders

Anaemia in a two-week-old lamb associated with the feeding of bovine colostrum was confirmed on an Aberdeenshire farm.

Unusually this case involved the use of bovine colostrum that had previously been tested negative for antibodies to sheep red blood cells. This test has been available for at least 15 years and during that time has been used very successfully in many flocks. Indeed further investigations have identified only one other case in which colostrum that had been deemed safe by the test was subsequently found to induce anaemia in lambs. Revised advice regarding the feeding of bovine colostrum to lambs is currently being formulated.

Toxic conditions

An interesting demonstration of the pernicious nature of copper as a toxin in sheep was demonstrated when a one-year-old Bluefaced Leicester ram from a Midlothian farm was submitted for necropsy. This animal came from a group of 40 shearlings that had suffered six deaths due to copper toxicity, which was associated with the feeding of a concentrate ration. This concentrate feed had been withdrawn from the group in early February when it was found to contain an excess of copper, complicated by low levels of its’ antagonist molybdenum. The animal examined in late May showed evidence of a haemolytic crisis and was found to have a liver copper level of 14,500 umol/kg and kidney copper of 1,520 umol/kg on a dry matter basis (reference ranges 314-7,850 umol/kg and < 787 umol/kg respectively).

Parasitic diseases

In Scotland the month of May usually sees a substantial rise in recorded outbreaks of nematodirosis, principally due to the species Nematodirus battus. This occurs when rising temperatures cause overwintered eggs to hatch, leading to the simultaneous appearance of large numbers of infective L3 larvae on pasture. When such a mass-hatch of eggs coincides with rising consumption of herbage by juvenile lambs (usually aged 6 to 12 weeks), large-scale outbreaks of nematodirosis are possible. This month a total of 27 such outbreaks were recorded. One interesting case recorded by the Inverness Centre, involved a North Country Cheviot lamb only three-weeks-old. This animal had died after developing a black scour and was found to have a total count of 12,400 N. battus adults and larvae within the small intestine.

Inefficacy of triclabendazole was suspected at the Ayr Centre when a post-dosing fluke egg count revealed that four of five samples contained eggs.

Generalised and systemic conditions

The Ayr Centre reported septicaemia due to Pasteurella trehalosi associated with the deaths of seven hoggs from a group of 90, over a period of some 10 days.

A total of twenty of 400 Texel and Shetland lambs born on a large unit in the north of Scotland died at three to five days of age. Necropsy of one affected lamb revealed signs of generalised septicaemia and necrosis of the liver. Streptococcus dysgalactiae was cultured from sampled tissues.

Alimentary tract disorders

Fourteen outbreaks of lamb dysentery were seen this month, most commonly affecting flocks where the routine vaccination of ewes against clostridial disease had ceased. In one case reported from the Thurso area, 40 lambs of 600 died, showing initial signs of disease during the first two to four days of life.

Two bottle-fed lambs from a smallholding in the Thurso area developed scour. When faecal samples were submitted for investigation, Salmonella dusseldorf was isolated on culture. No further cases were reported in this flock.

A one-month-old Bluefaced Leicester ram lamb was submitted to the Edinburgh Centre, one of several lambs that had appeared to thrive, before sudden loss of condition and death. On examination the lamb appeared thin, with marked abdominal distension. On opening the carcass severe purulent peritonitis was evident, involving the abdominal wall, mesentery and urachus. Bacteriology yielded a profuse growth of Arcanobacterium pluroanimalium - a recognised cause of sepsis in sheep.

Respiratory tract conditions

A number of ewes from an Inverness-shire flock of 600 that were housed for lambing were reported to have a dry, hacking cough and some showed weight loss. When one ewe in poor condition was submitted the majority of the left lung was found to be consolidated and pale grey in colour. Mannheimia haemolytica was isolated in culture from the lung and histopathology showed an acute, exudative broncho to lobar pneumonia and pleurisy. There was no evidence of ovine pulmonary adenomatosis (OPA) or maedi-visna.

Reproductive tract conditions

An abortion submission was received at Edinburgh DSC in which placentitis and associated exudate were noted, along with petechiation of foetal tissues. Although chlamydial or bacterial abortion was suspected, modified Ziehl-Neelsen (MZN) stained smears proved negative for acid-fast organisms and bacterial cultures yielded no significant organisms. Histopathology confirmed suppurative placentitis, vasculitis and thrombosis, again suggestive of enzootic abortion. However, no antigens of Chlamydophila abortus or Coxiella burnetii (Q fever) were recognized by subsequent immunohistochemistry. Although the findings were felt to be suggestive of a Gram-negative bacterial placentitis, no definitive cause has yet been ascertained.

In another case where a final diagnosis was not forthcoming, four aborted lambs were submitted from a flock in Inverness-shire. Acid-fast intra-cellular inclusions were detected in smears from the foetal stomach contents of three of the lambs, but none were detected in smears from the associated placental tissues. Serology for Q fever was later carried out on six ewes and three were found to have titres of 2/8. However it was concluded that this was unlikely to represent recent infection.

A five-year-old ewe from a farm in the Perth area was presented to a veterinary surgeon with inability to rise and was initially thought to be suffering from a metabolic disorder. However, following necropsy Clostridium sordellii was isolated from the uterus and histopathological examinations confirmed severe clostridial metritis.

A review of data relating to abortion submissions collected by SAC VS during the 2005 lambing season in Scotland indicates some interesting trends (click on the PDF link on the right). Toxoplasma gondii has now overtaken Chlamydophila abortus to become the most commonly diagnosed cause of infectious abortion in Scotland. Together these two pathogens account for slightly more than half of diagnosed outbreaks this year. Although still a significant proportion of the total, this is less than the 65% of diagnosed outbreaks attributed to the two diseases in 1998. The most likely explanation for this relative decrease in importance over the last decade is the availability of effective live vaccines to control both conditions.

 Mammary diseases

Mastitis due to infection with Pseudomonas aeruginosa was confirmed in a twelve-month-old housed Dorset hogg on an Aberdeenshire farm, which presented with pyrexia and a hot, painful udder.

Musculo-Skeletal conditions

A further seven cases of polyarthritis due to Streptococcus dysgalactiae subspecies dysgalactiae were recorded in neonatal lambs in Scotland during May. This brought to 20 the total number of flock outbreaks recorded by SAC VS this spring. This compares with two cases reported over the same period last year and four recorded in 2003. Outbreaks were typically seen in lambs between one and three weeks of age. In one outbreak in the Scottish Borders the owner reported that approximately 40 lambs from a group of 400 were affected in one or more joint. In another case from Ayrshire a farmer estimated that 200 to 250 of this year's crop of 3,500 lambs were affected. Since such lambs rarely thrive, this not only represents a major economic blow to the owner, but also a highly significant animal welfare issue.

Streptococcus suis was isolated from the joints of a three-month-old lamb showing septic polyarthritis submitted to the Ayr Centre. The same bacterium was isolated from lung, spleen and a vegetative endocarditis lesion.

Nervous system disorders

A one-month-old lamb was submitted to the Perth Centre with signs of nervous disease. Pasteurella trehalosi was isolated from the brain and neuropathological findings confirmed a bacterial infection. Also at the Perth Centre neuropathological lesions consistent with louping-ill infection were demonstrated in two, three-week-old lambs that had demonstrated clinical signs suggestive of a CNS disorder.

A flock in Wester Ross lost 10 out of 85 homebred hoggs, the majority of deaths occurring over a few days. One animal was seen to be blind and had a high-stepping gait. Post-mortem examination revealed a number of sheep ticks (Ixodes ricinus ) on the carcass. Neuropathology identified a widespread non-suppurative meningoencephalitis. Subsequently the antibody titre to louping-ill virus was shown to be greater than 1/10,240 and louping ill virus was isolated from the spinal cord.

Skin diseases

A Bluefaced Leicester flock near Inverness has suffered intermittent keratoconjunctivitis since the ewes were housed in December. Tetracycline antibiotics resulted in a temporary response, but cases often relapsed. While there was no evidence of chlamydial involvement, Branhamella ovis was isolated from one case and cultures for mycoplasma also proved positive. Further work to identify the mycoplasma species involved is now proceeding.