Veterinary Services

Nutritional and metabolic disorders

Four centres noted an increase in submissions for the routine screening of flocks for trace element deficiency and parasitic infection. The SAC considers that this may reflect the increased use of flock health and welfare plans, which frequently include a regular assessment of trace element and parasite status. The benefit of this procedure was highlighted by Dumfries where severe cobalt deficiency was diagnosed in groups of ill thriven weaned lambs on the basis of low individual and mean vitamin B12 serum activity. One group of lambs also showed selenium deficiency and concurrent parasitism. The latter was diagnosed on the basis of pepsinogen values of up to 3.1 iu/l, (normal range <1 iu/l).

A seven-month-old Scottish blackface-cross castrated lamb was submitted to Edinburgh for necropsy. It was from a group of 200 lambs where 10 per cent were described as lean, depressed and blind on the day after being dosed for liver fluke and worm infection. The lambs were on good grazing and were not receiving any supplementary feeding or minerals. At necropsy the lamb was lean, with horn separation at the white line and skin lesions on the brisket. Internal examination revealed localised areas of pneumonic change and a paleness of the liver. Analysis of a blood sample collected prior to euthanasia revealed significant hepatic damage and pre-renal uraemia. Subsequent histological examination of the brain showed varying degrees of spongy change consistent with hepatic failure. Histopathology of the liver revealed changes highly suggestive of ovine white liver disease due to cobalt deficiency and a measurement of liver vitamin B12 falling below detectable levels confirmed this diagnosis. Urgent supplementation of the rest of the group was indicated along with a recommendation to treat lame animals.

Toxic conditions

A four-year-old, North Ronaldsay ewe from a small hobby flock was submitted after being found recumbent, dyspnoeic and bloated. The carcase was markedly jaundiced, the liver was small and pale, and the kidneys were swollen and dark, as was the urine. Copper poisoning was confirmed with liver and kidney copper levels of 32,400 umol/kg (normal range 0-787) and 16,400 umol/kg (normal range 314-7850) respectively.

Parasitic diseases

Dumfries confirmed infection with Haemonchus contortus on four occasions. This parasite is usually considered to be rare in Dumfriesshire. In all four cases the history was of ill thrift or sudden deaths. Anaemia and hypoalbuminaemia were present in most cases, with packed cell volumes and serum albumin values recorded as low as 0.07 l/l, (normal range 0.26 – 0.36 l/l) and 10 g/l, (normal range 28-34 g/l), respectively. On one farm the identification of H contortus worms in ill thriven lambs at necropsy, was linked back to problems last spring among ewes pre-lambing. At that time, a group of 200 Scottish blackface ewes showed a dramatic loss of condition in last month before lambing, despite being moved onto clean, fresh grazing. There were consequential losses of ewes and neonatal lambs. The worm egg counts were low in two ewes submitted for postmortem after lambing and no Haemonchus worms were found at necropsy. Histopathology however had suggested that the problem was associated with massive worm challenge. The SAC considers that when the ewes were examined postmortem they had developed an immunity to the parasite. Subsequently the lambs became infected when they grazed the contaminated pasture after weaning. The flock owner was now advised to treat all sheep on the farm with an avermectin class anthelmintic and to quarantine dose all incoming stock. This treatment should break the H. contortus lifecycle as the parasite does not over-winter well in colder climates, surviving mainly as inhibited L4s within the sheep.

Twelve outbreaks of fasciolosis were recorded in Scottish flocks. Figure 3 (see top right-hand side) shows the typical postmortem picture of acute fasciolosis. Following a particularly wet summer in Scotland, the SAC anticipates higher than normal fluke activity this autumn and winter. Examination of data from the last 15 years (see Figure 4 - see top right-hand side) shows how the incidence of fasciolosis in sheep and cattle peaked in the early part of this decade at the same time as average rainfall in Scotland also rose. However, in recent years the incidence in sheep has started to decline, while that in cattle has remained elevated. One explanation is that sheep farmers have responded to the risks of severe, acute liver fluke disease by dosing prophylactically. In contrast, with the disease presentation in cattle either being chronic or possibly an incidental finding in older animals, less, prophylactic dosing of cattle may be carried out. This is particularly the case for dairy herds.

Generalised and systemic conditions

Systemic pasteurellosis was confirmed in a six-month-old lamb found dead at an Aberdeenshire farm. Two deaths occurred in a batch of 184 lambs that came home ten days previously. Postmortem findings of generalised blood splashing and carcase congestion suggested a septicaemia and Bibersteinia trehalosi was isolated from the lung and liver. The same diagnosis was made in flocks from Sutherland and Inverness-shire. In both these cases the vaccination history of the affected lambs was either uncertain or known to be incomplete. Stress due to recent transport and handling was considered a predisposing cause.

Interestingly only six outbreaks of systemic pasteurellosis were recorded in Scotland, compared with 30 during October 2006. Although FMD related restrictions may be responsible for at least part of the reduction, anecdotal reports from around the country suggest the condition was less common this autumn than has been the case in recent years.

Nervous system disorders

The owner of a flock in Angus found eight lambs dead, recumbent or ataxic over a period of a week. One lamb appeared to have drowned in a stream. A live lamb, submitted for examination, was pyrexic and showed a poor menace reflex, mild ataxia and a fine head tremor. Following euthanasia, neurohistopathology confirmed changes indicative of acute louping ill. Blood serology from the animal identified an immunoglobulin titre of 1/10240, principally IgM confirming recent infection.

Skin diseases

Caseous lymphadenitis was diagnosed in two flocks in Ross-shire. This brought to 36 the total number of diagnoses in Scotland between January and October 2007, compared to 21 over the same period in 2006.