Veterinary Services

Dumfries investigated ill thrift in a group of four-month-old lambs by examination of faecal and blood samples. A worm egg count carried out on a bulked faecal sample yielded a strongyle egg count of 4000 eggs per gram. In addition, assay of six blood samples revealed a mean copper result of 5.3umol/l (reference range 9-25umol/l). Copper deficiency is an unusual cause of ill thrift in lambs and SAC C VS suggested that the low copper status could be secondary to intestinal parasitic damage interfering with its absorption.

Parasitic diseases

Liver fluke prediction for winter 2011/2012

Levels of liver fluke disease are expected to remain high and comparable with recent winters.  This summer was wetter and colder than 2010. Maximum temperatures were almost 1ºC below the equivalent figure for 2010, but rainfall was markedly higher during winter, spring and summer compared with 2010. By contrast the winter was milder and the spring warmer than 2010. 

Both rainfall and temperature have an effect on the level of liver fluke infection in the intermediate host of the parasite, the mud snail Galba truncatula. Higher rainfall permits extension of permanently wet snail habitats and establishment of more temporary habitats in flooded and temporary wet areas. However, the lower temperatures will limit the rate of development of the stages of the parasite developing within the soft tissues of the snail. The number of immature stages (cercariae) emerging from snails this autumn and through the winter and spring will determine the level of acute and chronic liver fluke disease suffered by sheep and cattle in the coming months.
Interestingly, the summer of 2003, following which the highest levels of liver fluke disease were recorded in Scotland, had above average temperatures and below average rainfall suggesting that temperature rather than rainfall may have a greater influence on the level of disease. One reason for this may be that the water-table is extremely high throughout Scotland permitting regular flooding events.

SAC Disease Surveillance figures (Figure 3 - see top right-hand side) show a reduction in the number of outbreaks of liver fluke disease during 2011 to date compared with equivalent figures for 2010. Should this trend continue the exposure to the parasite and therefore the number of outbreaks of disease may be reduced compared with 2010. However outbreaks of acute fasciolosis in sheep have recently been recorded in Ayrshire and SAC C VS advises that it is essential that cattle and sheep at risk of disease should receive flukicide treatment and vaccination against Black Disease. Any casualty animals should be submitted for postmortem examination to establish a cause of death and to permit continual monitoring of the prevalence of liver fluke disease in cattle and sheep.

A late outbreak of nematodirosis was diagnosed by Inverness as the cause of diarrhoea and deaths in a group of three-month-old texel-cross lambs. The lambs were dosed with moxidectin four weeks prior to the onset of problems.  Nematodirus battus eggs were detected in significant numbers in three of four samples examined.   SAC C VS notes that moxidectin is effective against Nematodirus battus at the time of dosing but has no persistent effect. 

Generalised and systemic conditions

Edinburgh diagnosed Clostridium perfringens type D disease as the cause of death of three four-month-old texel-cross lambs that died suddenly.  The group was gathered a few days previously for weaning and appeared healthy at that time.  In each case the brain appeared swollen and flattened, with cloudy meninges noted in one case.  Two lambs had soft and haemorrhagic kidneys and both also showed pericardial effusion.  Epsilon toxin was detected in the small intestinal contents of all three lambs and neuro-histopathology revealed changes typical of Cl. perfringens type D enterotoxaemia. Mannheimia haemolytica was also isolated from the brain of the lamb with cloudy meninges.  Type D enterotoxaemia can manifest as sudden death associated with “pulpy kidney disease or as neurological disease due to focal symmetrical encephalomalacia.

Respiratory tract conditions

Pre-sale testing of seventeen shearling tups on the same farm found twelve were positive for antibodies to Maedi-Visna (MV) by the agar gel immunodiffusion test. MV was first diagnosed in this commercial, non-pedigree flock in early 2011.  All the tups were subsequently withdrawn from the sale.  SAC C VS observes that there has been an increase in MV outbreaks in recent years (Ritchie and Hosie, Veterinary Record 2010; 167: 389) and recommends that MV screening should form part of quarantine testing for all purchased tups.

Thurso diagnosed pasteurellosis due to Mannheimia haemolytica and Mannheimia glucosida as the cause of death in a four-month-old north country cheviot ewe lamb that was found dead. The lamb was in good body condition. SAC C VS notes that Manheimia glucosida, (formerly Mannheimia haemolytica serotype 11) is not included in commercial vaccines that provide protection against pasteurella-type infections.

Mammary diseases

St. Boswells diagnosed mastitis and pasteurella septicaemia as the cause of death of a three-year-old Lleyn ewe.  Five ewes from this flock of 2000 had died during the preceding week.  At necropsy the right side of the udder was hard and contained liquid orange/brown material.  Tissues anterior to the udder were oedematous.  Areas of the lungs were collapsed and consolidated.  Mannheimia haemolytica was isolated in pure growth from the udder and Biberstenia trehalosi and Mannheimia haemolytica were both isolated from the lungs and liver.

Nervous system disorders

Listeriosis was diagnosed on histopathology as the cause of right-sided unilateral facial paralysis (Figure 4 - see top right-hand side), nystagmus and lateral recumbency in a Suffolk-cross gimmer submitted alive to Dumfries. Neuropathology revealed multiple micro abscesses in the mid and hind brain. The farmer reported several similar cases each year and SAC C VS provided guidance on control of this disease.