Veterinary Services

The principal metabolic diseases of the pregnant ewe recorded with regularity by SAC VS are hypocalcaemia and pregnancy toxaemia (figure 3 - see top right-hand side).  Whilst the incidence of the former has remained relatively static, the incidence of pregnancy toxaemia appears to vary from season to season.   Following the very poor summer of 2008 there are fears that the poor quality of some forages may contribute to an increase in pregnancy toxaemia during the spring of 2009. 

The diagnosis of pregnancy toxaemia is defined as clinical signs, including anorexia, behavioural changes and blindness, recorded in association with an elevation of serum beta-hydroxybutyrate above 1.2 mmol/l. Pregnancy toxaemia consistently reaches a peak incidence in the month of March.  As a preventative measure the blood-testing of a representative number of ewes at four weeks prior to the start of lambing is recommended.  Where scanning has allowed ewes to be batched on the basis of the number of foetuses being carried, a group target of < 1.0 mmol/l is suggested for twin and triplet-bearing ewes.  Where the prospective litter size is unknown, a lower target of < 0.8 mmol/l is advisable.

Parasitic diseases

Chronic fasciolosis was diagnosed on 17 occasions during the month. Flocks on the west side of the country were affected mainly, but also in areas such as Fife on the East coast.  Towards the end of the month acute fasciolosis caused sudden deaths and acute anaemia in nine flocks in Ayrshire and south-west Scotland, despite flukicide treatment in some cases.  As a result, SAC issued a press release, warning farmers of the risk and suggesting treatment options.  In one such outbreak in Ayrshire, 12 wintering hoggs died suddenly from a group of 60. Measurement of the immature flukes recovered from affected livers indicated that initial infection must have occurred during November.  This was associated with a period of wet and relatively mild conditions likely to be conducive to development of intermediate stages of Fasciola hepatica within the dwarf pond snail Galba truncatula and subsequent emergence of large numbers of metacercariae onto pastures. 

Parasitic gastroenteritis was diagnosed in a group of Scottish blackface hoggs in an Argyllshire flock. The affected farm experienced problems of benzimidazole resistance in the past. The affected group were treated with a group 2 (Levamisole/Morantel) anthelmintic in November. Further anthelmintic treatment and submission of faecal samples for a post-dosing efficacy check was recommended.

A three-year-old billy goat from another Argyllshire farm was presented for postmortem examination with a history of listlessness followed by recumbency.  Parasitic gastroenteritis was diagnosed along with parasitic bronchitis leading to early consolidation of the caudal lung lobes and the presence of Dictyocaulus species lungworms in the bronchial tree.

Generalised and systemic conditions

The two most commonly diagnosed clostridial diseases affecting sheep in Scotland are Cl. perfringens B disease (lamb dysentery) and Cl. perfringens D disease (pulpy kidney).  Both diagnoses are based upon an association of typical clinical history with a combination of characteristic gross pathological changes, histopathological lesions and the detection of clostridial toxins, generally within intestinal contents. 

Over recent years there has been a slight decline in the combined incidence of these conditions (figure 4 - see top right-hand side).  Whilst in 2003 they together accounted for more than 10 percent of diagnosable submissions, by 2007 the figure was less than 6 percent and in 2008 less than 8 percent.  Since both conditions are largely preventable through the routine application of maternal vaccination the more widespread introduction of flock health plans may have contributed in part to this decline.  Farmers should therefore be encouraged to maintain their usual vaccination programmes against clostridial diseases, despite the current pressure that many may feel to cut costs.

Reproductive tract conditions

Two sets of foetuses were submitted to Aberdeen from a group of 27 Suffolk ewes due to start lambing 12 days later.  One set of lambs was autolytic and Salmonella Montevideo was isolated on culture. The other set were born alive and histopathological examination of the brains identified a paucity of myelin and hypercellularity of the white matter core within the cerebrums.  These changes were considered to be consistent with border disease and blood sampling of the affected ewes for border disease virus serology was advised.

Skin diseases

 
Sheep scab was diagnosed in an Ayrshire flock following identification of Psoroptes ovis mites in five of six submitted wool samples.  This was one of nine diagnoses of the condition in Scotland. Most submissions were made for free testing under the Sheep Scab Awareness Scheme.  On this occasion the outbreak occurred in a group of nine-month-old purchased crossbred lambs, despite these having received a pour-on insecticidal product.  Advice was provided on recommended scab control methods. SAC VS suggested that the flock owner should inform the owners of neighbouring flocks so that suitable remedial action could be taken.