Veterinary Services

 
Three deaths occurred in a group of 180 crossbred lambs after dullness, ataxia and stilted gait were noted in approximately 40 of the younger animals in the batch.  This occurred approximately four days after treatment of the 800 lambs on the premises with multivitamin, an anticoccidial and an insecticide product.  Two of the affected lambs were submitted to Ayr. Dehydration, abomasal ulceration and other non-specific changes were noted at gross postmortem examination.  However these lambs were also found to have elevated liver selenium values and histopathological evidence of nephrosis and toxicity.  On this basis a tentative diagnosis of selenium toxicity was made, compounded by abomasal ulceration and renal nephrosis of unknown aetiology. The remainder of the affected animals made an uneventful recovery.  

Parasitic diseases

As predicted in the news release referred to above, the hatch of Nematodirus battus larvae, associated with rising temperatures, resulted in 35 outbreaks of clinical nematodirosis.  In an Ayrshire flock four deaths occurred over two days amongst three-month-old grazing lambs.  Postmortem examination of a casualty lamb revealed enteritis associated with very large numbers of adult and larval Nematodirus battus.  Pasteurella trehalosi (Pasteurella haemolytica type T) was also isolated from liver and lungs indicating terminal systemic infection. Nematodirosis was also diagnosed in an Argyllshire flock in which seven-week-old lambs were scouring despite anthelmintic treatment.

Nematodirosis was confirmed on five units in Aberdeenshire. In all cases the history was of lambs found dead, with some scour reported amongst surviving lambs.  Mortality varied from three to eight per cent. Variable coccidial oocyst counts were also recorded in association with the nematode worm burden, although speciation is required to determine the proportion of pathogenic species present.

Chronic fasciolosis due to the liver fluke Fasciola hepatica was diagnosed in two Argyllshire flocks. In one affected flock deaths were reported in thin hill ewes showing "bottle jaw" despite treatment with a flukicide.  As parasite resistance to treatment could not be ruled out further investigations were initiated.

Generalised and systemic conditions

Three sudden deaths occurred amongst four-week-old lambs born to unvaccinated ewes.  A diagnosis of enterotoxaemia due to Clostridium perfringens Type D was made by demonstration of epsilon toxin in bowel filtrate.  Neuropathology was also carried out as another lamb in the group showed nervous signs. Histological examination of the brain showed severe perivascular serum leakage as well as infiltration of mononuclear inflammatory cells (focal symmetrical encephalopathy) caused by the epsilon toxin of C. perfringens.  SAC C VS recommended a programme of routine vaccination for the flock.

Enterotoxaemia due to Clostridium perfringens Type D was also diagnosed in a three-week-old Scottish blackface lamb from an Argyllshire island flock. The dams of affected lambs were bought as cast ewes and were not vaccinated against clostridial disease.

On an Ayrshire farm three deaths of five to six-week-old Texel lambs occurred over a period of five days.  In this case the ewes of affected lambs were vaccinated against clostridial diseases. However lesions consistent with pulpy kidney disease were evident at postmortem examination in an affected lamb and epsilon toxin of C. perfringens was detected in bowel filtrate. 
Postmortem examination of lambs submitted from flocks experiencing significant neonatal lamb mortality problems resulted in a variety of diagnoses. These included pneumonic pasteurellosis due to infection with Mannheimia haemolytica, colisepticaemia, starvation and hypothermia in lambs born to hoggs where a mortality rate of 50 per cent was recorded, cryptosporidiosis and joint ill due to infection with Streptococcus dysgalactiae.

Reproductive tract conditions

In 2010 the owners of 423 sheep flocks submitted material to their local SAC C VS Disease Surveillance Centre to assist in the investigation of an abortion outbreak.  This compared to 416 flocks over the same period in 2009.  This season the two most commonly diagnosed causes of abortion in Scottish flocks were Toxoplasma gondii and Chlamydophila abortus infections (Fig 4 - see top right-hand side).  Together these accounted for more than 60 per cent of the diagnosed infectious sheep abortion outbreaks in 2010, which is slightly more than the equivalent figure for 2009.  Diagnoses of both conditions continued to be made during May, with three incidents of toxoplasmosis and one of C. abortus.  From this year’s results, other common causes of abortion included the bacterial organisms Campylobacter species, Listeria species and Salmonella species.   The "Other" category, was responsible for more than ten per cent of outbreaks where a diagnosis was made, and is composed of those pathogens that are encountered more sporadically This includes border disease virus, and bacteria such as Arcanobacterium pyogenes, Bacillus licheniformis, Yersinia, Staphylococcus and Streptococcus species. 

Mammary diseases

Staphylococcus aureus and Streptococcus dysgalactiae were isolated from milk samples submitted to Dumfries from a sheep flock suffering an outbreak of mastitis.
Staphylococcus caprae was isolated from a milk sample collected from a British Toggenburg goat with recurrent mastitis.  This organism was found to be beta-lactamase positive, which explained a reported poor response to treatment.

Nervous system disorders

Two flocks in Aberdeenshire experiencing problems with joint ill submitted lambs displaying clinical signs of arched backs, progressing rapidly to recumbency.  These live lambs retained withdrawal and panniculus reflexes.  In addition there were no cranial nerve deficits and the suck reflex was intact.  Infection around the atlanto-occipital joint was suspected and confirmed on postmortem examination, although the prior use of antimicrobials prevented the recovery of pathogenic bacteria.

Louping ill was diagnosed on serology as the cause of acute death following nervous signs in a group of tick (Ixodes ricinus) infested hoggs from an Ayrshire island flock.  The same diagnosis was made serologically and on the basis of neuropathology of an affected animal in an Argyllshire hill flock of Scottish blackface ewes. The history was of convulsions, tremor, nystagmus and ataxia.  SAC C VS provided advice on tick control and vaccination was suggested as neither was practised on the affected farms.