Veterinary Services

A group of 500 lambs was split into groups and housed in preparation for introduction of a proprietary pelleted feed. Before the newly delivered batch feed was placed in the storage bins, the metalwork and piping had been cleaned and a quantity of last season’s pellets was collected.  The pellets had been present within the bins for nearly 10 months and were visibly contaminated with mould.  Despite this, these old pellets were offered to one pen of lambs.

Two days later, several of these lambs had become lethargic, anorexic and appeared blind. Closer examination revealed that the affected lambs had lost the menace reflex, although the pupillary light reflex was retained, and a slow nystagmus was also noted in some lambs.  Eventually, most of the 100 animals in the group were similarly affected; 20 became recumbent and two lambs died after being crushed by others. 

Treatment with B vitamins and antibiotic failed to elicit any clinical improvement.  When two moribund lambs were submitted for postmortem examination, histopathology confirmed toxic-type brain damage in each, and a mild hepatic insult in one animal. Subsequent examination of the remnants of the suspect feed failed to identify potentially toxic moulds or fungi in sufficient quantities to cause disease. However, a presumptive diagnosis of poisoning was made and the case became subject to action by the Food Standards Agency, Scotland. Over the following days, no further lamb losses were reported. Animals in the affected group recovered slowly and returned to normal feeding and growth, although a number were left with visual impairment.

Parasitic diseases

The relatively mild start to the month was associated with an increase in the number of outbreaks of parasitic gastroenteritis (PGE) and fasciolosis. PGE was confirmed in an Icelandic lamb submitted from a small flock in northern Aberdeenshire.  The owner reported that four of 15 lambs had died, despite receiving treatment with raspberry tea.

So-called winter nematodirosis was recorded in four flocks in the area served by Thurso. The condition is commonly identified in the far north of Scotland, where it causes acute-onset scour and deaths in older lambs. On this occasion, lambs in the affected flocks had last been treated with anthelmintic at weaning in September or October.

Generalised and systemic conditions

Systemic pasteurellosis due to P trehalosi was recorded in lambs aged six to eight months on 30 occasions during November. Reported mortality rates ranged from 1 per cent, to as high as 30 per cent in one outbreak reported by Ayr.

Concurrent PGE and trace element deficiency were identified in a number of outbreaks reported by centres. The history of inoculation of the affected lambs with Pasteurella vaccines was variable. In the 10 outbreaks investigated at Dumfries, the affected lambs had reportedly received a full course of vaccination in seven cases, were unvaccinated in two cases, and were of unknown status in one case.

Alimentary tract disorders

Ruminal acidosis was identified in a seven-month-old lamb in excellent body condition, that had been found dead on an Aberdeenshire farm.

Four deaths were reported in a group of lambs that had recently been moved to a stubble field.  A farmer submitted a two-year-old Scottish greyface gimmer for postmortem examination,with a history of progressive weight loss over six months. During this time the animal, which had been purchased as a hogg, had retained its appetite and shown no evidence of scour.  This type of chronic illthrift was said to be a sporadic problem within the flock of 400 ewes on the Scottish Borders farm.

Postmortem examination confirmed gross thickening of the mucosa along the greater part of the ileum, with multiple small abscesses present within the wall of the affected gut. The identification on mucosal smears of acid/alcohol-fast bacilli typical of Mycobacterium avium subspecies paratuberculosis confirmed a diagnosis of paratuberculosis (Johne’s disease).  The condition was known to be present within the herd of suckler cows on the farm, and the owner had previously considered joining a Johne’s disease eradication scheme. Following the diagnosis in the ewe, it was emphasised that in all likelihood, infection would continue to spill over into the flock while it remained uncontrolled among the cattle.

Nervous system disorders

Four hoggs died from a group of 400 that had been purchased on to a farm in the Edinburgh area for finishing. The brain from a submitted six-month-old male Scottish mule lamb showed large areas of fluorescence in the cerebrum when examined under UV light, consistent with a diagnosis of cerebrocortical necrosis. 

Louping ill was diagnosed following neuropathological examination of the brains of two Scottish blackface lambs that had recently been moved to a farm near Perth from the west coast of Scotland.

Skin diseases

Sheep scab was diagnosed on examination of skin scrape samples from sheep on five premises in November, bringing the total number of incidents of the condition recorded in Scotland in 2005 to 49. This compares with 42 incidents at this stage in 2004, and 57 in 2003. One diagnosis was made in a flock from an extensive hill farm in highland Perthshire. Of concern on that occasion was the fact that the sheep grazed a poorly fenced area of hill adjoining several other farms.