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News and Reports |
- These are among matters discussed in the disease surveillance report for November 2006 from Scottish Agricultural College Veterinary Services (SAC VS)
NOVEMBER saw the high mean temperatures continue to result in the warmest autumn on record. However, November 2006 was the wettest ever recorded, with the overall total rainfall being 155 per cent of the average for 1961 to 1990; some weather stations in western Scotland recorded well over double the average rainfall. These conditions continued to favour parasitic larval development and spread.
The State Veterinary Service lifted restrictions on the movement of poultry in East Lothian on November 18 as no further outbreaks of Newcastle disease (pigeon variant) had been found in the preceding 30 days.
SAC VS co-hosted a very successful Scottish Animal Health and Welfare conference in Pitlochry on November 29 and 30. The conference attracted over 150 delegates. Four themes ran through the presentations: awareness of disease problems; quantifying the cost, in both economic and welfare terms; understanding the disease or condition; and using that understanding to develop effective controls. Presentations made and abstracts of presentations and posters given are available on the SAC's website at www.sac.ac.uk/consultancy/veterinary/conferencereports/sahw/
SAC reminded farmers to treat cattle for liver fluke in the autumn and winter.
CATTLE
Parasitic diseases
Chronic liver fluke problems were a common diagnosis across Scotland during
the month. In Caithness, the condition was noted in eight beef suckler herds
affecting cows and calves. In some cases animals had been treated in
mid-summer with a flukicide but had been reinfected in the wet weather of
September and October.
Also in Caithness six groups of cattle, aged six to 18 months, were diagnosed with parasitic gastroenteritis (PGE). In one case calves still with their dams had been treated with avermectin in October but had remained at grass and had been re-infected. The good grazing season during autumn 2006 encouraged farmers to leave cattle at grass for longer.
Generalised and systemic disorders
The seasonal rise in the number of outbreaks of salmonellosis was noted
this month. An outbreak of salmonellosis due to infection with
Salmonella Dublin was confirmed on an Aberdeenshire beef suckler
unit. The owner reported 42 cows calving in the preceding two weeks, with a
sudden dramatic increase in mortality in the neonatal period. Eight deaths in
calves in the first week of life were reported. Colisepticaemia was initially
suspected but not confirmed at postmortem examination of the first calf
submitted. A light growth of S Dublin was eventually obtained on
enrichment from the liver. However, a profuse growth of S Dublin was
obtained from multiple organs from a second (stillborn) calf submitted two
days later.
A two-month-old Holstein heifer died after treatment for pneumonia. The farm had lost calves due to acute pneumonia the previous year. Vaccination resulted in no improvement. Pneumonia was confirmed at postmortem examination at Dumfries, but cultures were sterile. S Dublin was isolated on enrichment, and histopathology confirmed changes in the lung, liver and spleen that were consistent with salmonella septicaemia.
Alimentary tract disease
A Jersey herd in Dumfriesshire lost four calves in one week due to acute
scour. A four-day-old heifer was submitted for postmortem examination. It had
been born outside and had been given two litres of colostrum by stomach tube.
The calves remained with the cows for 24 hours before being moved into single
pens. The navels were not routinely treated. There were no gross changes at
postmortem examination, but histopathology revealed an extensive abomasitis
and enterotyphlocolitis. Tests for Escherichia coli K99
were positive and, in addition, bovine viral diarrhoea (BVD) virus
was isolated from the spleen in cell culture. The zinc sulphate turbidity
(ZST) test result was 5 suggesting inadequate colostrum intake.
Respiratory tract diseases
Infectious bovine rhinotracheitis (IBR) was the most common
cause of pneumonia diagnosed across Scotland in November. Clinical signs
included various combinations of ocular discharge, nasal discharge, coughing
and fever. Adult cows also suffered a significant milk drop. Diagnosis was
confirmed by the demonstration of IBR virus in ocular or nasal
swabs by immuno fluorescence. The involvement of IBR was also
suspected in some cases of fatal pneumonia, but although histopathological
examination of such animals showed a tracheitis suggestive of IBR,
it was not possible to demonstrate the virus in the postmortem material.
A six-month-old Simmental cross calf from a unit in Angus was submitted for postmortem examination with a history of death despite a period of treatment for pneumonia. Examination revealed an appreciable volume of straw-coloured pleural fluid, pulmonary congestion and oedema. In addition, a 2 cm diameter abscess was found within the wall of the left ventricle of the heart. Subsequently, bovine herpesvirus type 1 (BHV-1) was detected in the lung by the fluorescent antibody test (FAT), and Histophilus somni (Haemophilus somnus) was isolated on culture of the abscess.
A seven-month-old Simmental cross Charolais heifer died suddenly but had been a `poor doer' for some time. The weaned calves were housed one week previously and there had been some coughing in the group. The udder was congested and haemorrhagic, which was confirmed on histopathology, but there was no evidence of inflammation. There was sub cutaneous and intermuscular oedema at the base of the udder and in both hindlegs between the hip and the stifle area. There were a large number of petechial and ecchymotic haemorrhages in the laryngeal and tracheal area. The tracheal mucosa was intensely congested, as was the bronchial mucosa. There were petechial epicardial haemorrhages present. The lungs were congested. FATs on the tracheal mucosa were strongly positive for BHV-1, but there was no diphtheritic material in the trachea or evidence of a secondary bacterial pneumonia. The udder and systemic cultures were sterile. Histopathological findings were of terminal circulatory failure and hypoxia.
A six-month-old Limousin cross calf from a holding in Fife was submitted alive but moribund for postmortem examination. The farm had a history of BVD virus-associated disease and a number of other `poor doing' calves were currently present on the unit. An acute broncho pneumonia was identified on postmortem examination, from which a pure growth of Mannheimia haemolytica was isolated on culture. In addition, a blood sample tested by ELISA for antigen to BVD virus produced a result fractionally below the positive cut-off for the test. Advice was given on screening other calves in the same group for evidence of BVD virus.
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Congenital defects were diagnosed as the cause of death of two calves from different farms in the Borders. The first calf was a one-month-old Hereford that died of congestive heart failure and hepatocellular degeneration resulting from a patent foramen connecting the two ventricles. The second calf was a 10-week-old Charolais that had severe bilateral hydronephrosis resulting from a blockage of the urethra. From the history received, both appeared to be isolated incidents.
Skin diseases
A two-year-old Highland heifer had a haemorrhagic, large mass on the lower
left neck area, below the jugular furrow. The mass had enlarged over the
previous couple of months. Histopathology showed that it was composed of
dense, fibrous tissue, much of which was organised granulation tissue
containing an intense pyogranulomatous inflammatory infiltrate. At the centre
of the inflammation were eosinophilic club bodies. The findings were typical
of actinobacillosis, but it was not possible to demonstrate the bacteria
within the lesion.
SHEEP
Nutritional and metabolic disorders
Two 18-month-old Cheviot rams were submitted to Inverness as part of an
ongoing welfare investigation. Both were cachectic and weighed 31 kg and 26 kg
respectively. The liver selenium was found to be 0·4 mg/kg dry matter
(DM) in the first ram and 0·23 mg/kg DM in the
second ram (reference range 0·9 to 3·5 mg/kg DM). In
addition, one animal showed evidence of chronic fasciolosis and the other
PGE.
Parasitic diseases
The carcases of four ewe lambs were submitted to Edinburgh from a farm with
40 Shetland and Icelandic sheep. These lambs had begun to scour some five days
earlier. The animals had been vaccinated and dosed with avermectin in May and
with diclazuril six days previously, with little effect. The lambs weighed
from 11 to 17 kg. Examination of all four lambs confirmed scouring and a
moderate to severe verminous pneumonia. Muellerius capillaris and
Dictyocaulus species worms were present in the respiratory tract and
there was also evidence of severe enteric parasitism due principally to tricho
strongylid nematodes.
Nematodirosis was diagnosed on seven occasions in November. St Boswells reported the condition in a five-month-old Romney cross lamb submitted for postmortem examination from a holding where several cases of diarrhoea and death had occurred in a group of 3000. A total worm count of the small intestinal contents was attempted, but the helminths present, of which Nematodirus species predominated, were too numerous to count.
Generalised and systemic conditions
A total of 42 separate incidents of systemic pasteurellosis due to
Pasteurella trehalosi infection were recorded in Scotland in
November, the month that traditionally sees most cases of this condition. This
brought to 92 the number of outbreaks recorded in 2006, compared with 50 cases
diagnosed at the same point in 2005, of which 30 were in November
(Fig 1). All eight SAC
VS centres reported cases during the course of the month. In the great
majority of cases the initial presenting sign was sudden death, with lambs in
the age range of six to eight months most commonly affected. Reported
mortality in November ranged from 1 per cent to as high as 25 per cent. The
pathology was typical, with necrotic erosions in the pharynx and upper
oesophagus (Fig 2) and swollen
oedematous lungs with widespread focal haemorrhages
(Fig 3). Concurrent
PGE, trace element deficiencies and serological evidence of
exposure to tickborne fever were identified in a number of the outbreaks
reported by the centres.
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SAC VS comments that the risk factors suggested to be of importance in predisposing lambs to systemic pasteurellosis are folding on rape or kale, and movement to improved pasture. The association of outbreaks with periods of changeable weather, particularly prolonged, wet weather, may be of greater significance in 2006. The weather in Scotland during November was particularly wet, albeit with temperatures that were significantly higher than average. It would be consistent with the theory of climatic stress as a risk factor that the spell of inclement weather coincided with a surge in diagnoses of systemic pasteurellosis.
Alimentary tract disorders
Twenty deaths were reported in a group of 1000 recently housed lambs on an
Aberdeenshire unit. The owner reported that the lambs had been offered hay and
only a small amount of concentrate pellet. However, when two lamb carcases
were submitted for examination there was a substantial amount of grain within
the rumen, and the ruminal pH of less than 5·0 was consistent with a
diagnosis of acidosis.
The carcase of a seven-month-old Texel cross lamb that died suddenly, was submitted to Dumfries. On postmortem examination, a large quantity of bloodstained ascitic fluid containing fibrin clots was found within the abdomen. In addition, the caecal mucosa was thickened, inflamed and ulcerated, and the contents were bloody. Clostridium sordellii was isolated from the caecum in pure culture. Histopathology, which may have defined the significance of this bacteriological finding, was not possible in this case.
Two three-year-old Scottish blackface ewes were submitted alive to Dumfries. They had been in good body condition when put to the ram, but had wasted during the following six weeks and now weighed only 31 and 36 kg, respectively. Blood samples were taken antemortem and albumin levels of 9 g/l and 13 g/l were measured (reference range 28 to 34 g/l). During postmortem examination, lesions of the pigmented form of Johne's disease were seen, and Ziehl-Neelsen-stained smears of the ileum were positive for acid-fast bacteria.
Reproductive tract conditions
In the first recorded abortions of the season, Thurso diagnosed
Bacillus licheniformis infection in material submitted from a flock
of 60 Suffolk ewes, six of which had lost lambs.
A shepherd in the Scottish borders reported that two Charollais ewes had aborted in a group of 40 due to start lambing in December. No significant lesions were evident in the placentas, but the fetal livers were friable, and abdominal fluid was bloodstained. Campylobacter fetus subspecies fetus was isolated from the fetal stomach contents.
Musculoskeletal conditions
A Scottish blackface ewe was reported to have dropped dead in front of a
shepherd while being gathered from a hill near Edinburgh. At postmortem
examination, there was found to be tearing of the musculature of the left side
of the neck adjacent to vertebrae C4 to C7, with extensive associated
haemorrhage within the muscle, connective tissue and skin. The neck seemed
unstable at C6/C7 and there was a large haemorrhage on the ventral side of the
cervical spinal cord at C4 to C7 and on the underside of the brainstem. The
findings indicated that the ewe had suffered severe trauma to the neck but had
apparently been able to stand for a short period before spinal shock, collapse
and death occurred.
Nervous system disorders
Two Scottish blackface ram lambs from the same group were both found
recumbent within 24 hours on a holding near Edinburgh. Both remained bright
and alert, and retained withdrawal reflexes in the hindlegs, but neither was
able to stand. Examination of the first lamb revealed a large abscess in
association with vertebra L4 pressing on the spinal cord. In contrast,
histopathological examination of the brain and spinal cord from the second
lamb revealed a severe, widespread, non-suppurative meningomyeloencephalitis
consistent with a protozoal aetiology, most likely sarcocystosis.
Skin diseases
Chorioptes ovis mites were detected in scrapings from scabbed skin
lesions over the fetlock and metacarpal area of a Scottish blackface hogg from
an Inverness-shire flock that had died of pasteurellosis.
GOATS
A faecal sample was submitted from an eight-year-old neutered male goat that was reported to have suffered from scouring and pyrexia for three days. The other goat on the holding was unaffected. There was no evidence of underlying significant parasitism, and both Salmonella and Campylobacter species cultures were negative. However, Yersinia pseudotuberculosis was isolated on culture of the faeces.
PIGS
Generalised systemic diseases
A case of porcine dermatitis and nephropathy syndrome (PDNS) in
Ayrshire stimulated a classical swine fever alert on account of the gross
postmortem findings of multiple petechiae in the kidneys, peripheral lymph
nodes and bronchial tree. The five-month-old Landrace cross Large White pig
was euthanased after developing bloody diarrhoea, weakness on its legs and
respiratory signs. Two other pigs in the herd of 40 had died in the previous
week. Samples collected by the State Veterinary Service were tested for swine
fever with negative results. Histopathology subsequently demonstrated diffuse,
chronic glomerulonephritis and vasculitis affecting multiple tissues including
the intestinal mucosa, consistent with a diagnosis of PDNS.
Haemorrhagic skin lesions were absent in this particular case.
An outbreak of polyserositis, pneumonia and rhinitis among weaners on one unit yielded Haemophilus parasuis and/or Streptococcus suis serotype 7 from affected tissues. The piglets were in good body condition, but had shown dullness, lethargy, sneezing and coughing for 24 hours. As this unit was enzootic pneumonia-free, piglets were euthanased for diagnostic purposes. It appeared that the two agents were co-pathogens in the outbreak.
S suis serotype 14 was diagnosed as the cause of septic polyarthritis in weaners derived from two supply farms. Mortality was low but there was significant morbidity among the group of 190 weaners.
Respiratory tract diseases
A breakdown of enzootic pneumonia was confirmed in six-week-old piglets
that were showing coughing and illthrift. The unit had been repopulated in May
2005. The source of infection was unclear.
Alimentary tract disorders
Two 25-day-old piglets were euthanased and submitted from a unit suffering
from acute diarrhoea and deaths in the preweaning period. The mucosae of the
stomach and small and large intestine were congested with widespread
petechiae, and the gut contents and faeces were fluid in nature.
Histopathology showed acute haemorrhagic necrotising enteritis in both
piglets. Analysis of intestinal contents for clostridial toxins by
ELISA confirmed the presence of both alpha and beta toxins,
consistent with the presence of Clostridium perfingens type C.
SAC VS notes that the diagnosis of clostridial-type enteritis is
unusual in piglets of this age as this condition is generally confined to
piglets less than 14 days old.
Outbreaks of diarrhoea in growing and finishing pigs on several units were associated with either Brachyspira hyodysenteriae or Brachyspira pilosicoli solely, or either of these agents in combination with Lawsonia intracellularis and/or Salmonella Typhimurium.
Parasitic diseases
Four faecal samples from diarrhoeic adult sows were all positive for
Oesophagostomum dentatum eggs. The counts from the sows from one unit
were 1100 and 3200 eggs per gram of faeces (epg) and from the other 200 and
900 epg. O dentatum is a recognised cause of colitis and diarrhoea in
pigs.
BIRDS
Poultry
Impaction of the crop with a tangled mass of long, fibrous material was
found in a free-range layer. Several birds in the particular paddock had lost
weight and had died or been culled. Further inquiries revealed that the grass
in the paddock had become very long and had been cut, but the cut grass had
not been removed.
Marek's disease was diagnosed in a chicken from a small flock where several birds had developed paralysis. No abnormalities of the sciatic nerves were noted on gross postmortem examination, but histopathology revealed focal and locally diffuse lymphocyte and plasma cell infiltration consistent with a diagnosis of Marek's disease.
Aortic rupture was confirmed in a male turkey that had been found dead. The owner had reported five deaths in the group of 400 birds, all in excellent body condition and almost ready for slaughter.
Gamebirds
Deaths due to a combination of coccidiosis and gapeworms were recorded in
red-legged partridges that were still in release pens. Ten of 60 birds had
died in the previous few days, but there had been no problems with previous
batches and these birds were on a fresh site.
Diffuse pallor and substantial enlargement of the spleen were noted in a pheasant that had been shot and submitted to a processing plant. The liver was also slightly enlarged. Although the gross appearance was not typical of avian tuberculosis, Ziehl-Neelsen-stained smears demonstrated many acid-fast bacilli typical of Mycobacterium avium. Histopathology of the spleen subsequently showed that much of the parenchyma had been replaced by pale, eosinophilically staining material, presumed to be amyloid, with multifocal infiltrations of large epithelioid macrophages throughout the tissue. Small to moderate numbers of acid-fast organisms consistent with Mycobacterium species were visible in sections of both the liver and spleen.
Pigeons
The owner of a recently established flock of 50 fantail pigeons submitted
two of his birds for examination. Several pigeons had been lost over the
previous few days and others appeared lethargic and anorexic. Both submitted
birds were in poor body condition and had empty crops. The main postmortem
finding in one bird was considerable enlargement of the liver, which appeared
friable and showed diffuse pale degeneration throughout. The kidneys in the
pigeon were similarly pale, enlarged and soft. The other submitted bird showed
a fibrinous pericarditis and enlargement of the kidneys. A heavy growth of
S Typhimurium phage type 2 was isolated on culture of tissues from
both birds. Advice on the zoonotic risk of the infection was relayed to the
owner of the pigeons, and the divisional veterinary manager of the Animal
Health Office was informed.
MISCELLANEOUS MAMMALS
Dogs and cats
Aberdeen observed Sarcoptes scabiei mites in a skin scrape from a
12-week-old puppy purchased from a puppy farm, which presented with an intense
pruritus. Aberdeen also examined a three-year-old German shepherd dog found
dead. Cardiac postmortem examination confirmed the presence of right
ventricular hypertrophy.
Horses
A pony in a small trekking stable had severe scour and was depressed for
three to four days. Thurso demonstrated numerous strongyloid eggs in faeces
and cultured S Typhimurium DT 41. There were no other
animals affected and no human involvement. The horse made a full recovery
after being treated for worms.
Hares
A female juvenile hare was found dead on a beef and sheep unit in
Inverness-shire, on which several hares had been found dead over the summer.
The hare was in poor body condition and had a massive coccidial oocyst burden.
Severe coccidiosis was confirmed on histopathology.
This summary is produced by SAC Veterinary Services
and is based on reports from its centres in Edinburgh, Perth, St Boswells, Ayr
(Auchincruive), Dumfries, Aberdeen, Inverness and Thurso
SAC Veterinary Services monthly reports are available online at
www.sac.ac.uk/consultancy/veterinary/publications/monthlyreports/2006
from the first of every month
Related articles in The Veterinary Record:
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