Download SAC C VS Monthly Report for November 2014

SAC C VS Monthly Report for November 2014
OVERVIEW

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Leptospiral milk drop in dairy cows
Pseudomonas aeruginosa mastitis in a cow
Systemic pasteurellosis in lambs
Encephalopathy due to water deprivation/salt
poisoning suspected in weaned lambs
Biliary cystadenoma in a red deer hind

GENERAL INTRODUCTION
The month was generally unsettled but mild with fewer
frosts than average. Rainfall overall was 79 per cent of
average, with the north-west receiving less than half the
normal rainfall amount. Sunshine amounts were 94 per
cent of average overall. Eastern areas were dull;
whereas, the west received above average sunshine.
Scottish poultry producers were advised to stay vigilant
following an outbreak of avian influenza on a duck
breeding farm in East Yorkshire.
DISEASE ALERTS
The following conditions were reported by SAC C VS
disease surveillance centres in March 2014. Given
similar climatic and production conditions, they could
also be important this year.

Iodine deficiency in aborted calves

Diarrhoea in neonatal calves associated with
low zinc sulphate turbidity levels

Sheep abortions due to Chlamydophila,
Toxoplasma and Campylobacter

Hypocalcaemia in ewes

Listeriosis in sheep
CATTLE
Generalised and systemic conditions
Ayr diagnosed milk drop due to leptospirosis in a dairy
herd. Twelve cows from a herd of 160 experienced a
sudden onset drop in milk production, with no other
clinical signs observed. Acute and convalescent blood
samples from two affected cows showed seroconversion
to Leptospira Hardjo on ELISA testing. In addition,
quarterly bulk milk testing demonstrated recent elevation
in antibodies to L. Hardjo. The affected animals had
access to a stream shortly before the first case of milk
drop was observed. SAC C VS considered that this
natural water course may have been the source of
infection.
Respiratory tract diseases
There was an increase in the number of carcases and
samples submitted to investigate outbreaks of
pneumonia since housing. Lungworm infection continued
to be diagnosed this month. Aberdeen diagnosed
parasitic pneumonia in a group of 30 recently-housed,
weaned calves. Six calves had signs of respiratory
disease and one of these died. At postmortem
examination large numbers of lungworms were seen in
the airways, the cranioventral lung lobes were
consolidated and the caudal lobes emphysematous.
Mannheimia haemolytica was recovered from lung
lesions.
Outbreaks of viral pneumonia were commonly
diagnosed. Bovine herpes virus 1 (BHV-1) was most
frequently identified, diagnoses being made by PCR
testing of swabs (ocular, nasal or nasopharyngeal) or by
postmortem examination, where typical findings were
marked tracheitis with a necrotic diphtheritic membrane
and secondary lung consolidation.
Ayr diagnosed acute pneumonia in a five-month-old
Aberdeen Angus-cross bull calf that died within an hour
of antibacterial and anti-inflammatory treatment. At
postmortem examination red consolidation of the cranial
lung lobes, interstitial emphysema and emphysematous
bullae of the caudal lung lobes were present. Bibersteinia
trehalosi and Histophilus somni were recovered from lung
lesions, but screening for respiratory viruses (BHV-!,
parainfluenza virus 3 (PI3V) and respiratory syncytial
virus (RSV)) by PCR was negative. Histological
examination of the lungs identified acute suppurative
pneumonia and pleurisy of bacterial aetiology, consistent
with infection by the isolated organisms. Acute
bronchointerstitial pneumonia was also present. SAC C
VS commented that while this is not a specific change,
viral infection is considered the most likely cause.
Although RSV and PI3V were excluded by PCR testing
another virus (e.g. bovine coronavirus) could be involved.
Other possible causes include toxicity and acute
systemic disease. Acute interstitial pneumonia is a well
recognised condition in feed-lot cattle in the USA, where
it is thought to be associated with 3-methylindole and is
most common in calves with previously damaged lungs
(Loneragan and others, 2001). In this case there was
evidence of chronic lung damage in the form of airway
fibrosis.
Reproductive tract conditions
Aberdeen diagnosed Campylobacter fetus abortion in a
four-month-old foetus from a beef suckler cow, the first to
abort from a group of one hundred. The farmer reported
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a high proportion of barren cows at scanning. The foetus
was autolytic and partially predated with the stomach and
intestinal tract missing. A pure growth of C. fetus was
recovered from lung tissue. SAC C VS advised that when
C. fetus is isolated from an aborted calf and there is
evidence of infertility in the herd, the possibility of
venereal campylobacteriosis should be considered.
Musculo-skeletal conditions
Perth diagnosed ulcerative, necrotising dermatitis and
cellulitis in a recently purchased three-year-old HolsteinFriesian heifer, from a group of 60 with milk drop and
condition loss after calving. Two animals died and others
had swollen limbs. The heifers were fed a total mixed
ration, which on analysis was deficient in protein. Recent
blood testing of the cohort revealed consistent
hypoalbuminaemia and urea values below reference
range. At postmortem examination, body condition was
poor and a soft swelling was seen around the right hock.
An abscess discharging thick yellow pus was present in
one quarter of the udder. Severe erosive lesions were
found in the interdigital skin of all four feet with complete
loss of the interdigital skin in some areas (Fig 1).
energy balance, was identified. SAC C VS considered
that this would likely have resulted in compromised
immune defences and a review of nutrition was advised.
Mammary diseases
Dumfries diagnosed Pseudomonas aeruginosa mastitis
in a cow that died suddenly. This was the third cow in two
weeks to die within five days of drying off. On the
affected farm, cows were routinely treated with dry cow
antibiotic tubes and teat sealant at dry off. At postmortem
examination the eyes were sunken, there was a blue
tinge around all teats and teat sealant was present in the
teat canals. Three of the quarters had fibrinous and
fibrinopurulent material present within the gland and
there was extensive consolidation and inflammation in
one quarter (Fig 2).
Fig 2. Pseudomonas aeruginosa mastitis in a cow
Fig 1. Erosion of interdigital skin in a cow
Three of the limbs had purulent cellulitis and there were
areas of significant under-running of the skin with
purulent tracts. Trueperella pyogenes was recovered
from lesions. Screening for bovine viral diarhoea virus by
PCR proved negative. Histopathology revealed extensive
necrosis and ulceration of the interdigital skin associated
with mixed bacterial colonisation and active cellulitis.
SAC C VS commented that, at this chronic stage, the
original insult causing the breach of epidermal integrity
could no longer be determined. Fusobacterium
necrophorum infection or treponemes (associated with
digital dermatitis) were possible differential diagnoses
and examination of the feet of all heifers in the group was
advised. In addition fatty liver, indicative of negative
A pure, heavy growth of P. aeruginosa was recovered
from all quarters. SAC C VS advised that this organism is
usually associated with contaminated water. Cases postdrying off have been associated with hygiene issues such
as pre-warming syringes in water, hosing dirty udders
prior to dry cow tube infusion and in cows lying in wet
conditions in the days immediately following drying off. P.
aeruginosa was not isolated from samples of udder
cloths, hoses, hose water or teat dips.
SMALL RUMINANTS
Nutritional and metabolic disorders
Edinburgh diagnosed ruminal acidosis in a six-month-old
Scottish blackface tup from a hill-grazing group of 150.
Six were found dead since the introduction of barley
three days earlier. At postmortem examination the rumen
contained wet fibre and grain and had a pH of 3.5.
Thurso and St. Boswells also reported sudden deaths of
lambs due to ruminal acidosis following the recent
introduction of barley and Inverness reported similar
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losses after lambs were moved to a stubble field. SAC C
VS recommended introducing high carbohydrate feeds
slowly over a few weeks and, when not feeding ad lib,
ensuring sufficient trough space for all animals to access
the feed at the same time.
Parasitic diseases
Parasitic gastroenteritis was diagnosed on 26 occasions
during November 2014 compared to 19 occasions during
the same period in both 2012 and 2013. The increase
may reflect the mild weather that continued throughout
most of November and allowed continued hatching of
eggs and development of larvae to the infectious L3
stage.
Generalised and systemic conditions
November saw the expected peak of sudden deaths in
lambs due to systemic pasteurellosis with a total of 13
diagnoses. St. Boswells diagnosed the condition on four
farms and in all cases B. trehalosi was cultured from both
lung and liver (Table 1). Two flocks had used pasteurella
vaccine, one involved purchased animals of unknown
vaccine status and one flock had not vaccinated. B.
trehalosi can be found as a commensal organism in the
nasopharynx and tonsils of healthy sheep. Changes in
diet and weather are thought to be predisposing factors
in multiplication of the organism and spread of bacterial
emboli into the circulation (Donachie, 2007).
Aberdeen also isolated B. trehalosi from viscera of a
yearling goat. The cranial lung lobes showed severe
bilateral consolidation and the liver contained numerous
pale foci, less than 1 mm diameter, on the surface and
throughout the parenchyma. These lesions are
secondary to occlusion of blood vessels by bacterial
emboli and, particularly if found together with
oesophageal ulceration, suggest B. trehalosi infection.
Alimentary tract disorders
Perth diagnosed intestinal adenocarcinoma in a ewe that
had shown wasting, wool loss and malaise for six weeks
before death. At postmortem examination a large volume
of orange peritoneal fluid with fibrinous peritonitis and
serositis was seen. The jejunum was thickened, with an
area of stricture. Histopathology revealed extensive
deposits of fairly well-differentiated, mucoid, columnar
epithelial cells infiltrating the submucosa of the small
intestine. These changes were consistent with invasive
scirrhous intestinal adenocarcinoma. The primary tumour
site was not represented in the fixed tissue examined, but
tumour cells were clearly infiltrating via the lymphatics.
SAC C VS commented that intestinal adenocarcinoma is
a well-described, debilitating condition in sheep, which is
sometimes misdiagnosed as chronic peritonitis, as
invading neoplastic cells evoke a marked fibrous reaction
and adhesions. Hereditary factors, environmental
carcinogens such as contained in bracken, or exposure
to herbicides have been suggested as possible
predisposing causes (Løken and others, 2012).
Table 1: Significant history and necropsy findings in lambs diagnosed with systemic pasteurellosis
Age
Breed
6
months
8
months
8
months
Highlander
Number
of
deaths
4/400
Number of animals
examined
Texel
1/18
1
Suffolk X
Texel
14/400
2
7
months
Scottish
blackface
6/275
1
4
Nervous system disorders
Aberdeen diagnosed encephalopathy in a group of 100
weaned lambs that were gathered and separated
according to body condition. Approximately 50 poorer
lambs were given a trace element drench and housed,
the remainder returning to grass. Forty-eight hours
later many of the lambs appeared lethargic and the
concentrate feed had not been eaten. Fifteen-to-twenty
Significant postmortem findings
Pulmonary congestion and interstitial oedema,
oesophageal ulceration
Multiple adhesions between lung and parietal pleura, lung
consolidation, restrictive pericarditis
Pleural, pericardial and peritoneal effusions (one animal
only), lung congestion and interstitial oedema, congested
liver
Subcutaneous, pleural and pericardial haemorrhage,
congested lungs, mottled liver
showed signs of head-pressing and apparent
blindness. One lamb was submitted live was in lateral
recumbency showing signs of opisthotonus. The pupils
were dilated and there was no menace response.
There was evidence of parasitic gastroenteritis with a
strongyle egg count of 12,400 eggs per gram, but
diarrhoea was not present. There were no significant
findings
on
gross
postmortem
examination.
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Neuropathology revealed severe, acute to sub-acute,
generalised vacuolar leuko-encephalopathy and focal
lesions of cerebrocortical necrosis, which were
probably secondary to generalised brain swelling.
Histopathology of liver and kidney did not reveal any
changes to explain spongiform changes in the brain.
Water deprivation/salt poisoning was considered a
differential diagnosis and has been previously
suspected in cases of encephalopathy in weaned
lambs (Scholes and others, 2005).
PIGS
Generalised and systemic conditions
Aberdeen diagnosed bacterial endocarditis in a group
of seven-week-old cross-breed pigs that developed
acute onset dyspnoea and cyanotic extremities, dying
one to two days after showing clinical signs. At
postmortem examination of one animal there was an
excess of fluid in the thoracic cavity, interlobular
oedema and patchy, dark-red pulmonary congestion.
The heart appeared dilated and globular and there was
an endocarditis with numerous small abscesses along
the edge of the left atrio-ventricular valve.
Streptococcus suis serotype 2 was isolated from the
lung, liver and heart in mixed bacterial growths and
almost pure growth from the heart valve.
Alimentary tract disorders
Aberdeen examined six pigs that were submitted live
from a holding, in which about five per cent of the
animals had ill-thrift. There were 3000 animals on the
unit and batches were of 300 to 400 animals. At
postmortem examination of three eight-week-old and
three 11-week-old piglets, five animals had enteric
changes with prominence of the lymphoid tissue of the
ileum and thickening of the terminal ileum. There were
raised white discs of lymphoid tissue over the serosa
of the colon and the colon content was pasty. Findings
were more pronounced in the older two animals; the
spiral colon having copious liquid content. Laboratory
testing and histopathology confirmed proliferative
enteropathy in the ileum due to Lawsonia intracellularis
infection. In the older pigs proliferative enteropathy
affected both ileum and colon, with spirochaetal colitis
due to Brachyspira pilosicoli also affecting the large
intestine.
BIRDS
Poultry
Inverness suspected infectious laryngotracheitis (ILT)
was the cause of respiratory disease in a flock of 60
layer hens. The outbreak started in a show bird, which
recovered after treatment with enrofloxacin. Thirty
birds were subsequently purchased and several of
these developed respiratory disease. Eighteen birds
died and 12 birds showed clinical signs of respiratory
disease. At postmortem examination an 18-week-old
layer was lean and had an extensive biting louse
infestation. Pathological lesions were confined to the
upper respiratory tract and included a reddened infraorbital sinus containing sanguineous mucous and an
inflamed tracheal mucosa that was covered by serosanguineous mucus and tissue debris. Histological
examination of the infra-orbital sinus showed chronic,
active inflammatory changes, with significant numbers
of mononuclear cell infiltrates in addition to exudative
processes. The trachea showed evidence of a chronic
granulomatous tracheitis with a largely intact
epithelium. Viral inclusions were not apparent, but the
gross and histological changes in the respiratory tract
were suggestive of ILT, which was complicated by
bacterial infection of the sinuses. ILT is caused by
Gallid herpesvirus 1, a pathogen that remains
infectious for several weeks outside its host and
causes latent infections. All ages of fowl are
susceptible. SAC C VS advised vaccination to avoid
further losses.
Ayr examined three ten-day-old birds from a broiler
unit. At postmortem examination one bird had an
enlarged spleen and all three birds had enlarged
bursae of Fabricius. Enterococcus hirae was isolated
from all three birds. Enterococcus species are a
normal part of the microflora in the intestinal tract of
poultry but can cause disease, usually secondary to
another infection. E. hirae is most commonly seen in
either septicaemia/bacteraemia with focal symmetrical
encephalomalacia in chicks (broilers and layers)
between three- to eight-days-old or vegetative
endocarditis with right-sided heart failure in slightly
older broilers/broiler breeders, most commonly around
16-20 days old.
Cage and Aviary Birds
Perth found multiple foreign bodies in a three-year-old
Humboldt penguin (Spheniscus humboldti). The bird
was lethargic, in poor condition and regularly
regurgitated its food. On radiography a mass was seen
in the proventriculus and gizzard. At postmortem
examination there was a large bundle of straight twigs,
about 22 cm long and 7 cm in diameter, obstructing the
proventriculus and gizzard. Just below the
oesophageal opening, two small fish were seen on the
twigs. There were erosions, covered with thick mucus,
on the mucosa of the proventriculus and gizzard and
the intestines were empty. Ingestion of foreign bodies
is not uncommon in penguins and this penguin had a
persistent habit of pica, having previously ingested
many foreign bodies.
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MISCELLANEOUS
Dogs
St Boswells identified an intestinal torsion affecting a
65 cm section of the jejunum in an eight-week-old
West Highland white terrier. The puppy had been
found dead at 06-00, despite showing no obvious
clinical signs three hours previously. The affected
section of gut was clearly demarcated and deeply
congested (Fig 3). The lumen contained bloody
material and there was a moderate volume of strawcoloured peritoneal effusion. Torsion of the long axis of
the mesentery is considered rare in dogs and cats
(Brown and others, 2007).
increasing number of deaths. Terminal convulsions
had been seen. The carcase was in good condition
and the stomach well filled. Multiple necrotic lesions of
les or equal to 1 mm were found throughout the liver
parenchyma. Liver tissue tested positive for RHDV-2
by PCR. RHDV is endemic and can cause high
mortality, but the circulation of non-virulent strains in
some rabbit populations is protective (Forrester and
others, 2009). Local veterinary practices were alerted
to the possible risk to pet rabbits.
Perth diagnosed coccidiosis in a male hare, the sixth to
be found dead on a farm since the previous May. The
farmer had noticed an increase in the local hare
population and several carcases were seen throughout
the summer and autumn. At postmortem examination
the anus and genital openings were blocked by a thick,
sticky plug of faeces. Extrusion of the penis revealed
faecal material in the urethral opening. The large
intestine contained thick fluid material and the bladder
was dilated with a large amount of brown urine, which
could not be expressed. One of the renal pelvices
appeared slightly dilated. Coccidial oocysts were not
seen in a sample of intestinal content. However,
histopathology revealed that many intestinal crypts
were almost obliterated by large numbers of
developing coccidia, with segmental areas of complete
mucosal collapse (Fig 4).
Fig 3. Intestinal torsion in a West Highland white
terrier.
Deer
Inverness examined a liver from a shot red deer hind
(Cervus elaphus). Vesicular liver lesions were seen at
evisceration, and incisions into two lesions released
over four litres of either brown-coloured or bloody fluid.
The liver contained cysts of differing wall thickness
with cyst diameters from under 1 cm to over 10 cm,
with larger cysts having a cavernous lumen.
Histopathology revealed extensive fibrosis which
replaced most of the parenchyma, and contained
scattered bile ducts and islands of hepatocytes.
Multiple cyst-like spaces were lined by a single layer of
cuboidal to flattened epithelial cells resembling biliary
epithelium. The histological appearance resembled
biliary cystadenoma, a benign biliary neoplasm. There
was no evidence of Echinococcus tapeworm cysts.
Wild animals
Dumfries diagnosed Rabbit Haemorrhagic Disease
Virus type 2 (RHDV-2) in a young wild rabbit,
submitted by a member of the public who noticed an
Fig 4. Coccidiosis in a hare
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Feature – Tickborne Diseases
Reports of increased tick numbers and geographical
spread over the past decade have led to concerns that
tickborne disease is more common.
The sheep tick Ixodes ricinus is the only species native
to Britain associated with transmission of disease.
Disease is associated with peaks of tick activity, which
are temperature- and humidity-dependent. Warmer,
wetter conditions can allow ticks to be active in most
months of the year. The tickborne pathogens of most
concern are Louping-ill virus, Babesia divergens,
Anaplasma phagocytophilium and Borrelia burgdorferi.
Louping-ill virus causes neurological signs and death
in a wide range of species including sheep, cattle, red
grouse and people. High mortality may occur when
immunologically naïve animals are introduced to a tickinfested area. Losses can be minimised by the use of
louping-ill vaccine in sheep.
A. phagocytophilium causes tickborne fever of sheep
and cattle. Infection causes immunosuppression and
an increased susceptibility to secondary infections,
including tick pyaemia. Naïve sheep and cattle may
abort when exposed to infected ticks. The main
methods of disease prevention are avoiding exposure
of pregnant animals and tick control by the use of
ectoparasiticides.
Tickborne
fever
may
be
underdiagnosed due to the lack of a commercially
available serological test.
Babesiosis (‘redwater’) is a disease of cattle caused by
the protozoan parasite B. divergens. The disease
rarely occurs in herds originating from infected areas.
Susceptible older cattle may become ill, or even die
due to a haemolytic crisis, when exposed to infection.
Lyme disease, caused by B. burgdorferi bacteria, can
cause serious disease in humans, particularly if not
identified early. It may also affect companion animals
including dogs, cats and horses. Wild rodents are
important for the transmission of the disease.
There were 173 diagnoses of tickborne disease by
SACCVS from 2009 to October 2014. Louping-ill was
the most common diagnosis at 69 per cent, babesiosis
at 12 per cent and tickborne fever at 10 per cent. Tick
pyaemia accounted for the remaining diagnoses. Lyme
disease cases were not included as they rarely affect
farmed species.
Continued surveillance is necessary to determine if
climate change and rising tick numbers lead to an
increase in reports of tickborne disease in farm
animals, domestic pets and humans.
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