UK Pig Disease Quarterly Surveillance Report - May 2004
By Veterinary Laboratories Agency - This report monitors trends in the major endemic pig diseases and utilises the farmfile and VIDA (Veterinary Investigation Disease Analysis) databases. The report is compiled using disease data gathered by the network of 15 VLA regional laboratories which carry out disease investigation in the field.
![]() Jan - Mar 2004 - Published May 2004 Contents OVERVIEW (here) NOTIFIABLE DISEASES ZOONOTIC DISEASES ENDEMIC DISEASES |
Highlights: Third Quarter 2003
- National pig population may stabilise this year after several years of decline
- ZAP initiated salmonella investigations starting to take place
- Yet again, PMWS identified as the major issue affecting pig health.
Overview
The Meat and Livestock Commission Economics (www.mlceconomics.org.uk), Pig Market Outlook: 04/2 April 2004, provides an overview of the pig sector. Pig prices fell throughout January to around 100p/kg dw (GB Deadweight Average Pig Price: DAPP) before rising by 9p/kg to some 3p/kg better than one year previously. The UK breeding herd began to stabilise in 2003 after five years of contraction. The December 2003 figures were only one percent down on a year earlier. However, slaughter pigs were down 10 percent over the year, reflecting the deterioration in average sow productivity. In addition, declining inpig gilt replacement and maiden gilt numbers suggest that breeding sow numbers will continue to fall during the first half of 2004. Higher feed costs continue to adversely affect profit margins, and lack of investment remains a chronic problem.
Notifiable Disease:
No suspect incidents of swine fever investigated.
Zoonotic Diseases and Food Safety
POTENTIAL FOOD SAFETY INCIDENTS:
There were no reports of potential food safety incidents involving pigs.
SALMONELLOSIS AND SALMONELLA ISOLATIONS:
Salmonella isolates: Salmonella enterica serovar Typhimurium again predominated with unremarkable antimicrobial susceptibility patterns. Many pig isolates of Salmonella Typhimurium do not demonstrate the 05 antigen, unlike those of other species. Definitive types (DTs) of Typhimurium
included 193, 104A, U288 and 93.
Salmonella incidents:
Typhimurium DT93 occurred in two 10-
week-old pigs on a completely outdoor
unit. A quarter of rearing pigs on another
unit died with Typhimurium infections.
Postweaning multisystemic wasting
syndrome (PMWS) was again a
significant finding in many of the
salmonella incidents.
Two initial farm visits and one follow-up
visit were made under the ZAP scheme
initiative. One visit resulted after 86% of
the meatjuice ELISAs from the unit were
positive. The unit is a contract finisher
receiving pigs from five different sources.
Results indicated that a Group B
salmonella infection was persisting on the
unit rather than being brought in with the
pigs. Rodent control and improvement of
cleansing and disinfection were identified
as areas for urgent attention.
The second investigatory visit again
involved a contract finisher. Pigs were
received from 12 sources, all of which
were outdoor herds. Cleansing and
disinfection were only performed once a
year although the system was run on an
all-in/all-out basis. Other identified risk
factors included poor buildings, a high
incidence of PMWS during the finishing
period, and also overworked and
demoralised staff. It was suggested that
sampling of pigs on arrival at the unit
would identify sources of infected
animals.
A follow-up visit to a unit with a previously
high ZAP score found that overall
mortality had dropped from 9% to 1.5%.
However, these pigs were still excreting
salmonellas in at least 30% of the pens.
The next ZAP results are awaited with
interest.
BRUCELLOSIS:
Brucellas were not isolated under the
surveillance initiative to provide evidence
that pig herds remain free of Brucella
suis; an organism that has never been
isolated from pigs or hares in the UK.
STREPTOCOCCAL INFECTIONS AND DISEASE:
First quarter diagnoses of streptococcal
incidents are illustrated over five years
(vertical bars represent 95% confidence
limits):

% of submissions submitted with Streptococcal infections
The percentage of submissions with
streptococcal infections increased
significantly in 2000 following the upsurge
of PMWS and porcine dermatitis and
nephropathy syndrome (PDNS). The dip
in 2001 is attributed to few carcase
submissions during the FMD outbreak but
the diagnosis rate is now stable at around
7% of submissions. The continuing
predisposing presence of PMWS is
illustrated in this report.
The Wellcome Trust Sanger Institute has
received funding to sequence the
genome of Streptococcus suis. The work
is nearly complete and the sequence is to
be published in a peer-reviewed journal.
The genome is approximately 1.7 Mb in
size with a G+C content of around 40%.
Streptococcus suis isolates: Twenty-five Streptococcus suis isolates
were serotyped this quarter:

Over half of these were Streptococcus suis serotype 2 compared with proportionally fewer in previous quarters:
Quarter 1st | 1st 2003 | 2nd 2003 | 3rd 2003 | 4th 2003 | 1st 2004 |
Serotype 2 as % of isolates | 25.6 | 46.1 | 23.1 | 28.0 | 52.0 |
Streptococcus suis incidents
There were 11 incidents of Streptococcus
suis infection; four (36.4%) were serotype
2. There were three incidents of serotype
3 infection and single diagnoses of
serotype 1, 4, 8 and untypeable. It was
noted that seven of these incidents (64%)
had underlying PMWS/PDNS.
Two of the serotype 2 incidents involved
typical meningitis cases, but unusually
one of these involved pigs from ten to 23
weeks-of-age. The other two outbreaks
both involved respiratory disease with
underlying PMWS. The three S.suis
serotype 3 incidents all involved
respiratory disease as commonly
reported previously. One outbreak had
concurrent PMWS and another PDNS.
The disease outbreaks, where 4, 8, and
untypeable serotypes were isolated, had
PMWS. In one of these, Glasser’s
disease was confirmed and S.suis
serotype 8 was a secondary isolate. The
other two incidents were of respiratory
disease with S.suis isolated and other
respiratory pathogens identified. The
final incident was suspected Glasser’s
disease but surprisingly S.suis serotype 1
was isolated rather than Haemophilus
parasuis. Similar previous incidents are
reported but associated with S.suis
serotype 14.
Other streptococcal infections
Streptococcus dysgalactiae equisimilis
was involved with disease in two groups
of neonatal piglets. Both cases were
predisposed by trauma. In one, rough
flooring was judged to have caused skin
lesions over the limb joints leading to
polyarthritis. S.equisimilis was isolated
from the affected joints. The other was
due to a poor teeth clipping technique
leading to tooth root infection. Welfare
advice was given.
ENDEMIC DISEASES – SUBMISSIONS:

PIG-RELATED QUARTERLY SUBMISSIONS 2002-2003

Note: ‘diagnostic’ refers to initial submission in an incident
Total submissions were lower mainly due
to previous completion of non-diagnostic
project work. Carcase diagnostic
submissions and specimens (primarily
submitted for a differential diagnosis)
were at their highest since foot-andmouth
disease in 2001. The ‘diagnoses
not reached’ category, where reasonable
testing was possible on diagnostic
submissions, was unremarkable when
compared with data for the previous three
years.
POSTWEANING MULTISYSTEMIC WASTING SYNDROME (PMWS)/
PORCINE DERMATITIS AND NEPHROPATHY SYNDROME (PDNS):
Diagnoses of PMWS - as a percentage of
diagnostic submissions tested - remain
high at 23%, but are down on the same
quarter of 2003 (26%), and 2002 (33%).
This is, in part, attributed to a decreasing
need to confirm clinical diagnoses. The
widespread presence of porcine
circovirus type 2 (PCV-2) associated
diseases continues to exacerbate and
precipitate many disease conditions
making control and treatment difficult.
The high mortalities associated with
some outbreaks and increased culling are
demoralising for farm staff.
Despite the widespread occurrence of
PCV-2 there are still herds experiencing
their first recognised cases. One such
herd, which had been closely monitored
and previously shown no clinical or
pathological signs of PMWS/PDNS, had
an increased mortality rate and PMWS
was suspected. The findings of wasting,
enlarged inguinal lymph nodes, stomach
ulcers, pulmonary interlobular oedema
and pallor were confirmed as associated
with PCV-2 infection.
On an indoor unit mortality increased in 7
to 10-week-old pigs with signs reported of
scour, illthrift and respiratory disease.
Histopathology confirmed the presence of
PCV-2 associated disease for the first
time. The disease had affected 100 of
1100 pigs and resulted in the death of 50.
Disease was associated with
pasteurellosis including pleurisy and
bronchopneumonia. Mortality reduced
rapidly to between 2% and 3% following
antimicrobial therapy.
On a small unit of just 12 sows, wasting
and deaths were reported in several
litters preweaning. PMWS was first
observed at 6-weeks-old despite weaning
at 9 to 10 weeks of age. Various lesions
were seen in the 6-week-old pigs
including enteropathy, lymphadenopathy,
and polyserositis.
Diagnoses of PDNS were far less
common than PMWS with first quarter
rates remaining fairly stable at between
3% and 4% of diagnostic submissions for
the years 2002 to 2004. A single
diagnosis may be misleading as
illustrated on one unit where increasing
mortality resulted in 20 of 250 16-weekold
pigs dying acutely within one week. A
single pig was initially submitted for
necropsy, and Glasser’s disease
(Haemophilus parasuis) was diagnosed.
Subsequently a further three pigs were
submitted and all were confirmed as
having PDNS.
ENTERIC DISEASE:
There was only one confirmed swine
dysentery incident in which one percent
mortality was reported in 16-week
finishers. This follows the annual trend of
declining diagnoses over the previous
five years:

% of submissions diagnosed with Swine Dysentry
Lawsonia intracellularis infection was
more frequently reported than swine
dysentery. One outbreak of
haemorrhagic enteropathy caused 14
deaths in finishers over a short period.
Affected pigs showed severe pallor due
to anaemia. A second serious incident
involved 90% of Gloucester Old Spot
growers that showed dysentery, weight
loss and sudden death. Gross and
histopathological findings confirmed
classical lesions of porcine intestinal
adenomatosis.
Gastric ulceration is a common
subclinical condition in finishing pigs but
clinical disease is usually sporadic. The
exact pathogenesis is still unknown. An
outbreak presenting as illthrift with
vomiting in an AI boar stud was
interesting because one typical casualty
showed histological evidence of
helicobacter infection associated with
chronic gastric ulceration and
oesophageal stenosis with marked
muscular hypertrophy. Other noninfectious
factors were thought to be
contributory, particularly reduced fibre
intake following a move from straw-based
pens to fully slatted accommodation.
Coccidiosis due to Isospora suis is well
recognised as a cause of diarrhoea in
sucking pigs. In contrast, clinical disease
due to Eimeria species is rarely reported
and most strains are considered relatively
non-pathogenic. A 7-month-old boar did
however die from Eimeria-associated
necrotic enteritis a few days after
purchase. The timing and the parasite’s
pre-patent period suggested that coccidia
must have arrived with the animal as a
latent or incubating infection rather than
picked up from the new farm
environment. Other recent purchases in
the same group remained unaffected.
RESPIRATORY DISEASE:
Percentage of submissions diagnosed
with respiratory disease (excluding PRRS
and PCV-2 associated disease) were
similar this quarter to the same quarter in
2000, 2002 and 2003:

% of submissions diagnosed with Pneumonias and Pleurisy
Pasteurella multocida was the most commonly diagnosed (19) cause of respiratory disease and this is partly attributable to it being more readily identifiable than other respiratory pathogens. P.multocida was isolated with avian-like H1N1 influenza virus from lungs submitted to investigate respiratory disease within one week of weaning.
Some 70% of weaners were affected but with minimal mortality. A problem of growth check, wasting and coughing affecting around 25% of growers was investigated in pigs 5 to 15 weeks old. P.multocida and Actinobacillus pleuropneumoniae (App) were isolated and there was histological evidence of PMWS.
Incidents of pneumonia due to App as a percentage of diagnostic submissions were up this quarter (3.4%) on the same quarter last year (2.4%). An outbreak of respiratory disease in which 20% of 3 to 6-month-old pigs were affected with 3% mortality was again multifactorial. On this occasion swine influenza virus was isolated with App but without histopathological evidence of PCV-2 or PRRS. In another outbreak, mortality increased from 0.5% to 3% in pigs that were the first to follow a programme of partial depopulation and treatment for App. Serotype 8 App was isolated from typically affected lungs. On another unit A.pleuropneumoniae infection killed 7/800 pigs aged 14 weeks, and a further 60 pigs were ill. The unit had used an autogenous APP vaccine but apparently without success.
Quarterly diagnoses of enzootic pneumonia remain at a low level, in part attributable to introduction of vaccination in recent years:

% of submissions diagnosed with enzootic pneumonia
This quarter there was a reduction in
diagnoses of PRRS, which may in part
result from the lack of a quick, cheap and
effective diagnostic test. The use of
vaccines for PRRS (one is a live
attenuated vaccine and the other two are
inactivated) may result in greater difficulty
interpreting serological results. These
vaccines all became available in the UK
in September 2000. An outbreak of
respiratory disease in 4 to 5-month-old
finishers, with an increase in mortality
from 2% to 10%, was investigated by
serology. Seroconversion to PRRSV was
demonstrated.
Two less common causes of respiratory
disease were diagnosed this quarter.
Actinobacillus suis was isolated in
septicaemic distribution from 4-week-old
pigs that had a sudden rise in mortality
associated with purpura, respiratory
distress, and polyserositis. A sow 11-
weeks in-pig was necropsied after a few
days of inappetance, lethargy and
dyspnoea. There was a severe
polyserositis from which Haemophilus
parainfluenzae was isolated. This
organism is a commensal of the human
upper respiratory tract but has been
reported to cause a Glasser’s-like
disease in pigs.
Swine Influenza:
Continuing surveillance of influenza virus
isolates has not identified significant
changes in circulating strains:
Isolates obtained January to March 2004:
Received | Positive (%) | |
Submissions | 33 | 3* (9.1) |
Samples | 96 | 4 (4.2) |
* avian-like H1N1 x2; HIN2 x1 |
REPRODUCTIVE DISEASE:
Fetopathy diagnoses, regardless of
whether the cause was identified, show a
steady upward trend from 2000 despite a
concurrent decline in the national sow
population:

% of submissions diagnosed with fetopathies
Provisional numbers of the first quarter
submissions for abortion and nonabortion
reproductive disease, and the
non-diagnostic rates for both categories,
are given in the following tables:
Quarter | No of Submissions | |
Abortion | Non-abortion | |
1st | 14 | 37 |
Quarter | Diagnosis not reached | |
Abortion | Non-abortion | |
1st | 8 (57%) | 11 (30%) |
The ‘diagnosis-not-reached’ figure for
abortion submissions is higher this year
than it was in the same quarter of 2002
and 2003, but is based on fewer
submissions. The diagnostic rate for
non-abortion reproductive disease is
apparently better than for the previous
two years. No single aetiology appeared
to dominate diagnoses in either category.
Project OD0214 - Isolation and
characterisation of leptospires in pigs:
PCR and culture of kidneys is currently in
progress at VLA Weybridge and has
already resulted in successful isolation of
Leptospira Bratislava.
MUSCULOSKELETAL DISEASE:
An outbreak of lameness affecting pigs
aged from approximately 6 to 12 weeks
was investigated. The farm had a total of
9,000 piglets and growers, and within this
age group it was estimated that about 5%
of pigs were affected. Clinical signs
included ‘shifting lameness’ particularly of
the hind limbs, stiff gaits, arched backs, a
preference for ‘dog sitting’, and
recumbency. This had resulted in
reduced feed intake and subsequent
reduction in growth rate. Two batches of
pigs were necropsied prior to a farm visit.
Reduced bone density was identified in
all the carcases and involved the long
bones, but notably also the flat bones of
the skull, ribs and vertebrae. The ribs
were easily bent, and cortical bone of the
long bones was thin. A single pig
fractured the distal tibia. Affected pigs
were also hypocalcaemic. However, the
clinical picture was confused by the
presence of colitis due to Salmonella
Typhimurium in these worst affected pigs.
During the farm visit colitis was not
identified as a problem on the farm and
appeared to have occurred, as a terminal
event, in severely compromised
recumbent pigs. Results of gross and
clinical pathology, and feed analyses
indicated an imbalance/inadequacy of
dietary calcium and phosphorus as a
likely cause of the problem. A change in
ration, with increased mineral content,
was instigated within days of the visit and
preliminary reports indicated that there
were almost immediate improvements.
Individual attention was given to the worst
affected pigs to enable them to reach
feed and water without competition – a
priority from the welfare viewpoint.
Although there were two other units
where pathological fractures were
reported in similar age pigs, there is
currently little information available.
MYCOPLASMAS:
Seventeen isolates, all from lungs, were
identified as Mycoplasma hyorhinis. The
precise role of M.hyorhinis in disease is
worthy of further investigation.
Historically it has always been considered
a commensal, but internationally is
increasingly associated with more
disease, including otitis media,
eustachitis, bacterial meningitis, and even
abortion.
WELFARE
A ruptured oesophagus was identified
during an investigation of disease in
neonatal pigs. This was a sporadic
incident thought to result from a dosing
gun injury. Nevertheless, the private
veterinary surgeon was asked to
investigate and advise the farmer further.
Remnants from poorly clipped teeth
resulted in osteomyelitis from
Streptococcus dysgalactiae equisimilis
infections – advice was given to improve
teeth clipping procedures.
Two 5-week-old pigs were submitted for
investigation into poor growth and deaths
affecting 12 from a group of 60. Both
pigs had navel infections with fibrous
calluses and skin abscessation of the
distal limbs. Arcanobacterium pyogenes
was isolated form the navels. Although
the herd had previous PMWS cases there
was no evidence of PCV-2 associated
disease in these two pigs to account for
increased susceptibility to infection.
Source: Veterinary Laboratories Agency - May 2004