ShapeShapeauthorShapechevroncrossShapeShapeShapeGrouphamburgerhomeGroupmagnifyShapeShapeShaperssShape

UK Pig Disease Quarterly Surveillance Report - November 2003

by 5m Editor
6 December 2003, at 12:00am

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.

Quarterly Surveillance Report Pigs: Vol. 7 No. 3
Jul - Sep 2003 - Published Nov 2003

Contents

OVERVIEW (here)

NOTIFIABLE DISEASES

ZOONOTIC DISEASES

ENDEMIC DISEASES

Highlights: Third Quarter 2003

  • Clean pig slaughterings down 10% on previous year
  • Defra Animal Health and Welfare Strategy consultation in progress
  • Zoonoses Action Plan (ZAP) moves to on-farm initiatives
  • PMWS continues to occur concurrently with many other syndromes/infections
  • Reproductive problems occurring again in some herds as last year, but overall not as commonly reported as in previous September
  • No new strains of swine influenza virus detected Data, particularly from VIDA, is provisional and liable to change.

Overview

The MLC Economics, Pig Market Outlook: 03/4 October 2003, provides an overview of the pig sector. The UK breeding herd is still expected to stabilise at around half a million sows in 2004. Clean pig slaughterings for the first nine months of 2003 were down 10 percent on the same period for 2002. Reasons include further decline in the pig herd, deterioration in average sow productivity, continuing sporadic losses due to PMWS, last year’s increased infertility problems resulting in fewer pigs slaughtered in the second quarter this year, and some disruptions due to last year’s depopulation/repopulation of some herds.

Pig prices averaged 10 percent less in the third quarter compared with the previous quarter. The GB Deadweight Average Pig Price (DAPP) was 99.76/kg dw at the end of September compared with 110.79 p/kg at the end of June. A sharp fall in July and August prices was attributed partly to the extended period of very hot weather reducing demand for fresh pork, and partly to lower mainland European pig prices encouraging imports.

During September the UK pig price fell below the average EU price. For more information on the British pig industry go to http://www.bpex.org.uk and http://www.mlceconomics.org.uk Autofom, a new generation of pig grading equipment, is now authorised by the EU for use in Great Britain. It has the potential to improve the competitive position of British pig producers and processors.

Defra introduces new Pig Identification legislation in England and Wales in November. It requires all pigs moving from a holding to an abattoir to have a Defra herdmark, using an eartag, a tattoo or a slapmark.

The British Pig Executive, the National Pig Association, and the Pig Veterinary Society responded to the Defra Animal Health and Welfare Strategy consultation by producing a draft pig health and welfare strategy. The action points proposed are for further discussion. They are:

  1. establish a national framework,
  2. determine present health and disease status,
  3. enhance disease surveillance,
  4. undertake studies on disease control and eradication,
  5. develop national biosecurity controls,
  6. develop protocols for new disease prevention and eradication programmes,
  7. quantify risks and the consequences of emerging pig issues,
  8. enhance training in disease identification,
  9. increase the programme of targeted pig disease research.

Notifiable Disease:

AFRICAN SWINE FEVER (ASF):
No outbreaks of ASF were reported in Europe, though still considered as present in Sardinia. The disease was reported in African countries in the quarter, namely Senegal, Congo, Burkina Faso, Nigeria and Tanzania.

CLASSICAL SWINE FEVER (CSF):
CSF was reported in Luxembourg during August on a large breeding/finishing unit of 1,095 pigs. The first epidemiological investigations indicated a possible contact with wild boar. CSF was diagnosed in Sardinia during September. The disease is very difficult to control in Sardinia, due to the large numbers of wild boar and feral pigs, combined with the terrain of the island. The Classical Swine Fever Order (England) Order 2003 was made on 9 September 2003 and came into force on 1 October 2003. It enacts the provisions of EU Council Directive 2001/89 for the control of CSF. Similar legislation is being made for Scotland, Wales, and Northern Ireland. For more information: http://www.defra.gov.uk/animalh/diseases/default.htm

Only one case of CSF was reported from Brazil in the last three months, reflecting the apparent success of the eradication scheme that has been running in the country for some years.

FOOT AND MOUTH DISEASE (FMD):
There were no reports of outbreaks of FMD within Europe in the last quarter. In July FMD serotype “O” was confirmed in Bolivia. Over 1,000 cattle and 2500 pigs were involved. Subsequently seven further outbreaks were reported. Another serotype “O” outbreak was reported in September in Argentina in a herd of 39 pigs. African FMD outbreaks occurred in Libya and Zimbabwe.

EUROPEAN UNION FARM ANIMAL DISEASE CONTROL:
The European Commission announced a record budget of 147 million euros (£103 million) for farm animal disease control programs in 2004. The budget will include spending on programmes in the ten new countries (Accession Countries) joining the European Union (EU) in 2004. Eradicating the chronic problems of African and classical swine fever in Sardinia receives a budget of 250,000 euros. Programmes to monitor and eradicate Aujeszky's disease will be supported in Belgium, Spain, Hungary, Ireland, Lithuania, Malta, Portugal and the Slovak Republic. A sum of 400,000 euros is allocated to improving control and eradication of the occasional

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 incidents: The number of salmonella incidents recorded for the first nine months of 2003 is 154 compared with 158 and 152 for the same period in 2002 and 2001 respectively. Salmonella serovar Derby incidents (26) are higher than those recorded in the previous two years (12 in 2002 and 20 in 2001) whereas total Salmonella Typhimurium incidents are slightly down on last year’s analogous figure. See graph at end of report.

The breakdown of Typhimurium by determinative type (DT) shows a large peak for U288. However, this is a newly designated DT formerly recorded as U308a.

Typhimurium DT99 was an unusual isolate from outdoor pigs this quarter. This type is usually associated with birds. The farm reported that pigeons were present in the paddocks. No clinical disease was reported on the unit and the salmonella was identified during monitoring.

Zoonoses Action Plan (ZAP): The Zoonosis Action Plan was launched in December 2000. In June 2002 the British Pig Executive introduced their ZAP salmonella programme for British Quality Assured Pork pigs and Specially Selected Scotch Processors. This was extended in January 2003 to include Northern Ireland. Until July 2003 the testing protocol was one sample per batch of pigs or one sample per 50 pigs when batches were greater than 50 pigs. The mixed-salmonella meatjuice ELISA is used. Since July the testing procedure was altered to three pigs tested per movement order received at the abattoir.

In July 2003, analysis of the results for farms which had had at least 15 samples tested, showed that two farms were allocated to ZAP 3 level (greater than 85% of samples tested positive) and 18 farms were allocated to ZAP 2 level (65% to 84% of samples positive).

ZAP 2 and ZAP 3 results require an action plan to be drawn up with the farm veterinary surgeon at the next assurance visit. Farms in the ZAP 3 category must undergo microbiological testing for salmonella and have an on-farm advisory visit. The private veterinary surgeon may do the advisory visit and the VLA will carry out laboratory work free of charge provided that prior notice of the visit is given and the standard protocol is followed. Alternatively the VLA have agreed to carry out advisory visits to the protocol.

5th International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork:
A presentation was given on salmonella surveillance trends in porcine salmonella in GB (1996 to 2002). This highlighted that there had been an overall decrease in salmonella incidents in pigs. However, there was an increased frequency of Salmonella Typhimurium incidents. The isolates remained sensitive to the majority of antimicrobials on the screening panel, although increased resistance trends were identified to tetracycline and sulphamethoxazole/trimethoprim. The Health Protection Agency explored possible links between Salmonella Typhimurium from pigs with human infection in England and Wales. The most common DTs potentially linked included 104, 104b, 193 and provisional type U302. In 2002 the Laboratory of Enteric Pathogens (LEP) reported 1221 human cases infected with these types. Most of these cases were however associated to non-pig sources.

Salmonella Typhimurium DT208 resistant to tetracyclines (R type T) or resistant to sulphonamides, tetracyclines and trimethoprim (R type Su T Tm), DT U310 (R type T) and DT193a resistant to ampicillin, sulphonamides, tetracyclines and trimethoprim (R type A Su T Tm) appear predominantly pig related. These strains were reported in 160 human infections in 2002.

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:
Streptococcus suis isolates: Twenty-six Streptococcus suis isolates were serotyped this quarter. Some of the more unusual serotypes (17, 24 and 30) were isolated from the upper respiratory tract or tonsils and not specifically related to lesions:


Streptococcus suis incidents: There were 12 incidents of Strep.suis infection, six of which were serotype 2. Two were serotype 14, and single diagnoses of serotype 3, 4, 8 and 12 were recorded.

Only two of the serotype 2 incidents had typical cases of meningitis affecting 9 and 14-week-old pigs on different units. In the latter, 4 of 60 pigs had died over five days following clinical signs of hindleg lameness and recumbency. Postmortem examination of a typical case revealed a fibrinous peritonitis and congested meninges. Respiratory disease and terminal meningitis was diagnosed on an organic outdoor unit where 3 of 35 12- week-old pigs died in one week. From one carcase serotype 2 was isolated from the brain, and Pasteurella multocida and avian-like H1N1 swine influenza virus from the lungs. In another incident on an outdoor unit it occurred as a secondary infection in pneumonia in an 8-week-old pig. Half the pigs were affected and two percent died. Mycoplasma hyopneumoniae, Pasteurella multocida and Strep.suis serotype 2 were detected in the lungs.

In the remaining two incidents, serotype 2 was also a secondary infection. The first was in finisher pigs over 45kg in weight, where at least 10% had respiratory signs and were unthrifty. Serology confirmed active PRRSV involvement, and histopathology the presence of PCV-2. A variety of secondary bacteria were also isolated including Strep.suis serotype 2, Salmonella Typhimurium and Haemophilus parasuis. The other outbreak was typical of Glasser’s disease in 2-month-old pigs causing high mortality. H.parasuis was readily isolated from systemic sites as well as serotype 2 from the lung and liver of a typical case.

Serotypes 3 and 4 were isolated from cases of pneumonia in grower/finishing pigs on different units. Serotype 8 was also associated with pneumonia and deaths in 4-month-old housed finisher pigs.

Serotype 12 was isolated from a sow with metritis. Neonatal piglets on the same unit were dying showing central nervous signs and had gross lesions of polyarthritis and generalised peritonitis.

Histopathological examination confirmed meningitis suggestive of Strep.suis infection. Bacteria were not isolated from the brain, probably due to prior antimicrobial treatment. Two outbreaks of serotype 14 septicaemia, meningitis and arthritis were diagnosed in dying seven-week-old pigs. In one of these, about 80 of 2600 pigs were affected with lameness and meningitis with a case mortality of <1%.

There was gross evidence of pericarditis and arthritis. No histopathological evidence of PMWS was present. The pig from one outbreak had a severely bitten tail, a possible portal of entry for the infection.

Other streptococci: Streptococcus dysgalactiae equisimilis was isolated from a case of vaginal discharge on a farm with a recent history of conception failure. S.equisimilis is known to cause vaginitis in sows and neonatal septicaemia. The same organism was also isolated from a breeding boar with septic polyarthritis and pericarditis.

ENDEMIC DISEASES – SUBMISSIONS:


Note: ‘diagnostic’ refers to initial submission in an incident

Provisional data for total pig submissions showed a similar third quarter decline to last year. This was partly attributed to seasonal factors and partly to nondiagnostic project submissions that resulted in the higher total carcase submission numbers in the first half of this year. Diagnostic (submitted primarily for a differential diagnosis) submissions, and diagnostic carcase submissions and specimens were below the average for the previous six quarters, reflecting seasonal factors such as the higher priority for farmers of the autumn arable harvest.

There were no marked changes in the ‘diagnoses not reached’ and ‘diagnoses not listed’ categories for non-reproductive diseases. No increase in the number of undiagnosed non-fetopathy (incidents without abortions) reproductive disease submissions was recorded in the quarter. Despite the provisional nature of the data for September, there is no evidence yet that the increase recorded in this category for September last year has recurred this year.

POSTWEANING MULTISYSTEMIC WASTING SYNDROME (PMWS)/
PORCINE DERMATITIS AND NEPHROPATHY SYNDROME (PDNS):

Incidents: Diagnosis of PMWS as a percentage of diagnostic carcase submissions declined throughout the year with first quarter at 18.2%, second quarter at 13.7% and this quarter 6.4%. This is unlikely to represent a major reduction in PMWS. It probably reflects the widespread recognition of the clinical disease on farms with little need now for confirmation of the diagnosis except in changing circumstances. There were three diagnoses of PDNS this quarter.

PMWS was commonly diagnosed as part of the respiratory disease complex (see Respiratory Disease section). Housed 18-week-old finishers on one unit were diagnosed with pneumonia due to Pasteurella multocida and PDNS with a reported 7% mortality. A breeding and finishing unit was visited to investigate predisposing factors for suspected lateonset PMWS in finisher pigs. On this unit farrowing was changed to a batch system in 2001 resulting in a reduction in mortality due to PMWS in 6 to 10-weekold pigs, from 10-15% to 4-5%. There had been a gradual increase in mortality and wasting over the preceding 18- months to 10-15% in predominantly 14- week-old pigs. These pigs presented with wasting, dyspnoea and scour.

Pathogens identified at postmortem examination, and following serology, included Streptococcus suis serotype 2, Haemophilus parasuis, PRRSV and PCV- 2. The change to late onset of PMWS on this unit may have resulted from a gradual build-up of pathogens within buildings, and from the practice of crossfostering in the first 24 hours after farrowing, since this may be a risk factor for PMWS. The Madec 20-point plan recommends that cross-fostering is limited to that which is absolutely necessary within 24 hours of farrowing.

Concurrent PCV-2 infection was associated with a range of enteric pathogens including Salmonella Typhimurium, Lawsonia intracellularis and Brachyspira pilosicoli. VLA Bury St Edmunds reported that practitioners in East Anglia are seeing an increase in diseases concurrent with PCV-2 infection. Prioritising the importance of the pathogens identified within a herd is often clinically challenging. New Zealand reported the first diagnosis of PMWS in that country.

ENTERIC DISEASE:
Colibacillosis, involving predominantly enterotoxigenic K88-positive serotypes, continued to predominate in both neonates and weaners. Mortality was usually low but occasionally reached 20 to 25% in suckers, especially when complicated by mis-mothering and poor milk supply in gilt litters. Other enteric infections were sometimes present including coccidiosis, clostridial enterotoxaemia and salmonellosis. Coccidiosis was more commonly diagnosed; probably reflecting above average environmental temperatures encouraging rapid sporulation of oocysts in contaminated farrowing houses.

Several serious rotavirus scour outbreaks were also reported in neonates, one involving 75% morbidity and up to 50% mortality in affected litters. In growers, scour and illthrift were most often associated with ongoing PCV2/PMWS outbreaks. Porcine intestinal adenomatosis / proliferative enteropathy (Lawsonia intracellularis infection) and Brachyspira pilosicoli colitis were, however, implicated as significant contributory conditions in some herds. Swine dysentery continued at its very low level with only one confirmed case in finishers.

Easily the most frequently encountered non-infectious condition in finishers was gastric ulceration, usually causing sudden death as a result of severe haemorrhage. An outbreak of fatal gastric torsion and rupture in outdoor sows was associated with intense excitement at feeding and excessive soil ingestion.

RESPIRATORY DISEASE:
There were 24 reports of respiratory disease this quarter, and in 7 of these there was concurrent PCV-2 infection. The most frequently diagnosed cause of respiratory disease this quarter was P.multocida (18), although this was at a lower incidence than the first and second quarters (35 and 21 respectively). VLA Bury St Edmunds highlighted the importance of submitting fresh plucks or recently euthanased pigs to allow more useful investigation. The submission of samples from treated pigs and chronically affected pigs also hampers a full investigation with a tendency to increase the diagnosis of secondary bacterial infections. Diagnosis of pneumonia due to Actinobacillus pleuropneumoniae reached 14 this quarter, which is greater than the number of incidents in the third quarter of 2002 (7), 2001 (6) and 2000 (9). A previous peak occurred in 1999 (23 incidents), however as a percentage of total diagnostic submissions the figure for the third quarter of 2003 at 5.2% is greater than that for 1999 (4.4%).

A.pleuropneumoniae, in association with Bordetella bronchiseptica, accounted for 10%-15% morbidity and a mortality of 4%-5% in 37 to 50-day-old pigs. A finishing unit with 1700 pigs experienced coughing in about 5% of pigs; Mycoplasma hyopneumoniae and P.multocida were identified and the death of seven pigs was associated with concurrent A.pleuropneumoniae infection. On two units PRRSV and PCV-2 infection were implicated as causing respiratory disease with morbidity of 10% and 12% in 45 kg and 10 to 11-week-old pigs respectively. A mortality of 0.5% and morbidity of 50% in 6-week-old pigs was investigated, with Arcanobacterium pyogenes and P.multocida isolated from necrotic lung tissue. The severity of disease was thought to be due to the presence of cytomegalovirus (inclusion body rhinitis) which was identified by histopathological examination of nasal epithelium.

Swine Influenza
Received Positive(%)
Submissions 36 2*(5.6)
Samples 85 4(4.7)
* Avian-like H1N1 x2 (both isolates grew in eggs and tissue culture).

REPRODUCTIVE DISEASE:
There was an increase in the number of submissions for investigation of abortion (Table 1), and there was an improvement in the diagnostic rate based on provisional data (Table 2). However, the non-diagnostic rate for abortions is still a cause for concern. There was no apparent rise in submissions for nonabortion reproductive problems, despite the fact that this quarter includes the traditional period for seasonal infertility to begin. Further examination of figures next quarter will be of interest, as this will clarify the level of infertility investigation in the autumn period.

Table 1: Number of submissions to investigate abortion
and non-abortion reproductive disease:
Quarter No. of submissions
Abortion Non-abortion
1st 25 52
2nd 19* 40*
3rd 29** 39**
* data revised since previous report
** provisional data

Table 2: Diagnosis-not-reached for abortion
and non-abortion reproductive disease:
Quarter No. of submissions
Abortion Non-abortion
1st 9 (36%) 36 (69%)
2nd 17 (89%)* 17 (43%)*
3rd 17 (59%)** 14 (36%)**
* data revised since previous report
** provisional data

Causes of abortion and infertility identified or suspected included Leptospira bratislava, Erysipelothrix rhusiopathiae, PRRSV, swine influenza virus and porcine parvovirus. In all cases, these infectious agents were implicated on the basis of serology. Some reports of seasonal (summer/autumn) infertility noted the association with high ambient temperatures (>30 º C) in August.

Reproductive failure on one organic herd - characterised by low litter numbers, cystic ovaries, poor follicle development and sows not-in-pig - is under investigation for potential oestrogen exposure. A visit to a traditional pig farm to investigate excessive stillbirths identified a number of potential contributory causes. These included breeding from older sows, elevated farrowing house temperatures, and parvovirus infection. Vaccination against parvovirus was recommended. On another visit to a 280-sow unit, reproductive loss was associated with poor management including an inadequate service routine. On a separate unit the cause of dehydration and death of all piglets, up to one week of age, from four gilt farrowings was not established. Poor mothering was considered a predisposing factor. During a farm visit to investigate causes of stillbirth it was noted that some of the pigs had lesions indicative of sunburn. Advice was given to provide wallows as well as shading over the pens to help prevent further cases.

PROJECT (OD0214): Isolation and characterisation of leptospires in pigs: This Defra-funded project started in July and aims to identify and characterise circulating Leptospira serovars in UK pigs. The findings of this study should help to provide material for evaluation of new serological and PCR-based diagnostic tests, which will subsequently allow epidemiological studies to investigate the significance of leptospire infections in porcine reproductive disease. Practitioners were asked to submit material, including serum, aborted fetuses and cull-sow kidneys, and to complete a short questionnaire from pig herds with infertility problems. By the end of the quarter, almost 200 sera had been submitted for this project as well as fetuses, and kidneys from seven cull sows. An update on this and the pig infertility case-series study (Project ED1018) will be given in the next Quarterly Report.

OTHER DISEASES:
Iron deficiency anaemia was diagnosed in piglets from an organic unit. This condition has previously been reported as a problem on organic units, where injection of piglets with iron is prohibited. The problem arises when piglets do not have access to soil. See also: Pig Quarterly Report 2002, volume 6, no.1.

MYCOPLASMAS:
Mycoplasma hyopneumoniae was identified from three lung samples. One isolate came from a farm that housed 2400 pigs of which only six had respiratory disease, whilst the other two isolates came from 6-month-old pigs on a farm that housed 2000 pigs of which about 500 had respiratory disease. Two other isolates were identified as M. hyorhinis, one from a hip joint and the other from a lung sample. Once again, M.hyorhinis was reported as implicated in causing disease. Previously it has been associated with otitis media and eustachitis, and as causing bacterial meningitis. In the latest case [Shin, J. H. and others (2003) Identification and characterisation of cytopathogenic Mycoplasma hyorhinis from swine farms with a history of abortion. J. Vet. Med. Sci. 65 (4) 501-509.] a variant of M.hyorhinis was associated with pigs with a history of recurrent abortion In vitro the isolate caused a cytopathogenic effect with ciliostasis and loss of cilia.

MUSCULOSKELETAL DISEASE:
A boar, which was euthanased due to lameness, had a septic polyarthritis and pericarditis from which Streptococcus dysgalactiae equisimilis was isolated. It was suspected that an ulcerative heal lesion was the portal of entry of this organism.

A 10-month-old boar was euthanased due to a forelimb lameness that failed to respond to treatment. There was severe degenerative joint disease of both elbows and a large abscess with cellulitis extending from one elbow to carpus from which Pasteurella multocida was isolated. A six-month-old gilt was submitted to investigate lameness occurring on a 3000-pig unit. A septic arthritis was present in one elbow and a larger abscess was present in a hindlimb extending from stifle joint to hock.

P.multocida was again isolated from these joints. A previous investigation on this farm had identified lameness associated with degenerative joint disease.

Salmonella incidents in pigs*: January - September

*Data are provisional and subject to change

To read the full 9 page PDF report please click here

Source: Veterinary Laboratories Agency - November 2003