NADIS

Welcome to NADIS. Are you a...

Vet SQP Farmer/Animal Keeper Industry Professional Researcher Not In Animal Health Industry

You will only be asked this once.

Season Update on Pig Diseases

Boehringer Ingelheim logo

Pig Diseases - Selected Highlights from the GB Emerging Threats Quarterly Report. Vol 21: Q2, April to June 2017

The following material is taken from the GB Emerging Threats Quarterly Report. Vol 21: Q2, April to June 2017. The full report can be found on the Animal & Plant Health Agency (APHA) web pages: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/646137/pub-survrep-p0217.pdf

For information about pig disease diagnosis and to access diagnostic support, please see:

http://ahvla.defra.gov.uk/vet-gateway/surveillance/diagnostic/index.htm

Analysis of Diagnosis Not Reached (DNR) by syndrome and presenting sign

  • Four neonatal pig (0-7 days old) submissions with a presenting sign of diarrhoea were undiagnosed to Q2 2017 which was a significant increase compared to the same period in prior years. Although this represents a small number of cases, they and undiagnosed preweaned pig diarrhoea cases were reviewed. Histopathology indicated a likely bacterial cause in five of eight cases however, testing for the common enteropathogens for this age of pig which was possible in seven of the eight cases, did not identify the cause. Further submissions were recommended and additional diagnostic bacterial testing of such cases in future is being considered.
  • A significant increase in DNR in Q2 2017 compared to prior years for musculoskeletal syndrome submissions involving five undiagnosed cases was reviewed. Three were non-carcase submissions which would have limited diagnostic investigation. Two carcase submissions were undiagnosed; in one, prior antibiotic treatment was cited as a reason for lack of diagnosis while the other remained undiagnosed despite reasonable testing. These five cases do not suggest a new and emerging disease but DNR for this syndrome will be kept under review.

Risk of African Swine Fever introduction raised to low

The risk of African Swine Fever (ASF) being introduced into the UK pig herd has been raised from very low to low (rare but does occur) in the latest outbreak assessment from APHA's International Disease Monitoring Team ASF POA Aug 3 2017. This followed reports of cases of ASF in dead wild boar in the Czech Republic, the first case in Romania in backyard pigs and a westward spread in Poland. The detection in Czech wild boar represented a significant geographic jump into a new region. The source of infection has not been confirmed, but generally when the disease appears for the first time at this distance from previously affected areas, it is more likely to be due to illegal movements or feeding on contaminated products. The first wild boar cases in the Czech Republic were mostly found near inhabited areas and introduction of infection by wild boar consuming contaminated products is the most likely scenario. Intensive surveillance and wild boar containment and control are in progress. An alert was issued to Pig Veterinary Society members and in the APHA VIC monthly newsletters to veterinary practices requesting veterinarians to raise awareness about the ASF situation in Eastern Europe amongst their pig-keeping clients and to emphasise the need to minimise the risks of introduction of ASF, and other exotic diseases, to their pigs. Key amongst actions is preventing feeding of kitchen waste to pigs. APHA recently ran a campaign recently to get this message across to pig owners and members of the public ( APHA comms illegal feeding of pigs). Reviewing biosecurity measures to address any weak areas, ensuring that staff do not attend other pigs, that staff and visitors wear clothing and boots dedicated to the farm and that no meat or meat products are brought onto the farm are all vital. APHA contributed to an on-line item in Pig World ( ASF Pig World Aug2017) to help disseminate key messages. The BVA and Pig Veterinary Society have also issued a news release emphasising these BVA-PVS ASF Aug2017.

Early detection of suspect notifiable disease and prompt reporting to APHA field services is essential and there is more information about the signs and lesions of ASF on these links: Defra ASF Guidance and ASForce-project, and information about the disease in Eastern Europe on these links: FAO ASF and EFSA ASF control.

Haemorrhagic disease outbreaks reported as suspect swine fever

Two reports of suspect swine fever were made to APHA during Q2, 2017; both were negated. In the first, the Thirsk Veterinary Investigation Centre (VIC) reported suspicion of swine fever when dead, seven-day-old piglets with haemorrhagic lesions illustrated in Figures 2 and 3 were submitted from a farm on which about half the piglets in each of three litters had died in the previous two days.

F1

Figure 1

F2

Figure 2
Kidney (arrow) and serosal haemorrhages (Figure 1) and skin haemorrhages (Figure 2) in a case of thrombocytopenic purpura.

APHA veterinarians immediately visited the herd of origin to investigate and found sows and piglets were well, with no pyrexia or other clinical signs of swine fever, and that deaths reported in weaned pigs related to long-term respiratory disease. They were able to rule out swine fever on clinical grounds. The clinical, epidemiological and pathological features made it likely that the piglets died from thrombocytopenic purpura (TP). This occurs in preweaned pigs when the sow produces antibody to fetal thrombocyte antigens which is ingested by piglets in colostrum and leads to a coagulopathy. TP has prompted suspect swine fever report cases on previous occasions as the haemorrhages found at postmortem examination can resemble those seen in swine fever. TP is not seen in gilt litters and all three affected litters were from sows; no further problems were reported from the unit. The disease tends to be sporadic in commercial herds. The case was described in the APHA monthly Veterinary Record surveillance report (APHA 2017b).

In the second case, dead piglets aged two and three weeks of age were submitted to the Carmarthen VIC after being seen to be off colour in the morning and dying rapidly. There was extensive red-purple skin discolouration (Figure 3) and unusually marked haemorrhages over the kidney cortices of one pig (Figure 4).

F3

Figure 3: Red-purple discolouration of the skin due to erysipelas septicaemia

F4

 

Figure 4: Marked kidney haemorrhages due to erysipelas septicaemia

When further history was received that there was an unwell sow with pyrexia (40.5°C), two more sick piglets and others showing malaise at the smallholder premises, the case was reported as suspect notifiable disease (swine fevers). Field APHA veterinarians visited and examined the live pigs, and sampled them to test for swine fevers as it was not possible to rule out the possibility of notifiable disease on clinical grounds. Tests for African and Classical swine fevers were negative and restrictions were lifted. Bacteriology was then progressed and Erysipelothrix rhusiopathiae was isolated from the spleens, livers and meninges confirming a diagnosis of erysipelas. No pigs on the premises had been vaccinated for erysipelas. The live sick pigs had responded well to treatment with penicillin. This case is to be included in the September APHA disease surveillance report in the Veterinary Record.

Where suspect swine fever signs and/or lesions are seen, they must be reported to APHA https://www.gov.uk/guidance/african-swine-fever for investigation as occurred in these cases which highlight the importance of prompt veterinary investigation and achieving a diagnosis in disease incidents (once negated for notifiable disease), particularly where clinical signs resemble some of those seen in porcine notifiable disease.

Swine influenza infection in sows associated with several abortions

Convincing seroconversion (<1/10 to 1/5120) between acute and convalescent sera from the same sow collected two weeks apart was demonstrated to the pandemic H1N1 2009 strain of swine influenza. The sow was one of five out of a group of 60 showing late-term abortion over the period of a week in an indoor breeding herd. Foetuses submitted from this sow were freshly dead and of similar size without any mummification and no infectious agent of abortion was identified by routine testing. The serology results suggested the abortion was likely to have occurred due to maternal factors relating to the influenza, such as pyrexia, although there was no overt respiratory disease apparent in the sows. A second aborting sow showed a significant increase in antibody titre to the same influenza strain (1/80 increased to 1/640) between acute and convalescent sera which supported the diagnosis. Swine influenza infection in breeding pigs is very variable in clinical presentation; outbreaks in England have previously been confirmed by APHA in which reproductive disease with abortions was reported, while in other breeding herds, minimal or no clinical signs were noted despite confirmed infection (Williamson and others, 2012). Swine influenza is mainly diagnosed by PCR on plain nasal swabs or tissues (pool of tonsil, trachea and cranial lung from each pig) and this virological testing is offered at no charge to the submitting veterinary practice under a Defra-funded swine influenza surveillance project at APHA. There is more information about this surveillance on this link: http://ahvla.defra.gov.uk/documents/surveillance/diseases/swine-influenza.pdf.

Staphylococcal skin infection and antimicrobial resistance

Livestock-associated meticillin-resistant Staphylococcus aureus (LA-MRSA) was identified in an APHA scanning surveillance submission to a Veterinary Investigation Centre in England following testing of a Staphylococcus aureus isolate obtained from a piglet submitted to investigate skin disease. Antimicrobial resistance testing of the isolate was carried out within APHA's "Monitoring of Antimicrobial Resistance in Bacteria from Animals and their Environment" project. This is the second LA-MRSA to be isolated from a pig in a scanning surveillance submission in England; the first was in late 2014 (Hall and others, 2015), also in a case of skin disease. Guidance for those working with livestock to reduce the risk of LA-MRSA infection is available LAMRSA guidance for livestock workers. The diagnostic investigation also detected Staphylococcus hyicus, the common cause of greasy pig disease, which was diagnosed in the pig which had the skin lesions illustrated in Figures 5 and 6. The S. hyicus showed the same antimicrobial resistance pattern and is being further characterised. There have been no LA-MRSA prevalence studies in pigs reported in UK since 2008 when the EU breeding pigs survey did not detect LA-MRSA (EFSA, 2009). The Veterinary Medicines Directorate, which is the policy lead for antimicrobial resistance, has recently submitted an update of LA-MRSA isolations from animals in the UK which will shortly be published in the Veterinary Record.

F5

Figure 5: Exudative epidermitis lesions

F6

Figure 6: Facial exudative epidermitis lesions

Swine dysentery outbreaks continue into second quarter of 2017

Six diagnoses of swine dysentery were recorded in APHA and SAC CVS submissions in the first six months of 2017 on five premises in England; three in North Yorkshire, one in East Anglia and one in Cheshire. This represents a slight upward trend compared to 2015-16 as shown in Figure 7. Where Brachyspira hyodysenteriae isolates were available from outbreaks, they were tested for tiamulin sensitivity free of charge and none were resistant. The development of resistance in Brachyspira hyodysenteriae to antimicrobials commonly used in the control of swine dysentery is a recognized risk, particularly in situations where medication is used long-term. The control of swine dysentery using alternative interventions (all-in, all-out management systems; cleaning and disinfection; and partial and total depopulation leading to eradication) is vital to prevent the development of wider antimicrobial resistance.

F7

Figure 7: Seasonality of GB swine dysentery diagnoses as a % of diagnosable submissions

Advice issued to pig producers in 2016 when a cluster of swine dysentery cases was seen in Yorkshire remains relevant NPA Swine dysentery alert 2016. There is advice on swine dysentery control and information about the Significant Diseases Charter on the AHDB Pork website http://pork.ahdb.org.uk/health-welfare/health/swine-dysentery/.