Strep Suis Type 2 Keeps Mortality High

12 March 2012, at 5:33am

UK - In the latest AHVLA Scanning Surveillance Report, Streptococcus suis type 2 remains a prominent cause of pig mortality and hypoglycaemia.

Reproductive Diseases

Abortion due to PRRS

Fetuses from an aborted gilt litter submitted to Thirsk tested positive for PRRSv by PCR. The history was of late abortion with pyrexia and inappetence. The 540-sow herd was reported to vaccinate against PRRSv, erysipelas and parvovirus. The vaccination programme on farm was reviewed as a result of this diagnosis and further material will be submitted if problems persist.

Alimentary Diseases

Two outbreaks of swine dysentery in scouring growers and finishers

Three pigs were submitted to Thirsk to investigate acute onset diarrhoea affecting about 150 of 600 sixteen-week-old pigs. Swine dysentery (Brachyspira hyodysenteriae) was diagnosed with concurrent Salmonella Typhimurium var Copenhagen phage type U288 infection. Minimum inhibitory concentration (MIC) testing revealed the Brachyspira isolate to be sensitive to tiamulin. PRRS virus was also detected, which was not unexpected as PRRSv infection was present on the breeding farm supplying pigs to the unit.

Two ten-week-old pigs were submitted to Truro from a group of 13 in which two others had died following acute onset bloody diarrhoea. In one pig, watery blood-stained fluid was present in the distal small intestine which had a markedly congested mucosa, with evidence of diptheresis in the caecum and proximal colon and grey watery diarrhoea. In the second pig, the contents of the colon were watery and brown. Lawsonia intracellularis infection was detected in small intestinal contents from the first pig consistent with proliferative enteropathy. Brachyspira hyodysenteriae was detected in intestinal contents from both pigs consistent with concurrent swine dysentery.

Respiratory Diseases

Swine influenza in successive batches of replacement gilts

Swine influenza was diagnosed as the cause of recurrent coughing in batches of replacement gilts on an indoor unit. Nasal swabs were submitted from eight acutely ill five-month-old gilts. These were tested free of charge in the Defra-funded swine influenza surveillance project and influenza virus was detected by PCR, identification of the strain is in progress.

Systemic & Miscellaneous Diseases

Wasting due to combined PRRS and PCV-2 associated disease

A problem of wasting in finishers from about 12 weeks of age was reported. Three pigs were submitted from a batch of 500 where about 40 were affected. The pigs were vaccinated against Mycoplasma hyopneumoniae and PCV-2. Post mortem findings included pneumonia, peritonitis, pleuritis, enteritis and generalised lymphadenopathy in all three pigs. PRRS virus (European strain) was detected and histological examination revealed changes in depleted lymph nodes confirming PCV-2 associated disease. Streptococcus suis type 2 and Salmonella Typhimurium var Copenhagen (phage type U302) were isolated. It is considered possible that the presence of PRRS virus, which is immunosuppressive, affected the immunity of the pigs and interfered with the immune response to the PCV-2 vaccines, leading to PCV-2 associated disease and secondary bacterial infection; investigations continue.

Late onset porcine circovirus 2-associated disease (PCVAD) in finishers

PCVAD was diagnosed as the cause of wasting in thirty 16-week-old pigs from a group of 240 with several pigs also found dead. Two pigs in poor body condition were submitted in both of which there was marked interlobular pulmonary oedema and cranioventral pulmonary consolidation and, in one, a massive fibrinous pleural effusion, typical of the acute pulmonary oedema presentation occasionally seen with PCVAD. Streptococcus suis type 3 was isolated from the lungs of both pigs and was considered to be secondary to the porcine circovirus 2-associated disease which was confirmed by histopathology on lungs and lymph nodes of the two pigs with characteristic intracytoplasmic inclusion bodies being detected. The pigs were not vaccinated for PCV2 and piglet vaccination of subsequent batches was initiated.

Nervous Diseases

Streptococcus suis type 2 remains a prominent cause of mortality

Two dead pigs were submitted from a large outdoor nursery unit to investigate mortality which had risen from 1% to 2.5% over the previous two weeks. Affected pigs were seven to eight-weeks-old and were presenting as sudden deaths occurring randomly across outdoor pens. Eighteen deaths had occurred in the three days prior to submission. There was fibrin stranding in the peritoneal cavity and a purulent arthritis in one pig, meningeal blood vessels were prominent and the surface of cerebral hemispheres had a slightly cloudy appearance. These changes were suggestive of a septicaemia and 5 of 6 meningeal smears tested positive for Streptococcus suis type 2 from both pigs confirming a diagnosis of streptococcal meningitis.

Further Reading

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