PMWS and PDNS latest news November 2003

UK - Veterinary Laboratories Agency (VLA) Quarterly Surveillance report on PMWS and PDNS from July to September 2003
calendar icon 1 November 2003
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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.

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Source: Veterinary Laboratories Agency - November 2003
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