The annual diagnostic rate for PMWS demonstrated the continuing decline since 2002 in submissions of this disease – see histogram, which shows VIDA incidents of PMWS and related diseases (but excluding PDNS) as a percentage of diagnosable submissions 1999- 2005:

The annual diagnostic rate for PDNS demonstrated a return to that seen in 2000, although the increase on intervening years only reached statistical significance when comparing with 2003 – see histogram, which shows VIDA incidents of PDNS as a percentage of diagnosable submissions 1999-2005:

The explanation for these observations on the different trends in diagnostic rates for PMWS and PDNS are not known. However, the two conditions are associated with each other on affected units, and the occasional pig is diagnosed with both conditions. It is recognised that there is a decreasing demand for confirmatory diagnostic necropsies of clinically diagnosed PMWS, although the diagnosis of several other, often treatable or preventable, causes of wasting in pigs suggests that this may be an unsound strategy. An added complication is that PMWS now appears to increasingly affect older pigs particularly up to 20 weeks of age. PDNS on the other hand often presents as ‘found dead’ without obvious skin lesions; thus perhaps influencing a decision to have such ‘unexplained’ losses investigated further.

HIGH MORTALITY IN GROWERS AND FINISHERS

Preliminary findings from investigating 27 incidents of high mortality in growers and finishers, between 10 and 20-weeks of age, indicated that 60 of 100 pigs examined had underlying microscopic lymphoreticular lesions – distinct but variable lymphocyte depletion and granulomatous infiltration – in which PCV2 was also demonstrated.

However, only 27 of these 60 pigs were in poor condition sufficient to justify a diagnosis of PMWS. Twelve pigs in this study were diagnosed with PDNS. All incidents investigated had at least one pig with pneumonia and or pleurisy; lesions that were observed in 88% of the pigs necropsied. PCV2, PRRSV, and Pasteurella multocida were each detected in around one third of pneumonic lungs. Preliminary conclusions are that high mortality in growers and finishers, regardless of a variety of diagnoses and presenting clinical signs, commonly involves underlying PCV2-associated disease. Not unexpectedly, multiple pathogens contributed to disease on units and in individual pigs.

Further Information