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Bulletin No. 16 - Fall 2003
Fourth International Symposium on Emerging and Re-emerging Pig diseasesPMWS-PCV2-PCVD-PDNS
SEGALES J, CALSAMIGLIA M, DOMINGO M
How we diagnose postweaning multisystemic wasting syndrome.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 149-151
To be diagnosed as suffering from PMWS, a pig or a group of pigs must abide by three criteria, namely, typical clinical signs, typical histopathological lesions and detection of PCV2 in lymphoid tissues. One should always keep in mind that: not all pigs with wasting suffer from PMWS; although PMWS implies PCV2, the presence of PCV2 does not mean PMWS and the viral load is one of the determining factors in the expression of the disease; the detection of low amounts of PCV2 associated with only slight lesions could indicate subclinical PMWS but also an initial phase of the disease or an ongoing convalescence; PMWS can be present either in herds with good or bad performance; other diseases may be concomitantly present in a PMWS affected herd. So far, histopathological findings added to virus detection in tissues by immunohistochemistry or in situ hybridization have been considered the golden standard to establish a PMWS diagnosis. However, due to the likely correlation between amounts of PCV2 and severity of clinical signs, a quantitative PCR represents a useful (but still expensive) technique in the field of PMWS diagnosis. With regards to the epidemiological aspects of PMWS and in particular to the concept of enzootic disease (usual occurrence or constant presence of a disease), the author proposes the following criteria for a herd case definition: occurrence of clinical process characterized mainly by wasting, in excess of the expected level; and individual diagnosis in a pig or a group of pigs thanks to the three criteria mentioned before.
