Abstract
BackgroundDespite that PMWS commonly affects pigs aged eight to sixteen weeks; most studies of PMWS have been conducted during the period before transfer to finishing herds. This study focused on PCV2 load and antibody dynamics in finishing herds with different PMWS status.MethodsSequentially collected blood samples from 40 pigs in each of two Swedish (A and B) and one Norwegian (C) finishing herds were analysed for serum PCV2-load and -antibodies and saliva cortisol. The two Swedish herds differed in PMWS status, despite receiving animals from the same sow pool (multi-site production). However, the PMWS-deemed herd (A) had previously also received pigs from the spot market. ResultsThe initial serum PCV2 load was similar in the two Swedish herds. In herd A, it peaked after two weeks in the finishing herd and a high number of the pigs had serum PCV2 levels above 107 per ml. The antibody titres increased continually with exception for the pigs that developed PMWS, that had initially low and then declining antibody levels. Pigs in the healthy herd B also expressed high titres of antibodies to PCV2 on arrival but remained at that level throughout the study whereas the viral load steadily decreased. No PCV2 antibodies and only low amounts of PCV2 DNA were detected in serum collected during the first five weeks in the PMWS-free herd C. Thereafter a peak in serum PCV2 load accompanied by an antibody response was recorded. PCV2 from the two Swedish herds grouped into genotype PCV2b whereas the Norwegian isolate grouped into PCV2a. Cortisol levels were lower in herd C than in herds A and B.ConclusionsThe most obvious difference between the Swedish finishing herds and the Norwegian herd was the time of infection with PCV2 in relation to the time of allocation, as well as the genotype of PCV2. Clinical PMWS was preceded by low levels of serum antibodies and a high load of PCV2 but did not develop in all such animals. It is notable that herd A became affected by PMWS after errors in management routine, emphasising the importance of proper hygiene and general disease-preventing measures.
Highlights
Despite that postweaning multisystemic wasting syndrome (PMWS) commonly affects pigs aged eight to sixteen weeks; most studies of PMWS have been conducted during the period before transfer to finishing herds
The spread of PMWS was interrupted in Norway but prevailed in Sweden, and in 2007, when the present study was conducted, porcine circovirus type 2 (PCV2) was present in pigs from both countries but PMWS was only diagnosed in Swedish herds
General health status and description of herds Both Sweden and Norway are free from diseases listed by the Office International des Epizooties (OIE), including Aujeszky’s disease (AD) and porcine reproductive and respiratory syndrome (PRRS), as well as from porcine endemic diarrhoea (PED) and transmissible gastroenteritis (TGE)
Summary
Despite that PMWS commonly affects pigs aged eight to sixteen weeks; most studies of PMWS have been conducted during the period before transfer to finishing herds. PMWS appeared comparatively late at the Scandinavian Peninsula and was not diagnosed in Sweden or Norway until 2003 when two Norwegian herds were affected by PMWS [5]. These herds were stamped out during the spring/summer of 2004, and until February 2008 no new case of PMWS was diagnosed in Norway as demonstrated by screening programs performing necropsies on runt pigs [6]. The spread of PMWS was interrupted in Norway but prevailed in Sweden, and in 2007, when the present study was conducted, PCV2 was present in pigs from both countries but PMWS was only diagnosed in Swedish herds
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