Defence of doctoral thesis on epidemiology of PCV2

Next Tuesday, 28th April 2009, Llorenç Grau Roma, PhD student of the CReSA, will defend his doctoral thesis entitled “New insights into the epidemiology of postweaning multisystemic wasting syndrome (PMWS)”, directed by Dr. Joaquim Segalés Coma and Dr. Lorenzo José Fraile Sauce.

The present thesis was developed within the European Union (EU) project entitled Control of Porcine Circovirus Diseases (PCVD): Towards Improved Food Quality and Safety, which was funded by the EU Sixth Framework Programme. This thesis is summarized next:

The definition of two PCV2 genotypes (1 and 2) was proposed. Genotype 1 was shown to be predominant within pigs coming from PMWS affected farms. Moreover, all sequences included in genotype 1 came from pigs from PMWS affected farms, while all sequences obtained from non-PMWS affected farms corresponded to genotype 2. Consequently, it was suggested that PCV2 genotype 1 might potentially be more pathogenic than PCV2 genotype 2. In addition, infection of single pigs from PMWS affected farms harbouring both genotypes at the same time was described.

Two different real-time quantitative PCR (qPCR) assays used routinely in two laboratories from two different countries, Denmark and Spain, were compared. Results showed a significant linear association between the assays, and a systematic difference indicated that the assay from the Danish laboratory yielded a higher output than the assay from the Spanish laboratory. Moreover, the Danish assay had higher sensitivity than the Spanish one.

Longitudinal case–control studies were performed in PMWS affected farms from Denmark and Spain using similar designs. Similar PCV2 infection dynamic patterns were observed in Spain and Denmark, with a delay in PMWS age-presentation in Spain compared to the one in Denmark. Thus, all Spanish PMWS outbreaks occurred at the fattening phase, whereas all Danish clinical outbreaks were observed at nurseries.

Moreover, the evolution of two acute phase proteins (APPs), pig-major acute phase protein (pig-MAP) and haptoglobin (HPT), in serum from studied pigs was also assessed. Overall, results showed that PCV2 load increased concomitantly to maternal antibody level waning, reaching the maximum viral load concurrently with the development of clinical signs. Interestingly, the acute phase response (APR) in PMWS affected pigs occurred in parallel to PCV2 viremia, suggesting that PCV2 is the main responsible for the systemic inflammatory status suffered by diseased pigs.

As a collective, PMWS affected pigs harboured higher PCV2 loads and higher Pig-MAP and HPT concentrations in sera, shed higher viral loads through both nasal secretions and faeces, and had lower level of maternal antibodies against PCV2 than non-PMWS affected pigs. Moreover, in Spain, PMWS affected pigs showed also higher APR and higher PCV2 prevalence than non-affected ones at the sampling prior to PMWS outbreak. Besides, in Denmark, PMWS affected pigs at the sampling prior to PMWS outbreak showed higher PCV2 loads than non-affected ones. Results indicated that qPCR might potentially be a reliable technique to diagnose PMWS on a population basis.

The first vaccines against the disease appeared during the carrying out of this work. Therefore, the knowledge generated can contribute to the correct application of these vaccines, as well as to comprehend their mechanism of action.

The following papers have been published, fruits of the studies on PCV2 (Pubmed):

This work was funded by the projects No. 513928 from the Sixth Framework Programme of the European Commission (www.pcvd.org), GEN2003-20658- C05-02 and Consolider Ingenio 2010–PORCIVIR.

The event will be hold next Tuesday, 28th April, 2009, in the Sala de Graus of the Veterinary School of the Universitat Autònoma de Barcelona, at 11:30 h

 



  • To contact with the author of this thesis:
Llorenç Grau Roma
PhD Student
Viral Diseases Unit (CReSA)
Email: llgrau@cresa.uab.cat
Telephone no.: +34 93 581 45 61
Fax: +34 93 581 44 90
Edifici CReSA. Campus UAB
08193 Bellaterra (Barcelona) España
  • To consult the thesis:

 

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