Open Access Research article

Impact of genetic variation and geographic distribution of porcine reproductive and respiratory syndrome virus on infectivity and pig growth

Bouabid Badaoui1, Roberto Grande1, Stefano Calza2, Maria Cecere1, Mario Luini3, Alessandra Stella1 and Sara Botti1*

Author Affiliations

1 Parco Tecnologico Padano - CERSA, Via Einstein, Lodi, 26900, Italy

2 Università degli Studi di Brescia, piazza del Mercato, Brescia, 25121, Italy

3 Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna, Lodi, 26900, Italy

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BMC Veterinary Research 2013, 9:58  doi:10.1186/1746-6148-9-58

Published: 27 March 2013

Abstract

Background

The porcine reproductive and respiratory syndrome (PRRS) is a devastating disease for the pig industry. In this study, we analysed the genetic variability of PRRS virus (PRRSV) as well as the relationship between the genetic variability, the geographical and temporal distribution of the PRRSV strains. Moreover, we investigated the association between the glycosylation patterns in PRRSV sequences and pigs growth.

Results

The data highlight that PRRSV strains evolve rapidly on individual farms, and temporal evolution of PRRSV is an important factor of genetic variability. Analysis of glycosylation sites in the glycoprotein 5 (GP5) ectodomain revealed that PRRSV isolates had seven combinations of putative N-linked glycosylation sites of which the N37/46/53 sites was found in 79% of the sequences. No significant relationship was found between the genetic variation of the PRRSV strains and the geographic distance. A significant relationship was found between the genetic variation and time of sampling when farm was considered as a factor in the analysis. Furthermore, the commercial semen from artificial insemination centres was not a source of PRRS transmission.

The PRRSV having the glycosylation site at position N46 (N46+) were observed to have higher burden on pigs and accordingly the corresponding infected pigs had lower average daily gain (ADG) compared with those infected with PRRSV lacking the glycosylation at N46 (N46-) position site. This study showed that the number of piglets by litter infected by PRRSV was lower for the Landrace breed than for the other studied breeds (Large White, Duroc and Pietrain).

Conclusions

The PRRSV genetic variability which is determined by a local and temporal evolution at the farm level could be considered in a perspective of prevention. Moreover, the association between the PRRSV glycosylation patterns and its virulence could be of interest for vaccine development. The differences of resistance to PRRSV infections among pig breeds might open new horizons for the genetic selection of robustness against PRRSV infection.

Keywords:
PRRSV; ORF5; ORF7 sequences; Glycosylation