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

Abstract

BackgroundThe 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.ResultsThe 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).ConclusionsThe 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.

Phylodynamic analysis of porcine reproductive and respiratory syndrome virus (PRRSV) in Italy: Action of selective pressures and interactions between different clades

“…Contrary from what was previously reported in literature (Wissink et al, 2004), the presence of several strains collected at different points in time without N-46 confirms that this glycosylation is not essential for viral infectivity, a phenomenon recently reported for Type 2 (Wei et al, 2012). However, the high prevalence of this glycosylation site suggests that it could influence susceptibility to pig immune response (Ansari et al, 2006;Vu et al, 2011) and may consequently have repercussions on pigs' performance (Badaoui et al, 2013). Accordingly, the extremely limited number of strains lacking glycosylation in positions 35-37 and 53 could be due to an earlier and higher induction of neutralizing antibodies by strains devoid of these glycosylation sites, as reported by Faaberg et al (2006).…”

Investigation of the Occurrence of Porcine Reproductive and Respiratory Virus in Swine Herds Participating in an Area Regional Control and Elimination Project in Ontario, Canada

“…The lack of a strong spatial component that would be indicative of local spread is in agreement with previous studies (Goldberg et al., ; Badaoui et al., ; Rosendal et al., ) and in contrast to several findings from other source populations (Mondaca‐Fernandez et al., ; Otake et al., ; Lambert et al., ). It is interesting to note that most statistically significant associations were detected for PRRSV 1‐8‐4.…”

Genetic Diversity of PRRS Virus Collected from Air Samples in Four Different Regions of Concentrated Swine Production during a High Incidence Season

“…While some previous studies have also found that airborne transmission of PRRSV as an important route of viral spread [ 7 , 9 ] others have suggested that the relevant route of spread is animal movement, based on molecular epidemiology [ 30 , 31 , 32 ]. In theory, if the only route of PRRS spread were airborne, an association between the space and genetic variation would be expected, but because the virus is spread by animal movement, as well as air, evidence of this association is difficult to assess.…”