Genotype and evolution of the PRRSV present in Mexico (2005-2013)

Introduction

Porcine Reproductive and Respiratory Syndrome (PRRS) was first diagnosed in Mexico in the 90 ́s and readily spread among the nation ́s pig population. Due to its repercussions in the productive chain, it’s considered as the most important source of economic losses for the industry (1).

Materials and Methods

Based on the genetic analysis of 447 sequences (ORF5 gene) from clinical cases collected in several states of the country during 2005–2013, a dendogram was built (Figure 1) to verify viral evolution and the genetic patterns of the infection in the country (Vector NTI advance v11.5.1; Geneious Basic V 5.0).

Results

So far, 12 genetic clusters were determined based on our data analysis. The 1992 North American isolate type 2 (2) designated as VR2332 (GenBank-U87392) initially related with the first viruses isolated in Puebla, Jalisco and Sonora, evolved in 12 genetic clusters with a notorious geographic correlation.

Figure 1. Dendogram of the evolution of PRRS virus in Mexico.

Conclusions and Discussion

Until now, we have not detected PRRS virus type 1 in Mexico in accordance with other authors (3). Mexican PRRS viruses have evolved separately from VR2332 since 2005 (Table 1). The evolution to 12 genetic clusters is also noticeable (Figure 2). Related isolates to VR2332 were a relevant factor in the genetic of PRRS Mexican viruses at the onset of outbreaks, but viral recombination and natural mutations excluded it from their genetic evolutive patterns. The live vaccine strain derived from isolate VR2332 was introduced before 2005 in Mexico, but now it has an important distant genetic homology (>10%) against 2007-2013 isolates

(Table 1). According to our analysis, isolates from Jalisco are the origin of actual Mexican PRRS virus strains with 12 genetic clusters, and should be considered in all control programs in order to choose among the available commercial vaccines (MLV), a strategy based on the use of autogenous vaccines or a combination of both. 


Figure 2. Evolution of PRRS virus in Mexico