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PORCINE reproductive and respiratory syndrome (PRRS) is characterised by reproductive failure in breeding females and respiratory distress in pigs of all ages, particularly in young pigs (Zimmerman and others 2012). The causative agent, porcine reproductive and respiratory syndrome virus (PRRSV), is endemic to nearly all pig-rearing regions. PRRSV is divided into type 1 (formerly European) and type 2 (formerly North American) genotypes, with approximately 50 to 70 per cent nucleotide identity between the two genotypes.
The distribution of type 1 and type 2 PRRSV is not strictly restricted by continents anymore; type 1 and type 2 PRRSVs are circulating globally. In addition, coinfection with both type 1 and type 2 PRRSVs is prevalent on some farms (Choi and others 2015). Several type 1- or type 2-based commercial vaccines have been developed and used to combat PRRS. However, no combined type 1 and type 2 vaccine is commercially available. Considering this, what vaccination strategies should be implemented to control coinfection with two genotypes: vaccination with a type 1 vaccine alone, vaccination with a type 2 vaccine alone, or concurrent vaccination with both a type 1 and a type 2 vaccine?
In a paper summarised on p 291 of this issue of Veterinary Record, Choi and others (2016), from a research group lead by Chanhee Chae, compare commercial type 1 and type 2 PRRSV vaccines against heterologous dual challenge, adding to papers already published by this research group investigating the pathogenicity of type 1 and type 2 PRRSV coinfection as well as vaccination strategies.
Pathogenesis of single or dual infections with type 1 and type 2 PRRSVs
A type 1 PRRSV isolate SNUVR090485 (isolated in Korea in 2009) and a type 2 PRRSV isolate SNUVR090851 (isolated in Korea in 2010) were compared for their pathogenicity in the form of single or dual infections in three-week-old conventional pigs infected via the intranasal inoculation route …