The Thai Journal of Veterinary Medicine


Ten selected Thai isolates of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) were amplified in an open reading frame 5 by a reverse, transcriptase, polymerase chain reaction (RT-PCR) and cut with restriction enzymes: MluI, HincII, SacII and HaeIII for the US genotype and PstI, HaeII and ClaI for the EU genotype. None of the field isolates had a similar cutting pattern when compared to modified live virus vaccines, however, several cutting patterns were obtained from this study. The results suggested that genetic variation was present among the Thai isolates, even within the same genotype. The variations may be the result of the introduction of a new variant into the endemic area or by local evolution.

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