RESUMEN
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important porcine viruses worldwide. Recently, severe PRRS outbreaks had occurred in two farms located in eastern and southern Thailand where stringent vaccination had been routinely practiced. Genetic analysis of GP5 identified two highly virulent PRRSVs designated as NA/TH/S001/2015 and NA/TH/E001/2016 from the southern and eastern farms, respectively. Both incidences were the first outbreaks of severe PRRSV since the implementation of the modified live virus (MLV) vaccine, indicating the concurrent emergence of immune-escape viruses. The genetics of the two PRRSV variants, the previous studied sequences from Thailand, and the reference strains were characterized with a focus on the GP5 and NSP2 genes. The results indicated that NA/TH/S001/2015 and NA/TH/E001/2016 shared less than 87% nucleotide similarity to the MLV and PRRSV type 2, lineages 1 and 8.7 (NA), respectively. A comparative analysis of the retrospective GP5 sequences categorized the PRRSVs into five groups based on the clinical outcomes, and both of the novel PRRSV strains were in the same group. Epitope A, T cell epitope, and N-linked glycosylation patterns within GP5 of both PRRSV variants were highly variable and significantly differed from those of MLV. As observed in highly virulent type 2 strains, NA/TH/S001/2015 contained a single amino acid deletion at position 33 in the hypervariable region 1 (HV-1) of GP5. Amino acid analysis of the hypervariable region of NSP2 revealed that NA/TH/E001/2016 had a unique deletion pattern that included two discontinuous deletions: a 127-amino acid deletion from residues 301 to 427 and a single amino acid deletion at position 470. These results indicate the emergence of two novel PRRSV strains and highlight the common genetic characteristics of the immune-escaping PRRSV variants.
Asunto(s)
Programas de Inmunización , Síndrome Respiratorio y de la Reproducción Porcina/prevención & control , Virus del Síndrome Respiratorio y Reproductivo Porcino/genética , Proteínas del Envoltorio Viral/genética , Proteínas no Estructurales Virales/genética , Vacunas Virales/inmunología , Secuencia de Aminoácidos , Animales , Epítopos de Linfocito T/inmunología , Granjas , Variación Genética/genética , Virus del Síndrome Respiratorio y Reproductivo Porcino/clasificación , Virus del Síndrome Respiratorio y Reproductivo Porcino/inmunología , Estudios Retrospectivos , Eliminación de Secuencia/genética , Porcinos , Tailandia , VacunaciónRESUMEN
Since 2013, outbreaks of disease caused by duck Tembusu virus (DTMUV) have been observed in layer and broiler duck farms in Thailand. The virus is closely related to Chinese DTMUVs and belongs to the Ntaya group of mosquitoborne flaviviruses. These findings represent the emergence of DTMUV in ducks in Thailand.
Asunto(s)
Patos/virología , Flaviviridae/genética , Flaviviridae/patogenicidad , Infecciones por Flavivirus/genética , Animales , Flaviviridae/aislamiento & purificación , Infecciones por Flavivirus/epidemiología , Genoma Viral , Filogenia , Enfermedades de las Aves de Corral/virología , Tailandia/epidemiologíaRESUMEN
Porcine reproductive and respiratory syndrome virus (PRRSV) affects the swine industry worldwide. Annual surveillances taken from 2008 to 2013 revealed a 13.86% prevalence of PRRSVs in swine populations in Thailand. The selected positive samples were genetically characterized based on global systems and phylogenetic trees that were constructed using 967 ORF5 samples from this study, the collective sequences from Thailand and Southeast Asia and reference sequences. The results showed that both types I and II have been circulating in Thai swine and that genotype II was more prevalent than genotype I. Only type II was found in other countries in Southeast Asia. Type I PRRSVs from Thailand are clustered in subtype 1, clades A, D and H. Type II PRRSVs are topologically classified in lineage 1 and sublineages 5.1, 5.2 and 8.7, of which sublineage 8.7 was predominant, especially after 2010. PRRSVs in sublineage 8.7 are divided into two groups: classical NA and HP-PRRSV. An analysis of all HP-PRRSVs in Southeast Asia revealed four separate clades--A (SX2009-like), B (09HEN1-like), JXA1-like and GXFCH08-like--reflecting four different introductions of these viruses into Thailand, Lao PDR, Cambodia and Vietnam. HP-PRRSV first appeared in Thailand and Cambodia in 2008, 2 years before the first epidemic outbreaks. Recently, the genetics of PRRSVs in Southeast Asia have become more diverse. Thus, PRRSV genetics must be continually characterized and phylogenetically analyzed using global systematic classifications to provide annual genetic information for PRRS control and vaccine selection.