Asunto(s)
Síndrome Respiratorio y de la Reproducción Porcina/epidemiología , Virus del Síndrome Respiratorio y Reproductivo Porcino/clasificación , Crianza de Animales Domésticos/historia , Animales , Historia del Siglo XX , Historia del Siglo XXI , América del Norte/epidemiología , Vigilancia de la Población , Síndrome Respiratorio y de la Reproducción Porcina/prevención & control , Síndrome Respiratorio y de la Reproducción Porcina/transmisión , Virus del Síndrome Respiratorio y Reproductivo Porcino/genética , Virus del Síndrome Respiratorio y Reproductivo Porcino/aislamiento & purificación , PorcinosRESUMEN
We conducted an experiment to determine the ability of vaccine against Porcine reproductive and respiratory syndrome virus (PRRSV) to reduce the transmission of PRRSV among pigs. At the end of the experiment, transmission rates did not differ significantly (P = 0.61) between the vaccinated and nonvaccinated pigs, the mean R-values being 0.598 (95% confidence interval [CI] 0.136 to 3.218) and 0.264 (95% CI 0.008 to 2.266), respectively. The unusually low rate of PRRSV transmission in both groups may not have provided a sufficient challenge to detect a vaccine effect. Several factors could affect the rate of PRRSV transmission: isolate virulence, inoculation dose, inoculation route, number of passages of the challenge virus in cell culture, and population size. Of these, isolate virulence appears to be the most important factor associated with the low transmissibility observed in this study. More studies comparing rates of transmission between PRRSV isolates with diverse levels of virulence are needed to better understand this association.
Asunto(s)
Síndrome Respiratorio y de la Reproducción Porcina , Virus del Síndrome Respiratorio y Reproductivo Porcino/patogenicidad , Vacunas Virales/inmunología , Animales , Relación Dosis-Respuesta Inmunológica , Densidad de Población , Síndrome Respiratorio y de la Reproducción Porcina/prevención & control , Síndrome Respiratorio y de la Reproducción Porcina/transmisión , Síndrome Respiratorio y de la Reproducción Porcina/virología , Distribución Aleatoria , Especificidad de la Especie , Porcinos , Factores de Tiempo , Vacunas Virales/administración & dosificación , VirulenciaRESUMEN
The objective of this study was to investigate whether geographic distance was correlated with genetic homology among isolates of Porcine reproductive and respiratory syndrome virus (PRRSV) from a single pork-producing company. We analyzed geographic distance, temporal distance, and percentage similarity in the PRRSV nucleotide sequence among 62 farms, applying the Mantel test for correlation between distance matrices and PRRSV sequencing. Genomic similarity had a significant (P < 0.01) negative (rM = -0.217) correlation with geographic distance. These findings indicate that, under the conditions of this study, the greater the distance between farms, the less the genetic homology among PRRSV isolates.