Ramos Natalia, Porley Dario, Mirazo Santiago, Castro Gustavo, Cabrera Karina, Lozano Alejandra, Arbiza Juan
Sección Virología, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
Área Suinos, Facultad de Veterinaria, Universidad de la República, Alberto Lasplaces 1550, Montevideo 11600, Uruguay.
Gene. 2017 Dec 30;637:230-238. doi: 10.1016/j.gene.2017.09.058. Epub 2017 Sep 28.
Porcine Circovirus type 2 (PCV2) is a worldwide distributed pathogen and one of the most economically relevant swine infections. Four genotypes have been recognized and it is well known that PCV2a, PCV2b and PCV2d have a global distribution. However, the information about recombinant strains circulation and their influence in driving PCV2 evolution is a poorly studied area. In Uruguay, PCV2 associated symptoms began to be frequently observed in pigs from different farms since 2010. The main purpose of this study was to thoroughly investigate the molecular epidemiology of PCV2 in nationwide swine herds and free-living wild boars during the period 2010-2014, providing an extensive viral sequence dataset. Surprisingly, the findings revealed a predominance of recombinant strains circulation, evidencing for the first time in the field that PCV2 recombination can lead to the emergence of strains able to compete and potentially displace parental ones. In addition, the circulation of the genotypes PCV2d (29%), PCV2b (10.5%) and PCV2a (7.9%) were also observed. Since 2013, a high circulation of PCV2d was identified in the country and probably reflected the recent global scenario of the emergence of this genotype. In addition, fluctuations in the frequency of PCV2 infection in the period evaluated may suggest a limitation of biosecurity strategies implemented in Uruguay for the disease control, including the instability of vaccination practices. On the other hand, the sustained PCV2 infection observed in wild boar population and the similarity among circulating viral strains from these animals and domestic pigs, suggested that wild animals could serve as permanent reservoir of the disease. Altogether, this work put forward that many factors play a role in PCV2 heterogeneity including rapid viral spread and evolution, recombination, wide movement within national boundaries and multiples introduction events resulting of international trade. Continuous monitoring of viral epidemiology is needed to better understand the PCV2 population dynamics in Uruguay and the development of appropriate strategies are required for disease control.
猪圆环病毒2型（PCV2）是一种在全球范围内分布的病原体，也是与猪相关的最具经济影响的感染之一。目前已识别出四种基因型，并且众所周知，PCV2a、PCV2b和PCV2d在全球均有分布。然而，关于重组毒株的传播及其在推动PCV2进化方面的影响，这一领域的研究较少。在乌拉圭，自2010年以来，不同农场的猪中开始频繁观察到与PCV2相关的症状。本研究的主要目的是全面调查2010年至2014年期间全国猪群和自由生活野猪中PCV2的分子流行病学，提供一个广泛的病毒序列数据集。令人惊讶的是，研究结果显示重组毒株的传播占主导地位，首次在实地证明PCV2重组可导致能够竞争并可能取代亲本毒株的毒株出现。此外，还观察到PCV2d（29%）、PCV2b（10.5%）和PCV2a（7.9%）基因型的传播。自2013年以来，该国发现PCV2d的高传播率，这可能反映了该基因型最近在全球出现的情况。此外，在所评估期间PCV2感染频率的波动可能表明乌拉圭为控制该疾病而实施的生物安全策略存在局限性，包括疫苗接种做法的不稳定。另一方面，在野猪种群中观察到持续的PCV2感染，以及这些动物与家猪中传播的病毒株之间的相似性，表明野生动物可能是该疾病的永久宿主。总之，这项工作表明，许多因素在PCV2的异质性中起作用，包括病毒的快速传播和进化、重组、国内的广泛流动以及国际贸易导致的多次引入事件。需要持续监测病毒流行病学，以更好地了解乌拉圭PCV2的种群动态，并需要制定适当的疾病控制策略。
