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Porcine reproductive and respiratory syndrome virus (PRRSV) is considered an important economic pathogen for the international swine industry. At present, both PRRSV-1 and PRRSV-2 have been confirmed to be co-circulating in China. However, there is little available information about the prevalence or distribution of PRRSV-1 in Guangdong province, southern China. In this study, we performed molecular detection of PRRSV-1 in 750 samples collected from 50 farms in 15 major pig farming regions in this province. After RT-PCR testing, 64% (32/50) of farms were confirmed as PRRSV-1-positive. Surprisingly, PRRSV-1 was circulating on at least one pig farm in all 15 regions; of the 750 samples, 186 samples (24.8%) were positive for PRRSV-1. Furthermore, 15 representative PRRSV-1 ORF5 sequences (606 bp) (n = 1 per region) were obtained from those PRRSV-1-positive regions. Sequence alignment analysis indicated that they shared 81.8% ~ 100% nucleotide and 81.2% ~ 100% amino acid similarity with each other. Although all current PRRSV-1 sequences were divided into pandemic subtype 1, most of them had unique glycoprotein-5 amino acid sequences that are significantly different from other known PRRSV-1 isolates. To conclude, the present findings revealed wide geographical distribution of PRRSV-1 in Guangdong province, southern China. This study further extends the epidemiological significance of PRRSV-1 in China.

Members of the family Anelloviridae are emerging circular DNA viruses infecting many species of vertebrates including pigs. To date, members of two distinct genera, Iotatorquevirus, including torque teno sus virus 1a and torque teno sus virus 1b (TTSuV1a and TTSuV1b), and Kappatorquevirus, including torque teno sus virus k2a and torque teno sus virus k2b (TTSuVk2a and TTSuVk2b), have been identified in domestic pigs and wild boars. The goal of this study was to evaluate the prevalence and genetic diversity of these viruses based on 5' non-coding genes in Chinese swine herds experiencing clinical symptoms. One hundred eighty-five clinical samples from 11 different regions, collected during 2008-2009, were analyzed using a PCR method, and the results revealed a high TTSuV-positive rate of 78.9 % (146/185) in pigs. Moreover, we detected co-infection with multiple TTSuV strains in the same pig. Nucleotide sequencing results revealed greater genetic diversity within the genus Kappatorquevirus than within the genus Iotatorquevirus. In addition, TTSuVk2b, a novel virus discovered in New Zealand in 2012, was also identified in this study. In summary, the present work helps us obtain more knowledge about the epidemiology and genetic diversity of TTSuVs.

Background Following the initial isolation of porcine deltacoronavirus (PDCoV) from pigs with diarrheal disease in the United States in 2014, the virus has been detected on swine farms in some provinces of China. To date, little is known about the molecular epidemiology of PDCoV in southern China where major swine production is operated. Results To investigate the prevalence of PDCoV in this region and compare its activity to other enteric disease of swine caused by porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis coronavirus (TGEV), and porcine rotavirus group C (Rota C), 390 fecal samples were collected from swine of various ages from 15 swine farms with reported diarrhea. Fecal samples were tested by reverse transcription-PCR (RT-PCR) that targeted PDCoV, PEDV, TGEV, and Rota C, respectively. PDCoV was detected exclusively from nursing piglets with an overall prevalence of approximate 1.28 % (5/390), not in suckling and fattening piglets. Interestingly, all of PDCoV-positive samples were from 2015 rather than 2012–2014. Despite a low detection rate, PDCoV emerged in each province/region of southern China. In addition, compared to TGEV (1.54 %, 5/390) or Rota C (1.28 %, 6/390), there were highly detection rates of PEDV (22.6 %, 88/390) in those samples. Notably, all five PDCoV-positive piglets were co-infected by PEDV. Furthermore, phylogenetic analysis of spike (S) and nucleocapsid (N) gene sequences of PDCoVs revealed that currently circulating PDCoVs in southern China were more closely related to other Chinese strains of PDCoVs than to those reported in United States, South Korea and Thailand. Conclusions This study demonstrated that PDCoV was present in southern China despite the low prevalence, and supported an evolutionary theory of geographical clustering of PDCoVs. Electronic supplementary material The online version of this article (doi:10.1186/s12985-016-0591-6) contains supplementary material, which is available to authorized users.

Currently, porcine circovirus type 2 (PCV2) is considered the major pathogen of porcine circovirus associated-diseases (PCVAD) that causes large economic losses for the swine industry in the world annually, including China. Since the first report of PCV2 in 1998, it has been drawing tremendous attention for the government, farming enterprises, farmers, and veterinary practitioners. Chinese researchers have conducted a number of molecular epidemiological work on PCV2 by molecular approaches in the past several years, which has resulted in the identification of novel PCV2 genotypes and PCV2-like agents as well as the description of new prevalence patterns. Since late 2009, commercial PCV2 vaccines, including the subunit vaccines and inactivated vaccines, have already been used in Chinese swine farms. The aim of this review is to update the insights into the prevalence and control of PCV2 in China, which would contribute to understanding the epidemiology, control measures and design of novel vaccines for PCV2.