High Co-infection Status of Novel Porcine Parvovirus 7 With Porcine Circovirus 3 in Sows That Experienced Reproductive Failure

Abstract

Porcine parvoviruses (PPVs) and porcine circoviruses (PCVs) infect pigs worldwide, with PPV1–7 and PCV2 infections common in pigs. Although PPV7 was only identified in 2016, co-infection of PPV7 and PCV2 is already common, and PPV7 may stimulate PCV2 replication. PCV3, a novel type of circovirus, is prevalent in pig populations worldwide and considered to cause reproductive disorders and dermatitis nephrotic syndrome. In recent studies, pigs were commonly infected with both PCV3 and PPV7. Our objective was to investigate the co-infections between PPV7 and PCV3 in samples from swine on farms in Hunan, China, and assess the potential impacts of PPV7 on PCV3 viremia. A total of 209 samples, known to be positive (105) or negative (104) for PCV3, were randomly selected from serum samples that were collected from commercial swine herds in seven regions from 2016 to 2018 in our previous studies; these samples were subjected to real-time PCR to detect PPV7. Of these samples, 23% (48/209) were positive for PPV7. Furthermore, the PPV7 positive rate was significantly higher in PCV3 positive serum (31.4%, 33/105) than in PCV3 negative serum (14.4%, 15/104). Another 62 PCV3 positive sow serum samples and 20 PCV3 positive aborted fetuses were selected from 2015 to 2016 in our other previous study. These samples were designated as being from farms with or without long-standing histories of reproductive failure (RF or non-RF), respectively, and they were also subjected to real-time PCR to detect PPV7 and to determine whether PPV7 affected PCV3 viremia. Among the 62 serum samples (39 PCV3 positive RF-serum and 23 PCV3 positive non-RF-serum), 45.1% (28/62) were positive for PPV7 and PCV3, and the PPV7 positive rate was significantly higher in PCV3 positive RF-serum (51.2%, 20/39) than in PCV3 positive non-RF-serum (34.8%, 8/23). In addition, there was a higher positive rate of PPV7 (55%, 11/20) in PCV3 positive aborted fetus samples. In addition, the copy number of PCV3 in PPV7 positive samples was significantly higher than that in PPV7 negative serum samples. Based on these findings, we concluded that PPV7 may stimulate PCV3 replication.

Canine Circovirus Suppresses the Type I Interferon Response and Protein Expression but Promotes CPV-2 Replication

“…For example, pigs coinfected with PCV2 and porcine parvovirus (PPV) became dull, developed jaundice and hepatomegaly, and some even died [ 32 ]. Coinfection of PCV2 or PCV3 with PPV leads to severe viremia and reproductive disorders [ 33 , 34 , 35 ]. In addition, PCV-2 infection inhibits the response of immune-related signaling pathways and promotes the replication of viruses such as pseudorabies virus and porcine reproductive and respiratory syndrome virus [ 36 , 37 ].…”

Recent Progress on Epidemiology and Pathobiology of Porcine Circovirus 3

“…Moreover, co-infections of PCV3 with other pathogens may also lead to reproductive failure or even increase the severity of the disease [80,82,84]. As reported by Dal Santo et al, 93.1% of 270 PCV3-positive mummified fetuses were co-infected with PPV, PCV2, and/or Leptospira spp.…”

“…[80]. Mai et al also found that the positive rates of PPV7 in PCV3-positive reproductive failure-serum and PCV3-positive aborted fetus samples were significantly higher than that of the PCV3-positive non-reproductive failure serum samples [84]. Meanwhile, the positive rates of PCV3 in PPV7-positive samples were obviously higher than that of the PPV7-negative samples [84].…”

Detection and Molecular Characterization of Porcine Parvovirus 7 in Eastern Inner Mongolia Autonomous Region, China

“…The prevalence of PPV7 in China has been examined by different researchers, and the prevalence varies. It is 32.8% (21/64) in Guangdong ( 12 ), 27.3% (105/385) in Guangxi ( 16 ), 20% (24/120) to 74% (148/200) in Anhui ( 17 , 19 , 25 ), 23% (48/209) in Hunan ( 18 ) and 15.4% (67/435) for samples collected in Xinjiang, Hebei, Shandong, Henan, Jiangsu, Anhui, Fujian and Guangdong ( 20 ). However, information concerning the prevalence and genetic evolution of PPV7 is still limited.…”

“…Similarly, it has been reported that the PPV7 positive rate in PCV3 positive serum was significantly higher than that in PCV3 negative serum. Furthermore, the copy number of PCV3 in PPV7 positive samples was significantly higher than that in PPV7 negative serum samples, indicating that PPV7 may be a co-acting factor for PCV3 replication ( 18 ). High coinfection rates of PPV7 and PCV2, or PPV7 and PCV3 were also observed in our study.…”