Epidemiology and Evolution of Emerging Porcine Circovirus-like Viruses in Pigs with Hemorrhagic Dysentery and Diarrhea Symptoms in Central China from 2018 to 2021

Abstract

Porcine circovirus-like virus (PCLV) is a type of circular Rep-encoding single-stranded DNA virus and may be associated with the development of diarrheal symptoms in pigs. In this study, we retrospectively analyzed three years of past cases in Anhui, China, and reported a case of hemorrhagic enteritis and death in a pregnant sow possibly caused by PCLV. In addition, we analyzed the evolutionary characteristics of PCLV and found that mutation, recombination and selective pressure all played an important role in the evolution of PCLV. We identified N15D and T17S as well as L56T, T58R, K59Q, M62R, L75I and R190K mutations in two different branches, and we noted recombination events in the Rep of a group of Chinese strains. Analysis of selection pressure revealed that PCLV gained more positive selection, indicating that the virus is in a continuous evolutionary state. The PR2 plot, ENC-plot and neutrality analysis showed a greater role of natural selection than that of mutational pressure in the formation of codon usage patterns. This study is the first to identify PCLV in sows with hemorrhagic dysentery and death, and it provides new epidemiological information on PCLV infection in pigs in China.

Current Understanding of the Pathogenesis of Porcine Circovirus 3

“…Respiratory diseases and diarrhea can be found in naturally infected pigs [10,11,42], though those might not be considered as the major clinical signs following PCV3 infection and various factors could contribute to the clinical signs. Therefore, the ability of PCV3 to induce respiratory disease and diarrhea is still questionable.…”

“…Long term viremia or infection could render the infected animals more prone to secondary infection, which was also observed in PCV3 infection [11]. It should be noted that it is still possible that the presence of the PCV3 DNA might not accurately reflect virion production, as in the case of porcine circovirus-like viruses [42]. Duration of PCV3 infection, chronic PCV3 infection, and coinfection with other pathogens should be studied.…”

The Prevalence of Porcine Circovirus-like Viruses in China Presents New Challenges to the Diagnosis of Diarrhea-Associated Viruses. Comment on Yang et al. Epidemiology and Evolution of Emerging Porcine Circovirus-like Viruses in Pigs with Hemorrhagic Dysentery and Diarrhea Symptoms in Central China from 2018 to 2021. Viruses 2021, 13, 2282

“…Recently, a report in Viruses has highlighted the problem of porcine circovirus-like (PCL) virus [ 1 ]. PCLV is a novel circular replication-associated protein (Rep)-encoding single stranded (CRESS) DNA virus, which was first identified in swine fecal samples in the United States in 2011 [ 2 ].…”

“…In February 2022, we also identified PCLV from fecal swabs of 5-day-old piglets in Hunan Province (data not shown). It is worth noting that PCLV was identified for the first time in dead sows suffering from porcine epidemic diarrhea virus (PEDV) in Anhui province in 2021, providing new epidemiological information for adult pigs infected with PCLV ( Figure 1 ) [ 1 ].…”

“…Viral diarrheal diseases caused by various swine diarrhea etiologies and co-infections with multiple viruses are very common in diarrheal pigs [ 2 , 6 ]. Current research has shown that PCLV virus is co-infected with other viruses, such as porcine circovirus 2 (PCV-2), porcine parvovirus (PPV) and PEDV [ 1 , 4 , 5 ]. Some co-infection cases caused the death of piglets [ 1 ].…”