A Comparison of Virulence of Three Porcine Circovirus Type 2 (PCV2) Genotypes (a, b, and d) in Pigs Singularly Inoculated with PCV2 and Dually Inoculated with PCV2 and Porcine Reproductive and Respiratory Syndrome Virus

Abstract

The aim of this study was to compare the virulence of porcine circovirus type 2 (PCV2) genotypes in dually inoculated pigs with both three genotypes (a, b, and d) of PCV2 and porcine reproductive and respiratory syndrome virus-2 (PRRSV-2) versus pigs singularly inoculated with the same three PCV2 genotypes (a, b, and d). Differences in this comparison were found in PCV2 viremia levels, lung and lymphoid lesion severity, and the amount of PCV2 antigen within the lymphoid lesions. Regardless of PCV2 genotypes, pigs that were dually inoculated with PCV2/PRRSV had significantly higher clinical scores, less average daily weight gain, higher levels of PCV2 viremia, and more severe lug and lymphoid lesions compared to pigs singularly inoculated with PCV2. Among the dually infected pig groups, pigs infected with PCV2d/PRRSV-2 had significantly higher levels of PCV2 viremia, more severe lung and lymphoid lesions, and more PCV2-positive cells within lymphoid lesions compared to pigs dually inoculated with PCV2a/PRRSV-2 and PCV2b/PRRSV-2. The results of this study demonstrated significant differences in the virulence among dual inoculation of PCV2a/PRRSV-2, PCV2b/PRRSV-2, and PCV2d/PRRSV-2. A significant difference in the virulence among PCV2a, PCV2b, and PCV2d single-inoculated pig groups was not found with respect to the levels of PCV2 viremia and production of PCV2-associated lymphoid lesions.

Prevalence and genetic diversity of porcine circovirus type 2 in Henan Province of China during 2020-2023

“…PCV2 has been prevalent in pig populations in China for many years 5 . PCVADs is considered a major factor threatening the swine industry 2,24,27 . International breeding pig transportation, natural virus evolution and vaccine pressure are often considered the reason for the rapid evolution of PCV2 28 .…”

Revisiting Porcine Circovirus Infection: Recent Insights and Its Significance in the Piggery Sector

“…A study by Suh et al (2021) proved that PCV2a, PCV2b, and PCV2d show significant differences in virulence when co-infected with PRRSV-2, whereas no significant virulence difference was seen when each genotype infected solely. PCV2d was more virulent than PCV2a and PCV2b in a dual-infection model [ 142 ]. Another experiment involving M. hyopneumoniae as a co-infecting agent revealed the same results [ 143 ].…”

“…Another experiment involving M. hyopneumoniae as a co-infecting agent revealed the same results [ 143 ]. Such co-infectious agents might potentiate the replication of PCV2d, as reflected in greater severity in lymphoid lesions [ 142 , 143 ]. Therefore, further studies are essential to explore the relation of the genotype, isolate, or co-infecting agents with the pathogenic expression of PCV2 infection.…”

Phylogenetic and Structural Analysis of Porcine Circovirus Type 2 from 2016 to 2021 in Jilin Province, China

“…To date, considerable evidence shows that PCV2d has gradually replaced PCV2b as the predominant genotype globally or circulates as a co-infection with PCV2b in some areas or countries [10][11][12]. Furthermore, although there was no significant difference in the level of PCV2 viremia and the occurrence of PCV2-related lymphopathy in pigs inoculated with PCV2a, PCV2b, and PCV2d, the co-infection with other pathogens, such as Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus, might enhance the PCV2-related diseases [13,14]. Therefore, it is necessary to continuously monitor and genotype PCV2 to evaluate the epidemic and adopt an appropriate strategy to prevent and control the disease.…”