Revisiting Porcine Circovirus Disease Diagnostic Criteria in the Current Porcine Circovirus 2 Epidemiological Context

Abstract

Current knowledge on porcine circovirus diseases (PCVD) caused by Porcine circovirus 2 (PCV-2) includes the subclinical infection (PCV-2-SI), systemic (PCV-2-SD) and reproductive (PCV-2-RD) diseases, and porcine dermatitis and nephropathy syndrome (PDNS). Criteria to establish the diagnosis of these conditions have not changed over the years; thus, the triad composed by clinical signs, lesions and viral detection in lesions are still the hallmark for PCV-2-SD and PCV-2-RD. In contrast, PCV-2-SI diagnosis is not usually performed since this condition is perceived to be controlled by default through vaccination. PDNS is diagnosed by gross and histopathological findings, and PCV-2 detection is not recognized as a diagnostic criterion. Molecular biology methods as a proxy for PCVD diagnoses have been extensively used in the last decade, although these techniques should be mainly considered as monitoring tools rather than diagnostic ones. What has changed over the years is the epidemiological picture of PCV-2 through the massive use of vaccination, which allowed the decrease in infectious pressure paralleled with a decrease in overall herd immunity. Consequently, the need for establishing the diagnosis of PCVD has increased lately, especially in cases with a PCV-2-SD-like condition despite vaccination. Therefore, the objective of the present review is to update the current knowledge on diagnostic criteria for PCVDs and to contextualize the interest of using molecular biology methods in the overall picture of these diseases within variable epidemiological scenarios of PCV-2 infection.

High Rates of Detection and Molecular Characterization of Porcine Adenovirus Serotype 5 (Porcine mastadenovirus C) from Diarrheic Pigs

“…To our knowledge, the present study is the first report on high rates of detection (25.74%, 26/101) and molecular characterization of PAdV-5 ( PAdV-C ) from diarrheic pigs, although the virus has been previously identified in a few fecal samples from healthy pigs [ 17 , 18 ], indicating potential infection of the porcine GI tract. Since most of the PAdV-5 positive pigs were infected with PCV2 (associated with porcine enteritis [ 29 ]), and the samples were not screened for other enteric pathogens (except for PCV2 and RVA), we could not establish whether PAdV-5 caused GI disease in the pigs. After a long gap (more than 3 decades), the full-length CDS for two important PAdV-5 proteins (hexon and pol) were analyzed, revealing nearly absolute sequence identities between PAdV-5 strains (HNF-70, GES7 and Z11) detected in different parts of the world (Japan (Asia), and the Dominican Republic (Caribbean region)) and during different time periods (1987 and 2020-2021).…”

Porcine Lawsonia intracellularis Ileitis in Italy and Its Association with Porcine Circovirus Type 2 (PCV2) Infection

“…In the caseload of this study, a higher frequency of acute cases sharing both infections was observed, supporting the hypothesis that when infection by ubiquitous pathogens such as L. intracellularis occurs, it contributes to an increased likelihood of PCV2 replication, creating an opportunity to switch from subclinical to clinical PCV2 disease. However, doubts have been raised about the actual existence of PCV2 intestinal and lung diseases [ 24 ], as almost all lung and intestinal involvement is associated with systemic lymphoid lesions that lead to a diagnosis of systemic PCV2 disease when other lymphoid organs are available for histology. It is unknown if the PCV2-positive enteritis described in this study represents actual PCVD-enteric disease, as data on other target tissues were unavailable.…”

Abortion and fetal death in sows

“…Infections with PCV‐2 have been associated with a number of conditions collectively known as porcine circovirus disease (Segalés & Sibila, 2022). PCV‐3, since its first recovery in 2015, has received considerable research attention (Phan et al, 2016).…”