Porcine Circovirus 3 Detection in Aborted Fetuses and Stillborn Piglets from Swine Reproductive Failure Cases

Abstract

Porcine circovirus 3 (PCV-3) has been widely detected in healthy and diseased pigs; among different pathologic conditions, the strongest evidence of association comes from reproductive disease cases. However, simple viral detection does not imply the causality of the clinical conditions. Detection of PCV-3 within lesions may provide stronger evidence of causality. Thus, this study aimed to assess the frequency of PCV-3 detection in tissues from fetuses/stillborn piglets in cases of reproductive problems in domestic swine, as well as the histopathologic assessment of fetal tissues. Fetuses or stillborn piglets from 53 cases of reproductive failure were collected and analyzed by PCV-3 qPCR. The presence of porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus 2 (PCV-2), and porcine parvovirus 1 (PPV1) was also checked. PCV-3 qPCR positive samples with a high viral load were tested by PCV-3 in situ hybridization (ISH), sequenced, and phylogenetically analyzed. PCV-3 DNA was detected in 18/53 (33.9%) reproductive failure cases and in 16 of them PCV-3 was the only pathogen found. PCV-2 DNA was found in 5/53 (9.4%), PRRSV RNA in 4/53 (7.5%) and PPV1 was not detected. Four out of the six PCV-3 qPCR-positive cases with Ct value <30 were positive when tested by ISH. In these samples, PCV-3 was detected within mild histopathologic lesions, such as arteritis and periarteritis in multiple tissues. The present work emphasizes the need to include PCV-3 as a potential causative agent of reproductive failure in swine.

Recent Progress on Epidemiology and Pathobiology of Porcine Circovirus 3

“…PCV3 can be detected in the gilt of the pro-farrowing and farrowing period, in serum or tissues of weak-born piglets, in mummified fetuses and placenta, in the precolostrum sera of piglets and colostrum, suggesting the virus is associated with the reproductive disorders [33,48,74,[80][81][82]. Among the collected samples, the highest load of the PCV3 genome was detected in the thymus and lymph nodes of aborted and weak-born piglets [83].…”

Porcine circovirus 3 (PCV‐3) as a causal agent of disease in swine and a proposal of PCV‐3 associated disease case definition

“…Based on the general reluctance to accept that PCV-2 was truly pathogenic for swine at that time (Segalés et al, 2013), such demanding case definition guaranteed the necessary strictness and was found acceptable for most members of In any case, and following the path paved by PCV-2 diagnostic approach (Segalés, 2012), the existence of PCV-3 associated disease (PCV-3-AD) diagnostic criteria would help in placing the novel virus into the general context of swine disorders. Therefore, based on existing information that provide clinical, pathological and virological assessments of PCV-3 infection cases (Arruda et al, 2019;Kim, Park, et al, 2018;Phan et al, 2016;Saporiti et al, 2021), the authors would like to propose two major disease outcomes related with PCV-3 infection: PCV-3-reproductive disease (PCV-3-RD) in sows and fetuses/neonatal piglets and PCV-3-systemic disease (PCV-3-SD)…”

What do we know about porcine circovirus 3 (PCV3) diagnosis so far?: A review

“…PCV3 nucleic acid has been demonstrated in splenic arterial leiomyocytes and necrotic cells, renal artery, tubular epithelial cells, intestinal epithelial cells and inflammatory cells in lamina propria, hepatic lobular stroma and sinus antral wall, myocardial fibres, tissues and vascular contents; as well as foetal lung and cerebral samples with no apparent histopathologic lesions (Hou et al, 2020;Jiang, Wang et al, 2019;Palinski et al, 2017;Saporiti et al, 2021).…”