Porcine circovirus 2-genotypes in fetuses from litters suspicious for stillbirth, mummification, and embryonic death syndrome (SMEDI) in Germany

Abstract

Objective

The present study examined the occurrence of the 3 major genotypes of porcine circovirus 2 (PCV2a, PCV2b, PCV2d) in tissue samples from fetuses origination from litters suspicious for stillbirth, mummification, embryonic death, and infertility syndrome (SMEDI) affected litters from Germany.

Material and methods

A total of 53 litters suspicious for SMEDI of 27 farms with a total of 469 fetuses sent in for diagnostic purposes between 2021–2023 from veterinarians in the field were available for the present examination. Veterinarians were asked to submit all dead piglets of SMEDI-litters to allow random sampling. Four fetuses per litter were randomly selected for the study. In total, 209 fetuses were examined by qPCR for PCV2 DNA and in case of a positive result, further genotyped by PCV2 genotype-specific qPCR or sequencing of the open reading frame 2. Farm specific data was collected on a voluntary base and included in the analyses.

Results

In total 40.7% (11/27) of farms, 37.7% of litters (20/53) and 21.1% (44/209) of fetuses were positive for PCV2 DNA. Genotyping by qPCR was successful in 37 PCV2 positive tissue samples. For 4 additional samples, sequencing of PCV2 DNA was performed to support the genotype assignment. After all, 29.6% (8/27) of farms, 30.2% (16/53) of litters and 19.1% (40/209) of fetuses were positive for PCV2d. One farm (3.7%) had a PCV2a+PCV2d positive fetus (0.5%) in one litter (1.9%).

Conclusions

PCV2d could be identified as the main PCV2 genotype in SMEDI-associated fetuses. This finding is in line with the overall observed genotype shift toward PCV2d as the predominating PCV2 genotype in the domestic pig population not only in Germany but also in most all relevant pig producing countries worldwide. Moreover, these findings also indicate that diaplacental transmission may play a major role in the spread of PCV2 to downstream pig populations and thus, also for the observed genotype shift. The high Cq-values in tissue samples indicated that PCV2 was not the etiological pathogen in most cases.

Clinical relevance

The occurrence of SMEDI in a piglet producing herd needs diagnostic attention and may also include PCV2 diagnostics including genotyping in PCV2 associated cases. This approach could enable adjustment of the vaccination protocol on farm level and early detection of newly introduced PCV2 genotype in a pig herd.

Zusammenfassung

Ziel

In der vorliegenden Studie wurde das Vorkommen der in Europa vorherrschenden PCV2-Genotypen (PCV2a, PCV2b, PCV2d) in Gewebeproben von SMEDI-assoziierten Feten untersucht.

Material und Methoden

Für die vorliegende Untersuchung standen insgesamt 53 SMEDI-verdächtige Würfe aus 27 Betrieben mit insgesamt 469 Föten zur Verfügung, die zwischen 2021 und 2023 von Tierärzten zu diagnostischen Zwecken eingeschickt wurden. Für die Studie wurden nur Einsendungen ganzer Würfe (nur tot geborene Föten) berücksichtigt. Es wurden pro Wurf 4 Föten nach dem Zufallsprinzip für die Studie ausgewählt und somit insgesamt 209 Föten mittels qPCR auf PCV2-DNA untersucht. Im Falle eines positiven Ergebnisses wurde eine PCV2-Genotyp-spezifische qPCR oder die Sequenzierung des Open Reading Frame 2 zur Genotypisierung durchgeführt. Zusätzlich wurden bestandsspezifische Daten auf freiwilliger Basis erhoben und in die Analyse einbezogen.

Ergebnisse

Insgesamt waren 40,7% (11/27) der Betriebe, 37,7% der Würfe (20/53) und 21,1% (44/209) der Föten positiv für PCV2-DNA. Die Genotypisierung mittels PCR war bei 37 PCV2-positiven Gewebeproben möglich. Bei 4 weiteren Proben wurde eine Sequenzierung der PCV2-DNA durchgeführt, um die korrekte Genotypen-Zuordnung abzusichern. Insgesamt waren 29,6% (8/27) der Betriebe, 30,2% (16/53) der Würfe und 19,1% (40/209) der Föten positiv für PCV2d. In einem Betrieb (3,7%) konnte in einem positiven Fötus (0,5%) eines Wurfes (1,9%) gleichzeitig PCV2a und PCV2d nachgewiesen werden.

Schlussfolgerung

PCV2d konnte als der vorherrschende PCV2-Genotyp bei SMEDI-assoziierten Föten identifiziert werden. Dieses Ergebnis steht im Einklang mit dem global beobachteten Genotypen-Shift mit PCV2d als derzeit vorherrschendem PCV2-Genotyp in der Hausschweinepopulation. Darüber hinaus deuten diese Ergebnisse auch darauf hin, dass die diaplazentare Übertragung von PCV2 eine wichtige Rolle bei der Ausbreitung des Virus auf nachgelagerte Produktionsstufen spielen könnte und so auch für die Veränderung des Vorkommens von PCV2 Genotypen in Hausschweinepopulationen von Bedeutung ist. Die hohen Cq-Werte in fetalen Gewebeproben deuten darauf hin, dass PCV2 in den meisten Fällen nicht das ätiologische Agens für das klinische Bild darstellte.

Klinische Relevanz

Das Auftreten von SMEDI in Ferkelerzeugerbetrieben erfordert diagnostische Aufmerksamkeit und sollte auch eine PCV2-Diagnostik einschließlich Genotypisierung umfassen. Dieser Ansatz könnte die Anpassung des Impfschemas auf Bestandsebene und die frühzeitige Erkennung eines neu eingeschleppten PCV2-Genotyps in einem Schweinebestand ermöglichen.

Keywords

Porcine circovirus 2 - genotypes - reproductive disorder - SMEDI syndrome - sows - pigs

Schlüsselwörter

Porzines Circovirus 2 - Genotypen - Reproduktionsstörungen - SMEDI-Syndrom - Sauen - Schweine

Publication History

Received: 15 May 2025

Accepted: 09 September 2025

Article published online:
15 December 2025

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