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

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.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.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%).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.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.