Litters of Various-Sized Mummies (LVSM) and Stillborns after Porcine Reproductive and Respiratory Syndrome Virus Type 1 Infection-A Case Report

Simple Summary In an Austrian piglet-producing farm, sudden occurrences of mummified foetuses of various sizes and stillborn piglets were observed, and date of births were delayed in more than 50% of the sows in the respective farrowing group. There are a few pathogens known to be involved in pathogenesis of this particular clinical picture, called SMEDI (short for "stillbirth, mummification, embryonic death and infertility"). All of them were included in the diagnostic work-up of three litters consisting of mummies and stillborns, but were not detected. Instead, high viral loads of the porcine reproductive and respiratory syndrome virus (PRRSV), a virus known to be involved in the aetiology of a variety of clinical signs in pigs, but not in the one of papyraceous mummifications, were found. This once more shows the variability of the clinical outcome of this pathogen.Diverse origins and causes are described for papyraceous mummifications of porcine foetuses, but the porcine reproductive and respiratory syndrome virus (PRRSV) is not one of them. In contrast, PRRSV is unlikely to cause mid-term placental transmission but may cause late-term abortions and weakness of piglets. This case report describes a sudden occurrence of mummified foetuses of various sizes and stillborns and delayed birth (>115 days) in more than 50% of sows from one farrowing batch, while newborn piglets were mostly vital. Neither increased embryonic death nor infertility was reported. Three litters with mummies, autolysed piglets and stillborn piglets were investigated, and infections with porcine parvoviruses, porcine teschoviruses, porcine circoviruses, encephalomyocarditis virus, Leptospira spp. and Chlamydia spp. were excluded. Instead, high viral loads of PRRSV were detected in the thymus pools of piglets at all developmental stages, even in piglets with a crown-rump length between 80 and 150 mm, suggesting a potential mid-term in utero transmission of the virus. Genomic regions encoding structural proteins (ORF2-7) of the virus were sequenced and identified the virulent PRRSV-1 strain AUT15-33 as the closest relative. This case report confirms the diversity of PRRSV and its potential involvement in foetal death in mid-gestation.