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ZusammenfassungIn einem Jungsauenerzeugerbetrieb in Niederösterreich traten über mehrere Jahre hinweg gehäuft Atemwegserkrankungen bei Jungsauen aus Eigenremontierung nach Einstallung in die Altsauenherde auf. Im Herbst 2019 wurden zudem Fruchtbarkeitsstörungen in Form von Spätaborten und Umrauschen beobachtet. Bei der Untersuchung von Nasentupfern mittels PCR auf Influenza-A-Virus (IAV) konnte bei 3 Jungsauen mit respiratorischer Symptomatik und Fieber der IAV-Subtyp H1avN1 nachgewiesen werden. Die Untersuchung der Serumproben dieser Tiere an 2 Zeitpunkten im Abstand von 3 Wochen ergab jedoch keinen Nachweis von Antikörpern im Hämagglutinationshemmtest (HAH), der standardmäßig im Labor verwendet wurde. Auch bei der Untersuchung von Sauen weiterer Altersgruppen waren keine eindeutigen Antikörpertiter gegenüber H1avN1 detektierbar. Nach Erweiterung des diagnostischen Panels des HAH um 7 H1avN1-Testantigene konnte eine Serokonversion um bis zu 3 Titerstufen bei den PCR-positiven Sauen gegenüber 2 verschiedenen H1avN1-Isolaten gemessen werden. Darüber hinaus ließen sich auch bei der Mehrzahl der restlichen untersuchten Altersgruppen hohe Antikörpertiter gegen diese beiden H1avN1-Teststämme nachweisen. Nach Anwendung des europaweit zugelassenen trivalenten Influenzaimpfstoffs konnte das klinische Erscheinungsbild in der Herde deutlich verbessert werden. Der Fallbericht verdeutlicht, dass für eine zielgerichtete Influenzadiagnostik der direkte und der indirekte Erregernachweis kombiniert verwendet werden sollten. Zudem wurde gezeigt, dass die kontinuierliche Anpassung von Testantigenen an die im Feld zirkulierenden Isolate überaus entscheidend für die Aussagekraft des HAH wäre.

Swine influenza A viruses (swIAVs) can play a crucial role in the generation of new human pandemic viruses. In this study, in-depth passive surveillance comprising nearly 2,500 European swine holdings and more than 18,000 individual samples identified a year-round presence of up to four major swIAV lineages on more than 50% of farms surveilled. Phylogenetic analyses show that intensive reassortment with human pandemic A(H1N1)/2009 (H1pdm) virus produced an expanding and novel repertoire of at least 31 distinct swIAV genotypes and 12 distinct hemagglutinin/neuraminidase combinations with largely unknown consequences for virulence and host tropism. Several viral isolates were resistant to the human antiviral MxA protein, a prerequisite for zoonotic transmission and stable introduction into human populations. A pronounced antigenic variation was noted in swIAV, and several H1pdm lineages antigenically distinct from current seasonal human H1pdm co-circulate in swine. Thus, European swine populations represent reservoirs for emerging IAV strains with zoonotic and, possibly, pre-pandemic potential.

The emergence of the human 2009 pandemic H1N1 (H1N1pdm) virus from swine populations refocused public and scientific attention on swine as an important source of influenza A viruses bearing zoonotic potential. Widespread and year-round circulation of at least four stable lineages of porcine influenza viruses between 2009 and 2012 in a region of Germany with a high-density swine population is documented here. European avian influenza virus-derived H1N1 (H1N1av) viruses dominated the epidemiology, followed by human-derived subtypes H1N2 and H3N2. H1N1pdm viruses and, in particular, recently emerging reassortants between H1N1pdm and porcine HxN2 viruses (H1pdmN2) were detected in about 8% of cases. Further reassortants between these main lineages were diagnosed sporadically. Ongoing diversification both at the phylogenetic and at the antigenic level was evident for the H1N1av lineage and for some of its reassortants. The H1avN2 reassortant R1931/11 displayed conspicuously distinct genetic and antigenic features and was easily transmitted from pig to pig in an experimental infection. Continuing diverging evolution was also observed in the H1pdmN2 lineage. These viruses carry seven genome segments of the H1N1pdm virus, including a hemagglutinin gene that encodes a markedly antigenically altered protein. The zoonotic potential of this lineage remains to be determined. The results highlight the relevance of surveillance and control of porcine influenza virus infections. This is important for the health status of swine herds. In addition, a more exhaustive tracing of the formation, transmission, and spread of new reassortant influenza A viruses with unknown zoonotic potential is urgently required.

Samples were collected from 203 wild boars (Sus scrofa) hunted in Baden-Wurtemburg, Germany from November-January 2008 and 2009. Samples from the lung and tonsil were analyzed by quantitative polymerase chain reaction (qPCR) for porcine reproductive and respiratory syndrome virus (PRRSV) type 1 (European type) and type 2 (American type). A qPCR to detect porcine circovirus type 2 (PCV2)-specific genome was performed on tissue homogenates including lung, tonsils, and inguinal lymph nodes. Serum samples were tested for antibodies against PRRSV and PCV2 by enzyme-linked immunosorbent assay (ELISA). No PRRSV was detected in any of the 203 samples and one sample had detectable antibodies against PRRSV. We detected PCV2 in organ materials from 103 wild boars with a prevalence of 50.7%. The number of wild boars positive for PCV2 by PCR varied according to the population density of wild boars among woodlands. More positive samples were detected in woodlands with a high density of wild boars. We found no correlation between the number of PCV2-positive wild boars and the density of domestic pigs in the surrounding area. The number of wild boars positive for antibodies against PCV2 by the INGEZIM Circovirus IgG/IgM test kit was low (53 sera positive for IgG- and three sera positive for IgM-antibodies) in comparison to the higher positive results from the INGEZIM CIRCO IgG test kit (102 positive and 12 inconclusive results).