Pregnancy outcome and clinical status of gilts fol

Authors: Krzysztof Kwit Małgorzata PomorskaMól Iwona MarkowskaDaniel

Publish Date: 2015/07/11

Volume: 160, Issue: 10, Pages: 2415-2425

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Abstract

The present study was planned to study the effect of various subtypes of swine influenza virus SIV circulating among pigs H1N2 H3N2 and emerging pandemic strain of H1N1 influenza A virus H1N1pdm09 on the course of pregnancy in naïve gilts experimentally infected during the last month of pregnancy In addition the clinical course of infection distribution of viruses in various tissues blood placenta fetal lung and selected immunological reproductive and productive parameters were also investigated All SIVinoculated gilts became infected No abortions stillbirths intrauterine deaths or mummified fetuses were observed No clinical signs of influenza virus infection or other disorders were observed in piglets born from infected and control gilts There was a significant decrease in the number and frequency of lymphocytes in gilts inoculated with all influenza viruses In general the concentrations of IL6 IL10 and TNFα were significantly higher in SIVinoculated gilts as than in control animals while IL4 and IFNγ were not detected in plasma at any time postinoculation in SIV or mockinoculated gilts No evidence for transplacental transmission of SIV was found Viremia was also not observed in any of the infected females On the basis of recent results we hypothesize that pregnancy failure observed during SIV infection under field conditions is probably related to high fever and proinflammatory cytokines rather than a direct effect of the virus on the placenta embryo or fetusThere are several infectious agents that have the potential to cause reproductive failure in pigs 1 Infections of pregnant females with some of them often pass unnoticed however the pathogen may still pass the placenta and infect the embryo or/and fetus 1 In contrast other pathogens cause clear clinical signs that result directly or indirectly in abortions fetal deaths or other reproduction disorders 1 Among the second group of pathogens swine influenza virus SIV is often mentioned 2 3Swine influenza SI is characterized by high morbidity and low mortality The main clinical signs are fever coughing dyspnea inappetence and weight loss However abortion stillbirth fetal deaths and other reproductive disorders can be also associated with epidemics of SI 3 4 5 Abortions in influenza A virus IAVinfected humans as well as animals including pigs seem to be a result of high fever and a “cytokine storm” associated with acute infection but transplacental transmission of the virus has been also reported 5 6 7 8 9 10 Influenza virus has also been isolated from amnion and chorion tissues in guinea pigs 11 and amniotic fluid in ferrets 12 To date there is insufficient data to conclude that IAV has a specific and direct association with the occurrence of reproductive problemsSwine influenza virus has been isolated from farms where reproductive disorders have been reported but its effect on swine reproduction is not completely understood 10 13 In the study of Madec et al 5 only 23  of sows infected with SIV in their first week of pregnancy completed gestation and farrowed in 25  of sows that were one month into gestation total embryonic resorption occurred and in the 55  of sows that were more than 45 days into gestation an abortion occurred 5 Swine influenza virus was detected in an aborted fetus 5 The results obtained by Young and Underdahl 14 revealed that pigs born to sows that had been inoculated with SIV had higher mortality rates and lower weaning weights than those from control sows 14 Sporadic abortions late in pregnancy and increased stillbirths have also been reported during SI outbreaks 2 3 10 15 16To date the mechanisms responsible for the reproductive disorders during influenza virus infection have not been finally clarified Although influenza virus infections in humans are known to increase the risk of adverse pregnancy outcomes the effects of maternal influenza virus infection on the fetus are not well understood The influence of SIV infection in pigs on the course of pregnancy and on the fetus is also poorly understoodIn previous studies we have evaluated the effect of H1N2 SIV infection in gilts during the first and the second month of pregnancy 23 24 The results of these studies indicated that infection of pregnant gilts with swine H1N2 IAV in the earlier stages of pregnancy did not cause abortion or reproduction failure and no evidence for transplacental transmission of H1N2 SIV was noted However due to the diversity of IAV it cannot be excluded that other subtypes of IAV could be associated with reproduction failure in pigs Moreover the stage of pregnancy during SIV infection might be an important factor influencing the risk of reproduction disordersFor these reasons we have decided to evaluate the effect of infection with various subtypes of SIV circulating among pigs H1N2 H3N2 and the emerging pandemic strain of H1N1 SIV H1N1pdm09 on the course of pregnancy in naïve gilts experimentally infected during the last month of pregnancy In addition the clinical course of infection and selected immunological reproductive and productive parameters were also investigated

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