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The article emphasizes the unique pathogenicity of porcine Parvovirus (PPV) causing disease and death both of embryos and fetuses during symptom-fewer infections in pregnant sows as well as other pigs from birth until slaughter. It describes the structure, genetic and antigenic properties of PPV as well as mentioning the NS1 non-structural protein and VP1, VP2 and VP3 structural capsid proteins. The article underlines the importance of VP2 as a hemagglutinin and immunogenic antigen and indicates that PPV is amongst the most resistant existing viruses to environmental factors, heat and disinfectants. It presents the consequences of infections of embryos and fetuses during different intervals of gestation. The ubiquitous and endemic occurrence of PPV is also mentioned as being a horizontal transmission from infected to naive pigs. Infections may also occur in pigs ingesting or inhaling virus-loaded secretions. Vaccines are the major way to ensure prevention of losses due to reproductive failures in swine. Inactivated and live vaccines with attenuated PPV are available. Immunization procedures of gilts, sows and boars are indicated and the article confirms that suspicion of PPV infection is based on irregular estrus, excretion of dead and mummified fetuses and small litters. The hemagglutination-inhibition test, seroneutralization, ELISA, immunofluorescence, and PCR are used for laboratory diagnosis. Since PPV infection is frequent and can not be eradicated losses are considerable.
During the last decade a variety of previously unknown porcine parvoviruses (PPV) were identified. New species were classified as PPV2, PPV3, PPV4, bocaviruses or hokoviruses. Preliminary investigations indicate that some of the newly emerging parvoviruses are relatively widespread in the Polish pig population. These findings suggest that the evolution and diversity of parvoviruses is much more complex than previously assumed. Current scientific efforts focus on issues such as the prevalence, pathogenic potential, genetic and antigenic variability, as well as the further evolution of parvoviruses. The aim of the present study was to summarize current knowledge regarding the newly described parvovirus species. First atypical strains of parvoviruses were detected in Asia and classified as PPV2. Latest studies have showed that PPV2 is present in swine in Hungary. In 2008, Lau et al. described animal parvoviruses similar to the human parvovirus PARV4. After the place of their first isolation (Hong Kong), the names “porcine hokovirus” (PHoV) and “bovine hokovirus” (BHoV) were proposed. In 2010, Cheung et al. suggested including PHoV in the Parvovirus genus and changing its name to “PPV3,” but this classification is still unofficial. The presence of PPV3 genotype was confirmed in pigs in Hungary, Great Britain, and Romania, as well as in the population of wild boars in Germany. Another species, PPV4, was found in 2005 in North Carolina (USA). PPV4 has also been detected in China, in both healthy and diseased pigs. In Hungary, PPV4 infection has been confirmed in 13 out of 57 herds analyzed, which suggests a large prevalence of this virus in the swine population. The presence of bocaviruses has been detected in pigs in Sweden, China, and Hungary, as well as in wild boars in Romania. Preliminary results suggest that in the swine population in Poland, not only classical PPV1, but also PPV2, PPV3, and PPV4 are present.
Problems in the reproduction of pigs may be the result of interaction of various factors, both infectious and non-infectious. Among the infectious agents, the greatest economic losses are caused by viral infection of pregnant gilts and sows. In the present study the most important pathogens causing reproductive disorders in pigs, including parvovirus (PPV), porcine reproductive and respiratory syndrome (PRRSV), swine influenza virus (SIV), porcine circovirus type 2 (PCV2), enteroviruses, encephalitis virus (EMCV), Aujeszky’s disease virus (ADV), classical swine fever virus (CSFV), Leptospira spp., Brucella suis and Erysipelotrix rhusiopathiae are characterized. So far, three possible ways of natural infection of the embryo or fetus are identified: via placenta, through the cervical canal, and by infection of the egg cell. The consequences of infection of pregnant females depend on the species of the virus, the gestation period, wherein there is an infection and immune status of pregnant females. The most common changes included: embryo death, resorption of embryos, mummification of fetuses, malformations, abortions, birth of dead or very weak piglets. Because of the importance of the reproduction sector for the competitive production of pigs, the monitoring of the health status of breeding stock, including compliance with all biosecurity rules and vaccination schedules, should be strictly respected by veterinarians taking care of pig breeding herds.
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