Swine influenza is a respiratory disease that affects 50% of the swine population in France. It is generally benign but serious or recurrent outbreaks on swine farms can occur, leading to health alerts and significant economic losses. Swine influenza viruses have the potential for transmission to humans. The 2009 outbreak of the human swine flu pandemic following the reassortment of several swine viruses, highlighted the need to monitor and study flu viruses in pigs. The Agency’s activities in this area involve four levels of action and expertise: reference work, epidemiological surveillance, research and expert assessment. The details follow.
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Updated on 25/08/2016
Agency activities concerning swine influenza
Studies on porcine influenza viruses, included those derived from the 2009 pandemic virus A(H1N1)
The activities of the Agency can be divided into four areas of action and expertise: reference activities, epidemiological surveillance, research and expert appraisals.
With its proven experience in surveillance and its knowledge of swine influenza, the Agency’s Ploufragan-Plouzané Laboratory was designated by the Directorate General for Food as National Reference Laboratory (NRL) for swine influenza viruses in September 2009. The Swine virology-immunology unit develops, validates and controls virological and serological diagnostic tools for the detection and identification of influenza A viruses in swine, including the A(H1N1)pdm09 virus. Genomic amplification methods for first-line detection have been transferred to a network of 12 accredited veterinary laboratories which participate in bi-annual inter-laboratory tests organised by the NRL. The NRL also supplies reference materials including hyperimmune sera, antigens, and standard controls, and offers general and technical training sessions.
Epidemiological surveillance activities
Swine influenza is not a regulated disease and there are few structured, permanent surveillance systems. As a result, knowledge of circulating viruses varies from country to country and data are often scarce or incomplete. In Europe, research teams including ANSES have set up a network called the European Surveillance Network for Influenza in Pigs (ESNIP) with the aim of harmonising surveillance and diagnostic methods, and sharing information on the viruses identified in the various countries. Three programmes supported by the European Commission have been carried out since 2001. Since2005, the units responsible for swine virology-immunology, epidemiology and swine welfare at the Ploufragan-Plouzané Laboratory have carried out surveillance programmes, mainly on swine farms in western France, as part of their research activities. From 2011, surveillance was reinforced and extended to the whole country with the implementation of the National surveillance system at the request of the Directorate General for Food, in partnership with stakeholders from the pig farming industry and the network of accredited laboratories. The NRL is responsible for identifying the detected viruses. ANSES is also charged with comparing virology test results with data collected on swine farms, through statistical analyses, in order to study the various epidemiological profiles related to infection. The Ploufragan-Plouzané Laboratory also participates in the monitoring group in charge of evaluating the relevance and effectiveness of the National surveillance system, within the National animal health epidemiological surveillance platform (PNSESA). Finally, ANSES develops specific surveillance programmes in overseas territories and for wildlife (wild boars).
The research activities of the Agency concerning swine influenza focus on three areas:
Monitoring of genetic and antigenic variation of swine influenza virus strains
The viruses identified through epidemiosurveillance undergo extensive studies on both their genetic and antigenic features, in order to develop knowledge on the evolution of SIVs in France and on the emergence of new reassortant viruses. Strains isolated in France are compared to those identified elsewhere in Europe, specifically via antigenic mapping and thorough phylogenetic analyses, based on whole-genome sequencing of viruses. Acquiring knowledge on viral evolution helps to substantiate expert appraisals and to inform the authorities of any new emerging risk both to animal health and to human health.
Studying swine influenza viral infection patterns on swine farms and the role of these viruses in the development of complex respiratory syndromes
Influenza viral infection in pigs usually results in minor clinical signs or appears to concern only some of the animals in a single pen. However, infection can also be more severe and almost generalised, depending on the virulence of the implicated strain. Concomitant infections with other pathogens that target the respiratory system may cause complications, but other adverse factors that are as yet poorly characterised may also influence the severity of the disease.
ANSES’s research in this area therefore aims to study infection patterns with viral strains on swine farms, and the factors associated with the various epidemiological forms of the disease, particularly those that favour the development of “recurrent” forms. Epidemiological surveillance systems show an increasing number of reported cases of recurrent swine influenza, and this form of the disease may favour viral reassortment.
Epidemiological surveys carried out on farms have shown that the swine influenza virus (SIV) is strongly associated with the development of pneumonia, during co-infection with Mycoplasma hyopneumoniae (Mhp). Experimental studies on specific pathogen-free (SPF) pigs are performed to assess the mechanisms underlying synergy between the two pathogens. The objectives are to compare the pathogenetic profiles of various viral strains, alone or in combination with Mhp, oxidative stress, inflammatory response, and early induced immune responses in infected animals.
In a context of reduced use of veterinary medicinal products, preserving the health and welfare of animals, and thereby their performance, requires alternative solutions particularly involving feed and nutrition. Another research area is therefore the study of the impact of nutritional status and diet on the ability of the animals to fight SIV/Mhp co-infection.
Studying the host specificity determinants and potential transmission of swine viruses to other species
Further to emergence of the A(H1N1)pdm09 virus, the Agency participated in experimental studies on the transmission of the human virus to swine, and carried out a comparison of the phenotypes and genotypes of the A(H1N1)pdm09 virus isolated from various animal species, including the pig. Through these comparisons, the Agency aims to identify potential molecular determinants of host specificity, and even virulence, in order to obtain new data on evolution of the virus after it crosses the species barrier. Studies are also being conducted on the context and mechanisms underlying genomic segment reassortment, a process that appears to be more common in recurrent forms of influenza. The results of studies on SIVs are compared to those on influenza A viruses isolated from other species, specifically humans.
Expert appraisal activities
An Emergency collective expert assessment group (GECU) on swine influenza was established at the end of April 2009 to examine available information on the viral strain causing the epidemic known as "H1N1 swine flu", specifically its origin, and the possibility of an epidemic in animals, particularly pigs and domestic birds. During autumn 2009, the Agency was requested to provide several opinions on the subject. It assessed inter-species contamination risk levels and released recommendations on the implementation of biosafety and prevention measures. To enable closer monitoring of viral evolution, the Agency recommended the creation of a national epidemiological surveillance network on swine influenza. This network was established at the beginning of 2011.
At the international level, ANSES responds to requests from the Food and Agriculture Organisation of the United Nations (FAO). Contributions include providing documentation on biological specimen sampling techniques for diagnosis of influenza in pigs, assisting in the drafting of a summary document on the available methods for the diagnosis of infections caused by influenza A and influenza A(H1N1)pdm09 in pigs, and providing technical training to laboratory personnel in southern Asia. The Agency also responds to requests from theWorld Organisation for Animal Health (OIE), revising the diagnostic manual, among other contributions. Scientists from ANSES also participate in the joint OIE/FAO Network of expertise on animal influenza (OFFLU) and the Ploufragan-Plouzané Laboratory is referenced at the international level as competent in the field of diagnostic analyses of samples from pigs.