EPIDEMIOLOGY, GENOMIC CHARACTERISATION AND EVOLUTIONARY ANALYSIS OF ITALIAN H1 SWINE INFLUENZA VIRUSES
Tesi di Dottorato
Data di Pubblicazione:
2013
Citazione:
EPIDEMIOLOGY, GENOMIC CHARACTERISATION AND EVOLUTIONARY ANALYSIS OF ITALIAN H1 SWINE INFLUENZA VIRUSES / A.m. Moreno Martin ; tutor: G. Grilli ; coordinatore: G. Sironi. UNIVERSITA' DEGLI STUDI DI MILANO, 2013 Feb 05. 25. ciclo, Anno Accademico 2012. [10.13130/moreno-martin-ana-maria_phd2013-02-05].
Abstract:
Abstract
Study n.1 - Swine influenza viruses: virological surveillance in Italy during 1998-2011
Three predominant subtypes of swine influenza viruses (SIVs) circulating in pigs throughout the world are H1N1, H3N2 and H1N2. In Europe over the last years, the epidemiology of SIVs has considerable changed. In particular in Italy, swine monitoring programs have been applied since the nineties and are based on genome detection, virus isolation and sequencing of all respiratory forms. This study reported the swine influenza surveillance programme preformed during the period 1998 – 2011. Investigated samples originated from the entire country but the major part of them was from North Italy where more than 75% of the swine industry is located. In this period 580 SIVs were isolated divided in 243 H1N1, 214 H3N2, 111 H1N2, 12 2009 A/ H1N1 pandemic (H1N1pdm) and 1 H3N1. These results revealed continuous circulation of H1N1, H3N2 and H1N2 viruses and isolation of the H1N1 pdm viruses in pigs starting in 2009. The most frequent subtype was the avian-like H1N1 and the second the H3N2. The H1N2 subtype was rarely isolated in the first part of the investigated period but since 2005, its frequency increased becoming the second subtype in the last three years. In the last two years 12 H1N1pdm strains were isolated in 7 different farms also when these viruses did not circulate in the human population. Moreover it is worth noting the isolation of one H3N1 strain, which resulted from a reassortment between swine H1N1 and H3N2 influenza viruses. Phylogenetic analysis evidenced homogeneity among the recent Italian H1N1 SIVs, distinguishing these from the earlier strains. Also for the H1N2 subtype the presence of a homogeneous group, differing from the earlier strains is reported. Interestingly the neuraminidase (NA) gene of the recent Italian strains showed different characteristics respect to the European H1N2 strains, deriving from the recent human H3N2 viruses. Finally, Italian H3N2 viruses were gradually evolved from A/Port Chalmer/1/73 like human virus, which is considered the most probable ancestor of the swine PCh-73 lineage. These results evidenced reassortment events between swine and human influenza viruses and highlight the need for a stringent surveillance in the pig population with particular attention to the H1N2 subtype and the H1N1 pdm viruses.
Study n.2 - First pandemic H1N1 outbreak from a pig farm in Italy
The first outbreak of the 2009 A/H1N1 pandemic virus in a swine breeder farm in Italy in November 2009 was reported. Clinical signs observed in sows included fever, depression, anorexia and agalactia, while in piglets diarrhoea and weight loss. The morbidity in sows was approximately 30% and the accumulated mortality rate was similar with those usually reported in piggeries (<10%). Virus was isolated from piglets (A/Sw/It/290271/09) and the sequencing of the whole genome was then performed. Comparison with all pandemic H1N1 sequences available in GenBank shows in A/Sw/It/290271/09 three unique amino-acid (aa) changes in PB2 (S405T), PB1 (K386R) and PA (K256Q), not yet associated to any well characterized phenotype markers of Influenza viruses. All eight aa at positions representing the so-called species-specific swine-human signatures, found in both swine and in the pandemic H1N1v, are also present. The M2 protein displays the C55F and the PA protein the S409N substitutions, both corresponding to enhanced transmission phenotype markers. Phylogenetic analysis showed that the virus was genetically related to the pandemic H1N1 virus. In addition, serological samples were collected from 40 sows, of which 20 resulted positive to the pandemic H1N1 virus by HI test proving a virus circulation in the farm.
Study n.3 - Nove
Tipologia IRIS:
Tesi di dottorato
Keywords:
swine influenza viruses ; H1N2 subtype ; 2009 A/H1N1 pandemic viruses ; genomic characterization ; evolutionary analysis ; Italy
Elenco autori:
A.M. MORENO MARTIN
Link alla scheda completa:
Link al Full Text: