Long-Term Surveillance of Aujeszky's Disease in the Alpine Wild Boar (Sus scrofa).

Although wild boar can act as a persistent Aujeszky's disease (AD) reservoir, limited data are available on long-term epidemiology in free-ranging wild boar living in areas where industrial swine herds are limited. Hence, this study provides crucial information, which fills this knowledge gap, on the natural dynamics of AD infection. From 3260 sera sampled during eight hunting seasons, 162 (4.97%) were tested positive. Factors, including the animal's age class, and the sampling year, had significant effects on the probability of the wild boar being seropositive, while wild boar mean abundance per area, yearly abundance and the total number of pig farms, as well as interactions among age, year and sex, were not significant. In particular, a positive trend of seroprevalence was observed over the years, with values ranging from 2.1 to 10.8%. This long-term surveillance showed an increase in seroprevalence with a higher probability of being seropositive in older individuals and the independence of wild boar seropositivity from the likelihood of contact with pigs in the area.

Genetic data from avian influenza and avian paramyxoviruses generated by the European network of excellence (EPIZONE) between 2006 and 2011--review and recommendations for surveillance.

Since 2006, the members of the molecular epidemiological working group of the European "EPIZONE" network of excellence have been generating sequence data on avian influenza and avian paramyxoviruses from both European and African sources in an attempt to more fully understand the circulation and impact of these viruses. This review presents a timely update on the epidemiological situation of these viruses based on sequence data generated during the lifetime of this project in addition to data produced by other groups during the same period. Based on this information and putting it all into a European context, recommendations for continued surveillance of these important viruses within Europe are presented.

Comparison of enzyme-linked immunosorbent assay and RT-PCR for the detection of porcine epidemic diarrhoea virus.

Porcine epidemic diarrhoea (PED) is a contagious enteric disease of pigs caused by a coronavirus. A double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) based on the use of monoclonal antibodies was developed for the detection of porcine epidemic diarrhoea virus (PEDV). The DAS-ELISA was compared with RT-PCR in the examination of 506 specimens collected during 2006-2007 from pigs originating from different farms located in the Po valley. Both faecal samples obtained directly from the rectum of live animals showing clinical signs and intestinal samples collected from the caecum of deceased pigs were included in the study. The correlation between the two methods was higher when testing faecal samples (K=0.97, 95% CI: 0.94-1.00) than testing intestinal samples (K=0.62, 95% CI: 0.35-0.89). The use of ELISA technology provided an efficient and effective mean of evaluating the presence of coronavirus PED antigen in field samples and indicates that this procedure is a very useful tool in epidemiological studies.

Characterization of a new genotype and serotype of infectious bronchitis virus in Western Africa.

Between 2002 and 2007, more than 1000 chickens from commercial farms, live bird markets and backyard farms in Nigeria and Niger were tested for the presence of the infectious bronchitis virus (IBV) genome. Phylogenetic analysis of full-length sequences of the spike 1 (S1) gene revealed a new genotype of IBV that we refer to as 'IBADAN'. The minimum genetic distance to the closest 'non-IBADAN' strains (UK/7/93 at the nucleotide level; H120 and M41 at the amino acid level) reached 24 and 32 % at the nucleotide and amino acid levels, respectively. The full genome of the IBADAN reference strain (NGA/A116E7/2006) had a genetic distance of 9.7-16.4 % at the nucleotide level with all available fully sequenced strains. As IBV S1 plays a major role in antigenicity, the antigenic relatedness of NGA/A116E7/2006 was compared with strains of other serotypes. NGA/A116E7/2006 did not cross-react with antisera against IT02, M41, D274, Connecticut or 793/B strains in virus neutralization assays. NGA/A116E7/2006 cross-reacted with the QX-like strain ITA/90254/2005 but only to a low level (antigenic relatedness of 33 %), suggesting that IBADAN also represents a new serotype. A comparison of S1 sequences identified several amino acids that may play a role in IBV antigenicity. Despite the absence of obvious clinical signs in poultry infected by IBADAN strains, it is important to test the cross-protection of current vaccine strains.

Molecular analysis of avian H7 influenza viruses circulating in Eurasia in 1999-2005: detection of multiple reassortant virus genotypes.

Avian influenza infections by high and low pathogenicity H7 influenza viruses have caused several outbreaks in European poultry in recent years, also resulting in human infections. Although in some cases the source of H7 strains from domestic poultry was shown to be the viruses circulating in the wild bird reservoir, a thorough characterization of the entire genome of H7 viruses from both wild and domestic Eurasian birds, and their evolutionary relationships, has not been conducted. In our study, we have analysed low pathogenicity H7 influenza strains isolated from wild and domestic ducks in Italy and southern China and compared them with those from reared terrestrial poultry such as chicken and turkey. Phylogenetic analysis demonstrated that the H7 haemagglutinin genes were all closely related to each other, whereas the remaining genes could be divided into two or more phylogenetic groups. Almost each year different H7 reassortant viruses were identified and in at least two different years more than one H7 genotype co-circulated. A recent precursor in wild waterfowl was identified for most of the gene segments of terrestrial poultry viruses. Our data suggest that reassortment allows avian influenza viruses, in their natural reservoir, to increase their genetic diversity. In turn this might help avian influenza viruses colonize a wider range of hosts, including domestic poultry.

Active surveillance for avian influenza viruses in wild birds and backyard flocks in Northern Italy during 2004 to 2006.

Following the avian influenza epidemics that occurred in Italy between 1997 and 2003, the Italian Ministry of Health in collaboration with veterinary authorities promoted, funded and implemented a national surveillance programme. The main objectives of the surveillance effort were to identify avian influenza viruses circulating in wild birds and to investigate the role of backyard poultry flocks in the dynamics of infection in a densely populated poultry area. Over 2 years (2004 to 2006), 164 backyard flocks and 4083 wild birds (mainly migratory Anseriformes and Charadriiformes) were sampled in three regions in the North of Italy. Samples collected were screened by means of real-time reverse transcriptase-polymerase chain reaction and the positive samples were processed for attempted virus isolation in embryonated fowl's specific pathogen free eggs. At the end of the study period, 27 low-pathogenic avian influenza viruses had been isolated from backyard flocks and 49 strains obtained from wild birds. Of these, 26 belonged to the H5 or H7 subtype and were closely related to contemporary low-pathogenic strains of Eurasian lineage. The findings confirm that backyard free-range farming is at high risk for avian influenza virus introduction, and confirm the role of wild waterfowl in the introduction and perpetuation of low-pathogenic avian influenza viruses during the winter season in Southern Europe.

Genetic and antigenic characterization of infectious bursal disease viruses isolated in Italy during the period 2002-2005.

During the period 2002-2005, 109 infectious bursal disease virus (IBDV) field strains were isolated from bird flocks located in various parts of Italy. Out of these strains, 91 were isolated from broilers, 12 from pullets, and six from backyard flocks. Forty-two IBDV strains were further investigated and characterized on the basis of the geographical origin, source, and clinical signs. Antigenic and genetic characterizations were carried out using a monoclonal antibody (MAb)-based antigen-capture (AC) enzyme-linked immunosorbent assay (ELISA) or a virus neutralization assay and a reverse transcription, amplification, and direct sequencing of a genome fragment encoding the VP2 variable domain. The viruses were compared with reference IBDV strains, F52/70 (classical, 1970), 89163 (typical very virulent [vv]IBDV, 1989), 91168 (antigenically modified vvIBDV, 1991) and 94432 (antigenically modified vvIBDV, 1994) among others. All 42 strains were genetically characterized, and the comparison of their nucleotide sequences revealed the presence of six clusters having 100% identity, named group 1, 2, 3, 4, 5, and 6. Twelve strains, representative of each molecular group and/or with interesting amino acid sequence, were also antigenically characterized. The antigenic characterization showed six strains--151573, 157185 (group 1), 192294 (group 2), 77882 (group 3), 217 (group 4), and 192304--with the profile typical of vvIBDV (lack of binding of MAbs 3 and 4). Two strains, 77165 and 204875 (group 6), were also related to vvIBDV but did not react with MAb 5. Three isolates exhibited a profile of cell culture-adapted viruses and classical strains but with some differences: strain 157776 reacted with all MAbs; strain 168026 with all MAbs except MAb 4, which weakly neutralized it; and strain 72293 with all MAbs except MAb 9, which is rather unusual. The last strain, 213622, showed a very uncommon antigenic profile with missing or reduced binding of MAbs 3, 4, 5, 6, 8, and 9. Genetic characterization revealed 37 strains identified as vvIBDV viruses divided in 26 isolates (including groups 1, 2, 3, and 4) with the four amino acids residues typical of vvIBDV (222A, 256I, 294I, 299S) and 11 isolates (including groups 5, 6, and 213622) with some other amino acid exchanges. Four isolates (72293, 168026, 196783, and 222220) presented an amino acid sequence closely related to attenuated classical viruses whereas the last isolate (157776) exhibited a rather different sequence with some mutations typical of vvIBDV and others for cell culture-adapted viruses. Results of the antigenic and genetic characterization revealed that the majority of viruses (n = 37) were related to vvIBDV strains but, among these, 11 strains presented antigenically and genetically modified characteristics and originated, in major part, from the area where viruses have been circulating for a long time. The remaining viruses (n = 5) were related but not identical to attenuated classical viruses and came from areas where vaccination with intermediate strains is applied.