S C Essen

Agri-Food and Biosciences Institute, Béal Feirste, N Ireland, United Kingdom

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Publications (12)11.88 Total impact

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    The Veterinary record 07/2014; · 1.63 Impact Factor
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    ABSTRACT: In December 2010, infection with a H9N1 low pathogenicity avian influenza (LPAI) virus was detected in a broiler breeder flock in East Anglia. Disease suspicion was based on acute drops in egg production in two of four sheds on the premises, poor egg shell quality and evidence of diarrhoea. H9N1 LPAI virus infection was confirmed by real-time reverse transcription PCR. Sequencing revealed high nucleotide identity of 93.6 per cent and 97.9 per cent with contemporary North American H9 and Eurasian N1 genes, respectively. Attempted virus isolation in embryonated specific pathogen free (SPF) fowls' eggs was unsuccessful. Epidemiological investigations were conducted to identify the source of infection and any onward spread. These concluded that infection was restricted to the affected premises, and no contacts or movements of poultry, people or fomites could be attributed as the source of infection. However, the infection followed a period of extremely cold weather and snow which impacted on the biosecurity protocols on site, and also led to increased wild bird activity locally, including waterfowl and game birds around the farm buildings. Analysis of the N1 gene sequence suggested direct introduction from wild birds. Although H9 infection in poultry is not notifiable, H9N2 LPAI viruses have been associated with production and mortality episodes in poultry in many parts of Asia and the Middle East. In the present H9N1 outbreak, clinical signs were relatively mild in the poultry with no mortality, transient impact on egg production and no indication of zoonotic spread. However, this first reported detection of H9 LPAI virus in chickens in England was also the first H9 UK poultry case for 40 years, and vindicates the need for continued vigilance and surveillance of avian influenza viruses in poultry populations.
    The Veterinary record. 09/2012; 171(15):372.
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    ABSTRACT: Infection of pigs with influenza A H1N1 2009 virus (A(H1N1)pdm09) was first detected in England in November 2009 following global spread of the virus in the human population. This paper describes clinical and epidemiological findings in the first English pig farms in which A(H1N1)pdm09 influenza virus was detected. These farms showed differences in disease presentation, spread and duration of infection. The factors likely to influence these features are described and relate to whether pigs were housed or outdoors, the age of the pigs, inter-current disease and the management system of the unit. Infection could be mild or clinically inapparent in breeding pigs with more typical respiratory disease being identified later in their progeny. Mortality was low where disease was uncomplicated by environmental stresses or concurrent infections. Where deaths occurred in pigs infected with A(H1N1)pdm09 influenza, they were mainly due to other infections, including streptococcal disease due to Streptococcus suis infection. This paper demonstrates the ease with which A(H1N1)pdm09 virus was transmitted horizontally and maintained in a pig population.
    The Veterinary record. 08/2012; 171(11):271.
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    ABSTRACT: This study presents the results of the virological surveillance for swine influenza viruses (SIVs) in Belgium, UK, Italy, France and Spain from 2006 to 2008. Our major aims were to clarify the occurrence of the three SIV subtypes - H1N1, H3N2 and H1N2 - at regional levels, to identify novel reassortant viruses and to antigenically compare SIVs with human H1N1 and H3N2 influenza viruses. Lung tissue and/or nasal swabs from outbreaks of acute respiratory disease in pigs were investigated by virus isolation. The hemagglutinin (HA) and neuraminidase (NA) subtypes were determined using standard methods. Of the total 169 viruses, 81 were classified as 'avian-like' H1N1, 36 as human-like H3N2 and 47 as human-like H1N2. Only five novel reassortant viruses were identified: two H1N1 viruses had a human-like HA and three H1N2 viruses an avian-like HA. All three SIV subtypes were detected in Belgium, Italy and Spain, while only H1N1 and H1N2 viruses were found in UK and Northwestern France. Cross-hemagglutination inhibition (HI) tests with hyperimmune sera against selected older and recent human influenza viruses showed a strong antigenic relationship between human H1N1 and H3N2 viruses from the 1980s and H1N2 and H3N2 human-like SIVs, confirming their common origin. However, antisera against human viruses isolated during the last decade did not react with currently circulating H1 or H3 SIVs, suggesting that especially young people may be, to some degree, susceptible to SIV infections.
    Zoonoses and Public Health 03/2011; 58(2):93-101. · 2.09 Impact Factor
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    ABSTRACT: The initial incursion of pandemic (H1N1) 2009 influenza A virus (pH1N1) into a European pig population is reported. Diagnosis of swine influenza caused by pandemic virus was made during September 2009 following routine submission of samples for differential diagnosis of causative agents of respiratory disease, including influenza A virus. All four pigs (aged six weeks) submitted for investigation from a pig herd of approximately 5000 animals in Northern Ireland, experiencing acute-onset respiratory signs in finishing and growing pigs, were positive by immunofluorescence for influenza A. Follow-up analysis of lung tissue homogenates by real-time RT-PCR confirmed the presence of pH1N1. The virus was subsequently detected on two other premises in Northern Ireland; on one premises, detection followed the pre-export health certification testing of samples from pigs presumed to be subclinically infected as no clinical signs were apparent. None of the premises was linked to another epidemiologically. Sequencing of the haemagglutinin and neuraminidase genes revealed high nucleotide identity (>99.4 per cent) with other pH1N1s isolated from human beings. Genotypic analyses revealed all gene segments to be most closely related to those of contemporary pH1N1 viruses in human beings. It is concluded that all three outbreaks occurred independently, potentially as a result of transmission of the virus from human beings to pigs.
    The Veterinary record. 05/2010; 166(21):642-5.
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    ABSTRACT: The declaration of the human influenza A pandemic (H1N1) 2009 (H1N1/09) raised important questions, including origin and host range [1], [2]. Two of the three pandemics in the last century resulted in the spread of virus to pigs (H1N1, 1918; H3N2, 1968) with subsequent independent establishment and evolution within swine worldwide [3]. A key public and veterinary health consideration in the context of the evolving pandemic is whether the H1N1/09 virus could become established in pig populations [4]. We performed an infection and transmission study in pigs with A/California/07/09. In combination, clinical, pathological, modified influenza A matrix gene real time RT-PCR and viral genomic analyses have shown that infection results in the induction of clinical signs, viral pathogenesis restricted to the respiratory tract, infection dynamics consistent with endemic strains of influenza A in pigs, virus transmissibility between pigs and virus-host adaptation events. Our results demonstrate that extant H1N1/09 is fully capable of becoming established in global pig populations. We also show the roles of viral receptor specificity in both transmission and tissue tropism. Remarkably, following direct inoculation of pigs with virus quasispecies differing by amino acid substitutions in the haemagglutinin receptor-binding site, only virus with aspartic acid at position 225 (225D) was detected in nasal secretions of contact infected pigs. In contrast, in lower respiratory tract samples from directly inoculated pigs, with clearly demonstrable pulmonary pathology, there was apparent selection of a virus variant with glycine (225G). These findings provide potential clues to the existence and biological significance of viral receptor-binding variants with 225D and 225G during the 1918 pandemic [5].
    PLoS ONE 02/2010; 5(2):e9068. · 3.53 Impact Factor
  • Avian Diseases Digest 01/2009;
  • The Veterinary record 04/2008; 162(9):278-80. · 1.63 Impact Factor
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    ABSTRACT: Real time reverse transcriptase (RRT)-polymerase chain reaction (PCR) for the detection of Eurasian H5 avian influenza virus (AIV) isolates was adapted from an existing protocol, optimized, and validated using a number of genetically diverse H5 isolates (n = 51). These included 34 "Asian lineage" H5N1 highly pathogenic avian influenza (HPAI) viruses (2004-2006), plus 12 other H5 isolates from poultry outbreaks and wild birds in the Eastern Hemisphere (1996-2005). All 51 were positive by H5 Eurasian RRT-PCR. Specificity was assessed by testing representative isolates from all other AL virus subtypes (n = 52), non-AI avian pathogens (n = 8), plus a negative population of clinical specimens derived from AI-uninfected wild birds and poultry (n = 604); all were negative by H5 Eurasian RRT-PCR. RNA was directly extracted from suspect HPAI H5N1 clinical specimens (Africa, Asia, and Europe; 2005-2006; n = 58) from dead poultry and wild birds, and 55 recorded as positive by H5 Eurasian RRT-PCR: Fifty-one of these 55 were in agreement with positive AIV isolation in embryonated chickens' eggs. H5 Eurasian RRT-PCR was invaluable in H5 outbreak diagnosis and management by virtue of its rapidity and high degree of sensitivity and specificity. This method provides a platform for automation that can be applied for large-scale intensive investigations, including surveillance.
    Avian Diseases 04/2007; 51(1 Suppl):373-7. · 1.11 Impact Factor
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    ABSTRACT: 10.1637/7664-060906R1.1
    Avian Dis. 01/2007; 51:373-377.
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    ABSTRACT: There have been at least ten distinct outbreaks of LPAI or HPAI in poultry caused by H5 or H7 viruses in the last eight years in Europe and the Middle East. There appears to be an increased occurrence of such episodes consistent with global trends. As a result, surveillance systems have been enhanced to facilitate early detection of infection in poultry, together with active surveillance of wild bird populations. These complementary activities have resulted in the detection of a number of viruses in wild bird populations, including some with high genetic similarity to newly detected viruses in poultry, for example, H7N3 in Italy and H7N7 in the Netherlands. Furthermore, there is evidence for continued circulation of H5 and H7 viruses in wild Anseriformes, thereby presenting a real and current threat for the introduction of viruses to domestic poultry, especially those reared in outdoor production systems. Viruses of H9N2 subtype continue to circulate widely in the Middle East and are associated with significant disease problems in poultry. The epidemiology has the potential to be complicated further by introduction of novel viruses through illegal importation of captive birds, such as was detected with H5N1 in Belgium in 2004. Continual genetic exchange in the avian virus gene pool and independent evolution of all gene segments either within an individual host species or among wild bird hosts suggests that these viruses are not in evolutionary stasis in the natural reservoir.
    Developments in biologicals 02/2006; 124:45-50.
  • L P Phipps, S C Essen, I H Brown
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    ABSTRACT: Influenza A viruses are subtyped conventionally according to the antigenic characteristics of the external glycoproteins, haemagglutinin (HA) and neuraminidase (NA). To date 15 HA and 9 NA subtypes have been described. There is a need to develop fast, accurate and reliable methods to identify influenza virus subtypes, which may be associated with disease outbreaks. An RT-PCR is described using a single primer pair based on a conserved region of the HA2 gene that can detect all 15 HA influenza A subtypes. The assay was validated initially using a panel of 12 known standard prototype strains of influenza virus representing 6 HA subtypes and subsequently in a blind study using a panel of 30 strains. Selected viruses represented all known HA subtypes derived from avian, swine and human hosts separated both geographically and with time Sequence analysis of RT-PCR product showed complete correlation with results obtained using conventional serological methods. It is concluded that this RT-PCR is a reliable, robust and reproducible tool for the rapid identification of a wide range of all the HA subtypes of influenza A viruses.
    Journal of Virological Methods 01/2005; 122(1):119-22. · 1.88 Impact Factor