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Chung DH, Torchetti MK, Killian ML, Swayne DE, Lee DH. Transmission Dynamics of Low Pathogenicity Avian Influenza (H2N2) Viruses in Live Bird Markets of the Northeast United States of America, 2013-2019. Virus Evol 2022; 8:veac009. [PMID: 35494174 PMCID: PMC9048936 DOI: 10.1093/ve/veac009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 12/29/2021] [Accepted: 02/09/2022] [Indexed: 11/21/2022] Open
Abstract
Live bird market (LBM) surveillance was conducted in the Northeast United States (US) to monitor for the presence of avian influenza viruses (AIV) in domestic poultry and market environments. A total of 384 H2N2 low pathogenicity AIV (LPAIV) isolated from active surveillance efforts in the LBM system of New York, Connecticut, Rhode Island, New Jersey, Pennsylvania, and Maryland during 2013–2019 were included in this analysis. Comparative phylogenetic analysis showed that a wild-bird-origin H2N2 virus may have been introduced into the LBMs in Pennsylvania and independently evolved since March 2012 followed by spread to LBMs in New York City during late 2012–early 2013. LBMs in New York state played a key role in the maintenance and dissemination of the virus to LBMs in the Northeast US including reverse spread to Pennsylvania LBMs. The frequent detections in the domestic ducks and market environment with viral transmissions between birds and environment possibly led to viral adaptation and circulation in domestic gallinaceous poultry in LBMs, suggesting significant roles of domestic ducks and contaminated LBM environment as reservoirs in maintenance and dissemination of H2N2 LPAIV.
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Affiliation(s)
- David H Chung
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut, USA
| | - Mia K Torchetti
- National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, Iowa, USA
| | - Mary L Killian
- National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, Iowa, USA
| | - David E Swayne
- Southeast Poultry Research Laboratory, US National Poultry Research Center, Agricultural Research Service, US Department of Agriculture, Athens, Georgia, USA
| | - Dong-Hun Lee
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut, USA
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Bergervoet SA, Heutink R, Bouwstra R, Fouchier RAM, Beerens N. Genetic analysis identifies potential transmission of low pathogenic avian influenza viruses between poultry farms. Transbound Emerg Dis 2019; 66:1653-1664. [PMID: 30964232 PMCID: PMC6850361 DOI: 10.1111/tbed.13199] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/25/2019] [Accepted: 04/02/2019] [Indexed: 12/25/2022]
Abstract
Poultry can become infected with low pathogenic avian influenza (LPAI) viruses via (in)direct contact with infected wild birds or by transmission of the virus between farms. This study combines routinely collected surveillance data with genetic analysis to assess the contribution of between‐farm transmission to the overall incidence of LPAI virus infections in poultry. Over a 10‐year surveillance period, we identified 35 potential cases of between‐farm transmission in the Netherlands, of which 10 formed geographical clusters. A total of 21 LPAI viruses were isolated from nine potential between‐farm transmission cases, which were further studied by genetic and epidemiological analysis. Whole genome sequence analysis identified close genetic links between infected farms in seven cases. The presence of identical deletions in the neuraminidase stalk region and minority variants provided additional indications of between‐farm transmission. Spatiotemporal analysis demonstrated that genetically closely related viruses were detected within a median time interval of 8 days, and the median distance between the infected farms was significantly shorter compared to farms infected with genetically distinct viruses (6.3 versus 69.0 km; p < 0.05). The results further suggest that between‐farm transmission was not restricted to holdings of the same poultry type and not related to the housing system. Although separate introductions from the wild bird reservoir cannot be excluded, our study indicates that between‐farm transmission occurred in seven of nine virologically analysed cases. Based on these findings, it is likely that between‐farm transmission contributes considerably to the incidence of LPAI virus infections in poultry.
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Affiliation(s)
- Saskia A Bergervoet
- Department of Virology, Wageningen Bioveterinary Research, Lelystad, The Netherlands.,Department of Viroscience, Erasmus MC, Rotterdam, The Netherlandss
| | - Rene Heutink
- Department of Virology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
| | | | - Ron A M Fouchier
- Department of Viroscience, Erasmus MC, Rotterdam, The Netherlandss
| | - Nancy Beerens
- Department of Virology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
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3
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Assessing the probability of introduction and spread of avian influenza (AI) virus in commercial Australian poultry operations using an expert opinion elicitation. PLoS One 2018; 13:e0193730. [PMID: 29494696 PMCID: PMC5832321 DOI: 10.1371/journal.pone.0193730] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 02/16/2018] [Indexed: 11/26/2022] Open
Abstract
The objective of this study was to elicit experts’ opinions and gather estimates on the perceived probability of introduction and spread of avian influenza (AI) virus in the Australian broiler and layer industry. Using a modified Delphi method and a 4-step elicitation process, 11 experts were asked to give initial individual estimates for the various pathways and practices in the presented scenarios using a questionnaire. Following this, a workshop was conducted to present group averages of estimates and discussion was facilitated to obtain final individual estimates. For each question, estimates for all experts were combined using a discrete distribution, with weights allocated representing the level of expertise. Indirect contact with wild birds either via a contaminated water source or fomites was considered the most likely pathway of introduction of low pathogenic avian influenza (LPAI) on poultry farms. Presence of a water body near the poultry farm was considered a potential pathway for introduction only when the operation type was free range and the water body was within 500m distance from the shed. The probability that LPAI will mutate to highly pathogenic avian influenza (HPAI) was considered to be higher in layer farms. Shared personnel, equipment and aerosol dispersion were the most likely pathways of shed to shed spread of the virus. For LPAI and HPAI spread from farm to farm, shared pick-up trucks for broiler and shared egg trays and egg pallets for layer farms were considered the most likely pathways. Findings from this study provide an insight on most influential practices on the introduction and spread of AI virus among commercial poultry farms in Australia, as elicited from opinions of experts. These findings will be used to support parameterization of a modelling study assessing the risk of AI introduction and spread among commercial poultry farms in Australia.
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Walz E, Linskens E, Umber J, Culhane MR, Halvorson D, Contadini F, Cardona C. Garbage Management: An Important Risk Factor for HPAI-Virus Infection in Commercial Poultry Flocks. Front Vet Sci 2018; 5:5. [PMID: 29435454 PMCID: PMC5790769 DOI: 10.3389/fvets.2018.00005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 01/10/2018] [Indexed: 11/17/2022] Open
Abstract
Garbage management represents a potential pathway of HPAI-virus infection for commercial poultry operations as multiple poultry premises may share a common trash collection service provider, trash collection site (e.g., shared dumpster for multiple premises) or disposal site (e.g., landfill). The types of potentially infectious or contaminated material disposed of in the garbage has not been previously described but is suspected to vary by poultry industry sector. A survey of representatives from the broiler, turkey, and layer sectors in the United States revealed that many potentially contaminated or infectious items are routinely disposed of in the trash on commercial poultry premises. On-farm garbage management practices, along with trash hauling and disposal practices are thus key components that must be considered to evaluate the risk of commercial poultry becoming infected with HPAI virus.
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Affiliation(s)
- Emily Walz
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
| | - Eric Linskens
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
| | - Jamie Umber
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
| | - Marie Rene Culhane
- Department of Veterinary Population Medicine, University of Minnesota, St. Paul, MN, United States
| | - David Halvorson
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
| | - Francesca Contadini
- Center for Animal Health and Food Safety, University of Minnesota, St. Paul, MN, United States
| | - Carol Cardona
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
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Preskenis LA, Ladman BS, Gelb J. Identification of Type A Influenza Viruses from Wild Birds on the Delmarva Peninsula, 2007–10. Avian Dis 2017; 61:83-89. [DOI: 10.1637/11461-062716-reg] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Lauren A. Preskenis
- Department of Animal and Food Sciences, Avian Biosciences Center, University of Delaware, Newark, DE 19716
| | - Brian S. Ladman
- Department of Animal and Food Sciences, Avian Biosciences Center, University of Delaware, Newark, DE 19716
| | - Jack Gelb
- Department of Animal and Food Sciences, Avian Biosciences Center, University of Delaware, Newark, DE 19716
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Long-term surveillance of H7 influenza viruses in American wild aquatic birds: are the H7N3 influenza viruses in wild birds the precursors of highly pathogenic strains in domestic poultry? Emerg Microbes Infect 2015; 4:e35. [PMID: 26954883 PMCID: PMC4773044 DOI: 10.1038/emi.2015.35] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 05/11/2015] [Accepted: 05/13/2015] [Indexed: 11/08/2022]
Abstract
The emergence of influenza A virus (IAV) in domestic avian species and associated transmissions to mammals is unpredictable. In the Americas, the H7 IAVs are of particular concern, and there have been four separate outbreaks of highly pathogenic (HP) H7N3 in domestic poultry in North and South America between 2002 and 2012, with occasional spillover into humans. Here, we use long-term IAV surveillance in North American shorebirds at Delaware Bay, USA, from 1985 to 2012 and in ducks in Alberta, Canada, from 1976 to 2012 to determine which hemagglutinin (HA)-neuraminidase (NA) combinations predominated in Anseriformes (ducks) and Charadriiformes (shorebirds) and whether there is concordance between peaks of H7 prevalence and transmission in wild aquatic birds and the emergence of H7 IAVs in poultry and humans. Whole-genome sequencing supported phylogenetic and genomic constellation analyses to determine whether HP IAVs emerge in the context of specific internal gene segment sequences. Phylogenetic analysis of whole-genome sequences of the H7N3 influenza viruses from wild birds and HP H7N3 outbreaks in the Americas indicate that each HP outbreak was an independent emergence event and that the low pathogenic (LP) avian influenza precursors were most likely from dabbling ducks. The different polybasic cleavage sites in the four HP outbreaks support independent origins. At the 95% nucleotide percent identity-level phylogenetic analysis showed that the wild duck HA, PB1, and M sequences clustered with the poultry and human outbreak sequences. The genomic constellation analysis strongly suggests that gene segments/virus flow from wild birds to domestic poultry.
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Abdelwhab EM, Veits J, Mettenleiter TC. Prevalence and control of H7 avian influenza viruses in birds and humans. Epidemiol Infect 2014; 142:896-920. [PMID: 24423384 PMCID: PMC9151109 DOI: 10.1017/s0950268813003324] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/21/2013] [Accepted: 12/04/2013] [Indexed: 01/20/2023] Open
Abstract
The H7 subtype HA gene has been found in combination with all nine NA subtype genes. Most exhibit low pathogenicity and only rarely high pathogenicity in poultry (and humans). During the past few years infections of poultry and humans with H7 subtypes have increased markedly. This review summarizes the emergence of avian influenza virus H7 subtypes in birds and humans, and the possibilities of its control in poultry. All H7Nx combinations were reported from wild birds, the natural reservoir of the virus. Geographically, the most prevalent subtype is H7N7, which is endemic in wild birds in Europe and was frequently reported in domestic poultry, whereas subtype H7N3 is mostly isolated from the Americas. In humans, mild to fatal infections were caused by subtypes H7N2, H7N3, H7N7 and H7N9. While infections of humans have been associated mostly with exposure to domestic poultry, infections of poultry have been linked to wild birds or live-bird markets. Generally, depopulation of infected poultry was the main control tool; however, inactivated vaccines were also used. In contrast to recent cases caused by subtype H7N9, human infections were usually self-limiting and rarely required antiviral medication. Close genetic and antigenic relatedness of H7 viruses of different origins may be helpful in development of universal vaccines and diagnostics for both animals and humans. Due to the wide spread of H7 viruses and their zoonotic importance more research is required to better understand the epidemiology, pathobiology and virulence determinants of these viruses and to develop improved control tools.
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Affiliation(s)
- E M Abdelwhab
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Molecular Biology, Greifswald - Insel Riems, Germany
| | - J Veits
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Molecular Biology, Greifswald - Insel Riems, Germany
| | - T C Mettenleiter
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Molecular Biology, Greifswald - Insel Riems, Germany
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Slota KE, Hill AE, Keefe TJ, Bowen RA, Pabilonia KL. Biosecurity and bird movement practices in upland game bird facilities in the United States. Avian Dis 2011; 55:180-6. [PMID: 21793431 DOI: 10.1637/9509-082310-reg.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Since 1996, the emergence of Asian-origin highly pathogenic avian influenza subtype H5N1 has spurred great concern for the global poultry industry. In the United States, there is concern over the potential of a foreign avian disease incursion into the country. Noncommercial poultry operations, such as upland game bird facilities in the United States, may serve as a potential source of avian disease introduction to other bird populations including the commercial poultry industry, backyard flocks, or wildlife. In order to evaluate how to prevent disease transmission from these facilities to other populations, we examined biosecurity practices and bird movement within the upland game bird industry in the United States. Persons that held a current permit to keep, breed, or release upland game birds were surveyed for information on biosecurity practices, flock and release environments, and bird movement parameters. Biosecurity practices vary greatly among permit holders. Many facilities allow for interaction between wild birds and pen-reared birds, and there is regular long-distance movement of live adult birds among facilities. Results suggest that upland game bird facilities should be targeted for biosecurity education and disease surveillance efforts.
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Affiliation(s)
- Katharine E Slota
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 300 W. Drake Road, Fort Collins, CO 80523, USA.
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Li J, zu Dohna H, Cardona CJ, Miller J, Carpenter TE. Emergence and genetic variation of neuraminidase stalk deletions in avian influenza viruses. PLoS One 2011; 6:e14722. [PMID: 21373190 PMCID: PMC3044137 DOI: 10.1371/journal.pone.0014722] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 01/24/2011] [Indexed: 11/18/2022] Open
Abstract
When avian influenza viruses (AIVs) are transmitted from their reservoir hosts (wild waterfowl and shorebirds) to domestic bird species, they undergo genetic changes that have been linked to higher virulence and broader host range. Common genetic AIV modifications in viral proteins of poultry isolates are deletions in the stalk region of the neuraminidase (NA) and additions of glycosylation sites on the hemagglutinin (HA). Even though these NA deletion mutations occur in several AIV subtypes, they have not been analyzed comprehensively. In this study, 4,920 NA nucleotide sequences, 5,596 HA nucleotide and 4,702 HA amino acid sequences were analyzed to elucidate the widespread emergence of NA stalk deletions in gallinaceous hosts, the genetic polymorphism of the deletion patterns and association between the stalk deletions in NA and amino acid variants in HA. Forty-seven different NA stalk deletion patterns were identified in six NA subtypes, N1–N3 and N5–N7. An analysis that controlled for phylogenetic dependence due to shared ancestry showed that NA stalk deletions are statistically correlated with gallinaceous hosts and certain amino acid features on the HA protein. Those HA features included five glycosylation sites, one insertion and one deletion. The correlations between NA stalk deletions and HA features are HA-NA-subtype-specific. Our results demonstrate that stalk deletions in the NA proteins of AIV are relatively common. Understanding the NA stalk deletion and related HA features may be important for vaccine and drug development and could be useful in establishing effective early detection and warning systems for the poultry industry.
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Affiliation(s)
- Jinling Li
- Center for Animal Disease Modeling and Surveillance, University of California Davis, Davis, California, United States of America
| | - Heinrich zu Dohna
- Center for Animal Disease Modeling and Surveillance, University of California Davis, Davis, California, United States of America
| | - Carol J. Cardona
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Joy Miller
- National Center for Medical Intelligence, Fort Detrick, Maryland, United States of America
| | - Tim E. Carpenter
- Center for Animal Disease Modeling and Surveillance, University of California Davis, Davis, California, United States of America
- * E-mail:
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Leibler JH, Carone M, Silbergeld EK. Contribution of company affiliation and social contacts to risk estimates of between-farm transmission of avian influenza. PLoS One 2010; 5:e9888. [PMID: 20360859 PMCID: PMC2845626 DOI: 10.1371/journal.pone.0009888] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Accepted: 01/18/2010] [Indexed: 11/18/2022] Open
Abstract
Background Models of between-farm transmission of pathogens have identified service vehicles and social groups as risk factors mediating the spread of infection. Because of high levels of economic organization in much of the poultry industry, we examined the importance of company affiliation, as distinct from social contacts, in a model of the potential spread of avian influenza among broiler poultry farms in a poultry-dense region in the United States. The contribution of company affiliation to risk of between-farm disease transmission has not been previously studied. Methodology/Principal Findings We obtained data on the nature and frequency of business and social contacts through a national survey of broiler poultry growers in the United States. Daily rates of contact were estimated using Monte Carlo analysis. Stochastic modeling techniques were used to estimate the exposure risk posed by a single infectious farm to other farms in the region and relative risk of exposure for farms under different scenarios. The mean daily rate of vehicular contact was 0.82 vehicles/day. The magnitude of exposure risk ranged from <1% to 25% under varying parameters. Risk of between-farm transmission was largely driven by company affiliation, with farms in the same company group as the index farm facing as much as a 5-fold increase in risk compared to farms contracted with different companies. Employment of part-time workers contributed to significant increases in risk in most scenarios, notably for farms who hired day-laborers. Social visits were significantly less important in determining risk. Conclusions/Significance Biosecurity interventions should be based on information on industry structure and company affiliation, and include part-time workers as potentially unrecognized sources of viral transmission. Modeling efforts to understand pathogen transmission in the context of industrial food animal production should consider company affiliation in addition to geospatial factors and pathogen characteristics. Restriction of social contacts among farmers may be less useful in reducing between-farm transmission.
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Affiliation(s)
- Jessica H Leibler
- Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
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Beltrán-Alcrudo D, Carpenter TE, Cardona C. A flock-tailored early warning system for low pathogenic avian influenza (LPAI) in commercial egg laying flocks. Prev Vet Med 2009; 92:324-32. [PMID: 19767114 DOI: 10.1016/j.prevetmed.2009.07.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 07/23/2009] [Accepted: 07/24/2009] [Indexed: 10/20/2022]
Abstract
The aim of this study was to develop and evaluate an early warning system (EWS) for commercial egg laying flocks to detect the subtle mortality and egg production changes that characterize low pathogenic avian influenza virus (LPAIV) infections. An EWS will create an alert when the recommended 'trigger point' is reached or exceeded. Previously used EWSs are based on fixed alert levels, while the proposed EWS customizes the alert level to each flock. While a fixed approach may be valid for highly pathogenic diseases, it results in a lower detection probability for low pathogenic diseases. The EWS was based on daily data collected from flocks affected by the 2000-2004 H6N2 LPAI epidemic in California. Three EWSs were evaluated: (1) EWS1, which is triggered when the observed mortality increase or production decrease exceeds more than "x" times the expected daily value (2.75-3.50 times the expected mortality), (2) EWS2, which is triggered when the observed mortality increase or production decrease exceeds more than "y" times during each of 2 consecutive days the expected daily values (1.75-2.15 times the expected mortality), and (3) a combination of the two. The EWSs were evaluated according to three parameters: detection delay (days) of a LPAI outbreak, false alerts (%) and outbreaks missed (%). Results showed that an egg production-based EWS added no benefit to a mortality-based system, mainly because H6N2 LPAI-related egg production decrease always occurred after increase in mortality. Combining the two EWSs resulted in a reduced detection delay and no missed outbreaks, but at the expense of a slight increase in the number of false alerts triggered. The system presented in this study also outperformed fixed EWSs in all three evaluated parameters. The proposed EWS, if used as part of a poultry cooperative program and combined with a rapid laboratory diagnosis, could be a useful tool in the detection and control of LPAI outbreaks and other poultry diseases. Built in a spreadsheet, the system could be inexpensively, easily and quickly incorporated into a commercial egg production farm decision support system. In addition, the proposed system could be quickly adjusted to changing epidemic situations, and easily customized to individual flocks.
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Affiliation(s)
- Daniel Beltrán-Alcrudo
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California - Davis, One Shields Avenue, Davis, CA 95616, USA.
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Ward MP, Maftei D, Apostu C, Suru A. Geostatistical visualisation and spatial statistics for evaluation of the dispersion of epidemic highly pathogenic avian influenza subtype H5N1. Vet Res 2008; 39:22. [DOI: 10.1051/vetres:2007063] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2007] [Accepted: 11/09/2007] [Indexed: 11/14/2022] Open
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Lu H, Castro AE. Evaluation of the infectivity, length of infection, and immune response of a low-pathogenicity H7N2 avian influenza virus in specific-pathogen-free chickens. Avian Dis 2004; 48:263-70. [PMID: 15283413 DOI: 10.1637/7064] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The H7N2 subtype of avian influenza virus (AIV) field isolate (H7N2/chicken/PA/3779-2/97), which caused the 1997-98 AIV outbreak in Pennsylvania, was evaluated for its infectivity, length of infection, and immune response in specific-pathogen-free (SPF) chickens. The composite findings of three clinical trials with various concentrations of virus indicated that this H7N2 subtype contained minimal pathogenicity for chickens. The concentration of the virus in the inoculum proved critical in the establishment of a productive infection in a chicken. Seven-day-old SPF chickens were not infected when inoculated with 10(0.7-2.0) mean embryo lethal dose (ELD50) of the H7N2 virus per bird. At this dose level, the immune response to this virus was not detected by the hemagglutination-inhibition (HI) test. Nonetheless, chickens at ages of 5 and 23 wk old tested were successfully infected when exposed to 10(4.7-5.7) ELD50 of H7N2 infectious doses per bird by various routes of administration and also by direct contact. Infected birds started shedding virus as early as 2 days postinoculation, and the period of virus shedding occurred mostly within 1 or 2 wk postinoculation (WPI). This H7N2 subtype of AIV induced a measurable immune response in all birds within 2 wk after virus exposure. Antibody titers were associated with AIV infectious doses and age of exposure of birds. Challenge of these infected birds with the same H7N2 virus at 5 and 10 WPI indicated the infective virus was recoverable from cloacal swabs at 3 days postchallenge and disappeared thereafter. In these challenged birds, the antibody levels as measured by the HI test spiked within 1-2 wk.
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Affiliation(s)
- Huaguang Lu
- Animal Diagnostic Laboratory, Department of Veterinary Science, The Pennsylvania State University, University Park, PA 16802, USA
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Lu H, Dunn PA, Wallner-Pendleton EA, Henzler DJ, Kradel DC, Liu J, Shaw DP, Miller P. Investigation of H7N2 Avian Influenza Outbreaks in Two Broiler Breeder Flocks in Pennsylvania, 2001–02. Avian Dis 2004; 48:26-33. [PMID: 15077795 DOI: 10.1637/6063] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
An avian influenza (AI) outbreak occurred in meat-type chickens in central Pennsylvania from December 2001 to January 2002. Two broiler breeder flocks were initially infected almost simultaneously in early December. Avian influenza virus (AIV), H7N2 subtype, was isolated from the two premises in our laboratory. The H7N2 isolates were characterized as a low pathogenic strain at the National Veterinary Services Laboratories based on molecular sequencing of the virus hemagglutinin cleavage site and virus challenge studies in specific-pathogen-free leghorn chickens. However, clinical observations and pathologic findings indicated that this H7N2 virus appeared to be significantly pathogenic in meat-type chickens under field conditions. Follow-up investigation indicated that this H7N2 virus spread rapidly within each flock. Within 7 days of the recognized start of the outbreak, over 90% seroconversion was observed in the birds by the hemagglutination inhibition test. A diagnosis of AI was made within 24 hr of bird submission during this outbreak using a combination of virus detection by a same-day dot-enzyme-linked immunosorbent assay and virus isolation in embryonating chicken eggs. Follow-up investigation revealed that heavy virus shedding (90%-100% of birds shedding AIV) occurred between 4 and 7 days after disease onset, and a few birds (15%) continued to shed virus at 13 days post-disease onset, as detected by virus isolation on tracheal and cloacal swabs. AIV was not detected in or on eggs laid by the breeders during the testing phase of the outbreak. The two flocks were depopulated at 14 days after disease onset, and AIV was not detected on the two premises 23 days after depopulation.
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Affiliation(s)
- Huaguang Lu
- Animal Diagnostic Laboratory, Department of Veterinary Science, The Pennsylvania State University, University Park, PA 16802, USA
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