Review of the highly pathogenic avian influenza outbreak in Texas, 2004

Pelzel, Angela M.; McCluskey, Brian J.; Scott, Aaron E.

doi:10.2460/javma.228.12.1869

Cited by 35 publications

(19 citation statements)

References 9 publications

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“…Whilst outbreaks of influenza in domestic poultry continue to be blamed on contact with free-range and wild birds, based on the circumstantial evidence of co-location of wild birds and domestic poultry in time and space [7], illegal movements of poultry and other avian species have been documented as contributing to H5N1 spread in several instances [20,24]. Live bird markets have also been the presumed source of avian influenza outbreaks in domestic poultry, notably in the United States [6,10,16,18,22] and in Asia [24].…”

Section: Discussionmentioning

confidence: 99%

Geostatistical visualisation and spatial statistics for evaluation of the dispersion of epidemic highly pathogenic avian influenza subtype H5N1

et al. 2008

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-The aim of this study was to evaluate a range of statistical and geostatistical methods for their usefulness in providing insights into how highly pathogenic avian influenza (HPAI) subtype H5N1 might spread through a national population of village poultry. The insights gained allow the generation of disease dispersion hypotheses. The case study data set consisted of 161 outbreaks of HPAI subtype H5N1 in village poultry reported in Romania between

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Section: Discussionmentioning

confidence: 99%

Geostatistical visualisation and spatial statistics for evaluation of the dispersion of epidemic highly pathogenic avian influenza subtype H5N1

et al. 2008

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“…These viruses can initially be found in asymptomatically infected flocks or in flocks with clinical signs consistent with LPAI infection. (Lee et al, 2005b;Pelzel et al, 2006) Typical HPAI signs may be seen with time as these viruses evolve to become more pathogenic.…”

Section: Onset Of Clinical Signs In Hpai-infected Chickensmentioning

confidence: 99%

The onset of virus shedding and clinical signs in chickens infected with high-pathogenicity and low-pathogenicity avian influenza viruses

2008

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Some avian influenza viruses may be transmissible to mammals by ingestion. Cats and dogs have been infected by H5N1 avian influenza viruses when they ate raw poultry, and two human H5N1 infections were linked to the ingestion of uncooked duck blood. The possibility of zoonotic influenza from exposure to raw poultry products raises concerns about flocks with unrecognized infections. The present review examines the onset of virus shedding and the development of clinical signs for a variety of avian influenza viruses in chickens. In experimentally infected birds, some high-pathogenicity avian influenza (HPAI) and low-pathogenicity avian influenza (LPAI) viruses can occur in faeces and respiratory secretions as early as 1 to 2 days after inoculation. Some HPAI viruses have also been found in meat 1 day after inoculation and in eggs after 3 days. There is no evidence that LPAI viruses can be found in meat, and the risk of their occurrence in eggs is poorly understood. Studies in experimentally infected birds suggest that clinical signs usually develop within a few days of virus shedding; however, some models and outbreak descriptions suggest that clinical signs may not become evident for a week or more in some H5 or H7 HPAI-infected flocks. During this time, avian influenza viruses might be found in poultry products. LPAI viruses can be shed in asymptomatically infected or minimally affected flocks, but these viruses are unlikely to cause significant human disease.

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“…As a consequence, it is an acceptable approximation to neglect within-farm dynamics in the model. In the specific case of avian influenza, epidemiological investigations of outbreaks in the USA reveal that the most likely source of infection for domestic farms is bird-to-bird contact at live birds markets (Garnett 1987;Pelzel et al 2006), though the possibility of infection through feed or water contamination, cages, and other equipment cannot be ruled out. Moreover, several other studies have emphasized the central role of backyard poultry flocks in the spread of HPAI virus, both in developed (e.g., the Netherlands; Bavinck et al 2009) and developing countries (e.g., Vietnam; Henning et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Getting a free ride on poultry farms: how highly pathogenic avian influenza may persist in spite of its virulence

Leo

Bolzoni

2011

Theor Ecol

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It is well-known that highly pathogenic avian influenza (HPAI) strains can arise from low pathogenic strains (LPAI) during epidemics in poultry farms. Despite this, the possibility that partial cross-immunity triggered by previous exposure to LPAI viruses may reduce the pathogenicity of HPAI and thus enhance its persistence has been generally overlooked in both empirical and theoretical work on avian influenza. We propose a simple mathematical model to investigate the interacting dynamics of HPAI and LPAI strains of avian influenza in small-scale poultry farms. Through the analysis of a deterministic ordinary differential equations model, we show that: (1) for a wide range of realistic model parameters, the reduction in pathogenicity yielded by previous LPAI infection might allow an HPAI strain that would not be able to persist in a host population when alone (ℜ 0 <1) to invade and co-exist in the host population along with the LPAI strain and (2) the coexistence between the HPAI and LPAI strains may be characterized by multiyear periodicity. Because simulations showed that troughs between epidemics can be deep, with only a fraction of existing flocks infected by the HPAI strain, we also ran an individual-based stochastic version of the dynamical model to analyze the potential for natural fade-out of the HPAI strain. The analysis of the stochastic model confirms the prediction that previous exposure to a LPAI strain can significantly increase the duration of the epidemics by an HPAI strain before it fades from the population.

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Review of the highly pathogenic avian influenza outbreak in Texas, 2004

Cited by 35 publications

References 9 publications

Geostatistical visualisation and spatial statistics for evaluation of the dispersion of epidemic highly pathogenic avian influenza subtype H5N1

Geostatistical visualisation and spatial statistics for evaluation of the dispersion of epidemic highly pathogenic avian influenza subtype H5N1

The onset of virus shedding and clinical signs in chickens infected with high-pathogenicity and low-pathogenicity avian influenza viruses

Getting a free ride on poultry farms: how highly pathogenic avian influenza may persist in spite of its virulence

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