Entry of H5N1 highly pathogenic avian influenza virus into Europe through migratory wild birds: a qualitative release assessment at the species level

Abstract

Aims: To estimate qualitatively the probabilities of release (or entry) of Eurasian lineage H5N1 highly pathogenic avian influenza (HPAI) virus into Great Britain (GB), the Netherlands and Italy through selected higher risk species of migratory water bird. Methods and Results: The probabilities of one or more release events of H5N1 HPAI per year (P release ) were estimated qualitatively for 15 avian species, including swans, geese, ducks and gulls, by assessing the prevalence of H5N1 HPAI in different regions of the world (weighted to 2009) and estimates of the total numbers of birds migrating from each of those regions. The release assessment accommodated the migration times for each species in relation to the probabilities of their surviving infection and shedding virus on arrival. Although the predicted probabilities of release of H5N1 per individual bird per year were low, very low or negligible, P release was high for a few species reflecting the high numbers of birds migrating from some regions. Values of P release were generally higher for the Netherlands than for GB, while ducks and gulls from Africa presented higher probabilities to Italy compared to the Netherlands and GB. Conclusions: Bird species with high values of P release in GB, the Netherlands and Italy generally originate from within Europe based on data for global prevalence of H5N1 between 2003 and 2009 weighted to 2009. Potential longdistance transfer of H5N1 HPAI from North Asia and Eurasia to GB, the Netherlands and Italy is limited to a few species and does not occur from South-East Asia, an area where H5N1 is endemic. Significance and Impact of the Study: The approach accommodates biogeographical conditions and variability in the estimated worldwide prevalence of the virus. The outputs of this release assessment can be used to inform surveillance activities through focusing on certain species and migratory pathways.

Risk factors associated with highly pathogenic avian influenza subtype H5N8 outbreaks on broiler duck farms in South Korea

“…To construct strategies to control diseases, the identification of timely risk factors in outbreaks is important (Lewallen & Courtright, 1998). Previous avian influenza epidemiologic studies have identified several risk factors from a variety of settings and countries (Abbas, Wilking, Horeth-Bontgen, & Conraths, 2012;Arriola et al, 2015;Beaudoin et al, 2014;Biswas et al, 2011;Boender et al, 2007;Bui, Gardner, MacIntyre, & Sarkar, 2017;Cao et al, 2010;Chaudhry, Rashid, Thrusfield, Welburn, & Bronsvoort, 2015;Desvaux et al, 2011;Dinh et al, 2006;Fang et al, 2008;Fasina, Rivas, Bisschop, Stegeman, & Hernandez, 2011;Gale et al, 2014;Garber et al, 2016;Gilbert et al, 2006;Henning et al, 2009;Huang, Zeng, & Wang, 2016;Iglesias, Jesus Munoz, Martinez, & de la Torre, 2010;Kung et al, 2007;Liu et al, 2015;Lohiniva et al, 2013;Loth, Gilbert, Osmani, Kalam, & Xiao, 2010;Mannelli, Ferre, & Marangon, 2006;Martin et al, 2011;McQuiston et al, 2005;Metras et al, 2013;Mounts et al, 1999;Musa, Abdu, Sackey, & Oladele, 2013;Nishiguchi et al, 2007;Osmani et al, 2014;Paul et al, 2011;Tenzin, Wangdi, & Rai, 2017;Thomas et al, 2005;Thompson, Sinclair, & Ganzevoort, 2008;…”

Qualitative import risk assessment: A proposed method for estimating the aggregated probability of entry of infection

“…In contrast, EFSA 2012describes qualitative probabilities in terms of numerical bounds (see Table 2). There are a limited number of studies that have considered qualitative evaluation of the aggregated probability given in Equation (1) (Snary et al, 2012;Gale et al, 2014). In the examples which do exist, the estimate of probability has been undertaken subjectively, with assumptions being made on how to combine, for example a low p with a high n or a high p with a low n. To determine the most appropriate way to formalise this estimation, we break down Equation 1into separate components.…”

“…However, the evaluation of the product of two qualitative probabilities has been tackled. Several matrices for this product have been published (Gale et al, 2009;Gale et al, 2010;Wieland et al, 2011;Gale et al, 2014). Of these, the matrix of Gale et al (2010) is considered most appropriate from a mathematical point of view because it is based on the premise that probabilities can only take values between 0 and 1 and that the product of two probabilities is at most, the minimum of the two values (see Table 3).…”

“…Wieland et al (2011) present a matrix which follows the same approach, discussing the idea of conditional dependence between the two probabilities. The other papers have presented modifications to the matrix of Gale et al (2010), at the lower end of the ordinal scale (Gale et al, 2009;Gale et al, 2014). These modifications are, to some extent, subjective and arise because of assumed quantitative ranges for the lower end qualitative probabilities in an attempt to account for the problem that, for example, the product of two low probabilities may be lower than low.…”

“…The units for the individual probability are thus "per product" or "per animal" as in the case of capripoxviruses on imported ruminant skins and hides (Gale et al 2016). When data are available on the number of units imported per year or per batch, the individual probability may be scaled up to give the aggregated probability, for example the risk question may be, what is the probability of one or more infected units being introduced per year as in the case of avian influenza virus in migratory wild birds (Gale et al 2014). Implicit in the aggregated probability is the number of units per batch or imported over a given time period.…”