The Epidemiology of the Highly Pathogenic H5n1 Avian Influenza in Mute Swan (Cygnus Olor) and Other Anatidae in the Dombes Region (France), 2006

Abstract

In February 2006, a highly pathogenic avian influenza (HPAI) H5N1 virus was isolated from Common Pochards (Aythia ferina) in the Dombes region of France, an important migrating and wintering waterfowl area. Thereafter, HPAI H5N1 virus was isolated from 39 swab pools collected from dead waterfowl found in the Dombes, but only from three pooled samples collected outside of this area but located on the same migration flyway. A single turkey farm was infected in the Dombes. The epizootic lasted 2 mo and was restricted to the Dombes area. Virus-positive pools were detected in 20 of 1,200 ponds and infected Mute Swans (Cygnus olor) represented 82% of the virus-positive pools. Other infected species included Common Pochard (n=4), Grey Heron (Ardea cinerea, n=1), Eurasian Buzzard (Buteo buteo, n=1), and Greylag Goose (Anser anser, n=1). Despite intensive monitoring during and after the outbreak, HPAI H5N1 virus was not isolated from healthy wild birds. Our results are consistent with an HPAI H5N1-virus introduction into the Dombes via migrating ducks. These birds could have been pushed west by a severe cold spell in central Europe where the virus had already been detected. The Mute Swan served as an excellent epidemiologic sentinel during this outbreak; swans appear to be highly sensitive to infection with these viruses and swan mortality was easy to detect. During the outbreak, the mortality rates for wild birds remained moderate and the virus affected a limited number of species.

Estimating Dynamic Risk Factors for Pathogen Transmission Using Community-Level Bird Census Data at the Wildlife/Domestic Interface

“…and Ciconiiformes (Egret and Ibis spp.). These orders and families have been found with, or dead of, LPAI or HPAI strains (Gauthier-Clerc et al 2007, Hars et al 2008, Stoops et al 2009). Additionally, the MR curve ( Figure 4) was consistent across the two years and indicated a maximum risk of AIV presence in the waterfowl community during the hot-dry season, when migratory and paleartic waterfowl are present in the system, coming from areas where AIV strains circulate.…”

Within-host variation of avian influenza viruses

“…It is notable that species not normally associated with avian influenza virus infection have been found to be infected, and examples include sparrows, crows, magpies and storks, and birds of prey that may have fed on infected poultry, e.g. falcons (Monne et al 2008), kestrels (Smith et al 2009), vultures (Ducatez et al 2007a,b) and buzzards (Hars et al 2008). The presence of H5N1 viruses in the bar-headed goose population around Qinghai Lake in late 2005 (Chen et al 2005) provides a striking example of wild-bird infection, and it is postulated that virus was carried from Qinghai Lake westwards through bird migration.…”

The Cold European Winter of 2005–2006 Assisted the Spread and Persistence of H5N1 Influenza Virus in Wild Birds

“…They suggested that local transmission through direct contact was facilitated by the clustered geographic distribution of the water bodies recorded on the Baltic coast and also at Lake Constance and in the Helme reservoir (Wilking et al, 2009). In other sites, however, such as the Dombes region in France, infections remained spatially more restricted, with several noninfected ponds and a rather low mortality rate in wild birds (Hars et al, 2008).…”

“…In the Dombes Region in France, densities of mute swans (Cygnus olor) and other water birds in infected ponds were sixfold and threefold, respectively, of those in uninfected ponds (Hars et al, 2008). Conversely, in other instances, relatively few infected birds were recorded in places with large populations of wintering birds (Gaidet et al, 2007;Globig et al, 2009;Hofmann et al, 2008;Nagy et al, 2007).…”

“…However, the precise contribution of mute swans to the sudden dispersion of H5N1 remains elusive; mute swans may have acted mainly as sentinels for H5N1 virus circulation (Nagy et al, 2007). Other wild birds, including duck species, presumably also contributed to the introduction of H5N1 virus into central and western parts of Europe (Hars et al, 2008;Starick et al, 2008). That several bird species AUC area under curve of the receiver operating character, Dc proportion of variance explained by the model, T max long-term January 0°C isotherm given by T max , LR log-likelihood ratio chi-square test comparing the model with and without the distance to the January 0°C isotherm (T max = 0).…”