Analysis of H5N1 avian influenza infections from wild bird surveillance in Hong Kong from January 2006 to October 2007

Abstract

Summary Intensive surveillance of dead wild birds for H5N1 avian influenza infection is conducted in Hong Kong. Between January 2006 and October 2007 pooled cloacal and tracheal (C&T) swabs from 17,592 dead wild birds (from 16 different orders including 82 genera) were tested and 33 H5N1 HPAI viruses were isolated. No H5N1 infection has occurred in poultry farms or live poultry markets in Hong Kong since January 2003. The gross and histopathology in the various H5N1 infected avian species is described, along with the performance of the virology, PCR and antigen detection tests used. This evaluation also included determination of virus titres and detection limits for the H5 haemagglutinin gene (H5)and matrix gene (M) real-time reverse transcription PCR tests (RRT-PCR) in C&T swabs from 12 wild birds. The viruses isolated belonged to Clades 2.3.2 and 2.3.4 and within Clade 2.3.4 some clustering was evident based on H5 HA sequencing. However there were no differences in the pathology findings between these sub-groupings and the various diagnostic tests gave similar results for these viruses, except for a loss in sensitivity of the H5 RRT-PCR for several viruses in one cluster from birds submitted in February 2007.

Characterization of Avian Influenza Viruses A (H5N1) from Wild Birds, Hong Kong, 2004–2008

“…All virus isolation was conducted in biosafety level 3 facilities. Details of the avian infl uenza (H5N1) surveillance program in Hong Kong for dead wild birds, including pathologic fi ndings and diagnostic testing, are reported separately (17).…”

“…In addition, avian infl uenza surveillance has been conducted on wild birds found dead (wild birds and caged birds released for ceremonial purposes are collectively referred to as wild birds in this article) (17). Until the recent incursion of HPAI virus (H5N1) in June 2008, no viruses of subtype H5N1 had been detected on poultry farms or in markets in Hong Kong since November 2003, although 2 HPAI viruses (H5N1) were detected in chickens smuggled into Hong Kong in 2006 (18).…”

Anticuerpos séricos contra la enfermedad de Newcastle e Influenza Aviar en aves rapaces de Chile

“…El virus tipo A es el que puede causar enfermedad en aves y se ha presentado en cerca de 90 especies dentro de 12 órdenes de aves (10). Sin embargo, son las aves acuáticas, particularmente las especies de los órdenes Anseriformes (patos, gansos y cisnes) (3,11) y Charadriiformes (gaviotas) (11) las que constituyen el mayor reservorio (3). Por el contrario, los informes de infección del virus de la IA en aves rapaces son escasos (12).…”

“…Por el contrario, los informes de infección del virus de la IA en aves rapaces son escasos (12). A pesar de este hecho, se han reportado rapaces de los órdenes Falconiformes y Strigiformes positivas al virus de la IA en Asia, África y Europa (11,12). En Chile, en el año 2002 se produjeron dos brotes, limitados a un sólo plantel en la Región de Valparaíso (Chile).…”

Evolutionary genetics of highly pathogenic H5N1 avian influenza viruses isolated from whooper swans in northern Japan in 2008

“…We hypothesize that the first reassortment event, which is associated with displacement of the NP gene, occurred before 2005 because the HA clade 2.3.4 virus whose NP gene was derived from an HA clade 2.3.2 virus was first detected in Hunan and Guangxi provinces in 2005 (Fig. 2) [11,14].…”