The paper analyzes the first cases of highly pathogenic avian influenza (HPAI) caused by H5N1 subtype in wild birds in Poland. From mid-February, when the H5N1 virus was found in wild birds on Ruegen Island in Germany, the number of samples received by the National Reference Laboratory (NRL) for HPAI diagnosis in Pu³awy increased significantly. Samples of organs from wild birds (but occasionally from poultry and mammals) were tested by RT-PCR/H5, and in the case of positive results by RT-PCR/N1 and on SPF embryonated eggs. The first case of H5 was identified on 5th of March in 2 dead mute swans in Toruñ. Further tests proved it was the highly pathogenic H5N1 virus. The results obtained by the NRL were entirely confirmed by the Community Reference Laboratory in Weybridge, UK. The H5N1-positive swans were part of a flock of 113 mute swans. All birds from that flock were locked up in an aviary on 10th of March. On 15th of March one swan in the aviary died and was found positive for H5N1. On 28th of March, samples of tracheal and cloacal swabs as well as blood samples were collected from 112 live swans and submitted to the NRL. Thirty two swans were H5-positive in RT-PCR test and eighty three swans were serologically positive in the haemagglutination inhibition test with H5 antigen. On 1st of April, 80 swans negative in RT-PCR/H5 were released free while 32 swans were euthanized two days later. Subsequent cases of HPAI/H5N1 were found in: Kostrzyñ (1 outbreak) in 2 mute swans, 1 hawk and 1 grey heron, winoujcie (1 outbreak) in 1 goosander, Bydgoszcz (3 outbreaks) in 19 mute swans, Grudzi¹dz (2 outbreaks) in 2 mute swans, and Warta (1 outbreak) in 1 mute swan. Altogether, by the end of June 2006, samples from 1,489 wild birds (multiple species), 113 poultry (chickens, turkeys, ducks, geese, ostriches) and 22 mammals (cats, dogs, polecat, otter) had been tested. The preliminary data suggests a high level of genetic similarity in all isolated Polish H5N1 strains with other H5N1 strains isolated in Europe in 2006 and their homology with strains isolated during a large HPAI H5N1 outbreak at Qinghai Lake in China in 2005.
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