Eva, I; Lajos, T; Peter, Z; Eorsne, N; Mihaly, DK; Robert, G; Adam, B; Nimrod, P; Lazar, M; Adam, Dan; Krisztina, U; Levente, S; Zoltan, D; Dora, R; ,
Diseases caused by highly pathogenic avian influenza strain (H5N1 subtype) were confirmed in 13 goose and 15 duck (11 Pekingese and 4 mulard) flocks in the second quarter of 2006 in a region of dense waterfowl flock population in the Southern part of Danube-Tisza Interfluve region. The number of animals in the goose flocks varied between 1000 and 5000 and that of duck flocks between 3000 and 30.000. Small flocks were also involved (30-100 animals) and among them one, where fowls and guinea fowls were diseased, as well.Daily number of death increased dramatically in the infected goose and duck flocks. Because of official measure (killing) observation of the flock level course of the disease was not possible. infected animals showed lethargy, anorexia, serous nasal discharge, lacrimation and neurological signs (deviation of the head, head-tremor, -lateral deviation, and leg and wing paralysis). In some cases animals were found dead without any previous clinical signs. There were no skin lesions (cyanosis, oedema, haemorrhage, necrosis) in the waterfowls.During post mortem and histopathological examinations - both in case of duck and goose flocks similarly and of the same frequency but in ducks in milder form - acute-subacute changes (haemorrhages in the different tissues, organs, mainly on serous membranes, necrotic foci in the pancreas, myocardium, liver and, almost in all cases, lymphocytic encephalitis) typical to highly pathogenic avian influenza strains were observed. Immunohistochernical examination revealed viral antigen mainly in the brain of dead geese. Causative viral particles were observed with electron microscope, as well.The virus was isolated in embryonated SPF fowl eggs, and typing was carried out by haemagglutination inhibition test using H5 and H7 subtype-specific polyclonal sera. H5 gene was identified by Tag Man PCR. Identification of the N subtype was performed by EU avian influenza reference laboratory (Avian Virology Laboratory, VLA, Weybridge, UK).