DIAGNOSTIC PROCEDURE FOR DETECTION OF HPAI H5N8-BULGARIAN EXPERIENCE DURING THE EPIZOOTIC WAVE IN 2016/2017

Abstract

In the 4 months spanning the 2016/2017 winter (October – January), HPAI H5N8 was the predominant serotype throughout European countries. Bulgaria, an important geographical location for migratory birds crossing Europe through the two major migratory flyways for Africa, was heavily affected with HPAI H5N8 outbreaks. The first detection of HPAI virus serotype H5N8 in Bulgaria was on the 19th of December 2016 in the Vidin region. Subsequently many outbreaks in wild birds and domestic poultry were reported in 15 different administrative regions. By the end of January 2017, the HPAI H5N8 strain was detected in domestic poultry, game birds, wild waterfowl, and zoo birds. The observed and reported symptoms were discoordination, laboured breathing, ataxia, opisthotonos, watery diarrhoea, sudden death, high mortality, weakness, and recumbency. In wild birds data for high mortality was only available for some species, with well-defined hyperaemia of the meninges and brain congestion with a singular haemorrhage being mainly observed, particularly in Dalmatian pelicans. These observations showcase the importance of rapid and accurate detection and subtyping of these HPAI viruses by research laboratories. To tackle this issue, the National Reference laboratory for Influenza A and Newcastle disease in Sofia adapted a modified real-time RT-PCR assay for detection of the N8 subtype in domestic and wild birds. The aim of this study is to present a Bulgarian experience in diagnosis of HPAI H5N8 subtype during 2016/2017 epizootic wave.