Avian Influenza Outbreaks in Germany â Development of New Avian Vaccines

Abstract

Germany was among the first countries to be hit by highly pathogenic avian influenza (HPAI) or fowl plague virus soon after it first surfaced in Italy at the end of the 19th century. Subsequently, only very few sporadic outbreaks occurred despite the continuous presence of low pathogenic avian influenza viruses in wild birds in Germany. However, fowl plague episodes in poultry occurred in 1979 derived from a lowpathogenic strain originating from wild birds, in 2003 in the context of the Dutch epidemic and again in 2006 and 2007 by the introduction of HPAI virus (HPAIV) subtype H5N1 of Asian origin. The latter was associated with the westward spread of HPAIV H5N1 Asia out of China into Europe. In total, 343 (2006) and 326 (2007) wild birds, respectively, as well as one bird kept in a zoo, three cats and one stone marten as well as one commercial poultry holding were found infected with HPAIV H5N1 Asia. Molecular epidemiological analyses demonstrated that two distinct introductions occurred into Germany in spring 2006 resulting in a Northern and Southern German lineage. The last demonstration of HPAIV H5N1 in 2006 in Germany occurred in August. However, in June 2007, HPAIV H5N1 resurfaced in wild birds and also affected several poultry holdings leading to the destruction of more than 350,000 animals. Molecular epidemiological analyses demonstrated that in 2006 two genetically distinct viruses circulated in Germany, whereas in 2007 a third genotype was detected. This indicated a total of three separate introductions of HPAI H5N1 into Germany in 2006 and 2007. The arrival of HPAIV H5N1 in Germany together with restrictions in keeping poultry outdoors renewed requests for vaccination. However, currently available inactivated vaccines suffer from several shortcomings including the necessity for individual application and lack of an easy and sensitive differentiation between vaccinated and infected animals. Thus, the development of novel vaccines against HPAIV has become of prime importance. The most promising approaches include the use of viral vectors expressing the protective influenza virus hemagglutinin. They are primarily based on recombinant adeno-, pox-, paramyxo- or herpesviruses. In particular, the use of recombinant Newcastle disease virus as carrier for influenza hemagglutinin offers the advantage to be able to protect simultaneously against two of the most important chicken pathogens.