PhD Defence: Epidemiology of Highly Pathogenic Avian Influenza Virus H5N1 in Indonesian Poultry

Summary dissertation

After its first detection in 1996, bird flu (highly pathogenic avian influenza virus) of the H5N1 subtype continues to circulate worldwide with a major impact on poultry health and high economic losses. Also, occasionally human infections with bird flu are reported. Therefore, there is a fear that bird flu becomes transmissible among humans and causes the next pandemic. 
In Indonesia, bird flu of the H5N1 subtype circulates among poultry since its first introduction in 2003. To support control of bird flu in Indonesia, there is a need to improve the understanding of its spread, the genetic changes in bird flu viruses and risk factors associated with infections. Furthermore, it is important to describe clinical signs caused by infections with recent virus variants to improve recognition of the disease. 
Results of studies described in this thesis indicate that visitors of backyard chicken farms had a higher frequency of contacts than those of other farms, which might result in more frequent spread of bird flu among these farms. Analysis of genetic changes in bird flu viruses indicated that the viruses continue to evolve and that also genetic mixes among different bird flu viruses occurred. However, results also suggest that only two introductions of bird flu occurred into Indonesia, and the virus continued to circulate within Indonesia afterwards. Most observed clinical signs in chickens were skin lesions and breathing difficulties, while ducks had more often neurological disease.
Results of studies described in this thesis highlight the importance to continue and improve the detection and reporting of bird flu and analyze genetic variants among poultry, live bird markets and wild birds.