Highly pathogenic avian influenza (HPAI) A(H5N1) viruses have been circulating since 2003 in Indonesia, with major impacts on poultry health, severe economic losses, and 168 fatal laboratory-confirmed human cases. We performed phylogenetic analysis on 39 full-genome H5N1 virus samples collected during outbreaks among poultry in 2015–2016 in West Java and compared them with recently published sequences from Indonesia. Phylogenetic analysis revealed that the hemagglutinin gene of all samples belonged to 2 genetic groups in clade 2.3.2.1c. We also observed these groups for the neuraminidase, nucleoprotein, polymerase, and polymerase basic 1 genes. Matrix, nonstructural protein, and polymerase basic 2 genes of some HPAI were most closely related to clade 2.1.3 instead of clade 2.3.2.1c, and a polymerase basic 2 gene was most closely related to Eurasian low pathogenicity avian influenza. Our results detected a total of 13 reassortment types among HPAI in Indonesia, mostly in backyard chickens in Indramayu.

Although vaccination of poultry for control of highly pathogenic avian influenza virus (HPAIV) H5N1 has been practiced during the last decade in several countries, its effectiveness under field conditions remains largely unquantified. Effective HPAI vaccination is however essential in preventing incursions, silent infections and generation of new H5N1 antigenic variants. The objective of this study was to asses the level and duration of vaccine induced immunity in commercial layers in Indonesia. Titres of H5N1 haemagglutination inhibition (HI) antibodies were followed in individual birds from sixteen flocks, age 18–68 week old (wo). The study revealed that H5N1 vaccination had highly variable outcome, including vaccination failures, and was largely ineffective in providing long lasting protective immunity. Flocks were vaccinated with seven different vaccines, administer at various times that could be grouped into three regimes: In regime A, flocks (n = 8) were vaccinated two or three times before 19 wo; in regime B (n = 2), two times before and once after 19 wo; and in regime C (n = 6) three to four times before and two to three times after 19 wo. HI titres in regime C birds were significantly higher during the entire observation period in comparison to titres of regime A or B birds, which also differed significantly from each other. The HI titres of individual birds in each flock differed significantly from birds in other flocks, indicating that the effectiveness of field vaccination was highly variable and farm related. Protective HI titres of >4log2, were present in the majority of flocks at 18 wo, declined thereafter at variable rate and only two regime C flocks had protective HI titres at 68 wo. Laboratory challenge with HPAIV H5N1 of birds from regime A and C flocks confirmed that protective immunity differed significantly between flocks vaccinated by these two regimes. The study revealed that effectiveness of the currently applied H5N1 vaccination could be improved and measures to achieve this are discussed.

Background and Aim: Existing data on the characteristics of infectious bronchitis virus (IBV) gathered throughout Indonesia have been recognized to indicate variants similar to globally distributed vaccine strains. Despite past and current intensive vaccination programs, IBV infections in the country's poultry industry have not been effectively controlled. Therefore, this study aimed to investigate the genotype of several isolates based on partial S1 gene sequences. In particular, the investigation is directed to focus on layer chickens in actively vaccinated farms indicating IBV symptoms. Materials and Methods: Samples were isolated from ten different layer chicken flocks experiencing respiratory problem, drops in egg production, and a "penguin-like" stance, which were collected from commercial poultry farms in Central Java and Yogyakarta regions, Indonesia, within the periods of 2012-2018. Fragment of the S1 gene of IBV sampled from actively vaccinated commercial poultry farms was amplified using primer 5'-aca tgg taa ttt ttc aga tgg-3' (forward) and 5'-cag att gct tac aac cac c-3' (reverse) with the length of polymerase chain reaction (PCR) product at 383 bp. The sequence of samples was then compared with the sequence of reference S1 gene nucleotides of IBV from NCBI GenBank database. The amino acid analysis and multiple alignment sequence were conducted using Mega X. Results: During necropsy, enlargement of the oviduct and swollen kidney were observed. Reverse transcription-PCR diagnosis of their 383 bp S1 gene showed that all samples were IBV positive. Phylogenetic analysis of the S1 gene discovered seven samples to be clustered as 4/91-like strains. Meanwhile, the remaining three samples were grouped in QX-like strain cluster. Conclusion: This study is a pioneering report providing molecular evidence of pathogenic QX-like and 4/91-like strains circulating in Indonesia. Findings discovered, in this study, strongly suggested the importance of improving protections by available IBV vaccines through updated circulating strain clusters. It is critical to ensure the delivery of an effective control measurement of and vaccination protocols against IBV infections in the country's commercial poultry industry in particular and worldwide in general.

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