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Avian influenza A H5N1 infections in Bali Province, Indonesia: a behavioral, virological and seroepidemiological study.

ABSTRACT: Bali Province was affected by avian influenza H5N1 outbreaks in birds in October 2003. Despite ongoing circulation of the virus, no human infection had been identified by December 2005.To assess behavioral patterns associated with poultry rearing in Bali, and to identify potential risk factors for H5N1 infection in humans and in household chickens, ducks and pigs.A behavioral, virological and seroepidemiologic survey in 38 villages and three live bird markets was completed in December 2005. A multi-stage cluster design was used to select 291 households with 841 participants from all nine districts in Bali. Specimens were collected from participants as well as a maximum of three pigs, chickens and ducks from each household. Eighty-seven market vendors participated, where specimens were collected from participants as well as chickens and ducks.Twenty out of the 38 villages sampled had H5N1 outbreaks. Despite exposure to H5N1 outbreaks, none of the participants from villages or markets were seropositive for H5N1. None of the pigs tested were positive for H5N1. Virus isolation rate in ducks and chicken in markets was higher than in households. Transport of poultry in or out of villages was a risk factor for outbreaks in household chickens and ducks.The study highlighted that the market chain and associated behaviors may play a role in maintaining the virus in household flocks. The study adds evidence that transmission of H5N1 to humans remains a rare event despite high level handling of both healthy and sick birds.

SUBMITTER: Santhia K

PROVIDER: S-EPMC4634692 | biostudies-other | 2009 May

REPOSITORIES: biostudies-other

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Project description: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.

Dataset Information

Avian influenza A H5N1 infections in Bali Province, Indonesia: a behavioral, virological and seroepidemiological study.

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