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Henning J.,University of Queensland | Morton J.M.,Jemora Pty Ltd. | Wibawa H.,University of Queensland | Wibawa H.,CSIRO | And 6 more authors.
Epidemiology and Infection | Year: 2013

A prospective longitudinal study was conducted on 96 smallholder duck farms in Indonesia over a period of 14 months in 2007 and 2008 to monitor bird-and flock-level incidence rates of H5 highly pathogenic avian influenza (HPAI) infection in duck flocks, and to identify risk factors associated with these flocks becoming H5 seropositive. Flocks that scavenged around neighbouring houses within the village were at increased risk of developing H5 antibodies, as were flocks from which carcases of birds that died during the 2 months between visits were consumed by the family. Duck flock confinement overnight on the farm and sudden deaths of birds between visits were associated with lower risk of the flock developing H5 antibodies. Scavenging around neighbouring houses and non-confinement overnight are likely to be causal risk factors for infection. With this study we have provided insights into farm-level risk factors of HPAI virus introduction into duck flocks. Preventive messages based on these risk factors should be included in HPAI awareness programmes. © 2012 Cambridge University Press. Source

Henning J.,University of Queensland | Wibawa H.,University of Queensland | Wibawa H.,CSIRO | Wibawa H.,Disease Investigation Center Regional Wates | And 4 more authors.
World's Poultry Science Journal | Year: 2012

Ducks are considered to play an important role in the transmission and maintenance of the Highly Pathogenic Avian Influenza (HPAI) virus. However, there is limited information on duck management practices in countries where HPAI is endemic. A cross-sectional questionnaire survey was conducted on 96 'stationary' smallholder duck farms in Indonesia to describe the management of ducks and to identify practices that could potentially promote the risk of HPAI spread. The mean flock size was 29 ducks, ranging from 1 up to 150 birds. Both the sale and the consumption of eggs were the most important purposes of duck keeping, followed by the use of droppings for fertilizer and the production of meat ducks. About 77% of duck owners allowed their ducks to scavenge. Important hazards for interspecies HPAI virus transmission related to scavenging were identified: 1) intermingling between ducks and chickens on duck farms (48%); 2) frequent contact with neighbours' chickens (44%); 3) visits to the same paddies by duck flocks from other farms (88%); 4) in the paddies, contact between duck flock and other ducks, chickens, people and wild birds as reported by 88%, 30%, 80% and 77% of duck owners respectively; 5) the keeping of singing birds by 17% of farmers; 6) predators such as the small Asian mongoose (Herpestes javanicus) (25%) and feral cats (20%) visiting the duck farms (these species are susceptible to HPAI infection and might play a role in the spread of the HPAI virus). Many duck owners associated deaths of their birds with the use of pesticides in the rice paddies, and appeared to be more concerned about pesticide toxicity, problems that inhibit scavenging ability and external parasites than about HPAI, which in general was not considered to be of high importance. Hence HPAI vaccination or preventive culling of ducks during disease outbreaks was not conducted on the study farms. Copyright © 2012 World's Poultry Science Association. Source

Wibawa H.,CSIRO | Wibawa H.,University of Queensland | Wibawa H.,Disease Investigation Center Regional Wates | Henning J.,University of Queensland | And 6 more authors.
Virology Journal | Year: 2011

Background: Indonesia is one of the countries most severely affected by H5N1 highly pathogenic avian influenza (HPAI) virus in terms of poultry and human health. However, there is little information on the diversity of H5N1 viruses circulating in backyard farms, where chickens and ducks often intermingle. In this study, H5N1 virus infection occurring in 96 smallholder duck farms in central Java, Indonesia from 2007-2008 was investigated and the molecular and antigenic characteristics of H5N1 viruses isolated from these farms were analysed. Results: All 84 characterised viruses belonged to H5N1 clade 2.1 with three virus sublineages being identified: clade 2.1.1 (1), clade 2.1.3 (80), and IDN/6/05-like viruses (3) that did not belong to any of the present clades. All three clades were found in ducks, while only clade 2.1.3 was isolated from chickens. There were no significant amino acid mutations of the hemagglutinin (HA) and neuraminidase (NA) sites of the viruses, including the receptor binding, glycosylation, antigenic and catalytic sites and NA inhibitor targets. All the viruses had polybasic amino acids at the HA cleavage site. No evidence of major antigenic variants was detected. Based on the HA gene, identical virus variants could be found on different farms across the study sites and multiple genetic variants could be isolated from HPAI outbreaks simultaneously or at different time points from single farms. HPAI virus was isolated from both ducks and chickens; however, the proportion of surviving duck cases was considerably higher than in chickens. Conclusions: The 2.1.3 clade was the most common lineage found in this study. All the viruses had sequence characteristic of HPAI, but negligible variations in other recognized amino acids at the HA and NA proteins which determine virus phenotypes. Multiple genetic variants appeared to be circulating simultaneously within poultry communities. The high proportion of live duck cases compared to chickens over the study period suggests that ducks are more likely to survive infection and they may better suit the role of long-term maintenance host for H5N1. As some viruses were isolated from dead birds, there was no clear correlation between genetic variations and pathogenicity of these viruses. © 2011 Wibawa et al; licensee BioMed Central Ltd. Source

Wibawa H.,CSIRO | Wibawa H.,University of Queensland | Wibawa H.,Disease Investigation Center Regional Wates | Bingham J.,CSIRO | And 9 more authors.
PLoS ONE | Year: 2014

Ducks are important maintenance hosts for avian influenza, including H5N1 highly pathogenic avian influenza viruses. A previous study indicated that persistence of H5N1 viruses in ducks after the development of humoral immunity may drive viral evolution following immune selection. As H5N1 HPAI is endemic in Indonesia, this mechanism may be important in understanding H5N1 evolution in that region. To determine the capability of domestic ducks to maintain prolonged shedding of Indonesian clade 2.1 H5N1 virus, two groups of Pekin ducks were inoculated through the eyes, nostrils and oropharynx and viral shedding and transmission investigated. Inoculated ducks (n = 15), which were mostly asymptomatic, shed infectious virus from the oral route from 1 to 8 days post inoculation, and from the cloacal route from 2-8 dpi. Viral ribonucleic acid was detected from 1-15 days post inoculation from the oral route and 1-24 days post inoculation from the cloacal route (cycle threshold <40). Most ducks seroconverted in a range of serological tests by 15 days post inoculation. Virus was efficiently transmitted during acute infection (5 inoculation-infected to all 5 contact ducks). However, no evidence for transmission, as determined by seroconversion and viral shedding, was found between an inoculation-infected group (n = 10) and contact ducks (n = 9) when the two groups only had contact after 10 days post inoculation. Clinical disease was more frequent and more severe in contact-infected (2 of 5) than inoculation-infected ducks (1 of 15). We conclude that Indonesian clade 2.1 H5N1 highly pathogenic avian influenza virus does not persist in individual ducks after acute infection. © 2014 Wibawa et al. Source

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