Characteristics of two duck farming systems in the Mekong Delta of Viet Nam: stationary flocks and moving flocks, and their potential relevance to the spread of highly pathogenic avian influenza

Abstract

Ducks are considered to play a major role in the spread of highly pathogenic avian influenza (HPAI) H5N1 in Viet Nam, but detailed information on their management is limited. We distinguished two different systems (1) stationary duck flocks that are not commonly driven to rice fields beyond village boundaries and that are confined overnight on farms and (2) moving duck flocks that are intentionally driven to rice fields beyond village boundaries, that are not returning to home farms for extended periods and that are housed overnight in temporary enclosures in rice paddies. A total of 115 stationary and 22 moving flock farmers were interviewed in 2007 in the Mekong Delta of Viet Nam. Moving duck flocks are larger than stationary flocks, which is indicative of their more commercial production. Moving flock farmers apparently are more aware of HPAI risks than stationary flock farmers, as their flocks are more likely fully vaccinated and have less contact with chickens during scavenging. On the other hand, the spread of HPAI virus between birds might be promoted by moving duck flocks as they repeatedly use transport vehicles and numerous rice paddies for scavenging and are often visited by hatchery owners in the field for purchasing duck eggs. In addition, long distances travelled by moving duck flocks might also result in widespread dissemination of HPAI virus. Further studies are necessary to describe HPAI prevalence and travel patterns of moving duck flocks and to explore the moving duck flock network in detail.

An epidemiological study of avian influenza A (H5) virus in nomadic ducks and their raising practices in northeastern Bangladesh, 2011‐2012

“…Nomadic duck raising practices were characterized by movement outside of the owners’ home villages, transporting duck flocks on foot and marketing ducks and their eggs. This could contribute to regional spreading of avian influenza A viruses when nomadic ducks are actively shedding virus . The practices and levels of infection reported in this study may help inform modeling efforts describing the potential bidirectional spread of avian influenza A viruses between wild waterfowl, nomadic ducks, and domestic poultry in Bangladesh …”

“…Highly pathogenic avian influenza A (H5) viruses in domestic ducks may result in asymptomatic, subclinical, or clinical infections, and asymptomatic ducks often shed the viruses through feces and respiratory droplets . In many Asian countries, farmers herd scavenging ducks from one feeding ground to another through the year and these practices can contribute to the spread of influenza A (H5) viruses . Allowing contact between domestic ducks, wild waterfowl and other poultry and animal species, poses risks for spreading of influenza A (H5) viruses …”

Highly Pathogenic Avian Influenza Virus A/H5N1 Infection in Vaccinated Meat Duck Flocks in the Mekong Delta of Vietnam

“…Ducks are very important as a reservoir species for HPAI H5N1 viruses, as infected ducks often remain asymptomatic (Kim et al., ; Cha et al., ). In the Mekong Delta of Vietnam, duck farming systems typically involve free‐range rice grazing, a practice that has been associated with transmission of HPAI H5N1 infection (Minh et al., ; Henning et al., ).…”

Landscape attributes driving avian influenza virus circulation in the Lake Alaotra region of Madagascar

“…Second, ducks and geese may have had greater exposure to AIV due to differences in flock management. Indeed, while chickens stay in the backyard or in close vicinity to houses, ducks and geese in Madagascar are brought to rice fields where they feed on snails and crop residuals, movements that may enhance their probability of contact with infected wild or domestic birds (Henning et al, 2013).…”