Identifying Live Bird Markets with the Potential to Act as Reservoirs of Avian Influenza A (H5N1) Virus: A Survey in Northern Viet Nam and Cambodia

Abstract

Wet markets are common in many parts of the world and may promote the emergence, spread and maintenance of livestock pathogens, including zoonoses. A survey was conducted in order to assess the potential of Vietnamese and Cambodian live bird markets (LBMs) to sustain circulation of highly pathogenic avian influenza virus subtype H5N1 (HPAIV H5N1). Thirty Vietnamese and 8 Cambodian LBMs were visited, and structured interviews were conducted with the market managers and 561 Vietnamese and 84 Cambodian traders. Multivariate and cluster analysis were used to construct a typology of traders based on their poultry management practices. As a result of those practices and large poultry surplus (unsold poultry reoffered for sale the following day), some poultry traders were shown to promote conditions favorable for perpetuating HPAIV H5N1 in LBMs. More than 80% of these traders operated in LBMs located in the most densely populated areas, Ha Noi and Phnom Penh. The profiles of sellers operating at a given LBM could be reliably predicted using basic information about the location and type of market. Consequently, LBMs with the largest combination of risk factors for becoming virus reservoirs could be easily identified, potentially allowing control strategies to be appropriately targeted. These findings are of particular relevance to resource-scarce settings with extensively developed LBM systems, commonly found in South-East Asia.

Interventions for avian influenza A (H5N1) risk management in live bird market networks

“…Traders who might promote conditions favorable for sustaining HPAIV H5N1 in LBMs (20) were predominant in 13 of the Hanoi LBMs included in the survey (solid triangle in Fig. 1).…”

“…1). In contrast, traders operating in the Hanoi hub, and all traders operating in Bac Giang markets, kept their poultry in LBMs for only a short period, so virus maintenance was unlikely (20). Most of these 13 Hanoi markets with the potential to act as viral reservoirs were either isolated from or connected only weakly to the Hanoi network (five isolates, four peripheral nodes, and four nodes with medium connectivity).…”

“…Bac Giang traders kept poultry for only a short period in LBMs and thus were unlikely to permit virus perpetuation in these LBMs (20). However, a trader whose poultry was infectious or whose equipment was contaminated might potentially transfer viruses to the market environment.…”

“…In the absence of effective disinfection, traders may then act as a major source of exposure to infection for farms (13)(14)(15)(16)(17)(18). Once contaminated, some LBMs may even act as viral reservoirs, depending on the poultry management practices of their traders (19,20). Such markets provide a continuous source of infection for the poultry sector.…”

Links Among Human Health, Animal Health, and Ecosystem Health

“…Small-scale animal agriculture activities may involve deforestation to create animal pasture areas as well as to compensate for movements of people and animals from more rural areas to rapidly growing cities. As a result of these rapid transitions, people in large cities may have close contact with animals through live-animal (wet) markets (25) or because other residents are raising small-scale poultry or ruminants inside or close to their households, creating a low-biosecurity setting for both humans and animals.…”