Risk Factors of Highly Pathogenic Avian Influenza H5N1 Occurrence at the Village and Farm Levels in the Red River Delta Region in Vietnam

Abstract

of poultry movements and trading activities. In particular, our models found that higher number of 36 broiler flocks in the village increased the risk (OR = 1.49, 95% CI: 1.12-1.96), as well as the village 37 having at least one poultry trader (OR =11.53, 95% CI: 1.34-98.86). To a lesser extent, in one of our 2 38 models, we also identified that increased density of ponds and streams, commonly used for waterfowl 39 production, and greater number of duck flocks in the village also increased the risk. The higher 40 percentage of households keeping poultry, as an indicator of households keeping backyard poultry in 41 our study population, was a protective factor (OR= 0.95,. At the farm level, 3 risk 42 factors at the 5% level of type I error were identified by univariate analysis: a greater total number of 43 birds (P=0.006), and increase in the number of flocks having access to water (p=0.027, and a greater 44 number of broiler flocks in the farm (P=0.049). Effect of vaccination implementation (date and doses) 45 was difficult to investigate due to a poor recording system. Some protective or risk factors with limited 46 effect may not have been identified due to our limited sample size. Nevertheless, our results provide a 47 better understanding of local transmission mechanisms of HPAI H5N1 in one province of the Red 48 River Delta region in Vietnam and highlight the need to reduce at-risk trading and production 49 practices. 50

Spatio-Temporal Occurrence Modeling of Highly Pathogenic Avian Influenza Subtype H5N1: A Case Study in the Red River Delta, Vietnam

“…However, this mechanism has not been fully understood in a scientific sense [2,3]. In Vietnam, the occurrence and spread of HPAI H5N1 were thought to be associated with either increases in poultry production, trade and movement of live poultry before, during and after Tet (the national lunar new year celebration), or the expansion of free-range duck farming where domestic ducks came into contact with rice paddy fields during the rice crop harvest season [4,5]. However, temporal distribution of the disease in Thailand showed this same trend, even though movement of poultry in high-risk areas was restricted [6,7].…”

Evaluation of the vaccination efficacy against H5N1 in domestic poultry in the Red River Delta in Vietnam

“…Those communes also provided a good representation of the poultry production systems of the Red River Delta area, with Bac Giang province representative of the agricultural practices in the Delta region [12] and Ha Tay province being the main poultry production area in Northern Vietnam, especially for breeders [1]. One-day-old chickens and ducklings from this province are sent to most of the Northern provinces [1].…”

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

“…Here, poultry traders can mix and potentially transfer the virus either by trading infected poultry or by sharing contaminated equipment. 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).…”