Spread of HPAIV H5N1 from south china agro-ecosystems through wild birds migration: a multidisciplinary approach

Agricultural intensification in South China has increased densities of domestic ducks raised on intensively irrigated paddy fields, an important factor of the persistence of H5N1 highly pathogenic avian influenza virus (AIV) persistence. Some major wild bird congregation wetlands in South China have been partly turned into paddy fields where millions of free-grazing domestic ducks are raised. This may facilitate the contact and the circulation of AIV between poultry and wild waterbirds, reservoir of AIV. In this study we combined epidemiological, ecological, agricultural and virological data to investigate the potential role of wild birds in the long-distance spread of H5N1 HPAIV virus from South China. We used new technologies such as satellite-tracking of Wild birds, GPS tracking of domestic ducks, remote sensing of irrigated paddy fields, phylogenetic analysis of H5N1 strains isolated in wild and domestic birds. Our results show that: (i) wild birds share paddy fields, wetlands and AIV strains with free-grazing domestic ducks when wintering in South China, (ii) spring migration of wild birds from South China match spatially and temporally with the long-distance spread of HPAIV H5N1, (iii) epidemiological and virological data support the role of wild birds in this long-distance spread. This multidisciplinary study brings together different elements in favour of the long distance spread of H5N1 AIV from South China agro-ecosystems through wild ducks migration. (Texte intégral

Wild birds in south china agro-ecosystems and long-distance spread of H5N1

Agricultural intensification in South China has increased densities of domestic ducks raised on intensively irrigated paddy fields, an important factor in the persistence of H5N1 highly pathogenic avian influenza virus (HPAIV). Some major wild bird congregating wetlands in South China have been partly turned into paddy fields where millions of free-grazing domestic ducks are raised. This may facilitate the contact and the circulation of avian influenza virus (AIV) between domestic and wild waterfowl, the latter a reservoir of AIV. In this study we combined epidemiological, ecological, agricultural and virological data to investigate the potential role of wild birds in the long-distance spread of H5N1 HPAIV virus from South China. We used new technologies such as satellite-tracking of wild birds, GPS tracking of domestic ducks, remote sensing of irrigated paddy fields, and phylogenetic analysis of H5N1 strains isolated in wild and domestic birds. Our results show that: (i) wild birds share paddy fields, wetlands and AIV strains with free-grazing domestic ducks when wintering in South China, (ii) spring migration of wild birds from South China match spatially and temporally with the longdistance spread of HPAIV H5N1, (iii) epidemiological and virological data support the role of wild birds in this long-distance spread. This study provides evidence of the role of wild birds in the long distance spread of H5N1 AIV from South China agro-ecosystems. It also raises the question of the role of wild birds in the evolution of low and highly pathogenic strains as they introduce new AIV strains in these agro-ecosystems. (Résumé d'auteur

Poultry population dynamics and mortality risks in smallholder farms of the Mekong river delta region

Background: Poultry farming is widely practiced by rural households in Vietnam and the vast majority of domestic birds are kept on small household farms. However, smallholder poultry production is constrained by several issues such as infectious diseases, including avian influenza viruses whose circulation remains a threat to public health. This observational study describes the demographic structure and dynamics of small-scale poultry farms of the Mekong river delta region. Method: Fifty three farms were monitored over a 20-month period, with farm sizes, species, age, arrival/departure of poultry, and farm management practices recorded monthly. Results: Median flock population sizes were 16 for chickens (IQR: 10–40), 32 for ducks (IQR: 18–101) and 11 for Muscovy ducks (IQR: 7–18); farm size distributions for the three species were heavily right-skewed. Muscovy ducks were kept for long periods and outdoors, while chickens and ducks were farmed indoors or in pens. Ducks had a markedly higher removal rate (broilers: 0.14/week; layer/breeders: 0.05/week) than chickens and Muscovy ducks (broilers: 0.07/week; layer/breeders: 0.01–0.02/week) and a higher degree of specialization resulting in a substantially shorter life span. The rate of mortality due to disease did not differ much among species, with birds being less likely to die from disease at older ages, but frequency of disease symptoms differed by species. Time series of disease-associated mortality were correlated with population size for Muscovy ducks (Kendall's coefficient τ = 0.49, p-value < 0.01) and with frequency of outdoor grazing for ducks (τ = 0.33, p-value = 0.05). Conclusion: The study highlights some challenges to disease control in small-scale multispecies poultry farms. The rate of interspecific contact and overlap between flocks of different ages is high, making small-scale farms a suitable environment for pathogens circulation. Muscovy ducks are farmed outdoors with little investment in biosecurity and few inter-farm movements. Ducks and chickens are more at-risk of introduction of pathogens through movements of birds from one farm to another. Ducks are farmed in large flocks with high turnover and, as a result, are more vulnerable to disease spread and require a higher vaccination coverage to maintain herd immunity

Evaluation of agro-industrial by-products as protein sources for duck production in the Mekong Delta of Vietnam

This thesis is based on four studies to determine the nutritive value and ileal and total tract amino acid digestibility of agro-industrial by-products, and the effects of inclusion of these by-products in diets on the biological performance of growing crossbred Muscovy and common ducks in the Mekong Delta, Vietnam. The results show that brewery waste (BW) was characterised by high protein content,good balance of essential amino acids, but high crude fibre content. The best growth performance was observed when 50% of the concentrate was replaced by BW for both Muscovy and common ducks. The crossbred Muscovies had better performance and gave higher economic benefit than the local Muscovies, and common ducks gave the lowest profit. BW could be offered either in mixed or separate feeding systems without any effects on performance and carcass yield (Paper I and II). Soya waste (SW) and ensiled shrimp waste (ESW) are good protein sources, but low in dry matter (DM) and methionine content (SW) and high in chitin content (ESW). The best performance in terms of growth rate and carcass quality was found with replacement of up to 60% of soybean meal by SW, and only 20% of fish meal by ESW, which gave the lowest feed costs (Paper III). The inclusion of ESW in diets for adult crossbred common ducks resulted in a linear decrease of the apparent total tract digestibility of dry matter, organic matter, ether extract, N free extract and N retention with increasing levels of ESW. The digestibility of individual amino acids followed a similar pattern to the nutrient digestibility. The apparent total tract digestibility of most individual amino acids was higher than the apparent ileal value (Paper IV). It can be concluded that from nutritive and economic apects the three agro-industrial byproducts evaluated have proven to be acceptable feed ingredients in duck diets. Replacement up to levels of 20% (ESW), 50% (BW) and 60% (SW) of fish meal, concentrate and soybean meal, respectively, in diets for growing crossbred ducks can be recommended under the conditions of the Mekong Delta

Distribution of contaminants in the environment and wildlife habitat use: a case study with lead and waterfowl on the Upper Texas Coast

The magnitude and distribution of lead contamination remain unknown in wetland systems. Anthropogenic deposition of lead may be contributing to negative population-level effects in waterfowl and other organisms that depend on dynamic wetland habitats, particularly if they are unable to detect and differentiate levels of environmental contamination by lead. Detection of lead and behavioral response to elevated lead levels by waterfowl is poorly understood, but necessary to characterize the risk of lead-contaminated habitats. We measured the relationship between lead contamination of wetland soils and habitat use by mottled ducks (Anas fulvigula) on the Upper Texas Coast, USA. Mottled ducks have historically experienced disproportionate negative effects from lead exposure, and exhibit a unique nonmigratory life history that increases risk of exposure when inhabiting contaminated areas. We used spatial interpolation to estimate lead in wetland soils of the Texas Chenier Plain National Wildlife Refuge Complex. Soil lead levels varied across the refuge complex (0.01–1085.51 ppm), but greater lead concentrations frequently corresponded to areas with high densities of transmittered mottled ducks. We used soil lead concentration data and MaxENT species distribution models to quantify relationships among various habitat factors and locations of mottled ducks. Use of habitats with greater lead concentration increased during years of a major disturbance. Because mottled ducks use habitats with high concentrations of lead during periods of stress, have greater risk of exposure following major disturbance to the coastal marsh system, and no innate mechanism for avoiding the threat of lead exposure, we suggest the potential presence of an ecological trap of quality habitat that warrants further quantification at a population scale for mottled ducks

Trade patterns facilitating highly pathogenic avian influenza virus dissemination in the free-grazing layer duck system in Vietnam

Highly pathogenic avian influenza (HPAI) viruses continue to threaten smallholder poultry producers in several South‐east Asian countries, including Vietnam. In particular, the free‐grazing duck system has been repeatedly highlighted as a major risk factor for HPAI outbreaks. Free‐grazing ducks, which scavenge on rice paddies after the harvest, account for a large proportion of the duck population in Vietnam and the wider South‐east Asian region. However, the structure and dynamics of the free‐grazing duck production from farm to consumption has not been described for Vietnam. In this study, we used a value chain approach to provide a complete picture of the actors involved in the production and marketing of free‐grazing duck eggs and spent layer ducks, as well as to investigate the governance structure of this food system. Group interviews and key informant interviews were conducted in two provinces located in the Mekong River Delta (MRD) and the Red River Delta (RRD). The results presented here highlight similarities and differences in farming and trade practices between the two provinces. The trade of spent layer ducks involved large volumes of live ducks being sent to China and Cambodia for consumption, generating a substantial risk of transboundary spread of pathogens, including HPAI viruses. We describe the major role of “duck yards”, which act as hubs in the northbound trade of spent layer ducks. These yards should be considered as essential links in the value chain of spent layer ducks when considering HPAI surveillance and control. The veterinary authorities are only marginally involved in the value chain activities, and their influence could be strengthened by increasing surveillance activities for instance in duck yards. Last, we discuss the dynamics of the duck value chain and further implications for future HPAI management policies

Wood Duck Investigations W-118-R-4-5-6 Final Report

W-118-R-4-5-6 (Final Report); issued November 20, 1998; Study I: Aerial helicopter surveys of breeding wood ducks in bottomland forest.Report issued on: November 20, 1998INHS Technical Report prepared for Illinois Department of Natural Resource

Utilization of Palm Kernel Cake in Muscovy Ducks

Four experiments were conducted on Muscovy ducks to evaluate their utilization, performance and nutrient digestibility when offered diets containing different levels of palm kernel cake (PKC). In the first experiment, two types of PKC (solvent and expeller extracted) were force-fed to male and female ducks 7 weeks of age and the nutrient digestibility, true metabolizable energy and true amino acid digestibility were determined. There was no significant (p>0.05) effect on the type of PKC used on crude protein (CP), ether extract (EE), metabolizable energy (ME) and amino acid (AA) digestibility, except for those of dry matter (DM) and neutral detergent fibre (NDF) which was higher in solvent extracted compared to expeller extracted PKC. It was found that the ducks utilized about 47% of the gross energy in PKC. The average apparent metabolizable energy value of PKC for Muscovy ducks was obtained to be 1870 kcal/kg, which was rather higher than those reported in broiler chickens. The performance of male and female Muscovy ducks when fed diets containing 15% and 35% levels of PKC were investigated. The results indicated that inclusion of up to 15% of PKC in growing diet for ducks did not depress growth nor feed conversion ratio (FCR) at any significant degree. Given the low cost of PKC, such usage is likely to be economic, depending, to some extent, on cost of added oil. At this level no negative effect in faecal consistency nor carcass fatness were observed. As PKC level increased up to 35%, the ducks ate more feed and as a result had poorer FCR. The explanation for the poorer FCR could be related to the decline in the energy and protein digestibility when ducks were fed at higher PKC level as compared to the control diet. It could be suggested that addition of oil to PKC based diet may improve the palatability and thus the feed intake and the performance of the ducks. Differences in the feed efficiency and nutrient digestibility between Muscovy ducks and broiler chickens were found when PKC was included up to 25% in the diet. Feeding up to 25% level of PKC to ducks was not associated in any detrimental effects on the performance and FCR. However, FCR was depressed when PKC was added at 25% level to broiler grower diet. The ME value was found to be higher in ducks than in chickens. This indicates that the ME value for chickens cannot be applied to ducks. The digestibility of NDF was found to be higher for ducks than for chickens and this could be due to the higher hemicellulose digestibility for ducks than for chickens