The Yamabe flow on asymptotically Euclidean manifolds with nonpositive Yamabe constant

We study the Yamabe flow on asymptotically flat manifolds with non-positive Yamabe constant $Y\leq 0$. Previous work by the second and third named authors \cite{ChenWang} showed that while the Yamabe flow always converges in a global weighted sense when $Y>0$, the flow must diverge when $Y\leq 0$. We show here in the $Y\leq 0$ case however that after suitable rescalings, the Yamabe flow starting from any asymptotically flat manifold must converge to the unique positive function which solves the Yamabe problem on a compactification of the original manifold.Comment: 24 page

Using a value chain framework for food safety assessment of broiler and indigenous chicken meat systems of Nairobi

Purpose: Research on livestock food systems in developing countries remains limited, yet this context needs to be understood to investigate the epidemiology of zoonoses. The aim of this study was to use a value chain framework to characterize the broiler and indigenous chicken meat systems of Nairobi and their food safety risks. Methods: Using such a framework for food safety characterisation at system level is novel and has significant potential in developing countries. Data collection involved 18 focus group discussions and 236 interviews with various poultry meat value chain stakeholders in Nairobi. Analysis included chain mapping and identification of governance and food safety challenges. Results: The study identified 10 chain profiles, characterising the broiler and indigenous chicken systems, and production-retailing continuum. Food safety risks identified were related to lack of biosecurity, cold chain and access to water, poor cleaning and hygiene practices, consumption of sick animals, significant environmental contamination of by-products, and lack of inspection at farm slaughter. Large companies dominated the governance of the broiler system through the control of day-old chick production. Overall government control was relatively weak leading to minimal official regulatory enforcement. Large companies and brokers were identified as dominant groups in market information dissemination and price setting. No dominant group was identified for indigenous chicken profiles, farming being at household level for local consumption, with quasi non-existent regulations. Lack of industry association was system-wide, creating a barrier for access to capital. Other system barriers included lack of space and expertise, leading to poor infrastructure and limited ability to implement effective hygienic measures. Conclusions and relevance: Optimal food safety and disease control strategies should consider the structure of the poultry meat system and stakeholder interactions to ensure effective programmes. This study provides a new perspective for epidemiologists and public health officers to address food safety risks in full understanding of the food system context

Identification of production challenges and benefits using value chain mapping of egg food systems in Nairobi, Kenya

Commercial layer and indigenous chicken farming in Nairobi and associated activities in the egg value chains are a source of livelihood for urban families. A value chain mapping framework was used to describe types of inputs and outputs from chicken farms, challenges faced by producers and their disease control strategies. Commercial layer farms were defined as farms keeping exotic breeds of chicken, whereas indigenous chicken farms kept different cross breeds of indigenous chicken. Four focus group discussions were held with producers of these chickens in peri-urban area: Dagoretti, and one informal settlement: Kibera. Qualitative data were collected on interactions between farmers, sources of farm inputs and buyers of poultry products, simple ranking of production challenges, farmers' perception on diseases affecting chicken and strategies for management of sick chicken and waste products. Value chain profiles were drawn showing sources of inputs and channels for distribution of chicken products. Production challenges and chicken disease management strategies were presented as qualitative summaries. Commercial layer farms in Dagoretti kept an average of 250 chickens (range 50–500); while flock sizes in Kibera were 12 chickens (range 5–20). Farms keeping indigenous chicken had an average of 23 chickens (range 8–40) in Dagoretti, and 10 chickens (range 5–16) in Kibera. Commercial layer farms in Dagoretti obtained chicks from distributors of commercial hatcheries, but farms in Kibera obtained chicks from hawkers who in turn sourced them from distributors of commercial hatcheries. Indigenous chicken farms from Dagoretti relied on natural hatching of fertilised eggs, but indigenous chicken farms in Kibera obtained chicks from their social connection with communities living in rural areas. Outlets for eggs from commercial layer farms included local shops, brokers, restaurants and hawkers, while eggs from indigenous chicken farms were sold to neighbours and restaurants. Sieved chicken manure from Dagoretti area was fed to dairy cattle; whereas non-sieved manure was used as fertilizer on crops. Production challenges included poor feed quality, lack of space for expansion, insecurity, occurrence of diseases and lack of sources of information on chicken management. In Kibera, sick and dead chickens were slaughtered and consumed by households; this practice was not reported in Dagoretti. The chicken layer systems contribute to food security of urban households, yet they have vulnerabilities and deficiencies with regard to disease management and food safety that need to be addressed with support on research and extension

The broiler meat system in Nairobi, Kenya: using a value chain framework to understand animal and product flows, governance and sanitary risks

Livestock food systems play key subsistence and income generation roles in low to middle income countries and are important networks for zoonotic disease transmission. The aim of this study was to use a value chain framework to characterize the broiler chicken meat system of Nairobi, its governance and sanitary risks. A total of 4 focus groups and 8 key informant interviews were used to collect cross-sectional data from: small-scale broiler farmers in selected Nairobi peri-urban and informal settlement areas; medium to large integrated broiler production companies; traders and meat inspectors in live chicken and chicken meat markets in Nairobi. Qualitative data were collected on types of people operating in the system, their interactions, sanitary measures in place, sourcing and selling of broiler chickens and products. Framework analysis was used to identify governance themes and risky sanitary practices present in the system. One large company was identified to supply 60% of Nairobi’s day-old chicks to farmers, mainly through agrovet shops. Broiler meat products from integrated companies were sold in high-end retailers whereas their low value products were channelled through independent traders to consumers in informal settlements. Peri-urban small-scale farmers reported to slaughter the broilers on the farm and to sell carcasses to retailers (hotels and butcheries mainly) through brokers (80%), while farmers in the informal settlement reported to sell their broilers live to retailers (butcheries, hotels and hawkers mainly) directly. Broiler heads and legs were sold in informal settlements via roadside vendors. Sanitary risks identified were related to lack of biosecurity, cold chain and access to water, poor hygiene practices, lack of inspection at farm slaughter and limited health inspection in markets. Large companies dominated the governance of the broiler system through the control of day-old chick production. Overall government control was described as relatively weak leading to minimal official regulatory enforcement. Large companies and brokers were identified as dominant groups in market information dissemination and price setting. Lack of farmer association was found to be system-wide and to limit market access. Other system barriers included lack of space and expertise, leading to poor infrastructure and limited ability to implement effective hygienic measures. This study highlights significant structural differences between different broiler chains and inequalities in product quality and market access across the system. It provides a foundation for food safety assessments, disease control programmes and informs policy-making for the inclusive growth of this fast-evolving sector

Genetic diversity and relationships of the liver fluke Fasciola hepatica (Trematoda) with native and introduced definitive and intermediate hosts

Fasciolosis is a worldwide spread parasitosis mainly caused by the trematode Fasciola hepatica. This disease is particularly important for public health in tropical regions, but it can also affect the economies of many developed countries due to large infections in domestic animals. Although several studies have tried to understand the transmission by studying the prevalence of different host species, only a few have used population genetic approaches to understand the links between domestic and wildlife infections. Here, we present the results of such genetic approach combined with classical parasitological data (prevalence and intensity) by studying domestic and wild definitive hosts from Camargue (southern France) where fasciolosis is considered as a problem. We found 60% of domestic hosts (cattle) infected with F. hepatica but lower values in wild hosts (nutria, 19%; wild boars, 4.5%). We explored nine variable microsatellite loci for 1,148 adult flukes recovered from four different populations (non-treated cattle, treated cattle, nutria and wild boars). Populations from the four groups differed, though we found a number of migrants particularly non-treated cattle and nutria. Overall, we detected 729 different multilocus genotypes (from 783 completely genotyped individuals) and only 46 genotypes repeated across samples. Finally, we experimentally infected native and introduced intermediate snail hosts to explore their compatibility with F. hepatica and assess the risks of fasciolosis expansion in the region. The introduced species Galba truncatula and Pseudosuccinea columella attained the higher values of overall compatibility in relation to the European species. However, concerning the origin, sympatric combinations of G. truncatula were more compatible (higher prevalence, intensity and survival) than the allopatric tested. According to our results, we should note that the assessment of epidemiological risks cannot be limited to a single host–parasite system, but should focus on understanding the diversity of hosts in the heterogeneous environment through space and time.Fil: Vázquez, Antonio A.. Instituto de Medicina Tropical “Pedro Kourí”; Cuba. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; FranciaFil: Sabourin, Emeline. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Alda, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Zoología de Invertebrados I; Argentina. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Leroy, Clémentine. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Leray, Carole. Institut de Recherche de la Tour du Valat; FranciaFil: Carron, Eric. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Mulero, Stephen. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; Francia. Université de Perpignan Via Domitia; FranciaFil: Caty, Céline. Institut de Recherche de la Tour du Valat; FranciaFil: Hasfia, Sarah. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Boisseau, Michel. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Saugné, Lucas. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Pineau, Olivier. Institut de Recherche de la Tour du Valat; FranciaFil: Blanchon, Thomas. Institut de Recherche de la Tour du Valat; FranciaFil: Alba, Annia. Instituto de Medicina Tropical “Pedro Kourí”; Cuba. Università di Corsica Pasquale Paoli; FranciaFil: Faugère, Dominique. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; FranciaFil: Vittecoq, Marion. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; Francia. Institut de Recherche de la Tour du Valat; FranciaFil: Hurtrez Boussès, Sylvie. Centre National de la Recherche Scientifique; Francia. Université Montpellier II; Franci

Value chain analysis for products and by-products of egg laying birds in peri-urban areas of Nairobi City

Livestock keeping in urban areas is a source of livelihoods for poor urban families, but it also poses public health challenges. Purpose This included mapping of value chains for products from commercial layers (CL) and indigenous layers (IL) kept in peri-urban areas of Nairobi City, prioritization of barriers to entry into layer farming and assessment of disease and food safety management. Methods Data on interaction between people and poultry products, barriers to entry and disease and food safety management were collected through key informant interviews, focus group discussions (FGD) and administration of questionnaires. Twelve FGD were conducted and 250 questionnaires administered to individual farmers. Additional data was obtained from retailers of poultry products and government officers. Results The CL farms kept between 100 and 1,000 birds per flock while for IL farms, flock sizes were between 1 and 50 birds. CL farms obtained day old chicks from distributors of large and small-scale hatcheries and from hawkers, while IL farms obtained chicks from small-scale hatcheries and neighbouring farms. Products from these farms were eggs, spent hens and poultry manure. Eggs from CL farms were sold to shops, consumers and hawkers, while those from IL farms were sold to neighbours, bakeries and restaurants, while some were consumed at home. Spent layers were sold to brokers, neighbours and households. Poultry manure was used on crop farms and as feed for dairy cattle. The barriers to entry included poor quality feeds, poultry diseases, seasonality and scarcity of water and land. The diseases included coccidiosis, Newcastle disease and respiratory problems and these were managed by personnel from “agrovets”, while in slums sick birds were slaughtered and consumed. Furthermore, hawkers and personnel from restaurants and shops were reported to lack training in food safety. Conclusion and relevance Risk for zoonoses exists along poultry value chains and hence with increasing urbanization in developing countries, investigation of food systems in cities should adopt this framework to better understand public health risks

Planning for changes in complex food systems: Value chain mapping of different poultry production systems in Nairobi as a first step to food safety, livelihood improvement and micronutrient supply assessments

Introduction: Research on livestock food systems in developing countries remains limited yet these systems are undergoing rapid and ongoing changes. Poultry meat in Nairobi is a good case study to investigate the changes that result from increasing demand for animal protein1, in particular how different systems affect the supply of macro and micronutrients, livelihood improvement and food safety risks. The aim of the current study was to map the broiler and indigenous chicken meat value chains of Nairobi to provide a thorough context (milieu) for future food safety and socio-economic assessments of the wide poultry meat system. Methods: Focus groups and individual questionnaires were used to collect data from: - Broiler and indigenous farmers (in Dagoretti, reflecting peri-urban chains, and Kibera informal settlement, for urban chains); - Retailers in Viwandani, Korogocho (informal settlements), and Dagoretti; - Three larger broiler production companies; - Livestock production and public health officers, meat inspectors, city council, National Environment Management Authority, and a village chief. The following data were collected for each chain and entered in templates: - Categories of farms, retailers, products and consumers; production practices and performance; relative flows of birds and products, their sources and seasonality; market outlets; regulations enforcement and institutional context; interactions and involvement of people in the chains’ nodes; biosecurity measures. Analysis allowed detailed characterisation and graphical representation of the food system. Within the system the following “chain profiles” were identified: 1) peri-urban and 2) urban broilers; 3) peri-urban and 4) urban indigenous chickens; 5) large and 6) medium integrated companies; 7) live and 8) meat poultry markets; 9) main poultry chains in each sub-county; 10) characterisation of poultry retailer types. Each profile has a distinct set of flows, interactions, market potentials, risk practices, production and distribution characteristics, useful for food safety, food security and governance assessments. Findings and interpretation: Within the poultry meat food system the chains in urban areas had fewer intermediaries and smaller geographic span than those in peri-urban areas – overall they were “shorter”. The limited space in urban areas appeared to reduce flock size and hence increase one-off transactions. Use of brokers in peri-urban chains made transport of meat, rather than birds, more practical. Greatest homogeneity was seen in the chains with commercial broiler chickens (birds for meat production) with one large company supplying 60% of Nairobi’s day-old chicks to small-scale farmers. A small number of larger companies supply broiler chicken meat to high-end retailers across Nairobi, yet there are many more small-scale broiler farmers who sell birds close to their farms, or in Nairobi markets. Indigenous breed chickens are kept in backyard farming systems and are kept for home or local consumption. Birds are also sourced from remote areas of Kenya. Different meat products reach different consumers, based on their value. The lowest value products are heads and legs from broilers of large-scale and peri-urban small farms, which are sold in informal settlements via roadside vendors. The description of the chicken meat food system provides the context for further food safety and food security analysis

Campylobacter, a zoonotic pathogen of global importance: prevalence and risk factors in the fast-evolving chicken meat system of Nairobi, Kenya

Campylobacteriosis is a leading foodborne zoonosis worldwide, and is frequently associated with handling and consumption of poultry meat. Various studies indicate that Campylobacter causes a substantial human disease burden in low to middle-income countries, but data regarding the organism's epidemiology in countries like Kenya are scarce. In sub-Saharan Africa, 3.8 million deaths of children under-5 years of age are reported annually. Of those, 25% are caused by diarrheal diseases, and Campylobacter is one of the most frequently isolated bacteria from diarrheic children. With the growth of urban conglomerates, such as Kenya's capital, Nairobi, changes in diets, food production systems, and retailing dynamics, it is likely that exposure and susceptibility to this pathogen will change. Therefore, the importance of Campylobacter disease burden in Kenya may increase further. The objectives of this study were: 1) to determine the prevalence of Campylobacter spp. in Nairobi's small-scale chicken farms and meat retailers, and 2) to identify potential risk factors associated with its presence in those sites. The prevalence data provides the first detailed baseline for this pathogen in the urban Kenyan context. The risk factors provide context-specific insights for disease managers. A cross-sectional study of broiler, indigenous chicken farms, and chicken meat retailers, was conducted in a peri-urban, low to middle-income area (Dagoretti), and a very-low income informal settlement (Kibera) of Nairobi. Chicken faeces were collected using one pair of boot socks per farm, and 3 raw chicken meat samples were purchased per retailer. Samples were cultured for viable Campylobacter spp. using mCCDA, followed by blood agar plates in aerobic/microaerobic conditions for prevalence calculations. A questionnaire-based survey on sanitary, sourcing and selling practices was conducted at each site for risk factor identification using logistic regression analyses. A total of 171 farm premises and 53 retailers were sampled and interviewed. The prevalence results for Campylobacter spp. were between 33 to 44% for broiler and indigenous chicken farms, 60% and 64% for retailers, in Dagoretti and Kibera, respectively. Univariable logistic regression showed an association between Campylobacter spp. presence and the easiness of cleaning the display material used by the retailer. Restricting access to the flock was also associated with the pathogen's presence. Multivariable logistic regression identified the selling of defrosted meat as a retailer risk factor (OR: 4.69; 95% CI: 1.31-19.97), calling for more investigation of the reported repetitive freezing-thawing processes and cold chain improvement options. At the farm-level, having a pen floor of material not easy to clean was found to increase the risk (OR: 2.31; 95%CI: 1.06-5.37). The relatively high prevalence of Campylobacter spp. across different areas and value chain nodes indicates a clear human exposure risk. The open nature of both small-scale broiler and indigenous chicken production practices with low biosecurity, hygiene and informal transactions, likely plays a role in this. While gradual improvement of farm biosecurity is recommended, risk factors identified suggest that consumer education and enforcement of basic food safety principles at the retailer end of the food continuum represent key targets for risk reduction in informal settings

A Multicenter Randomized Controlled Trial of Zephyr Endobronchial Valve Treatment in Heterogeneous Emphysema (TRANSFORM)

Rationale: Single-center randomized controlled trials of the Zephyr endobronchial valve (EBV) treatment have demonstrated benefit in severe heterogeneous emphysema. This is the first multicenter study evaluating this treatment approach. Objectives: To evaluate the efficacy and safety of Zephyr EBVs in patients with heterogeneous emphysema and absence of collateral ventilation. Methods: This was a prospective, multicenter 2:1 randomized controlled trial of EBVs plus standard of care or standard of care alone (SoC). Primary outcome at 3 months post-procedure was the percentage of subjects with FEV1 improvement from baseline of 12% or greater. Changes in FEV1, residual volume, 6-minute-walk distance, St. George's Respiratory Questionnaire score, and modified Medical Research Council score were assessed at 3 and 6 months, and target lobe volume reduction on chest computed tomography at 3 months. Measurements and Main Results: Ninety seven subjects were randomized toEBV(n = 65) or SoC(n = 32). At 3 months, 55.4% of EBV and 6.5% of SoC subjects had an FEV1 improvement of 12% or more (P <0.001). Improvements were maintained at 6 months: EBV 56.3% versus SoC 3.2% (P <0.001), with a mean +/- SD change in FEV1 at 6 months of 20.7 +/- 29.6% and -8.6 +/- 13.0%, respectively. A total of 89.8% of EBV subjects had target lobe volume reduction greater than or equal to 350 ml, mean 1.09 +/- 0.62 L (P <0.001). Between-group differences for changes at 6 months were statistically and clinically significant: Delta EBV-SoC for residual volume, -700 ml; 6-minute-walk distance, +78.7 m; St. George's Respiratory Questionnaire score, -6.5 points; modified Medical Research Council dyspnea score, -0.6 points; and BODE(body mass index, airflow obstruction, dyspnea, and exercise capacity) index, 21.8 points (all P <0.05). Pneumothorax was the most common adverse event, occurring in 19 of 65 (29.2%) of EBV subjects. Conclusions: EBV treatment in hyperinflated patients with heterogeneous emphysema without collateral ventilation resulted in clinically meaningful benefits in lung function, dyspnea, exercise tolerance, and quality of life, with an acceptable safety profile