Manure management and public health: Sanitary and socio-economic aspects among urban livestock-keepers in Cambodia

Spatial analysis of airborne bacterial concentrations and microbial communities in a large-scale commercial layer facility

This study investigated the spatial distribution patterns of airborne bacterial concentrations and microbial community structures in a modern commercial layer facility housing approximately 50,000 laying hens equipped with advanced environmental control systems. Air samples were systematically collected at 50 strategically distributed locations using a six-stage Andersen microbial air sampler, while environmental samples (dust, manure, intestinal contents) were characterized using 16S rRNA gene sequencing. Results demonstrated a distinct longitudinal gradient in airborne bacterial concentrations, progressively increasing from the air inlet (883±177 CFU/m³) to exhaust fans (12,650±813 CFU/m³), with a facility-wide mean concentration of 5,618±530 CFU/m³. Spatial analysis revealed significant bacterial concentration heterogeneity, with elevated bacterial loads (>8,000 CFU/m³) concentrated in central regions while peripheral areas maintained lower concentrations (<6,000 CFU/m³). Taxonomic profiling identified Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes as predominant phyla across all sample types, with significant compartment-specific distribution patterns: Firmicutes dominated intestinal samples (72.9 %), Proteobacteria and Bacteroidetes were enriched in posterior dust and manure samples, while Acinetobacter exhibited highest abundance (19.90 %) in anterior dust. Differential abundance analysis demonstrated significant enrichment of fecal-associated bacteria (particularly Bacteroides and Escherichia coli) in posterior sampling locations, establishing direct correlations between environmental parameters and microbial dissemination patterns. This comprehensive spatial-microbial analysis elucidates critical factors influencing bacterial dispersion within intensive poultry production environments, providing the empirical foundation for implementing concentration-based risk stratification management systems and targeted interventions to enhance biosecurity, minimize disease transmission, and optimize poultry health in commercial operations.

The last decade epidemiologic concern of drinking water contaminants of emerging concern (CECs) in Asian Countries: A scoping review

With the rapid industrialization and urbanization in Asian countries, the challenge of rising emerging contaminants in the environment, including the water cycle, has become more pronounced. Consequently, the presence of CECs in drinking water systems is inevitable due to their ubiquitous nature in aquatic environments. This scoping review aims to identify epidemiological concerns regarding drinking water CECs in Asian countries over the past decade by describing the types of assessed CECs, their associated health effects, and identifying gaps and future research prospects through a summary of relevant studies. Searches were conducted on PubMed and Scopus up to February 29, 2024. Included were epidemiological studies from the past 10 years (since January 2014) in Asian countries that assessed emerging contaminants in drinking water through direct measurement or analysis as factors. From an initial pool of 3198 results, 15 relevant studies were selected. These studies assessed various types of CECs, including disinfection byproducts (n = 10), endocrine disruptors (n = 2), pesticides (n = 2), and a protozoan pathogen (n = 1). The meticulous assessment of CECs and associated health outcomes in Asian epidemiological studies over the past decade has been deemed inadequate to address the wide range of ubiquitous CECs in drinking water and their potential health effects that have not yet been addressed. While not the sole objective, the primary aim of epidemiological studies is to inform policy decisions and increase awareness among the public and policymakers. Therefore, researchers in Asian countries, particularly in environmental and public health fields, should prioritize the development of research in this area by exploring more CECs type and associated health outcomes.

Plugging the leaks: antibiotic resistance at human-animal interfaces in low-resource settings

Antibiotic resistance is one of the greatest public health challenges of our time. International efforts to curb resistance have largely focused on drug development and limiting unnecessary antibiotic use. However, in areas where water, sanitation, and hygiene infrastructure is lacking, we propose that bacterial flow between humans and animals can exacerbate the emergence and spread of resistant pathogens. Here, we describe the consequences of poor environmental controls by comparing mobile resistance elements among Escherichia coli recovered from humans and meat in Cambodia, a middle-income country with substantial human-animal connectivity and unregulated antibiotic use. We identified identical mobile resistance elements and a conserved transposon region that were widely dispersed in both humans and animals, a phenomenon rarely observed in high-income settings. Our findings indicate that plugging leaks at human-animal interfaces should be a critical part of addressing antibiotic resistance in low- and especially middle-income countries.

Trends in the management of organic swine farm waste by composting: A systematic review

Pig farming contributes to the economic development of nations and supplies human food demand; however, it generates a large amount of organic waste which, if not managed properly, becomes a risk to the environment and human and animal health. Considering the relevance of composting and its usefulness for the use of waste, this study aimed to determine the global trends in the management of composting manure, mortality and other organic waste produced on pig farms over the last five years (2017-2022). Systematic search involved four databases: ISI Web of Science, Scopus, Ebsco and Scielo. Of the total findings, 56 articles were included in the review, further classified into 14 categories for their respective analysis: co-substrates/additives, microbial communities, antibiotic resistance, heavy metals, polycyclic aromatic hydrocarbons, microbiological/parasitological quality, phytopathogens, nitrogen transformation, bioinoculants, comparison/combination with other waste management techniques, factors affecting composting, swine mortality and plant growth promotion/phytotoxicity. The review exemplified the importance of swine mortality composting as an alternative for organic matter management in pig farms, considering that the process also includes manure, vegetable waste and wood chips, among others. Controlled factors throughout the process are a requirement to obtain a stable product with physicochemical and microbiological quality that complies with national and international regulations and that will be useful and safe for application on crops, ensuring environmental, animal, and human health.

Epidemiological connectivity between humans and animals across an urban landscape

Urbanization is predicted to be a key driver of disease emergence through human exposure to novel, animal-borne pathogens. However, while we suspect that urban landscapes are primed to expose people to novel animal-borne diseases, evidence for the mechanisms by which this occurs is lacking. To address this, we studied how bacterial genes are shared between wild animals, livestock, and humans (n = 1,428) across Nairobi, Kenya-one of the world's most rapidly developing cities. Applying a multilayer network framework, we show that low biodiversity (of both natural habitat and vertebrate wildlife communities), coupled with livestock management practices and more densely populated urban environments, promotes sharing of Escherichia coli-borne bacterial mobile genetic elements between animals and humans. These results provide empirical support for hypotheses linking resource provision, the biological simplification of urban landscapes, and human and livestock demography to urban dynamics of cross-species pathogen transmission at a landscape scale. Urban areas where high densities of people and livestock live in close association with synanthropes (species such as rodents that are more competent reservoirs for zoonotic pathogens) should be prioritized for disease surveillance and control.

Knowledge and Practices of Cypriot Bovine Farmers towards Effective and Safe Manure Management

Manure from bovine farms is commonly used as an organic fertiliser. However, if not properly managed, it can spread significant biological and chemical hazards, threatening both human and animal health. The effectiveness of risk control hugely relies on farmers' knowledge regarding safe manure management and on the application of suitable management practices. This study aims to evaluate the knowledge and practices of Cypriot bovine farmers towards safer manure management, from its generation to its final use, in line with the One Health approach. Factors affecting farmers' knowledge and applied practices are also investigated through a questionnaire survey. The questionnaire was developed and sent to all eligible bovine farmers in Cyprus (n = 353), and 30% (n = 105) of them returned the completed questionnaire. Results revealed there are some gaps in farmers' knowledge. The use of manure for fertilising crops dominated. Only half of the farmers stored manure in appropriate facilities, with 28.5% of them using a dedicated area with cement floors and 21.5% utilising leakproof tanks. The majority (65.7%) stored manure for more than three months before its use as a fertiliser in a dried form. In multiple regression analysis, education level and farming purpose were significant determinants of farmer knowledge. In conclusion, Cypriot farmers' knowledge must be reinforced to ensure proper manure management. The results highlight the importance of providing relevant training to farmers. Although the current practices partially decrease manure pathogens, interventions to promote the use of more effective treatment methods, such as biogas transformation and composting, would be beneficial.

A Transportation Network Optimization Model for Livestock Manure under Different Terrains Considering Economic and Environmental Benefits

Optimizing the path of livestock manure used for farmland is a hugely significant issue, which not only improves the utilization efficiency of manure but also reduces the cost of the transportation of manure. However, some factors such as different terrains and the density of surrounding farmland may lead to more difficulty in further improving the resource utilization rate. Therefore, this paper aims to establish a transport network optimization model for a complex livestock manure distribution scheme. Using basic information from livestock and poultry farms, cultivated land, water areas and forestland in Xinzhou District, Wuhan City, Hubei Province, the relationship between farmland and livestock farms is divided into farm-intensive and water-intensive farmland areas by using the Voronoi diagram subdivision method. Then, according to the supply–demand balance of manure and crop demand, an optimization model is proposed to discuss the manure return scheme for these two types of terrain. The results show that our model can help significantly improve manure utilization efficiency under different terrain situations, which is proposed comprehensively, considering the economic and environmental benefits.

Co-treatment with silicon and quicklime in pig manure application as a promising option of environmnetal management

Manure utilization is the most important current practices economically and, ecologically. The combined use of active forms of silicon together with other types of soil amendments or fertilizers has been shown to reduce P, N and K leaching from upper soil horizon or fixation, which positively affect crop production. The present study evaluated the performance of pig manure co-treated with quicklime (calcium oxide - CaO) and monosilicic acid (Si(OH)₄) as sources of nutrients for rice production conducted in greenhouse and field tests for the reduction of negative environmental effects through the soil-plant system. Results indicated that quicklime/monosilicic acid-treated pig manure reduced the phosphorus and potassium leaching and phosphorus fixation which resulted in an increase in the biomass of rice by 38.3-52.3% in greenhouse and rice yield in field increased by up to 17.4%. Phosphorus plant-availability in the soil and its uptake by rice plants were enhanced by the mixture of treatments. Furthermore, quicklime/monosilicic acid -treated pig manure enhanced the accumulation of potassium in rice leaves.

Implementing "from here to there": A case study of conceptual and practical challenges in implementation science

There is a significant challenge in global health and development research that pivots on the difficulties of delivering (cost-)effective treatments or interventions that are scalable andtransferable across settings. That is, how does one deliver "true effects", proven treatments, into new settings? This is often addressed in pragmatic trials or implementation research in which one makes adjustments to the delivery of the treatment to ensure that it works here and there. In this critical analytical review, we argue that the approach mis-characterises the cause-effect relationship and fails to recognise the local, highly contextual nature of what it means to say an intervention "works". We use an ongoing randomised controlled trial (RCT)-an informal settlement redevelopment intervention in Indonesia and Fiji to reduce human exposure to pathogenic faecal contamination-as a vehicle for exploring the ideas and implications of identifying interventions that work in global health and development. We describe the highly contextualised features of the research and the challenges these would pose in attempts to generalise the results. In other words, we detail that which is frequently elided from most RCTs. As our critical lens, we us the work of American philosopher, Nancy Cartwright, who argued that research produces dappled regions of causal insights-lacunae against a backdrop of causal ignorance. Rather than learn about a relationship between a treatment and an outcome, we learn that in the right sort of context, a treatment reliably produces a particular outcome. Moving a treatment from here to there becomes, therefore, something of an engineering exercise to ensure the right factors (or "shields") are in place so the cause-effect is manifest. As a consequence, one cannot assume that comparative effectiveness or cost-effectiveness would be maintained.

Optimization of Hydrolysis-Acidogenesis Phase of Swine Manure for Biogas Production Using Two-Stage Anaerobic Fermentation

The traditional pig manure wastewater treatment in Taiwan has been low in methane production efficiency due to unstable influent concentration, wastewater volume, and quality. Two-stage anaerobic systems, in contrast, have the advantage of buffering the organic loading rate in the first stage (hydrolysis-acidogenesis phase), allowing a more constant feeding rate to the second stage (methanogenesis phase). Response surface methodology was applied to optimize the operational period (0.5–2.0 d) and initial operational pH (4–10) for hydrolysis and acidogenesis of the swine manure (total solid 5.3%) at 35 °C in batch operation mode. A methanogenesis verification experiment with the optimal condition of operational period 1.5 d and pH 6.5 using batch operation resulted in peak volatile acid production 7 g COD/L, methane production rate (MPR) 0.3 L-CH4/L-d, and methane yield (MY) 92 mL-CH4/g-CODre (chemical oxygen demand removed). Moreover, a two-stage system including a hydrolysis-acidogenesis reactor with the optimal operating condition and a methanogenesis reactor provided an average MPR 163 mL/L-d and MY 38 mL/g volatile solids, which values are 60% higher than those of a single-stage system; both systems have similar dominant methane-producing species of Firmicutes and Bacteroidetes with each having around 30%–40%. The advantages of a two-stage anaerobic fermentation system in treating swine manure for biogas production are obvious.

Reducing odor emissions from feces aerobic composting: additives

Aerobic composting is a reliable technology for treating human and animal feces, and converting them into resources. Odor emissions in compost (mainly NH₃ and VSCs) not only cause serious environmental problems, but also cause element loss and reduce compost quality. This review introduces recent progresses on odor mitigation in feces composting. The mechanism of odor generation, and the path of element transfer and transformation are clarified. Several strategies, mainly additives for reducing odors proven effective in the literature are proposed. The characteristics of these methods are compared, and their respective limitations are analyzed. The mechanism and characteristics of different additives are different, and the composting plant needs to be chosen according to the actual situation. The application of adsorbent and biological additives has a broad prospect in feces composting, but the existing research is not enough. In the end, some future research topics are highlighted, and further research is needed to improve odor mitigation and element retention in feces compost.

Aerobic composting is a reliable technology for treating human and animal feces, and converting them into resources. The addition of additives can reduce the production of odor during the composting process.

Source, distribution and emerging threat of micro- and nanoplastics to marine organism and human health: Socio-economic impact and management strategies

The nature of micro- and nanoplastics and their harmful consequences has drawn significant attention in recent years in the context of environmental protection. Therefore, this paper aims to provide an overview of the existing literature related to this evolving subject, focusing on the documented human health and marine environment impacts of micro- and nanoplastics and including a discussion of the economic challenges and strategies to mitigate this waste problem. The study highlights the micro- and nanoplastics distribution across various trophic levels of the food web, and in different organs in infected animals which is possible due to their reduced size and their lightweight, multi-coloured and abundant features. Consequently, micro- and nanoplastics pose significant risks to marine organisms and human health in the form of cytotoxicity, acute reactions, and undesirable immune responses. They affect several sectors including aquaculture, agriculture, fisheries, transportation, industrial sectors, power generation, tourism, and local authorities causing considerable economic losses. This can be minimised by identifying key sources of environmental plastic contamination and educating the public, thus reducing the transfer of micro- and nanoplastics into the environment. Furthermore, the exploitation of the potential of microorganisms, particularly those from marine origins that can degrade plastics, could offer an enhanced and environmentally sound approach to mitigate micro- and nanoplastics pollution.

Triple-hurdle model analysis of the factors influencing biogas digester building, use and processing by Chinese pig farmers

Because of the pollution associated with pig manure, pig farmers are being encouraged to adopt environmentally friendly manure management solutions such as biogas digesters. However, as the correlations and influencing factors associated with the different manure disposal stages remain unclear, these solutions have failed to positively change farmer disposal behaviors. Therefore, this paper constructed a triple-hurdle model to empirically analyze the pig farmer manure disposal behaviors and the associated relationships under the belief that the three stage biogas digester decisions were driven by structurally different processes. This paper adds to the literature in three ways: (1) it provides a dynamic framework that identifies pig farmer manure disposal behaviors; (2) it applies a recently developed econometric method that corrects for conditional correlations between error terms; and (3) proves that certain factors might have opposite impacts in different behavior stages. It was found that cultivated land area and farm income ratio had statistically significant positive impacts on biogas digesters construction behavior but a negative influence on the farmers' use of the biogas digesters. Farmers who joined a cooperative were found to be statistically more likely to be biogas digester users, and the unconditional expected share of the actual treated manure was significantly higher. This study can assist policymakers in formulating and implementing strategies to encourage greater biogas digestor use by pig farmers.

Livestock Development in Hanoi City, Vietnam-Challenges and Policies

The rapid urban growth of Hanoi city requires a livestock production system that ensures both food security and the livelihoods of dwellers. This paper reviews the existing policies for livestock production of Hanoi city and the changes in livestock population between 2014 and 2018 and identifies major challenges for livestock development of the city. While a remarkable increase of the livestock population in recent years is evident, the dominance of small-scale farms, the presence of animal diseases, the slow progress of transiting farms out of urban areas, as well as the lack of analysis of climate change and gender impacts are major challenges that could affect the livestock development of Hanoi.

Manure management and pollution levels of contract and non-contract livestock farming in Vietnam

In analyzing contract farming of livestock production, many studies have focused on the economic aspect. This paper offers the environmental issue by investigating manure management and pollution levels of contract farming (CF) and non-contract farming (NCF) livestock producers in Vietnam. By surveying 270 pig farms and applying logit model, we found that commercial pigpen type of CF reduces the probability of manure separation, while larger garden area and knowledge of composting increase it. By analyzing the wastewater samples collected from 59 farms and employing nearest neighbor matching technique, this paper indicated that CF reduces the pollutants' concentrations in effluents. Using OLS regression models, we found out that manure separation contributes to a reduction in nutrient matters, while biogas plant or combination of biogas plant and stabilization ponds helps to diminish organic matters. The study results suggest that the government should regulate the minimum required land area for installation of the combined manure treatment plants (MTPs). Additionally, to recycle manure and improve nutrient matters in effluent, advanced technologies for separating solid manure are extremely necessary for CF producers. Furthermore, we recommend the government to build mechanisms to compel agribusiness firms engaging in their liability for the environmental side effects caused by their CF producers.

Carriage of carbapenemase- and extended-spectrum cephalosporinase-producing Escherichia coli and Klebsiella pneumoniae in humans and livestock in rural Cambodia; gender and age differences and detection of blaOXA-48 in humans

Objectives

This study investigates the frequency and characteristics of carbapenemase‐producing Escherichia coli/Klebsiella pneumoniae (CPE/K) and extended‐spectrum cephalosporinase‐producing E. coli/K. pneumoniae (ESCE/K) in healthy humans and livestock in rural Cambodia. Additionally, household practices as risk factors for faecal carriage of ESCE/K are identified.

Methods

Faecal samples were obtained from 307 humans and 285 livestock including large ruminants, pigs and poultry living in 100 households in rural Cambodia in 2011. Each household was interviewed, and multilevel logistic model determined associations between household practices/meat consumption and faecal carriage of ESCE/K. CPE and ESCE/K were detected and further screened for colistin resistance genes.

Results

CPE/K isolates harbouring bla_OXA‐48 were identified in two humans. The community carriage of ESCE/K was 20% in humans and 23% in livestock. The same ESBL genes: bla_CTX‐M‐15, bla_CTX‐M‐14, bla_CTX‐M‐27, bla_CTX‐M‐55, bla_SHV‐2, bla_SHV‐12, bla_SHV‐28; AmpC genes: bla_CMY‐2, bla_CMY‐42,bla_DHA‐1; and colistin resistance genes: mcr‐1‐like and mcr‐3‐like were detected in humans and livestock. ESCE/K was frequently detected in women, young children, pigs and poultry, which are groups in close contact. The practice of burning or burying meat waste and not collecting animal manure indoors and outdoors daily were identified as risk factors for faecal carriage of ESCE/K.

Conclusions

Faecal carriage of E. coli and K. pneumoniae harbouring extended‐spectrum cephalosporinase genes are common in the Cambodian community, especially in women and young children. Exposure to animal manure and slaughter products are risk factors for intestinal colonization of ESCE/K in humans.