Zoonoses and wet markets: beyond technical interventions

Modelling the transmission dynamics of H9N2 avian influenza viruses in a live bird market

H9N2 avian influenza viruses (AIVs) are a major concern for the poultry sector and human health in countries where this subtype is endemic. By fitting a model simulating H9N2 AIV transmission to data from a field experiment, we characterise the epidemiology of the virus in a live bird market in Bangladesh. Many supplied birds arrive already exposed to H9N2 AIVs, resulting in many broiler chickens entering the market as infected, and many indigenous backyard chickens entering with pre-existing immunity. Most susceptible chickens become infected within one day spent at the market, owing to high levels of viral transmission within market and short latent periods, as brief as 5.3 hours. Although H9N2 AIV transmission can be substantially reduced under moderate levels of cleaning and disinfection, effective risk mitigation also requires a range of additional interventions targeting markets and other nodes along the poultry production and distribution network.

Live poultry markets beyond health risks: Understanding consumer preferences for live poultry in South China

Live poultry markets (LPMs) are veterinary and public health risks because of potential for zoonotic spillover of pathogens from diseased animals to humans. To control these health risks, veterinary and public health authorities in Asia, including China, have closed or restricted LPMs. In south China, however, LPM closure has been opposed or rendered infeasible by consumers who prefer to purchase live poultry. Previous scholarship has suggested this preference is due to cultural values of freshness. In this study, we present results from detailed interviews with shoppers in south China, including those who prefer live poultry and those who prefer pre-slaughtered poultry. We argue that broader concerns about food safety and quality, rather than freshness alone, drive the demand for LPMs. Live poultry provide sensory information that enable shoppers to evaluate safety and quality in ways that are not possible with pre-slaughtered, refrigerated meat. Based on these findings, we suggest that hygienic interventions into LPMs should recognize that not only freshness, but also trust, must be constructed and maintained in any intervention.

Quantifying Enteropathogen Contamination along Chicken Value Chains in Maputo, Mozambique: A Multidisciplinary and Mixed-Methods Approach to Identifying High Exposure Settings

BACKGROUND

Small-scale poultry production is widespread and increasing in low- and middle-income countries (LMICs). Exposure to enteropathogens in poultry feces increases the hazard of human infection and related sequela, and the burden of disease due to enteric infection in children < 5 y in particular is substantial. Yet, the containment and management of poultry-associated fecal waste in informal settings in LMICs is largely unregulated.

OBJECTIVES

To improve the understanding of potential exposures to enteropathogens carried by chickens, we used mixed methods to map and quantify microbial hazards along production value chains among broiler, layer, and indigenous chickens in Maputo, Mozambique.

METHODS

To map and describe the value chains, we conducted 77 interviews with key informants working in locations where chickens and related products are sold, raised, and butchered. To quantify microbial hazards, we collected chicken carcasses (n = 75 ) and fecal samples (n = 136 ) from chickens along the value chain and assayed them by qPCR for the chicken-associated bacterial enteropathogens C. jejuni/coli and Salmonella spp.

RESULTS

We identified critical hazard points along the chicken value chains and identified management and food hygiene practices that contribute to potential exposures to chicken-sourced enteropathogens. We detected C. jejuni/coli in 84 (76%) of fecal samples and 52 (84%) of carcass rinses and Salmonella spp. in 13 (11%) of fecal samples and 16 (21%) of carcass rinses. Prevalence and level of contamination increased as chickens progressed along the value chain, from no contamination of broiler chicken feces at the start of the value chain to 100% contamination of carcasses with C. jejuni/coli at informal markets. Few hazard mitigation strategies were found in the informal sector.

DISCUSSION

High prevalence and concentration of C. jejuni/coli and Salmonella spp. contamination along chicken value chains suggests a high potential for exposure to these enteropathogens associated with chicken production and marketing processes in the informal sector in our study setting. We identified critical control points, such as the carcass rinse step and storage of raw chicken meat, that could be intervened in to mitigate risk, but regulation and enforcement pose challenges. This mixed-methods approach can also provide a model to understand animal value chains, sanitary risks, and associated exposures in other settings. https://doi.org/10.1289/EHP11761.

Limiting the spillover of zoonotic pathogens from traditional food markets in developing countries and a new market design for risk-proofing

Traditional food markets are age-old systems that primarily serve the food supply needs of society's less affluent sectors, often operating with minimal infrastructure. These markets are prevalent in low and middle-income countries. However, their hygienic conditions are frequently suboptimal, potentially fostering the emergence and spread of presumptive zoonotic diseases. The recent emergence of zoonotic or potentially zoonotic diseases and their possible links to traditional food markets underscore the need for focused attention on this overlooked issue. The socioeconomic characteristics of traditional food markets reveal that despite the risk of zoonotic pathogen spread, these markets play a crucial role for large segments of the population. These individuals rely on such markets for their livelihood, food, and nutrition. Therefore, a comprehensive set of measures addressing various aspects of traditional food markets is necessary to manage and mitigate the risks of potential zoonotic disease emergence. In this article, we explore various facets of traditional food markets, paying special attention to the risks of zoonotic diseases that urgently require stakeholder attention. We also propose a new market design to prevent the risk of zoonotic spillover and advocate for the development of a Market Hygiene Index for these markets.

Wet market biosecurity reform: Three social narratives influence stakeholder responses in Vietnam, Kenya, and the Philippines

In 2020, Covid-19 led to global policy statements promoting bans and reforms to wet markets in Asia and Africa to prevent future pandemics. We conducted a comparative, exploratory qualitative study in 2021 in three countries (Kenya, Vietnam and the Philippines) to understand the social and political dimensions to biosecurity reform at wet markets. This included 60 key informant interviews and rapid ethnographic research in 15 markets, as well as a review of policy documents and online media articles. We found no evidence that the rhetoric of pandemic spillover that emerged in 2020 had any influence on policy or reform efforts apart from those related to Covid-19 infection control. Rather, we identified three main narratives that frame the problem of biosecurity and preferences for reform. The first, a human health narrative, questioned global framings about pandemic risk, viewed markets as sources for food security rather than disease, emphasized the need to strengthen the control of endemic diseases, and conceptualized health through the lens of 'freshness' rather than biomedical categories. A second modernization narrative approached biosecurity as part of a broader process of socio-economic development that emphasized infrastructural gaps, spatial arrangements, cleanliness and a conflict between reform and economic interests. A third narrative centered on local livelihoods and the tension between local market stakeholders and biosecurity and modernization efforts. This final narrative called into question the appropriateness of certain regulations and policies, including bans and closures, emphasized the importance of preserving cultural heritage and highlighted the need for collective political action to resist certain veterinary policies. In conclusion, wet market biosecurity strategies occur in the context of three contrasting narratives that emphasize different aspects of health and risk, and reflect different worldviews and interests. Within this context, there is a need for local government to strengthen market management and biosecurity in ways that enhance the agency of market stakeholders and strengthen local livelihoods and food security as part of a pluralistic and democratic politics.

Contamination by Antibiotic-Resistant Bacteria on Cell Phones of Vendors in a Peruvian Market

Background and Objectives. Multiple studies have evaluated the presence of bacterial contamination on cell phones in clinical settings; however, the presence and transmission of antibiotic-resistant bacteria on cell phones in the community have not been adequately elucidated. Material and Methods. A cross-sectional study was carried out to determine the presence of bacteria resistant to antibiotics on the cell phones of vendors in a Peruvian market and the associated factors. A sample of 127 vendors was obtained through stratified probabilistic sampling using a data collection form validated by experts. Cell phone samples were cultured using a standard technique, and antibiotic sensitivity was determined using the Kirby–Bauer technique. Chi-squared and Mann-Whitney U tests were used to determine factors associated with resistance in cell phone cultures. Results. Among the cell phones, 92.1% showed bacterial growth, predominantly Gram-positive bacteria (coagulase-negative staphylococci and Staphylococcus aureus), and 17% of the cultures showed resistance to at least three antibiotics evaluated. Two strains fell into the category of methicillin-resistant S. aureus, and three strains of E. coli had resistance to carbapenems. Conclusions. A short distance between customers and vendors, lack of a cell phone case, and having a cell phone with touchscreen are factors associated with antibiotic-resistant bacteria on cell phones.

Research and Innovation Opportunities to Improve Epidemiological Knowledge and Control of Environmentally Driven Zoonoses

While zoonotic diseases are defined by transmission processes between animals and humans, for many of these diseases the presence of a contaminated environmental source is the cause of transmission. Most zoonoses depend on complex environmentally driven interactions between humans and animals, which occur along an occupational and recreational environmental continuum, including farming and animal marketing systems, environmental management systems, and community leisure environments. Environmentally driven zoonoses (EDZs) are particularly challenging to diagnose and control as their reservoirs are in the natural environment and thus often escape conventional surveillance systems that rely on host monitoring. Changes in the environment as a result of climate change [1], human population density [2], and intensification of agriculture [3] have been linked to increasing transmission events for this group of infections. As such, there is a recognised need to be able to detect the presence of EDZs in the environment as a means to better anticipate transmission events and improve source attribution investigations. Finally, the recognition that a One Health approach is needed to combat these infections is signalling to governments the need to develop policy that optimises trade-offs across human, animal, and environmental health sectors. In this review, we discuss and critically appraise the main challenges relating to the epidemiology, diagnosis, and control of environmental zoonotic disease. Using a set of exemplar diseases, including avian influenza and antimicrobial resistant pathogens, we explore the epidemiological contexts (risk factors) within which these infections not only impact human health but also contribute to animal health and environmental impacts. We then critically appraise the surveillance challenges of monitoring these infections in the environment and examine the policy trade-offs for a more integrated approach to mitigating their impacts.