Strategic decision making in animal healthcare involves an array of complex factors interacting for the allocation of scarce resources. Consequently, modelling techniques which consider the actions ...and interactions of multiple decision makers, such as game theory and agency theory, have potential to provide insight of past and future interventions and policy which seek to improve economic efficiency. This scoping review aimed to identify, describe, and synthesise literature relating to multi-actor strategic decision making in animal healthcare. Embase, Web of Science, PubMed, CAB direct, EconLit, and AnthroSource were searched for literature published until November 2020. Studies were included if they were written in English, modelled strategic decisions between multiple actors, and contained information that related to animal healthcare practices. Data were analysed within the context of a conceptual framework based on strategic decision-making literature and modelling techniques. The identified literature (n = 31) had a strong focus on livestock healthcare and particularly on cattle (n = 13). Most studies (27/31) examined decisions concerning infectious disease and seven studies used compartmental models to include disease prevalence data. Almost all the articles (n = 30) used the monetary outcome of strategic decisions as a basis for expected utility, either through direct profit maximisation or via the aversion of losses. Nine studies used discursive and conceptual models to describe the strategic decision-making process, providing a wide lens by which to view decisions and opportunity to discuss the role of behavioural contributors to utility. Twenty-two studies used formal mathematical models to describe strategic decisions and used model solutions to provide recommendations to a specific problem, ten of which were parameterised with empirical data. Consequently, 20 articles provided specific policy recommendations to improve the welfare output of a system, the majority of which suggested the need for an increased level of state intervention in the animal health sector. This review describes the range of studies which have approached strategic decision making in animal healthcare through multi-player modelling techniques. These modelling techniques provide opportunity to consider the perspectives of multiple stakeholders and to combine economic and epidemiological data which may be beneficial to the development of animal health interventions.
Abstract
A cross-sectional study was conducted with 144 small-scale poultry farmers across 42 Bangladeshi villages to explore risk factors associated with avian influenza H5 and H9 seropositivity on ...backyard chicken farms. Using mixed-effects logistic regression with village as random effect, we identified crow abundance in garbage dumping places and presence of migratory wild birds within villages to be associated with higher odds of H5 and H9 seropositivity. At farm-level, garbage around poultry houses was also associated with higher odds of H5 and H9 seropositivity. In addition, specific trading practices (such as, purchase of chickens from live bird markets (LBM) and neighboring farms to raise them on their own farms, frequency of visits to LBM, purchase of poultry at LBM for consumption) and contact of backyard chickens with other animals (such as, feeding of different poultry species together, using pond water as drinking source for poultry, access of feral and wild animals to poultry houses) were associated with higher odds of H5 or H9 seropositivity. Resource-constrained small-scale poultry farmers should be able to address risk factors identified in this study without requiring large investments into poultry management, thereby reducing the likelihood of avian influenza virus transmission and ultimately occurrence of avian influenza outbreaks.
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.
Peste des petits ruminants (PPR), a devastating viral disease of sheep and goats, has been targeted by the global community for eradication within the next 15 years. Although an efficacious ...attenuated live vaccine is available, the lack of knowledge about the transmission potential of PPR virus (PPRV) may compromise eradication efforts. By fitting a metapopulation model simulating PPRV spread to the results of a nationwide serological survey in Ethiopia, we estimated the level of viral transmission in an endemic setting and the vaccination coverage required for elimination. Results suggest that the pastoral production system as a whole acts as a viral reservoir, from which PPRV spills over into the sedentary production system, where viral persistence is uncertain. Estimated levels of PPRV transmission indicate that viral spread could be prevented if the proportion of immune small ruminants is kept permanently above 37% in at least 71% of pastoral village populations. However, due to the high turnover of these populations, maintaining the fraction of immune animals above this threshold would require high vaccine coverage within villages, and vaccination campaigns to be conducted annually. Adapting vaccination strategies to the specific characteristics of the local epidemiological context and small ruminant population dynamics would result in optimized allocation of limited resources and increase the likelihood of PPR eradication.
Poultry production is a valuable source of nutritious food and income and is considered a crucial part of global development. This is especially important for countries such as Bangladesh where ...levels of hunger and childhood stunting remain high. However, in many low- and middle-income countries poultry production remains dominated by small to medium scale enterprises operating with poor farm biosecurity associated with poultry and zoonotic disease risks. We aimed to characterize the structure of poultry production in Bangladesh in order to identify the underlying structural factors and resulting practices which create risk environments for emergence, persistence and transmission of infectious diseases.
Using the concept of a production and distribution network (PDN), we conducted a review of the literature, 27 in-depth interviews with key-informants and stakeholders, and 20 structured interviews with poultry distributors to map the ways which poultry are raised, distributed and marketed in Bangladesh. Findings indicate that the PDN can be considered in the context of four major sub-networks, based on the types of chickens; broadly indigenous, cross-bred, exotic broiler, and layer chickens. These sub-networks do not exist in isolation; their transactional nodes - actors and sites - are dynamic and numerous interactions occur within and between the PDN.
Our findings suggest that the growth in small and medium scale poultry enterprises is conducted within ‘fragile’ enterprises by inexperienced and poorly supported producers, many of whom lack capacity for the level of system upgrading needed to mitigate disease risk. Efforts could be taken to address the structural underlying factors identified, such as the poor bargaining power of producers and lack of access to independent credit and indemnity schemes, as a way to reduce the fragility of the PDN and increase its resilience to disease threats.
This knowledge on the PDN structure and function provide the essential basis to better study the generation, mitigation and consequences of disease risks associated to livestock, including the analysis of potential hotspots for disease emergence and transmission.
Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal ...domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella. Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis, the early stages of agricultural development were likely to promote the exposure of humans to this pathogen.
Contact structure among livestock populations influences the transmission of infectious agents among them. Models simulating realistic contact networks therefore have important applications for ...generating insights relevant to livestock diseases. This systematic review identifies and compares such models, their applications, data sources and how their validity was assessed. From 52 publications, 37 models were identified comprising seven model frameworks. These included mathematical models (
= 8; including generalized random graphs, scale-free, Watts-Strogatz and spatial models), agent-based models (
= 8), radiation models (
= 1) (collectively, considered 'mechanistic'), gravity models (
= 4), exponential random graph models (
= 9), other forms of statistical model (
= 6) (statistical) and random forests (
= 1) (machine learning). Overall, nearly half of the models were used as inputs for network-based epidemiological models. In all models, edges represented livestock movements, sometimes alongside other forms of contact. Statistical models were often applied to infer factors associated with network formation (
= 12). Mechanistic models were commonly applied to assess the interaction between network structure and disease dissemination (
= 6). Mechanistic, statistical and machine learning models were all applied to generate networks given limited data (
= 13). There was considerable variation in the approaches used for model validation. Finally, we discuss the relative strengths and weaknesses of model frameworks in different use cases.
Because disease incidence in people is low at present, the focus should move beyond detection of human cases and emergency response towards prevention at the infection source.14 A multisectoral ...approach would be needed first to identify and then target the inter-related social, economic, cultural, biological, and environmental drivers underlying disease emergence and spread.
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