One Health, emerging infectious diseases and wildlife: two decades of progress?

Infectious diseases affect people, domestic animals and wildlife alike, with many pathogens being able to infect multiple species. Fifty years ago, following the wide-scale manufacture and use of antibiotics and vaccines, it seemed that the battle against infections was being won for the human population. Since then, however, and in addition to increasing antimicrobial resistance among bacterial pathogens, there has been an increase in the emergence of, mostly viral, zoonotic diseases from wildlife, sometimes causing fatal outbreaks of epidemic proportions. Concurrently, infectious disease has been identified as an increasing threat to wildlife conservation. A synthesis published in 2000 showed common anthropogenic drivers of disease threats to biodiversity and human health, including encroachment and destruction of wildlife habitat and the human-assisted spread of pathogens. Almost two decades later, the situation has not changed and, despite improved knowledge of the underlying causes, little has been done at the policy level to address these threats. For the sake of public health and wellbeing, human-kind needs to work better to conserve nature and preserve the ecosystem services, including disease regulation, that biodiversity provides while also understanding and mitigating activities which lead to disease emergence. We consider that holistic, One Health approaches to the management and mitigation of the risks of emerging infectious diseases have the greatest chance of success.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.

[Description of the process of preparation and response of local health authorities facing the introduction of the Chikungunya virus in Colombia, 2014]. / Caracterización del proceso de preparación y respuesta de entidades territoriales de salud ante la introducción del virus Chikungunya, Colombia, 2014.

Objective To describe the process of preparation and response of local health authorities in key public health issues while facing the introduction stage of an unusual virus: Chikungunya in Colombia in 2014. Methods A cross-sectional study was conducted using a survey that was developed for this study and sent to Public Health coordinators and to the person in charge of vector borne-diseases in the country's territorial entities. Results 23 out of the 35 territories at risk from the transmission of Chikungunya agreed to answer the survey. A global review of the survey scores for each evaluated section shows better performances in the areas of knowledge management, comprehensive patient care, epidemiological intelligence, and health promotion. According to the results of this study, the epidemiological surveillance system during the Chikungunya epidemic had a low acceptability and flexibility, possibly contributing to the underreporting of cases. Conclusions In general, knowledge and implementation by local authorities of the Integrated Health Strategy- EGI (Estrategia de Gestión Integral, by its Spanish acronym)- for vector-borne diseases was evident from the themes evaluated in this study. However, it is necessary to reinforce the communication of risks, laboratory, and outbreak and contingencies management areas faced during the introduction of new viruses.

A framework for the study of zoonotic disease emergence and its drivers: spillover of bat pathogens as a case study.

Many serious emerging zoonotic infections have recently arisen from bats, including Ebola, Marburg, SARS-coronavirus, Hendra, Nipah, and a number of rabies and rabies-related viruses, consistent with the overall observation that wildlife are an important source of emerging zoonoses for the human population. Mechanisms underlying the recognized association between ecosystem health and human health remain poorly understood and responding appropriately to the ecological, social and economic conditions that facilitate disease emergence and transmission represents a substantial societal challenge. In the context of disease emergence from wildlife, wildlife and habitat should be conserved, which in turn will preserve vital ecosystem structure and function, which has broader implications for human wellbeing and environmental sustainability, while simultaneously minimizing the spillover of pathogens from wild animals into human beings. In this review, we propose a novel framework for the holistic and interdisciplinary investigation of zoonotic disease emergence and its drivers, using the spillover of bat pathogens as a case study. This study has been developed to gain a detailed interdisciplinary understanding, and it combines cutting-edge perspectives from both natural and social sciences, linked to policy impacts on public health, land use and conservation.

Linking environmental nutrient enrichment and disease emergence in humans and wildlife.

Worldwide increases in human and wildlife diseases have challenged ecologists to understand how large-scale environmental changes affect host-parasite interactions. One of the most profound changes to Earth's ecosystems is the alteration of global nutrient cycles, including those of phosphorus (P) and especially nitrogen (N). Along with the obvious direct benefits of nutrient application for food production, anthropogenic inputs of N and P can indirectly affect the abundance of infectious and noninfectious pathogens. The mechanisms underpinning observed correlations, however, and how such patterns vary with disease type, have long remained conjectural. Here, we highlight recent experimental advances to critically evaluate the relationship between environmental nutrient enrichment and disease. Given the interrelated nature of human and wildlife disease emergence, we include a broad range of human and wildlife examples from terrestrial, marine, and freshwater ecosystems. We examine the consequences of nutrient pollution on directly transmitted, vector-borne, complex life cycle, and noninfectious pathogens, including West Nile virus, malaria, harmful algal blooms, coral reef diseases, and amphibian malformations. Our synthetic examination suggests that the effects of environmental nutrient enrichment on disease are complex and multifaceted, varying with the type of pathogen, host species and condition, attributes of the ecosystem, and the degree of enrichment; some pathogens increase in abundance whereas others decline or disappear. Nevertheless, available evidence indicates that ecological changes associated with nutrient enrichment often exacerbate infection and disease caused by generalist parasites with direct or simple life cycles. Observed mechanisms include changes in host/vector density, host distribution, infection resistance, pathogen virulence or toxicity, and the direct supplementation of pathogens. Collectively, these pathogens may be particularly dangerous because they can continue to cause mortality even as their hosts decline, potentially leading to sustained epidemics or chronic pathology. We suggest that interactions between nutrient enrichment and disease will become increasingly important in tropical and subtropical regions, where forecasted increases in nutrient application will occur in an environment rich with infectious pathogens. We emphasize the importance of careful disease management in conjunction with continued intensification of global nutrient cycles.

Emerging infections: a tribute to the one medicine, one health concept.

Events in the last decade have taught us that we are now, more than ever, vulnerable to fatal zoonotic diseases such as those caused by haemorrhagic fever viruses, influenza, rabies and BSE/vCJD. Future research activities should focus on solutions to these problems arising at the interface between animals and humans. A 4-fold classification of emerging zoonoses was proposed: Type 1: from wild animals to humans (Hanta); Type 1 plus: from wild animals to humans with further human-to-human transmission (AIDS); Type 2: from wild animals to domestic animals to humans (Avian flu) and Type 2 plus: from wild animals to domestic animals to humans, with further human-to-human transmission (Severe Acute Respiratory Syndrome, SARS). The resulting holistic approach to emerging infections links microbiology, veterinary medicine, human medicine, ecology, public health and epidemiology. As emerging 'new' respiratory viruses are identified in many wild and domestic animals, issues of interspecies transmission have become of increasing concern. The development of safe and effective human and veterinary vaccines is a priority. For example, the spread of different influenza viruses has stimulated influenza vaccine development, just as the spread of Ebola and Marburg viruses has led to new approaches to filovirus vaccines. Interdisciplinary collaboration has become essential because of the convergence of human disease, animal disease and a common approach to biosecurity. High containment pathogens pose a significant threat to public health systems, as well as a major research challenge, because of limited experience in case management, lack of appropriate resources in affected areas and a limited number of animal research facilities in developed countries. Animal models that mimic certain diseases are key elements for understanding the underlying mechanisms of disease pathogenesis, as well as for the development and efficacy testing of therapeutics and vaccines. An updated veterinary curriculum is essential to empower future graduates to work in an international environment, applying international standards for disease surveillance, veterinary public health, food safety and animal welfare.

Medical anthropology and Ebola in Congo: cultural models and humanistic care.

Seldom have medical anthropologists been involved in efforts to control high mortality diseases such as Ebola hemorrhagic fever (EHF) This paper describes the results of two distinct but complementary interventions during the first phases of an outbreak in the Republic of Congo in 2003. The first approach emphasized understanding local peoples cultural models and political-economic explanations for the disease while the second approach focused on providing more humanitarian care of patients by identifying and incorporating local beliefs and practices into patient care and response efforts.

Antimicrobial resistance in developing countries. Part II: strategies for containment.

The growing threat from resistant organisms calls for concerted action to prevent the emergence of new resistant strains and the spread of existing ones. Developing countries have experienced unfavourable trends in resistance-as detailed in part I, published last month--and implementation of many of the containment strategies recommended by WHO is complicated by universal, as well as developing country-specific, factors. The control of selective pressure for resistance could potentially be addressed through educational and other interventions for orthodox and unorthodox prescribers, distributors, and consumers of antimicrobials. At national levels, the implementation of drug use strategies--eg, combination therapy or cycling--may prove useful to lengthen the lifespan of existing and future agents. Programmes such as the Integrated Management of Childhood Illnesses (IMCI) and directly observed short-course therapy (DOTS) for tuberculosis are prescriber-focused and patient-focused, respectively, and have both been shown to positively influence factors that contribute to the selective pressure that affects resistance. The institution of interventions to prevent the transmission of infectious diseases could also lead to beneficial effects on the prevalence of resistance, as has vaccination against Haemophilus influenzae type B and Streptococcus pneumoniae. There has been an upsurge in the number of organisations and programmes that directly address issues of resistance, and collaboration could be one way to stem the dire trend. Additional factors such as unregulated drug availability, inadequate antimicrobial drug quality assurance, inadequate surveillance, and cultures of antimicrobial abuse must be addressed to permit a holistic strategy for resistance control.

Perspectives on emerging zoonotic disease research and capacity building in Canada.

Zoonoses are fundamental determinants of community health. Preventing, identifying and managing these infections must be a central public health focus. Most current zoonoses research focuses on the interface of the pathogen and the clinically ill person, emphasizing microbial detection, mechanisms of pathogenicity and clinical intervention strategies, rather than examining the causes of emergence, persistence and spread of new zoonoses. There are gaps in the understanding of the animal determinants of emergence and the capacity to train highly qualified individuals; these are major obstacles to preventing new disease threats. The ability to predict the emergence of zoonoses and their resulting public health and societal impacts are hindered when insufficient effort is devoted to understanding zoonotic disease epidemiology, and when zoonoses are not examined in a manner that yields fundamental insight into their origin and spread. Emerging infectious disease research should rest on four pillars: enhanced communications across disciplinary and agency boundaries; the assessment and development of surveillance and disease detection tools; the examination of linkages between animal health determinants of human health outcomes; and finally, cross-disciplinary training and research. A national strategy to predict, prevent and manage emerging diseases must have a prominent and explicit role for veterinary and biological researchers. An integrated health approach would provide decision makers with a firmer foundation from which to build evidence-based disease prevention and control plans that involve complex human/animal/environmental systems, and would serve as the foundation to train and support the new cadre of individuals ultimately needed to maintain and apply research capacity in this area.