'One health' is particularly suited to serve mobile pastoralists. Dinka pastoralists in Sudan inspired Calvin Schwabe to coin the term 'one medicine', indicating that there is no difference in paradigm between human and veterinary medicine. Our contemporary definition of 'one health' is any added value in terms of improved health of humans and animals or financial savings or environmental services resulting from a closer cooperation of human and animal health sectors. Here we present a summary of 'one health' studies with mobile pastoralists in Africa which were done in research partnership, demonstrating such an added value. Initial joint human and animal health studies revealed higher livestock vaccination coverage than in the pastoralist community, leading to joint animal and human vaccination intervention studies which demonstrated a better access to primary health care services for pastoralists in Chad. Further simultaneous animal and human serological studies showed that camel breeding was associated with human Q-fever seropositivity. In Borana communities in Ethiopia, human cases of Mycobacterium bovis infection could be related to strains isolated from cattle. A challenge remained with regard to how to assess vaccination coverage in mobile populations. With the advent of mobile phones, health and demographic surveillance could be established for mobile pastoralists and their animals. This presents vast possibilities for surveillance and control of human and animal diseases. Pastoralists prefer a 'one health' approach and therefore contribute toward the validation of this concept by showing real added value of the cooperation between human and animal health services.

We first review historic and conceptual background to integrative thinking in medicine. Lacking a general theory of 'One Health', we provide an operational definition of 'One Health' and its leverage as: any added value in terms of human and animal health, financial savings or environmental benefit from closer cooperation of human and animal health sectors at all levels of organisation. Examples of such added value of 'One Health' are given from the fields of health systems, nutrition and zoonoses control in Africa and Asia. 'One Health' must become main-stream rather than a new discipline or new association; it should just become normal that practitioners and professionals in the health, animal and environment sectors work together as closely as possible. Current and future challenges in financing clean energy, migration flows, food security and global trade further warrant rethinking of human and animal health services. A conceptual outlook relates health as an outcome of human-environment systems called 'health in social-ecological systems'. The paper ends with an outlook on the operationalisation of 'One Health' and its future potential, specifically also in industrialised countries.

PROBLEM: Reliable demographic data is a central requirement for health planning and management, and for the implementation of adequate interventions. This study addresses the lack of demographic data on mobile pastoral communities in the Sahel. APPROACH: A total of 1081 Arab, Fulani and Gorane women and 2541 children (1336 boys and 1205 girls) were interviewed and registered by a biometric fingerprint scanner in five repeated random transect demographic and health surveys conducted from March 2007 to January 2008 in the Lake Chad region in Chad. LOCAL SETTING: Important determinants for the planning and implementation of household surveys among mobile pastoral communities include: environmental factors; availability of women for interviews; difficulties in defining "own" children; the need for informationeducation-communication campaigns; and informed consent of husbands in typically patriarchal societies. RELEVANT CHANGES: Due to their high mobility, only 5% (56/1081) of registered women were encountered twice. Therefore, it was not possible to establish a demographic and health cohort. LESSONS LEARNT: Prospective demographic and health cohorts are the most accurate method to assess child mortality and other demographic indices. However, their feasibility in a highly mobile pastoral setting remains to be shown. Future interdisciplinary scientific efforts need to target innovative methods, tools and approaches to include marginalized communities in operational health and demographic surveillance systems.

SITUACIÓN: Contar con datos demográficos fiables es un requisito fundamental para la planificación y la gestión sanitarias, así como para la puesta en marcha de las medidas necesarias. El estudio aborda la falta de datos demográficos en las comunidades nómadas de pastores de la región del Sahel. ENFOQUE: Se realizaron entrevistas a un total de 1081 mujeres y de 2541 niños (1336 niños y 1205 niñas) árabes, fulanís y goraneses, y se les incluyó en un registro mediante un lector óptico-biométrico de las huellas dactilares en cinco encuestas demográficas y de salud aleatorias, repetidas y transversales que se realizaron entre marzo de 2007 y enero de 2008 en la región del Lago Chad, en Chad. MARCO REGIONAL: Entre los determinantes más importantes de la planificación y la puesta en marcha de las encuestas domiciliarias en las comunidades nómadas pastoriles se encuentran: los factores medioambientales, la disponibilidad de las mujeres para realizar las entrevistas, las dificultades para definir cuáles son «sus» hijos, la necesidad de desarrollar campañas de información-educacióncomunicación y la obtención de los consentimientos informados de los maridos en las sociedades patriarcales típicas. CAMBIOS IMPORTANTES: Debido a su elevada movilidad, sólo pudimos volver a encontrarnos con el 5% (56:1081) de las mujeres registradas. Por lo tanto, no fue posible establecer una cohorte demográfica y sanitaria. LECCIONES APRENDIDAS: Las cohortes prospectivas de carácter demográfico y sanitario son el método más preciso para evaluar la mortalidad infantil y otros índices demográficos. No obstante, sigue sin demostrarse su viabilidad en grupos de pastores que se desplazan mucho. Los futuros esfuerzos científicos interdisciplinarios deben dirigirse a la obtención de métodos, herramientas y enfoques innovadores que incluyan a las comunidades marginadas en los sistemas operativos de control demográfico y sanitario.

PROBLÈME: La fiabilité des données démographiques constitue un critère majeur, tant pour la planification et la gestion sanitaire que pour la mise en oeuvre d'interventions adéquates. Cette étude s'intéresse au manque de données démographiques concernant les communautés pastorales nomades du Sahel. APPROCHE: Au total, 1 081 femmes et 2 541 enfants (1 336 garçons et 1 205 filles) arabes, foulani et goranes ont été interrogés et enregistrés à l'aide d'un lecteur biométrique d'empreintes digitales, au cours de cinq enquêtes sanitaires et démographiques transversales aléatoires successives, réalisées entre mars 2007 et janvier 2008 dans la région du lac Tchad au Tchad. ENVIRONNEMENT LOCALE: Les facteurs déterminants pour la planification et la mise en oeuvre d'enquêtes auprès des ménages des communautés pastorales nomades comprennent: les facteurs environnementaux, la disponibilité des femmes pour les entretiens, les difficultés à identifier leurs «propres» enfants, le besoin en campagnes d'information, d'éducation et de communication, ainsi que le consentement éclairé des époux au sein de ces sociétés typiquement patriarcales. CHANGEMENTS SIGNIFICATIFS: Du fait de leur grande mobilité, seulement 5% (56/1 081) des femmes enregistrées ont été rencontrées à deux reprises. Il n'a donc pas été possible d'établir de cohorte démographique et sanitaire. LEÇONS TIRÉES: Les cohortes démographiques et sanitaires prospectives constituent la méthode la plus précise pour évaluer la mortalité infantile et les autres indices démographiques. Cependant, leur faisabilité dans un contexte pastoral hautement nomade reste à prouver. Les prochains efforts scientifiques interdisciplinaires devront cibler des méthodes, des outils et des approches novateurs, permettant d'inclure les communautés marginalisées dans des systèmes de surveillance démographique et sanitaire opérationnels.