Comparative Immunology, Microbiology and Infectious Diseases
A “One Health” surveillance and control of brucellosis in developing countries: Moving away from improvisation
Introduction
In its foreword of the book “People, Pathogens, and Our Planet” – Volume 1: Towards a One Health Approach for Controlling Zoonotic Diseases, Juergen Voegele, Director of Agriculture and Rural Development, The World Bank writes the following: “A global surveillance and control system that is established primarily for emerging infectious zoonotic diseases with pandemic potential can be readily improvised to address the endemic diseases that are a priority in many developing countries, few of which have the capacity or resources necessary to monitor or control them effectively” (http://siteresources.worldbank.org/INTARD/Resources/PPP_Web.pdf).
In other words, to date there is no “One Health” surveillance and control system for endemic (i.e., enzootic) diseases like brucellosis, particularly – but not exclusively – in developing countries. Such a strong statement contradicts our intuitive feeling that there are benefits for public health and society to be gained by implementing sound control and eradication brucellosis programs for livestock, although such benefits need to be demonstrated, particularly in countries with scarce resources [1]. Should such benefits be documented, does this however mean that they are the outcome of a conceptually sound “One Health” approach?
It is fair to say that there are many unknowns and misconceptions that may lead to the implementation of improvised control measures for endemic diseases as written by Juergen Voegele. It is important to stress that there is an inherent risk that improvised measures might beat best not justified and would not help in providing a sustainable solution or worse, improvisation may be counter-productive or even detrimental. In order to be successful, a “One Health” approach has to be truly multi-disciplinary and every component of a global/holistic approach has to be addressed proficiently in its own right. More, given the changes in the livestock sector, its contact with wildlife and the resurgence and emergence of zoonotic diseases linked to it, a new “One Health” research and policy-generation strategy has to be defined [2]. It is in this context that the World Animal Health Organization (OIE) is endorsing a “One Health” approach which will result in a deeper and sustainable political support for the coordinated prevention of high public health and animal impact diseases at the human–animal interface (http://www.oie.int/en/for-the-media/onehealth/).
The aim of the manuscript is to highlight some of the unanswered questions related to the biology of Brucella spp. infections in humans and livestock, as well as questions related to brucellosis control measures that besides being efficient should also be realistic in developing countries where human and financial resources are scarce. Such information is needed for the definition of a “One Health” conceptual framework for zoonotic brucellosis in the developing world.
Control and eradication programs of animal brucellosis are implemented in the developed world whereas resources are often not allocated to such programs is developing countries. Epidemiological studies in these countries rely almost exclusively on brucellosis serology. Shortcomings of serology will be highlighted by reviewing scientific publications from Uganda, one of the few developing countries were brucellosis has been extensively studied for the last 15 years. From the human health perspective, the benefit of mass vaccination of livestock and the dramatic public health consequences following the absence or the discontinuation of animal vaccination campaigns will be illustrated by situations prevailing in Mongolia and Greece. Risk factors related to husbandry practices like nomadism and mixed herds will be addressed and the importance of non-classical livestock species and wildlife as a source of Brucella spp. for people will be highlighted. Finally, recommendations related to targeted actions will be made in the context of a sound conceptual brucellosis “One Health” approach.
Section snippets
Brucellosis control and eradication programs
Currently, about half a million human brucellosis cases are annually reported worldwide but the estimated number of unreported cases due to the unspecific clinical symptoms of the disease is supposed to be 10 times higher. In endemic countries prevalence rates often exceed 10 cases per 100,000 population [3]. Brucellosis is transmitted to humans from direct contact with livestock (occupational disease for abattoir personnel, farmers and veterinarians for example) or more often by ingestion of
Shortcomings in brucellosis serology
The “Manual of Diagnostic Tests and Vaccines for Terrestrial Animals” published by the OIE lists diagnostic tests in two categories: “prescribed” and “alternative”. Prescribed tests are required by the OIE Terrestrial Animal Health Code for the international movement of animals and animal products and are considered optimal for determining the health status of animals. The manual can be consulted on line following the link: //www.oie.int/en/international-standard-setting/terrestrial-manual/access-online/
Mass vaccination against animal brucellosis and human health benefits
The benefits of the implementation of mass vaccination campaigns as well as the negative consequences of the unsuccessful implementation or the discontinuation of such campaigns will be illustrated by the Mongolian and the Greek examples.
Mixed herds an nomadism
Intermingling of livestock species may cause uninfected animals to easily get exposed to the disease from multiple sources such as abortion discharges and direct contact with infected animals. Mixed farming and especially raising sheep and/or goats along with cattle was reported by many researchers to be a risk factor for Brucella transmission between different animal species. However this transmission does not occur indifferently in both directions. Indeed, whereas infection of sheep and goats
Brucellosis in non-classical livestock species, in wildlife and at the wildlife/livestock/human interface
Besides B. suis biovar 4 infection in reindeer/caribou (Tarandus tarandus) and Brucella suis biovar 2 infection in wildboar (Sus scrofa), brucellosis in wild ungulates seems always to result from a spillover from a livestock reservoir [40]. Only in very few cases does the infection establish itself and become sustainable in wildlife spillover species. This results almost inevitably from wildlife management practices as suggested for winter feeding of elk (Cervus elaphus) and bison (Bison bison)
Discussion
Nearly two-thirds of human pathogens are zoonotic and, of greater concern, nearly three-quarters of emerging and re-emerging diseases of human beings are zoonoses [47]. This is the rationale for establishing a global surveillance and control system primarily for emerging infectious zoonotic diseases with pandemic potential. However, improvising a system based on the early detection of infectious zoonotic diseases with pandemic potential to assess the zoonotic risk of endemic diseases prevailing
Conclusions
As far as the definition of a brucellosis “One Health” framework is concerned, it is of paramount importance to identify Brucella species infecting humans and the different animal species in order to rightly identify the source of infection and develop targeted control measures.
The following principles should always prevail:
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Although B. abortus may infect sheep and goats and B. melitensis cattle, only the preferential host species, i.e., sheep and goats for B. melitensis and cattle for B. abortus
Conflict of interest
None.
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