Las enfermedades zoonóticas emergentes en un mundo cambiante: ¿visión estratégica o apagando incendios?
30 de julio de 2010 - As human population expands, economic development proceeds in certain subsectors of the population and new technologies arise, societies around the globe face more complex and previously unknown challenges. Without a doubt we are experiencing a rapidly evolving world: a place where domestic struggles meet regional priorities that are moulded by international concerns and global issues. We now face climatic change, energy insecurity, nuclear proliferation, hegemonic contestation, deepening regionalism, international terrorism, radicalism, a new multipolar order, and novel diseases. This very last challenge is the one this article deals with. Briefly, the emergence of zoonotic diseases such as Nipah virus in 1999 in Malaysia, Severe Acute Respiratory Syndrome (SARS) in 2002 in China, Monkey Pox in mid 2003 in the United States, Highly Pathogenic Avian Influenza A subtype H5N1 (H5N1 HPAI) since early 2004 mainly in Southeast Asia but also in Europe and Africa, and Pandemic H1N1 Influenza in 2009 in North America, have heightened public awareness of the multidimensional linkages between wild animals, livestock production and global public health.
In an increasingly affluent, informed and interconnected world heading towards nine billion by 2050, animal production systems of all types will be pressed to provide the kind of high-quality protein people crave. Moreover, as four billion people in countries with emerging economies move slowly out of poverty, global meat consumption will grow at about five millions metric tons per year; while globally, in 2009, it reached about 280 millions metric tons. In fact recently, a report by the International Panel for Sustainable Resource Management (IPSRM) titled Environmental Impacts of Consumption and Production concluded that energy, in the form of fossil fuels, and agriculture, especially the raising of livestock for meat and dairy products, are the two areas currently having a disproportionately high impact on people and the planet’s life support systems. This and other publications provide further evidence that, as academics, netizens, opinion leaders, influential bodies, scholars and civic actions groups advocate for transformational measures to mitigate impacts and reduce pressures on the environment, the forthcoming decades will bring more extraordinary changes.
Despite strong economic incentives, excessive livestock production to meet growing demand of food animals can exacerbate problems of soil degradation, forest encroachment via deforestation and land clearing, biological impoverishment, and through overgrazing and intensive feed production, a loss in the soil’s ability to sequester carbon, as well as reductions in the amounts of cereals available for human consumption. As of right now, world agricultural production accounts for 18 percent of the total greenhouse gas emissions that are contributing to atmospheric imbalances and 60 percent of the phosphorus and nitrogen pollution. For comparison, the largest contributor to greenhouse gases is the world energy sector with 62 percent of total emissions, according to the United Nations Environmental Programme (UNEP). Ironically, as if this is not enough, further climatic changes are expected to affect agricultural production via water and heat stress, and changes in the spread of diseases, infections and pests. In a nutshell, as concentrations of atmospheric gases reach record levels, global temperatures are expected to increase by 1.8 to 5.8 degrees Celsius by the end of this century. The hydrologic cycle will be altered, since warmer air can retain more moisture than cooler air. This means that some geographic areas will have more rainfall, while others more drought and severe weather events. If this holds true in the future, rising temperatures and changing rainfall patterns will have a substantial effect on the burden of infectious diseases that are transmitted by insect vectors, contaminated waters, and through humid-environment macroparasites.
As global public health is repositioned in international agendas, it is imperative for disease emergence not be looked at in isolation, but must now be systematically viewed alongside dynamic changes in farming landscapes, animal agriculture intensifications, natural resource depletions, land utilisation patterns, trade globalization, human behaviours, food consumption, and evolving trends in agricultural production, distribution and marketing systems. Attention to and analysis of these changes will reveal the feasible and viable options to address the root causes that underpin pathogen evolution, establishment and persistence. Additionally, with population growth and labour opportunities arising in urban centres, mass movements within resource-poor countries against a backdrop of collapsed public health systems can create devastating epidemics. Migrants in their cross-country treks are exposed to disease vectors to which they have little resistance, and the diseases they pick up then move with them to their new places of residence –also infecting the people already living in that area. Conversely, individuals travelling between countries and continents for business or pleasure may find themselves in the midst of new urban centres within few hours, but for less than the incubation period for a typical infection to ensue. We must admit that these changes will drive our approach and actions. Another factor to consider is that there are communities who have gotten used to recurrent natural disasters and living with infectious diseases who have developed deeply embedded understandings of risks and resilience that ultimately influence the way they view and respond to hazards and threats. It is for this reason that cultural and social dimensions must be embraced, leveraged and made central to bring people, with their incentives and motivations, back into spotlight. In years to come, an important challenge in veterinary public health will be to balance the need for adequate population intake of animal-source protein and essential nutrients with the rapid selection, amplification and spread of pathogens in animal production systems. Evidently, addressing disease burdens on host populations must also consider livelihoods, poverty alleviation, food security, and environmental stewardship while constantly reassessing successes, failures, threats and opportunities.
As noted above, the numerous challenges faced by the international health community are daunting, yet not impossible to overcome. A principal obstacle is to rightly position the impacts of emerging zoonotic diseases on animal and human populations as a salient theme in global agendas, especially as it competes with other equally important and pressing priorities weighed by influential nation-states. The last decade has fortunately experienced an upsurge of narratives and discourses calling for a paradigm shift from selfish divergence towards unified, coordinated and interdisciplinary mechanisms across agricultural, ecological, nutritional, public health, scientific and veterinary communities worldwide, with the goal of making our world a safer one to live in. As altruistic as this rhetoric may be, the factual evidence suggest that, as a whole, we have reengaged in the classical case of triage, that is, the prioritized assignment of economic, human and physical resources on the basis of where these can be best used, where they are most needed, or where are they most likely to achieve success when suddenly faced with a previously unknown disease. Yes, common sense indeed argues that one can not worry of things not yet known, but in this case, when the health and welfare of humanity is at stake, common sense is verily just not enough. We must recognize that decades of extraordinary scientific and technological progress now grant collective confidence that development and diffusion of best practices and continuing innovation can advance our world much further in forecasting emerging zoonotic diseases that arise at the animal-human-ecosystem interface, and also now offers other cardinal directions for a healthy and prosperous environment for all.
Is the global health community following a strategic vision or engaging in fire-fighting?
Diseases will be always part of our lives. Pathogenic agents need animal, human and plant hosts to survive and thrive. The science and art dealing with the maintenance of health and the prevention, alleviation, or cure of diseases rests firmly on this premise. Human and veterinary medicine have spoken for long to each other, but with the emergence of SARS and H5N1 HPAI, a realization that these two disciplines needed to closely interact became absolute. This is the perfect case that illustrates how health within medical communities was seen then, and how it is perceived now. We can no longer address health independently. The simple truth is that there is only one health.
With this rationale in mind, the Food and Agriculture Organization of the United Nations (FAO), the World Organisation for Animal Health (OIE), the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF), in collaboration with the World Bank and the United Nations System Influenza Coordination (UNSIC), conceptualized the One World, One Health™ approach, which is a collaborative, international, cross-sectoral, multidisciplinary mechanism to address threats and reduce risks of detrimental infectious diseases at the animal-human-ecosystem interface. It strategically builds on the lessons learned from, and achievements of, the responses to H5N1 and H1N1 epizootics. This approach is acknowledged as a feasible and viable model to address the multidimensional challenges that are rapidly evolving in a changing world. While some regions are bound to benefit more than others, it is expected that the potential for One Health approaches to reduce disease burdens might be greater in specific hotspots, especially in developing countries in the tropics, than those estimated in studies conducted in developed countries. Although very likely to deliver substantial benefits to animal and human health and the environment, One Health will probably encounter commercial, cultural, and political resistance, and face numerous technical and logistical challenges. As a bankable start, to showcase the potential of this approach to both donors and sceptical stakeholders, a number of experts and strategists suggest the initiation of a worldwide early alerting and reporting mechanism that could be enabled by aggregation of open source, event-focused, web-based threats and hazards platforms such as Argus, Biocastor, GHSAG, GLEWS, GOARN, GPHIN, EMPRES-i, HealthMap, MedISys, OFFLU, ProMed and Pulse. In addition to its easy justification and investment worthiness, this timely gathering of disease intelligence is critically essential for the world to avoid wandering aimlessly in a wilderness of growing uncertainties.