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10/22/2018

The One Health Approach to Zoonotic Emerging Infectious Diseases

The following post can also be found in the October 2018
issue of the American Journal of Bioethics.

by Ariadne Nichol and David Magnus, Ph.D.

In light of the continuing threat of emerging infectious diseases, as exemplified by the current Ebola outbreak in the Democratic Republic of Congo, we must carefully consider the ethical implications of different public health approaches. Seeking to find new innovative, ethical approaches to addressing the issue of emerging infectious diseases might not be the best strategy. Instead, reflecting on and utilizing previous successful approaches might provide a faster and more effective path forward. In the feature article in the American Journal of Bioethics, Edwards et al. advocate for a One Health approach to infectious disease prevention and control. The One Health approach has been advocated for many years. Considering roughly 75% of emerging pathogens are transmitted from animals to humans, it makes sense to use an ecological public health approach towards emerging infectious diseases that are zoonotic in nature. While the One Health approach has much to offer, it is compatible with a range of particular strategies for addressing Ebola, some of which are more plausible than others.

Many scientists would agree that a One Health approach could improve both animal health and human health. The approach ensures the wellbeing of the larger multi-species population in a given area based on the environment and species’ interactions with one another. There are multiple points of intervention that can minimize the spread of harmful infectious diseases through strong public health surveillance systems and vaccination measures. For example, focusing on the surveillance of disease within animal populations, such as livestock could help facilitate mapping of spillover risk to the human population. These ‘spillover’ events are often due to changes in land use and agricultural practices. Therefore, this idea of mitigating events where viruses make the leap between species has significant relevance in our ethical thinking today.

Second, there are good reasons for taking on robust surveillance and vaccination measures. In developing nations across the globe we can see a rising level of modernization and development. Therefore, more pathogens will emerge as communities venture out into new land territory in attempting to establish new agricultural or industrial developments. As our global society becomes increasingly interconnected, the ethical challenges presented by emerging infectious diseases will rise in importance and require the allocation of increasing resources. When viewing the current state of affairs, a broad One Health approach is promising and potentially a cost-effective means of avoiding, reducing or mitigating future global pandemic threats and should be an essential part of pandemic preparedness.

Edwards et al. make a strong claim to a moral imperative specifically for expanding vaccine research, and they do so by highlighting the importance of interrupting predictable chains of inter-species transmission of Ebola from animals to humans. However, in order to help alleviate the burden of emerging infectious diseases, including Ebola, Dengue, Rift Valley fever and Lassa fever, which are all zoonotic in nature, researchers must tailor interventions to the respective contexts. Here, we disagree with Edwards et al. on the specific intervention they propose in the Ebola context, trying to incorporate a One Health approach. They support a line of research previously conducted by Peter Walsh to vaccinate wild apes in an attempt to decrease inter-species transmission of Ebola. Yet, there are two main ethical issues with this intervention- there is little potential for accelerating human vaccine development and second, biological uncertainty exists in regard to the ecology of Ebola. Wild ape vaccine approaches would utilize an oral vaccination route (bait mediated); yet, this kind of vaccine formulation would differ markedly from that used in a human vaccine strategy. Most approved human vaccines are injectable. Exceptions are those used to protect against pathogens transmitted by oral-fecal route, such as polio. Ebola is not transmitted in this way. Individuals mainly get infected by touching infectious bodily fluids, contaminating their mucous membranes and allowing entry of the virus. Given the different routes and formulations, regulatory licensing bodies such as the FDA would not be likely to accept the kind of pluralistic approach to evidence Edwards et al. propose.

Moreover, as suggested by Afolabi and Afolabi in their commentary “Engaging the Uncertainties of Ebola Outbreaks: An Anthropo-ecological Perspective,” many uncertainties exist within the Ebola context in West Africa, including which animals are the natural reservoir hosts of Ebola virus. With this level of uncertainty, we think it would be morally irresponsible to direct resources towards a vaccination campaign with such little licensing benefit and potential risk of harm for the wild endangered apes from the experimental vaccines. A One Health approach should support development of vaccines, however studies should be conducted in animals that are known to be natural reservoir hosts or important vectors. Otherwise, vaccine research in the wrong animals would direct valuable resources away from more necessary research efforts. Specific interventions utilizing a One Health approach should have a firm evidence base, and be designed to produce a high probability of significant benefit, particularly for interventions that have the potential to harm affected species and exacerbate existing health disparities.

In conclusion, we agree with the idea of re-utilizing an old public health approach to combat emerging infectious disease, by grounding decisions in a broader ecological perspective of the disease landscape. However, as pointed out by some of the commentaries, it is crucial to contextualize the proposed interventions and health monitoring systems for them to be effective. Developing a good scientific understanding of the species interactions and disease burden within animal populations can help researchers construct effective interventions. Researchers must take up a One Health approach to zoonotic emerging infectious diseases in order to prevent future outbreaks and to uphold their ethical duty to minimize suffering and promote health for all.

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