A One Health perspective on COVID-19: How can future pandemics be prevented?

Most human pathogens originate from non-human hosts. Diseases circulating between humans and animals are known as zoonoses. They are the key drivers of emergence and reemergence of infectious diseases. Zoonoses are classified into stages depending on the modes of transmission and their epidemiology. Stage two pathogens such as brucellosis and rabies are continuously transmitted from animals to humans but are not further transmitted between humans. Stage three pathogens such as monkeypox or Leishmania donovani are transmitted to humans and lead to limited transmission that stutters to extinction. The basic reproductive number R0 is defined as the number of secondary infections originating from one infected individual. In stage three, pathogens R0 is below 1. Stage 4 pathogens persist in animal reservoirs.

However, when they are transmitted to humans, they may lead to self-sustaining chains of transmission with R0 in excess of one. It follows that stage 4 pathogens represent the highest risk for future pandemics. For their prevention, transmission over the species barrier, although rarely occurring, should be avoided by all means. HIV/AIDS and COVID 19 are stage 4 pathogens. HIV/AIDS and COVID 19 can have devastating effects not only on human health and well being but also on the social cultural fabric and our economies. In view of that, effective prevention of animal-human transmission cannot be overemphasised. The financial resources required are very likely much less than the primary or secondary or indirect costs of a pandemic outbreak.

Back in 2012, The World Bank recommended engagement in a systemic approach for zoonoses control considering integrated surveillance response and control of human and animal diseases for primarily economic reasons. And still, with a few exceptions, contemporary surveillance response systems remain separated for humans and animals.

We extended a schematic that was originally proposed by The World Bank and included the range from the environmental dimension, such as wildlife and water bodies. They are potential reservoirs for zoonotic pathogens for the occurrence in domestic animals and humans which are part of the social ecological system. This schematic shows the relationship between the ecosystem and the social system. The earlier a zoonotic pathogen is detected in the environment, in wildlife, or in domestic animals, and the better human, animal, and environmental surveillance communicate with each other to prevent an outbreak, the lower are the cumulative costs.

As emerging diseases like SARS-CoV-2 are most often zoonotic, we need to investigate the bio-security of live animal markets, intensively farmed chickens and pigs and other interfaces of a number of animals in wildlife and domestic species.

To improve bio-security in live animal markets and on farms, animal welfare needs to be fundamentally changed. Animals are often kept under unacceptable, inhumane standards with very poor sanitary conditions. At the same time, domestic animal husbandry contributes to the livelihoods of hundreds of millions of small farmers. Drastic measures can lead to the loss of income and impeding poverty and hunger for large numbers of small scale farmers. For this reason, all stakeholders, for instance, farmers, traders, butchers, consumers, administrators, and scientists, should be included to identify locally adapted bio-security and animal welfare measures. This would still maintain economic activity.

This requires the societal participatory trans-disciplinary process that we addressed in the early steps of this course. It also requires a better governance of surveillance response systems of health governance. Public health governance is set by the International Health Regulation, IHR 2005, of The World Health Organisation. Animal health governance is followed by the performance of Veterinary Services Pathway (PVS) of The World Organisation of Animal Health (OIE). A better health governance bringing IHR and PVS together can be imagined as one Health Governance (OHG) to contribute to Global Health Security (GHS) which is supported by the tripartite engagements of WHO, OIE, and The Food and Agricultural Organisation of the United Nations, FAO. What this means is depicted in the figure that we showed earlier.

It shows how the cumulative societal cost increases from the earliest detection of zoonoses in wildlife and livestock until it reaches human populations. The earlier a zoonoses can be detected and the better information is communicated between animal and human health sectors, the lower are the cumulative costs of an outbreak. This is true since an early effective response can prevent exposure and reduces the risk of transmission. The impact of an early detection and action is shown in these three scenarios. Scenario 3 would be the final, undesirable stage of global health security through a One Health approach. Despite existing environmental threats and some animal exposure only few human cases would be observed, and cost could be kept at the minimum.

This is only possible by a high level of integration of human and animal health.

The Covid19 outbreak is an unexpected, classical example illustrating the urgent need for reform of health governance towards a fully integrated environment, wildlife, domestic animal, human surveillance response system for infectious diseases to contribute to global health security.