One Health and Climate: Essentially Connected

Article by Prof. Martyn Jeggo 

One Health seeks to integrate the sciences of animal, human and environmental health in recognition of the interconnected nature of these three disciplines. One Health embraces the concept that by working across these disciplines, health problems can be better understood, and more effective and sustainable solutions developed. This approach does demand a change in culture and resourcing as those engaged in agriculture, human medicine and environmental management have been historically separated. Taking this more systems thinking approach to health research is gaining considerable traction across Governments and academia and providing seriously important insights into some of our most intractable problems such as antimicrobial resistance.

But where does climate change fit? From an environmental health viewpoint, climate change is easily recognised as a major factor driving significant change to our environmental well-being. However, climate change also significantly and directly impacts animal and human health in a myriad of ways. For example, vector borne diseases are governed by the distribution of the vector, and climate plays a crucial role in this distribution. In Australia as an example, this has a serious impact on the occurrence of the bluetongue virus, a disease that affects sheep, and other wild and domestic ruminants. an important disease of sheep. The distribution of culicoides (a type of biting midge), the vector vector of causing bluetongue vector is therefore continually monitored, to assist in demonstrating freedom of the disease for trade purposes. As another example, influenza in humans occurs primarily in times of cold and wet weather, and climate therefore impacts on when to vaccinate against this infection.

In the 1970’s whilst managing the national veterinary laboratory in North Yemen, I personally worked closely with the local Save the Children organisation. At this time there was about 70% child mortality at the children's clinic in the capital in Sanaa and some of this was attributed to salmonellosis. In the veterinary laboratory we were able to match the salmonella subtypes with those found in samples of faeces from the 2 million feral dogs roaming the capital. A dog culling and controlling program - carried out ostensibly for rabies control, also had a useful impact in reducing the child mortality rates. A great early example of One Health in action. Another example was in southern Sudan during the global rinderpest eradication campaign in the early 1990’s. I was involved in trying to vaccinate cattle in this difficult area, and whilst as veterinarians, we were not able to visit many crucial cattle rearing areas, the Red Cross were active. They agreed to take on vaccination of the cattle  as this gave them an increased visibility  and access to sick people that they would not otherwise have. The cattle were protected from rinderpest and more people were receiving treatment. One health in action!

A useful example that brings together human, animal health and climate interactions is that of Rift Valley Fever. This is a vector-borne disease of sheep, cattle and occasionally humans that was restricted to East Africa. A vaccine is available for sheep and, hence vaccinating prior to the wet season. This coincides with, when there is an increase in vector numbers and subsequent onset of disease, and has proved a useful strategy for controlling the disease both in animals and humans. But climate change has significantly altered the vector distribution both in timing and location, and the disease is now occurring in Arabia and elsewhere. Understanding the dynamics of this interaction between the climate, vector distribution, host disease occurrence and vaccination scheduling thus becomes crucial for the control of this serious disease – and a One Health approach, alongside climate modelling, is ideally suited to this task.

From the reverse side, it is also vital to understand the impact of animals and humans on climate and the changes we are experiencing. Anthropomorphic impacts on climate have been extensively documented over the past few years., and, for example, in livestock the impact of overgrazing of livestock on environmental degradation and deforestation are critical areas to consider. From a One Health perspective it is reasonable to argue that the healthier are our livestock, ourselves, and our environment, the less likely are these areas to drive climate change. Nevertheless, specific areas such as reducing methane emissions from cattle must be considered.

Clearly, most aspects of animal, human and environmental health are impacted by climate change and any effective process both to understand and maintain well-being must be integrated with an understanding of climate change. And for the most part, the impacts of the climate changes we are now so vividly experiencing, have serious negative implications for the health of our livestock, for humans and for the global environment. Taking a One Health approach requires an intimate understanding and appreciation of our current climate change challenges.

Biography of Professor Martyn Jeggo

Professor Jeggo has worked in research and research management of infectious diseases. This included spells in a number of developing countries, at the UK high containment laboratory and within the United Nations (UN). During this period of 18 years at the UN, he managed programs of support for animal health in the developing world with research related projects in some 150 countries. One such program involved support to laboratories in 40 countries assisting the global eradication of rinderpest for which he received the UN Medal. In 2002 he became Director of the Australian Animal Health Laboratory, one of the largest high containment facilities in the world. He was heavily involved in the global development of One Health and chaired both the first and third International Congress on One Health. He currently works on a part time basis within the framework of the Geelong Centre for Emerging Infectious Diseases – a One Health consortium.

Article published 2 November 2023