Introduction by Croakey: The importance of One Health approaches in climate responses is likely to be highlighted at the upcoming global Conference of the Parties (COP28) negotiations on climate change in Dubai, from 30 November to 12 December.
A draft of the COP28 Declaration on Climate and Health, which is be launched during the COP’s health day on 3 December, includes a recommendation for “collaboration on human, animal, environment and climate health challenges, such as by implementing a One Health approach”.
The draft declaration also recommends: addressing the environmental determinants of health; strengthening research on the linkages between environmental and climatic factors and antimicrobial resistance; and intensifying efforts for the early detection of zoonotic spill-overs as an effective means of pandemic prevention, preparedness and response.
In the article below, Professor Martyn Jeggo, a member of Vets for Climate Action, describes some examples of where One Health approaches have led to health gains, and calls for more concerted investment in One Health approaches, especially in relation to climate change and health.
Martyn Jeggo writes:
One Health seeks to integrate the sciences of animal, human and environmental health in recognition of the interconnected nature of these three disciplines. It 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 linked to climate change, such as antimicrobial resistance.
As climate change intensifies, this interconnectedness between the health of humans and animals is intricately linked to the health of the environment becomes even more apparent.
The recent rise in global pandemics such as avian influenza, SARS, MERS and COVID, in some instances characterised by host switching and exacerbated by environmental factors including climate change, highlights the importance of a holistic approach that considers both human and animal health in the context of a changing environment.
One Health seeks not only to better understand these relationships, but to develop solutions that are sustainable, environmentally acceptable, and economically viable.
Climate change also affects food security and nutrition, which are integral components of One Health. Shifts in temperature and precipitation patterns can disrupt agricultural systems, leading to changes in crop yields and the availability of certain foods. This, in turn, has implications for both human and animal nutrition.
The interconnectedness of food systems, environmental health, and human well-being underscores the need for collaborative efforts to ensure sustainable and resilient food production systems that can withstand the challenges posed by a changing climate.
Some examples of One Health outcomes follow.
Rift Valley Fever
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 and cattle, with occasional serious outbreaks of disease in that was restricted to East Africa. A vaccine was developed primarily for use in sheep for use prior to the wet season. It is during the onset of the wet season that there is an increase in vector numbers and serious outbreaks of disease.
Vaccination has proved a useful strategy for controlling the disease both in animals and humans. Notwithstanding this logic, annual vaccination of sheep is costly and difficult in affected areas, and since the disease does not occur every year it was not pursued.
Unfortunately, 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.
In recent years therefore, the Food and Agriculture Organisation, World Health Organization, and the World Organisation for Animal Health have developed predictive models that greatly assist in determining the likelihood and disease and thus when to vaccinate.
Hendra virus
Hendra is an occasional fatal virus infection of horses and humans that occurs on the east coast of Australia. The primary host of the virus are the flying fox bats, also found in this area. Horses get infected from under trees where the flying fox roosts.
Humans only become infected after close contact with a sick horse, but with a very high mortality rate. In most cases, this has been veterinarians treating a sick horse.
Changes in climate along the east coast of Australia, together with habitat destruction, have seen the disease spread from Queensland into New South Wales. Given the lethality of this disease in humans and its growing distribution, the Chief Medical Officer of Queensland convened a meeting in 2012 with human disease experts, veterinarians, ecologists and wildlife experts and climatologists to discuss how best to reduce the risks associated with Hendra.
Several options were considered, including “bombing” the bats, developing a Hendra vaccine for humans, or similarly developing a vaccine against Hendra for use in horses.
The ecologists pointed out the futility of trying to get rids of the bats, and it was clear that the timelines and costs of developing a Hendra vaccine for humans was not acceptable.
It was therefore decided to develop a vaccine for horses. Resources and the necessary science was then focused on this outcome and within 18 months such a vaccine was available and became widely used for at risk horses.
This is an excellent example of a One Health approach mitigating a serious disease risk – and one that was being significantly exacerbated by climate change.
Cattle methane emissions
Cattle methane emissions contribute significantly to global warming. Methane is a potent greenhouse gas, with a global warming potential many times greater than carbon dioxide over a short time frame.
Livestock, particularly cattle, produce methane through a process called enteric fermentation, which occurs in their digestive systems, mainly in the rumen. Additionally, manure management and rice cultivation are other sources of methane emissions associated with livestock.
Whilst reducing meat consumption in the developed world has been seen as an obvious way to reduce such emissions, in the developing world it is much more complex. Not only do the breeds of cattle and production systems in such areas have lower emission levels, but consuming livestock products is an essential part of a healthy and balanced diet in poor communities.
Using both a systems and one health approach, a number of strategies have been developed to mitigate cattle methane emissions for addressing climate change.
Below are some that have been explored.
Improved feeding practices: Changing the composition of cattle feed can help reduce methane emissions. For example, adding certain compounds (such as fats or oils) to the diet can inhibit methane production in the digestive system.
Feed additives: Some feed additives, such as tannins, seaweed, and certain chemicals, have been studied for their ability to reduce methane emissions from cattle. Seaweeds have shown promise in inhibiting methane production.
Genetic selection: Breeding cattle that are more efficient in converting feed into body weight can potentially reduce methane emissions per unit of meat or milk produced. This involves selecting for traits that result in lower methane production during digestion.
Methane inhibitors: Researchers are investigating various compounds and substances that can be added directly to the digestive system to inhibit the microbes responsible for methane production. This includes the development of methane inhibitors or vaccines.
Manure management: Proper management of manure can help minimize methane emissions. Anaerobic digestion, which captures methane from manure for energy use, is one option. Additionally, changes in manure storage and treatment practices can reduce emissions.
Agroforestry and silvopasture: Integrating trees into pastureland (agroforestry) or combining trees with livestock grazing (silvopasture) can have multiple benefits, including providing alternative feed sources, sequestering carbon, and potentially reducing methane emissions.
Grazing management: Implementing better grazing practices, such as rotational grazing, can improve the efficiency of cattle production, increase carbon drawdown into soil and reduce the overall environmental impact.
Education and outreach: Educating farmers about sustainable practices and providing incentives for adopting environmentally friendly methods can contribute to reducing methane emissions from cattle farming.
It’s important to note that a combination of these strategies, along with ongoing One Health research and technological innovation, will likely be necessary to achieve significant reductions in methane emissions from cattle.
Calls to action
In order to further promote the One Health agenda and to ensure that One Health activities explicitly continue to address climate change and the impact on health the following actions are proposed.
For government and funding agencies
Resources available for One Health activities, whether it be for research, policy development or operational, are traditionally made available through health, agricultural or environmental ministries, bodies or institutes.
This is far from ideal. A targeted pool of funding for One Health should be established. Within this framework, specific actions areas such as those concerned with the impact of climate change can be identified.
For those engaged in One Health activities
Given the considerable impact of climate change on health (whether of humans, livestock or the environment), this should become a priority area.
At a minimum, any One Health activities that leads to a better understanding, mitigation or climate change adaption processes should be clearly identified and wherever possible their impact quantified.
From an Australian perspective
The recent Government agreement to establish a Centre for Disease Control (CDC) or similar entity should include a One Health component, that is suitably resourced and has a specific component dealing with the impact of climate change within Australia and the threat it poses to the health of both humans and livestock.
Author details
Professor Martyn Jeggo has worked in research and research management of infectious diseases, including at the UN, where he managed programs of support for animal health in the developing world with research related projects in some 150 countries.
He received the UN Medal for his work supporting laboratories in 40 countries to assist the global eradication of rinderpest. In 2002 he became Director of the Australian Animal Health Laboratory.
He was heavily involved in the global development of One Health and currently works on a part time basis within the framework of the Geelong Centre for Emerging Infectious Diseases – a One Health consortium.
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