Migratory Species and Wildlife Health

1.    General Information - What is Wildlife Health?

Wildlife health can be defined as “the physical, physiological, behavioural, and social wellbeing of wild-living animals measured at an individual, population and wider ecosystem level, and their resilience to change” (Meredith et al., 2022). From this perspective, ’health’ in individuals and wider populations infers that the basic needs of individuals and populations are met and they are able to perform their usual functions. It infers that populations are resilient and have capacity to adapt to social, epidemiological or ecological change (Stephen, 2014). Wildlife health refers to the state in which wild animal populations are resilient and functioning within their ecosystems, with minimal disease burden and stress from environmental factors. It is shaped by a dynamic interplay of biological, environmental, and anthropogenic drivers. The health of wildlife is not only about coping with disease but also the capacity of populations to thrive, reproduce, and contribute to ecological balance. Wildlife health is critical to species conservation and ecosystem stability and plays a key role in ecosystem services that support all life.

The causes, epidemiology and impacts of wildlife disease are often under-researched, a situation exacerbated by limited surveillance and outbreak investigation. This reduces our ability to prepare for, prevent or mitigate disease risks across all sectors of wildlife, people and domestic animals.  Framing wildlife disease primarily as an agricultural issue rather than a wildlife conservation concern has led to reluctance in leading on wildlife and ecosystem health, resulting in negative health outcomes across sectors.

Many wildlife health issues are under-detected or mischaracterised, limiting the development of robust and integrated approaches to wildlife and ecosystem health. There is an urgent need to strengthen national and global systems for wildlife disease surveillance, improve data sharing, and support coordinated outbreak responses.

1.1.   Importance of Wildlife Health

The health of populations of wild animals is not only important for maintaining conservation status and resilience of ecosystems, but it is intrinsically linked to health of other sectors. This is most easily understood by considering infectious agents that can be transmitted between livestock, other domesticated or feral animals and wildlife and vice versa, as well as those pathogens which are zoonotic i.e. transmissible between animals and humans. More broadly, the health of wildlife populations is important for ensuring provision of ecosystem services and maintenance of resilient ecosystems which promote health across all sectors. 

5.    One Health

Mexican free-tail bats (Tadarida brasiliensis) leaving the largest bat colony in the world, Bracken Cave, USA © USFWS/Ann Froschauer

The recognition of the interconnectedness of the health of humans, animals (both wild and domestic), and the environment has led to the mainstreaming of One Health approaches.

Definition (as adapted from OHHLEP, 2023):

One Health can be defined as an integrated, unifying approach that aims to sustainably balance and optimize the health of people, animals and ecosystems. 

• It recognizes that the health of humans, domestic and wild animals, plants, and the wider environment (including ecosystems) are closely linked and inter-dependent.
• The approach mobilizes multiple sectors, disciplines and communities at varying levels of society to work together to foster well-being and tackle threats to health and ecosystems, while addressing the collective need for clean water, energy and air, safe and nutritious food, taking action on climate change, and contributing to sustainable development. 

Key underlying principles include: 

1. equity between sectors and disciplines;
2. socio-political and multicultural parity (the doctrine that all people are equal and deserve equal rights and opportunities) and inclusion and engagement of communities and marginalized voices;
3. socioecological equilibrium that seeks a harmonious balance between human–animal– environment interaction and acknowledging the importance of biodiversity, access to sufficient natural space and resources, and the intrinsic value of all living things within the ecosystem;
4. stewardship and the responsibility of humans to change behaviour and adopt sustainable solutions that recognize the importance of animal welfare and the integrity of the whole ecosystem, thus securing the well-being of current and future generations; and
5. transdisciplinary and multisectoral collaboration, which includes all relevant disciplines, both modern and traditional forms of knowledge and a broad representative array of perspectives.

The One Health concept emphasises that intact, healthy ecosystems are foundational to preventing disease emergence and spread. Conversely, environmental degradation can increase the risk of outbreaks and amplify stressors that compromise immune function and health in wildlife. Controlling disease once it has emerged can be very challenging due to the complexity of many wildlife diseases and the ecological context within which they operate. Proactive, upstream interventions are more effective than addressing human, animal and ecosystem health problems only once they occur. The One Health approach aims to sustainably balance and optimise health management. It has become an integrated and unifying approach to health, including to address emerging infectious diseases, and is endorsed by multiple national and international organizations and intergovernmental agreements.

6.    Solutions for Promoting Wildlife Health

Livestock-wildlife interfaces create disease risks to both sectors. At these interfaces infectious agents can be transmitted in either direction between the two, particularly where there is a close phylogenetic relationship. Some indigenous breeds of livestock, including these Ankole cattle, exhibit greater disease resistance than exotic breeds © Sergey Dereliev

1. Tackling key drivers of disease emergence

It is important to recognize the commonalities between the drivers of both migratory species population decline and disease emergence. As such, urgent enhanced actions are required to address the drivers of population decline, including through climate change mitigation and adaptation; reducing habitat loss, fragmentation and degradation; limiting pollution; reducing overexploitation; preventing the spread of invasive non-native species; and addressing high-risk agricultural and aquacultural practices. Addressing these drivers of disease emergence will reduce threats and pressures on wildlife and ecosystems and is key to limiting ill-health and improving resilience to disease across sectors. 

2. Enabling frameworks for health

Implementation of the Sustainable Development Goals would significantly enhance the health of people, animals and the environment worldwide. One Health and ecosystem approaches appreciate the interconnectivity of health between wildlife, livestock and people, and are essential for maximizing health across sectors. However, One Health approaches can often be anthropocentric, with insufficient attention on promoting the health of wildlife. They should instead be used to promote equitable decision-making about health management, appreciating that promoting the health of wildlife reduces risks to humans and their interests as well as bringing conservation benefits. 

 One Health approaches require multisectoral and transdisciplinary collaboration and appropriate organizational structures and communication. These approaches should be promoted and enhanced at the national level, along with cooperation at the international level, in order to prevent and respond to wildlife health threats. 

Preventative approaches are both cost-effective and necessary to safeguard health in migratory wildlife, domestic animals and people. They should be a key feature of any future pandemic instrument being negotiated under the auspices of WHO. The role of those involved in biodiversity conservation and sustainable livelihoods should therefore be recognized for and actively supported in their contribution to health across all sectors. The role of UNEP in the FAO UNEP WHO WOAH Quadripartite is warmly welcomed. 

3. Managing interfaces and infectious diseases

Livestock-wildlife interfaces created by, for example, agricultural development and expansion into wild areas, are particularly problematic for infectious agent transmission and emergence. There should be a focus on ensuring effective protection of well-connected natural habitat and minimizing fragmentation to reduce ‘edge effects’ where transmission of infections could occur. 

Effort should be taken to better manage livestock to reduce risks for the benefit of all. Measures include: 

a) Improving biosecurity, livestock vaccination, and planning of both the location and nature of livestock management. 

b) Reassessing and reducing dependence on intensive livestock production systems that present particular threats to human and wildlife health. Reducing consumption of animal protein from these systems is desirable, both from an environmental and wildlife health perspective. 

c) Using resilient, adaptive local breeds of livestock that pose a lower risk in terms of pathogen spillover and spillback. 

Robust efforts should be made to prevent additional sources of pathogen pollution/introduction to wildlife and their environment, always recognizing the value of robust risk assessments and preventative approaches. These sources include feral animals, traded plants and animals, non-native species and animals released for game, conservation or other purposes. Additionally, practices within live animal market systems that pose a high risk of pathogen transfer and drive pathogen evolution should be reduced or improved through enhanced management.

4. Tackling non-infectious disease 

In addition to tackling the overarching drivers of disease emergence, measures to minimize non-infectious causes of wildlife mortality include: 

a) Taking action to reduce and mitigate pollutants and poisons, particularly where regulatory restriction and/or enforcement is required to prevent release or use of pollutants and poisons at source. 

b) Mitigating human-induced injury of wildlife from infrastructure and other human developments and activities. 

c) Removing barriers to migration such as habitat fragmentation, or physical barriers that can result in death through undernourishment. 

d) Considering the effects of nutritional deficits and stressors in terms of resilience to other diseases when planning changes to land use or altering habitats. 

5. Improving institutional preparedness, planning and response

Rather than viewing animal health as the sole responsibility of agriculture ministries, environmental authorities within governments also need to fully engage in wildlife health and recognise their role in promoting ecosystem resilience and positive health outcomes across sectors, including human pandemic prevention.

The development of national wildlife health strategies is encouraged, noting the important role they play in successful One Health approaches. 

The health of migratory populations can be protected and fostered by strengthening wildlife health systems. These comprise the expertise, resources and organizational structures that enable effective planning, and disease surveillance, diagnosis and management. Building this capacity is relatively inexpensive compared to the potential costs associated with reactive management of disease outbreaks. 

Governments, their agencies, and all those with responsibility for managing wildlife are encouraged to carry out contingency planning during times without outbreaks (‘peacetime’), ensuring that all relevant stakeholders are involved. This will not only help prevent wildlife health problems occurring in the first place but also facilitate swift and appropriate responses in emergency situations. It will also minimize the adverse impacts of disease outbreaks and guard against inappropriate control measures such as lethal responses. 

Robust wildlife health surveillance, with conservation (in parallel to livestock protection) as a key goal, is required to support contingency planning, early warning systems and risk assessments. Ecological and population monitoring should be integrated into surveillance systems so that the epidemiology and impacts of disease can be better understood. Thorough investigations of outbreaks of wildlife disease are needed to help inform epidemiological understanding and assist in future disease planning to minimize impacts across health sectors. 

Improvements are needed in wildlife diagnostics, including increased capacity in testing facilities. Additionally, it is important to prevent delays in diagnosis and research caused by regulatory limitations on transporting diagnostic and research specimens across national boundaries.

6. Filling knowledge gaps and prioritisation

In line with Article II.3.a) of the Convention, Parties should promote, cooperate in and support research relating to migratory species in the context of disease. Efforts should be made to address the significant gaps in our knowledge of the epidemiology and drivers of many diseases of migratory species. Research and resourcing should be targeted at priority health threats to migratory species, and particularly to species with a poor conservation status. 

7. Improving reporting and information sharing 

Global disease information and reporting systems for wildlife are essential for early warning as well as other aspects of disease control. These systems require further improvement to ensure rapid reporting and inclusion of contextual epidemiological and environmental information to better inform understanding of disease events and their conservation impacts. Timely information and data sharing on wildlife health issues between nations is encouraged, to enable early warning and risk assessments for management decision-making. 

8. Using information sources for wildlife health

Guidance on managing wildlife health and responding to diseases is available, and those with responsibilities for wildlife are encouraged to use it and adapt it for national and specific settings.