Sustainable and Ethical Animal Management: Climate Change and Animal Disease

Sustainable and Ethical Animal Management: Climate Change and Animal Disease

Introduction and Learning Outcomes

This presentation, delivered by Pete Irons from Murdoch University, explores the critical interface between climate change and animal disease within the broader context of sustainable and ethical animal management.

Acknowledgment of Country

Murdoch University acknowledges the Binjareb people of the Noongar nation as the traditional custodians of the land and waters upon which the university stands, paying respects to their elders, past and present, and recognizing their wisdom and cultural knowledge.

Learning Outcomes

Upon completion, students should be able to:

  • Explain how climate change affects (and is projected to affect) animal diseases, outlining the underlying mechanisms.

  • Critically evaluate information regarding the impact of climate change on animal diseases.

  • Provide examples of animal diseases that have spread recently and discuss the role of climate change in their propagation.

  • Propose effective measures to manage the effects of climate change on animal disease.

The Urgency of the Issue

Recent news highlights the escalating threat:

  • Exotic vector-borne diseases: Scientists warn that these are worsening due to climate change.

  • Lumpy skin disease (LSD): There are fears that LSD could reach Australia before Foot and Mouth Disease, potentially costing Australia 7.4extbillion7.4 ext{ billion} in its first year alone if an outbreak occurs.

The Ecosystem of Disease

Disease is an inherent part of the 'ecosystem', fundamentally governed by the interactions between:

  • Environment

  • Host

  • (Vector?)

  • Agent / Pathogen

Climate Change and Infectious Disease Manifestations

Climate change profoundly influences disease dynamics by acting on the environment, host, pathogen, and vectors, leading to:

  • Geographical Shifts: Changes in the distribution patterns of hosts, vectors, or pathogens.

  • Persistence Alterations: Modifications in how hosts and vectors/pathogens survive and sustain themselves within an environment.

  • Homeostatic Imbalance: Disruption of the natural balance within ecological systems.

It's important to note that these effects can be positive, negative, or neutral depending on the specific system and context.

Mechanisms of Interaction

The way infectious disease moves through a system is determined by the inherent characteristics of the host, the agent, and the environment. Climate change interacts with all these components.

While there may be 'winners' and 'losers' among species and pathogens, the overarching impact of climate change is to undermine the resilience of systems, forcing them to adapt rapidly to continuously changing environments.

Host Impacts

Climate change directly impacts hosts in several ways:

  1. Undermined Resilience: Events like droughts, floods, and shifts in resource availability weaken host immunity and overall health, making them more susceptible to disease.

  2. Range Shifts and Redistribution: As climates change, hosts may migrate to new areas, potentially leading to:

    • Novel interactions with pathogens.

    • New encounters with other host species carrying different pathogens.

    • Interactions with new vectors.

    • Changes in host density, which can directly influence disease transmission rates.

Vector Impacts

(Based on Bett, B, Preventive Veterinary Medicine 2017)
Changes in climatic factors such as temperature, humidity, rainfall, flooding, and droughts critically influence:

  • Vector Distribution: Altering the geographical ranges where vectors (e.g., mosquitoes) can survive.

  • Vector Reproduction: Affecting their life cycles and population numbers.

These changes can:

  • Facilitate the spread of vector-borne diseases into previously unaffected areas.

  • Conversely, reduce the incidence of vector-borne diseases in other areas where conditions become unfavorable.

Agent/Pathogen Impacts

(Based on Bett, B, Preventive Veterinary Medicine 2017)
Environmental changes also directly affect pathogens:

  • Survival and Replication: Shifts in temperature, humidity, rainfall, flooding, and droughts influence the survival and replication rates of pathogens. These changes are not always beneficial to the pathogen.

  • Evolution and Emergence: Host redistribution and alterations in host 'assemblages' create new opportunities for pathogen evolution and the emergence of more pathogenic variants.

Identifying Climate-Sensitive Systems

A system is likely to be climate-sensitive if its host(s) or agent(s) are dependent on factors that are expected to adjust with climate change. Key factors to consider include:

  • Rainfall

  • Humidity

  • Temperature

  • Extreme weather events

  • Host densities

  • Redistribution of species

Comprehensive Health Effects of Climate Change

(Adapted from Bett, B, Preventive Veterinary Medicine 2017)
Anthropogenic greenhouse gas emissions drive climate change, resulting in changes in mean climatic conditions and variability (e.g., temperature, precipitation, humidity, wind). These changes have both direct and indirect effects on health:

Direct Effects

  • Changes in temperature and other climate variables.

  • Increased frequency, severity, and altered geography of extreme weather events (e.g., floods, storms, cyclones, bushfires).

Indirect Effects

  • Changes in ecosystems.

  • Socio-cultural or behavioral changes.

Health Impacts

These effects collectively manifest as a range of health consequences:

  • Thermal stress: Leading to deaths, illnesses, changes in immunity, and reduced feed intake in animals.

  • Injury or death: Resulting from extreme weather events like floods, storms, cyclones, and bushfires.

  • Pathogen and Vector Dynamics: Altered proliferation rates (increased or decreased development) of microbial, fungal, and parasitic agents.

  • Vector-Pathogen-Host Relationships: Fundamental changes in these intricate interactions.

  • Disease Distribution: Shifts in the spatio-temporal distribution of diseases.

  • Host Diversity: Changes in the diversity and abundance of host species.

  • Agricultural Productivity: Changes in the productivity of crops, forages, and rangelands, impacting feed availability and quality.

  • Socio-economic Impacts: Movement of populations, loss of livelihoods, conflicts, poverty, and reduced access to health services.

Real-world Implications and Examples

Human Health Perspective

(Mora, C. et al. Nat. Clim. Chang. 2022)

  • Widespread Impact: Over half of known human pathogenic diseases can be aggravated by climate change.

  • Complex Pathways: Researchers identified over 1,0001,000 different pathways through which various climatic hazards, via different transmission types, resulted in disease outbreaks by a taxonomic diversity of pathogens.

  • Urgent Call to Action: The sheer number of affected diseases and transmission pathways underscores the immense human health threat posed by climate change, emphasizing the urgent need for aggressive actions to mitigate Greenhouse Gas (GHG) emissions.

Animal Health Examples

  • Malaria in Africa: (Ryan, S.J. et al. Malar J 2020)

    • Both the malaria vectors (mosquitoes) and the parasite itself are highly dependent on specific levels of rainfall and humidity.

    • Rising temperatures are causing a latitudinal shift in the distribution of these vectors, expanding malaria risk into new areas.

Challenges in Adaptation

(Stephen, C., Wade, J.)
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