Zoonosis and Climate Change : A double threat to global health
Deep Narayan Singh, Ranjana Sinha, Gyan Deo Singh, Manmohan Kumar, Suchit Kumar & Dushyant Yadav
Bihar Veterinary College, Patna , Bihar Animal Sciences University, Patna- 800 014
Abstract
Climate change significantly impacts livestock production, affecting animal health, productivity, and the spread of diseases. Rising temperatures and changing precipitation patterns alter the distribution of vectors, pathogens, and hosts, increasing the risk of zoonotic disease transmission. The emergence of zoonotic diseases can be attributed to a number of factors, including biodiversity loss, land use, and international mobility of people, livestock, and goods. It is an increasingly recognized fact that climate change is a major driver of emerging infectious diseases. Extreme weather events, including floods, severe droughts, storms, and wildfires, in conjunction with gradual shifts in temperature and precipitation patterns, can profoundly alter ecosystems. This, in turn, can influence the survival and distribution of hosts, vectors (e.g. mosquitoes and ticks), and pathogens. Climate change impacts virus reservoirs, increasing transmission rates of vectors. Vector-borne diseases have already witnessed increasing numbers compared to before. Certain non-endemic areas are encountering their first-ever infectious disease cases due to increasing temperatures. Tick-borne diseases are undergoing transformations provoking a heightened prevalence. Food-borne illnesses are expected to increase owing to warmer temperatures. It is important to recognize that climate change has a multivariable impact on the transmission of viruses. With climate change comes the potential of increasing interspecies interactions promoting jumps. These factors must be considered, and an informed strategy must be formulated. Adaptation and mitigation strategies are required to curb these diseases from spreading. Despite significant evidence that climate change affects infectious diseases, gaps in research exist. We conducted this review to identify the potential role climate change plays in the emergence of new viruses.
Key words: Climate Change, Endemic, Vector, Weather and Zoonosis
Introduction
Climate change poses significant threats to human health and well-being, with far-reaching consequences. Rising temperatures, sea-level rise, and extreme weather events are altering ecosystems, increasing the spread of infectious diseases. The relationship between climate change and infectious diseases is complex, involving multiple factors. Ecosystem, Climate, and all living forms are interlinked in endless ways. In Greek, “Zoon” means animal, while “noses” implies illness. According to the World Health Organization (WHO), any disease or infection naturally transmissible from vertebrate animals to humans or humans to animals is classified as zoonosis. Diseases transmitted from animals to humans and vice versa through direct or indirect means are called Zoonoses. Evidence suggests that animals are key players in most infectious diseases affecting humans. The contribution of zoonoses in human infections could exceed 60%, with 70% of these coming from wildlife animal species only. Those animals could be pets, companion animals, and birds. Fish and aquatic animals also contribute to the emergence of infectious diseases of zoonotic origin. Insects are one of the zoonotic disease vectors and act as an intermediate reservoir for various pathogens. They have high nutritional benefits and are heavily relied on as food sources in Asia, Africa, and South America, intensifying the risk of spreading zoonotic disease. With nearly 2 billion people worldwide considering beetles, caterpillars, insects, and many other insects as favorable food sources, it is clear how potential zoonoses could be transmitted to these populations. It is observed that, edible insects increase the risk of zoonoses carrying various bacterial, parasitic, and foodborne pathogens
Effect of climate change on infectious or vector-born diseases
Those diseases transmitted through infected arthropod species, such as mosquitoes, sandflies, and ticks, are classified as vector-borne diseases. Climate readily affects the biological traits of both the vector and pathogen. Temperature variations can reshape the emergence of zoonotic diseases through changes in the number of vectors, transmission cycles, and the contact between species. Water availability is a determinant in oviposition patterns of vectors. As precipitation increases, vectors are more likely to find suitable habitats and mature faster with increased breeding.
The COVID-19 pandemic highlights the need for a broader understanding of climate change’s role in the emergence of infectious diseases. The relationship between climate change and infectious diseases, aiming to:
- Identify Trends: Analyze the impact of climate change on infectious disease emergence.
- Highlight Ramifications: Examine the consequences of climate change on public health.
- Provide Strategies: Offer adaptation and mitigation strategies to prevent public health crises.
- Analyze Gaps: Identify existing gaps in knowledge and policy.
By understanding the complex relationship between climate change and infectious diseases, effective policy decisions can be made to prevent public health crises and promote global health security.
Effects of climate change on livestock:
Direct Effects:
– Heat Stress: Reduced feed intake, milk production, and reproductive efficiency
– Mortality: Increased death rates due to extreme temperatures and humidity
– Immune System Suppression: Weakened immunity makes animals more susceptible to diseases
Indirect Effects:
– Changes in Feed and Water Availability: Droughts and altered precipitation patterns impact feed quality and quantity
– Vector-Borne Diseases: Increased spread of diseases like Rift Valley fever, African horse sickness, anaplasmosis, and babesiosis
– Water-Borne Diseases: Contaminated water sources lead to diseases like entero-haemorrhagic Escherichia coli
Impact on Livestock Health:
– Disease Transmission: Climate change increases the risk of disease transmission between animals and humans
– Reproductive Issues: Heat stress affects fertility and reproduction in livestock
– Growth and Development: Climate stressors impact animal growth rates and development
- Mosquito-borne disease
- Dengue:Dengue, transmitted by Aedes mosquitoes, is among the most important vector-borne diseases worldwide with a high disease burden. Increasing temperatures exhibit an almost exponential pattern on the species’ physiological traits, such as biting and development rates for vectors up to a certain level before tapering off. Similarly, increased rainfall facilitates the development of mosquito breeding sites up to a certain threshold, after which flooding demolishes them. The primary vectors for dengue Aedes aegyptii and Aedes Albopictus has increased in transmission by 10% and 15% since 1950 due to greater climate suitability.
Increased precipitation and temperatures due to climate change are projected to intensify dengue by 2050 in various parts of the world, including western Africa, the southeastern United States, and inland areas of Australia. These favorable climate conditions for the vector-borne virus will also prolong the transmission period by four months, specifically in the Eastern Mediterranean and Western Pacific regions.
Malaria:Malaria is a life-threatening disease caused by the Plasmodium parasites transmitted by the female Anopheles mosquitoes. Although the past five years have witnessed a decrease in the incidence of this disease owing to a range of human interventions, climate change can still cause increased transmission. Spread of malaria is affected by ecological factors such as temperatures, precipitation, and topography. As a result, equatorial regions with lower altitudes, increased rainfall, warmer temperatures, and higher humidity are favorable for the vector’s reproduction and longevity. Studies demonstrate that based on the projected climate change scenarios of longer monsoon periods and increased temperatures in tropical areas of Africa, the Anopheles vector is expected to widen its distribution area.
iii. West Nile virus: West Nile virus (WNV), primarily transmitted by the Culex species of mosquitoes, can cause serious health infections ranging from mild febrile illness to severe meningitis or encephalitis. The principal hosts for these mosquitoes are wild migratory birds, but there have been cases of human-to-human transmission (through blood or transplacental transfusions). Temperature appears to be the predominant factor in WNV transmission. Optimum temperatures regulate vector growth rate, mosquito survival, and external incubation time period. As temperatures increase (up to a certain threshold), the virus develops within vectors, and their transmission becomes increasingly efficient. These findings are particularly important as vectors can circulate WNV to further geographical regions.
Tick-borne Lyme disease: It is the most common vector-borne disease in North America and Europe. It is caused by the Borrelia burgdorferi spherocyte bacteria transmitted mainly by Ixodes pacificusand I. scapularisticks. Like mosquitoes, ticks are affected by weather conditions, and the changing climate can be responsible for the frequency and severity of Lyme disease. Elevated temperatures affect egg development, population density, growth cycle, and ticks’ dispersal.
Adaptation and Mitigation Strategies
Adaption and mitigation strategies are crucial in diminishing climate change’s ramifications on infectious diseases. Adaptation strategies focus on tackling climate change. Key strategies include modeling climate resilient health systems that include a
-Well-informed health workforce equipped with the necessary mechanisms to assist climate resilience
-Health information systems that facilitate skillful handling of health risks arising from extreme events caused by climate change
-Efficient service distribution including necessary foundations in cases of emergencies
-Sufficient financing and improving education.
– Climate-Resilient Breeding: Developing breeds that can withstand climate-related stressors
– Sustainable Farming Practices: Implementing practices that reduce greenhouse gas emissions and promote animal welfare
– Improved Veterinary Surveillance: Enhancing disease monitoring and surveillance systems to quickly respond to emerging diseases
– Diversification of Livestock and Crops: Increasing drought and heat wave tolerance and promoting ecosystem services.
Conclusions:
Climate change poses a profound threat to livestock health in terms of zoonotic disease transmission. Globally, temperatures are rising day by day, and vectors and pathogens are adapting to new environments to increase the likelihood of outbreaks in previously un-affected regions. Heat stress, other climate-induced factors, and weakened livestock immunity further amplify the risk of zoonotic disease transmission. This interplay between climate change and disease emergence highlights the need for urgent interventions like enhanced surveillance, biosecurity measures and adaptive livestock management practices. These challenges may be addressed by requiring a multifaceted approach that includes climate adaptation strategies and a deeper understanding of how environmental shifts impact disease dynamics in livestock
Zoonotic diseases are contagious illnesses that can spread from domestic or wild animals to people. These illnesses, which mostly have natural zoonotic origins, are especially important in light of the rise in infectious diseases that affect humans.
