The Deadliest Animals on Earth Are Getting a Climate Upgrade

Baby sleeping under mosquito netting by Masum Saieed, Pexels

Every year, around 1.5 million people die from animal-related causes worldwide. Surprisingly, the animals responsible are rarely the large predators that dominate headlines.

Instead, the biggest killers are tiny disease-carrying organisms, such as mosquitoes.

Data compiled by Our World in Data shows that mosquitoes alone cause about 760,000 deaths annually, followed by venomous snakes (~100,000 deaths) and rabies transmitted by dogs (~40,000 deaths). Most of these deaths occur through disease transmission rather than direct attacks.  

While these risks have existed for centuries, climate change is now reshaping the distribution of disease-carrying animals, potentially increasing exposure in regions that historically faced lower risk. 

Key Highlights 

• Mosquitoes are the deadliest animals on Earth, causing about 760,000 deaths each year, mainly through malaria, dengue, and other mosquito-borne diseases. 
• Snakes are the second-largest animal killers, responsible for roughly 100,000 deaths annually, largely in rural areas with limited access to antivenom treatment. 
• Dogs account for around 40,000 deaths, primarily due to rabies transmission. 

Other disease-carrying organisms, including parasites and insects also contribute to global mortality. Examples include: 

• Freshwater snails (schistosomiasis) 
• Kissing bugs (Chagas disease) 
• Sandflies (leishmaniasis) 
• Tsetse flies (trypanosomiasis) 

Climate Change Context 

Climate change is altering temperature, rainfall, and ecosystem patterns, all of which influence the distribution and life cycles of disease-carrying animals. Warmer temperatures can accelerate mosquito reproduction and increase the rate at which pathogens develop inside vectors, while changes in precipitation and extreme weather events can create new breeding habitats such as standing water after floods. Climate conditions strongly influence where disease-carrying organisms can survive and how quickly diseases spread. 

Recent research published in The Lancet Planetary Health also highlights that climate change interacts with social inequalities such as poverty and limited healthcare access will amplify the burden of vector-borne diseases, in regions like sub-Saharan Africa where malaria already causes hundreds of thousands of deaths annually. The study emphasizes that climate-sensitive diseases including malaria, leishmaniasis, and even snakebite risk are increasingly linked to environmental changes and require community-centered research and locally driven health responses to reduce impacts. 

As temperatures rise and ecosystems shift, these changes may expand the habitable areas for the animal carrying the disease and increase exposure to diseases that historically occurred only in tropical regions. 

Global Implications 

• Expansion of diseases such as malaria, dengue, and others into regions previously unaffected.  
• Longer transmission seasons as warmer temperatures extend the active period of mosquitoes and other vectors. 
• Higher exposure for vulnerable communities, especially in tropical and rural regions with limited healthcare infrastructure. 
• Greater pressure on health systems, especially in low- and middle-income countries already facing climate and disease burdens. 
• Increased human–wildlife interaction as species shifts their habitats in response to climate stress. 

Key high-risk regions include: 

• Sub-Saharan Africa – where malaria and other vector-borne diseases already cause a major health burden. 
• South and Southeast Asia – experiencing rising dengue and mosquito-borne disease outbreaks. 
• Latin America and the Caribbean – where climate variability and urbanization are increasing dengue risk. 
• Small island states and coastal regions – where climate extremes and ecosystem shifts amplify disease vulnerability. 

Urgent Response Needed 

• Strengthen global vector-control strategies, including insecticide-treated bed nets, environmental management, and innovative biological approaches. 
• Expand access to life-saving treatments, such as malaria medication and snakebite antivenoms. 
• Improve disease surveillance systems to detect emerging outbreaks as vectors expand into new regions. 
• Integrate climate science into public health planning, ensuring preparedness for shifting disease patterns. 
• Increase global investment in climate mitigation and adaptation, recognizing the link between environmental change and infectious disease risks. 

Read more about health risks here. 

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