Vector-borne diseases surveillance: a global health imperative

Vector-borne diseases (VBDs) are emerging as a significant threat to both human and animal health, with recent years seeing a troubling increase in their prevalence and spread. The World Organisation for Animal Health (WOAH) has highlighted this growing concern in their latest report “Animal Health Situation Worldwide” covering 2023 and early 2024, presented during its 91^st General Session. This analysis brings some additional elements related to the intricate relationship between climate change and the dynamics of VBDs, underscoring the urgent need for effective surveillance and control measures.

Climate change’s impact on
vector-borne diseases (VBDs)

VBDs, which include diseases transmitted by vectors such as mosquitoes, ticks, and flies, thrive in certain environmental conditions. The climatic conditions of tropical regions make them particularly vulnerable to these diseases. However, climate change is reshaping this landscape, altering vector density, activity periods, and geographical distribution. These changes facilitate the expansion of VBDs into new areas, posing significant risks to previously unaffected regions. 

WOAH’s report on the “Animal Health Situation Worldwide” underscores the complexity of this issue, noting that both biological and non-biological pathways influence VBD transmission. There is clear evidence that climate change is a critical driver in the spread of these diseases. Observational data corroborate this, showing an increasing trend in the maximum latitudes at which VBDs are reported, closely mirroring global temperature anomalies.

Revealing emerging trends 

Data reported through the early warning system of the World Animal Health Information System (WAHIS), from 2023 and early 2024 (as of 11 March 2024), reveal that VBDs were responsible for a total of 2,422 outbreaks across 28 countries and territories, in the context of exceptional epidemiological events. These events mainly include first occurrences, recurrences and new strains. The Americas notably experienced a large outbreak of western equine encephalomyelitis, with 1,461 outbreaks, while Europe reported 697 outbreaks of various VBDs. 

Of the 90 diseases of terrestrial animals currently listed by WOAH, almost a third are vector-borne (entirely or for which vectors play an important role), some of which have shown a significant evolution in 2023 and early 2024.

Infection with West Nile fever virus, bluetongue virus, lumpy skin disease virus and western equine encephalomyelitis virus were the most frequently reported in 2023 and early 2024, in the context of exceptional events. Infection with lumpy skin disease virus, for which exceptional events were predominant in Asia, accounted for 144 outbreaks, making it the most reported VBD outside Europe and the Americas through early warning. Notably, 99% of these VBD outbreaks in 2023 and early 2024 were detected in temperate regions, indicating a worrying shift in their geographical distribution. 

Monitoring the expansion of VBDs 

These challenges are not new and date back several years. In response, WOAH had launched in 2022 the PROVNA project, aimed at enhancing VBD surveillance in North Africa. This initiative seeks to define ‘ecoregions’ within the study area, identify vulnerable zones, and develop a prototype application to predict climatic and environmental changes.  

A notable case study presented in the report is the recent spread of infection with epizootic haemorrhagic disease (EHD) virus. Traditionally confined to regions like North America and parts of Asia, EHD has expanded its range significantly since 2006, with new reports from countries around the Mediterranean and into Europe. This spread exemplifies the broader trend of VBD expansion driven by climate and environmental changes. 

Taking action for global health 

WOAH’s report paints a vivid picture of the escalating threat posed by vector-borne diseases in the context of climate change. As it stands at its centenary, WOAH reiterates the need for robust surveillance systems, international collaboration, and adaptive strategies to manage this growing challenge. As climate change continues to influence the spread and impact of VBDs, the global community must respond with urgency and innovation to safeguard both human and animal health. Because animal health is our health. It’s everyone’s health. 

For more detailed insights, explore the full report.

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