WOAH urged strengthened surveillance and preparedness against vector-borne diseases following a marked increase in events reported to WAHIS since 2023. Bluetongue concentrates that increase, with 38 annual events compared with 9.1 between 2015 and 2022.
The World Organisation for Animal Health (WOAH) urged its members to strengthen surveillance, early warning and preparedness against vector-borne diseases, after detecting a marked increase in exceptional epidemiological events reported to the World Animal Health Information System (WAHIS) since 2023. A vector-borne disease can spread from one animal or person to another through a living organism, generally insects or ticks such as mosquitoes, ticks, fleas or sandflies, capable of carrying and transmitting pathogens.
Analysis of the official reports submitted to WAHIS shows that the increase is concentrated in a small number of diseases and countries, with significant repercussions for animal health, biodiversity conservation, food security, livelihoods and the resilience of Veterinary Services worldwide.
Bluetongue accounts for most of the rise, with an average of 38 exceptional epidemiological events per year recorded in 2023–2025, compared with an average of 9.1 per year between 2015 and 2022. This increase is mainly due to the introduction of the BTV-3 serotype in north-western Europe from the autumn of 2023.
Events related to West Nile fever, a zoonosis that can cause encephalitis in people, increased considerably, rising from an average of 8 to 55 per year. Equine infectious anaemia recorded a more moderate increase, mainly due to a rise in case notifications in countries of the Americas.
By contrast, other vector-borne diseases included in the WOAH List, such as lumpy skin disease, have generally remained close to their historical levels in terms of the number of events, although their geographical distribution has expanded considerably from Africa towards the Middle East, Europe and Asia. Since 2005, bluetongue alone has accounted for the majority of vector-borne disease outbreaks reported to WOAH, followed by lumpy skin disease.
Trends vary between regions: since 2022 Europe has reported the vast majority of bluetongue outbreaks, Africa has remained the main region affected by Rift Valley fever, and the Americas have recorded most cases of equine infectious anaemia and Western equine encephalomyelitis. WOAH warns that these data should be interpreted as trends in reported events and not as a direct measure of changes in incidence, since changes in surveillance intensity, diagnostic capacity and reporting practices can also have an influence.
The trends observed are consistent with the demonstrated relationship between climate change and vector ecology, highlighted in WOAH's 2025 report on the State of the World's Animal Health. Rising temperatures, changes in rainfall patterns and changes in land use are altering vector density, activity periods, survival and geographical distribution.
In some areas, conditions may allow vectors to reproduce throughout the year, considerably extending their activity period and increasing opportunities for pathogen transmission. These changes can create favourable conditions for the establishment or transmission of vector-borne diseases in previously unaffected regions, often with a temperate climate; the notifications received by WOAH have made it possible to document changes in geographical distribution, including an increase in the maximum latitude at which outbreaks have been reported.
Other factors, such as ecological changes, animal movements and unregulated trade, as well as changes in interactions between wildlife, farmed animals and people, can also influence the emergence and spread of these diseases. Many of the vectors involved transmit pathogens that affect both animals and people, reinforcing the need for surveillance and response that span the interface between animals, people and the environment.
Some vector-borne diseases involve complex interactions between animals, people, vectors and the environment. Effective prevention and control require an integrated One Health approach involving Veterinary Services, public health authorities, environmental agencies, research institutions and other relevant stakeholders.
Control options may be limited, and vaccination is an effective measure where available. Other preventive measures include reducing vector breeding sites, the use of mechanical protection and, where appropriate, repellents. The use of insecticides in the environment must be carefully assessed for its potential effects on non-target organisms and ecosystems, and further research is also needed to develop and evaluate biological control methods.
WOAH international standards, including the Terrestrial Code recommendations on surveillance of arthropod vectors, provide members with the scientific basis for assessing the presence, distribution and abundance of vectors and for designing surveillance strategies proportionate to risk.
WOAH also supports its members through innovative early warning approaches. Since 2022, the PROVNA project has been working with Veterinary Services in North Africa to combine Earth observation and climate data with disease occurrence data reported through WAHIS, and is developing models capable of identifying areas with environmental and climatic characteristics conducive to the presence and transmission of these diseases.
While several of the factors mentioned continue to change vector ecology, investment in surveillance, laboratory capacity and Veterinary Services is essential for animal health, but also for food security, livelihoods, biodiversity protection and global health security. WOAH remains committed to supporting its members through its international standards, its expert networks, its data systems and scientific collaboration to anticipate, prevent and respond to the changing threat of vector-borne diseases.
