Contemporary Anopheles vector species distribution in Scotland and its association with historical hotspots of malaria transmission

Background Malaria poses a significant threat to public health in tropical regions, with nearly half of the global population at risk. Historically, transmission was common in temperate regions including northwestern Europe, with records indicating that malaria was prevalent in Scotland until the early 19th century. While current environmental and epidemiological conditions are unsuitable for transmission, the risk of re-establishment of malaria or other mosquito-borne diseases in Scotland may increase with climate change. As a first step to assess the potential for future transmission risk, we aimed to map the distribution of two native Anopheles mosquito species in Scotland that have been implicated in historical malaria transmission and assess the relationship between areas of high contemporary suitability and historical hotspots of transmission. Methods Using data generated from a recent Scotland-wide mosquito surveillance programme and citizen science reporting (2023–2024), we used species distribution models to predict the current distribution of Anopheles claviger and An. plumbeus in Scotland and identify their associations with environmental and land-use variables. Another historical vector, An. maculipennis s.l., was also recorded but with too few observations for reliable modelling. Using georeferenced historical parish hotspots of malaria in Scotland (18th century records), we tested whether predicted contemporary suitability at hotspot locations was higher than expected by chance using comparisons against randomly sampled background locations. Results Several climatic and physical environmental variables were associated with Anopheles species distribution in Scotland, with altitude and landcover being the most consistent, and temperature and precipitation having variable impact across species. Anopheles were predicted to have widespread distribution across coastal and lowland Scotland, with pockets of habitat suitability extending up to the northeast coast and Shetland islands. Historical hotspots of malaria (parish locations) were consistently associated with higher predicted current suitability for Anopheles species than background locations. Conclusions Overall, these findings show that potential malaria vectors are still common throughout Scotland and highlight the need for continued monitoring to generate more accurate estimates of predictors, distribution and future disease risk.