Mosquito vector abundance, spatial distribution and arboviral transmission risk in high‐traffic cross‐border zones of Tanzania

Arboviral diseases remain a major global public health challenge because mosquito vectors continue to expand their geographical range through increasing international travel, urbanization and climate change. This study aimed to assess the abundance, spatial distribution and larval indices of mosquito vectors of medical importance in a cross‐border setting. A comprehensive entomological survey, using multiple collection techniques, was conducted between October and November 2024 at high‐traffic cross‐border zones at Mutukula ground crossing connecting Tanzania and Uganda and Namanga ground crossing connecting Tanzania and Kenya. Adult mosquitoes were collected using BG‐Pro traps, CDC light traps and Prokopack aspirators, while larval surveys were conducted through cross‐sectional household inspections of potential breeding habitats. Data were summarized using descriptive statistics, and associations between variables were assessed using the Chi‐square test or Fisher's exact test, as appropriate. Binomial and Poisson regression models were used to identify factors associated with mosquito abundance and breeding site occurrence, with statistical significance set at p < 0.05. A total of 6952 mosquitoes were collected, comprising Culex quinquefasciatus (84.7%, n = 5895), Aedes aegypti ( 10.0%, n = 689) and Anopheles gambiae s.l. (5.3%, n = 369). Significantly higher abundance of Aedes spp. and Anopheles funestus s.l was recorded in hamlets located within 400 m of the international border ( p < 0.0001), whereas Culex quinquefasciatus predominated in hamlets situated beyond 400 m from the border (χ 2 = 1938, p < 0.000001). One female Aedes albopictus was detected among the adult Aedes collections, suggesting the potential introduction of this invasive vector. Four of the 10 hamlets surveyed had larval indices exceeding recommended thresholds, indicating an elevated risk of arboviral transmission. This study revealed a high prevalence of Aedes aegypti within the cross‐border buffer zone and a broader distribution of Culex species beyond this zone. These findings underscore the urgent need for sustained vector control interventions and strengthened entomological surveillance and control beyond the International Health Regulations (2005) as amended in 2024, which recommended a 400 m buffer zone at points of entry to mitigate the risk of arboviral disease transmission and potential epidemics.