Forgotten in the tropics: research on Culex mosquitoes is overshadowed in malaria and dengue-endemic regions

BACKGROUND: In many countries where mosquito-borne diseases such as malaria and dengue are endemic, the research community focuses on studying the mosquito vectors of these diseases in the Anopheles and Aedes genera, respectively. In these settings, other mosquito taxa, including Culex spp. and associated pathogens, appear less frequently in published studies. Although the field widely recognizes that several mosquito taxa and pathogen systems are understudied in several regions, few studies have quantified these patterns. METHODS: We conducted a systematic literature review of mosquito-related studies published in 2010 and 2020 to test the hypothesis that the proportion of mosquito publications on Culex spp. would be higher in countries that are non-endemic for malaria and dengue. Studies were identified through PubMed and Web of Science using "Country + mosquito" keyword searches, screened by inclusion/exclusion criteria, and categorized by endemicity (malaria-endemic, dengue-endemic, both, and non-endemic). We summarized mosquito genera per study and compared their reporting frequencies using generalized linear mixed models (beta-binomial likelihood) adjusted for year and GDP per capita. RESULTS: After screening 10,834 unique publications, 1,389 met inclusion criteria. The average number of mosquito genera reported per study was significantly higher for non-endemic countries compared with countries endemic for malaria and dengue. Publications including data on Culex spp. mosquitoes were significantly higher for non-endemic countries (64.5%) compared with malaria endemic (30.2%) and dengue endemic (34.2%) countries. Between 2010 and 2020, reporting of Aedes spp. increased, whereas reporting of Anopheles decreased, consistent with changing global research emphasis over the decade, including the 2015-2017 Zika emergence and continued dengue expansion. CONCLUSIONS: These results indicate that the presence of human-amplified mosquito-borne pathogens (e.g., human malaria and dengue) is associated with lower reporting of Culex in the published field-collection literature and with comparatively less published attention to Culex-associated zoonotic pathogens. A step to help resolve this neglect is for researchers to include additional mosquito community data when publishing malaria and dengue vector studies. These findings can help the research and public health community to allocate attention on multiple vector-borne disease threats, proportional to the respective human health burden.