Blood-meal analysis indicates preferential feeding on humans and non-commensal rodents by Culex mosquitoes in Tanzania

Arthropod-borne viruses are important emerging and re-emerging pathogens worldwide, yet information on mosquito feeding ecology and associated transmission networks remains limited in many African regions. This study investigated mosquito host-feeding patterns and arbovirus occurrence along an urban-rural gradient in Morogoro, Tanzania. Mosquitoes were collected at four locations representing different levels of human influence during wet and dry seasons. Vertebrate blood-meal sources were identified using a Nanopore-based metabarcoding approach, while viral screening was performed using RT-qPCR assays targeting Orthoflavivirus and Alphavirus genera. A total of 8,917 mosquitoes were collected, of which more than 90% belonged to the Culex genus. Blood-meal analyses of 310 blood-fed and gravid mosquitoes identified 35 molecular operational taxonomic units, which we grouped into 11 host categories. Humans were the most frequently utilized hosts (68%), followed by non-commensal rodents (22%) and crows (18%). Culex mosquitoes showed broad host use and frequently fed on multiple taxonomic units, with an average of 1.36 taxonomic units detected per individual. Co-feeding network analyses revealed extensive host sharing between humans and wildlife, with non-commensal rodents showing significantly higher co-feeding probabilities with humans than any other host group. No human-pathogenic arboviruses were detected. Viral detections were limited to insect-specific viruses, an endogenous viral element in chromosome 2 of Aedes aegypti, and two detections of bird-infecting Bagaza virus, indicating ongoing viral circulation within the mosquito community. Our findings demonstrate broad and flexible host use by Culex mosquitoes and highlight non-commensal rodents as an underappreciated component of mosquito feeding with potential relevance for arbovirus transmission and spillover between wildlife and humans.