Culex mosquitoes in Tanzania show a strong preference for humans and non-commensal rodents
In Morogoro, Tanzania, Culex mosquitoes are feeding across a wider host range than many surveillance programs are built to capture. Blood-meal analysis from an urban-rural gradient found humans at the center of that network, with non-commensal rodents emerging as a major and previously underappreciated source of blood meals.
The study sampled mosquitoes at four locations representing different degrees of human influence during both wet and dry seasons. Across 8,917 mosquitoes collected, more than 90% belonged to the Culex genus, a detail that matters because these mosquitoes are common, adaptable, and often embedded in domestic and peri-domestic ecologies where human contact is frequent. Among 310 blood-fed and gravid mosquitoes examined for blood-meal origin, Nanopore-based metabarcoding identified 35 molecular operational taxonomic units that were grouped into 11 host categories.
Humans were the dominant host, accounting for 68% of identified blood meals. Non-commensal rodents followed at 22%, while crows accounted for 18%. The pattern is not simply a tally of feeding preferences; it reflects how mosquitoes move through shared environments where people, wildlife, and synanthropic animals intersect. A mosquito that routinely bridges these compartments can carry ecological information from one host community into another, even when no pathogen is detected in a given sampling window.
Non-commensal rodents stood out because they were not just eaten, so to speak, by mosquitoes in isolation. They were also the host group with significantly higher co-feeding probabilities with humans than any other host category, suggesting a shared biting network that could create conditions favorable for spillover if a competent arbovirus enters the system. The finding is especially relevant in settings where rodent habitats overlap with household compounds, market edges, agricultural fringes, and drainage areas that support larval breeding.
Flexible host use may amplify contact between wildlife and people
Culex mosquitoes did not behave as strict specialists. Instead, they showed broad host use and frequently fed on multiple taxonomic units, with an average of 1.36 taxonomic units detected per individual mosquito. That level of mixed feeding suggests either repeated feeding attempts, partial blood meals from more than one host, or the biological and behavioral flexibility that allows mosquitoes to sample whatever vertebrate hosts are most accessible in a given microenvironment. In practical terms, such feeding behavior can blur classical distinctions between enzootic and domestic transmission cycles.
The ecological consequences are easiest to see in the host-sharing network. Extensive overlap between humans and wildlife was detected, and non-commensal rodents sat near the interface of that network rather than at its margins. In arbovirus ecology, interface species matter because they can connect habitats that would otherwise remain semi-isolated. A mosquito that feeds on a rodent today and a person tomorrow does not need to be a classic anthropophilic vector to influence transmission dynamics; it only needs enough host mobility to move viral particles across that boundary.
Viral screening found no human-pathogenic arboviruses, but mosquito-associated viruses were present
Molecular screening of the mosquito pool did not detect any human-pathogenic arboviruses. Instead, viral detections were limited to insect-specific viruses, an endogenous viral element in chromosome 2 of Aedes aegypti, and two detections of Bagaza virus, a bird-infecting virus. The absence of human-pathogenic arboviruses in this dataset cannot be read as proof that local transmission risk is absent; it means only that the sampled mosquitoes did not carry those targets at the time and sites studied.
Even so, the viral findings are informative. Insect-specific viruses often circulate in mosquito populations without causing human disease, but they can influence vector biology and may interact with other viral infections in ways that are still being worked out. The detection of Bagaza virus points to ongoing viral circulation within the mosquito community and the broader vertebrate cycle connected to avian hosts. In other words, the mosquito population is not biologically quiet; it is moving viral material through an ecological network even when human disease agents are not present in the assay.
What the feeding pattern means for arbovirus surveillance in East Africa
This work expands the way mosquito surveillance is interpreted in a region where arbovirus ecology remains incompletely mapped. The dominant human blood meals confirm that Culex mosquitoes are not confined to wildlife-only cycles, while the substantial contribution from non-commensal rodents complicates any simple domestic-versus-wildlife divide. Rodents are often overlooked in vector surveillance because they are less visible than livestock, birds, or humans, yet this dataset places them squarely inside the mosquito feeding network.
The bedside translation is indirect but real: mosquito control programs that focus only on obvious household exposure may miss a larger interface involving peri-domestic rodents and heterogeneous habitat use. A surveillance strategy that ignores that bridge risks underestimating how pathogens could move if an arbovirus is introduced or re-emerges. The data also reinforce why blood-meal identification remains essential. Species counts alone do not explain transmission risk; host choice does.
The study does not establish transmission from rodents to humans, and it does not identify a specific arbovirus threat in the sampled mosquitoes. What it does show is a feeding ecology that could support spillover if the right virus enters the right network. In Morogoro, Culex mosquitoes are already navigating that network with considerable flexibility, and non-commensal rodents appear to be part of the route rather than an ecological footnote.