De Kesel, W. | bioRxiv Science

bioRxiv2026

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.

ecology↗

bioRxiv2024

Antibodies against medically relevant arthropod-borne viruses in the ubiquitous African rodent Mastomy natalensis

Over the past decades, the number of arthropod-borne virus (arbovirus) outbreaks has increased worldwide. Knowledge regarding the sylvatic cycle (i.e., non-human hosts/environment) of arboviruses is limited, particularly in Africa, and the main hosts for virus maintenance are unknown. Previous studies have shown the presence of antibodies against certain arboviruses (i.e., chikungunya-, dengue- and zika virus) in African non-human primates and bats. We hypothesize that small mammals, specifically rodents, may function as amplifying hosts in anthropogenic environments. The detection of RNA of most arboviruses is complicated by the viruss short viremic period within their hosts. An alternative to determine arbovirus hosts is by detecting antibodies, which can persist several months. We developed a high-throughput multiplex immunoassay to detect antibodies against 15 medically relevant arboviruses. We used this assay to assess almost 1,300 blood samples of the multimammate mouse, Mastomys natalensis from Tanzania. In 24% of the samples, we detected antibodies against at least one of the tested arboviruses, with high seroprevalences of antibodies reacting against dengue virus serotype one (7.6%) and two (8.4%) and chikungunya virus (6%). Seroprevalence was higher in females and increased with age, which could be explained by inherent immunity and behavioral differences between sexes and the increased chance of exposure to an arbovirus with age. We evaluated whether antibodies against multiple arboviruses co-occur more often than randomly and found that this may be true for some members of the Flaviviridae and Togaviridae. In conclusion, the development of an assay against a wide diversity of medically relevant arboviruses enabled the analysis of a large sample collection of one of the most abundant African small mammals. Our findings suggest a role in the transmission of multiple arboviruses by this ubiquitous rodent and provide a solid foundation for future molecular screening to elucidate the role in the arbovirus transmission cycle. Author summaryOne of the main causes of zoonotic related human morbidity and mortality is the transmission of arthropod-borne viruses such as dengue virus, Yellow Fever virus, and chikungunya virus. These viruses cannot only infect humans but also livestock, pets, and wildlife, though our understanding of their non-human hosts remains limited. Rodents are thought to be an interesting host for these viruses because they can be abundant, often live near humans and some are already known to be viral hosts. However, research has focused on non-human primates, neglecting other potential hosts. To address this gap, we have developed a high-throughput antibody test to screen rodent blood against 15 different arboviruses. Our findings reveal that a proportion of Mastomys natalensis, a common African rodent species, carry antibodies that (cross-)react against these viruses. We hypothesize that immunologically naive juveniles may drive transmission, particularly during population outbreaks. These outbreaks coincide with environmental conditions that are favorable for mosquitoes, the vectors of these viruses. Thus, increasing the risk of spillover to humans, livestock, and wildlife. Understanding the role of rodents in arbovirus transmission dynamics is crucial for mitigating zoonotic disease risks.

immunology↗