Acceptability of Aedes aegypti blood feeding on dengue virus-infected human volunteers for vector competence studies in Iquitos, Peru

Background Transmission of dengue virus (DENV) from humans to mosquitoes represents a critical component of dengue epidemiology. Examinations of this process have generally been hampered by a lack of methods that adequately represent natural acquisition of DENV by mosquitoes from humans. In this study, we assessed artificial and natural blood feeding methods based on rates of DENV infection and dissemination within mosquitoes for use in a field-based epidemiological cohort study in Iquitos, Peru. Methodology/Principal findings Our study was implemented, stepwise, between 2011 and 2015. Participants who were 5 years and older with 5 or fewer days of fever were enrolled from ongoing clinic- and neighborhood-based studies on dengue in Iquitos. Wild type, laboratory-reared Aedes aegypti were fed directly on febrile individuals or on blood collected from participants that was either untreated or treated with EDTA. Mosquitoes were tested after approximately 14 days of extrinsic incubation for DENV infection and dissemination. A total of 58 participants, with viremias ranging from 1.3 × 102 to 2.9 × 106 focus-forming units per mL of serum, participated in one or more feeding methods. DENV infection and dissemination rates were not significantly different following direct and indirect-EDTA feeding; however, they were significantly lower for mosquitoes that fed indirectly on blood with no additive. Relative to direct feeding, infection rates showed greater variation following indirect-EDTA than indirect-no additive feeding. Dissemination rates were similar across all feeding methods. No differences were detected in DENV infection or dissemination rates in mosquitoes fed directly on participants with different dengue illness severity. Conclusions/Significance Our study demonstrates the feasibility of using direct and indirect feeding methods for field-based studies on vector competence. Direct mosquito feeding is preferable in terms of logistical ease, biosecurity, and reliability.
Author summary In the context of ongoing clinic- and field-based epidemiological studies on dengue virus (DENV), we compared methods of feeding mosquitoes on blood from naturally infected humans. Participants chose to participate in direct (uninfected mosquitoes applied directly to skin) and/or indirect (uninfected mosquitoes fed on a membrane feeder in the laboratory with blood drawn from a participant) methods. Overall, rates of DENV infection and dissemination were lower in mosquitoes fed indirectly on blood with no additive than in mosquitoes fed directly on a participant. Rates of DENV infection and dissemination were similar between mosquitoes fed directly and indirectly when anticoagulant (EDTA) was added. The indirect-EDTA method resulted in more variable infection rates than the direct method. Our results demonstrate the feasibility of using either direct or indirect feeding methods to study DENV-human infectiousness to mosquito vectors. In our experience, however, direct feeding is preferable to indirect feeding in terms of logistical ease, biosecurity, and reliability.