Detritus and larval competition influence phenotypic traits, nutrient stoichiometry, and vector competence for dengue...

Aedes aegypti is the primary vector of dengue virus (DENV), a major arboviral disease affecting human health. Variation in detritus inputs and larval competition in containers where the species develop can influence female Ae. aegypti phenotypic traits, nutrient content (carbon, nitrogen, C:N ratio), and elemental isotopes (δ¹³C and δ¹⁵N), ultimately affecting vector competence for DENV.

Female Ae. aegypti were reared under simulated urban detritus levels (low, medium, and high) and larval intra- (30:0 and 60:0) and interspecific (30:30 and 60:60) competition with Ae. mediovittatus (Ae. aegypti: Ae. mediovittatus). Aedes aegypti were offered a DENV-1-infected bloodmeal. Transmission assays were conducted, followed by assessment of susceptibility to infection, disseminated infection, and transmission rates. Body nutrient composition and isotope values were measured and analyzed in relation to phenotypic traits and vector competence for DENV-1, with male body nutrient profiles used as proxies for females where sample sizes were limited.

Longer development time and reduced wing length in Ae. aegypti were associated with low detritus. Wing length increased under interspecific competition with Ae. mediovittatus but decreased under intraspecific competition. Higher δ¹⁵N values in Ae. aegypti body tissues were associated with greater detritus availability and with interspecific competition. DENV-1 dissemination exhibited a nonlinear relationship with δ¹⁵N, showing high dissemination at low δ¹⁵N, the lowest dissemination at intermediate δ¹⁵N, and an increase at higher δ¹⁵N. Vector competence for DENV-1 was reduced under conditions of low detritus and low intraspecific competition (30:0). High interspecific competition combined with high detritus negatively affected Ae. aegypti phenotypic traits and reduced DENV-1 vector competence. Under the most extreme conditions (high interspecific competition, 60:60, and high detritus), Ae. aegypti failed to reach adulthood. At intermediate detritus levels for the same density, Ae. aegypti exhibited high rates of DENV-1 disseminated infection.

This research underscores the importance of larval crowding and nutritional availability experienced during the immature stages of Ae. aegypti on adult nutrient stoichiometry and DENV-1 infection. These findings suggest the potential use of δ¹⁵N as a tool to assess how larval nutritional and competitive environments shape dengue vector competence, with implications for understanding and predicting Ae. aegypti-driven DENV-1 dynamics in urban and suburban areas. Interpretations should consider that female nutrient estimates were partially inferred from male data due to low female sample sizes, survivorship was estimated assuming a 1:1 sex ratio, and some high-mortality treatments lacked surviving adults.