She’s a femme fatale: low-density larval development produces good disease vectors

Abstract

Two hypotheses for how conditions for larval mosquitoes affect vectorial capacity make opposite predictions about the relationship of adult size and frequency of infection with vector-borne pathogens. Competition among larvae produces small adult females. The competition-susceptibility hypothesis postulates that small females are more susceptible to infection and predicts frequency of infection should decrease with size. The competition-longevity hypothesis postulates that small females have lower longevity and lower probability of becoming competent to transmit the pathogen and thus predicts frequency of infection should increase with size. We tested these hypotheses for Aedes aegypti in Rio de Janeiro, Brazil, during a dengue outbreak. In the laboratory, longevity increases with size, then decreases at the largest sizes. For field-collected females, generalised linear mixed model comparisons showed that a model with a linear increase of frequency of dengue with size produced the best Akaike’s information criterion with a correction for small sample sizes (AICc). Consensus prediction of three competing models indicated that frequency of infection increases monotonically with female size, consistent with the competition-longevity hypothesis. Site frequency of infection was not significantly related to site mean size of females. Thus, our data indicate that uncrowded, low competition conditions for larvae produce the females that are most likely to be important vectors of dengue. More generally, ecological conditions, particularly crowding and intraspecific competition among larvae, are likely to affect vector-borne pathogen transmission in nature, in this case via effects on longevity of resulting adults. Heterogeneity among individual vectors in likelihood of infection is a generally important outcome of ecological conditions impacting vectors as larvae.

Ecología de Aedes aegypti y Aedes albopictus en América y la transmisión de enfermedades

“…aegypti. Esta situación es complicada porque los mosquitos pequeños son más propensos a la infección y la diseminación del DENV que los de mayor tamaño (41), pero la mayor propensión a la infección y la diseminación de vectores más pequeños pueden obviarse dada su menor vida útil (49). Debido a que la competencia tiende a disminuir el tamaño del mosquito adulto (50), se hace difícil diferenciar entre efectos directos de la competencia y efectos indirectos causados por la reducción en el tamaño de los mosquitos.…”

Larval interference competition between the native Neotropical mosquito Limatus durhamii and the invasive Aedes aegypti improves the fitness of both species

“…Yet, another factor, vector competence, is of importance for mosquitoes because it can be influenced by plastic responses in the life history traits induced by larval competition (Alto et al ., ). According to the competitive‐susceptibility hypothesis, vector competence is inversely correlated to body size: small females develop and transmit viruses more readily than do large ones (Juliano et al ., ). In the present study Ae.…”

“…aegypti ’s susceptibility to viral infection. Yet, according to the longevity–susceptibility hypothesis, this interaction might actually increase their longevity and thus indirectly increase their capacity to transmit viruses (Juliano et al ., ).…”

Effect of food types on competitive interaction between Aedes aegypti (LINNAEUS, 1762) and Ae. albopictus (SKUSE, 1894) (Diptera, Culicidae): a proximate level appraisal

“…albopictus to a considerable extent (AGNEW et al 2002, JULIANO 2009 and can thus be considered a vital factor for disease transmission potential (ALTO et al 2008a(ALTO et al , 2008b. The disease transmission potential of dengue vectors is linked with the fitness of the mosquitoes (JULIANO et al 2014), reflected through body size and various life history traits that are influenced by larval development and the resources acquired during the larval stages. Resource-based competition in Ae.…”

“…Body size has an immense effect on vector competence, as demonstrated by studies of Ae. aegypti (JULIANO et al 2014) and Aedes triseriatus (PAULSON & HAWLEY 1991). Energy reserves in adult Aedes depend on resource acquisition in the larval stages, which may be affected by nutritional deprivation during larval development.…”