Size alters susceptibility of vectors to dengue virus infection and dissemination

Abstract

The size of arthropod vectors may affect their ability to transmit pathogens. Here we test the hypothesis that body size alters the susceptibility of Aedes aegypti and Aedes albopictus mosquitoes to dengue virus (DENV) infection and subsequent dissemination throughout the body of the mosquito. After feeding on blood containing known quantities of virus, smaller-sized females were significantly more likely to become infected and to disseminate virus than larger individuals. The effects of size were stronger for Ae. aegypti and independent of rearing conditions. Ae. albopictus was more susceptible to DENV infection and had higher virus titer in the body than Ae. aegypti, yet infected Ae. aegypti disseminated DENV more readily than infected Ae. albopictus. These results are consistent with the concept that Ae. aegypti is a more competent vector of DENV and emphasize the importance of body size in determining adult infection parameters.

FIGURE 1

Least squares means (SE) for sizes of adult Aedes mosquitoes in different states of DENV-2 infection (uninfected [no virus detected], positively infected [non-disseminated infection], and positively infected [disseminated infection]). Some replicates for Ae. albopictus treatments had all mosquitoes infected with dengue virus (100% infection in 6 of 21 replicates). These results did not yield information on sizes of uninfected mosquitoes. The design was un-balanced so least squares means are reported. Pooled over mosquito species (A and B), an analysis of variance showed that uninfected mosquitoes were significantly larger than mosquitoes with disseminated dengue virus infections. Also, Ae. aegypti were significantly larger than Ae. albopictus (see Results section). Sample sizes are indicated above each bar.

FIGURE 2

Mean (per replicate) size and body titer for Ae. aegypti and Ae. albopictus mosquitoes with disseminated dengue virus infections. Line drawn through means shows the best-fit linear regression for Ae. aegypti (intercept [SE] =–0.4177 [1.5941]; slope [SE] = 1.5379 [0.5997]; r² = 0.2571, F_1,19 = 6.58, P= 0.0190). No significant size by body titer relationship was observed for Ae. albopictus (intercept [SE] = 1.3232 [2.0153]; slope [SE] 0.9902 [0.7807], r² = 0.0820, F_1,18 = 1.61, P = 0.2209).