Variation of Vectorial Capacity and Life History Traits of Aedes aegypti; Main Vector for Dengue Transmission with Larval Diet Concentration

Abstract

Vectorial capacity (VC) is the number of new infections disseminated per case per day by an insect vector. There are several attempts define the VC of disease vectors. Mathematical approximation using different biological parameters is one such approaches. Therefore, the present investigation was carried out to assess the effect of larval diet concentration on vector bionomic and vectorial capacity of Aedes aegypti in Sri Lanka. A batch of 400 first instar larvae of Ae. aegypti in 100 ml of water were exposed to three different concentrations (6%, 8% and 10%) of larval diet, made with tuna meal (12.5g), bovine liver powder (9.0g), brewer’s yeast (3.5g). The effect of larval diet concentration on different biological parameters of larvae (mortality rate, survival rate), pupae (mortality rate, survival rate, pupation success), adult (mortality rate, longevity and fecundity of adults) and selected morphometric characters at each stage with respect to diet concentration were recorded. The whole experiment setup was repeated five times. Vectorial capacities for each diet treatment were calculated using VC= ma2pn/-logeP mathematical approximation. There was a significant effect of larval diet on most of larval growth parameters including head length (F4,14 = 29.599; P<0.05), head width (F4, 14 = 20.797; P<0.05), thoracic width (F4, 14 = 55.924; P<0.05), abdominal length (F4, 14 = 10.381; P<0.05), abdominal width (F4, 14 = 7.239; P<0.05) and total length (F4, 14 = 20.797; P<0.05). Most of larval growth parameters were varied significantly with different larval dietary concentrations including thoracic length (F4, 14 = 4.662; P<0.05), abdominal length (F4, 14 = 12.452; P<0.05), abdominal width (F4, 14 = 5.890; P<0.05) and wing length (F4,14 =7.001; P<0.05) of sexes, except thoracic width (F4, 14 = 2.469; P>0.05). Further, biting frequency (F4, 14 = 47.50; P<0.05), fecundity (F4, 14 = 18.33; P<0.05) and survival rate (F4, 14 = 3.61; P<0.05) of adult female, significantly varied with different larval diet concentrations. However, the longevity of adults (F4, 14 = 0. 591; P>0.05) was not correlated significantly with larval food availability. The highest VC (196.37 ± 29.92) were observed from 10% larval treatment followed by 8% (27.30 ± 4.47). The VC of adult Ae. aegypti differed significantly (F4, 14 = 24.048; P=0.014, at 95% level of confidence) among the different larval diet concentrations. Therefore, it is required to document the environmental variation at the larval stages in order to understand transmission dynamics and control of dengue in Sri Lanka.