Multi-modal Aedes aegypti mosquito reduction interventions and dengue fever prevention

Objective  To systematically review the effectiveness of biological, chemical and educational dengue fever prevention programs on the reduction of entomologic indicators.
Methods  Searches of PubMed, GoogleScholar, CabDirect databases and reference lists yielded over 1000 articles containing mosquito abatement interventions. Inclusion criteria were: Vector control programs targeting Aedes aegypti and Aedes albopictus mosquitoes; Studies providing pre- and post-test data. Intervention effectiveness was assessed using Mulla's formula to determine percent reductions for all studies with control groups. Twenty-one studies were reviewed.
Results  Twelve dependent variables were presented, however, the Breteau, House and Container indices were the primary measurement tools for monitoring larval populations. Behavioural methods consisting of educational campaigns and maintaining water containers to reduce the mosquito population were applied in eight studies. Eight studies involved the use of biological methods such as predatory organisms or bacteria. Finally, eight studies used chemical control techniques including insecticide sprays, larvicides, insecticide-treated materials, and cleaning water of containers with household chemicals with three studies using a combination of intervention techniques. Post-intervention reduction in entomologic indices ranged from 100% to an increase of 13.9% from baseline.
Conclsuion  Little evidence exists to support the efficacy of mosquito abatement programs owing to poor study designs and lack of congruent entomologic indices. Creation of a standard entomological index, use of clustered and randomized-controlled trials, and testing the generalizability of proven methods are recommended for future research.     

The development of predictive tools for pre‐emptive dengue vector control: a study of Aedes aegypti abundance and meteorological variables in North Queensland,Australia

Objectives To describe the meteorological influences on adult dengue vector abundance in Australia for the development of predictive models to trigger pre‐emptive control operation. Methods Multiple linear regression analyses were performed using meteorological data and female Aedes aegypti collection data from BG‐Sentinel Mosquito traps placed at 11 monitoring sites in Cairns, north Queensland. Results Considerable regression coefficients (R² = 0.64 and 0.61) for longer‐ and shorter‐term factor models respectively were derived. Longer‐term factors significantly associated with abundance of adult vectors were mean minimum temperature (lagged 6 month) and mean daily temperature (lagged 4 month), explaining the predictable increase in abundance during the wet season. Factors explaining fluctuation in abundance in the shorter term were mean relative humidity over the previous 2 week and current daily average temperature. Rainfall variables were not found to be strong predictors of A. aegypti abundance in either longer‐ or shorter‐term models. Conclusions The implications of these findings for the development of useful predictive models for vector abundance risks are discussed. Such models can be used to guide the application of pre‐emptive dengue vector control, and thereby enhance disease management.     

Association of human immune response to Aedes aegypti salivary proteins with dengue disease severity

Dengue viruses (DENV; family Flaviviridae, genus Flavivirus) are transmitted by Aedes aegypti mosquitoes and can cause dengue fever (DF), a relatively benign disease, or more severe dengue haemorrhagic fever (DHF). Arthropod saliva contains proteins delivered into the bite wound that can modulate the host haemostatic and immune responses to facilitate the intake of a blood meal. The potential effects on DENV infection of previous exposure to Ae. aegypti salivary proteins have not been investigated. We collected Ae. aegypti saliva, concentrated the proteins and fractionated them by nondenaturing polyacrylamide gel electrophoresis (PAGE). By the use of immunoblots, we analysed reactivity with the mosquito salivary proteins (MSP) of sera from 96 Thai children diagnosed with secondary DENV infections leading either to DF or DHF, or with no DENV infection, and found that different proportions of each patient group had serum antibodies reactive to specific Ae. aegypti salivary proteins. Our results suggest that prior exposure to MSP might play a role in the outcome of DENV infection in humans.     

Aedes aegypti in French Guiana: susceptibility to a dengue virus

Twenty-seven samples of Aedes aegypti (F1 generation) from French Guiana were tested for their susceptibility to dengue serotype 2 virus. Very high infection rates were observed by indirect fluorescent antibody (IFA) test. Ae. aegypti samples were pooled according to two groups: the first group (N=10) represented mosquitoes from the urbanized area of Cayenne and surroundings, and the second group (N=17) corresponded to mosquitoes collected in the countryside. Infection rates were found to be similar in these two cases. These findings are discussed in relation with the history of Ae. aegypti in this part of the world.     

Genetic heterogeneity of the dengue vector Aedes aegypti in Martinique

In Martinique, Aedes aegypti, the vector of dengue viruses has been the target of insecticide control for more than 35 years. Despite significant control efforts, dengue has become a major disease of public health concern. We conducted a population genetic analysis based on isoenzyme variations combined with an estimation of infection rate to a dengue virus among 26 Ae. aegypti samples. Aedes aegypti samples could be differentiated for their susceptibility to dengue infection (infection rates ranging from 42.8% to 98.6%) and showed important genetic variation (significant F(ST) values).