Influence of laboratory, semi-field and field conditions on Aedes albopictus vector competence
Experimental infections of mosquitoes with arboviruses are used to infer the potential role of vector populations in the transmission of diseases. However, the heterogeneity in the design of such studies can affect the results and reproducibility of experiments, making difficult the extrapolation of laboratory results to field conditions and comparisons between studies. Adaptation of mosquito’s colonies to laboratory and rearing conditions is a common step before conducting such studies and can affect the outcome of the research. In this study we aimed to investigate the impact of Aedes albopictus rearing conditions on vector competence. Mosquito eggs were collected from the field and reared over five generations under different temperature and humidity conditions using cages of different size, to get a gradient of conditions from closer to those in nature to those typically used for colony maintenance in the insectary. Females were infected with Chikungunya virus and after 10-14 days saliva, legs/wings and the rest of the body were recovered and analysed by plaque assay. We measured mosquito development and reproductive outputs, and calculated infection, dissemination and transmission rate and transmission efficiency. Results showed that rearing conditions typically used in the laboratory could lead to an overestimation of vector competence, with high values of infection rate and transmission efficiency compared to mosquitoes reared under semi-field conditions. Results also showed a physiological adaptation of mosquitoes to different cage settings, with a higher fecundity measured for insects reared in large outdoor cages and in small cages at static conditions, compared to the other treatments. The outcome of this study highlights the importance of standardizing rearing conditions before conducting vector competence studies and underline the limitations to translate estimates from the laboratory to field conditions.