- What is known about the subject?
Besides causing irritating bites, mosquitoes play a central role in public health as main vectors (transmitters) of pathogens responsible for serious diseases. There are different species in our environment, native and invasive, able to transmit pathogens to humans and other animals. Among them, the common house mosquito (Culex pipiens) is a vector of numerous viruses and other parasites including West Nile Virus responsible for significant encephalitis outbreaks in Spain in recent years.
Mosquitoes have complex life cycles including aquatic stages as larvae and pupae before reaching their adult stage where they develop their haematophagous behaviour. During these immature stages, mosquitoes are exposed to different pollutants present in mosquito breeding waters. These pollutants include human and livestock pharmaceutical residues. Among these, antibiotics are capable of altering mosquitoes’ gut microbiota, that is, the microbial community inhabiting their gut. This is particularly relevant in the capacity of mosquitoes to transmit diseases because of the potential effects of this microbiota on mosquitoes’ survival and activation of the immune system.
- What does this study add to the existing literature?
This study aimed to identify the impact of antibiotic exposure during larval and adult stages on the survival rate of adult male and female common house mosquitoes. To this end, we used an experimental approach in which wild-collected Cx pipiens larvae were exposed to an antibiotic cocktail in the laboratory or were reared in water free of antibiotics. Emerged adults (for whom we controlled time of emergence) from both groups of treatment were subsequently fed with sugar solution supplemented with antibiotics or fed only with sugar solution. By doing so, we aimed to identify the role of antibiotic exposure during the different development stages of mosquitoes on the survival of adults, i.e. the time they had to bite and develop pathogens inside their organisms.
We observed that larval exposure to antibiotics significantly increased the survival rate of adult female mosquitoes, which is particularly relevant considering the fact that they are the only haematophagous sex, i.e. they feed on blood. In terms of adult exposure to antibiotics, the survival effects depended on the time of emergence and, hence, the number of days fed with ad libitum during larval stage. Precisely, as larval ad libitum feeding period shortened, antibiotic exposure had a more negative effect on the survival of adult mosquitoes, thereby evidencing that the nutritional status during these mosquitoes’ development may have potential consequences in adult stages.
- What are the implications of the findings?
The alteration of the microbiota of mosquitoes due to antibiotic exposure during their different development stages represents a significant impact on a key component of the vectorial capacity, the vector survival rate. While limited by the laboratory conditions involved, our study shows that antibiotic exposure of common house mosquitoes can affect their survival rate. In particular, the presence of antibiotics in aquatic habitats where mosquito larvae rear could increase emerged adult mosquitoes’ survival rate, thus increasing the opportunities to bite animals and humans, and therefore transmitting pathogens. This study clearly opens new questions that need to be addressed in the future to identify the mechanisms underlying these results and their epidemiological consequences.
Marta Garrigós
Predoctoral fellow. Department of Parasitology
Faculty of Pharmacy
University of Granada