Microbial control of arthropod-borne disease

Arthropods harbor a diverse array of microbes that profoundly influence many aspects of host biology, including vector competence. Additionally, symbionts can be engineered to produce molecules that inhibit pathogens. Due to their intimate association with the host, microbes have developed strategies that facilitate their transmission, either horizontally or vertically, to conspecifics. These attributes make microbes attractive agents for applied strategies to control arthropod-borne disease. Here we discuss the recent advances in microbial control approaches to reduce the burden of pathogens such as Zika, Dengue and Chikungunya viruses, and Trypanosome and Plasmodium parasites. We also highlight where further investigation is warranted.

Haematophagy and Opportunities for Symbiotic Control of Insect Vectors of Human Protozoan Diseases.

Insect vector-symbiotic relationships are widely reported in literature with several microorganisms reported to play a key role in growth, development, survival and evolutionary success of insect disease vectors. Symbiotic bacteria are prevalent in insects like mosquitoes, sand flies, tsetse flies that are known efficient vectors of tropical diseases. Several studies have been undertaken to determine the mechanisms of the insect host-symbiotic relationships with the aim of developing new strategies to control human vector borne diseases. Some bacterial symbionts have evolved together with the respective insect hosts such that the hosts cannot survive without them. This is the basis of an intervention strategy known as symbiotic control. It is a recent multi-pronged approach that targets symbiotic microorganisms to control insect disease vectors and possibly interfere with their vectorial capacity. The strategy is promising and has recently generated a lot of research interest. Three such approaches have been reported and are: the interference and destabilization of microbial symbionts essential for insect vector survival; changing the genetic make-up of symbionts so that they generate and express anti-parasite agents within the insect host; and the introduction of other microorganisms that may eventually negatively affect the longevity and vector competence of the offspring in future populations. The availability of new molecular techniques has made the understanding of symbiotic relationships more clear. With sustained and increasing research interest and recent findings in insect-symbiotic associations, there is high possibility that soon we will have many insect-vector control programs utilizing this information and techniques. In this review we highlight the evolution of blood feeding behavior in insect disease vectors, new findings and developments on microbial symbiosis in mosquitoes, sand flies, triatomine bugs and tsetse flies that are feasible and therefore form basis for formulating symbiotic control strategies for major human insect borne parasitic protozoan diseases: malaria, leishmaniasis and trypanosomiasis.

Metagenomics, paratransgenesis and the Anopheles microbiome: a portrait of the geographical distribution of the anopheline microbiota based on a meta-analysis of reported taxa

Anophelines harbour a diverse microbial consortium that may represent an extended gene pool for the host. The proposed effects of the insect microbiota span physiological, metabolic and immune processes. Here we synthesise how current metagenomic tools combined with classical culture-dependent techniques provide new insights in the elucidation of the role of the Anopheles-associated microbiota. Many proposed malaria control strategies have been based upon the immunomodulating effects that the bacterial components of the microbiota appear to exert and their ability to express anti-Plasmodium peptides. The number of identified bacterial taxa has increased in the current “omics” era and the available data are mostly scattered or in “tables” that are difficult to exploit. Published microbiota reports for multiple anopheline species were compiled in an Excel® spreadsheet. We then filtered the microbiota data using a continent-oriented criterion and generated a visual correlation showing the exclusive and shared bacterial genera among four continents. The data suggested the existence of a core group of bacteria associated in a stable manner with their anopheline hosts. However, the lack of data from Neotropical vectors may reduce the possibility of defining the core microbiota and understanding the mosquito-bacteria interactive consortium.