Abstract:
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.