Influence of bacterial strains on oviposition and larval development of two BTV vector species of Culicoides (Diptera: Ceratopogonidae): an approach to colony establishment

The biting midges, Culicoides peregrinus Kieffer and Culicoides oxystoma
Kieffer (Diptera: Ceratopogonidae) are the most significant vector species
of bluetongue virus (BTV) in the Oriental region, including India. Rearing
of these vector species was cumbersome; previous researchers supplemented
the rearing substrates primarily with cattle dung (the habitat), yeast,
and nutrient broth. Other investigations reiterated that an enriched
milieu of live bacteria is required for the oviposition and developmental
progression of the immatures, as they failed to develop in sterile medium.
Therefore, bacteria-based approaches provide novel opportunities for
artificial rearing. This investigation tries to simplify and create a
cleaner version of rearing based on different bacterial strains. The
substrate bacterial strains were biochemically characterized, and their
influence on oviposition, hatching, and larval development was analyzed
and evaluated under laboratory conditions. We artificially reared two
vector species by utilizing three different strains of Bacillus cereus and
one strain of Alcaligenes faecalis retrieved from the substrates. The
results demonstrated that gravid females select their oviposition
substrates based on stimuli derived from live microorganisms that indicate
the suitability of the developmental substrate for immature development.
Bacillus cereus 1B stimulated the greatest extent of egg hatching
(>99%), larval survivability (>74%), Pupae formation
(>83%), and adult emergence (>98%) in both species. This
present investigation proposes to utilize the B. cereus 1B as an
alternative approach to artificially rear and establish laboratory
colonies of these vector species.