Abstract:
Background: An increasing number of countries in sub-Saharan Africa are moving
towards malaria-elimination, mostly thanks to successful vector control campaigns.
However, elimination has proven challenging, resulting in the persistence of malaria
transmission. It is now accepted that in order to eliminate malaria, new complementary
vector control approaches must be developed. This study describes the development of a
sugar-baited resting place containing a toxic dose of ivermectin for the control of
Anopheles arabiensis.
Results: Dose response experiments were performed in insectary conditions to determine
the LD90 of ivermectin against An. arabiensis. Over 95% of An. arabiensis were
knocked down 48 h post-sugar feeding on 10% sucrose solutions containing 0.01%
ivermectin. When investigating different juices as attractants, it was observed that An.
arabiensis preferred orange, watermelon and commercial guava juice over pawpaw,
tomato, mango or banana, but were most likely to feed on simple 10% sugar solution.
Using recycled materials, different bait prototypes were tested to determine the best
design to maximize sugar feeding. Baits that offered a resting place for the mosquito
rather than just a surface to sugar feed were more likely to attract An. arabiensis to sugar
feed. The optimized prototype was then placed in different locations within a screenhouse, colour-coded with different food dyes, containing competing vegetation (Ricinus
communis) and experimental huts where humans slept under bed nets. Around half of all
the released An. arabiensis sugar fed on the sugar baits, and approximately 50% of all
sugar fed mosquitoes chose the baits close to outdoor vegetation before entering the huts.
Conclusions: Ivermectin is an effective insecticide for use in sugar baits. The design of
the sugar bait can influence feeding rates and, therefore, efficacy. Sugar baits that offer a
resting surface are more efficient and sugar feeding on the baits is maximized when these
are placed close to peri-domestic vegetation. Attractive toxic sugar baited resting places
may provide an additional vector control method to complement with existing strategies.