Field experiments of Anopheles gambiae attraction to local fruits/seedpods and flowering plants in Mali to optimize strategies for malaria vector control in Africa using attractive toxic sugar bait methods

Abstract

BackgroundBased on recent studies in Israel demonstrating that attractive toxic sugar bait (ATSB) methods can be used to decimate local anopheline and culicine mosquito populations, an important consideration is whether the same methods can be adapted and improved to attract and kill malaria vectors in Africa. The ATSB approach uses fruit or flower scent as an attractant, sugar solution as a feeding stimulant, and an oral toxin. The ATSB solutions are either sprayed on vegetation or suspended in simple bait stations, and the mosquitoes ingesting the toxic solutions are killed. As such, this approach targets sugar-feeding female and male mosquitoes. This study examines the attractiveness of African malaria vectors to local fruits/seedpods and flowering plants, key biological elements of the ATSB approach for mosquito control.MethodsThree field experiments were conducted at sites in Mali. The attraction of Anopheles gambiae s.l. to 26 different local fruits and seedpods was determined at a site in the semi-arid Bandiagara District of Mali. Wire mesh glue traps with fruits/seedpods suspended on skewers inside were set along a seasonal lagoon. Seven replicates of each fruit/seedpod species were tested, with a water-soaked sponge and a sugar-soaked sponge as controls. The attraction of An. gambiae s.l. to 26 different types of flowering plants was determined at a site near Mopti in Mali. The flowering plants held in a water-filled buried container were tested using the same glue traps, with controls including water only and sugar solution. Six replicates of each selected plant type were tested on transects between rice paddies. Additional studies using CDC light traps were done to determine the relative densities and periodicity of An. gambiae s.l. attraction to branches of the most highly attractive flowering plant, branches without flowers, human odor, and candescent light.ResultsOf the 26 fruits and seedpods tested, 6 were attractive to An. gambiae s.l. females and males, respectively. Guava (Psidium guajava) and honey melon (Cucumis melo) were the two most attractive fruits for both females and males. Of the 26 flowering plants tested, 9 were significantly attractive for females, and 8 were attractive for males. Acacia macrostachya was the most attractive flowering plant. Periodicity studies using this plant showed peaks of An. gambiae s.l. attraction between 1930 and 2200 h and 0400-0500 h, which differed considerably from the response to human odors, which expectedly peaked at around midnight.ConclusionThese field experiments in Mali highlight that female and male An. gambiae s.l. have pronounced differences in attraction for diverse types of indigenous fruits/seedpods and flowering plants. The identification of attractive fruits and seedpods shows that a variety of indigenous and locally abundant natural products could potentially be used as juices to make ATSB solution for mosquito control. As well, the simple methods used to identify the most attractive flowering plants provide valuable insights into the natu...

Dry season reproductive depression of Anopheles gambiae in the Sahel

“…The low blood feeding response in late October-November coincides with the apparent disappearance of the M form (Adamou et al, 2011; Lehmann et al, 2010) from indoor collections. Presumably these mosquitoes fly to unknown shelters and feed on plants (Muller et al, 2010) as proposed by (Huestis et al, 2011). On the other hand, the relative scarcity of unfed females during the dry season suggests that those females which do enter houses are highly intent on blood feeding.…”

Efficient attractants and simple odor-baited sticky trap for surveillance of Anopheles arabiensis Patton mosquito in Ethiopia

“…The combination of guava fruit with CO 2 caught a smaller number of mosquitoes when compared to CO 2 alone. According to a study in Mali, guava fruit was the most attractive fruit for both female and male A.gambiaes [26]. The difference of guava fruits may be the possible reason for the unparalleled efficacy.…”

Seasonal variation in metabolic rate, flight activity and body size of Anopheles gambiae in the Sahel

“…The abundance of sugar sources (e.g. Müller et al, 2010), blood and water (around houses and in wells) probably relaxes the constraints imposed by limited food and water typically available to diapausing insects. Consistent with this, we (Yaro et al, 2012) found that reproductive physiology, but not blood-feeding response, was depressed during the dry season in Sahelian M-form A. gambiae.…”

“…These results indicate that these relatively small individuals surviving until the end of the dry season (April-May) have greater nutritional reserves (relative to their body size) than do mosquitoes at other times of the year. Considering the abundance of flowers and fruits during the dry season (Müller et al, 2010), continued availability of human hosts and the hospitable temperature range, mosquitoes may amass nutritional reserves until they can later allocate them to reproduction. It is possible that these seasonal shifts in body size are mostly due to the drying of larval sites at the end of the wet season, which in turn affects larval density and thus food availability and larval growth patterns, as it is well known that growing conditions affect adult size (Lanciani, 1992;Fischer and Fiedler, 2002;Chown and Klok, 2003;Aboagye-Antwi and Tripét, 2010;Russell et al, 2011).…”