Field-collected mosquitoes of the two main malaria vectors in Africa, Anopheles gambiae sensu lato and Anopheles funestus, were screened for their midgut bacterial contents. The midgut from each blood-fed mosquito was screened with two different detection pathways, one culture independent and one culture dependent. Bacterial species determination was achieved by sequence analysis of 16S rRNA genes. Altogether, 16 species from 14 genera were identified, 8 by each method. Interestingly, several of the bacteria identified are related to bacteria known to be symbionts in other insects. One isolate, Nocardia corynebacterioides, is a relative of the symbiont found in the vector for Chagas' disease that has been proven useful as a paratransgenic bacterium. Another isolate is a novel species within the ␥-proteobacteria that could not be phylogenetically placed within any of the known orders in the class but is close to a group of insect symbionts. Bacteria representing three intracellular genera were identified, among them the first identifications of Anaplasma species from mosquitoes and a new mosquito-Spiroplasma association. The isolates will be further investigated for their suitability for a paratransgenic Anopheles mosquito.Malaria remains the parasitic disease that kills the most people in the world. Anopheles gambiae sensu lato and Anopheles funestus mosquitoes are the main vectors in Africa, where 90% of malaria-related deaths occur. An approach to stop malaria transmission is paratransgenics. In this approach, suitable symbiotic bacteria are genetically modified to produce an antiparasitic factor and then reintroduced into the insect gut, where they kill or inhibit the development of the parasites (4).A few studies have been performed to investigate bacterial species in field-collected Anopheles mosquitoes, all using culturing techniques. Jadin et al. (22) To identify bacterial candidates for a paratransgenic mosquito, we conducted a screen for uncultured and cultured midgut bacteria from wild-caught A. gambiae and A. funestus mosquitoes. MATERIALS AND METHODSField site, mosquitoes, and dissections. Indoor-resting, blood-fed female A. gambiae sensu lato and A. funestus mosquitoes were caught in Lwanda, 12 km east of Mbita Point Research and Training Centre, ICIPE, Suba district, Western Kenya. In total, 116 Anopheles mosquitoes were caught on eight different occasions (A2 to H2). Living mosquitoes were anesthetized with chloroform, the species were determined by morphology and PCR (A. gambiae sensu lato) (30a). The mosquitoes were dissected in a sterile hood. Individual midguts were mashed in 50 l of sterile saline (0.9% NaCl); this suspension was later used for isolation of bacteria and cloning of the 16S rRNA gene from bacteria. Controls for the efficiency of sterilization were treated like the other samples.Bacterial isolation and phenotypic characterization. The midgut suspension was streaked on Luria-Bertani agar (LA) plates and incubated for 48 h at room temperature. All bacteria were restreaked and pre...

BackgroundMost cases of human African trypanosomiasis (HAT) start with a bite from one of the subspecies of Glossina fuscipes. Tsetse use a range of olfactory and visual stimuli to locate their hosts and this response can be exploited to lure tsetse to insecticide-treated targets thereby reducing transmission. To provide a rational basis for cost-effective designs of target, we undertook studies to identify the optimal target colour.Methodology/Principal FindingsOn the Chamaunga islands of Lake Victoria , Kenya, studies were made of the numbers of G. fuscipes fuscipes attracted to targets consisting of a panel (25 cm square) of various coloured fabrics flanked by a panel (also 25 cm square) of fine black netting. Both panels were covered with an electrocuting grid to catch tsetse as they contacted the target. The reflectances of the 37 different-coloured cloth panels utilised in the study were measured spectrophotometrically. Catch was positively correlated with percentage reflectance at the blue (460 nm) wavelength and negatively correlated with reflectance at UV (360 nm) and green (520 nm) wavelengths. The best target was subjectively blue, with percentage reflectances of 3%, 29%, and 20% at 360 nm, 460 nm and 520 nm respectively. The worst target was also, subjectively, blue, but with high reflectances at UV (35% reflectance at 360 nm) wavelengths as well as blue (36% reflectance at 460 nm); the best low UV-reflecting blue caught 3× more tsetse than the high UV-reflecting blue.Conclusions/SignificanceInsecticide-treated targets to control G. f. fuscipes should be blue with low reflectance in both the UV and green bands of the spectrum. Targets that are subjectively blue will perform poorly if they also reflect UV strongly. The selection of fabrics for targets should be guided by spectral analysis of the cloth across both the spectrum visible to humans and the UV region.

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Tsetse flies, which transmit sleeping sickness to humans and nagana to cattle, are commonly controlled by stationary artificial baits consisting of traps or insecticide-treated screens known as targets. In Kenya the use of electrocuting sampling devices showed that the numbers of Glossina fuscipes fuscipes (Newstead) visiting a biconical trap were nearly double those visiting a black target of 100 cm×100 cm. However, only 40% of the males and 21% of the females entered the trap, whereas 71% and 34%, respectively, alighted on the target. The greater number visiting the trap appeared to be due to its being largely blue, rather than being three-dimensional or raised above the ground. Through a series of variations of target design we show that a blue-and-black panel of cloth (0.06 m2) flanked by a panel (0.06 m2) of fine black netting, placed at ground level, would be about ten times more cost-effective than traps or large targets in control campaigns. This finding has important implications for controlling all subspecies of G. fuscipes, which are currently responsible for more than 90% of sleeping sickness cases.