Differential attractiveness of human foot odours to Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) and variation in their chemical composition.

Counter flow geometry (CFG) traps (American Biophysics) baited with foot odours (adsorbed overnight on a combination of a nylon and a cotton socks) from 4 groups of 4 male volunteers were initially used in a screen-house to compare and grade the attractiveness of Anopheles gambiae Giles sensu stricto to these odours. Ten individuals were then selected from the 4 groups for further grading in which mosquito attractiveness to odours adsorbed on socks worn by each of the individuals was compared against a control (clean, un-worn cotton and nylon socks). A gradation of attractiveness was found, with the most attractive foot odour catching 8-fold more mosquitoes than the least attractive one (t-test, p=0.001). For comparison of the chromatographic profiles of the foot odours and identification of their constituents, six adsorbents (tenax, chromsorb, porapak Q, activated charcoal, reverse phase octadecyl and octyl bonded silica) were evaluated for their suitability in trapping the volatiles in a static mode. Of these, porapak Q was found to be the most effective. Comparison of the gas-chromatographic (GC) and gas chromatography-linked mass spectrometry (GC-MS) profiles of blends collected from the most and least attractive feet on porapak Q adsorbent revealed both qualitative and quantitative differences. The implication of our finding on differential attraction of An. gambiae to their preferred feeding site of different human subjects is highlighted.

Antiplasmodial, anti-trypanosomal, anti-leishmanial and cytotoxicity activity of selected Tanzanian medicinal plants.

The antiplasmodial, anti-trypanosomal and anti-leishmanial activity of 25 plant extracts obtained from seven Tanzanian medicinal plants: Annickia (Enantia) kummeriae (Annonaceae), Artemisia annua (Asteraceae), Pseudospondias microcarpa (Anacardiaceae), Drypetes natalensis (Euphorbiaceae), Acridocarpus chloropterus (Malpighiaceae), Maytenus senegalensis (Celastraceae) and Neurautanenia mitis (Papilonaceae), were evaluated in vitro against Plasmodium falciparum K1, Trypanosoma brucei rhodesiense STIB 900 and axenic Leishmania donovani MHOM-ET-67/82. Out of the 25 extracts tested, 17 showed good antiplasmodial activity (IC50 0.04-5.0 microg/ml), 7 exhibited moderate anti-trypanosomal activity (IC50 2.3-2.8 microg/ml), while 5 displayed mild anti-leishmanial activity (IC50 8.8-9.79 microg/ml). A. kummeriae, A. annua, P. microcarpa, D. natalensis, M. senegalensis and N. mitis extracts had good antiplasmodial activity (IC50 0.04-2.1 microg/ml) and selectivity indices (29.2-2,250 microg/ml). The high antiplasmodial, moderate anti-trypanosomal and mild anti-leishmanial activity make these plants good candidates for bioassay-guided isolation of anti-protozoal compounds which could serve as new lead structures for drug development.

The in vitro anti-plasmodial and in vivo anti-malarial efficacy of combinations of some medicinal plants used traditionally for treatment of malaria by the Meru community in Kenya.

The use of herbal drugs as combinations has existed for centuries in several cultural systems. However, the safety and efficacy of such combinations have not been validated. In this study, the toxicity, anti-plasmodial and antimalarial efficacy of several herbal drug combinations were investigated. Lannea schweinfurthii, Turraea robusta and Sclerocarya birrea, used by traditional health practitioners in Meru community, were tested for in vitro anti-plasmodial and in vivo anti-malarial activity singly against Plasmodium falciparum and Plasmodium berghei, respectively. Methanolic extract of Turraea robusta was the most active against Plasmodium falciparum D6 strain. Aqueous extracts of Lannea schweinfurthii had the highest anti-plamodial activity followed by Turraea robusta and Sclerocarya birrea. D6 was more sensitive to the plant extracts than W2 strain. Lannea schweinfurthii extracts had the highest anti-malarial activity in mice followed by Turraea robusta and Sclerocarya birrea with the methanol extracts being more active than aqueous ones. Combinations of aqueous extracts of the three plants and two others (Boscia salicifolia and Rhus natalensis) previously shown to exhibit anti-plasmodial and anti-malarial activity singly were tested in mice. Marked synergy and additive interactions were observed when combinations of the drugs were assayed in vitro. Different combinations of Turraea robusta and Lannea schweinfurthii exhibited good in vitro synergistic interactions. Combinations of Boscia salicifolia and Sclerocarya birrea; Rhus natalensis and Turraea robusta; Rhus natalensis and Boscia salicifolia; Turraea robusta and Sclerocarya birrea; and Lannea schweinfurthii and Boscia salicifolia exhibited high malaria parasite suppression (chemo-suppression >90%) in vivo when tested in mice. The findings are a preliminary demonstration of the usefulness of combining several plants in herbal drugs, as a normal practice of traditional health practitioners.

Livestock farmers' perception and epidemiology of bovine trypanosomosis in Kwale District, Kenya.

We did cross-sectional surveys in Kwale District, Kenya to determine the epidemiology of bovine trypanosomosis and livestock owners' perceptions of the disease. The surveys involved relative importance of trypanosomosis, examination of the current disease constraints, current control practices and drug-use patterns. Informal meetings were held with farmers and cattle census undertaken. Tsetse-fly densities and trypanosomosis prevalences in cattle were determined. A total of 132 farmers were interviewed. Trypanosomosis, anaplasmosis, East Coast fever, foot-and-mouth diseases were reported to be the major constraints to livestock production. Trypanosomosis was the most important compared to other diseases. Chemotherapy was the most widely used method of controlling the disease. Farmer-based tsetse-control technologies were poorly adopted. Respondents were quite knowledgeable on the symptoms, causes and treatment of trypanosomosis. Glossina austeni, G. brevipalpis and G. pallidipes were found in the area; the latter was the most common (0.2-738 flies/trap). Trypanosoma congolense and T. vivax were found in cattle with the former more prevalent. Infection prevalences in cattle varied between 0 and 25% (median: 22%).

Anti-plasmodial activity and toxicity of extracts of plants used in traditional malaria therapy in Meru and Kilifi Districts of Kenya.

The methanol and aqueous extracts of 10 plant species (Acacia nilotica, Azadirachta indica, Carissa edulis, Fagaropsis angolensis, Harrissonia abyssinica, Myrica salicifolia, Neoboutonia macrocalyx, Strychnos heningsii, Withania somnifera and Zanthoxylum usambarensis) used to treat malaria in Meru and Kilifi Districts, Kenya, were tested for brine shrimp lethality and in vitro anti-plasmodial activity against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum (NF54 and ENT30). Of the plants tested, 40% of the methanol extracts were toxic to the brine shrimp (LD(50)<100micro/ml), while 50% showed in vitro anti-plasmodial activity (IC(50)<100microg/ml). The methanol extract of the stem bark of N. macrocalyx had the highest toxicity to brine shrimp nauplii (LD(50) 21.04+/-1.8microg/ml). Methanol extracts of the rest of the plants exhibited mild or no brine shrimp toxicity (LD(50)>50microg/ml). The aqueous extracts of N. macrocalyx had mild brine shrimp toxicity (LD(50) 41.69+/-0.9microg/ml), while the rest were lower (LD(50)>100microg/ml). The methanol extracts of F. angolensis and Zanthoxylum usambarense had IC(50) values <6microg/ml while the aqueous ones had values between 6 and 15microg/ml, against both chloroquine-sensitive and resistant P. falciparum strains. The results support the use of traditional herbs for anti-malarial therapy and demonstrate their potential as sources of drugs.

Fumigant toxicity of the essential oils of some African plants against Anopheles gambiae sensu stricto.

The essential oils from 15 species of African plants selected by ethnobotanical considerations and field inspection (odour and presence of insects) were screened for fumigant toxicity to Anopheles gambiae s.s. in the laboratory. Essential oils from 6 species showed varying levels of toxicity, with Conyza newii (Compositae) and Plectranthus marruboides (Labiateae) being the most potent. Fifty compounds representing approximately 74% of the essential oil of C. newii were identified by GC-MS and GC-coinjection (for available standards). The major and some of the minor constituents of the two oils were assayed at different doses. Two compounds, from C. newii, perillaldehyde and perillyl alcohol, exhibited higher fumigant toxicity (LD50 = 1.05 x 10(-4) and 2.52 x 10(-4) mg cm(-3), respectively) than the parent oil (2.0 x 10(-3) mg cm(-3)). GC-MS analysis of the essential oil of P. marruboides gave results similar to that previously reported. Interestingly, none of its components were active, suggesting that the insecticidal activity of the oil results from either some of the minor components or as a blend effect of some of the major constituents.

Anti-plasmodial activity of some Kenyan medicinal plant extracts singly and in combination with chloroquine.

Sixty organic and aqueous extracts of eleven plants used for the control of malaria by local communities in Kisii District, Kenya were screened for in vitro anti-plasmodial activity. The plants selection was based on existing ethnobotanical information and interviews with local communities. The extracts were tested against chloroquine sensitive and resistant laboratory adapted strains of Plasmodium falciparum. The study revealed that 63.6% of the plants were active (IC50 < or = 100 microg/mL). Extracts of four plants, Ekebergia capensis, Stephania abyssinica, Ajuga remota and Clerodendrum myricoides gave IC50 values below 30 microg/mL against both chloroquine sensitive and resistant P. falciparum strains. Combination of extracts of E. capensis and C. myricoides with chloroquine against the multi-drug resistant P. falciparum isolate (V1/S) revealed synergistic effect. The plants which showed activity may be useful as sources for novel anti-plasmodial compounds.

In vitro antiplasmodial activity of some plants used in Kisii, Kenya against malaria and their chloroquine potentiation effects.

Fifty-five organic and aqueous extracts of 11 plants used in malaria therapy in Kisii District, Kenya were tested in vitro against chloroquine (CQ)-sensitive and resistant strains of Plasmodium falciparum. Of the plants tested, 73% were active (IC(50) < 100 microg/ml). Three plants, Vernonia lasiopus, Rhamnus prinoides and Ficus sur afforded extracts with IC(50) values ranging less than 30 microg/ml against both CQ-sensitive and resistant strains. Combination of some extracts with CQ against the multi-drug resistant P. falciparum isolate V1/S revealed some synergistic effect. The plant extracts with low IC(50) values may be used as sources for novel antimalarial compounds to be used alone or in combination with CQ.

Behavioral and electrophysiological responses of the banana weevilCosmopolites sordidus to host plant volatiles.

Male and femaleCosmopolites sordidus were attracted to freshly cut banana rhizome and pseudostem in a still-air olfactometer. Females responded similarly to odors from a comparatively resistant and from a susceptible cultivar of banana, when presented as either freshly cut tissue or as Porapak-trapped volatiles. Females were also attracted to rotting banana pseudostem and to volatiles collected from it. Males and females gave similar responses to host tissue in both the behavioral bioassay and to collected volatiles in EAG recordings. Weevils did not respond, either behaviorally or electrophysiologically, to a synthetic mixture of mono- and sesqiterpenes, which made up over 9% of the volatiles collected from pseudostem.

Evidence for volatile male-produced pheromone in banana weevilCosmopolites sordidus.

Females of the banana weevil,Cosmopolites sordidus, were attracted to and made longer visits to live conspecific males, trapped volatiles from males, and dissected male hindguts in a still-air olfactometer. Male weevils were attracted to volatiles trapped from males and made longer visits to live males and volatiles from males. Live females, collected volatiles from females and female hindguts, elicited small or no behavioral responses from either sex. Electroantennogram (EAG) responses from both male and female antennae were elicited by collected volatiles from males and by dichloromethane extracts of male hindguts and bodies but not by surface washes of males. No significant EAG responses were given to equivalent material from females. It is therefore suggested that male banana weevils release an aggregation pheromone via their hindgut.