Field detection of resistance to isometamidium chloride and diminazene aceturate in Trypanosoma vivax from the region of the Boucle du Mouhoun in Burkina Faso.

A longitudinal study assessed the chemoresistance to isometamidium chloride (ISM) and diminazene aceturate (DA) in the region of the Boucle du Mouhoun in Burkina Faso. A preliminary cross-sectional survey allowed the identification of the 10 villages with the highest parasitological prevalences (from 2.1% to 16.1%). In each of these 10 villages, two herds of approximately 50 bovines were selected, one being treated with ISM (1mg/kg b.w.) and the other remaining untreated as control group. All animals (treated and untreated herds) becoming infected were treated with DA (3.5mg/kg b.w.). In total, 978 head of cattle were followed up. Fortnightly controls of the parasitaemia and PCV were carried out during 8 weeks. The main trypanosome species was Trypanosoma vivax (83.6%) followed by Trypanosoma congolense (16.4%). In two villages, less than 25% of the control untreated cattle became positive indicating no need to use prophylactic treatment. These two villages were not further studied. Resistance to ISM was observed in 5 of the remaining 8 villages (Débé, Bendougou, Kangotenga, Mou and Laro) where the relative risk (control/treated hazard ratios) of becoming infected was lower than 2 i.e. between 0.89 (95% CI: 0.43-2.74) and 1.75 (95% CI: 0.57-5.37). In contrast, this study did not show evidence of resistance to DA in the surveyed villages with only 8.6% (n=93) of the cattle relapsing after treatment. Our results suggest that because of the low prevalence of multiple resistances in the area a meticulous use of the sanative pair system would constitute the best option to delay as much as possible the spread of chemoresistance till complete eradication of the disease by vector control operations.

Chemical composition and antimicrobial activity of Cymbopogon citratus and Cymbopogon giganteus essential oils alone and in combination.

As part of ongoing research on the chemical composition and the antimicrobial properties of Burkinabe plants essential oils alone and in combination, essential oils (EOs) from leaves of Cymbopogon citratus and Cymbopogon giganteus from Burkina Faso were analyzed by GC-FID and GC-MS. Five constituents, which accounted for 96.3% of the oil, were identified in the EO of C. citratus. Geranial (48.1%), neral (34.6%) and myrcene (11.0%) were the major constituents. For C. giganteus a total of eight compounds were identified which represented 86.0% of the oils extracted. The dominant compounds were limonene (42%) and a set of monoterpene alcohols: trans-p-mentha-1(7),8-dien-2-ol (14.2%), cis-p-mentha-1(7),8-dien-2-ol (12%), trans-p-mentha-2,8-dien-1-ol (5.6%) and cis-p-mentha-2,8-dien-1-ol (5.2%). The EOs were tested against nine bacteria by using disc diffusion and microdilution methods. C. giganteus EO showed antimicrobial effects against all microorganisms tested whereas C. citratus EO failed to inhibit Pseudomonas aeruginosa. The antimicrobial activity of combinations of the two EOs was quantified by the checkerboard method. Combinations of the two EOs exerted synergistic, additive and indifferent antimicrobial effects. Results of the present investigation provide evidence that the combinations of plant EOs could be assessed for synergistic activity in order to reduce their minimum effective dose.

Chemical composition and antibacterial activities of the essential oils of Lippia chevalieri and Lippia multiflora from Burkina Faso.

The chemical composition of the essential oils of Lippia chevalieri and Lippia multiflora obtained from the air-dried leaves by hydrodistillation were analysed using GC and GC-MS. L. chevalieri and L. multiflora belonged to thymol/p-cymene/2-phenyl ethyl propionate and thymol/p-cymene/thymyl acetate chemotypes, respectively. The essential oils were also tested against 09 strains using a broth microdilution method. The Gram-negative bacteria were the most sensitive. The essential oil of L. multiflora was the most active.

Ovicidal and larvicidal activity against Aedes aegypti and Anopheles gambiae complex mosquitoes of essential oils extracted from three spontaneous plants of Burkina Faso.

Essential oils extracted from dried leaves of three spontaneous plants naturally growing in Burkina Faso, i.e. Cymbopogon proximus, Lippia multiflora and Ocimum canum, exhibited larvicidal activity by the WHO standard protocol against 3rd and 4th instar F1-larvae of field-collected mosquitoes vectors of human disease, namely Aedes aegypti and members of the Anopheles gambiae complex, An. arabiensis and An. gambiae. The median lethal concentration (LC50) for Ae. aegypti and An. gambiae s.l. larvae ranged between 53.5-258.5 ppm and 61.9-301.6 ppm, respectively. The LC90 estimates ranged 74.8-334.8 ppm for Ae. aegypti, and 121.6-582.9 ppm for An. gambiae s.l. Ovicidal activity against eggs of An. gambiae s.l. was also demonstrated. The LC50 values for An. gambiae s.l. eggs ranged between 17.1-188.7 ppm, while LC90 values ranged between 33.5-488 ppm. Lippia multiflora showed the highest activity against An. gambiae s.l. eggs and Ae. aegypti larvae, whereas no difference was found among C. proximus and L. multiflora in their activity against An. gambiae s.l. larvae. Of the three plants, essential oils from O. canum had the lowest activity against both eggs and larvae. Eggs were more susceptible than larvae. Ae. aegypti larvae were more susceptible than larvae of An. gambiae s.l.