The mosquito dunk (Bacillus thuringensis israelienses) as a control agent against mosquito larvae in Khartoum State, Sudan Abdalmagi

Background: During the mid-1970s, larvicides have become available that are highly effective, yet selective in action, and therefore environmentally safe to non-target organisms, as well as for human exposure(1). Objectives: The small field trial was carried out from 12th of January to 16th of February 2008 in Khartoum State to evaluate the efficacy and persistence mosquito dunk® (Bti) against mosquito larvae and to measure the effect of physic-chemical properties on mosquito dunk. Material & Methods: The efficacy and persistence of Bacillus thuringiensis subspecies israelensis (mosquito dunk®) as a biological control agent against mosquito larvae was conducted in Khartoum State. Twelve ponds were used as natural breeding habitats of mosquitoes; six of them were treated with dunk at a rate of 1 dunk per 100 square feet and six ponds left untreated (control). Results: The study revealed that more than 80% reduction in immature stages density was observed up to 5, 3 and 2 weeks for the 3rd, 2nd and 4th instars of Anopheline spp., respectively. However, the study showed that the mosquito dunk was noteffective (under 80% mortality) against 1st, instar larvae and pupae of Anopheline species as well as Culex developmental stages. Conclusion & Interpretations: The dunk was very effective in controlling 3rd and 4th instars of Anopheles spp; for 2 weeks interval. Therefore we propose a surface application regime of once every 2 weeks for mosquito dunk

Field Evaluation of Three Commercial Repellents Formulations against Afrotropical Vectors Mosquitoes in Camerooun

Three synthetic commercial insert repellents; Buzz-Off TM (30DEET); Cinq-sur-CinqTM (25IR3535 + essential oils) and prebutix TM(25IR3535) were tested in field conditions for their efficacy and persistence against mosquitoes in the forest area of Cameroon. During 48-days; 7; 569 mosquitoes belonging to four genera were collected: Mansonia spp (67.3); Anopheles spp (27.4); Aedes spp(3.8); and Culex spp (1.5). At the end of the 8-hours exposure period; the DEET-based repellent; Buzz Off TM produced the highest protection against Aedes spp; Culex spp and Mansonia spp. For Anophelines; results were more variable : PrebutixTM showed better protection against An. mouchetti; Cinq-sur-CinqTM was more efficacious against An. Funestus and An.ziemani; whereas Buzz-OffTM appeared more effective against An. Gambiae s.s. and An. nili. Efficacy and persistence parameters were estimated only for An. moucheti and Mansonia spp. The effective dosages (ED50 and ED95) as well as the effective half-life obtained with the DEET-based repellent were highly variable among replicates in the case of An. moucheti. For mansonia spp; the estimated EDO value for the DEET -based repellent was = 0.06mg/cm2. For the two IR3535-based repellents; the ED50 values varied from 0.06 to 0.10 mg/cm2; and 0.15 to 0.20 mg/cm2 for An. moucheti and Mansonia spp; respectively. Globally; the ED95 values values of the three repellents were around 1mg/cm2 except that of Cinq-sur-CinqTM which was ? 0.3mg/cm2 in the case of An. moucheti. The estimated effective half-lifes of the three repellents were approximately between 3 and 5h. Our results highlight the heterogeneity in the response of different mosquito species when exposed to the tested insect repellents; showing the relevance of evaluating efficacy and persistence profiles of different formulations in specific environmental contexts