Background Anopheles stephensi, an invasive malaria vector, was first detected in Africa nearly 10 years ago. After the initial finding in Djibouti, it has subsequently been found in Ethiopia, Sudan and Somalia. To better inform policies and vector control decisions, it is important to understand the distribution, bionomics, insecticide susceptibility, and transmission potential of An. stephensi. These aspects were studied as part of routine entomological monitoring in Ethiopia between 2018 and 2020. Methods Adult mosquitoes were collected using human landing collections, pyrethrum spray catches, CDC light traps, animal-baited tent traps, resting boxes, and manual aspiration from animal shelters. Larvae were collected using hand-held dippers. The source of blood in blood-fed mosquitoes and the presence of sporozoites was assessed through enzyme-linked immunosorbent assays (ELISA). Insecticide susceptibility was assessed for pyrethroids, organophosphates and carbamates. Results Adult An. stephensi were collected with aspiration, black resting boxes, and animal-baited traps collecting the highest numbers of mosquitoes. Although sampling efforts were geographically widespread, An. stephensi larvae were collected in urban and rural sites in eastern Ethiopia, but An. stephensi larvae were not found in western Ethiopian sites. Blood-meal analysis revealed a high proportion of blood meals that were taken from goats, and only a small proportion from humans. Plasmodium vivax was detected in wild-collected An. stephensi. High levels of insecticide resistance were detected to pyrethroids, carbamates and organophosphates. Pre-exposure to piperonyl butoxide increased susceptibility to pyrethroids. Larvae were found to be susceptible to temephos. Conclusions Understanding the bionomics, insecticide susceptibility and distribution of An. stephensi will improve the quality of a national response in Ethiopia and provide additional information on populations of this invasive species in Africa. Further work is needed to understand the role that An. stephensi will have in Plasmodium transmission and malaria case incidence. While additional data are being collected, national programmes can use the available data to formulate and operationalize national strategies against the threat of An. stephensi.

Background The emergence and spread of resistant strains of malaria vectors to chemical insecticides are becoming major problems for malaria vector management. Natural plant products have a vital role to play in the current challenge of malaria control. The current study was conducted to evaluate insecticidal effect of ethnobotanical plant extracts against the primary malaria vector, Anopheles arabiensis in northwestern Ethiopia. Methods Primarily, ethnobotanical plants used for Anopheles mosquito control were surveyed in Dangur district, northwestern Ethiopia. Insecticide-susceptible strains of Anopheles arabiensis mosquito were reared in the insectary of the Tropical and Infectious Diseases Research Centre, Assosa University. After surveying plants used for mosquito control in local people, four frequently used plants were identified for extraction. The larvicidal and adulticidal potential of frequently used plant extracts against susceptible strains of the laboratory colony were evaluated. Results A total of 15 plants were identified as ethnobotanical plants that help local people with mosquito control. Azadirachta indica, Ocimum lamiifolium, Ocimum americanum, Moringa olifeira leaf, and Moringa olifeira seed species of local plants were found to be frequently used to kill and/or repel mosquitoes in the study district. All the plant extracts were found to have potential larvicidal activity against fourth instar larvae of An. arabiensis and only ethanol and methanol extract of Azadirachta indica and Ocimum lamiifolium were found to have potential adulticidal effect against adult of An. arabiensis. The highest larvicidal activity was observed in ethanol extract of Azadirachta indica with 95% larval mortality and lowest Lethal Concentration 50 (LC 50) of 40.73parts per million (ppm) and LC90 of 186.66 ppm. The highest adulticidal activity was observed in methanol extract of Azadirachta indica with 75% adult mortality at 300 ppm and lowest LC50 of 106.65 ppm and LC90 of 1,293 ppm. The lowest larvicidal and adulticidal activity was observed in methanol extracts of Ocimum lamiifolium with 63.35% larval mortality and leaf extract of Moringa olifeira with 50% adult mortality at 300 ppm, respectively. Conclusion Ethanol extract of Azadirachta indica exerted a remarkable larvicidal effect against An. arabiensis and thus it can be used for botanical mosquito insecticide development. Since the current finding is based on susceptible strain of An. arabiensis, further work on wild mosquitoes is recommended.

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Anopheles gambiae complex mosquitoes comprise different morphologically identical species and the most medically important malaria vectors in Africa. Understanding An. gambiae complex mosquitoes’ mating behaviour is a clue for prevention and control of malaria. The factors affecting the mating behavior of An. gambiae complex are age, body size, food finding, type of food, host availability and environmental temperature. An. gambiae complex passes through different and unique mating strategies. The fundamental mechanisms underlying mating behavior of An. gambiae complex are male aggregation before copulation which is called swarming, finding female and insemination. Male in the swarm detects the wing beat of female with which he mates by auditory system. The wing beat frequencies of opposite sex of the same genetic form simply harmonize indicating possible hybridization while that of different genetic forms do not harmonize. The successive mating behavior of female An. gambiae mosquitoes includes, locating a male among the swarm for cupola, friend selection and storage of sperm. Successful female An. gambiae complex mosquitoes mating is accomplished by host seeking, blood feeding and digestion, egg development and oviposition. The sequential process of host finding and blood feeding followed by blood digestion and simultaneously egg maturation and accomplished by searching of oviposition site and oviposition is referred to as gonotrophic cycle. The time period between two successive blood feedings or two successive ovipositions is said to be gonotrophic period. The length of gonotrophic period depends on temperature, number of previous gonotrophic cycle, host and breeding site availability. In addition to population net reproduction of the colony, gonotrophic cycle is also used to estimate female mosquitoes’ age by determining the parity. Finally, understandings of mating behavior and gonotrophic cycle of An. gambiae complex mosquitoes help in malaria vector control strategies and their vector competence.

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Background Malaria vectors control interventions mainly rely on the control of adults using indoor residual sprayings and long-lasting insecticidal nets in Ethiopia. However, the emergence and widespread of insecticide resistance in the primary malaria vector, Anopheles gambiae sinso lato challenges the malaria vector control efforts in Ethiopia. The aim of this study was to investigate species composition, abundance and insecticide resistance status of main malaria mosquitoes in Assosa district, Benishangul Gumuz, Western Ethiopia. Methods The study was conducted from July 2021 to June 2022. After identification of possible breeding sites, Anopheles mosquito larvae were collected using a standard dipper from varies breeding habitats. Susceptibility tests were conducted on wild population of female An. gambiae complex following World health organization standard susceptibility test procedure. Insecticide impregnated papers with deltamethrin (0.05%), alphacypermethrine (0.05%), propoxur (0.1%), and primiphos methyl (0.25%), were used for the study. Result Six major Anopheles mosquitoes’ larvae breeding habitats were identified in four villages, namely, drainage ditch, swamp, pond, animal footprint, sewerage and stagnant water. A total of 2051 Anopheles larvae were collected and identified. Out of all collected Anopheles larvae, 1884 larvae were reared and identified to four species (An. gambiae s.l., An. coustani, An. ziemanni and An. funestus). An. gambiae s.l. were found to be the dominant species (1732, 84.4%) species and the lowest An. funestus were collected (n = 17, 0.9%). The most productive habitats were stagnant water (n = 752; 39. 9%) with larvae/dip while sewerage were detected to be least productive (n = 71; 3.76%) for Anopheles mosquito larvae with mean density of 1.2 and 0.03 larvae/dip, respectively, (P < 0.05). The susceptibility result indicated that the population of An. gambiae s.l in the study area found resistant against alphacypermethrine, deltamethrin and permethrin 63%, 71% and 43% respectively. The result revealed that the vector is susceptible to pirimiphos-methyl and propoxur with 100% susceptibility rate. Conclusion Anopheles gambiae complex is the predominant malaria vector in Assosa District. Anopheles gambiae complex developed high level of resistance against most of insecticide classes. Pirmiphosmethyl and propoxur are effective insecticides for malaria vector control in Assosa district, Ethiopia.

Background: The emergence and spread of resistant strains of malaria vectors to chemical insecticides are becoming major problem for malaria vector management. Natural plant products play a vital role to resolve the current challenge of malaria control.Objective: The current study was conducted to evaluate insecticidal effect of ethnobotanical plant extracts against the primary malaria vector, Anopheles arabiensis in Northwestern Ethiopia.Methods: Primarily, ethnobotanical plants used for Anopheles mosquito control was surveyed in Dangur district, Northwestern Ethiopia. Insecticide susceptible strains of Anopheles arabiensis mosquito were reared in insectary of tropical and infectious diseases research center, Assosa university. The larvicidal and adulticidal potentials of frequently used plant extracts against susceptible strains of laboratory colony were evaluated.Result: A total of fifteen plants were identified as ethnobotanical plants helping the local people for mosquito control. Azadirachta indica, Ocimum lamiifolium, Ocimum americanum, Moringa olifiera leaf, and Moringa olifiera seed species of local plants were found to be frequently used to kill and/or repel mosquitoes in the study district. All the plant extracts were found to have potential larvicidal activity against 4th instar larvae of An. arabiensis and only ethanol and methanol extract of A. indica and O. lamiifolium were found to have potential adulticidal effect against adult of An. arabiensis. The highest larvicidal activity was observed in ethanol extract of A. indica with 95% larval mortality and lowest LC50 of 40.73 ppm and LC90 of 186.66 ppm. The highest adulticidal activity was observed in methanol extract of A. indica with 75% adult mortality at 300 ppm and lowest LC50 of 106.65ppm and LC90 of 1293ppm. The lowest larvicidal and adulticidal activity was observed in methanol extracts of O. lamiifolium with 63.35% larval mortality and leaf extract of M. olifiera with 50% adult mortality at 300 ppm, respectively.Conclusion: ethanol extract of A. indica exerted a remarkable larvicidal effect against An. arabiensis and thus it can be used for botanical mosquito insecticide development.