ETUDE DE LA NUISANCE DES MOUSTIQUES EN MILIEU UNIVERSITAIRE DE LA FACULTE DES SCIENCES ET TECHNIQUES, BAMAKO, MALI

Mosquitoes are potentially harmful and vectors of pathogens. They compromise the rest and well-being of humans and animals. The main goal of this study is to determine the composition of mosquitoes responsible of human biting at the Faculty of Sciences and Technics of Bamako-Mali. Longitudinal monitoring with monthly cross-sectional visit was carried out from September to December 2019, in order to collect the endophilic and endophagic mosquitoes. The spray-catch was used as a collection methodin 21 rooms selected randomly at the FST. Mosquitoes were identified morphologically andthen by PCR. ELISA-CSP test was used for Plasmodium infection index and the ELISA blood-meal test was to determine mosquitoes blood origin. In total, 802 mosquitoes were collected: 794Culex and 8Anopheles. There were 200 males and 602 females. Female mosquitoes were separated by gonotrophic stages: 231 unfed, 223 fed, 80 semi-gravid and 68 gravid. Up to 34% of Culex and 67% of Anopheles had a preference for human blood, but no female tested positive for Plasmodium infection. This result would be due to the small number of Anopheles captured. An. coluzzii is the only Anopheles species collected.This study shows that mosquitoes are linked to serious problems of nuisance and risk of pathogens transmission in the university. They highly prefer to feed on human host.

Wolbachia endosymbionts in two Anopheles species indicates independent acquisitions and lack of prophage elements

Wolbachia is a genus of obligate bacterial endosymbionts that infect a diverse range of arthropod species as well as filarial nematodes, with its single described species, Wolbachia pipientis, divided into several 'supergroups' based on multilocus sequence typing. Wolbachia strains in mosquitoes have been shown to inhibit the transmission of human pathogens including Plasmodium malaria parasites and arboviruses. Despite their large host range, Wolbachia strains within the major malaria vectors of the Anopheles (A.) gambiae and A. funestus complexes appear at low density based solely on PCR-based methods. Questions have been raised as to whether this represents a true endosymbiotic relationship. However, recent definitive evidence for two distinct, high-density strains of supergroup B Wolbachia within A. demeilloni and A. moucheti has opened exciting possibilities to explore naturally occurring Wolbachia endosymbionts in Anopheles for biocontrol strategies to block Plasmodium transmission. Here we utilise genomic analyses to demonstrate that both Wolbachia strains have retained all key metabolic and transport pathways despite their smaller genome size. We further confirm the presence of cytoplasmic incompatibility factor genes, despite noticeably few prophage regions. Additionally, phylogenetic analysis indicates that these Wolbachia strains may have been introduced into these two Anopheles species via horizontal transmission events, and unlikely to be by ancestral acquisition and subsequent loss events in the Anopheles gambiae species complex. These are the first Wolbachia genomes that enable us to study the relationship between natural strains Plasmodium malaria parasites and their Anopheline hosts.

Oral Susceptibility to Ivermectin is Over Fifty Times Greater in a Wild Population of Anopheles Albimanus Mosquitoes from Belize than the STECLA Laboratory Reference Strain of A. Albimanus

Background: The STECLA strain of Anopheles albimanus Wiedemann has been in continuous colony for many years and is the reference strain on which genomic studies for the species are based. Recently, the STECLA strain was demonstrated to be much less susceptible to ivermectin ingested in a blood meal (LC 50 of 1468 ng/ml) than all other Anopheles species tested to-date (LC 50 values range from 7 – 56 ng/ml). The ability of A. albimanus to survive ingestion of ivermectin at concentrations far beyond that typically found in the blood of ivermectin-treated people or livestock ( i.e ., 30 – 70 ng/ml) could invalidate the use of ivermectin as a malaria vector control strategy in areas where A. albimanus is a primary vector. Methods: To investigate this, we captured host-seeking A. albimanus in northern Belize and conducted membrane feeding bioassays of ivermectin, using the same methods as described earlier with the STECLA strain. Results: Field-collected A. albimanus in Belize were 55 times more susceptible to ingested ivermectin than were the STECLA reference strain. Oral susceptible to ivermectin in wild A. albimanus from Belize (LC 50 of 26 ng/ml) was equivalent to that of other Anopheles species tested. Conclusion: Contrary to our initial assessment using a highly inbred laboratory strain of mosquito, we show that ivermectin treatment of livestock could reduce A. albimanus populations in areas of Central America and the Caribbean where malaria transmission may occur. Future toxicity screening of ivermectin and other systemic parasiticides for malaria control should consider examining wild populations of the vector species being targeted.

Time of Test Periods Influence the Behavioral Responses of Anopheles minimus and Anopheles dirus (Diptera: Culicidae) to DEET

Information on factors influencing the behavioral responses of mosquitoes to repellents is lacking and poorly understood, especially in the Anopheles species, night-biting mosquitoes. Our goal was to investigate the impact of different time periods on circadian activity and behavioral responses of two malaria vectors, Anopheles minimus and An. dirus, to 5% DEET using an excito-repellency test system. Each mosquito species was exposed to the repellent during the daytime (06.00–18.00) and nighttime (18.00–06.00), and time of observation was further divided into four 3-h intervals. Significant escape responses were observed between daytime and nighttime for An. minimus in both noncontact and contact tests. An. dirus showed statistical differences in contact irritancy escape response, whereas no significant difference was found in noncontact repellency tests. Both mosquito species showed more significantly higher escape responses when exposed to DEET during the afternoon and late in the night. This finding indicates that the time of testing may affect the behavioral responses of mosquitoes to repellents, especially in An. minimus and An. dirus. A better understanding of nocturnally active mosquito behavioral responses spanning from dusk to dawn would assist in optimizing product development, screening, and effective evaluation.

Review of Anopheles Mosquito Species, Abundance, and Distribution in Ethiopia

Background. Malaria is a major mosquito-borne disease in Ethiopia, and it is one of the leading causes of morbidity and mortality. Plasmodium falciparum and P. vivax are the two malaria-causing parasitic species commonly known to cause human malaria in Ethiopia. To better manage and control vectors transmitting malaria parasites, the abundance, distribution, and updated annotated list of Anopheles species present in Ethiopia are very important. Methods. In order to compile a list of the species recorded in Ethiopia, 33 original research articles were collected. This work gives an updated list of Anopheles mosquito species in Ethiopia and their abundance, distribution, and composition. Results. According to this review, 110305 Anopheles mosquitoes were collected and 35 Anopheles species were recorded in different parts of Ethiopia. A. arabiensis was the most abundant when compared to other species, whereas A. maculipalpis and A. wilsonii were the least abundant species. The most abundant Anopheles species was recorded in central and the least abundant, from eastern Ethiopia. The second, third, and fourth abundant species were also collected from southern, northern, and western parts of Ethiopia.

Short Communication: The detection of Plasmodium in mosquitoes from Sumba and Sorong districts, Indonesia

Munirah M, Wahid I, Hamid F, Wahyuni S. 2021. Short Communication: The detection of Plasmodium in mosquitoes from Sumba and Sorong districts, Indonesia. Biodiversitas 22: 2680-2684. Malaria is heading for elimination in 2030, but the disease remains prevalent in Indonesia. Therefore, this study aimed to determine a vector other than Anopheles that is potentially responsible for malaria transmission in the country's endemic areas. The mosquitoes were trapped by Kelambu trap, collected using a mouth aspirator, and stored in a tube containing silica gel. They were also examined microscopically following O'Connor identification keys, and Nested PCR was used to detect Plasmodium DNA. The number of mosquitoes collected from two areas was 1.336. In Sumba (Gaura village) district, 493 mosquitoes were captured, and the dominant genus was Anopheles (58.6%), followed by Culex (31%), Armigeres (9.9%), Aedes (0.2%), and Lutzia (0.2%). Among 843 mosquitoes collected from Sorong (Aimas), Culex was 98.9%, followed by Aedes (0.8%) and Anopheles (0.2%). The result of nested PCR found two An. sundaicus from Sumba carried Plasmodium which belongs to P. falciparum and P. vivax species (0.14%). Although we did not detect the presence of Plasmodium in mosquitoes other than the genus Anopheles, in this study, we found Anopheles species that have never previously been reported from the area, namely An. bailey and An. barbirostris from Papua and An. nivipes in West Sumba.

A systematic review assessing the potential for release of vector species from competition following insecticide-based population suppression of Anopheles species in Africa

Background: While insecticide-based vector control can effectively target vector species in areas of high malaria endemicity, such as Anopheles gambiae in Africa, residual disease transmission can occur. Understanding the potential role of competitive displacement between vector species could inform both current insecticide-based vector control programmes and the development of future complementary interventions. Methods: A systematic review was conducted to identify studies of insecticide-based vector control of Anopheles species in Africa that reported indices for absolute densities of vector species. After screening against inclusion, exclusion and risk of bias criteria, studies were assigned to three categories based on whether they showed population density changes involving decreases in two or more vector species (D), increases in two or more vector species (I), or increases in one vector species concomitant with decreases in another vector species (ID). Category ID studies could thus provide evidence consistent with the release of vector species from competition following the insecticide-based population suppression of Anopheles species. Results: Of 5,569 papers identified in searches, 30 were selected for quantitative and qualitative analysis. Nineteen studies were assigned to category D and 1 study to category I. Ten studies categorised as ID provided evidence ranging from weak to persuasive that release from competition could have contributed to changes in species composition. Category ID showed no statistical differences from category D for reductions in malaria transmission and levels of insecticide resistance, but did so for insecticide type, pyrethroids being associated with category ID. A qualitative assessment identified 5 studies that provided the most convincing evidence that release from competition could have contributed to changes in species composition. Conclusion: This review identified evidence that insecticide-based reductions in the density of Anopheles species in Africa could facilitate the release of other vector species from competition. While it remains uncertain whether this evidence is representative of most entomological sequelae from the use insecticide-based vector control in the field, 5 studies provided persuasive evidence that insecticide use could lead, at least under some circumstances, to competitive release of non-targeted vector species. These results should inform current and future integrated vector management approaches to malaria control.

Larvicidal Efficacy and GC-MS Analysis of Hyptis suaveolens Leaf Extracts against Anopheles Species

Mosquitoes are the most important group of insects in terms of public health importance, which transmit serious human diseases. The continuous application of synthetic insecticides to control these mosquitoes causes development of resistance in vector species, and an adverse effect on environmental quality and non-target organisms including human health. Therefore, the use of active toxic agents from plant extracts as alternative mosquito control strategy cannot be over emphasized, as these are non-toxic, easily available at affordable prices, biodegradable and show target - specific activities against different species of vector mosquitoes. The aim of the present study was to evaluate the larvicidal efficacy of the aqueous and methanol leaf extracts of H. suaveolens against the fourth instars larvae of Anopheles species. Standard WHO protocols was adopted for the larvicidal bioassay. Larvicidal activity was evaluated at concentrations of 200, 400, 600, 800 and 1000 mg/L. The larval mortality was observed after 24 and 48hours bioassay. The results are mean of three replicates and the mortalities recorded were subjected to chi-square test and probit analysis to determine median lethal concentrations (LC50). TheGC-MS analysis ofthe methanolic leaf extract of the plantrevealed the presence of twelve compounds on the chromatogram. Among the major compounds areOleic Acid (33.33%), Octadecanoic acid (13.52%), 1,3-Cyclohexadiene-1-methanol,alpha.,2,6,6-(10.42%), 1,3-Cyclopentanediol, trans (9.60%), n-Hexadecanoic acid (9.01%) and 4-Hepten-3-one, 4-methyl (7.0%).The phytochemical screening of the aqueous and methanol leaf extracts of the plant revealed the presence of Tannins, Terpenoids, Flavonoids, Steroids, Carbohydrates, Cardiac glycoside and resins. The LC50 values estimated were 316.22mg/Lfor methanol extract and 323.59 mg/L for aqueous extract. The differences between the two extracts were however not significantly different at P>0.05. The findings also revealed that mortality was concentration dependent and both extracts showed promising larvicidal activity against Anopheles species larvae. Therefore, the crude leaf extract of the plant is recommended to be used as alternative to synthetic larvicides and further research is needed to test the activity of the plant on non-target organisms.

Lymphatic filariasis, infection status in Culex quinquefasciatus and Anopheles species after six rounds of mass drug administration in Masasi District, Tanzania

Background Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. Evidence shows a persistent LF transmission despite more than a decade of mass drug administration (MDA). It is advocated that, regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely. This study was therefore designed to assess the status of Wuchereria bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District, South Eastern Tanzania. Methods Mosquitoes were collected between June and July 2019 using Center for Diseases Control (CDC) light traps and gravid traps for indoor and outdoor respectively. The collected mosquitoes were morphologically identified into respective species. Dissections and PCR were carried out to detect W. bancrofti infection. Questionnaire survey and checklist were used to assess vector control interventions and household environment respectively. A Poisson regression model was run to determine the effects of household environment on filarial vector density. Results Overall, 12 452 mosquitoes were collected of which 10 545 (84.7%) were filarial vectors. Of these, Anopheles gambiae complex, An. funestus group and Cx. quinquefasciatus accounted for 0.1%, 0.7% and 99.2% respectively. A total of 365 pools of Cx. quinquefasciatus (each with 20 mosquitoes) and 46 individual samples of Anopheles species were analyzed by PCR. For Cx. quinquefasciatus pools, 33 were positive for W. bancrofti, giving an infection rate of 0.5%, while the 46 samples of Anopheles species were all negative. All 1859 dissected mosquitoes analyzed by microscopy were also negative. Households with modern latrines had less mosquitoes than those with pit latrines [odds ratio (OR) = 0.407, P < 0.05]. Houses with unscreened windows had more mosquitoes as compared to those with screened windows (OR = 2.125, P < 0.05). More than 80% of the participants own bednets while 16.5% had no protection. Conclusions LF low transmission is still ongoing in Masasi District after six rounds of MDA and vector control interventions. The findings also suggest that molecular tools may be essential for xenomonitoring LF transmission during elimination phase.

The Microbiota of Three Anopheles Species in China

ABSTRACT Microbiota are vital for the development, physiology, and vectorial capacity of mosquitoes. The composition and role of microbiota in Anopheles species, especially Anopheles gambiae and Anopheles stephensi, have been extensively studied, but little is known about the microbiota of Anopheles species in China. We characterized the microbial communities of Anopheles dirus, Anopheles sinensis, and Anopheles lesteri by 16S rRNA sequencing. There were distinct differences in the composition of microbiota in An. lesteri and the other 2 species. The discriminatory genera in the 3 species were analyzed by the linear discriminant analysis effect size method. Our results provide an overview of the population structure of microbiota in 3 native Anopheles species and will pave the way for further understanding of their role in mosquito physiology and vector competence.