Adhesion and virulence properties of native Metarhizium fungal strains from Burkina Faso for the control of malaria vectors

Background: Local strains of the entomopathogenic fungus Metarhizium pingshaense in Burkina Faso have demonstrated remarkable virulence against malaria vectors, positioning them as promising candidates for inclusion in the future arsenal of malaria control strategies. However, the underlying mechanisms responsible for this virulence remain unknown. To comprehend the fungal infection process, it is crucial to investigate the attachment mechanisms of fungal spores to the mosquito cuticle and explore the relationship between virulence and attachment kinetics. This study aims to assess the adhesion and virulence properties of native Metarhizium fungal strains from Burkina Faso for controlling malaria vectors. Methods: Fungal strains were isolated from 201 insects and 1399 rhizosphere samples, and four strains of Metarhizium fungi were selected. Fungal suspensions were used to infect 3-day-old female Anopheles coluzzii mosquitoes at three different concentrations (106, 107, 108 conidia/ml). The survival of the mosquitoes was measured over 14 days, and fungal growth was quantified after 1 and 24 h to assess adhesion of the fungal strains onto the mosquito cuticle. Results: All four fungi strains increased mosquito mortality compared to control (P<2.2–16). Adhesion of the fungal strains was observed on the mosquito cuticle after 24 h at high concentrations (1× 108 conidia/ml), with one strain, having the highest virulent, showing adhesion after just 1 h. Conclusion: The native strains of Metarhizium spp. fungi found in Burkina Faso have the potential to be effective biocontrol agents against malaria vectors, with some strains showing high levels of both virulence and adhesion to the mosquito cuticle

Native entomopathogenic Metarhizium spp. from Burkina Faso and their virulence against the malaria vector Anopheles coluzzii and non-target insects

Genetically enhanced Metarhizium pingshaense are being developed for malaria vector control in Burkina Faso. However, not much is known about the local prevalence and pathogenicity of this fungus, so we prospected mosquitoes and plant roots (a common habitat for Metarhizium spp.) for entomopathogenic fungi. Our investigations showed that Metarhizium spp. represented between 29–74% of fungi isolated from plant root rhizospheres in diverse collection sites. At low spore dosages (1 × 106 conidia/ml), two mosquito-derived M. pingshaense isolates (Met_S26 and Met_S10) showed greater virulence against Anopheles coluzzii (LT80 of ~7 days) than isolates tested in previous studies (LT80 of ~10 days). In addition, the local isolates did not cause disease in non-target insects (honeybees and cockroaches). Our work provides promising findings for isolating local Metarhizium strains for application in mosquito biological control and for future transgenic biocontrol strategies in Burkina Faso.https://doi.org/10.1186/s13071-018-2796-

Wolbachia strain wAlbB shows favourable characteristics for dengue control use in Aedes aegypti from Burkina Faso

Dengue represents an increasing public health burden worldwide. In Africa, underreporting and misdiagnosis often mask its true epidemiology, and dengue is likely to be both more widespread than reported data suggest and increasing in incidence and distribution. Wolbachia-based dengue control is underway in Asia and the Americas but has not to date been deployed in Africa. Due to the genetic heterogeneity of African Aedes aegypti populations and the complexity of the host-symbiont interactions, characterization of key parameters of Wolbachia-carrying mosquitoes is paramount for determining the potential of the system as a control tool for dengue in Africa. The wAlbB Wolbachia strain was stably introduced into an African Ae. aegypti population by introgression, and showed high intracellular density in whole bodies and different mosquito tissues; high intracellular density was also maintained following larval rearing at high temperatures. No effect on the adult lifespan induced by Wolbachia presence was detected. Moreover, the ability of this strain to strongly inhibit DENV-2 dissemination and transmission in the host was also demonstrated in the African background. Our findings suggest the potential of harnessing Wolbachia for dengue control for African populations of Ae. aegypti

Mosquito control by abatement programmes in the United States: perspectives and lessons for countries in sub-Saharan Africa.

Africa and the United States are both large, heterogeneous geographies with a diverse range of ecologies, climates and mosquito species diversity which contribute to disease transmission and nuisance biting. In the United States, mosquito control is nationally, and regionally coordinated and in so much as the Centers for Disease Control (CDC) provides guidance, the Environmental Protection Agency (EPA) provides pesticide registration, and the states provide legal authority and oversight, the implementation is usually decentralized to the state, county, or city level. Mosquito control operations are organized, in most instances, into fully independent mosquito abatement districts, public works departments, local health departments. In some cases, municipalities engage independent private contractors to undertake mosquito control within their jurisdictions. In sub-Saharan Africa (SSA), where most vector-borne disease endemic countries lie, mosquito control is organized centrally at the national level. In this model, the disease control programmes (national malaria control programmes or national malaria elimination programmes (NMCP/NMEP)) are embedded within the central governments' ministries of health (MoHs) and drive vector control policy development and implementation. Because of the high disease burden and limited resources, the primary endpoint of mosquito control in these settings is reduction of mosquito borne diseases, primarily, malaria. In the United States, however, the endpoint is mosquito control, therefore, significant (or even greater) emphasis is laid on nuisance mosquitoes as much as disease vectors. The authors detail experiences and learnings gathered by the delegation of African vector control professionals that participated in a formal exchange programme initiated by the Pan-African Mosquito Control Association (PAMCA), the University of Notre Dame, and members of the American Mosquito Control Association (AMCA), in the United States between the year 2021 and 2022. The authors highlight the key components of mosquito control operations in the United States and compare them to mosquito control programmes in SSA countries endemic for vector-borne diseases, deriving important lessons that could be useful for vector control in SSA

The Strategy of Paratransgenesis for the Control of Malaria Transmission

International audienceInsect-borne diseases are responsible for important burdens on health worldwide particularly in Africa. Malaria alone causes close to half a million deaths every year, mostly in developing, tropical and subtropical countries, with 94% of the global deaths in 2019 occurring in the WHO African region. With several decades, vector control measures have been fundamental to fight against malaria. Considering the spread of resistance to insecticides in mosquitoes and to drugs in parasites, the need for novel strategies to inhibit the transmission of the disease is pressing. In recent years, several studies have focused on the interaction of malaria parasites, bacteria and their insect vectors. Their findings suggested that the microbiota of mosquitoes could be used to block Plasmodium transmission. A strategy, termed paratransgenesis, aims to interfere with the development of malaria parasites within their vectors through genetically-modified microbes, which produce antimalarial effectors inside the insect host. Here we review the progress of the paratransgenesis approach. We provide a historical perspective and then focus on the choice of microbial strains and on genetic engineering strategies. We finally describe the different steps from laboratory design to field implementation to fight against malaria

Targeting male mosquito swarms to control malaria vector density.

Malaria control programs are being jeopardized by the spread of insecticide resistance in mosquito vector populations. It has been estimated that the spread of resistance could lead to an additional 120000 deaths per year, and interfere with the prospects for sustained control or the feasibility of achieving malaria elimination. Another complication for the development of resistance management strategies is that, in addition to insecticide resistance, mosquito behavior evolves in a manner that diminishes the impact of LLINs and IRS. Mosquitoes may circumvent LLIN and IRS control through preferential feeding and resting outside human houses and/or being active earlier in the evening before people go to sleep. Recent developments in our understanding of mosquito swarming suggest that new tools targeting mosquito swarms can be designed to cut down the high reproductive rate of malaria vectors. Targeting swarms of major malaria vectors may provide an effective control method to counteract behavioral resistance developed by mosquitoes. Here, we evaluated the impact of systematic spraying of swarms of Anopheles gambiae s.l. using a mixed carbamate and pyrethroid aerosol. The impact of this intervention on vector density, female insemination rates and the age structure of males was measured. We showed that the resulting mass killing of swarming males and some mate-seeking females resulted in a dramatic 80% decrease in population size compared to a control population. A significant decrease in female insemination rate and a significant shift in the age structure of the male population towards younger males incapable of mating were observed. This paradigm-shift study therefore demonstrates that targeting primarily males rather than females, can have a drastic impact on mosquito population

First identification of Microsporidia MB in Anopheles coluzzii from Zinder City, Niger

Abstract Background Malaria, a disease transmitted by Anopheles mosquitoes, is a major public health problem causing millions of deaths worldwide, mostly among children under the age of 5 years. Biotechnological interventions targeting parasite-vector interactions have shown that the microsporidian symbiont Microsporidia MB has the potential to disrupt and block Plasmodium transmission. Methods A prospective cross-sectional survey was conducted in Zinder City (Zinder), Niger, from August to September 2022, using the CDC light trap technique to collect adult mosquitoes belonging to the Anopheles gambiae complex. The survey focused on collecting mosquitoes from three neighborhoods of Zinder (Birni, Kangna and Garin Malan, located in communes I, II and IV, respectively). Collected mosquitoes were sorted and preserved in 70% ethanol. PCR was used to identify host species and detect the presence of Microsporidia MB and Plasmodium falciparum infection. Results Of the 257 Anopheles mosquitoes collected and identified by PCR, Anopheles coluzzii was the most prevalent species, accounting for 97.7% of the total. Microsporidia MB was exclusively detected in A. coluzzii, with a prevalence of 6.8% (17/251) among the samples. No significant difference in prevalence was found among the three neighborhoods. Only one An. coluzzii mosquito tested PCR-positive for P. falciparum. Conclusions The results confirm the presence of Microsporidia MB in Anopheles mosquitoes in Zinder, Niger, indicating its potential use as a biotechnological intervention against malaria transmission. However, further studies are needed to determine the efficacy of Microsporidia MB to disrupt Plasmodium transmission as well as its impact on vector fitness. Graphical Abstrac

Proportions of young males in the villages of VK5 and VK7 pre-intervention (Round 1 in blue) and post-intervention (Round 2 in Red).

<p>Proportions of young males in the villages of VK5 and VK7 pre-intervention (Round 1 in blue) and post-intervention (Round 2 in Red).</p