bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2023–02–12
eleven papers selected by
Richard Halfpenny, Staffordshire University
  1. Detection of a reduced susceptibility to chlorfenapyr in the malaria vector Anopheles gambiae contrasts with full susceptibility in Anopheles funestus across Africa.
  2. Gaps in protection: the actual challenge in malaria elimination.
  3. Quantifying the direct and indirect protection provided by insecticide treated bed nets against malaria.
  4. Distribution and mitochondrial CO1-based genetic diversity of Aedes aegypti L (Culicidae: Diptera) in Saudi Arabia.
  5. Two novel, tightly linked, and rapidly evolving genes underlie Aedes aegypti mosquito reproductive resilience during drought.
  6. Evaluation of the model malaria elimination strategy in Mandla district along with its neighbouring districts: a time series analysis from 2008 to 2020.
  7. Notification of malaria cases in the Brazilian Amazon Basin from 2010 to 2020: an analysis of the reporting times.
  8. Climate Drivers of Malaria Transmission Seasonality and Their Relative Importance in Sub-Saharan Africa.
  9. Evaluating a community engagement model for malaria elimination in Haiti: lessons from the community health council project (2019-2021).
  10. Characterizing the Vector Data Ecosystem.
  11. Vaccine against malaria: A ground-breaking step towards elimination in India.
  1. Sci Rep. 2023 Feb 09. 13(1): 2363
    Detection of a reduced susceptibility to chlorfenapyr in the malaria vector Anopheles gambiae contrasts with full susceptibility in Anopheles funestus across Africa.
    Magellan Tchouakui, Tatiane Assatse, Hervé R Tazokong, Ambrose Oruni, Benjamin D Menze, Daniel Nguiffo-Nguete, Leon M J Mugenzi, Jonathan Kayondo, Francis Watsenga, Themba Mzilahowa, Michael Osae, Charles S Wondji.
      New insecticides have recently been produced to help control pyrethroid-resistant malaria vectors including the pyrrole, chlorfenapyr. Monitoring the susceptibility of mosquito populations against this new product and potential cross-resistance with current insecticides is vital for better resistance management. In this study, we assessed the resistance status of the major malaria vectors Anopheles gambiae and Anopheles funestus to chlorfenapyr across Africa and explored potential cross-resistance with known pyrethroid resistance markers. Efficacy of chlorfenapyr 100 µg/ml against An. gambiae and An. funestus from five Cameroonian locations, the Democratic Republic of Congo, Ghana, Uganda, and Malawi was assessed using CDC bottle assays. Synergist assays were performed with PBO (4%), DEM (8%) and DEF (0.25%) and several pyrethroid-resistant markers were genotyped in both species to assess potential cross-resistance between pyrethroids and chlorfenapyr. Resistance to chlorfenapyr was detected in An. gambiae populations from DRC (Kinshasa) (mortality rate: 64.3 ± 7.1%) Ghana (Obuasi) (65.9 ± 7.4%), Cameroon (Mangoum; 75.2 ± 7.7% and Nkolondom; 86.1 ± 7.4). In contrast, all An. funestus populations were fully susceptible. A negative association was observed between the L1014F-kdr mutation and chlorfenapyr resistance with a greater frequency of homozygote resistant mosquitoes among the dead mosquitoes after exposure compared to alive (OR 0.5; P = 0.02) whereas no association was found between GSTe2 (I114T in An. gambiae; L119F in An. funestus) and resistance to chlorfenapyr. A significant increase of mortality to chlorfenapyr 10 µg/ml was observed in An. funestus after to PBO, DEM and DEF whereas a trend for a decreased mortality was observed in An. gambiae after PBO pre-exposure. This study reveals a greater risk of chlorfenapyr resistance in An. gambiae populations than in An. funestus. However, the higher susceptibility in kdr-resistant mosquitoes points to higher efficacy of chlorfenapyr against the widespread kdr-based pyrethroid resistance.
    DOI:  https://doi.org/10.1038/s41598-023-29605-w
  2. Malar J. 2023 Feb 07. 22(1): 46
    Gaps in protection: the actual challenge in malaria elimination.
    Krijn P Paaijmans, Neil F Lobo.
      Progress in reducing both malaria cases and deaths has stalled with regression seen in many geographies. While significant attention is given to the contributing challenges of drug and insecticide resistance, 'residual' malaria is often diminished to transmission resulting from outdoor-biting or zoophagic/opportunistic mosquito vectors. These specific vector bionomic traits are only part of the problem, as residual transmission may be driven by (a combination of) (1) sub-optimal intervention coverage, quality, acceptance, and/or usage, (2) drug resistance, (3) insecticide resistance, (4) refractory, resistant and adaptive vector and human behaviours that lower intervention effectiveness, (5) lack of, limited access to, and/or willingness to use healthcare systems, (6) diagnostic sensitivity along with the parallel issue of hrp2/3 mutations, (7) (inter)national policy, (8) the research and development pipeline, and (9) external factors such as natural disasters and conflict zones. Towards combating the minimization of this extensive and multipronged issue among the scientific community, funding agencies, and public health officials responsible for guiding or developing malaria programmes, an alternative way of describing this transmission is proposed by focusing in on the causative 'gaps in protection'. Defining and wording it as such zeros in on the drivers that result in the observed remaining (or increasing) transmission, allowing the malaria community to focus on solutions by identifying the actual causes. Outlining, defining and quantifying the gaps in protection for a given system is of utmost importance to understand what needs to be done, differentiating what can be done versus what cannot be tackled at that moment, along with delineating the technical and financial capacity required.
    DOI:  https://doi.org/10.1186/s12936-023-04473-x
  3. Nat Commun. 2023 Feb 08. 14(1): 676
    Quantifying the direct and indirect protection provided by insecticide treated bed nets against malaria.
    H Juliette T Unwin, Ellie Sherrard-Smith, Thomas S Churcher, Azra C Ghani.
      Long lasting insecticidal nets (LLINs) provide both direct and indirect protection against malaria. As pyrethroid resistance evolves in mosquito vectors, it will be useful to understand how the specific benefits LLINs afford individuals and communities may be affected. Here we use modelling to show that there is no minimum LLIN usage needed for users and non-users to benefit from community protection. Modelling results also indicate that pyrethroid resistance in local mosquitoes will likely diminish the direct and indirect benefits from insecticides, leaving the barrier effects intact, but LLINs are still expected to provide enhanced benefit over untreated nets even at high levels of pyrethroid resistance.
    DOI:  https://doi.org/10.1038/s41467-023-36356-9
  4. Saudi J Biol Sci. 2023 Mar;30(3): 103566
    Distribution and mitochondrial CO1-based genetic diversity of Aedes aegypti L (Culicidae: Diptera) in Saudi Arabia.
    Al Thabiani Aziz.
      Mosquitoes (Diptera: Culicidae) act as vectors for various pathogens and parasites that affect millions of people worldwide. Aedes aegypti (Linnaeus, 1762) is one of the devastating pests of humans, acting as a key vector of dengue viruses. Therefore, correct identification of this serious pest to determine its distribution is paramount in its management. Morphological identification is usually based on the maturity and quality of the specimens. This can still yield ambiguous results in distinguishing Ae. aegypti species due to limited taxonomic expertise and the presence of cryptic species. In this research, mitochondrial CO1 gene-based identification was adopted to analyze 7 samples, each containing 7 specimens of Ae. aegypti from various localities of Saudi Arabia: Jeddah (A1), Makkah (A2), Al Madinah Al Munawwarah (A4), Jazan (A5), Qunfudah (A6), Yanbu (A8), and Najran (A10). DNA barcoding and maximum likelihood (ML) tree analysis revealed that all 49 species belong to Ae. aegypti and showed high similarity with specimens of this species worldwide.
    Keywords:  Aedes aegypti; Arthropods; DNA barcoding; Genetic variability; Saudi Arabia; Viruses
    DOI:  https://doi.org/10.1016/j.sjbs.2023.103566
  5. Elife. 2023 Feb 06. pii: e80489. [Epub ahead of print]12
    Two novel, tightly linked, and rapidly evolving genes underlie Aedes aegypti mosquito reproductive resilience during drought.
    Krithika Venkataraman, Nadav Shai, Priyanka Lakhiani, Sarah Zylka, Jieqing Zhao, Margaret Herre, Joshua Zeng, Lauren A Neal, Henrik Molina, Li Zhao, Leslie B Vosshall.
      Female Aedes aegypti mosquitoes impose a severe global public health burden as vectors of multiple viral pathogens. Under optimal environmental conditions, Aedes aegypti females have access to human hosts that provide blood proteins for egg development, conspecific males that provide sperm for fertilization, and freshwater that serves as an egg-laying substrate suitable for offspring survival. As global temperatures rise, Aedes aegypti females are faced with climate challenges like intense droughts and intermittent precipitation, which create unpredictable, suboptimal conditions for egg-laying. Here we show that under drought-like conditions simulated in the laboratory, females retain mature eggs in their ovaries for extended periods, while maintaining the viability of these eggs until they can be laid in freshwater. Using transcriptomic and proteomic profiling of Aedes aegypti ovaries, we identify two previously uncharacterized genes named tweedledee and tweedledum, each encoding a small, secreted protein that both show ovary-enriched, temporally-restricted expression during egg retention. These genes are mosquito-specific, linked within a syntenic locus, and rapidly evolving under positive selection, raising the possibility that they serve an adaptive function. CRISPR-Cas9 deletion of both tweedledee and tweedledum demonstrates that they are specifically required for extended retention of viable eggs. These results highlight an elegant example of taxon-restricted genes at the heart of an important adaptation that equips Aedes aegypti females with 'insurance' to flexibly extend their reproductive schedule without losing reproductive capacity, thus allowing this species to exploit unpredictable habitats in a changing world.
    Keywords:  evolutionary biology; genetics; genomics
    DOI:  https://doi.org/10.7554/eLife.80489
  6. Malar J. 2023 Feb 06. 22(1): 45
    Evaluation of the model malaria elimination strategy in Mandla district along with its neighbouring districts: a time series analysis from 2008 to 2020.
    Mrigendra P Singh, Harsh Rajvanshi, Praveen K Bharti, Himanshu Jayswar, Srinath Singh, R K Mehra, Manoj Pandey, Ram Shankar Sahu, Brajesh Patel, Ramji Bhalavi, Sekh Nisar, Harpreet Kaur, Aparup Das, Davidson H Hamer, Altaf A Lal.
       BACKGROUND: Compared to 2017, India achieved a significant reduction in malaria cases in 2020. Madhya Pradesh (MP) is a tribal dominated state of India with history of high malaria burden in some districts. District Mandla of MP state showed a considerable decline in malaria cases between 2000 and 2013, except in 2007. Subsequently, a resurgence of malaria cases was observed during 2014 and 2015. The Malaria Elimination Demonstration Project (MEDP) was launched in 2017 in Mandla with the goal to achieve zero indigenous malaria cases. This project used: (1) active surveillance and case management using T4 (Track fever, Test fever, Treat patient, and Track patient); (2) vector control using indoor residual sprays and long-lasting insecticidal nets; (3) information education communication and behaviour change communication; and (4) regular monitoring and evaluation with an emphasis on operational and management accountability. This study has investigated malaria prevalence trends from 2008 to 2020, and has predicted trends for the next 5 years for Mandla and its bordering districts.
    METHODS: The malaria prevalence data of the district Mandla for the period of January 2008 to August 2017 was obtained from District Malaria Office (DMO) Mandla and data for the period of September 2017 to December 2020 was taken from MEDP data repository. Further, the malaria prevalence data for the period of January 2008 to December 2020 was collected from DMOs of the neighbouring districts of Mandla. A univariate time series and forecast analysis was performed using seasonal autoregressive integrated moving average model.
    FINDINGS: Malaria prevalence in Mandla showed a sharp decline [- 87% (95% CI - 90%, - 84%)] from 2017 to 2020. The malaria forecast for Mandla predicts zero cases in the next 5 years (2021-2025), provided current interventions are sustained. By contrast, the model has forecasted a risk of resurgence of malaria in other districts in MP (Balaghat, Dindori, Jabalpur, Seoni, and Kawardha) that were not the part of MEDP.
    CONCLUSION: The interventions deployed as part of MEDP have resulted in a sustainable zero indigenous malaria cases in Mandla. Use of similar strategies in neighbouring and other malaria-endemic districts in India could achieve similar results. However, without adding extra cost to the existing intervention, sincere efforts are needed to sustain these interventions and their impact using accountability framework, data transparency, and programme ownership from state to district level.
    Keywords:  Causal effect; Forecast; Malaria Elimination Demonstration Project; Malaria elimination; Time series; Trend of malaria
    DOI:  https://doi.org/10.1186/s12936-023-04477-7
  7. Malar J. 2023 Feb 10. 22(1): 49
    Notification of malaria cases in the Brazilian Amazon Basin from 2010 to 2020: an analysis of the reporting times.
    Mario J C Ayala, Naiara C M Valiati, Leonardo S Bastos, Daniel A M Villela.
       BACKGROUND: As controlling malaria transmission remains a public-health challenge in the Brazilian Amazon basin, the National Surveillance System for Malaria (SIVEP-MALARIA) has registered malaria notifications for over fifteen years helping in the decision-making on control and elimination. As a surveillance database, the system is prone to reporting delays, and knowledge about reporting patterns is essential in decisions.
    METHODS: This study contains an analysis of temporal and state trends of reporting times in a total of 1,580,617 individual malaria reports from January 2010 to December 2020, applying procedures for statistical distribution fitting. A nowcasting technique was applied to show an estimation of number of cases using a statistical model of reporting delays.
    RESULTS: Reporting delays increased over time for the states of Amazonas, Rondônia, Roraima, and Pará. Amapá has maintained a similar reporting delay pattern, while Acre decreased reporting delay between 2010 and 2020. Predictions were more accurate in states with lower reporting delays. The temporal evolution of reporting delays only showed a decrease in malaria reports in Acre from 2010 to 2020.
    CONCLUSION: Malaria notifications may take days or weeks to enter the national surveillance database. The reporting times are likely to impact incidence estimation over periods when data is incomplete, whilst the impact of delays becomes smaller for retrospective analysis. Short-term assessments for the estimation of malaria incidence from the malaria control programme must deal with reporting delays.
    Keywords:  Health surveillance; Malaria; Reporting times
    DOI:  https://doi.org/10.1186/s12936-023-04464-y
  8. Geohealth. 2023 Feb;7(2): e2022GH000698
    Climate Drivers of Malaria Transmission Seasonality and Their Relative Importance in Sub-Saharan Africa.
    Edmund I Yamba, Andreas H Fink, Kingsley Badu, Ernest O Asare, Adrian M Tompkins, Leonard K Amekudzi.
      A new database of the Entomological Inoculation Rate (EIR) was used to directly link the risk of infectious mosquito bites to climate in Sub-Saharan Africa. Applying a statistical mixed model framework to high-quality monthly EIR measurements collected from field campaigns in Sub-Saharan Africa, we analyzed the impact of rainfall and temperature seasonality on EIR seasonality and determined important climate drivers of malaria seasonality across varied climate settings in the region. We observed that seasonal malaria transmission was within a temperature window of 15°C-40°C and was sustained if average temperature was well above 15°C or below 40°C. Monthly maximum rainfall for seasonal malaria transmission did not exceed 600 in west Central Africa, and 400 mm in the Sahel, Guinea Savannah, and East Africa. Based on a multi-regression model approach, rainfall and temperature seasonality were found to be significantly associated with malaria seasonality in all parts of Sub-Saharan Africa except in west Central Africa. Topography was found to have significant influence on which climate variable is an important determinant of malaria seasonality in East Africa. Seasonal malaria transmission onset lags behind rainfall only at markedly seasonal rainfall areas such as Sahel and East Africa; elsewhere, malaria transmission is year-round. High-quality EIR measurements can usefully supplement established metrics for seasonal malaria. The study's outcome is important for the improvement and validation of weather-driven dynamical mathematical malaria models that directly simulate EIR. Our results can contribute to the development of fit-for-purpose weather-driven malaria models to support health decision-making in the fight to control or eliminate malaria in Sub-Saharan Africa.
    Keywords:  climate; drivers; malaria; relative; seasonal; transmission
    DOI:  https://doi.org/10.1029/2022GH000698
  9. Malar J. 2023 Feb 09. 22(1): 47
    Evaluating a community engagement model for malaria elimination in Haiti: lessons from the community health council project (2019-2021).
    Kevin Bardosh, Luccene Desir, Lorence Jean, Sarah Yoss, Brianna Poovey, Andrew Nute, Madsen Valerie Beau de Rochars, Marc-Aurèle Telfort, Fabiola Benoit, Ginette Chery, Marie Carmelle Charlotin, Gregory S Noland.
       BACKGROUND: Community engagement (CE) plays a critical role in malaria control and elimination. CE approaches vary substantially, with more participatory programmes requiring higher levels of adaptive management. This study evaluates the effectiveness of a volunteer-based CE programme developed in Haiti in 2018. The approach was based on local leaders organizing and implementing monthly anti-malaria activities in their communities, and was implemented as part of Malaria Zero Consortium activities.
    METHODS: This programme evaluation draws on quantitative and qualitative data collected from 23 Community Health Councils (CHCs) over a two-year period (2019-2021) in Grand'Anse department, a malaria hotspot region in Haiti.
    RESULTS: Monthly monitoring data showed that 100% of the 23 CHCs remained functional over the two-year period, with an average of 0.90 monthly meetings held with an 85% attendance rate. A high degree of transparency and diversity in membership helped create strong planning and involvement from members. CHCs conducted an average of 1.6 community-based activities per month, directly engaging an average of 123 people per month. High levels of fluctuation in monthly activities were indicative of local ownership and self-organization. This included school and church sensitization, environmental sanitation campaigns, mass education, support for case referrals and community mobilization during mass drug administration (MDA) and indoor residual spraying (IRS) campaigns. Members drew on the tradition of konbit (mutual self-help), local histories of health and development campaigns and a lexicon of "solidarity" in difficult times as they negotiated their agency as community volunteers. Small incentives played both symbolic and supportive roles. Some level of politicization was viewed as inevitable, even beneficial. Rumours about financial and political profiteering of CHC volunteers took time to dispel while the tendency towards vertical planning in malaria control created conditions that excluded CHCs from some activities. This generated resentment from members who felt sidelined by the government malaria programme.
    CONCLUSION: The CHC model was effective in promoting group solidarity and community-based anti-malaria activities over a two-year period in Haiti. With the end of the Malaria Zero Consortium in early 2021, there is now an opportunity to better integrate this programme into the primary healthcare system, evaluate the impact of the CHCs on malaria epidemiology, and promote the greater integration of CHCs with active surveillance and response activities.
    Keywords:  Community engagement; Haiti; Malaria elimination; Participation; Vector control
    DOI:  https://doi.org/10.1186/s12936-023-04471-z
  10. J Med Entomol. 2023 Feb 08. pii: tjad009. [Epub ahead of print]
    Characterizing the Vector Data Ecosystem.
    Catherine A Lippi, Samuel S C Rund, Sadie J Ryan.
      A growing body of information on vector-borne diseases has arisen as increasing research focus has been directed towards the need for anticipating risk, optimizing surveillance, and understanding the fundamental biology of vector-borne diseases to direct control and mitigation efforts. The scope and scale of this information, in the form of data, comprising database efforts, data storage, and serving approaches, means that it is distributed across many formats and data types. Data ranges from collections records to molecular characterization, geospatial data to interactions of vectors and traits, infection experiments to field trials. New initiatives arise, often spanning the effort traditionally siloed in specific research disciplines, and other efforts wane, perhaps in response to funding declines, different research directions, or lack of sustained interest. Thusly, the world of vector data - the Vector Data Ecosystem - can become unclear in scope, and the flows of data through these various efforts can become stymied by obsolescence, or simply by gaps in access and interoperability. As increasing attention is paid to creating FAIR (Findable Accessible Interoperable, and Reusable) data, simply characterizing what is 'out there', and how these existing data aggregation and collection efforts interact, or interoperate with each other, is a useful exercise. This study presents a snapshot of current vector data efforts, reporting on level of accessibility, and commenting on interoperability using an illustration to track a specimen through the data ecosystem to understand where it occurs for the database efforts anticipated to describe it (or parts of its extended specimen data).
    Keywords:  database; ecoinformatics; interoperability; mosquito; vector-borne disease
    DOI:  https://doi.org/10.1093/jme/tjad009
  11. J Vector Borne Dis. 2022 Oct-Dec;59(4):59(4): 386-387
    Vaccine against malaria: A ground-breaking step towards elimination in India.
    Sadhvika Kanagat, Abhijit Vinodrao Boratne.
      
    DOI:  https://doi.org/10.4103/0972-9062.355961
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