bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒08‒30
seventeen papers selected by
Richard Halfpenny
Staffordshire University

  1. J Med Entomol. 2020 Aug 23. pii: tjaa157. [Epub ahead of print]
    McGregor BL, Connelly CR.
      Aedes aegypti (L) is an anthropophilic mosquito involved in the transmission of a variety of viral pathogens worldwide including dengue, chikungunya, yellow fever, and Zika viruses. This species, native to Africa, is well established in the continental U.S. (CONUS) and occasionally contributes to localized outbreaks of viral diseases. In the last seven decades, mosquito control programs in the CONUS have been focused on vectors of eastern equine encephalitis, St. Louis encephalitis, and West Nile viruses, as well as nuisance species. Aedes aegypti receives little control focus except during outbreak periods, which has led to a lack of information on appropriate and effective control options targeting Ae. aegypti in the CONUS. As such, in the event of an Ae. aegypti-borne arboviral outbreak in the CONUS, there are limited evidence-based control recommendations or protocols in place. Autochthonous outbreaks of Ae. aegypti-borne pathogens have occurred recently in the CONUS, including dengue outbreaks in 2010 and 2013, a chikungunya outbreak in 2014, and the 2016 outbreak of Zika virus. The increasing frequency of Ae. aegypti-borne outbreaks necessitates increased attention and research on control of this species to prevent and mitigate future outbreaks. This review consolidates and synthesizes the available literature on control of Ae. aegypti, specifically within the CONUS, focusing on data generated through operational applications as well as field and semifield experiments. The purpose of this review is to identify and highlight areas where additional research is needed. The review covers chemical control and insecticide resistance, biological control, source reduction, trapping, and alternative techniques.
    Keywords:   Aedes aegypti ; continental U.S; mosquito control
  2. Front Microbiol. 2020 ;11 1750
    Lu P, Sun Q, Fu P, Li K, Liang X, Xi Z.
      As traditional approaches to the control of dengue and Zika are insufficient, significant efforts have been made to develop utilization of the endosymbiotic bacterium Wolbachia to reduce the ability of mosquitoes to transmit pathogens. Although Wolbachia is known to inhibit flaviviruses in mosquitoes, including dengue virus (DENV) and Zika virus (ZIKV), it remains unclear how the endosymbiont interferes with viral replication cycle. In this study, we have carried out viral binding assays to investigate the impact of the Wolbachia strain wAlbB on the attachment of DENV serotype 2 (DENV-2) and ZIKV to Aedes aegypti Aag-2 cells. RNA interference (RNAi) was used to silence a variety of putative mosquito receptors of DENV that were differentially regulated by wAlbB in Aag-2 cells, in order to identify host factors involved in the inhibition of viral binding. Our results showed that, in addition to suppression of viral replication, Wolbachia strongly inhibited binding of both DENV-2 and ZIKV to Aag-2 cells. Moreover, the expression of two putative mosquito DENV receptors - dystroglycan and tubulin - was downregulated by wAlbB, and their knock-down resulted in the inhibition of DENV-2 binding to Aag-2 cells. These results will aid in understanding the Wolbachia-DENV interactions in mosquito and the development of novel control strategies for mosquito-borne diseases.
    Keywords:  Wolbachia; Zika; dengue; mosquito; viral entry
  3. Front Cell Infect Microbiol. 2020 ;10 407
    Guerrero D, Cantaert T, Missé D.
      Vector-borne diseases are responsible for over a billion infections each year and nearly one million deaths. Mosquito-borne dengue virus, West Nile, Japanese encephalitis, Zika, Chikungunya, and Rift Valley Fever viruses constitute major public health problems in regions with high densities of arthropod vectors. During the initial step of the transmission cycle, vector, host, and virus converge at the bite site, where local immune cells interact with the vector's saliva. Hematophagous mosquito saliva is a mixture of bioactive components known to modulate vertebrate hemostasis, immunity, and inflammation during the insect's feeding process. The capacity of mosquito saliva to modulate the host immune response has been well-studied over the last few decades and has led to the consensus that the presence of saliva is linked to the enhancement of virus transmission, host susceptibility, disease progression, viremia levels, and mortality. We review some of the major aspects of the interactions between mosquito saliva and the host immune response that may be useful for future studies on the control of arboviruses.
    Keywords:  Aedes spp; arbovirus; immune response; mosquito saliva; saliva composition
  4. Parasit Vectors. 2020 Aug 26. 13(1): 430
    Goupeyou-Youmsi J, Rakotondranaivo T, Puchot N, Peterson I, Girod R, Vigan-Womas I, Paul R, Ndiath MO, Bourgouin C.
      BACKGROUND: Malaria is still a heavy public health concern in Madagascar. Few studies combining parasitology and entomology have been conducted despite the need for accurate information to design effective vector control measures. In a Malagasy region of moderate to intense transmission of both Plasmodium falciparum and P. vivax, parasitology and entomology have been combined to survey malaria transmission in two nearby villages.METHODS: Community-based surveys were conducted in the villages of Ambohitromby and Miarinarivo at three time points (T1, T2 and T3) during a single malaria transmission season. Human malaria prevalence was determined by rapid diagnostic tests (RDTs), microscopy and real-time PCR. Mosquitoes were collected by human landing catches and pyrethrum spray catches and the presence of Plasmodium sporozoites was assessed by TaqMan assay.
    RESULTS: Malaria prevalence was not significantly different between villages, with an average of 8.0% by RDT, 4.8% by microscopy and 11.9% by PCR. This was mainly due to P. falciparum and to a lesser extent to P. vivax. However, there was a significantly higher prevalence rate as determined by PCR at T2 ([Formula: see text] = 7.46, P = 0.025). Likewise, mosquitoes were significantly more abundant at T2 ([Formula: see text] = 64.8, P < 0.001), especially in Ambohitromby. At T1 and T3 mosquito abundance was higher in Miarinarivo than in Ambohitromby ([Formula: see text] = 14.92, P < 0.001). Of 1550 Anopheles mosquitoes tested, 28 (1.8%) were found carrying Plasmodium sporozoites. The entomological inoculation rate revealed that Anopheles coustani played a major contribution in malaria transmission in Miarinarivo, being responsible of 61.2 infective bites per human (ib/h) during the whole six months of the survey, whereas, it was An. arabiensis, with 36 ib/h, that played that role in Ambohitromby.
    CONCLUSIONS: Despite a similar malaria prevalence in two nearby villages, the entomological survey showed a different contribution of An. coustani and An. arabiensis to malaria transmission in each village. Importantly, the suspected secondary malaria vector An. coustani, was found playing the major role in malaria transmission in one village. This highlights the importance of combining parasitology and entomology surveys for better targeting local malaria vectors. Such study should contribute to the malaria pre-elimination goal established under the 2018-2022 National Malaria Strategic Plan.
    Keywords:  Andriba; Anopheles arabiensis; Anopheles coustani; Madagascar; Plasmodium falciparum; Plasmodium vivax; Vector biology dynamics
  5. Rev Environ Health. 2020 Aug 24. pii: /j/reveh.ahead-of-print/reveh-2020-0028/reveh-2020-0028.xml. [Epub ahead of print]
    Holeva-Eklund WM, Behrens TK, Hepp CM.
      Aedes aegypti mosquitoes are primary vectors of dengue, yellow fever, chikungunya and Zika viruses. Ae. aegypti is highly anthropophilic and relies nearly exclusively on human blood meals and habitats for reproduction. Socioeconomic factors may be associated with the spread of Ae. aegypti due to their close relationship with humans. This paper describes and summarizes the published literature on the association between socioeconomic variables and the distribution of Ae. aegypti mosquitoes in the mainland United States. A comprehensive search of PubMed/Medline, Scopus, Web of Science, and EBSCO Academic Search Complete through June 12, 2019 was used to retrieve all articles published in English on the association of socioeconomic factors and the distribution of Ae. aegypti mosquitoes. Additionally, a hand search of mosquito control association websites was conducted in an attempt to identify relevant grey literature. Articles were screened for eligibility using the process described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Initially, 3,493 articles were identified through the database searches and previously known literature. After checking for duplicates, 2,145 articles remained. 570 additional records were identified through the grey literature search for a total of 2,715 articles. These articles were screened for eligibility using their titles and abstracts, and 2,677 articles were excluded for not meeting the eligibility criteria. Finally, the full text for each of the remaining articles (n=38) was read to determine eligibility. Through this screening process, 11 articles were identified for inclusion in this review. The findings for these 11 studies revealed inconsistent relationships between the studied socioeconomic factors and the distribution and abundance of Ae. aegypti. The findings of this review suggest a gap in the literature and understanding of the association between anthropogenic factors and the distribution of Ae. aegypti that could hinder efforts to implement effective public health prevention and control strategies should a disease outbreak occur.
    Keywords:  built environment; health equity; insect vectors; public health; social determinants of health
  6. Acta Trop. 2020 Aug 24. pii: S0001-706X(20)30888-3. [Epub ahead of print] 105678
    Gimenez JO, Alvarez CN, Almirón WR, Stein M.
      Aedes aegypti is the main vector of dengue virus in South America. In the last fifteen years, Argentina has suffered three large dengue outbreaks: one in 2009, another one in 2016 and the current 2020 outbreak, with 26,000, 66,000 and more than 43,000 confirmed cases, respectively. These outbreaks are associated with the circulation of the virus in neighboring countries due to the constant movement of people across the frontier. In 2009, the main province affected was Chaco province, with 11,037 confirmed cases (50% of total cases). Thus, the aim of this study was to characterize the temporal oviposition rate of Aedes aegypti in Resistencia, the capital city of this province, in relation to meteorological variables. Mosquitoes were sampled weekly, from April 2015 to March 2017, using ovitraps located in houses randomly selected within the urban area. Oviposition rate was evaluated by means of the total number of eggs collected per week and the proportion of positive ovitraps per week. The coefficient of variation for these two indicators was estimated for the whole study period and then compared using the Wilcoxon Pair test. A generalized linear model (GLM) was performed to infer association between meteorological variables and oviposition rate without time lag and with a time lag of 1 to 4 weeks, considering the biology of this mosquito species. Comparisons between the coefficient of variation of egg number versus the proportion of positive ovitraps showed significant differences, being the former more variable than the latter. The most significant time lag was 2 weeks for the minimum temperature. The number of Ae. aegypti eggs increased 4.05 times when the minimum temperature increased 1°C two weeks before, and decreased 0.69 times with an increase of 1 unit in relative humidity. No eggs were collected when the temperature was below 8°C. The oviposition rate was associated with the increase in the critical minimum temperature (over 8°C) and the weekly frequency of precipitation and dissociated with relative humidity. The maximum oviposition rate was recorded between November and January of both years. The GLM could not explain the relation between meteorological variables and the proportion of positive ovitraps. The peaks of Ae. aegypti egg abundance occurred simultaneously with dengue autochthonous cases recorded in Chaco province, resulting in a good indicative of the period of greatest epidemiological risk.
    Keywords:  Aedes aegypti; Dengue; Northeastern Argentina; Oviposition; Risk
  7. Environ Res. 2020 Sep;pii: S0013-9351(20)30763-5. [Epub ahead of print]188 109868
    Nikookar SH, Fazeli-Dinan M, Enayati A, Zaim M.
      Zika virus is transmitted by Aedes mosquitoes, especially, Ae. aegypti and Ae. albopictus. About 80% of the cases do not manifest any symptoms, and it is a self-limiting, mild viral infection. In 20% of the cases and only in fraction of those who do show the symptoms, important complications including Guillaine Barre'syndrome and microcephaly may occur. The emergence of Zika in 2016 in Brazil spreading to about 70 other countries prompted the WHO officials to declare the disease a Public Health Emergency with International Concern (PHEIC). This has led to increased concerns in health authorities of almost all countries making them embark on the strengthened human and vector surveillance, vector control and clinical management of the disease. Although the main vectors of the disease have not yet been able to establish in Iran, because of their occurrence in neighboring countries as well as increased global travel and trade, the country established a national advisory committee for capacity building, vector and human surveillance and case management of Aedes-borne diseases. This study aims at performing a literature review about global situation of Zika and Aedes mosquitoes, their distribution, biology and ecology from the past to present and the threat posed to Iran. Aedes aegypti was historically present in the checklist of Iranian mosquitoes and Ae. albopictus has recently been collected from Southern Iran, however, the species has apparently failed to establish in the country as comprehensive follow up entomological surveillance could not reproduce the findings. Although Zika was not detected in Iran, considering the expansion in tourism, travel and trade to and from Zika infected and Aedes infested countries, suitable climate and favorable prediction for establishment of Aedes vectors, Iran may well be at risk of invasion of Aedes vector species and the diseases they carry. Therefore, this review is of value particularly to health authorities in Iran and other WHO Eastern Mediterranean countries for sustained vigilance and preparedness for early detection and response, including vector control.
    Keywords:  Aedes; Ecology; Iran; Zika
  8. Epidemiol Serv Saude. 2020 ;pii: S2237-96222020000400701. [Epub ahead of print]29(4): e2020057
    Andrioli DC, Busato MA, Lutinski JA.
      Objective To describe the characteristics of the dengue epidemic in Pinhalzinho, Santa Catarina, Brazil, and to investigate the effects of climate variables on Aedes aegypti mosquito infestation. Methods This was an ecological study using data on dengue cases, hospitalizations and deaths in 2015 and 2016; in addition to climate variables and Aedes aegypti breeding grounds from 2015 to 2018. Results In the 2015-2016 epidemic, the dengue incidence rate was 12,695.2/100,000 inhabitants. Higher incidence was registered in the female sex (13,926.4/100,000 inhabitants) and in the 50 years and over age group (17,162.0/100,000 inhabitants). Average temperature and relative humidity showed a positive relationship with increase in Aedes aegypti breeding grounds. Conclusion Dengue incidence during the epidemic was the highest ever recorded in the country. Climate conditions must be considered when planning vector control and dengue prevention actions.
  9. PLoS Negl Trop Dis. 2020 Aug;14(8): e0008428
    Sim S, Ng LC, Lindsay SW, Wilson AL.
      Vector-borne diseases are a major cause of morbidity and mortality worldwide. Aedes-borne diseases, in particular, including dengue, chikungunya, yellow fever, and Zika, are increasing at an alarming rate due to urbanisation, population movement, weak vector control programmes, and climate change. The World Health Organization calls for strengthening of vector control programmes in line with the Global Vector Control Response (GVCR) strategy, and many vector control programmes are transitioning to this new approach. The Singapore dengue control programme, situated within the country's larger vision of a clean, green, and sustainable environment for the health and well-being of its citizens, provides an excellent example of the GVCR approach in action. Since establishing vector control operations in the 1960s, the Singapore dengue control programme succeeded in reducing the dengue force of infection 10-fold by the 1990s and has maintained it at low levels ever since. Key to this success is consideration of dengue as an environmental disease, with a strong focus on source reduction and other environmental management methods as the dominant vector control strategy. The programme collaborates closely with other government ministries, as well as town councils, communities, the private sector, and academic and research institutions. Community engagement programmes encourage source reduction, and house-to-house inspections accompanied by a strong legislative framework with monetary penalties help to support compliance. Strong vector and epidemiological surveillance means that routine control activities can be heightened to specifically target dengue clusters. Despite its success, the programme continues to innovate to tackle challenges such as climate change, low herd immunity, and manpower constraints. Initiatives include development of novel vector controls such as Wolbachia-infected males and spatiotemporal models for dengue risk assessment. Lessons learnt from the Singapore programme can be applied to other settings, even those less well-resourced than Singapore, for more effective vector control.
  10. Genome Biol. 2020 Aug 26. 21(1): 215
    Palatini U, Masri RA, Cosme LV, Koren S, Thibaud-Nissen F, Biedler JK, Krsticevic F, Johnston JS, Halbach R, Crawford JE, Antoshechkin I, Failloux AB, Pischedda E, Marconcini M, Ghurye J, Rhie A, Sharma A, Karagodin DA, Jenrette J, Gamez S, Miesen P, Masterson P, Caccone A, Sharakhova MV, Tu Z, Papathanos PA, Van Rij RP, Akbari OS, Powell J, Phillippy AM, Bonizzoni M.
      BACKGROUND: The Asian tiger mosquito Aedes albopictus is globally expanding and has become the main vector for human arboviruses in Europe. With limited antiviral drugs and vaccines available, vector control is the primary approach to prevent mosquito-borne diseases. A reliable and accurate DNA sequence of the Ae. albopictus genome is essential to develop new approaches that involve genetic manipulation of mosquitoes.RESULTS: We use long-read sequencing methods and modern scaffolding techniques (PacBio, 10X, and Hi-C) to produce AalbF2, a dramatically improved assembly of the Ae. albopictus genome. AalbF2 reveals widespread viral insertions, novel microRNAs and piRNA clusters, the sex-determining locus, and new immunity genes, and enables genome-wide studies of geographically diverse Ae. albopictus populations and analyses of the developmental and stage-dependent network of expression data. Additionally, we build the first physical map for this species with 75% of the assembled genome anchored to the chromosomes.
    CONCLUSION: The AalbF2 genome assembly represents the most up-to-date collective knowledge of the Ae. albopictus genome. These resources represent a foundation to improve understanding of the adaptation potential and the epidemiological relevance of this species and foster the development of innovative control measures.
    Keywords:  Ae. albopictus; Developmental transcriptome; Genome; Immunity; Population differentiation; Sex locus; Viral integrations; miRNAs; piRNA clusters
  11. Methods Ecol Evol. 2019 Aug;10(8): 1274-1285
    Faiman R, Dao A, Yaro AS, Diallo M, Djibril S, Sanogo ZL, Ousmane Y, Sullivan M, Veru L, Krajacich BJ, Krishna A, Matthews J, France CAM, Hamer G, Hobson KA, Lehmann T.
      Background: 1.Tracking mosquitoes using current methods of mark-release-recapture are limited to small spatial and temporal scales exposing major gaps in understanding long-range movements and extended survival. Novel approaches to track mosquitoes may yield fresh insights into their biology which improves intervention activities to reduce disease transmission.Stable isotope enrichment of natural mosquito breeding sites allows large-scale marking of wild mosquitoes absent human handling. Mosquito larvae that develop in 2H-enriched water are expected to be detectable for over four months using tissue mass-fraction 2H measurements, providing opportunities for long-term mark-capture studies on a large scale.Approach: 2.A laboratory study followed by a field experiment of mosquito larval habitat 2H-enrichment was conducted in Mali, to evaluate potential labeling of wild mosquitoes. Twelve natural larval sites were enriched using [2H]-Deuterium-oxide (D2O, 99%). Enrichment level was maintained by supplementation following dilution by rains. Availability of 2H to mosquito larvae was enhanced by locally collected and cultured microorganisms (i.e. protozoa, algae and bacteria) reared in deuterated water, and provided as larval diet. Putative natural predators were removed from the larval sites and first instar larvae Anopheles gambiae s.l. larvae were added every other day. Emergence traps enabled collection of eclosing adults. Adult mosquitoes were kept at laboratory conditions for analysis of label attrition with age.
    Results: 3.Deuterium enrichment of wild mosquitoes above background levels (maximum = 143.1 ppm) became apparent 5-6 days after initial exposure, after which 2H values increased steadily until ~24 days later (to a mean of approx. 220 ppm). Anopheles and Culex mosquitoes showed significantly different 2H values (211 and 194.2 ppm respectively). Both genera exhibited exponential label attrition (e (-x)) amounting to 21.6% by day 30 post emergence, after which attrition rate continuously decreased. Males of both taxa exhibited a higher mean 2H value compared to females.
    Conclusions: 4.Deuterium-oxide proved useful in marking mosquitoes in their natural larval sites and although costly, may prove valuable for studies of mosquitoes and other aquatic insects. Based on our field study, we provide a protocol for marking mosquito larval sites using deuterium-oxide.
    Keywords:  Anopheles gambiae; deuterium; mark-capture; stable isotopes; vector dispersal
  12. Proc Natl Acad Sci U S A. 2020 Aug 24. pii: 202010214. [Epub ahead of print]
    Carballar-Lejarazú R, Ogaugwu C, Tushar T, Kelsey A, Pham TB, Murphy J, Schmidt H, Lee Y, Lanzaro GC, James AA.
      A Cas9/guide RNA-based gene drive strain, AgNosCd-1, was developed to deliver antiparasite effector molecules to the malaria vector mosquito, Anopheles gambiae The drive system targets the cardinal gene ortholog producing a red-eye phenotype. Drive can achieve 98 to 100% in both sexes and full introduction was observed in small cage trials within 6 to 10 generations following a single release of gene-drive males. No genetic load resulting from the integrated transgenes impaired drive performance in the trials. Potential drive-resistant target-site alleles arise at a frequency <0.1, and five of the most prevalent polymorphisms in the guide RNA target site in collections of colonized and wild-derived African mosquitoes do not prevent cleavage in vitro by the Cas9/guide RNA complex. Only one predicted off-target site is cleavable in vitro, with negligible deletions observed in vivo. AgNosCd-1 meets key performance criteria of a target product profile and can be a valuable component of a field-ready strain for mosquito population modification to control malaria transmission.
    Keywords:  cage trials; guide RNA polymorphisms; load; nontarget; off-target
  13. Vector Borne Zoonotic Dis. 2020 Aug 20.
    Brindicci G, Santoro CR, Loconsole D, Martinelli D, Prato R, Lonero G, Loperfido P, Buccoliero GB, Chironna M.
      Background: Italy was declared malaria free by the World Health Organization in 1970. Despite this, nonimport malaria cases are on the increase in Italy and throughout the Mediterranean area. In Italy, in the period between 2011 and 2015, seven cases of locally acquired malaria have been reported, including one introduced case of Plasmodium vivax; moreover, the last certain case of introduced malaria (by P. vivax) has been reported in Tuscany in 1997. No case of introduced malaria from Plasmodium falciparum has been reported in Italy since 1970. Case Presentation: A cluster of four cryptic P. falciparum malaria cases were ascertained in migrant farm workers (three from Morocco and one from Sudan) in Apulia (southern Italy) with clinical onset between September 20 and 27, 2017. None of the patients reported a history of a recent trip to malaria-endemic areas or hospitalization or other risk factors. Typing of malaria was also confirmed using molecular biology methods in two different laboratories. There were no cases of severe malaria in our four patients, and only one in need of transfusion. All patients were discharged cured after being treated with mefloquine due to the unavailability of other antimalarials. Conclusions: In recent years, numerous reports of locally acquired malaria have been made in southern Europe. The cases described in this article represent the first cluster of malaria caused by P. falciparum in Europe. Today, clinical presentation in the diagnosis of malaria is more important than ever, since epidemiological criterion cannot be considered unfailing. The mode of transmission has not been proven and further biological and entomological studies are necessary to define our case as cryptic or confirm the presence of mosquitoes capable of transmitting P. falciparum and/or the capacity of Anopheles labranchiae, An. superpictus, or An. plumbeus to transmit it on Italian territory.
    Keywords:  Plasmodium falciparum; cluster of locally acquired malaria; south Italy
  14. Malar J. 2020 Aug 26. 19(1): 301
    Kgoroebutswe TK, Makate N, Fillinger U, Mpho M, Segoea G, Sangoro PO, Mutero CM, Chanda E, Ntebela D, Mogopa M, Mosweunyane T, Nkya TE.
      Botswana has in the recent past 10 years made tremendous progress in the control of malaria and this informed re-orientation from malaria control to malaria elimination by the year 2020. This progress is attributed to improved case management, and scale-up of key vector control interventions; indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs). However, insecticide resistance, outdoor biting and resting, and predisposing human behaviour, such as staying outdoors or sleeping outdoors without the use of protective measures, pose a challenge to the realization of the full impact of LLINs and IRS. This, together with the paucity of entomological data, inadequate resources and weak community participation for vector control programme implementation delayed attainment of Botswana's goal of malaria elimination. Also, the Botswana National Malaria Programme (NMP) experiences the lack of intersectoral collaborations and operational research for evidence-based decision making. This case study focuses on the vector control aspect of malaria elimination by identifying challenges and explores opportunities that could be taken advantage of to benefit the NMP to optimize and augment the current vector control interventions to achieve malaria elimination by the year 2030 as per the Global Technical Strategy for Malaria 2016-2030 targets. The authors emphasize the need for timely and quality entomological surveillance, operational research and integrated vector management.
    Keywords:  Elimination; Entomology; Integrated vector management; Malaria
  15. Proc Natl Acad Sci U S A. 2020 Aug 25. pii: 202006781. [Epub ahead of print]
    Moyes CL, Athinya DK, Seethaler T, Battle KE, Sinka M, Hadi MP, Hemingway J, Coleman M, Hancock PA.
      Malaria vector control may be compromised by resistance to insecticides in vector populations. Actions to mitigate against resistance rely on surveillance using standard susceptibility tests, but there are large gaps in the monitoring data across Africa. Using a published geostatistical ensemble model, we have generated maps that bridge these gaps and consider the likelihood that resistance exceeds recommended thresholds. Our results show that this model provides more accurate next-year predictions than two simpler approaches. We have used the model to generate district-level maps for the probability that pyrethroid resistance in Anopheles gambiae s.l. exceeds the World Health Organization thresholds for susceptibility and confirmed resistance. In addition, we have mapped the three criteria for the deployment of piperonyl butoxide-treated nets that mitigate against the effects of metabolic resistance to pyrethroids. This includes a critical review of the evidence for presence of cytochrome P450-mediated metabolic resistance mechanisms across Africa. The maps for pyrethroid resistance are available on the IR Mapper website, where they can be viewed alongside the latest survey data.
    Keywords:  insecticide resistance; insecticide resistance management; malaria control; metabolic resistance; pyrethroid
  16. Science. 2020 Aug 28. 369(6507): 1123-1128
    Katzelnick LC, Narvaez C, Arguello S, Lopez Mercado B, Collado D, Ampie O, Elizondo D, Miranda T, Bustos Carillo F, Mercado JC, Latta K, Schiller A, Segovia-Chumbez B, Ojeda S, Sanchez N, Plazaola M, Coloma J, Halloran ME, Premkumar L, Gordon A, Narvaez F, de Silva AM, Kuan G, Balmaseda A, Harris E.
      The Zika pandemic sparked intense interest in whether immune interactions among dengue virus serotypes 1 to 4 (DENV1 to -4) extend to the closely related Zika virus (ZIKV). We investigated prospective pediatric cohorts in Nicaragua that experienced sequential DENV1 to -3 (2004 to 2015), Zika (2016 to 2017), and DENV2 (2018 to 2020) epidemics. Risk of symptomatic DENV2 infection and severe disease was elevated by one prior ZIKV infection, one prior DENV infection, or one prior DENV infection followed by one ZIKV infection, compared with being flavivirus-naïve. By contrast, multiple prior DENV infections reduced dengue risk. Further, although high preexisting anti-DENV antibody titers protected against DENV1, DENV3, and ZIKV disease, intermediate titers induced by previous ZIKV or DENV infection enhanced future risk of DENV2 disease and severity, as well as DENV3 severity. The observation that prior ZIKV infection can modulate dengue disease severity like a DENV serotype poses challenges to development of dengue and Zika vaccines.
  17. Med Biol Eng Comput. 2020 Aug 26.
    de Araújo APR, de Araujo MCM, Cavalcanti TC, de Lacerda Vidal CF, da Silva MGNM.
      Dengue, Zika, and chikungunya are epidemic diseases transmitted by the Aedes mosquito. These virus infections can be so severe to the point of bringing on mobility and neurological problems, or even death. Expert systems (ES) can be used as tools for the identification of patterns intended to solve problems in the same way as a professional specialist would. This work aimed to develop an ES in the form of an Android application to serve as a supportive tool in the diagnosis of these arboviruses. The goal is to associate the set of symptoms from a patient to a score related to the likelihood of them having these diseases. To make this possible, we implemented a rule-based ES which considers the presence of symptoms itself and the relation between them to associate the case under analysis to others found in the literature. We performed 96 tests (32 for each illness), and our system had a success rate of 96.88%. Resident physicians of a public hospital also analyzed these clinical cases and achieved an average success rate of 72.92%. Comparing the results of the method proposed and errors made by health professionals, we showed an improvement in the effectiveness of clinical diagnoses. Graphical abstract Figure - DZC DIAG Operating Flowchart: the physicians record patients' data and answer a series of questions related to the patient's symptoms; after all the questions, the result is generated by the expert system (score for dengue, Zika, and chikungunya); and it is saved in the same device where the test was done and uploaded online to a FTP.
    Keywords:  Chikungunya virus; Dengue; Expert system; Zika virus; mHealth