bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022‒02‒13
nineteen papers selected by
Richard Halfpenny
Staffordshire University
  1. The tiger mosquito in Lebanon two decades after its introduction: A growing health concern.
  2. Aedes mosquitoes in the emerging threat of urban yellow fever transmission.
  3. Silent circulation of Zika and dengue virus in Aedes aegypti (Diptera: Culicidae) during a non-epidemic year in the state of Sergipe, northeastern Brazil.
  4. Monitoring of synthetic insecticides resistance and mechanisms among malaria vector mosquitoes in Iran: A systematic review.
  5. Detection and population genetic analysis of kdr L1014F variant in eastern Ethiopian Anopheles stephensi.
  6. The Fauna, Diversity, and Bionomics of Culicinae (Diptera: Culicidae) in Hormozgan Province, Southern Iran.
  7. Surveillance and genetic data support the introduction and establishment of Aedes albopictus in Iowa, USA.
  8. Articulating ethical principles guiding Target Malaria's engagement strategy.
  9. Current status of insecticide resistance in malaria vectors in the Asian countries: a systematic review.
  10. Why did the Wolbachia transinfection cross the road? drift, deterministic dynamics, and disease control.
  11. Seroprevalence of dengue, Zika, chikungunya and Ross River viruses across the Solomon Islands.
  12. Abiotic factors affecting the prevalence of Wolbachia (Rickettsiaceae) in immature Aedes albopictus (Skuse) (Culicidae).
  13. Influence of abiotic factors on the oviposition of Aedes (Stegomyia) aegypti (Diptera: Culicidae) in Northern Paraná, Brazil.
  14. Reemergence of yellow fever virus in southeastern Brazil, 2017-2018: What sparked the spread?
  15. Stegomyia indices of Aedes aquatic stages in El Geneina town, Western Sudan.
  16. Cross-sectional study of asymptomatic malaria and seroepidemiological surveillance of seven districts in Gia Lai province, Vietnam.
  17. Trends and Spatial Pattern Analysis of Dengue Cases in Northeast Malaysia.
  18. The triple epidemics of arboviruses in Feira de Santana, Brazilian Northeast: Epidemiological characteristics and diffusion patterns.
  19. Mark-release-recapture experiment in Burkina Faso demonstrates reduced fitness and dispersal of genetically-modified sterile malaria mosquitoes.
  1. PLoS Negl Trop Dis. 2022 Feb 09. 16(2): e0010206
    The tiger mosquito in Lebanon two decades after its introduction: A growing health concern.
    Nabil Haddad, Hayssam Omran, Fadila Amraoui, Renée Zakhia, Laurence Mousson, Anna-Bella Failloux.
      The tiger mosquito was introduced to the Eastern region of the Mediterranean basin more than twenty years ago. In Lebanon, it was first observed in 2002 in a limited number of locations mainly from the coastal area of the country. In the absence of national entomological control program, this invasive mosquito became an established species and is now considered in many localities, a source of nuisance because of its human biting behavior. Several entomological surveys were conducted to monitor the geographic spread and the seasonal dynamics of Aedes albopictus by collecting adult stages and by monitoring oviposition activity. Moreover, its susceptibility to the common groups of insecticides was assessed using WHO standard bioassays. Previous vector competence studies revealed that local strains were able to transmit Chikungunya and Dengue viruses. Due to the increased risk of Zika virus introduction in the country, we determined the competence of local populations to transmit this virus. Mapping results showed that Ae. albopictus is mainly spread in the relatively humid western versant of the Mount Lebanon chain reaching 1000m altitude, while it is absent from arid and semi-arid inland areas. Besides, this mosquito is active during 32 weeks from spring till the end of autumn. Local strains of the tiger mosquito are susceptible to pyrethroids and carbamates but resistant to organophosphates and organochlorines. They showed ability to transmit Zika virus; however, only 9% of females were capable to excrete the virus in their saliva at day 28 post infection. Current and previous observations highlight the need to establish a surveillance system in order to control this mosquito and monitor the potential introduction of related diseases.
    DOI:  https://doi.org/10.1371/journal.pntd.0010206
  2. Rev Med Virol. 2022 Feb 06. e2333
    Aedes mosquitoes in the emerging threat of urban yellow fever transmission.
    Gaelle Gabiane, Pei-Shi Yen, Anna-Bella Failloux.
      This last decade has seen a resurgence of yellow fever (YF) in historical endemic regions and repeated attempts of YF introduction in YF-free countries such as the Asia-Pacific region and the Caribbean. Infected travellers are the main entry routes in these regions where competent mosquito vectors proliferate in appropriate environmental conditions. With the discovery of the 17D vaccine, it was thought that YF would be eradicated. Unfortunately, it was not the case and, contrary to dengue, chikungunya and Zika, factors that cotribute to YF transmission remain under investigation. Today, all the signals are red and it is very likely that YF will be the next pandemic in the YF-free regions where millions of people are immunologically naïve. Unlike COVID-19, YF is associated with a high case-fatality rate and a high number of deaths are expected. This review gives an overview of global YF situation, including the non-endemic Asia-Pacific region and the Caribbean where Aedes aegypti is abundantly distributed, and also proposes different hypotheses on why YF outbreaks have not yet occurred despite high records of travellers importing YF into these regions and what role Aedes mosquitoes play in the emergence of urban YF.
    Keywords:  Aedes mosquitoes; risk assessment; yellow fever
    DOI:  https://doi.org/10.1002/rmv.2333
  3. Trans R Soc Trop Med Hyg. 2022 Feb 10. pii: trac009. [Epub ahead of print]
    Silent circulation of Zika and dengue virus in Aedes aegypti (Diptera: Culicidae) during a non-epidemic year in the state of Sergipe, northeastern Brazil.
    Myrela C S Jesus, Rynat D O Chagas, Matheus L J Santos, Rafaela W F Santos, Roseli La Corte, Luciane M Storti-Melo.
      BACKGROUND: Dengue virus (DENV) and Zika virus (ZIKV) have a severe impact on human health worldwide. To understand the dynamics of these viruses in mosquito populations, it is necessary to maintain surveillance during non-epidemic years.METHODS: We aimed to assess the presence of DENV and ZIKV in Aedes aegypti females in the state of Sergipe, northeastern Brazil, during a non-epidemic year. The Ae. aegypti females collected were sectioned, and the heads and thorax were used to analyze the infection rate. Each female was first analyzed to detect Flavivirus using RT-PCR. Flavivirus-positive samples were further screened to detect ZIKV and DENV types 1, 2, 3 and 4.
    RESULTS: A total of 184 females were collected. ZIKV was identified in 5.4% of the sample and DENV in 7.1%, with the DENV-positive samples belonging to subtypes 2, 3 and 4. The presence of coinfected vectors was also observed. Of the four cities tested, only one was negative for all viruses.
    CONCLUSIONS: These results show that the maintenance of vigilance during non-epidemic years can provide data on viruses circulating before the onset of outbreaks. This can enable the planning and implementation of local control measures to prevent the appearance of new outbreaks.
    Keywords:   Flavivirus ; arboviruses; medical entomology; vector surveillance
    DOI:  https://doi.org/10.1093/trstmh/trac009
  4. Heliyon. 2022 Jan;8(1): e08830
    Monitoring of synthetic insecticides resistance and mechanisms among malaria vector mosquitoes in Iran: A systematic review.
    Ebrahim Abbasi, Mozaffar Vahedi, Masoumeh Bagheri, Saber Gholizadeh, Hamzeh Alipour, Mohammad Djaefar Moemenbellah-Fard.
      Background: In Iran, the prospect of malaria control relies mainly on insecticides used against the genus Anopheles (Diptera: Culicidae) as important vectors of malaria, arboviruses, and so on. Only eight out of 30 malaria mosquito vectors (Anopheles species) have been examined for insecticide resistance in Iran. This study aimed to review articles related to the incremental trend in insecticide resistance and their mechanisms among anopheline malaria vectors in Iran.Methods: A literature review was conducted based on such search engines as Iran doc, Web of Science, SID, PubMed, Scopus, and Google Scholar websites using the following keywords: "Anopheles," "Malaria," "Resistance," "Vectors," "Insecticide Resistance," and "Iran" for data collection. Published papers in English or Persian covering 1980 to 2020 were reviewed.
    Results: A total of 1125 articles were screened, only 16 of which were filtered to be pertinent in this review. While most of the mosquito vectors of malaria, such as Anopheles stephensi, were resistant to DDT, dieldrin, malathion, and becoming less susceptible to deltamethrin and other synthetic pyrethroid insecticides, few like Anopheles fluviatilis s. l. were susceptible to all insecticides. A disseminating trend in insecticide resistance among different anopheline mosquito vector species was evident. Metabolic and insecticide target-site resistance mechanisms were involved with organochlorines and pyrethroids, respectively.
    Conclusions: Insecticide resistance is becoming a severe scourge to the effectiveness of vector-borne disease management measures. This event is especially critical in developing and marginalized communities that applied chemical-based vector elimination programs for malaria; therefore, it is crucial to monitor insecticide resistance in malaria vectors in Iran using biochemical and molecular tools.
    Keywords:  Anophelinae; Carbamate; Knock-down resistance; Organophosphate; Pyrethrum
    DOI:  https://doi.org/10.1016/j.heliyon.2022.e08830
  5. Infect Genet Evol. 2022 Feb 02. pii: S1567-1348(22)00032-6. [Epub ahead of print] 105235
    Detection and population genetic analysis of kdr L1014F variant in eastern Ethiopian Anopheles stephensi.
    Jeanne N Samake, Solomon Yared, Dejene Getachew, Peter Mumba, Dereje Dengela, Gedeon Yohannes, Sheleme Chibsa, Sae Hee Choi, Joseph Spear, Seth R Irish, Sarah Zohdy, Meshesha Balkew, Tamar E Carter.
      Anopheles stephensi is a malaria vector that has been recently introduced into East Africa, where it threatens to increase malaria disease burden. The use of insecticides, especially pyrethroids, is still one of the primary malaria vector control strategies worldwide. The knockdown resistance (kdr) mutation in the IIS6 transmembrane segment of the voltage-gated sodium channel (vgsc) is one of the main molecular mechanisms of pyrethroid resistance in Anopheles. Extensive pyrethroid resistance in An. stephensi has been previously reported in Ethiopia. Thus, it is important to determine whether or not the kdr mutation is present in An. stephensi populations in Ethiopia to inform vector control strategies. In the present study, the kdr locus was analyzed in An. stephensi collected from ten urban sites (Awash Sebat Kilo, Bati, Dire Dawa, Degehabur, Erer Gota, Godey, Gewane, Jigjiga, Semera, and Kebridehar) situated in Somali, Afar, and Amhara regions, and Dire Dawa Administrative City, to evaluate the frequency and evolution of kdr mutations and the association of the mutation with permethrin resistance phenotypes. Permethrin is one of the pyrethroid insecticides used for vector control in eastern Ethiopia. DNA extractions were performed on adult mosquitoes from CDC light trap collections and those raised from larval and pupal collections. PCR and targeted sequencing were used to analyze the IIS6 transmembrane segment of the vgsc gene. Of 159 An. stephensi specimens analyzed from the population survey, nine (5.7%) carried the kdr mutation (L1014F). An. stephensi with kdr mutations were only observed from Bati, Degehabur, Dire Dawa, Gewane, and Semera. We further randomly selected twenty resistant and twenty susceptible An. stephensi mosquitoes from Dire Dawa post-exposure to permethrin and investigated the role of kdr in pyrethroid resistance by comparing the vgsc gene in the two populations. We found no kdr mutations in the permethrin-resistant mosquitoes. Population genetic analysis of the sequences, including neighboring introns, revealed limited evidence of non-neutral evolution (e.g., selection) at this locus. The low kdr mutation frequency detected and the lack of kdr mutation in the permethrin-resistant mosquitoes suggest the existence of other molecular mechanisms of pyrethroid resistance in eastern Ethiopian An. stephensi.
    Keywords:  An. Stephensi; Insecticide resistance; Invasive mosquito; Kdr mutation; L1014F; Malaria
    DOI:  https://doi.org/10.1016/j.meegid.2022.105235
  6. J Med Entomol. 2022 Feb 03. pii: tjac003. [Epub ahead of print]
    The Fauna, Diversity, and Bionomics of Culicinae (Diptera: Culicidae) in Hormozgan Province, Southern Iran.
    Seyed-Aghil Jaberhashemi, Shahyad Azari-Hamidian, Aboozar Soltani, Kourosh Azizi, Hedayat Dorzaban, Mojtaba Norouzi, Elaheh Daghighi.
      Hormozgan Province is one of the important foci of malaria in Iran. In addition to malaria pathogens, mosquitoes also transmit the pathogens that cause dirofilariasis and West Nile fever in the province. Also, the threat of emerging aedine-borne viruses that cause infections, such as Chikungunya, dengue, and Zika, is noticeable. There is little information about the fauna and bionomics of Culicinae in the province. The present investigation aimed to study the fauna, diversity, and bionomics of culicines. The study was conducted from September 2016 to April 2017 in four counties of Bandar Abbas, Bandar Khamir, Bashagard, and Jask. In total, 3,236 larvae and 1,901 adults including 16 culicine species were collected. The larvae of Culiseta longiareolata (Macquart) (25.65%), Culex pipiens Linnaeus (16.62%), and Cx. quinquefasciatus Say (16.16%) were most abundant and Cx. hortensis Ficalbi (0.09%) was least abundant. Among adults, Cx. laticinctus Edwards (33.19%), Cx. quinquefasciatus (31.09%), and Cx. pipiens (11.99%) were the most prevalent species and Cs. longiareolata (0.47%), Aedes caballus (Theobald) (0.90%), and Cx. bitaeniorhynchus Giles (0.90%) were the least prevalent species. The pairwise similarities of fauna of the counties and different collecting methods and diversity indices were investigated. More ecological data, especially on host preference, seasonality, and larval habitat characteristics, are needed as a basic knowledge for any intervention measures using integrated vector management.
    Keywords:   Aedes ; Culex ; Culiseta ; altitude; ecology
    DOI:  https://doi.org/10.1093/jme/tjac003
  7. Sci Rep. 2022 Feb 08. 12(1): 2143
    Surveillance and genetic data support the introduction and establishment of Aedes albopictus in Iowa, USA.
    David R Hall, Ryan E Tokarz, Eleanor N Field, Ryan C Smith.
      Aedes albopictus is a competent vector of several arboviruses that has spread throughout the United States over the last three decades. With the emergence of Zika virus in the Americas in 2015-2016 and an increased need to understand the current distributions of Ae. albopictus in the US, we initiated surveillance efforts to determine the abundance of invasive Aedes species in Iowa. Here, we describe surveillance efforts from 2016 to 2020 in which we detect stable and persistent populations of Aedes albopictus in three Iowa counties. Based on temporal patterns in abundance and genetic analysis of mitochondrial DNA haplotypes between years, our data support that Ae. albopictus are overwintering and have likely become established in the state. The localization of Ae. albopictus predominantly in areas of urbanization, and noticeable absence in rural areas, suggests that these ecological factors may contribute to overwintering success. Together, these data document the establishment of Ae. albopictus in Iowa and their expansion into the Upper Midwest, where freezing winter temperatures were previously believed to limit their spread. With impending climate change, our study provides evidence for the further expansion of Ae. albopictus into temperate regions of the United States resulting in increased risks for vector-borne disease transmission.
    DOI:  https://doi.org/10.1038/s41598-022-06294-5
  8. Malar J. 2022 Feb 05. 21(1): 35
    Articulating ethical principles guiding Target Malaria's engagement strategy.
    Aaron J Roberts, Delphine Thizy.
      Progress in gene drive research has engendered a lively discussion about community engagement and the ethical standards the work hinges on. While there is broad agreement regarding ethical principles and established best practices for conducting clinical public health research, projects developing area-wide vector control technologies and initiating ambitious engagement strategies raise specific questions: who to engage, when to engage, and how? When responding to these fundamental questions, with few best practices available for guidance, projects need to reflect on and articulate the ethical principles that motivate and justify their approach. Target Malaria is a not-for-profit research consortium that aims to develop and share malaria control and elimination technology. The consortium is currently investigating the potential of a genetic technique called gene drive to control populations of malaria vectoring mosquito species Anopheles gambiae. Due to the potentially broad geographical, environmental impact of gene drive technology, Target Malaria has committed to a robust form of tailored engagement with the local communities in Burkina Faso, Mali, and Uganda, where research activities are currently taking place. This paper presents the principles guiding Target Malaria's engagement strategy. Herein the authors (i) articulate the principles; (ii) explain the rationale for selecting them; (iii) share early lessons about the application of the principles. Since gene drive technology is an emerging technology, with few best practices available for guidance, the authors hope by sharing these lessons, to add to the growing literature regarding engagement strategies and practices for area-wide vector control, and more specifically, for gene drive research.
    Keywords:  Co-development; Ethics; Gene drive; Malaria; Responsible research; Stakeholder engagement; Vector control
    DOI:  https://doi.org/10.1186/s12936-022-04062-4
  9. F1000Res. 2021 ;10 200
    Current status of insecticide resistance in malaria vectors in the Asian countries: a systematic review.
    Dewi Susanna, Dian Pratiwi.
      Background : The application of insecticides for malaria vector control has remained a global problem, due to the current trend of increased resistance against these chemicals. This study aims to determine the insecticide-resistant status in Asia and how to implement the necessary interventions. Moreover, the implications of resistance in malaria vector control in this region were studied. Methods: This systematic review was conducted using a predefined protocol based on PRISMA-retrieved articles from four science databases, namely ProQuest, Science Direct, EBSCO, and PubMed in the last ten years (2009 to 2019). The searching process utilized four main combinations of the following keywords: malaria, vector control, insecticide, and Asia. In ProQuest, malaria control, as well as an insecticide, were used as keywords. The following criteria were included in the filter, namely full text, the source of each article, scholarly journal, Asia, and publication date as in the last ten years. Results: There were 1408 articles retrieved during the initial search (ProQuest=722, Science Direct=267, EBSCO=50, PubMed=285, and Scopus=84). During the screening, 27 articles were excluded because of duplication, 1361 based on title and abstract incompatibility with the inclusion criteria, and 20 due to content differences. In the final screening process, 15 articles were chosen to be analyzed. From the 15 articles, it is known that there was dichlorodiphenyltrichloroethane (DDT) and pyrethroids resistance in several anopheles species with a mortality rate of less than 80%. Conclusion s : The report on the pyrethroid resistance was complicated, since this insecticide was considered effective in malaria vector control. Therefore, several strategies were required, including the management plans in selecting insecticides, using a rotation system during interventions in the field, regular monitoring, and integrating vector control based on physics, chemistry, and biology. All of these need to be supported by cross-sector policies and cooperation in achieving the 2030 malaria-free target.
    Keywords:  Anopheles; Malaria Elimination; Vector Control Program; Insecticide Resistance; Asian Countries
    DOI:  https://doi.org/10.12688/f1000research.46883.1
  10. Evol Lett. 2022 Feb;6(1): 92-105
    Why did the Wolbachia transinfection cross the road? drift, deterministic dynamics, and disease control.
    Michael Turelli, Nicholas H Barton.
      Maternally inherited Wolbachia transinfections are being introduced into natural mosquito populations to reduce the transmission of dengue, Zika, and other arboviruses. Wolbachia-induced cytoplasmic incompatibility provides a frequency-dependent reproductive advantage to infected females that can spread transinfections within and among populations. However, because transinfections generally reduce host fitness, they tend to spread within populations only after their frequency exceeds a critical threshold. This produces bistability with stable equilibrium frequencies at both 0 and 1, analogous to the bistability produced by underdominance between alleles or karyotypes and by population dynamics under Allee effects. Here, we analyze how stochastic frequency variation produced by finite population size can facilitate the local spread of variants with bistable dynamics into areas where invasion is unexpected from deterministic models. Our exemplar is the establishment of wMel Wolbachia in the Aedes aegypti population of Pyramid Estates (PE), a small community in far north Queensland, Australia. In 2011, wMel was stably introduced into Gordonvale, separated from PE by barriers to A. aegypti dispersal. After nearly 6 years during which wMel was observed only at low frequencies in PE, corresponding to an apparent equilibrium between immigration and selection, wMel rose to fixation by 2018. Using analytic approximations and statistical analyses, we demonstrate that the observed fixation of wMel at PE is consistent with both stochastic transition past an unstable threshold frequency and deterministic transformation produced by steady immigration at a rate just above the threshold required for deterministic invasion. The indeterminacy results from a delicate balance of parameters needed to produce the delayed transition observed. Our analyses suggest that once Wolbachia transinfections are established locally through systematic introductions, stochastic "threshold crossing" is likely to only minimally enhance spatial spread, providing a local ratchet that slightly-but systematically-aids area-wide transformation of disease-vector populations in heterogeneous landscapes.
    Keywords:  Aedes aegypti; bistable dynamics; disease control; hybrid zone movement; migration‐induced transformation; population structure; population transformation; shifting balance theory; stochastic transitions
    DOI:  https://doi.org/10.1002/evl3.270
  11. PLoS Negl Trop Dis. 2022 Feb 10. 16(2): e0009848
    Seroprevalence of dengue, Zika, chikungunya and Ross River viruses across the Solomon Islands.
    Tanya L Russell, Paul F Horwood, Humpress Harrington, Allan Apairamo, Nathan J Kama, Albino Bobogare, David MacLaren, Thomas R Burkot.
      Across the Pacific, and including in the Solomon Islands, outbreaks of arboviruses such as dengue, chikungunya, and Zika are increasing in frequency, scale and impact. Outbreaks of mosquito-borne disease have the potential to overwhelm the health systems of small island nations. This study mapped the seroprevalence of dengue, Zika, chikungunya and Ross River viruses in 5 study sites in the Solomon Islands. Serum samples from 1,021 participants were analysed by ELISA. Overall, 56% of participants were flavivirus-seropositive for dengue (28%), Zika (1%) or both flaviviruses (27%); and 53% of participants were alphavirus-seropositive for chikungunya (3%), Ross River virus (31%) or both alphaviruses (18%). Seroprevalence for both flaviviruses and alphaviruses varied by village and age of the participant. The most prevalent arboviruses in the Solomon Islands were dengue and Ross River virus. The high seroprevalence of dengue suggests that herd immunity may be a driver of dengue outbreak dynamics in the Solomon Islands. Despite being undetected prior to this survey, serology results suggest that Ross River virus transmission is endemic. There is a real need to increase the diagnostic capacities for each of the arboviruses to support effective case management and to provide timely information to inform vector control efforts and other outbreak mitigation interventions.
    DOI:  https://doi.org/10.1371/journal.pntd.0009848
  12. J Invertebr Pathol. 2022 Feb 03. pii: S0022-2011(22)00015-5. [Epub ahead of print] 107730
    Abiotic factors affecting the prevalence of Wolbachia (Rickettsiaceae) in immature Aedes albopictus (Skuse) (Culicidae).
    Ana C Alonso, Marina Stein, Carlos Matías Hisgen, María V Micieli.
      Wolbachia is a genus of gram-negative endosymbiotic bacterium of maternal transmission, located mainly in the gonads of arthropods, including mosquitoes such as Aedes albopictus. The current distribution of Ae. albopictus in Argentina is restricted to the subtropical northeastern region of the country. Here, we studied the seasonal prevalence of Wolbachia detected in Ae. albopictus larvae and the relationship between the abiotic factors of the larval microhabitat and the infection status, in Eldorado city, Misiones province, subtropical region. The prevalence of Wolbachia infection found was 76.89% (n=312). From the total samples examined, 52.80% (n=214) showed double infection with the wAlbA/wAlbB strains, 23.84% (n=97) infection only with wAlbB, and 0.25% (n=1) only with wAlbA. The prevalence of double infection did not present statistically significant differences between the sites studied. For single infection, the lowest prevalence value of the wAlbB strain (13.33%) was found in the natural park, whereas the highest was found in the family dwellings and cemeteries. Tire repair shops showed an intermediate value. The wAlbA single infection was identified once. Our results also showed an association between temperature and slightly turbid waters with exposure to the sun in the larval habitats and the probability of infection by Wolbachia.
    Keywords:  Wolbachia - Mosquitoes - Aedes albopictus - Prevalence
    DOI:  https://doi.org/10.1016/j.jip.2022.107730
  13. Int J Trop Insect Sci. 2022 Feb 04. 1-6
    Influence of abiotic factors on the oviposition of Aedes (Stegomyia) aegypti (Diptera: Culicidae) in Northern Paraná, Brazil.
    Juliana Freitas do Nascimento, Graciana Freitas Palioto-Pescim, Rodrigo Rossetto Pescim, Marcio Seiji Suganuma, João Antonio Cyrino Zequi, Halison Correia Golias.
      Aedes aegypti is the main vector of dengue in the Americas and is also a transmitter of urban yellow fever arboviruses, Zika, and Chikungunya, all of which have substantial economic impacts on the affected countries. Through mathematical models, the influence of climatic factors on the oviposition of Ae. aegypti was determined. The data were collected in the city of Apucarana, Paraná State, using oviposition traps. Daily data were submitted to a negative binomial regression model (p < 0.05). The analyses were performed using the R statistical program to determine the climatic factors that most influenced oviposition. A Poisson regression showed that the variables temperature, atmospheric pressure, humidity, and precipitation significantly increased the number of eggs. However, using the semi-normal probability graph with a simulation envelope, it was determined that the Poisson regression model was not adequate to explain the relationships between the variables. Thus, a negative binomial regression model was used, which overcame the problem of overdispersion, and showed that only temperature affected the increase in the number of eggs, where an increase of 1 °C was expected to result in a 54.03% increase in the number of Ae. aegypti eggs.
    Keywords:  Climatic factors; Negative Regression; Ovitrap; Poisson Regression; Vector monitoring
    DOI:  https://doi.org/10.1007/s42690-022-00742-5
  14. PLoS Negl Trop Dis. 2022 Feb 07. 16(2): e0010133
    Reemergence of yellow fever virus in southeastern Brazil, 2017-2018: What sparked the spread?
    Joelle I Rosser, Karin Nielsen-Saines, Eduardo Saad, Trevon Fuller.
      BACKGROUND: The 2017-2018 yellow fever virus (YFV) outbreak in southeastern Brazil marked a reemergence of YFV in urban states that had been YFV-free for nearly a century. Unlike earlier urban YFV transmission, this epidemic was driven by forest mosquitoes. The objective of this study was to evaluate environmental drivers of this outbreak.METHODOLOGY/PRINCIPAL FINDINGS: Using surveillance data from the Brazilian Ministry of Health on human and non-human primate (NHP) cases of YFV, we traced the spatiotemporal progression of the outbreak. We then assessed the epidemic timing in relation to drought using a monthly Standardized Precipitation Evapotranspiration Index (SPEI) and evaluated demographic risk factors for rural or outdoor exposure amongst YFV cases. Finally, we developed a mechanistic framework to map the relationship between drought and YFV. Both human and NHP cases were first identified in a hot, dry, rural area in northern Minas Gerais before spreading southeast into the more cool, wet urban states. Outbreaks coincided with drought in all four southeastern states of Brazil and an extreme drought in Minas Gerais. Confirmed YFV cases had an increased odds of being male (OR 2.6; 95% CI 2.2-3.0), working age (OR: 1.8; 95% CI: 1.5-2.1), and reporting any recent travel (OR: 2.8; 95% CI: 2.3-3.3). Based on this data as well as mosquito and non-human primate biology, we created the "Mono-DrY" mechanistic framework showing how an unusual drought in this region could have amplified YFV transmission at the rural-urban interface and sparked the spread of this epidemic.
    CONCLUSIONS/SIGNIFICANCE: The 2017-2018 YFV epidemic in Brazil originated in hot, dry rural areas of Minas Gerais before expanding south into urban centers. An unusually severe drought in this region may have created environmental pressures that sparked the reemergence of YFV in Brazil's southeastern cities.
    DOI:  https://doi.org/10.1371/journal.pntd.0010133
  15. East Mediterr Health J. 2021 Dec 28. 27(12): 1189-1196
    Stegomyia indices of Aedes aquatic stages in El Geneina town, Western Sudan.
    Hamid Hamid, Hiba Musa, Adla Ahmed, Tayseer Abdul Azeez, Asma Adam, Mwahib Abdel Malik, Azeeza El Tahir, Hmooda Kafy, Rasha Azrag.
      Background: Darfur in Western Sudan has the most volatile camps of internally displaced persons (IDPs) and has experienced several outbreaks of dengue, chikungunya and yellow fever.Aims: To determine the prevalence and Stegomyia indices of Aedes aquatic stages in El Geneina town, Western Darfur.
    Methods: Cross-sectional entomological surveys of immature stages of Aedes were carried out during August-November 2019 in 4 sites with IDP camps and a residential area with no camp.
    Results: We searched 17 730 houses, IDP camps and buildings of governmental corporations for Aedes larvae, and 6809 (38.4%) were positive for Aedes aquatic stages. Both Aedes aegypti and Aedes vittatus larvae were found. However, Ae. aegypti constituted > 90% of the larvae. Six positive water containers were recorded: tyres, clay pots, barrels, plastic water tanks, flower vases and old cars: 26% of 92 tyres contained Aedes larvae compared to 23.8% of 21 old cars and 17.1% of 44 198 clay pots. This suggested that clay pots were the main source of Aedes. The results showed high infestation of El Geneina town with Aedes immature stages in all study sites including public buildings and residential areas with no IDP camps. Stegomyia indices varied among study sites, and were more elevated in sites with IDP camps. For all sites, House index = 38.40, Container Index = 11.40, Breateu index = 13.60 and Pupa Index = 27.
    Conclusion: Multisectoral response coupled with community participation are urgently needed to reduce the burden of Aedes-borne diseases in the unstable El Geneina town.
    DOI:  https://doi.org/10.26719/emhj.21.073
  16. Malar J. 2022 Feb 08. 21(1): 40
    Cross-sectional study of asymptomatic malaria and seroepidemiological surveillance of seven districts in Gia Lai province, Vietnam.
    Nguyen Ngoc San, Nguyen Xuan Kien, Nguyen Duc Manh, Nguyen Van Thanh, Marina Chavchich, Nguyen Thi Huong Binh, Tran Khanh Long, Kimberly A Edgel, Eduard Rovira-Vallbona, Michael D Edstein, Nicholas J Martin.
      BACKGROUND: Malaria elimination by 2030 is an aim of many countries in the Greater Mekong Sub-region, including Vietnam. However, to achieve this goal and accelerate towards malaria elimination, countries need to determine the extent and prevalence of asymptomatic malaria as a potential reservoir for malaria transmission and the intensity of malaria transmission. The purpose of this study was to determine the prevalence of asymptomatic malaria and seropositivity rate in several districts of Gia Lai province in the Central Highlands of Vietnam.METHODS: A cross-sectional survey of asymptomatic malaria and serological testing was conducted in 3283 people living at 14 communes across seven districts in Gia Lai province in December 2016 to January 2017. Finger prick capillary blood samples were tested for malaria using rapid diagnostic testing and polymerase chain reaction (PCR), as well as detecting antibodies against 3 Plasmodium falciparum and 4 Plasmodium vivax antigens by indirect enzyme-linked immunosorbent assay (ELISA). Age-seroprevalence curves were fitted using reverse catalytic models with maximum likelihood.
    RESULTS: The study population was predominantly male (65.9%, 2165/3283), adults (88.7%, 2911/3283) and of a minority ethnicity (72.2%, 2371/3283), with most participants being farmers and outdoor government workers (90.2%, 2960/3283). Using a small volume of blood (≈ 10 µL) the PCR assay revealed that 1.74% (57/3283) of the participants had asymptomatic malaria (P. falciparum 1.07%, P. vivax 0.40%, Plasmodium malariae 0.15% and mixed infections 0.12%). In contrast, the annual malaria prevalence rates for clinical malaria in the communities where the participants lived were 0.12% (108/90,395) in 2016 and 0.22% (201/93,184) in 2017. Seropositivity for at least one P. falciparum or one P. vivax antigen was 38.5% (1257/3262) and 31.1% (1022/3282), respectively. Age-dependent trends in the proportion of seropositive individuals in five of the districts discriminated the three districts with sustained low malaria prevalence from the two districts with higher transmission.
    CONCLUSIONS: Asymptomatic Plasmodium carriers were found to be substantially more prevalent than clinical cases in seven districts of Gia Lai province, and a third of the population had serological evidence of previous malaria exposure. The findings add knowledge on the extent of asymptomatic malaria and transmission for developing malaria elimination strategies for Vietnam.
    Keywords:  Asymptomatic malaria; Drug resistance; Gia Lai province; PCR; Plasmodium falciparum; Plasmodium vivax; Serology; Vietnam
    DOI:  https://doi.org/10.1186/s12936-022-04060-6
  17. J Prev Med Public Health. 2022 Jan;55(1): 80-87
    Trends and Spatial Pattern Analysis of Dengue Cases in Northeast Malaysia.
    Afiqah Syamimi Masrani, Nik Rosmawati Nik Husain, Kamarul Imran Musa, Ahmad Syaarani Yasin.
      OBJECTIVES: Dengue remains hyperendemic in Malaysia despite extensive vector control activities. With dynamic changes in land use, urbanisation and population movement, periodic updates on dengue transmission patterns are crucial to ensure the implementation of effective control strategies. We sought to assess shifts in the trends and spatial patterns of dengue in Kelantan, a north-eastern state of Malaysia (5°15'N 102°0'E).METHODS: This study incorporated data from the national dengue monitoring system (eDengue system). Confirmed dengue cases registered in Kelantan with disease onset between January 1, 2016 and December 31, 2018 were included in the study. Yearly changes in dengue incidence were mapped by using ArcGIS. Hotspot analysis was performed using Getis-Ord Gi to track changes in the trends of dengue spatial clustering.
    RESULTS: A total of 10 645 dengue cases were recorded in Kelantan between 2016 and 2018, with an average of 10 dengue cases reported daily (standard deviation, 11.02). Areas with persistently high dengue incidence were seen mainly in the coastal region for the 3-year period. However, the hotspots shifted over time with a gradual dispersion of hotspots to their adjacent districts.
    CONCLUSIONS: A notable shift in the spatial patterns of dengue was observed. We were able to glimpse the shift of dengue from an urban to peri-urban disease with the possible effect of a state-wide population movement that affects dengue transmission.
    Keywords:  Dengue; Disease hot spot; Incidence studies; Malaysia; Spatial analysis
    DOI:  https://doi.org/10.3961/jpmph.21.461
  18. Epidemics. 2022 Feb 01. pii: S1755-4365(22)00004-4. [Epub ahead of print]38 100541
    The triple epidemics of arboviruses in Feira de Santana, Brazilian Northeast: Epidemiological characteristics and diffusion patterns.
    Lacita Menezes Skalinski, Ana Paula Razal Dalvi, Márcio Natividade, José Ueleres Braga, Maria da Conceição Nascimento Costa, Eloisa Bahia Santana, Neuza Santos de Jesus Silva, Jimmy Witworth, Maria Glória Teixeira.
      Arboviruses are diseases of worldwide importance in the field of communicable diseases. In Brazil, the reemergence of dengue and the emergence of chikungunya and Zika since 2014 have led to epidemic waves of great magnitude and rapid spread. However, their diffusion patterns vary and change over time. This study analyzes the spatial diffusion of the simultaneous circulation of three arboviruses transmitted by the same vector in a large urban space over two epidemic waves in consecutive years. An ecological study of spatial and temporal aggregates on the occurrence of dengue, chikungunya, and Zika, from 2014 to 2019, in Feira de Santana, Bahia State, was carried out using data of cases reported to the national surveillance system. Four different methods were used to analyze the spatial diffusion: Kernel Estimation with sequential maps, cumulative nearest-neighbor ratios (NNI) over time, spatial correlograms and local autocorrelation changes (LISA) over time. From 2014-2019, there were 21,723 confirmed cases of arboviruses. The highest incidences were among women (496.9, 220.2, and 91.0 cases/100,000 women for dengue, chikungunya and Zika respectively). By age group, the highest incidences were from ages 10-19 years old (609.3 dengue cases/100,000), from 60 and more (306.7 chikungunya cases/100,000), and from 0-9 years old (124.1 Zika cases/100,000 inhabitants). The temporal distribution demonstrated two epidemic waves of simultaneous circulation in 2014 and 2015. Kernel maps indicate that arboviruses spread to neighboring areas near the first hotspots, suggesting an expansion diffusion pattern. The NNI, spatial correlograms and LISA changes results suggest expansion patterns for the three arboviruses in all periods. The spatial diffusion pattern of dengue, Zika, and chikungunya in the 2014-2015 epidemics in Feira de Santana was expansion. These findings are useful to guide prevention measures and reduce occurrence in other areas.
    Keywords:  Arbovirus infections; Epidemics; Spatial Analysis
    DOI:  https://doi.org/10.1016/j.epidem.2022.100541
  19. Nat Commun. 2022 Feb 10. 13(1): 796
    Mark-release-recapture experiment in Burkina Faso demonstrates reduced fitness and dispersal of genetically-modified sterile malaria mosquitoes.
    Franck Adama Yao, Abdoul-Azize Millogo, Patric Stephane Epopa, Ace North, Florian Noulin, Koulmaga Dao, Mouhamed Drabo, Charles Guissou, Souleymane Kekele, Moussa Namountougou, Robert Kossivi Ouedraogo, Lea Pare, Nourou Barry, Roger Sanou, Haida Wandaogo, Roch K Dabire, Andrew McKemey, Frederic Tripet, Abdoulaye Diabaté.
      Every year, malaria kills approximately 405,000 people in Sub-Saharan Africa, most of them children under the age of five years. In many countries, progress in malaria control has been threatened by the rapid spread of resistance to antimalarial drugs and insecticides. Novel genetic mosquito control approaches could play an important role in future integrated malaria control strategies. In July 2019, the Target Malaria consortium proceeded with the first release of hemizygous genetically-modified (GM) sterile and non-transgenic sibling males of the malaria mosquito Anopheles coluzzii in Burkina Faso. This study aimed to determine the potential fitness cost associated to the transgene and gather important information related to the dynamic of transgene-carrying mosquitoes, crucial for next development steps. Bayesian estimations confirmed that GM males had lower survival and were less mobile than their wild type (WT) siblings. The estimated male population size in Bana village, at the time of the release was 28,000 - 37,000. These results provide unique information about the fitness and behaviour of released GM males that will inform future releases of more effective strains of the A. gambiae complex.
    DOI:  https://doi.org/10.1038/s41467-022-28419-0
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