bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022‒12‒25
nineteen papers selected by
Richard Halfpenny
Staffordshire University
  1. Mosquitoes and Mosquito-Borne Diseases in Vietnam.
  2. Assessing the efficacy of male Wolbachia-infected mosquito deployments to reduce dengue incidence in Singapore: study protocol for a cluster-randomized controlled trial.
  3. Arbovirus persistence in North-Western Europe: Are mosquitoes the only overwintering pathway?
  4. Impact of physicochemical parameters of Aedes aegypti breeding habitats on mosquito productivity and the size of emerged adult mosquitoes in Ouagadougou City, Burkina Faso.
  5. Vector Competence of Mosquitoes from Germany for Sindbis Virus.
  6. Insecticide Resistance Profile and Mechanisms in An. gambiae s.l. from Ebolowa, South Cameroon.
  7. Malaria transmission in Nepal under climate change: anticipated shifts in extent and season, and comparison with risk definitions for intervention.
  8. Vector Competence of German Aedes punctor (Kirby, 1837) for West Nile Virus Lineages 1 and 2.
  9. The effects of climate factors, population density, and vector density on the incidence of dengue hemorrhagic fever in South Jakarta Administrative City 2016-2020: an ecological study.
  10. Mosquito Fauna and Spatial Distribution in an Atlantic Forest Area in Rio de Janeiro State, Brazil, Reveal a High Risk of Transmission of Yellow Fever and Other Arboviruses.
  11. Invasion Pattern of Aedes aegypti in the Native Range of Ae. albopictus in Vietnam Revealed by Biogeographic and Population Genetic Analysis.
  12. Discovery of super-insecticide-resistant dengue mosquitoes in Asia: Threats of concomitant knockdown resistance mutations.
  13. Is Asian tiger mosquito (Aedes albopictus) going to become homodynamic in Southern Europe in the next decades due to climate change?
  14. Re-Introduction of West Nile Virus Lineage 1 in Senegal from Europe and Subsequent Circulation in Human and Mosquito Populations between 2012 and 2021.
  15. Modelling the West Nile virus force of infection in the European human population.
  16. Anopheles albimanus is a Potential Alphavirus Vector in the Americas.
  17. Estimating the Distribution of Japanese Encephalitis Vectors in Australia Using Ecological Niche Modelling.
  18. Epidemiology and costs of dengue in Thailand: A systematic literature review.
  19. An African West Nile virus risk map for travellers and clinicians.
  1. Insects. 2022 Nov 22. pii: 1076. [Epub ahead of print]13(12):
    Mosquitoes and Mosquito-Borne Diseases in Vietnam.
    Ly Na Huynh, Long Bien Tran, Hong Sang Nguyen, Van Hoang Ho, Philippe Parola, Xuan Quang Nguyen.
      Mosquito-borne diseases pose a significant threat to humans in almost every part of the world. Key factors such as global warming, climatic conditions, rapid urbanisation, frequent human relocation, and widespread deforestation significantly increase the number of mosquitoes and mosquito-borne diseases in Vietnam, and elsewhere around the world. In southeast Asia, and notably in Vietnam, national mosquito control programmes contribute to reducing the risk of mosquito-borne disease transmission, however, malaria and dengue remain a threat to public health. The aim of our review is to provide a complete checklist of all Vietnamese mosquitoes that have been recognised, as well as an overview of mosquito-borne diseases in Vietnam. A total of 281 mosquito species of 42 subgenera and 22 genera exist in Vietnam. Of those, Anopheles, Aedes, and Culex are found to be potential vectors for mosquito-borne diseases. Major mosquito-borne diseases in high-incidence areas of Vietnam include malaria, dengue, and Japanese encephalitis. This review may be useful to entomological researchers for future surveys of Vietnamese mosquitoes and to decision-makers responsible for vector control tactics.
    Keywords:  Aedes; Anopheles; Anophelinae; Culex; Culicidae; Culicinae; Vietnam; vector
    DOI:  https://doi.org/10.3390/insects13121076
  2. Trials. 2022 Dec 17. 23(1): 1023
    Assessing the efficacy of male Wolbachia-infected mosquito deployments to reduce dengue incidence in Singapore: study protocol for a cluster-randomized controlled trial.
    Janet Ong, Soon Hoe Ho, Stacy Xin Hui Soh, Yvonne Wong, Youming Ng, Kathryn Vasquez, Yee Ling Lai, Yin Xiang Setoh, Chee-Seng Chong, Vernon Lee, Judith Chui Ching Wong, Cheong Huat Tan, Shuzhen Sim, Lee Ching Ng, Jue Tao Lim.
      BACKGROUND: Dengue is a severe environmental public health challenge in tropical and subtropical regions. In Singapore, decreasing seroprevalence and herd immunity due to successful vector control has paradoxically led to increased transmission potential of the dengue virus. We have previously demonstrated that incompatible insect technique coupled with sterile insect technique (IIT-SIT), which involves the release of X-ray-irradiated male Wolbachia-infected mosquitoes, reduced the Aedes aegypti population by 98% and dengue incidence by 88%. This novel vector control tool is expected to be able to complement current vector control to mitigate the increasing threat of dengue on a larger scale. We propose a multi-site protocol to study the efficacy of IIT-SIT at reducing dengue incidence.METHODS/DESIGN: The study is designed as a parallel, two-arm, non-blinded cluster-randomized (CR) controlled trial to be conducted in high-rise public housing estates in Singapore, an equatorial city-state. The aim is to determine whether large-scale deployment of male Wolbachia-infected Ae. aegypti mosquitoes can significantly reduce dengue incidence in intervention clusters. We will use the CR design, with the study area comprising 15 clusters with a total area of 10.9 km2, covering approximately 722,204 residents in 1713 apartment blocks. Eight clusters will be randomly selected to receive the intervention, while the other seven will serve as non-intervention clusters. Intervention efficacy will be estimated through two primary endpoints: (1) odds ratio of Wolbachia exposure distribution (i.e., probability of living in an intervention cluster) among laboratory-confirmed reported dengue cases compared to test-negative controls and (2) laboratory-confirmed reported dengue counts normalized by population size in intervention versus non-intervention clusters.
    DISCUSSION: This study will provide evidence from a multi-site, randomized controlled trial for the efficacy of IIT-SIT in reducing dengue incidence. The trial will provide valuable information to estimate intervention efficacy for this novel vector control approach and guide plans for integration into national vector control programs in dengue-endemic settings.
    TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT05505682 . Registered on 16 August 2022. Retrospectively registered.
    DOI:  https://doi.org/10.1186/s13063-022-06976-5
  3. One Health. 2023 Jun;16 100467
    Arbovirus persistence in North-Western Europe: Are mosquitoes the only overwintering pathway?
    Rody Blom, Maarten J J Schrama, Jeroen Spitzen, Babette F M Weller, Anne van der Linden, Reina S Sikkema, Marion P G Koopmans, Constantianus J M Koenraadt.
      In some areas in temperate Europe, genomic analyses of mosquito-borne virus outbreaks have revealed the presence of similar virus strains over several years, indicating local overwintering of these viruses. However, it remains unclear how mosquito-borne viruses can persist in winter, when conditions are generally unfavourable for virus circulation. One of the presumed routes of virus persistence is via diapausing mosquitoes. Here, we set out to study whether arbovirus persistence of West Nile virus (WNV), Usutu virus (USUV) and Sindbis virus (SINV) occurs in diapausing mosquitoes in the Netherlands. To this end, mosquito collections were carried out in the winter of 2020 and 2021, in hibernacula located in two areas with previously observed WNV and/or USUV activity. In total, we collected 4200 mosquitoes belonging to four species (Culex pipiens, Culiseta annulata, Anopheles maculipennis s.l., and Culex territans), which were pooled in 490 monospecific pools. These pools were subjected to WNV-, USUV- and SINV-screening using a multiplex real-time RT-PCR assay. All mosquito pools tested negative for the presence of WNV, USUV and SINV RNA. Consequently, we did not find evidence of arbovirus persistence in diapausing mosquitoes in the Netherlands, even though USUV and WNV have re-appeared in birds and/or mosquitoes during the summer seasons of 2020-2022. Concluding, given the persistence of USUV and WNV in the Netherlands and SINV in other temperate regions, this study highlights the importance of further research on (alternative) arbovirus overwintering routes.
    Keywords:  Culex pipiens; Diapause; Sindbis virus; Usutu virus; West Nile virus
    DOI:  https://doi.org/10.1016/j.onehlt.2022.100467
  4. Parasit Vectors. 2022 Dec 20. 15(1): 478
    Impact of physicochemical parameters of Aedes aegypti breeding habitats on mosquito productivity and the size of emerged adult mosquitoes in Ouagadougou City, Burkina Faso.
    Wendegoudi Mathias Ouédraogo, Kobié Hyacinthe Toé, Aboubacar Sombié, Mafalda Viana, Clarisse Bougouma, Antoine Sanon, David Weetman, Philip J McCall, Hirotaka Kanuka, Athanase Badolo.
      BACKGROUND: Outbreaks of dengue fever caused by viruses transmitted by Aedes aegypti mosquitoes are repeated occurrences in West Africa. In recent years, Burkina Faso has experienced major dengue outbreaks, most notably in 2016 and 2017 when 80% of cases were recorded in Ouagadougou City (Central Health Region). In order to better understand the ecology of this vector and to provide information for use in developing control measures, a study on the characteristics of Aedes container breeding sites and the productivity of such sites, as measured by the abundance of immature stages and resultant adult body size, was undertaken in three health districts (Baskuy, Bogodogo and Nongremassom) of Ouagadougou.METHODS: Adult mosquitoes were collected indoors and outdoors in 643 households during the rainy season from August to October 2018. The presence of water containers was systematically recorded and the containers examined for the presence or absence of larvae. Characteristics of the container breeding sites, including size of the container and temperature, pH and conductivity of the water contained within, were recorded as well as the volume of water. Traditional Stegomyia indices were calculated as quantitative indicators of the risk of dengue outbreaks; generalised mixed models were fitted to larval and pupal densities, and the contribution of each covariate to the model was evaluated by the Z-value and associated P-value.
    RESULTS: A total of 1061 container breeding sites were inspected, of which 760 contained immature stages of Ae. aegypti ('positive' containers). The most frequent container breeding sites found in each health district were tyres and both medium (buckets/cans/pots) and large (bins/barrels/drums) containers; these containers were also the most productive larval habitats and the types that most frequently tested positive. Of the Stegomyia indices, the Breteau, House and Container indices exceeded WHO dengue risk thresholds. Generalised linear mixed models showed that larval and pupal abundances were associated with container type, physicochemical characteristics of the water and collection month, but there were significant differences among container types and among health districts. Aedes aegypti body size was positively associated with type and diameter of the container, as well as with electrical conductivity of the water, and negatively associated with pH and temperature of the water and with the level of exposure of the container to sunlight.
    CONCLUSION: This study provides data on putative determinants of the productivity of habitats regarding Ae. aegypti immature stages. These data are useful to better understand Ae. aegypti proliferation. The results suggest that identifying and targeting the most productive container breeding sites could contribute to dengue vector control strategies in Burkina Faso.
    Keywords:  Ae. aegypti; Body size; Breeding sites; Dengue; Larvae; Pupae; Stegomyia index
    DOI:  https://doi.org/10.1186/s13071-022-05558-3
  5. Viruses. 2022 Nov 26. pii: 2644. [Epub ahead of print]14(12):
    Vector Competence of Mosquitoes from Germany for Sindbis Virus.
    Stephanie Jansen, Renke Lühken, Michelle Helms, Björn Pluskota, Wolf Peter Pfitzner, Sandra Oerther, Norbert Becker, Jonas Schmidt-Chanasit, Anna Heitmann.
      Transmission of arthropod-borne viruses (arboviruses) are an emerging global health threat in the last few decades. One important arbovirus family is the Togaviridae, including the species Sindbis virus within the genus Alphavirus. Sindbis virus (SINV) is transmitted by mosquitoes, but available data about the role of different mosquito species as potent vectors for SINV are scarce. Therefore, we investigated seven mosquito species, collected from the field in Germany (Ae. koreicus, Ae. geniculatus, Ae. sticticus, Cx. torrentium, Cx. pipiens biotype pipiens) as well as lab strains (Ae. albopictus, Cx. pipiens biotype molestus, Cx. quinquefasciatus), for their vector competence for SINV. Analysis was performed via salivation assay and saliva was titrated to calculate the amount of infectious virus particles per saliva sample. All Culex and Aedes species were able to transmit SINV. Transmission could be detected at all four investigated temperature profiles (of 18 ± 5 °C, 21 ± 5 °C, 24 ± 5 °C or 27 ± 5 °C), and no temperature dependency could be observed. The concentration of infectious virus particles per saliva sample was in the same range for all species, which may suggest that all investigated mosquito species are able to transmit SINV in Germany.
    Keywords:  Aedes and Culex mosquitoes; Sindbis virus; saliva titration; vector competence
    DOI:  https://doi.org/10.3390/v14122644
  6. Insects. 2022 Dec 08. pii: 1133. [Epub ahead of print]13(12):
    Insecticide Resistance Profile and Mechanisms in An. gambiae s.l. from Ebolowa, South Cameroon.
    Salomon Efa, Emmanuel Elanga-Ndille, Yacouba Poumachu, Billy Tene, Jacqueline Ze Mikande, Njoumémi Zakariaou, Charles S Wondji, Cyrille Ndo.
      Monitoring the trend of insecticide resistance and understanding associated genetic mechanisms is important for designing efficient malaria vector control strategies. This study was conducted to provide temporal data on insecticide resistance status and mechanisms in the major malaria vector Anopheles gambiae s.l. from Ebolowa, Southern Cameroon.METHODS: Larvae of An. gambiae s.l. were collected from typical breeding sites throughout the city and reared to adulthood. Emerging adults were morphologically identified and WHO tube assays were performed to determine their susceptibility to carbamate, organophosphate and pyrethroid insecticides at diagnostic doses. When resistance was observed, its intensity was determined by performing WHO tube tests using 5 and 10 times the concentration of the diagnostic dose. Metabolic resistance mechanisms were investigated using insecticide-synergist assays. Sibling species of the An. gambiae complex were identified using SINE-PCR protocol. TaqMan assay was used to genotype the L1014F and L1014S kdr mutations, and the N1575Y mutation, an amplifier of the resistance conferred by the L1014F mutation.
    RESULTS: Anopheles coluzzii was by far the dominant (99%) member of the An. gambiae s.l. complex in Ebolowa. The species was fully susceptible to carbamates and organophosphates, but resistant to all pyrethroid insecticides tested. Resistance was of moderate intensity for deltamethrin (mortality: 37%, 70% and 99% for 1×, 5× and 10× insecticide concentration, respectively) but rather of high intensity for permethrin (5% for 1×; 62% for 5× and 75% for 10×) and for alphacypermethrin (4.4% for 1×; 57% for 5× and 80% for 10×). Pre-exposure to the synergist PBO resulted in a full recovery of the susceptibility to delthametrin, but this was not observed for the other two pyrethroids tested. L1014S (kdr-East) and the N1575Y mutations were absent, whereas the L1014F (kdr-West) mutation was present at a high frequency (75%), showing a significant association with resistance to permethrin (OR = 3.8; 95%; CI [1.9-7.4]; p < 0.0001) and alphacypermethrin (OR = 3; 95%; CI [1.6-5.4]; p = 0.0002).
    CONCLUSION: The increased resistance of An. gambiae s.l. to pyrethroid insecticides as observed in Ebolowa poses a threat to the efficacy of LLINs used to protect populations from the bites of Anopheles mosquitoes that transmit malaria parasites. The present study further highlights the urgent need to implement resistance management strategies in order to maintain the effectiveness of insecticide-based vector control interventions and prevent a rebound in malaria-related mortality.
    Keywords:  Anopheles gambiae s.l.; Ebolowa; carbamates; insecticide resistance; organophosphates; pyrethroids
    DOI:  https://doi.org/10.3390/insects13121133
  7. Malar J. 2022 Dec 22. 21(1): 390
    Malaria transmission in Nepal under climate change: anticipated shifts in extent and season, and comparison with risk definitions for intervention.
    Shreejana Bhattarai, Jason K Blackburn, Sadie J Ryan.
      BACKGROUND: Climate and climate change affect the spatial pattern and seasonality of malaria risk. Season lengths and spatial extents of mapped current and future malaria transmission suitability predictions for Nepal were assessed for a combination of malaria vector and parasites: Anopheles stephensi and Plasmodium falciparum (ASPF) and An. stephensi and Plasmodium vivax (ASPV) and compared with observed estimates of malaria risk in Nepal.METHODS: Thermal bounds of malaria transmission suitability for baseline (1960-1990) and future climate projections (RCP 4.5 and RCP 8.5 in 2030 and 2050) were extracted from global climate models and mapped for Nepal. Season length and spatial extent of suitability between baseline and future climate scenarios for ASPF and ASPV were compared using the Warren's I metric. Official 2010 DoHS risk districts (DRDs) and 2021 DoHS risk wards (DRWs), and spatiotemporal incidence trend clusters (ITCs) were overlaid on suitability season length and extent maps to assess agreement, and potential mismatches.
    RESULTS: Shifts in season length and extent of malaria transmission suitability in Nepal are anticipated under both RCP 4.5 and RCP 8.5 scenarios in 2030 and 2050, compared to baseline climate. The changes are broadly consistent across both future climate scenarios for ASPF and ASPV. There will be emergence of suitability and increasing length of season for both ASPF and ASPV and decreasing length of season for ASPV by 2050. The emergence of suitability will occur in low and no-risk DRDs and outside of high and moderate-risk DRWs, season length increase will occur across all DRD categories, and outside of high and moderate-risk DRWs. The high and moderate risk DRWs of 2021 fall into ITCs with decreasing trend.
    CONCLUSIONS: The study identified areas of Nepal where malaria transmission suitability will emerge, disappear, increase, and decrease in the future. However, most of these areas are anticipated outside of the government's current and previously designated high and moderate-risk areas, and thus outside the focus of vector control interventions. Public health officials could use these anticipated changing areas of malaria risk to inform vector control interventions for eliminating malaria from the country, and to prevent malaria resurgence.
    Keywords:  Anopheles stephensi; Climate change; Elimination; Intervention; Nepal
    DOI:  https://doi.org/10.1186/s12936-022-04417-x
  8. Viruses. 2022 Dec 14. pii: 2787. [Epub ahead of print]14(12):
    Vector Competence of German Aedes punctor (Kirby, 1837) for West Nile Virus Lineages 1 and 2.
    Christin Körsten, Amira A Al-Hosary, Mandy Schäfer, Birke A Tews, Doreen Werner, Helge Kampen, Ana Vasic, Cornelia Silaghi.
      West Nile virus (WNV) is a zoonotic flavivirus transmitted by mosquitoes as a biological vector. Because of its biting behavior, the widespread snow-melt mosquito Aedes punctor could be a potential bridge vector for WNV to humans and nonhuman mammals. However, little is known on its role in transmission of WNV. The aim of this study was to determine the vector competence of German Ae. punctor for WNV lineages 1 and 2. Field-collected larvae and pupae were reared to adults and offered infectious blood containing either an Italian WNV lineage 1 or a German WNV lineage 2 strain via cotton stick feeding. Engorged females were incubated for 14/15 or 21 days at 18 °C. After incubation; surviving mosquitoes were dissected and forced to salivate. Mosquito bodies with abdomens, thoraces and heads, legs plus wings and saliva samples were investigated for WNV RNA by RT-qPCR. Altogether, 2/70 (2.86%) and 5/85 (5.88%) mosquito bodies were found infected with WNV lineage 1 or 2, respectively. In two mosquitoes, viral RNA was also detected in legs and wings. No saliva sample contained viral RNA. Based on these results, we conclude that Ae. punctor does not play an important role in WNV transmission in Germany.
    Keywords:  Aedes punctor; Germany; West Nile virus; vector competence
    DOI:  https://doi.org/10.3390/v14122787
  9. Acta Biomed. 2022 Dec 16. 93(6): e2022323
    The effects of climate factors, population density, and vector density on the incidence of dengue hemorrhagic fever in South Jakarta Administrative City 2016-2020: an ecological study.
    Yuri Shizcha Amelinda, Ririn Arminsih Wulandari, Al Asyary.
      BACKGROUND AND AIM: Dengue hemorrhagic fever (DHF) is an infectious disease caused by the dengue virus (DENV) and is transmitted through the bite of the Aedes aegypti and Aedes albopictus mosquitoes. This study aims to analyze the relationship between the incidence of DHF which can be influenced by climatic factors in the same month (non-time lag), climatic factors with a lag of 1 month (time lag 1), climatic factors with a lag of 2 months (time lag 2), population density, and vector density.METHODS: The study design used is an ecological study. The data is sourced from the South Jakarta City Administration of Health, the South Jakarta City Administration of Central Statistics, and the Meteorology, Climatology and Geophysics Agency. Data were analyzed using correlation test.
    RESULTS: The results showed that the incidence of DHF was related to non-time lag rainfall, time lag 1, and time lag 2, air temperature time lag 2, air humidity non-time lag, time lag 1, and time lag 2, population density, and numbers of mosquito's larvae free index (ABJ).
    CONCLUSIONS: DHF is still a disease that needs to be watched out for in the South Jakarta Administrative City, requiring the government and the people of the South Jakarta Administration to continue to increase efforts to prevent and control DHF.
    DOI:  https://doi.org/10.23750/abm.v93i6.13503
  10. Trop Med Infect Dis. 2022 Nov 30. pii: 410. [Epub ahead of print]7(12):
    Mosquito Fauna and Spatial Distribution in an Atlantic Forest Area in Rio de Janeiro State, Brazil, Reveal a High Risk of Transmission of Yellow Fever and Other Arboviruses.
    Rafaella Moraes de Miranda, Anielly Ferreira-de-Brito, Júlia Dos Santos Silva, Alexandre da Silva Xavier, Shayenne Olsson Freitas Silva, Jeronimo Alencar, Ricardo Lourenço-de-Oliveira.
      In 2017-2019, Brazil recorded its most severe outbreak of yellow fever due to the spread of the virus (YFV) in the country's southeast. Here, we investigated mosquito fauna and the spatial distribution of species in a primatology center in the Atlantic Forest bioregion in Rio de Janeiro state to evaluate the risk of YFV transmission in distinct environments. Fortnightly mosquito collections were performed from December 2018 to December 2019 at 12 sites along a disturbance gradient from a modified environment to 400 m inside the forest. We used ovitraps, BG-Sentinel, and protected human attraction (PHA). A total of 9349 mosquitoes of 21 species were collected. The collection method strongly influenced the captured fauna, with species such as Anopheles cruzii, Psorophora ferox, Runchomyia cerqueirai, Wyeomyia incaudata, Wy. theobaldi, Sabethes chloropterus, and Sa. albiprivus only collected via PHA. Collections with ovitraps resulted in low diversity and richness, with Haemagogus leucocelaenus and Hg. janthinomys/capricornii predominating. The diverse local fauna and the abundance and ubiquity of the latter species, which are the primary vectors of YFV, indicated that this area was highly vulnerable to arbovirus transmission, especially yellow fever, highlighting the need for improved surveillance and vaccination coverage in human and captive endangered non-human primates.
    Keywords:  Atlantic Forest; Culicidae; diversity; primary vectors; richness; yellow fever
    DOI:  https://doi.org/10.3390/tropicalmed7120410
  11. Insects. 2022 Nov 23. pii: 1079. [Epub ahead of print]13(12):
    Invasion Pattern of Aedes aegypti in the Native Range of Ae. albopictus in Vietnam Revealed by Biogeographic and Population Genetic Analysis.
    Cuong Van Duong, Ji Hyoun Kang, Van Vinh Nguyen, Yeon Jae Bae.
      Since its introduction to Asia, Aedes aegypti has coexisted with the native species Ae. albopictus and has been reported to transmit several infectious diseases. However, the development of efficient disease prevention and vector control is hindered by the relatively poor understanding of the biogeography and the genetic diversity of Ae. aegypti in the region. This study aimed to determine the invasion patterns of Ae. aegypti by evaluating the distribution and abundance of Ae. aegypti and Ae. albopictus in different climatic regions (northern temperate and southern tropical regions) and habitats (domestic, peri-domestic, and natural). We further analyzed the genetic diversity and phylogenetic relationships of Ae. aegypti populations in Vietnam using mitochondrial COI gene sequences. Both Aedes species were observed at most of the study sites, but only Ae. albopictus thrived in northern mountainous areas. In sympatric ranges, the individual abundance of the species was influenced by regional climate and habitats. The tropical climate and availability of domestic containers facilitated the dominance of Ae. aegypti, whereas temperate climates and natural breeding sites facilitated that of Ae. albopictus. In addition, many genetic polymorphisms were detected in the Ae. aegypti populations, which formed two distinct genetic groups; however, this genetic diversity is unlikely to be relevant to the invasive success of Ae. aegypti. These findings provide insights into the mechanisms and patterns of Ae. Aegypti invasion, which depend on the climate and reproductive strategies in the native range of Ae. albopictus in Asia.
    Keywords:  Aedes aegypti; Aedes albopictus; biogeography; genetic diversity; invasion
    DOI:  https://doi.org/10.3390/insects13121079
  12. Sci Adv. 2022 Dec 21. 8(51): eabq7345
    Discovery of super-insecticide-resistant dengue mosquitoes in Asia: Threats of concomitant knockdown resistance mutations.
    Shinji Kasai, Kentaro Itokawa, Nozomi Uemura, Aki Takaoka, Shogo Furutani, Yoshihide Maekawa, Daisuke Kobayashi, Nozomi Imanishi-Kobayashi, Michael Amoa-Bosompem, Katsunori Murota, Yukiko Higa, Hitoshi Kawada, Noboru Minakawa, Tran Chi Cuong, Nguyen Thi Yen, Tran Vu Phong, Sath Keo, Kroesna Kang, Kozue Miura, Lee Ching Ng, Hwa-Jen Teng, Samuel Dadzie, Sri Subekti, Kris Cahyo Mulyatno, Kyoko Sawabe, Takashi Tomita, Osamu Komagata.
      Aedes aegypti (Linnaeus, 1762) is the main mosquito vector for dengue and other arboviral infectious diseases. Control of this important vector highly relies on the use of insecticides, especially pyrethroids. The high frequency (>78%) of the L982W substitution was detected at the target site of the pyrethroid insecticide, the voltage-gated sodium channel (Vgsc) of A. aegypti collected from Vietnam and Cambodia. Alleles having concomitant mutations L982W + F1534C and V1016G + F1534C were also confirmed in both countries, and their frequency was high (>90%) in Phnom Penh, Cambodia. Strains having these alleles exhibited substantially higher levels of pyrethroid resistance than any other field population ever reported. The L982W substitution has never been detected in any country of the Indochina Peninsula except Vietnam and Cambodia, but it may be spreading to other areas of Asia, which can cause an unprecedentedly serious threat to the control of dengue fever as well as other Aedes-borne infectious diseases.
    DOI:  https://doi.org/10.1126/sciadv.abq7345
  13. R Soc Open Sci. 2022 Dec;9(12): 220967
    Is Asian tiger mosquito (Aedes albopictus) going to become homodynamic in Southern Europe in the next decades due to climate change?
    Irene Del Lesto, Claudio De Liberato, Riccardo Casini, Adele Magliano, Arianna Ermenegildi, Federico Romiti.
      The Asian tiger mosquito, Aedes albopictus, competent vector of several arboviruses, poses significant impact on human health worldwide. Although global warming is a driver of A . albopictus range expansion, few studies focused on its effects on homodynamicity (i.e. the ability to breed all-year-round), a key factor of vectorial capacity and a primary condition for an Aedes-borne disease to become endemic in temperate areas. Data from a 4-year monitoring network set in Central Italy and records from weather stations were used to assess winter adult activity and weekly minimum temperatures. Winter oviposition occurred in 38 localities with a seasonal mean photoperiod of 9.7 : 14.3 (L : D) h. Positive collections (87) occurred with an average minimum temperature of the two and three weeks before sampling of approximately 4°C. According to these evidences and considering the climate projections of three global climate models and three shared socio-economic pathways for the next three 20-year periods (from 2021 to 2080), the minimum temperature of January will increase enough to allow an all-year-round oviposition of A . albopictus in several areas of the Mediterranean Basin. Due to vector homodynamicity, Aedes-borne diseases could become endemic in Southern Europe by the end of the twenty-first century, worsening the burden on human health.
    Keywords:  Culicidae; climate change; disease vector; global warming; invasive mosquito; risk map
    DOI:  https://doi.org/10.1098/rsos.220967
  14. Viruses. 2022 Dec 06. pii: 2720. [Epub ahead of print]14(12):
    Re-Introduction of West Nile Virus Lineage 1 in Senegal from Europe and Subsequent Circulation in Human and Mosquito Populations between 2012 and 2021.
    Marie Henriette Dior Ndione, El Hadji Ndiaye, Martin Faye, Moussa Moïse Diagne, Diawo Diallo, Amadou Diallo, Amadou Alpha Sall, Cheikh Loucoubar, Oumar Faye, Mawlouth Diallo, Ousmane Faye, Mamadou Aliou Barry, Gamou Fall.
      West Nile virus (WNV) is a virus of the Japanese encephalitis antigenic complex and belongs to the family Flaviviridae of the genus flavivirus. The virus can cause infection in humans which in most cases is asymptomatic, however symptomatic cases exist and the disease can be severe causing encephalitis and meningoencephalitis. The virus is maintained in an enzootic cycle involving mosquitoes and birds, humans and other mammals such as horses can be accidental hosts. A mosquito-based arbovirus surveillance system and the sentinel syndromic surveillance network (4S) have been in place since 1988 and 2015 respectively, to better understand the transmission dynamics of arboviruses including WNV in Senegal. Arthropod and human samples have been collected from the field and analysed at Institut Pasteur de Dakar using different methods including RT-PCR, ELISA, plaque reduction neutralization test and viral isolation. RT-PCR positive samples have been analysed by Next Generation Sequencing. From 2012 to 2021, 7912 samples have been analysed and WNV positive cases have been detected, 20 human cases (19 IgM and 1 RT-PCR positive cases) and 41 mosquito pools. Phylogenetic analyzes of the sequences of complete genomes obtained showed the circulation of lineage 1a, with all these recent strains from Senegal identical to each other and very close to strains isolated from horse in France in 2015, Italy and Spain. Our data showed lineage 1a endemicity in Senegal as previously described, with circulation of WNV in humans and mosquitoes. Phylogenetic analyzes carried out with the genome sequences obtained also revealed exchanges of WNV strains between Europe and Senegal which could be possible via migratory birds. The surveillance systems that have enabled the detection of WNV in humans and arthropods should be extended to animals in a one-health approach to better prepare for global health threats.
    Keywords:  4S network; Senegal; West Nile virus; arbovirus; human population; lineage 1; mosquito population; mosquito-based surveillance; phylogenetic analysis
    DOI:  https://doi.org/10.3390/v14122720
  15. One Health. 2022 Dec;15 100462
    Modelling the West Nile virus force of infection in the European human population.
    Giovanni Marini, Andrea Pugliese, William Wint, Neil S Alexander, Annapaola Rizzoli, Roberto Rosà.
      West Nile virus (WNV) is among the most recent emerging mosquito-borne pathogens in Europe where each year hundreds of human cases are recorded. We developed a relatively simple technique to model the WNV force of infection (FOI) in the human population to assess its dependence on environmental and human demographic factors. To this aim, we collated WNV human case-based data reported to the European Surveillance System from 15 European Countries during the period 2010-2021. We modelled the regional WNV FOI for each year through normal distributions and calibrated the constituent parameters, namely average (peak timing), variance and overall intensity, to observed cases. Finally, we investigated through regression models how these parameters are associated to a set of climatic, environmental and human demographic covariates. Our modelling approach shows good agreement between expected and observed epidemiological curves. We found that FOI magnitude is positively associated with spring temperature and larger in more anthropogenic semi-natural areas, while FOI peak timing is negatively related to summer temperature. Unsurprisingly, FOI is estimated to be greater in regions with a larger fraction of elderly people, who are more likely to contract severe infections. Our results confirm that temperature plays a key role in shaping WNV transmission in Europe and provide some interesting hints on how human presence and demography might affect WNV burden. This simple yet reliable approach could be easily adopted for early warning and to address epidemiological investigations of other vector-borne diseases, especially where eco-epidemiological data are scarce.
    Keywords:  Mathematical model; Mosquito; Public health; Vector-borne disease
    DOI:  https://doi.org/10.1016/j.onehlt.2022.100462
  16. Am J Trop Med Hyg. 2022 Dec 19. pii: tpmd220417. [Epub ahead of print]
    Anopheles albimanus is a Potential Alphavirus Vector in the Americas.
    Gerard Terradas, Mario Novelo, Hillery Metz, Marco Brustolin, Jason L Rasgon.
      Despite its ecological flexibility and geographical co-occurrence with human pathogens, little is known about the ability of Anopheles albimanus to transmit arboviruses. To address this gap, we challenged An. albimanus females with four alphaviruses and one flavivirus and monitored the progression of infections. We found this species is an efficient vector of the alphaviruses Mayaro virus, O'nyong-nyong virus, and Sindbis virus, although the latter two do not currently exist in its habitat range. An. albimanus was able to become infected with Chikungunya virus, but virus dissemination was rare (indicating the presence of a midgut escape barrier), and no mosquito transmitted. Mayaro virus rapidly established disseminated infections in An. albimanus females and was detected in the saliva of a substantial proportion of infected mosquitoes. Consistent with previous work in other anophelines, we find that An. albimanus is refractory to infection with flaviviruses, a phenotype that did not depend on midgut-specific barriers. Our work demonstrates that An. albimanus may be a vector of neglected emerging human pathogens and adds to recent evidence that anophelines are competent vectors for diverse arboviruses.
    DOI:  https://doi.org/10.4269/ajtmh.22-0417
  17. Trop Med Infect Dis. 2022 Nov 22. pii: 393. [Epub ahead of print]7(12):
    Estimating the Distribution of Japanese Encephalitis Vectors in Australia Using Ecological Niche Modelling.
    Morgan Furlong, Andrew Adamu, Roslyn I Hickson, Paul Horwood, Maryam Golchin, Andrew Hoskins, Tanya Russell.
      Recent Japanese encephalitis virus (JEV) outbreaks in southeastern Australia have sparked interest into epidemiological factors surrounding the virus' novel emergence in this region. Here, the geographic distribution of mosquito species known to be competent JEV vectors in the country was estimated by combining known mosquito occurrences and ecological drivers of distribution to reveal insights into communities at highest risk of infectious disease transmission. Species distribution models predicted that Culex annulirostris and Culex sitiens presence was mostly likely along Australia's eastern and northern coastline, while Culex quinquefasciatus presence was estimated to be most likely near inland regions of southern Australia as well as coastal regions of Western Australia. While Culex annulirostris is considered the dominant JEV vector in Australia, our ecological niche models emphasise the need for further entomological surveillance and JEV research within Australia.
    Keywords:  Australia; Culex; Culex annulirostris; Culex quinquefasciatus; Culex sitiens; Japanese encephalitis virus; arbovirus; ecological niche modelling; species distribution modelling
    DOI:  https://doi.org/10.3390/tropicalmed7120393
  18. PLoS Negl Trop Dis. 2022 Dec 19. 16(12): e0010966
    Epidemiology and costs of dengue in Thailand: A systematic literature review.
    Usa Thisyakorn, Surasak Saokaew, Elaine Gallagher, Randee Kastner, Rosarin Sruamsiri, Louisa Oliver, Riona Hanley.
      BACKGROUND: Dengue is the fastest-spreading vector-borne viral disease worldwide. In Thailand, dengue is endemic and is associated with a high socioeconomic burden. A systematic literature review was conducted to assess and describe the epidemiological and economic burden of dengue in Thailand.METHODS: Epidemiological and economic studies published in English and Thai between 2011-2019 and 2009-2019, respectively, were searched in MEDLINE, Embase, and Evidence-Based Medicines reviews databases. Reports published by the National Ministry of Public Health (MoPH) and other grey literature sources were also reviewed. Identified studies were screened according to predefined inclusion and exclusion criteria. Extracted data were descriptively summarised and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.
    RESULTS: A total of 155 publications were included in the review (39 journal articles and 116 grey literature). Overall, dengue incidence varied yearly, with the highest rates per 100,000 population in 2013 (dengue fever (DF) 136.6, dengue haemorrhagic fever (DHF) 100.9, dengue shock syndrome (DSS) 3.58) and 2015 (DF 133.1, DHF 87.4, DSS 2.14). Peak incidence coincided with the monsoon season, and annual mortality was highest for DSS, particularly in the age group 15-24-year-olds. The highest dengue incidence rates were reported in children (10-14-year-olds) and young adults (15-24-year-olds), irrespective of dengue case definition. Economic and societal burdens are extensive, with the average cost per case ranging from USD 41 to USD 261, total cost per year estimated at USD 440.3 million, and an average of 7.6 workdays lost for DHF and 6.6 days for DF.
    CONCLUSIONS: The epidemiological, economic, and societal burden of dengue in Thailand is high and underreported due to gaps in national surveillance data. The use of expansion factors (EFs) is recommended to understand the true incidence of dengue and cost-benefit of control measures. Furthermore, as dengue is often self-managed and underreported, lost school and workdays result in substantial underestimation of the true economic and societal burden of dengue. The implementation of integrated strategies, including vaccination, is critical to reduce the disease burden and may help alleviate health disparities and equity challenges posed by dengue.
    DOI:  https://doi.org/10.1371/journal.pntd.0010966
  19. Travel Med Infect Dis. 2022 Dec 19. pii: S1477-8939(22)00275-7. [Epub ahead of print] 102529
    An African West Nile virus risk map for travellers and clinicians.
    José-María García-Carrasco, Antonio-Román Muñoz, Jesús Olivero, Marina Segura, Raimundo Real.
      International travellers are exposed to pathogens not commonly found in their countries of residence, including West Nile virus (WNV). Due to the difficulty of its diagnosis, little is known about its distribution in Africa. Understanding the geographic extent of risk of WNV infections is a necessity for both travellers and clinicians who advise and treat them, since there is no human vaccine. To date, there is no risk map for WNV infections in humans in Africa. Having a high-resolution risk map for the virus could be of relevance before the trip, to take preventive measures, and after the trip, for appropriate diagnosis of the disease. Virus detection in humans along the African continent were collected from official reports, and published scientific research for the period 1940 to 2020, and then geo-referenced in order to use biogeographical modelling for WNV. Models were based on fuzzy logic and machine learning algorithms and were designed to identify the environmental drivers that explain the distribution of human cases and to locate favourable areas for infections. We elaborated a high-resolution risk map for WNV infections that highlights favourable areas for infections in Africa. Although WNV infections are widely spread across Africa, the risk of the disease is not homogenously distributed. Popular tourist destinations such as Morocco, Tunisia, and South Africa, are high-risk areas for WNV infection.
    Keywords:  Clinical guidance; Epidemiology; Prevention; Tourism; Zoonosis
    DOI:  https://doi.org/10.1016/j.tmaid.2022.102529
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