bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022‒06‒26
eighteen papers selected by
Richard Halfpenny
Staffordshire University
  1. Review of the ecology and behaviour of Aedes aegypti and Aedes albopictus in Western Africa and implications for vector control.
  2. Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil.
  3. Intensity of insecticide resistance in the major malaria vector Anopheles funestus from Chikwawa, rural Southern Malawi.
  4. Assessment of malaria transmission intensity and insecticide resistance mechanisms in three rural areas of the Moyen Ogooué Province of Gabon.
  5. Differential Hatching, Development, Oviposition, and Longevity Patterns among Colombian Aedes aegypti Populations.
  6. Vector competence of Anopheles quadrimaculatus and Aedes albopictus for genetically distinct Jamestown Canyon virus strains circulating in the Northeast United States.
  7. The Potential Vector Competence and Overwintering of West Nile Virus in Vector Aedes Albopictus in China.
  8. Efficacy of a spatial repellent for control of Aedes-borne virus transmission: A cluster-randomized trial in Iquitos, Peru.
  9. Systematic Review on Diversity and Distribution of Anopheles Species in Gabon: A Fresh Look at the Potential Malaria Vectors and Perspectives.
  10. The Emergence of Japanese Encephalitis Virus in Australia in 2022: Existing Knowledge of Mosquito Vectors.
  11. Robust network stability of mosquitoes and human pathogens of medical importance.
  12. A Follow-Up to the Geographical Distribution of Anopheles Species in Malaria-Endemic and Non-Endemic Areas of Honduras.
  13. Survey of United States Mosquito Control Programs Reveals Opportunities to Improve the Operational Value of Centers for Disease Control and Prevention Bottle Bioassays.
  14. High pyrethroid-resistance intensity in Culex quinquefasciatus (Say) (Diptera: Culicidae) populations from Jigawa, North-West, Nigeria.
  15. Implementation and acceptance of government-sponsored malaria control interventions in Meghalaya, India.
  16. One Health surveillance of West Nile and Usutu viruses: a repeated cross-sectional study exploring seroprevalence and endemicity in Southern France, 2016 to 2020.
  17. Climate factors and dengue fever in Burkina Faso from 2017 to 2019.
  18. Cost and cost effectiveness of reactive case detection (RACD), reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) to reduce malaria in the low endemic setting of Namibia: an analysis alongside a 2×2 factorial design cluster randomised controlled trial.
  1. Curr Res Parasitol Vector Borne Dis. 2022 ;2 100074
    Review of the ecology and behaviour of Aedes aegypti and Aedes albopictus in Western Africa and implications for vector control.
    Beatrice R Egid, Mamadou Coulibaly, Samuel Kweku Dadzie, Basile Kamgang, Philip J McCall, Luigi Sedda, Kobie Hyacinthe Toe, Anne L Wilson.
      Western Africa is vulnerable to arboviral disease transmission, having recently experienced major outbreaks of chikungunya, dengue, yellow fever and Zika. However, there have been relatively few studies on the natural history of the two major human arbovirus vectors in this region, Aedes aegypti and Ae. albopictus, potentially limiting the implementation of effective vector control. We systematically searched for and reviewed relevant studies on the behaviour and ecology of Ae. aegypti and Ae. albopictus in Western Africa, published over the last 40 years. We identified 73 relevant studies, over half of which were conducted in Nigeria, Senegal, or Côte d'Ivoire. Most studies investigated the ecology of Ae. aegypti and Ae. albopictus, exploring the impact of seasonality and land cover on mosquito populations and identifying aquatic habitats. This review highlights the adaptation of Ae. albopictus to urban environments and its invasive potential, and the year-round maintenance of Ae. aegypti populations in water storage containers. However, important gaps were identified in the literature on the behaviour of both species, particularly Ae. albopictus. In Western Africa, Ae. aegypti and Ae. albopictus appear to be mainly anthropophilic and to bite predominantly during the day, but further research is needed to confirm this to inform planning of effective vector control strategies. We discuss the public health implications of these findings and comment on the suitability of existing and novel options for control in Western Africa.
    Keywords:  Aedes aegypti; Aedes albopictus; Behaviour; Ecology; Insecticide resistance; Vector control; Western Africa
    DOI:  https://doi.org/10.1016/j.crpvbd.2021.100074
  2. Trop Med Infect Dis. 2022 Jun 08. pii: 94. [Epub ahead of print]7(6):
    Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil.
    Shayenne Olsson Freitas Silva, Cecilia Ferreira de Mello, Sergio Lisboa Machado, Paulo José Leite, Jeronimo Alencar.
      The yellow fever (YF) virus has been detected throughout Brazil, with the occurrence of human cases, cyclic epizootics, and its isolation from Haemagogus janthinomys and Hg. leucocelaenus. We assessed the seasonal occurrence, egg abundancy, and oviposition interaction of mosquito vector species captured at a Private Natural Heritage Reserve in the Atlantic Forest biome. A total of 2943 eggs and 1538 mosquito larvae were collected from which 1231 belonged to entomologically important species. Ovitraps were used to collect immature mosquitoes from September 2019 to January 2021. The Mann-Whitney test was used to assess the differences in the abundance of eggs between rainy and dry seasons. Kruskal-Wallis and Dunn's post hoc tests were used to evaluate the significance of the differences in the number of individuals from vector species. The highest percentage of mosquito vector eggs were collected during the rainy season, from December to February. Most eggs recovered from ovitraps belonged to the species Hg. leucocelaenus, representing 85% of all mosquito eggs identified. The other species had lower abundances and percentages: Aedes terrens (7%), Haemagogus janthinomys (5%) and Aedes albopictus (3%). The species that shared breeding sites with a higher frequency were Hg. leucocelaenus and Hg. janthinomys, with a statistically positive correlation (ρ = 0.74). This finding suggests that maybe the presence of Hg. leucocelaenus eggs acted as an attractant for Hg. janthinomys or vice versa. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control approaches directed against specific pathogen vectors of medical and veterinary importance.
    Keywords:  mosquito vectors; oviposition; seasonality; surveillance; yellow fever
    DOI:  https://doi.org/10.3390/tropicalmed7060094
  3. Parasit Vectors. 2022 Jun 21. 15(1): 220
    Intensity of insecticide resistance in the major malaria vector Anopheles funestus from Chikwawa, rural Southern Malawi.
    Justin Kumala, Lizette L Koekemoer, Maureen Coetzee, Themba Mzilahowa.
      BACKGROUND: Malaria vector control using insecticide-based approaches has proven to be an effective strategy. However, widespread insecticide resistance among malaria vector populations across sub-Saharan Africa threatens to derail control efforts. This study was conducted in Chikwawa district, an area in rural southern Malawi characterised by persistent malaria transmission and reports of insecticide resistance in the local mosquito population. The aim of the was to characterise the intensity of insecticide resistance within a population of Anopheles funestus sensu lato (s.l.), a major vector of malaria in this district.METHODS: Live adult females belonging to the An. funestus group were collected from households by indoor aspiration. The CDC bottle assay was used for phenotypic quantification of resistance to deltamethrin, permethrin and alpha-cypermethrin at 1×, 2.5×, 5× and 10× the recommended diagnostic dose for each of these insecticides. WHO tube assays were used to determine susceptibility to bendiocarb, dichlorodiphenyltrichloroethane (DDT) and pirimiphos-methyl insecticides at diagnostic concentrations.
    RESULTS: Anopheles funestus s.l. exposed to 10× the recommended diagnostic dose was highly resistant to alpha-cypermethrin (mortality 95.4%); in contrast, mortality was 100% when exposed to both deltamethrin and permethrin at the same dose. Despite showing susceptibility to deltamethrin and permethrin at the 10× concentration, mortality at the 5× concentration was 96.7% and 97.1%, respectively, indicating moderate resistance to these two insecticides. WHO susceptibility assays indicated strong resistance against bendiocarb (mortality 33.8%, n = 93), whereas there was full susceptibility to DDT (mortality 98.9%, n = 103) and pirimiphos-methyl (mortality 100%, n = 103).
    CONCLUSIONS: Strategies for managing resistance to insecticides, particularly against pyrethroids, must be urgently implemented to maintain the effectiveness of insecticide-based vector control interventions in the area. Such strategies include the wide-scale introduction of third-generation synergist insecticide-treated bed nets (ITNs) and next-generation dual active ingredient ITNs. The use of effective non-pyrethroids, such as pirimiphos-methyl, clothianidin and potentially DDT, could provide a window of opportunity for indoor residual spraying across the district. This strategy would support the current Malawi Insecticide Resistance Management Plan which aims at rotating insecticides to minimise selection pressure and slow down the evolution of resistance to approved insecticides. These actions will help to prevent malaria vector control failure and improve progress towards malaria elimination.
    Keywords:  Bioassay; Indoor residual spraying; Insecticide-treated nets; Malaria transmission; Pyrethroids; Sub-Saharan Africa; Susceptibility test; Vector control
    DOI:  https://doi.org/10.1186/s13071-022-05299-3
  4. Parasit Vectors. 2022 Jun 20. 15(1): 217
    Assessment of malaria transmission intensity and insecticide resistance mechanisms in three rural areas of the Moyen Ogooué Province of Gabon.
    Stravensky Térence Boussougou-Sambe, Tamirat Gebru Woldearegai, Ange Gatien Doumba-Ndalembouly, Barclaye Ngossanga, Romuald Beh Mba, Jean Ronald Edoa, Jeannot Fréjus Zinsou, Yabo Josiane Honkpehedji, Ulysse Ateba Ngoa, Jean Claude Dejon-Agobé, Steffen Borrmann, Peter G Kremsner, Benjamin Mordmüller, Ayôla A Adegnika.
      BACKGROUND: Vector control is considered to be the most successful component of malaria prevention programs and a major contributor to the reduction of malaria incidence over the last two decades. However, the success of this strategy is threatened by the development of resistance to insecticides and behavioural adaptations of vectors. The aim of this study was to monitor malaria transmission and the distribution of insecticide resistance genes in Anopheles populations from three rural areas of the Moyen Ogooué Province of Gabon.METHODS: Anopheles spp. were collected using human landing catches in Bindo, Nombakélé and Zilé, three villages located in the surroundings of Lambaréné, during both the rainy and dry seasons. Mosquitoes were identified morphologically, and DNA was extracted from heads and thoraces. Members of the Anopheles gambiae complex were identified by molecular methods using the PCR SINE200 protocol and by sequencing of the internal transcribed spacer 2 region. Taqman assays were used to determine Plasmodium infection and the presence of resistance alleles.
    RESULTS: Anopheles gambiae sensu lato (97.7%), An. moucheti (1.7%) and An. coustani (0.6%) were the three groups of species collected. Anopheles gambiae sensu stricto (98.5%) and An. coluzzii (1.5%) were the only species of the An. gambiae complex present in the collection. Of the 1235 Anopheles collected, 1193 were collected during the rainy season; these exhibited an exophagic behaviour, and consistently more mosquitoes were collected outdoor than indoor in the three study areas. Of the 1166 Anopheles screened, 26 (2.2%) were infected with Plasmodium species, specifically Plasmodium falciparum (66.7%), P. malariae (15.4%), P. ovale curtisi (11.5%) and P. ovale wallikeri (3.8%). Malaria transmission intensity was high in Zilé, with an average annual entomological inoculation rate (aEIR) of 243 infective bites per year, while aEIRs in Bindo and Nombakélé were 80.2 and 17 infective bites per year, respectively. Both the L1014F and L1014S mutations were present at frequencies > 95% but no Ace1G119S mutation was found.
    CONCLUSION: Our results demonstrate that malaria transmission intensity is heterogeneous in these three rural areas of Moyen Ogooué Province, with areas of high transmission, such as Zilé. The exophagic behaviour of the mosquitoes as well as the high frequency of resistance mutations are serious challenges that need to be addressed by the deployment of control measures adapted to the local setting.
    Keywords:  Anopheles gambiae complex; Entomological inoculation rate; Gabon; Moyen Ogooué Province; Plasmodium species
    DOI:  https://doi.org/10.1186/s13071-022-05320-9
  5. Insects. 2022 Jun 10. pii: 536. [Epub ahead of print]13(6):
    Differential Hatching, Development, Oviposition, and Longevity Patterns among Colombian Aedes aegypti Populations.
    Andrea Arévalo-Cortés, Yurany Granada, David Torres, Omar Triana-Chavez.
      Dengue, Zika, and chikungunya are arboviral diseases for which there are no effective therapies or vaccines. The only way to avoid their transmission is by controlling the vector Aedes aegypti, but insecticide resistance limits this strategy. To generate relevant information for surveillance and control mechanisms, we determined life cycle parameters, including longevity, fecundity, and mortality, of Colombian Ae. aegypti populations from four different geographical regions: Neiva, Bello, Itagüí, and Riohacha. When reared at 28 °C, Bello had the shortest development time, and Riohacha had the longest. Each mosquito population had its own characteristic fecundity pattern during four gonotrophic cycles. The survival curves of each population were significantly different, with Riohacha having the longest survival in both males and females and Bello the shortest. High mortality was observed in mosquitoes from Neiva in the egg stage and for Bello in the pupae stage. Finally, when mosquitoes from Neiva and Bello were reared at 35 °C, development times and mortality were severely affected. In conclusion, each population has a unique development pattern with an innate trace in their biological characteristics that confers vulnerability in specific stages of development.
    Keywords:  Aedes aegypti; development time; fecundity; hatching; longevity; mortality; survivorship curve
    DOI:  https://doi.org/10.3390/insects13060536
  6. Parasit Vectors. 2022 Jun 23. 15(1): 226
    Vector competence of Anopheles quadrimaculatus and Aedes albopictus for genetically distinct Jamestown Canyon virus strains circulating in the Northeast United States.
    Constentin Dieme, Laura D Kramer, Alexander T Ciota.
      BACKGROUND: Jamestown Canyon virus (JCV; Peribunyaviridae, Orthobunyavirus) is a mosquito-borne pathogen belonging to the California serogroup. The virus is endemic in North America and increasingly recognized as a public health concern. In this study, we determined the vector competence of Anopheles (An.) quadrimaculatus and Aedes (Ae.) albopictus for five JCV strains belonging to the two lineages circulating in the Northeast.METHODS: An. quadrimaculatus and Ae. albopictus were fed blood meals containing two lineage A strains and three lineage B strains. Vector competence of both mosquito species was evaluated at 7- and 14-days post-feeding (dpf) by testing for virus presence in bodies, legs, and saliva.
    RESULTS: Our results demonstrated that Ae. albopictus mosquitoes are a competent vector for both lineages, with similar transmission levels for all strains tested. Variable levels of infection (46-83%) and dissemination (17-38%) were measured in An. quadrimaculatus, yet no transmission was detected for the five JCV strains evaluated.
    CONCLUSIONS: Our results demonstrate that establishment of Ae. albopictus in the Northeast could increase the risk of JCV but suggest An. quadrimaculatus are not a competent vector for JCV.
    Keywords:  Aedes albopictus; Anopheles quadrimaculatus; Jamestown Canyon virus; Vector competence
    DOI:  https://doi.org/10.1186/s13071-022-05342-3
  7. Front Microbiol. 2022 ;13 888751
    The Potential Vector Competence and Overwintering of West Nile Virus in Vector Aedes Albopictus in China.
    Ying-Mei Zhang, Xiao-Xia Guo, Shu-Fang Jiang, Chun-Xiao Li, Dan Xing, Heng-Duan Zhang, Yan-de Dong, Tong-Yan Zhao.
      West Nile virus (WNV) is an arbovirus, which causes widespread zoonotic disease globally. In China, it was first isolated in Jiashi County, Kashgar Region, Xinjiang in 2011. Determining the vector competence of WNV infection has important implications for the control of disease outbreaks. Four geographical strains of Aedes Albopictus (Ae. Albopictus) in China were allowed to feed on artificial infectious blood meal with WNV to determine the infection and transmission rate. The results indicated that four strains of Ae. Albopictus mosquitoes could infect and transmit WNV to 1- to 3-day-old Leghorn chickens. The infection rates of different strains were ranged from 16.7 to 60.0% and were statistically different (χ2 = 12.81, p < 0.05). The highest infection rate was obtained from the Shanghai strain (60.0%). The transmission rates of Ae. Albopictus Shanghai, Guangzhou, Beijing, and Chengdu strains were 28.6, 15.2, 13.3, and 6.7%, respectively. Furtherly, the results reveal that Ae. Albopictus Beijing strain infected orally can transmit WNV transovarially even the eggs are induced diapausing. The study confirmed that WNV could survive in the diapause eggs of Ae. Albopictus and could be transmitted to progeny after diapause termination. This is of great significance for clarifying that the WNV maintains its natural circulation in harsh environments through inter-epidemic seasons.
    Keywords:  Aedes Albopictus; West Nile virus; diapausing; infection; overwinter; transmission
    DOI:  https://doi.org/10.3389/fmicb.2022.888751
  8. Proc Natl Acad Sci U S A. 2022 Jun 28. 119(26): e2118283119
    Efficacy of a spatial repellent for control of Aedes-borne virus transmission: A cluster-randomized trial in Iquitos, Peru.
    Amy C Morrison, Robert C Reiner, William H Elson, Helvio Astete, Carolina Guevara, Clara Del Aguila, Isabel Bazan, Crystyan Siles, Patricia Barrera, Anna B Kawiecki, Christopher M Barker, Gissella M Vasquez, Karin Escobedo-Vargas, Carmen Flores-Mendoza, Alfredo A Huaman, Mariana Leguia, Maria E Silva, Sarah A Jenkins, Wesley R Campbell, Eugenio J Abente, Robert D Hontz, Valerie A Paz-Soldan, John P Grieco, Neil F Lobo, Thomas W Scott, Nicole L Achee.
      Over half the world's population is at risk for viruses transmitted by Aedes mosquitoes, such as dengue and Zika. The primary vector, Aedes aegypti, thrives in urban environments. Despite decades of effort, cases and geographic range of Aedes-borne viruses (ABVs) continue to expand. Rigorously proven vector control interventions that measure protective efficacy against ABV diseases are limited to Wolbachia in a single trial in Indonesia and do not include any chemical intervention. Spatial repellents, a new option for efficient deployment, are designed to decrease human exposure to ABVs by releasing active ingredients into the air that disrupt mosquito-human contact. A parallel, cluster-randomized controlled trial was conducted in Iquitos, Peru, to quantify the impact of a transfluthrin-based spatial repellent on human ABV infection. From 2,907 households across 26 clusters (13 per arm), 1,578 participants were assessed for seroconversion (primary endpoint) by survival analysis. Incidence of acute disease was calculated among 16,683 participants (secondary endpoint). Adult mosquito collections were conducted to compare Ae. aegypti abundance, blood-fed rate, and parity status through mixed-effect difference-in-difference analyses. The spatial repellent significantly reduced ABV infection by 34.1% (one-sided 95% CI lower limit, 6.9%; one-sided P value = 0.0236, z = 1.98). Aedes aegypti abundance and blood-fed rates were significantly reduced by 28.6 (95% CI 24.1%, ∞); z = -9.11) and 12.4% (95% CI 4.2%, ∞); z = -2.43), respectively. Our trial provides conclusive statistical evidence from an appropriately powered, preplanned cluster-randomized controlled clinical trial of the impact of a chemical intervention, in this case a spatial repellent, to reduce the risk of ABV transmission compared to a placebo.
    Keywords:  Aedes aegypti; arbovirus vector; clinical trial; spatial repellent; vector control
    DOI:  https://doi.org/10.1073/pnas.2118283119
  9. Pathogens. 2022 Jun 09. pii: 668. [Epub ahead of print]11(6):
    Systematic Review on Diversity and Distribution of Anopheles Species in Gabon: A Fresh Look at the Potential Malaria Vectors and Perspectives.
    Neil Michel Longo-Pendy, Larson Boundenga, Pyazzi Obame Ondo Kutomy, Clark Mbou-Boutambe, Boris Makanga, Nancy Moukodoum, Judicaël Obame-Nkoghe, Patrice Nzassi Makouloutou, Franck Mounioko, Rodolphe Akone-Ella, Lynda Chancelya Nkoghe-Nkoghe, Marc Flaubert Ngangue Salamba, Jean Bernard Lekana-Douki, Pierre Kengne.
      Gabon is located in the malaria hyper-endemic zone, where data concerning malaria vector distribution remains fragmentary, making it difficult to implement an effective vector control strategy. Thus, it becomes crucial and urgent to undertake entomological surveys that will allow a better mapping of the Anopheles species present in Gabon. In this review, we examined different articles dealing with Anopheles in Gabon from ProQuest, Web of Science, PubMed, and Google scholar databases. After applying the eligibility criteria to 7543 articles collected from four databases, 42 studies were included that covered a 91-year period of study. The review revealed a wide diversity of Anopheles species in Gabon with a heterogeneous distribution. Indeed, our review revealed the presence of 41 Anopheles species, of which the most abundant were members of the Gambiae and Nili complexes and those of the Funestus and Moucheti groups. However, our review also revealed that the major and minor vectors of malaria in Gabon are present in both sylvatic, rural, and urban environments. The observation of human malaria vectors in sylvatic environments raises the question of the role that the sylvatic environment may play in maintaining malaria transmission in rural and urban areas. Ultimately, it appears that knowledge of biodiversity and spatial distribution of Anopheles mosquitoes is fragmentary in Gabon, suggesting that additional studies are necessary to complete and update these entomological data, which are useful for the implementation of vector control strategies.
    Keywords:  Anopheles species; Gabon; diversity; rural; spatial distribution; sylvatic; urban
    DOI:  https://doi.org/10.3390/pathogens11060668
  10. Viruses. 2022 Jun 02. pii: 1208. [Epub ahead of print]14(6):
    The Emergence of Japanese Encephalitis Virus in Australia in 2022: Existing Knowledge of Mosquito Vectors.
    Andrew F van den Hurk, Eloise Skinner, Scott A Ritchie, John S Mackenzie.
      In early 2022, the Japanese encephalitis virus (JEV) was identified as the cause of stillborn and mummified piglets in pig farms in southeastern Australia. Human cases and additional pig farms with infected piglets were subsequently identified across a widespread area encompassing four states. To inform surveillance and control programs, we synthesized existing information on Australian vectors of JEV, much of which was generated in response to incursions of JEV into the northern state of Queensland between 1995 and 2005. Members of the Culex sitiens subgroup, particularly Culex annulirostris, should be considered the primary vectors of JEV in Australia, as they yielded &gt;87% of field detections of JEV, were highly efficient laboratory vectors of the virus, readily fed on pigs and birds (the key amplifying hosts of the virus) when they were available, and are widespread and often occur in large populations. Three introduced species, Culex quinquefasciatus, Culex gelidus and Culex tritaeniorhynchus may also serve as vectors, but more information on their geographical distribution, abundance and bionomics in the Australian context is required. Mosquitoes from other genera, such as Aedes and Verrallina, whilst considered relatively poor vectors, could play a regional or supplemental role in transmission, especially facilitating vertical transmission as a virus overwintering mechanism. Additional factors that could impact JEV transmission, including mosquito survival, dispersal and genetics, are also discussed. Possible directions for investigation are provided, especially in the context of the virus emerging in a region with different mosquito fauna and environmental drivers than northern Australia.
    Keywords:  Australia; Japanese encephalitis virus; host feeding patterns; mosquitoes; vector competence; virus detection
    DOI:  https://doi.org/10.3390/v14061208
  11. Parasit Vectors. 2022 Jun 20. 15(1): 216
    Robust network stability of mosquitoes and human pathogens of medical importance.
    Donald A Yee, Catherine Dean Bermond, Limarie J Reyes-Torres, Nicole S Fijman, Nicole A Scavo, Joseph Nelsen, Susan H Yee.
      BACKGROUND: The exact number of mosquito species relevant to human health is unknown, posing challenges in understanding the scope and breadth of vector-pathogen relationships, and how resilient mosquito vector-pathogen networks are to targeted eradication of vectors.METHODS: We performed an extensive literature survey to determine the associations between mosquito species and their associated pathogens of human medical importance. For each vector-pathogen association, we then determined the strength of the associations (i.e., natural infection, lab infection, lab dissemination, lab transmission, known vector). A network analysis was used to identify relationships among all pathogens and vectors. Finally, we examined how elimination of either random or targeted species affected the extinction of pathogens.
    RESULTS: We found that 88 of 3578 mosquito species (2.5%) are known vectors for 78 human disease-causing pathogens; however, an additional 243 species (6.8%) were identified as potential or likely vectors, bringing the total of all mosquitos implicated in human disease to 331 (9.3%). Network analysis revealed that known vectors and pathogens were compartmentalized, with the removal of six vectors being enough to break the network (i.e., cause a pathogen to have no vector). However, the presence of potential or likely vectors greatly increased redundancies in the network, requiring more than 41 vectors to be eliminated before breaking the network.
    CONCLUSION: Although < 10% of mosquitoes are involved in transmitting pathogens that cause human disease, our findings point to inherent robustness in global mosquito vector-pathogen networks.
    Keywords:  Arbovirus; Culicidae; Extinction curves; Network analysis; Pathogen; Vector
    DOI:  https://doi.org/10.1186/s13071-022-05333-4
  12. Insects. 2022 Jun 15. pii: 548. [Epub ahead of print]13(6):
    A Follow-Up to the Geographical Distribution of Anopheles Species in Malaria-Endemic and Non-Endemic Areas of Honduras.
    Denis Escobar, Osman Archaga, Allan Reyes, Adalid Palma, Ryan T Larson, Gissella M Vásquez, Gustavo Fontecha.
      Anopheles species are the vectors of malaria, one of the diseases with the greatest impact on the health of the inhabitants of the tropics. Due to their epidemiological relevance and biological complexity, monitoring of anopheline populations in current and former malaria-endemic areas is critical for malaria risk assessment. Recent efforts have described the anopheline species present in the main malaria foci in Honduras. This study updates and expands knowledge about Anopheles species composition, geographical distribution, and genetic diversity in the continental territory of Honduras as in the Bay Islands. Outdoor insect collections were carried out at 25 sites in eight municipalities in five departments of Honduras between 2018 and 2021. Specimens were identified using taxonomic keys. Partial COI gene sequences were used for molecular species identification and phylogenetic analyses. In addition, detection of Plasmodium DNA was carried out in 255 female mosquitoes. Overall, 288 Anopheles mosquitoes were collected from 8 municipalities. Eight species were morphologically identified. Anopheles albimanus was the most abundant and widely distributed species (79.5%). A subset of 175 partial COI gene sequences from 8 species was obtained. Taxonomic identifications were confirmed via sequence analysis. Anopheles albimanus and An. apicimacula showed the highest haplotype diversity and nucleotide variation, respectively. Phylogenetic clustering was found for An. argyritarsis and An. neomaculipalpus when compared with mosquitoes from other Neotropical countries. Plasmodium DNA was not detected in any of the mosquitoes tested. This report builds upon recent records of the distribution and diversity of Anopheles species in malaria-endemic and non-endemic areas of Honduras. New COI sequences are reported for three anopheline species. This is also the first report of COI sequences of An. albimanus collected on the island of Roatán with apparent gene flow relative to mainland populations.
    Keywords:  Anopheles spp.; COI gene; Honduras; genetic diversity
    DOI:  https://doi.org/10.3390/insects13060548
  13. J Med Entomol. 2022 Jun 25. pii: tjac076. [Epub ahead of print]
    Survey of United States Mosquito Control Programs Reveals Opportunities to Improve the Operational Value of Centers for Disease Control and Prevention Bottle Bioassays.
    Stephanie L Richards, Brian D Byrd, Mark Breidenbaugh, Kurt Vandock.
      Mosquito control programs have increasingly used Centers for Disease Control and Prevention bottle bioassays (BB) to evaluate insecticide resistance (IR). The reported utility, benefits, and limitations of BB and other methods were assessed via electronic survey of U.S. mosquito control professionals to identify potential areas for improvement, future study, and professional training. Opportunities were identified to improve BB operational value and IR detection.
    Keywords:  bottle bioassay; insecticide resistance; operational mosquito control
    DOI:  https://doi.org/10.1093/jme/tjac076
  14. PLoS Negl Trop Dis. 2022 Jun 21. 16(6): e0010525
    High pyrethroid-resistance intensity in Culex quinquefasciatus (Say) (Diptera: Culicidae) populations from Jigawa, North-West, Nigeria.
    Ahmed Idowu Omotayo, Musa Mustapha Dogara, Danjuma Sufi, Tasiu Shuaibu, Joshua Balogun, Salwa Dawaki, Bature Muktar, Kamoru Adeniyi, Nura Garba, Isah Namadi, Hafiz Abdullahi Adam, Shuaibu Adamu, Hamza Abdullahi, Abubakar Sulaiman, Adedayo Olatunbosun Oduola.
      This study examined pyrethroid resistance intensity and mechanisms in Culex quinquefasciatus (Say) (Diptera: Culicidae) populations from Jigawa, North-West Nigeria. Resistance statuses to permethrin, lambda-cyhalothrin and alphacypermethrin were determined with both WHO and CDC resistance bioassays. Synergist assay was conducted by pre-exposing the populations to Piperonyl butoxide (PBO) using the WHO method. Resistance intensities to 2x, 5x and 10x of diagnostic concentrations were determined with the CDC bottle method. Species analysis and presence of knockdown mutation (Leu-Phe) were done using Polymerase Chain Reaction (PCR). Results showed that Cx. quinquefasciatus was the only Culex spp. present and "Kdr-west" mutation was not detected in all analyzed samples. Using WHO method, Cx. quinquefasciatus resistance to permethrin was detected in Dutse (12.2%) and Kafin-Hausa (77.78%). Lambda-cyhalothrin resistance was recorded only in Kafin-Hausa (83.95%) with resistance suspected in Ringim (90%). Resistance to alphacypermethrin was recorded in all locations. Pre-exposure to PBO led to 100% mortality to alphacypermethrin and lambda-cyhalothrin in Ringim while mortality to permethrin and alphacypermethrin in Dutse increased from 12.2% to 97.5% and 64.37% to 79.52% respectively. Using CDC bottle bioassay, resistance was also recorded in all populations and the result shows a significant positive correlation (R2 = 0.728, p = 0.026) with the result from the WHO bioassay. Results of resistance intensity revealed a very high level of resistance in Kafin-Hausa with susceptibility to lambda-cyhalothrin and alphacypermethrin not achieved at 10x of diagnostic doses. Resistance intensity was also high in Dutse with susceptibility to all insecticides not achieved at 5x of diagnostic doses. Widespread and high intensity of resistance in Cx. quinquefasciatus from North-West Nigeria is a major threat to the control of diseases transmitted by Culex and other mosquito species. It is a challenge that needs to be adequately addressed so as to prevent the failure of pyrethroid-based vector control tools.
    DOI:  https://doi.org/10.1371/journal.pntd.0010525
  15. Malar J. 2022 Jun 23. 21(1): 200
    Implementation and acceptance of government-sponsored malaria control interventions in Meghalaya, India.
    Mattimi Passah, Carinthia Balabet Nengnong, Mark L Wilson, Jane M Carlton, Larry Kharbamon, Sandra Albert.
      BACKGROUND: India has made considerable progress in malaria reduction over the past two decades, with government-sponsored indoor residual spraying (IRS) and insecticide-treated bed net (ITN) or long-lasting insecticidal nets (LLIN) distribution being the main vector-related prevention efforts. Few investigations have used non-participant observational methods to assess malaria control measures while they were being implemented, nor documented people's perceptions and acceptance of IRS or LLINs in India, and none have done so in the northeast region. This study evaluated household (HH)-level operation of IRS and distribution of LLINs by India's National Vector Borne Disease Control Programme (NVBDCP) in 50 villages of Meghalaya state, and documented their acceptance and use.METHODS: Study field teams accompanied the government health system teams during August-October, 2019 and 2020 to observe deployment of LLINs, and record HH-level data on LLIN numbers and use. In addition, NVBDCP spray teams were followed during 2019-2021 to observe IRS preparation and administration. HH members were interviewed to better understand reasons for acceptance or refusal of spraying.
    RESULTS: A total of 8386 LLINs were distributed to 2727 HHs in 24 villages from five Primary Health Centres, representing 99.5% of planned coverage. Interviews with 80 HH residents indicated that they appreciated the LLIN dissemination programme, and generally made regular and appropriate use of LLINs, except during overnight travel or when working in agricultural fields. However, HH-level IRS application, which was observed at 632 HHs, did not always follow standard insecticide preparation and safety protocols. Of 1,079 occupied HHs visited by the spray team, 632 (58.6%) refused to allow any spraying. Only 198 (18.4%) HHs agreed to be sprayed, comprising 152 (14.1%) that were only partly sprayed, and 46 (4.3%) that were fully sprayed. Reasons for refusal included: inadequate time to rearrange HH items, young children were present, annoying smell, staining of walls, and threat to bee-keeping or Eri silk moth cultivation.
    CONCLUSIONS: These findings are among the first in India that independently evaluate people's perceptions and acceptance of ongoing government-sponsored IRS and LLIN programmes for malaria prevention. They represent important insights for achieving India's goal of malaria elimination by 2030.
    Keywords:  Implementation evaluation; Indoor residual spraying; Long-lasting insecticidal nets, risk perception; Malaria prevention; Qualitative research
    DOI:  https://doi.org/10.1186/s12936-022-04223-5
  16. Euro Surveill. 2022 Jun;27(25):
    One Health surveillance of West Nile and Usutu viruses: a repeated cross-sectional study exploring seroprevalence and endemicity in Southern France, 2016 to 2020.
    Orianne Constant, Patricia Gil, Jonathan Barthelemy, Karine Bolloré, Vincent Foulongne, Caroline Desmetz, Agnès Leblond, Isabelle Desjardins, Sophie Pradier, Aurélien Joulié, Alain Sandoz, Rayane Amaral, Michel Boisseau, Ignace Rakotoarivony, Thierry Baldet, Albane Marie, Benoît Frances, Florence Reboul Salze, Bachirou Tinto, Philippe Van de Perre, Sara Salinas, Cécile Beck, Sylvie Lecolinet, Serafin Gutierrez, Yannick Simonin.
      BackgroundWest Nile virus (WNV) and Usutu virus (USUV), two closely related flaviviruses, mainly follow an enzootic cycle involving mosquitoes and birds, but also infect humans and other mammals. Since 2010, their epidemiological situation may have shifted from irregular epidemics to endemicity in several European regions; this requires confirmation, as it could have implications for risk assessment and surveillance strategies.AimTo explore the seroprevalence in animals and humans and potential endemicity of WNV and USUV in Southern France, given a long history of WNV outbreaks and the only severe human USUV case in France in this region.MethodsWe evaluated the prevalence of WNV and USUV in a repeated cross-sectional study by serological and molecular analyses of human, dog, horse, bird and mosquito samples in the Camargue area, including the city of Montpellier, between 2016 and 2020.ResultsWe observed the active transmission of both viruses and higher USUV prevalence in humans, dogs, birds and mosquitoes, while WNV prevalence was higher in horses. In 500 human samples, 15 were positive for USUV and 6 for WNV. Genetic data showed that the same lineages, WNV lineage 1a and USUV lineage Africa 3, were found in mosquitoes in 2015, 2018 and 2020.ConclusionThese findings support existing literature suggesting endemisation in the study region and contribute to a better understanding of USUV and WNV circulation in Southern France. Our study underlines the importance of a One Health approach for the surveillance of these viruses.
    Keywords:  One Health surveillance; Usutu virus; West Nile virus; co-circulation; seroprevalence
    DOI:  https://doi.org/10.2807/1560-7917.ES.2022.27.25.2200068
  17. J Public Health Afr. 2022 May 24. 13(1): 2145
    Climate factors and dengue fever in Burkina Faso from 2017 to 2019.
    Cheick Ahmed Ouattara, Tiandiogo Isidore Traore, Seydou Traore, Ibrahim Sangare, Clément Z Meda, Léon G B Savadogo.
      Dengue is now a major health concern in sub-Saharan Africa. Understanding the influence of local meteorological factors on the incidence of dengue is an important element for better prediction and control of this disease. This study aims to assess the impact of meteorological factors on dengue transmission in the central region of Burkina Faso. We analyzed the lagged effects of meteorological factors on the weekly incidence of dengue from 2017 to 2019 in the central region of Burkina Faso using a General Additive Model. The results show that maximum and minimum temperature, relative humidity, and wind speed have a significant non-linear effect on dengue cases in the region with 83% of case variance explained. The optimal temperature that increases dengue cases was 27°C to 32°C for the maximum temperature and 18°C to 20°C for the minimum temperature with a decrease beyond that. The maximum temperature shifted by six weeks had the best correlation with dengue incidence. The estimated number of dengue cases increases as the maximum relative humidity increases from 15 to 45% and then from 60 to 70%. In general, an increase in daily wind speed is estimated to decrease the number of daily dengue cases. The relationship between rainfall and dengue cases was not significant. This study provides local information about the effect of meteorological factors on dengue that should help improve predictive models of dengue cases in Burkina Faso and contribute to the control of this disease.
    Keywords:  Dengue; Humidity; Rainfall; Temperature; Wind speed
    DOI:  https://doi.org/10.4081/jphia.2022.2145
  18. BMJ Open. 2022 Jun 23. 12(6): e049050
    Cost and cost effectiveness of reactive case detection (RACD), reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) to reduce malaria in the low endemic setting of Namibia: an analysis alongside a 2×2 factorial design cluster randomised controlled trial.
    Henry Ntuku, Cara Smith-Gueye, Valerie Scott, Joseph Njau, Brooke Whittemore, Brittany Zelman, Munyaradzi Tambo, Lisa M Prach, Lindsey Wu, Leah Schrubbe, Mi-Suk Kang Dufour, Agnes Mwilima, Petrina Uusiku, Hugh Sturrock, Adam Bennett, Jennifer Smith, Immo Kleinschmidt, Davis Mumbengegwi, Roly Gosling, Michelle Hsiang.
      OBJECTIVES: To estimate the cost and cost effectiveness of reactive case detection (RACD), reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) to reduce malaria in a low endemic setting.SETTING: The study was part of a 2×2 factorial design cluster randomised controlled trial within the catchment area of 11 primary health facilities in Zambezi, Namibia.
    PARTICIPANTS: Cost and outcome data were collected from the trial, which included 8948 community members that received interventions due to their residence within 500 m of malaria index cases.
    OUTCOME MEASURES: The primary outcome was incremental cost effectiveness ratio (ICER) per in incident case averted. ICER per prevalent case and per disability-adjusted life years (DALY) averted were secondary outcomes, as were per unit interventions costs and personnel time. Outcomes were compared as: (1) rfMDA versus RACD, (2) RAVC versus no RAVC and (3) rfMDA+RAVC versus RACD only.
    RESULTS: rfMDA cost 1.1× more than RACD, and RAVC cost 1.7× more than no RAVC. Relative to RACD only, the cost of rfMDA+RAVC was double ($3082 vs $1553 per event). The ICERs for rfMDA versus RACD, RAVC versus no RAVC and rfMDA+RAVC versus RACD only were $114, $1472 and $842, per incident case averted, respectively. Using prevalent infections and DALYs as outcomes, trends were similar. The median personnel time to implement rfMDA was 20% lower than for RACD (30 vs 38 min per person). The median personnel time for RAVC was 34 min per structure sprayed.
    CONCLUSION: Implemented alone or in combination, rfMDA and RAVC were cost effective in reducing malaria incidence and prevalence despite higher implementation costs in the intervention compared with control arms. Compared with RACD, rfMDA was time saving. Cost and time requirements for the combined intervention could be decreased by implementing rfMDA and RAVC simultaneously by a single team.
    TRIAL REGISTRATION NUMBER: NCT02610400; Post-results.
    Keywords:  EPIDEMIOLOGY; HEALTH ECONOMICS; Health policy; Public health
    DOI:  https://doi.org/10.1136/bmjopen-2021-049050
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