bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒04‒05
twenty-five papers selected by
Richard Halfpenny
Staffordshire University

  1. Viruses. 2020 Mar 26. pii: E364. [Epub ahead of print]12(4):
    Abreu FVS, Ferreira-de-Brito A, Azevedo AS, Linhares JHR, de Oliveira Santos V, Hime Miranda E, Neves MSAS, Yousfi L, Ribeiro IP, Santos AACD, Dos Santos E, Santos TPD, Teixeira DS, Gomes MQ, Fernandes CB, Silva AMVD, Lima MDRQ, Paupy C, Romano APM, Ano Bom APD, Oliveira-Pinto LM, Moutailler S, Motta MA, Castro MG, Bonaldo MC, Maria Barbosa de Lima S, Lourenço-de-Oliveira R.
      In the last decade, Flaviviruses such as yellow fever (YFV) and Zika (ZIKV) have expanded their transmission areas. These viruses originated in Africa, where they exhibit both sylvatic and interhuman transmission cycles. In Brazil, the risk of YFV urbanization has grown, with the sylvatic transmission approaching the most densely populated metropolis, while concern about ZIKV spillback to a sylvatic cycle has risen. To investigate these health threats, we carried out extensive collections and arbovirus screening of 144 free-living, non-human primates (NHPs) and 5219 mosquitoes before, during, and after ZIKV and YFV outbreaks (2015-2018) in southeast Brazil. ZIKV infection was not detected in any NHP collected at any time. In contrast, current and previous YFV infections were detected in NHPs sampled between 2017 and 2018, but not before the onset of the YFV outbreak. Mosquito pools screened by high-throughput PCR were positive for YFV when captured in the wild and during the YFV outbreak, but were negative for 94 other arboviruses, including ZIKV, regardless of the time of collection. In conclusion, there was no evidence of YFV transmission in coastal southeast Brazil before the current outbreak, nor the spread or establishment of an independent sylvatic cycle of ZIKV or urban Aedes aegypti transmission of YFV in the region. In view of the region's receptivity and vulnerability to arbovirus transmission, surveillance of NHPs and mosquitoes should be strengthened and continuous.
    Keywords:  Flavivirus; PRNT; arboviruses; high throughput real time PCR; serology
  2. Appl Environ Microbiol. 2020 Mar 27. pii: AEM.00240-20. [Epub ahead of print]
    Caragata EP, Otero LM, Carlson JS, Dizaji NB, Dimopoulos G.
      Given the continued high prevalence of mosquito-transmitted diseases there is a clear need to develop novel disease and vector control strategies. Biopesticides of microbial origin represent a promising source of new approaches to target disease transmitting mosquito populations. Here we describe the development and characterization of a novel mosquito biopesticide, derived from an air-dried, non-live preparation of the bacterium Chromobacterium sp. Panama (Family: Neisseriaceae). This preparation rapidly and effectively kills the larvae of prominent mosquito vectors, including the dengue and Zika vector Aedes aegypti, and the human malaria vector Anopheles gambiae During semi-field trials in Puerto Rico, we observed high efficacy of the biopesticide against field-derived Ae. aegypti populations, and against Ae. aegypti and Culex spp. larvae in natural breeding water, indicating the suitability of the biopesticide for use under more natural conditions. In addition to high efficacy, the non-live Csp_P biopesticide has a low effective dose, a long shelf life, high heat stability, and can be incorporated into attractive larval baits, all of which are desirable characteristics for a biopesticide.Importance We have developed a novel preparation to kill mosquitoes from an abundant soil bacterium, Chromobacterium sp. Panama. This preparation is an air-dried powder containing no live bacteria, which can be incorporated into an attractive bait and fed directly to mosquito larvae. We demonstrate that the preparation has broad spectrum activity against the larval form of the mosquitoes responsible for the transmission of malaria and the dengue, chikungunya, Yellow Fever, West Nile and Zika viruses, as well as mosquito larvae that are already resistant to commonly used mosquitocidal chemicals. Our preparation possesses many favourable traits: it kills at a low dosage, and does not lose activity when exposed to high temperatures, all of which suggest it could eventually become an effective new tool for controlling mosquitoes and the diseases they spread.
  3. Malar J. 2020 Mar 30. 19(1): 127
    Afify A, Potter CJ.
      BACKGROUND: The species-specific mode of action for DEET and many other mosquito repellents is often unclear. Confusion may arise for many reasons. First, the response of a single mosquito species is often used to represent all mosquito species. Second, behavioural studies usually test the effect of repellents on mosquito attraction towards human odorants, rather than their direct repulsive effect on mosquitoes. Third, the mosquito sensory neuron responses towards repellents are often not directly examined.METHODS: A close proximity response assay was used to test the direct repulsive effect of six mosquito repellents on Anopheles coluzzii, Aedes aegypti and Culex quinquefasciatus mosquitoes. Additionally, the behavioural assay and calcium imaging recordings of antennae were used to test the response of An. coluzzii mosquitoes towards two human odorants (1-octen-3-ol and benzaldehyde) at different concentrations, and mixtures of the repellents lemongrass oil and p-menthane-3,8-diol (PMD) with DEET.
    RESULTS: Anopheles coluzzii mosquitoes were repelled by lemongrass oil and PMD, while Ae. aegypti and Cx. quinquefasciatus mosquitoes were repelled by lemongrass oil, PMD, eugenol, and DEET. In addition, high concentrations of 1-octen-3-ol and benzaldehyde were repellent, and activated more olfactory receptor neurons on the An. coluzzii antennae than lower concentrations. Finally, changes in olfactory responses to repellent mixtures reflected changes in repulsive behaviours.
    CONCLUSIONS: The findings described here suggest that different species of mosquitoes have different behavioural responses to repellents. The data further suggest that high-odour concentrations may recruit repellent-sensing neurons, or generally excite many olfactory neurons, yielding repellent behavioural responses. Finally, DEET can decrease the neuronal and behavioural response of An. coluzzii mosquitoes towards PMD but not towards lemongrass oil. Overall, these studies can help inform mosquito repellent choice by species, guide decisions on effective repellent blends, and could ultimately identify the olfactory neurons and receptors in mosquitoes that mediate repellency.
    Keywords:  Behaviour; Calcium imaging; Human odorants; Masking; Olfaction; Olfactory neurons; Q-system; Spatial repellents
  4. Insects. 2020 Mar 22. pii: E198. [Epub ahead of print]11(3):
    Manh HD, Tuyet OT.
      Dengue is one of the most dangerous vector-borne diseases transmitted by Aedes mosquitoes. The use of mosquito repellents to protect human hosts and insecticides to reduce the mosquito population is a crucial strategy to prevent the disease. Here, we reported larvicidal and repellent activities of Mentha arvensis L. essential oil against Aedes aegypti, the main vector of the disease. The essential oil was extracted by hydro-distillation from the aromatic plant grown in Vietnam. The yield was 0.67% based on the weight of fresh leaves. The essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The main components were menthol (66.04%), menthyl acetate (22.19%), menthone (2.51%), and limonene (2.04%). Toxicity test on Aedes aegypti larvae showed that the median lethal concentrations, LC50 and LC90 were 78.1 ppm (part per million) and 125.7 ppm, respectively. Besides, the essential oil showed excellent repellency on Aedes aegypti mosquitoes. At 25%, 50%, and 100% concentration, the respective complete protection times (CPTs) were 45 min, 90 min, and 165 min. When adding 5% vanillin to the essential oil (25%), the complete protection time of the essential oil increased up to 120 min. In conclusion, the EO from Mentha arvensis L. has been shown to be a promising natural larvicide and repellent against Aedes aegypti mosquitoes.
    Keywords:  Aedes aegypti; Larvicidal activity; Mentha arvensis; essential oil; mosquito repellent
  5. Am J Trop Med Hyg. 2020 Mar 30.
    Ali R, Azmi RA, Wasi Ahmad N, Abd Hadi A, Muhamed KA, Rasli R, Cheong YL, Anak Chua H, Kiew Lian W, Lim LH.
      Two confirmed human cases of Zika virus (ZIKV) were reported in the district of Miri, Sarawak, in 2016. Following that, a mosquito-based ZIKV surveillance study was conducted within 200-m radius from the case houses. Mosquito surveillance was conducted using five different methods, that is, BG sentinel trap, modified sticky ovitrap, resting catch, larval surveillance, and conventional ovitrap. A total of 527 and 390 mosquito samples were obtained from the case houses in two localities, namely, Kampung Lopeng and Taman Shang Ri La, Miri, Sarawak, respectively. All mosquitoes collected were identified, which consisted of 11 species. Aedes albopictus, both the adult and larval stages, was the dominant species. Resting catch method obtained the highest number of adult mosquitoes (67%), whereas ovitrap showed the highest catch for larval mosquitoes (84%). Zika virus was detected in both adults and larvae of Ae. albopictus together with adults of Culex gelidus, and Culex quiquefasciatus using the real-time reverse transcriptase PCR technique. It was noteworthy that Ae. albopictus positive with ZIKV were caught and obtained from all four types of collection method. By contrast, Cx. gelidus and Culex quinquefasciatus adults collected from sticky ovitraps were also found positive with ZIKV. This study reveals vital information regarding the potential vectors of ZIKV and the possibility of transovarian transmission of the virus in Malaysia. These findings will be essentials for vector control program managers to devise preparedness and contingency plans of prevention and control of the arboviral disease.
  6. Vector Borne Zoonotic Dis. 2020 Apr 02.
    Guo X, Jang T, Jiang Y, Zhao T, Li C, Dong Y, Xing D, Qin C, Zhao T.
      A new duck Tembusu-related flavivirus, Baiyangdian virus (BYDV), caused duck egg-drop syndrome in China. The rapid spread, unknown transmission routes, and zoonotic nature, raise serious concern about BYDV as a potential threat to human health. The study provides the first evaluation on the vector competence of Culex and Aedes mosquitoes to transmit BYDV in China. The results show that Culex tritaeniorhynchus, Culex pipiens pallens, Culex pipiens quinquefasciatus, and Aedes albopictus can become infected with BYD-1 virus (BYDV-1) on different days after oral infection. Although the viral copies in Ae. albopictus was higher than that in Cx. p. quinquefasciatus at 13 days postinfection (χ2 = 10.385, p = 0.016), there was no significant differences between infection rates of four mosquito species (χ2 = 3.98, p = 0.137). In transmission experiment, healthy ducks were infected after being bitten by virus-positive mosquitoes and BYDV-1 disseminated to and replicated in the duck brains. These findings verified the potential role of Cx. p. quinquefasciatus and Cx. tritaeniorhynchus as vectors of BYDV-1. BYDV-1 was also detected in salivary gland of Cx. p. pallens, which indicated that this virus could be transmitted by mosquitoes. These results provide evidence for the role of Culex mosquitoes in the transmission cycles involving BYDV-1 and avian hosts in China.
    Keywords:  BYDV-1; Culex; vector competence
  7. Trop Med Infect Dis. 2020 Apr 01. pii: E51. [Epub ahead of print]5(2):
    Young KI, Medwid JT, Azar SR, Huff RM, Drumm H, Coffey LL, Pitts RJ, Buenemann M, Vasilakis N, Perera D, Hanley KA.
      Land cover and land use change (LCLUC) acts as a catalyst for spillover of arthropod-borne pathogens into novel hosts by shifting host and vector diversity, abundance, and distribution, ultimately reshaping host-vector interactions. Identification of bloodmeals from wild-caught mosquitoes provides insight into host utilization of particular species in particular land cover types, and hence their potential role in pathogen maintenance and spillover. Here, we collected 134 blood-engorged mosquitoes comprising 10 taxa across 9 land cover types in Sarawak, Malaysian Borneo, a region experiencing intense LCLUC and concomitant spillover of arthropod-borne pathogens. Host sources of blood were successfully identified for 116 (87%) mosquitoes using cytochrome oxidase subunit I (COI) barcoding. A diverse range of hosts were identified, including reptiles, amphibians, birds, and mammals. Sixteen engorged Aedes albopictus, a major vector of dengue virus, were collected from seven land cover types and found to feed exclusively on humans (73%) and boar (27%). Culex tritaeniohynchus (n = 2), Cx. gelidus (n = 3), and Cx. quiquefasciatus (n = 3), vectors of Japanese encephalitis virus, fed on humans and pigs in the rural built-up land cover, creating potential transmission networks between these species. Our data support the use of COI barcoding to characterize mosquito-host networks in a biodiversity hotspot.
    Keywords:  Aedes; Borneo; arbovirus; bloodmeal; dengue virus; host; land cover and land use change; mosquito; vector
  8. Parasit Vectors. 2020 Mar 30. 13(1): 156
    Surendran SN, Jayadas TTP, Tharsan A, Thiruchenthooran V, Santhirasegaram S, Sivabalakrishnan K, Raveendran S, Ramasamy R.
      BACKGROUND: Malaria was eliminated from Sri Lanka in 2013. However, the influx of infected travelers and the presence of potent anopheline vectors can re-initiate transmission in Jaffna city, which is separated by a narrow strait from the malaria-endemic Indian state of Tamil Nadu.METHODS: Anopheline larvae were collected from different habitats in Jaffna city and the susceptibility of emergent adults to DDT, malathion and deltamethrin investigated.
    RESULTS: Anopheline larvae were found in wells, surface-exposed drains, ponds, water puddles and water storage tanks, with many containing polluted, alkaline and brackish water. Anopheles culicifacies, An. subpictus, An. stephensi and An. varuna were identified in the collections. Adults of the four anopheline species were resistant to DDT. Anopheles subpictus and An. stephensi were resistant while An. culicifacies and An. varuna were possibly resistant to deltamethrin. Anopheles stephensi was resistant, An. subpictus possibly resistant while An. varuna and An. culicifacies were susceptible to malathion. DNA sequencing showed a L1014F (TTA to TTC) mutation in the IIS6 transmembrane segment of the voltage-gated sodium channel protein in deltamethrin-resistant An. subpictus-a mutation previously observed in India but not Sri Lanka.
    CONCLUSION: Anopheles subpictus in Jaffna, like An. stephensi, may have recently originated in coastal Tamil Nadu. Besides infected overseas travelers, wind- and boat-borne carriage of Plasmodium-infected anophelines across the Palk Strait can potentially reintroduce malaria transmission to Jaffna city. Adaptation to diverse larval habitats and resistance to common insecticides in anophelines are identified as potential problems for vector control should this happen.
    Keywords:  Anopheles malaria vectors; Insecticide resistance; Jaffna; Larval habitats; Malaria control; Mosquito range expansion; Sri Lanka; Tamil Nadu; Transnational mosquito migration; kdr mutation
  9. Mol Ecol. 2020 Apr 04.
    Endersby-Harshman NM, Schmidt TL, Chung J, van Rooyen A, Weeks AR, Hoffmann AA.
      Nations throughout the Indo-Pacific region use pyrethroid insecticides to control Aedes aegypti, the mosquito vector of dengue, often without knowledge of pyrethroid resistance status of the pest or origin of resistance. Two mutations (V1016G + F1534C) in the sodium channel gene (Vssc) of Ae. aegypti modify ion channel function and cause target-site resistance to pyrethroid insecticides, with a third mutation (S989P) having a potential additive effect. Of 27 possible genotypes involving these mutations, some allelic combinations are never seen while others predominate. Here, five allelic combinations common in Ae. aegypti from the Indo-Pacific region are described and their geographical distributions investigated using genome-wide SNP markers. We tested the hypothesis that resistance allele combinations evolved de novo in populations, versus the alternative that dispersal of Ae. aegypti between populations facilitated genetic invasions of allele combinations. We used latent factor mixed-models to detect SNPs throughout the genome that showed structuring in line with resistance allele combinations and compared variation at SNPs within the Vssc gene with genome-wide variation. Mixed-models detected an array of SNPs linked to resistance allele combinations, all located within or in close proximity to the Vssc gene. Variation at SNPs within the Vssc gene was structured by resistance profile, while genome-wide SNPs were structured by population. These results demonstrate that alleles near to resistance mutations have been transferred between populations via linked selection. This indicates that genetic invasions have contributed to the widespread occurrence of Vssc allele combinations in Ae. aegypti in the Indo-Pacific region, pointing to undocumented mosquito invasions between countries.
    Keywords:   Aedes aegypti ; genetic invasion; insecticide resistance; linked selection; single nucleotide polymorphism (SNP); voltage sensitive sodium channel (Vssc)
  10. PLoS One. 2020 ;15(4): e0230910
    Bohari R, Jin Hin C, Matusop A, Abdullah MR, Ney TG, Benjamin S, Lim LH.
      Several sites, Z-7L, Z-5 and Z-14, in Sibu district, Sarawak, Malaysia, experienced intense dengue transmission in 2014 that continued into 2015. A pilot study with Bacillus thuringiensis israelensis (Bti) to control Aedes aegypti (L.) and Ae. albopictus (Skuse) was evaluated in Z-7L, a densely populated site of 12 ha. Bti treatments were conducted weekly from epidemiology week (EW) 24/2015 for 4 weeks, followed by fortnight treatments for 2 months, in addition to the routine control activities. Bti was directly introduced into potable containers and the outdoor artificial and natural containers were treated via a wide area spray application method using a backpack mister. Aedes indices significantly reduced during the treatment and post treatment phases, compared to the control site, Z-5 (p<0.05). A 51 fold reduction in the incidence rate per 100,000 population (IR) was observed, with one case in 25 weeks (EW 29-52). In Z-5 and Z-14, control sites, a 6 fold reduction in the IR was observed from EW 29-52. However, almost every week there were dengue cases in Z-14 and until EW 44 in Z-5. In 2016, dengue cases resurfaced in Z-7L from EW 4. Intensive routine control activities were conducted, but the IR continued to escalate. The wide area Bti spray misting of the outdoor containers was then included from EW 27 on fortnight intervals. A 6 fold reduction in IR was observed in the Bti treatment phase (EW 32-52) with no successive weekly cases after EW 37. However, in the control sites, there were dengue cases throughout the year from EW 1-52, particularly in Z-14. We feel that the wide area Bti spray application method is an integral component in the control program, in conjunction with other control measures carried out, to suppress the vector population in outdoor cryptic containers and to interrupt the disease transmission.
  11. J Infect Dis. 2020 Apr 02. pii: jiaa157. [Epub ahead of print]
    Alkema M, Reuling IJ, de Jong GM, Lanke K, Coffeng LE, van Gemert GJ, van de Vegte-Bolmer M, de Mast Q, van Crevel R, Ivinson K, Ockenhouse CF, McCarthy JS, Sauerwein R, Collins KA, Bousema T.
      BACKGROUND: For malaria elimination efforts it is important to better understand parasite transmission to mosquitoes and develop models for early-clinical evaluation of transmission-blocking interventions.METHODS: In a randomized open-label trial, 24 participants were infected by bites from Plasmodium falciparum 3D7-infected mosquitoes (MB, n=12) or by induced blood stage malaria with the same parasite line (IBSM, n=12). Following subcurative piperaquine treatment, asexual parasite and gametocytes kinetics were assessed and mosquito feeding experiments were performed.
    RESULTS: Study procedures were well tolerated. Median peak gametocyte density was 1304 gametocytes/mL (interquartile range (IQR) 308-1607) following IBSM compared to 14 gametocytes/mL (IQR 10-64) following MB (P < 0.001), despite similar peak asexual parasite densities (P = 0.478). Peak gametocyte density correlated with preceding pfap2-g transcripts, indicative of gametocyte commitment (ρ = 0.62; P = 0.002). Direct feeding assays resulted in mosquito infections from 9/12 participants following IBSM versus 0/12 following MB (P < 0.001).
    CONCLUSIONS: We observed a striking effect of inoculation method on gametocyte production, suggesting higher gametocyte commitment following IBSM. Our direct comparison of MB and IBSM establishes the CHMI-transmission model using intravenous administration of Pf-infected erythrocytes as a model for early-clinical evaluation of interventions that aim to interrupt malaria transmission.
    Keywords:   Plasmodium falciparum ; anopheles ; controlled infection; gametocyte
  12. Salud Publica Mex. 2020 Mar-Apr;62(2):62(2): 203-210
    Sánchez-Casiano N, Cime-Castillo J, Ovilla-Muñoz M, Ramírez-Arroyo J, González-Acosta C, Moreno-García M, Correa-Morales F, Pando-Robles V.
      OBJECTIVE: To gain a better understanding of the Zika virus (ZIKV) vector transmission in Mexico, we determined the vector competence of a local population of Ae. aegypti (Acapulco, Guerrero) for a strain of ZIKV isolated from a Mexican febrile patient.MATERIALS AND METHODS: Eggs were hatched and larvae were reared under controlled conditions. After five days post-emergence, female mosquitoes were fed an infectious blood-meal containing ZIKV. Mosquitoes were analyzed at 4, 7 and 14-day post-infection (dpi). Infection (gut), dissemination (wings, legs and heads) and potential transmission (salivary glands) were assessed by RT-qPCR. The Rockefeller Ae. aegypti strain was used as ZIKV infection control.
    RESULTS: ZIKV infection, dissemination, and potential transmission rates were 96.2, 96.1 and 93.2%, respectively.
    CONCLUSIONS: Ae. aegypti (F1) from Acapulco were very susceptible to ZIKV infection, and showed similar vector competence to that of the susceptible Rockefeller strain. To our knowledge, this is the first report of vector competence for ZIKV performed in a Mexican laboratory.
    Keywords:  Aedes aegypti; Mexico; Zika virus; vector competence
  13. Parasit Vectors. 2020 Apr 01. 13(1): 161
    Nebbak A, Almeras L.
      BACKGROUND: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) biotyping is an innovative strategy, applied successfully for the identification of numerous arthropod families including mosquitoes. The effective mosquito identification using this emerging tool was demonstrated possible at different steps of their life-cycle, including eggs, immature and adult stages. Unfortunately, for species identification by MS, the euthanasia of the mosquito specimen is required.METHODS: To avoid mosquito euthanasia, the present study assessed whether aedine mosquitoes could be identified by MALDI-TOF MS biotyping, using their respective exuviae. In this way, exuviae from the fourth-instar and pupal stages of Aedes albopictus and Aedes aegypti were submitted to MALDI-TOF MS analysis.
    RESULTS: Reproducible and specific MS spectra according to aedine species and stage of exuviae were observed which were objectified by cluster analyses, composite correlation index (CCI) tool and principal components analysis (PCA). The query of our reference MS spectra database (DB) upgraded with MS spectra of exuviae from fourth-instar larvae and pupae of both Aedes species revealed that 100% of the samples were correctly classified at the species and stage levels. Among them, 93.8% (135/144) of the MS profiles reached the threshold log score value (LSV > 1.8) for reliable identification.
    CONCLUSIONS: The extension of reference MS spectra DB to exuviae from fourth-instar and pupal stages made now possible the identification of mosquitoes throughout their life-cycle at aquatic and aerial stages. The exuviae presenting the advantage to avoid specimen euthanasia, allowing to perform complementary analysis on alive mosquitoes.
    Keywords:  Aedes; Exuviae; Identification; Innovative strategy; MALDI-TOF MS
  14. Med Vet Entomol. 2020 Mar 31.
    Montenegro D, Martinez L, Tay K, Hernandez T, Noriega D, Barbosa L, Muñoz J, Mateus H, Daza J, Teherán A, Ramírez JD.
      In the past decade, new strategies have been developed to control the Aedes aegypti (Diptera: Culicidae) mosquito vector, as well as a broad range of arboviral agents. Vector control surveillance programmes in Puerto Rico and Australia have implemented the Centers for Disease Control and Prevention autocidal gravid ovitrap (AGO), which has had an impact on vector density and, consequently, the epidemiology of arboviral infections. Colombia intends to establish the AGO as a new tool for the surveillance and control of the A. aegypti vector. AGOs were evaluated in a hyperendemic area for dengue virus during an 8-week period in Villavicencio city, eastern Colombia. The results indicated that the AGOs detect a high density of A. aegypti, with positive results for these traps of over 80% and an average catch of six individuals per trap per week. Acceptance of AGOs in the community exceeded 95%, and adherence was around 89%. This study's results demonstrate, for the first time in Colombia, that traps are a useful tool for the surveillance of A. aegypti. Future studies must consider the implementation of AGOs in the region.
    Keywords:  Arboviruses; autocidal gravid ovitrap; entomology; surveillance; vector control
  15. Malar J. 2020 Mar 30. 19(1): 125
    Gosling R, Chimumbwa J, Uusiku P, Rossi S, Ntuku H, Harvard K, White C, Tatarsky A, Chandramohan D, Chen I.
      Despite huge investments and implementation of effective interventions for malaria, progress has stalled, with transmission being increasingly localized among difficult-to-reach populations and outdoor-biting vectors. Targeting difficult pockets of transmission will require the development of tailored and targeted approaches suited to local context, drawing from insights close to the frontlines. Districts are best placed to develop tailored, locally appropriate approaches. We propose a reorganization of how malaria services are delivered. Firstly, enabling district health officers to serve as conduits between technical experts in national malaria control programmes and local community leaders with knowledge specific to local, at-risk populations; secondly, empowering district health teams to make malaria control decisions. This is a radical shift that requires the national programme to cede some control. Shifting towards a district or provincial level approach will necessitate deliberate planning, and repeated, careful assessment, starting with piloting and learning through experience. Donors will need to alter current practice, allowing for flexible funding to be controlled at sub-national levels, and to mix finances between case management, vector control and surveillance, monitoring and evaluation. System-wide changes proposed are challenging but may be necessary to overcome stalled progress in malaria control and elimination and introduce targeted interventions tailored to the needs of diverse malaria affected populations.
    Keywords:  Community engagement; Control; District health management team; Elimination; High risk populations; Malaria; Policy; Residual transmission; Surveillance
  16. Parasit Vectors. 2020 Mar 30. 13(1): 160
    Ong OTW, Kho EA, Esperança PM, Freebairn C, Dowell FE, Devine GJ, Churcher TS.
      BACKGROUND: Practical, field-ready age-grading tools for mosquito vectors of disease are urgently needed because of the impact that daily survival has on vectorial capacity. Previous studies have shown that near-infrared spectroscopy (NIRS), in combination with chemometrics and predictive modeling, can forecast the age of laboratory-reared mosquitoes with moderate to high accuracy. It remains unclear whether the technique has utility for identifying shifts in the age structure of wild-caught mosquitoes. Here we investigate whether models derived from the laboratory strain of mosquitoes can be used to predict the age of mosquitoes grown from pupae collected in the field.METHODS: NIRS data from adult female Aedes albopictus mosquitoes reared in the laboratory (2, 5, 8, 12 and 15 days-old) were analysed against spectra from mosquitoes emerging from wild-caught pupae (1, 7 and 14 days-old). Different partial least squares (PLS) regression methods trained on spectra from laboratory mosquitoes were evaluated on their ability to predict the age of mosquitoes from more natural environments.
    RESULTS: Models trained on spectra from laboratory-reared material were able to predict the age of other laboratory-reared mosquitoes with moderate accuracy and successfully differentiated all day 2 and 15 mosquitoes. Models derived with laboratory mosquitoes could not differentiate between field-derived age groups, with age predictions relatively indistinguishable for day 1-14. Pre-processing of spectral data and improving the PLS regression framework to avoid overfitting can increase accuracy, but predictions of mosquitoes reared in different environments remained poor. Principal components analysis confirms substantial spectral variations between laboratory and field-derived mosquitoes despite both originating from the same island population.
    CONCLUSIONS: Models trained on laboratory mosquitoes were able to predict ages of laboratory mosquitoes with good sensitivity and specificity though they were unable to predict age of field-derived mosquitoes. This study suggests that laboratory-reared mosquitoes do not capture enough environmental variation to accurately predict the age of the same species reared under different conditions. Further research is needed to explore alternative pre-processing methods and machine learning techniques, and to understand factors that affect absorbance in mosquitoes before field application using NIRS.
    Keywords:  Age; Asian tiger mosquito; Chemometrics; Near-infrared; Spectroscopy
  17. BMC Infect Dis. 2020 Mar 26. 20(1): 252
    Romero-Alvarez D, Parikh N, Osthus D, Martinez K, Generous N, Del Valle S, Manore CA.
      BACKGROUND: Dengue fever is a mosquito-borne infection transmitted by Aedes aegypti and mainly found in tropical and subtropical regions worldwide. Since its re-introduction in 1986, Brazil has become a hotspot for dengue and has experienced yearly epidemics. As a notifiable infectious disease, Brazil uses a passive epidemiological surveillance system to collect and report cases; however, dengue burden is underestimated. Thus, Internet data streams may complement surveillance activities by providing real-time information in the face of reporting lags.METHODS: We analyzed 19 terms related to dengue using Google Health Trends (GHT), a free-Internet data-source, and compared it with weekly dengue incidence between 2011 to 2016. We correlated GHT data with dengue incidence at the national and state-level for Brazil while using the adjusted R squared statistic as primary outcome measure (0/1). We used survey data on Internet access and variables from the official census of 2010 to identify where GHT could be useful in tracking dengue dynamics. Finally, we used a standardized volatility index on dengue incidence and developed models with different variables with the same objective.
    RESULTS: From the 19 terms explored with GHT, only seven were able to consistently track dengue. From the 27 states, only 12 reported an adjusted R squared higher than 0.8; these states were distributed mainly in the Northeast, Southeast, and South of Brazil. The usefulness of GHT was explained by the logarithm of the number of Internet users in the last 3 months, the total population per state, and the standardized volatility index.
    CONCLUSIONS: The potential contribution of GHT in complementing traditional established surveillance strategies should be analyzed in the context of geographical resolutions smaller than countries. For Brazil, GHT implementation should be analyzed in a case-by-case basis. State variables including total population, Internet usage in the last 3 months, and the standardized volatility index could serve as indicators determining when GHT could complement dengue state level surveillance in other countries.
    Keywords:  Brazil; Digital epidemiology; Epidemiology; Google health trends; Internet data streams; Internet penetration; Volatility
  18. PLoS Negl Trop Dis. 2020 Apr 03. 14(4): e0008204
    Ross PA, Axford JK, Callahan AG, Richardson KM, Hoffmann AA.
      Wolbachia are being used to reduce dengue transmission by Aedes aegypti mosquitoes around the world. To date releases have mostly involved Wolbachia strains with limited fitness effects but strains with larger fitness costs could be used to suppress mosquito populations. However, such infections are expected to evolve towards decreased deleterious effects. Here we investigate potential evolutionary changes in the wMelPop infection transferred from Drosophila melanogaster to Aedes aegypti more than ten years (~120 generations) ago. We show that most deleterious effects of this infection have persisted despite strong selection to ameliorate them. The wMelPop-PGYP infection is difficult to maintain in laboratory colonies, likely due to the persistent deleterious effects coupled with occasional maternal transmission leakage. Furthermore, female mosquitoes can be scored incorrectly as infected due to transmission of Wolbachia through mating. Infection loss in colonies was not associated with evolutionary changes in the nuclear background. These findings suggest that Wolbachia transinfections with deleterious effects may have stable phenotypes which could ensure their long-term effectiveness if released in natural populations to reduce population size.
  19. Zootaxa. 2020 Mar 03. 4747(2): zootaxa.4747.2.8
    Talaga S, Gantier JC, Girod R.
      Examination of type specimens and topotypic material is often a necessary step to ascertain the validity of a species. Consequently, solid knowledge about type series, type locality and type depository is critical. In this paper, we provide a thorough review of the mosquito species originally described from specimens collected in French Guiana, with specific emphasis on the location of the current depositories of type material, the composition of type series and the delimitation of type localities. Information already published about the mosquito type material from French Guiana was gathered and efforts were made to ascertain the current location of their depositories. This investigation made it possible to locate a large part of the existing type material and to provide corrected information on type series and type localities, therefore providing a strong basis for future taxonomic research on mosquitoes. The type locality of Culex (Culex) pseudojanthinosoma Senevet Abonnenc is corrected from French Guiana to Africa, and this species is synonymized with Culex (Culex) duttoni Theobald.
    Keywords:  Diptera, holotype, lectotype, South America, type depository, type locality
  20. Epidemiol Infect. 2020 Apr 01. 148 e72
    Sherwood JA, Stehman SV, Howard JJ, Oliver J.
      From 1971 to 2012, in New York State, years with human Eastern equine encephalitis (EEE) were more strongly associated with the presence of Aedes canadensis, Coquillettidia perturbans and Culiseta melanura mosquitoes infected with the EEE virus (Fisher's exact test, one-sided P = 0.005, 0.03, 0.03) than with Culiseta morsitans, Aedes vexans, Culex pipiens-restuans, Anopheles quadrimaculatus or Anopheles punctipennis (P = 0.05, 0.40, 0.33, 1.00, 1.00). The estimated relative risk of a case in a year in which the virus was detected vs. not detected was 14.67 for Ae. canadensis, 6.38 for Cq. perturbans and 5.50 for Cs. morsitans. In all 5 years with a case, Cs. melanura with the virus was detected. In no year was there a case in the absence of Cs. melanura with the virus. There were 18 years with no case in the presence of Cs. melanura with the virus. Such observations may identify the time of increased risk, and when the methods may be used to prevent or reduce exposure to vector mosquito species in this geographic region.
    Keywords:  Aedes; Eastern equine encephalitis virus; human; mosquitoes; vector
  21. J Chem Ecol. 2020 Apr 02.
    Schoelitsz B, Mwingira V, Mboera LEG, Beijleveld H, Koenraadt CJM, Spitzen J, van Loon JJA, Takken W.
      The oviposition behavior of mosquitoes is mediated by chemical cues. In the malaria mosquito Anopheles gambiae, conspecific larvae produce infochemicals that affect this behavior. Emanations from first instar larvae proved strongly attractive to gravid females, while those from fourth instars caused oviposition deterrence, suggesting that larval developmental stage affected the oviposition choice of the female mosquito.We examined the nature of these chemicals by headspace collection of emanations of water in which larvae of different stages were developing. Four chemicals with putative effects on oviposition behavior were identified: dimethyldisulfide (DMDS) and dimethyltrisulfide (DMTS) were identified in emanations from water containing fourth instars; nonane and 2,4-pentanedione (2,4-PD) were identified in emanations from water containing both first and fourth instars. Dual-choice oviposition studies with these compounds were done in the laboratory and in semi-field experiments in Tanzania.In the laboratory, DMDS and DMTS were associated with oviposition-deterrent effects, while results with nonane and 2,4-PD were inconclusive. In further studies DMDS and DMTS evoked egg retention, while with nonane and 2,4-PD 88% and 100% of female mosquitoes, respectively, laid eggs. In dual-choice semi-field trials DMDS and DMTS caused oviposition deterrence, while nonane and 2,4-PD evoked attraction, inducing females to lay more eggs in bowls containing these compounds compared to the controls. We conclude that oviposition of An. gambiae is mediated by these four infochemicals associated with conspecific larvae, eliciting either attraction or deterrence. High levels of egg retention occurred when females were exposed to chemicals associated with fourth instar larvae.
    Keywords:  2,4-pentanedione; An. gambiae s.s.; Anopheles coluzzii; Behavior; Dimethyldisulfide; Dimethyltrisulfide; Malaria; Mosquito; Nonane; Oviposition
  22. PLoS One. 2020 ;15(4): e0230486
    Quintero J, Ronderos Pulido N, Logan J, Ant T, Bruce J, Carrasquilla G.
      Aedes aegypti transmitted arboviral diseases are of significant importance in Colombia, particularly since the 2014/2015 introduction of chikungunya and Zika in the Americas and the increasing spread of dengue. In response, the Colombian government initiated the scaling-up of a community-based intervention under inter and multi-sector partnerships in two out of four sectors in Girardot, one of the most hyper-endemic dengue cities in the country. Using a quasi-experimental research design a scaled-up community-led Aedes control intervention was assessed for its capacity to reduce dengue from January 2010 to August 2017 in Girardot, Colombia. Reported dengue cases, and associated factors were analysed from available data sets from the Colombian disease surveillance systems. We estimated the reduction in dengue cases before and after the intervention using, Propensity Score Matching and an Autoregressive Moving Average model for robustness. In addition, the differences in dengue incidence among scaling-up phases (pre-implementation vs sustainability) and between treatment groups (intervention and control areas) were modelled. Evidence was found in favour of the intervention, although to maximise impact the scaling-up of the intervention should continue until it covers the remaining sectors. It is expected that a greater impact of the intervention can be documented in the next outbreak of dengue in Girardot.
  23. Int J Radiat Biol. 2020 Mar 31. 1-19
    Sistanizadeh-Aghdam M, Abai MR, Shayeghi M, Mahvi AH, Raeisi A.
      Purpose: In southern Iran with a tropical climate, the above and underground cisterns of drinking water are the main habitats for immature stages of mosquitoes. The local people do not agree with using calcium hypochlorite granules in the water cisterns due to the change of water taste. Following the increased worldwide interest in using ultrasound technology for water disinfection, this study was conducted to assess the possible dual effects of ultrasound waves against immature mosquitoes.Materials and methods: Combinations of four power levels, two frequencies, three temperatures, and eight exposure times were applied to immature Culex pipiens. The exposure chamber of immature mosquitoes was the disposable cups placed inside a sonication bath containing tap water.Results: The mortality rate of immature mosquitos was 85-91% at 10-25 W, 30 °C and 130 kHz. The most effective ultrasound regimen for causing immature mortality included a fixed frequency of 130 kHz, a temperature of 30 °C, and a power level of 20-25 W. The lowest efficacy was observed in the egg stage. The median lethal time (LT50) and ninety percent lethal time (LT90) of sonication was 5.9 ± 0.6 min and 1.6 ± 0.1 min at 30 °C and a fixed frequency of 130 kHz.Conclusions: Evidence indicated effective ultrasound irradiation against immature mosquitoes in the water. This study provides a clear scientific basis for larvicidal properties induced by ultrasound emissions at laboratory conditions. The findings could be used for setting the ultrasound devices in the field investigations for achieving desired effectiveness.
    Keywords:  Culex pipiens; Ultrasound; immature; irradiation; larviciding effect
  24. Environ Sci Pollut Res Int. 2020 Apr 01.
    Soonwera M, Sittichok S.
      The knockdown and adulticidal activities of individual Cymbopogon citratus and Eucalyptus globulus essential oils (EOs) and their combinations were evaluated against three medical insect pests (Aedes aegypti, Aedes albopictus, and Musca domestica) using a WHO susceptibility test. The knockdown and adulticidal activities against the three medical insect pests of combinations of C. citratus and E. globulus EOs were higher than those of individual EOs alone. Combinations of 7.5% C. citratus + 7.5% E. globulus EOs and 10% C. citratus + 10% E. globulus EOs exhibited the highest efficacy against females of the three species with 100% knockdown and mortality rates at 1 and 24 h after exposure, respectively. Their adulticidal activities were equivalent to that of 10% w/v cypermethrin. In contrast, 70% v/v ethyl alcohol negative control was not effective at all. The combinations of EOs showed a synergistic effect, i.e., their adulticidal activity was improved by 0.2 to 100%, with increased knockdown and mortality rates, compared to individual EOs. The highest synergistic effect on effective knockdown and adulticidal activities against females of the three species was achieved by a combination of 2.5% C. citratus + 2.5% E. globulus EOs, with 36.6 to 100% knockdown rate increase and 33.5 to 98.9% mortality rate increase. This study demonstrates that all tested combinations of C. citratus and E. globulus EOs were effective adulticidal agents against females of Ae. aegypti, Ae. albopictus, and M. domestica and have a high potential for development into a botanical insecticide for controlling populations of Aedes mosquitoes and houseflies.
    Keywords:  Aedes aegypti; Aedes albopictus; Cymbopogon citratus; Eucalyptus globulus; Musca domestica; Plant essential oil
  25. Zootaxa. 2020 Mar 04. 4747(3): zootaxa.4747.3.1
    Irish SR, Kyalo D, Snow RW, Coetzee M.
      The distributions of the Afrotropical Anopheles mosquitoes were first summarized in 1938. In 2017, an extensive geo-coded inventory was published for 48 sub-Saharan African countries, including information such as sampling methods, collection dates, geographic co-ordinates and the literature consulted to produce the database. Using the information from the 2017 inventory, earlier distribution lists, museum collections and publications since 2016, this paper presents an updated, simplified list of Anopheles species by mainland countries and associated Afrotropical islands, with comments where applicable. It is intended as a supplement to the 2017 geo-coded inventory.
    Keywords:  Diptera, Africa, Anopheles, mosquitoes, inventory