bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒07‒12
twenty-two papers selected by
Richard Halfpenny
Staffordshire University

  1. PLoS Negl Trop Dis. 2020 Jul 06. 14(7): e0008450
    Li CX, Guo XX, Deng YQ, Liu QM, Xing D, Sun AJ, Wu Q, Dong YD, Zhang YM, Zhang HD, Cao WC, Qin CF, Zhao TY.
      BACKGROUND: Zika virus (ZIKV) disease outbreaks have been occurring in South America since 2015, and has spread to North America. Because birth defects and cases of Guillain Barré have been associated with infection with ZIKV, this has drawn global attention. ZIKV is generally considered an Aedes-transmitted pathogen. The transmission of ZIKV through blood by Aedes mosquito bites has been recognized as the major transmission route. However, it is not clear whether there are other transmission routes that can cause viral infection in mosquitos. The aim of the present study is to describe the susceptibility of Armigeres subalbatus, which often develop in human waste lagoons, to ZIKV, through oral infection in adult mosquitoes and urine infection in larvae.METHODOLOGY/PRINCIPAL FINDINGS: Five-day-old female Ar. subalbatus ingested infectious blood meals containing ZIKV. After 4, 7, and 10 days of ingesting infectious blood meals, ZIKV could be detected in the midguts, salivary glands, ovaries, and collected saliva of mosquitoes. The ZIKV infection rate (IR) on day 10 reached 40% in salivary glands and 13% in saliva, indicating that these mosquitoes were able to transmit ZIKV. In addition, ZIKV infection was also discovered in mosquito ovaries, suggesting the possibility of vertical transmission of virus. Moreover, Ar. subalbatus transmitted ZIKV to infant mice bitten by infectious mosquitoes. In a second experiment, 1st-instar larvae of Ar. subalbatus were reared in water containing ZIKV and human urine. After pupation, pupae were placed in clean water and transferred to a mosquito cage for emergence. Although ZIKV RNA was detected in all of the larvae tested, ZIKV was not detected in the saliva of any adult Ar. subalbatus. Considering that there are more uncontrollable factors in nature than in the laboratory environment, the possibility that the virus is transmitted to adult mosquitoes via larvae is very small period.
    CONCLUSIONS/SIGNIFICANCE: Adult Ar. subalbatus could be infected with ZIKV and transmit ZIKV through mosquito bites. Therefore, in many rural areas in China and in undeveloped areas of other Asian countries, the management of human waste lagoons in the prevention and control of Zika disease should be considered. Corresponding adjustments and modifications should also be made in prevention and control strategies against ZIKV.
  2. Vector Borne Zoonotic Dis. 2020 Jul 07.
    Zhu C, Jiang Y, Zhang Q, Gao J, Gu Z, Lan C, Li C, Li C, Dong Y, Xing D, Li J, Guo X, Zhao T.
      Zika virus (ZIKV) is a mosquito-borne pathogen classified in the genus Flavivirus of the family Flaviviridae. Vertical transmission is considered to be the primary way to maintain some arboviruses under adverse natural conditions, which play a critical epidemiological role in arbovirus spread and maintenance. Aedes aegypti is the primary vector for ZIKV. In this study, we demonstrated vertical transmission in two Ae. aegypti strains from Jiegao (JG) and Mengding (MD) in the border area of Yunnan province. The minimum infection rate of F1 adult progeny from JG Ae. aegypti strain was significantly higher than that of MD Ae. aegypti strain in the second gonotrophic cycle (1:14.29 and 1:200, respectively, p < 0.05). The cytopathic effect was observed in C6/36 cells after infection of ZIKV isolated from the progeny. The results suggest that Ae. aegypti mosquitoes from JG and MD play potential roles in ZIKV spread and maintenance. Therefore, more adult and eggs control methods should be implemented to control mosquitoes if a Zika epidemic occurs.
    Keywords:  Aedes aegypti; Yunnan province; Zika virus; vertical transmission
  3. PLoS One. 2020 ;15(7): e0228835
    Esterly AT, Alemayehu D, Rusmisel B, Busam J, Shelton TL, Sebay T, Zahiri N, Huston JW, Clausnitzer RJ, Haas-Stapleton EJ.
      The mosquito Culex erythrothorax Dyar is a West Nile virus (WNV) vector that breeds in wetlands with emergent vegetation. Urbanization and recreational activities near wetlands place humans, birds and mosquitoes in close proximity, increasing the risk of WNV transmission. Adult Cx. erythrothorax abundance peaked in a wetland bordering the San Francisco Bay of California (USA) during the first 3 hours after sunset (5527 ± 4070 mosquitoes / trap night) while peak adult Culex tarsalis Coquillett abundance occurred during the subsequent 3 h period (83 ± 30 Cx. tarsalis). When insecticide resistance was assessed using bottle bioassay, Cx. erythrothorax was highly sensitive to permethrin, naled, and etofenprox insecticides compared to a strain of Culex pipiens that is susceptible to insecticides (LC50 = 0.35, 0.71, and 4.1 μg/bottle, respectively). The Cx. erythrothorax were 2.8-fold more resistant to resmethrin, however, the LC50 value was low (0.68 μg/bottle). Piperonyl butoxide increased the toxicity of permethrin (0.5 μg/bottle) and reduced knock down time, but a higher permethrin concentration (2.0 μg/bottle) did not have similar effects. Bulk mixed-function oxidase, alpha-esterase, or beta-esterase activities in mosquito homogenates were higher in Cx. erythrothorax relative to the Cx. pipiens susceptible strain. There was no difference in the activity of glutathione S-transferase between the two mosquito species and insensitive acetylcholine esterase was not detected. Larvicides that were applied to the site had limited impact on reducing mosquito abundance. Subsequent removal of emergent vegetation in concert with larvicide applications and reduced daily environmental temperature substantially reduced mosquito abundance. To control Cx. erythrothorax in wetlands, land managers should consider vegetation removal so that larvicide can efficiently enter the water. Vector control agencies may more successfully control adult viremic Cx. erythrothorax that enter nearby neighborhoods by applying adulticides during the 3 h that follow sunset.
  4. Proc Biol Sci. 2020 Jul 08. 287(1930): 20200119
    Blagrove MSC, Caminade C, Diggle PJ, Patterson EI, Sherlock K, Chapman GE, Hesson J, Metelmann S, McCall PJ, Lycett G, Medlock J, Hughes GL, Della Torre A, Baylis M.
      Mosquito-borne Zika virus (ZIKV) transmission has almost exclusively been detected in the tropics despite the distributions of its primary vectors extending farther into temperate regions. Therefore, it is unknown whether ZIKV's range has reached a temperature-dependent limit, or if it can spread into temperate climates. Using field-collected mosquitoes for biological relevance, we found that two common temperate mosquito species, Aedes albopictus and Ochlerotatus detritus, were competent for ZIKV. We orally exposed mosquitoes to ZIKV and held them at between 17 and 31°C, estimated the time required for mosquitoes to become infectious, and applied these data to a ZIKV spatial risk model. We identified a minimum temperature threshold for the transmission of ZIKV by mosquitoes between 17 and 19°C. Using these data, we generated standardized basic reproduction number R0-based risk maps and we derived estimates for the length of the transmission season for recent and future climate conditions. Our standardized R0-based risk maps show potential risk of ZIKV transmission beyond the current observed range in southern USA, southern China and southern European countries. Transmission risk is simulated to increase over southern and Eastern Europe, northern USA and temperate regions of Asia (northern China, southern Japan) in future climate scenarios.
    Keywords:  Aedes; EIP; R0; Zika; climate change
  5. Acta Trop. 2020 Jul 07. pii: S0001-706X(20)30567-2. [Epub ahead of print] 105624
    Pruett G, Hawes J, Varnado W, Deerman H, Goddard J, Burkett-Cadena N, Kearney C.
      Mosquitoes rely upon plant nectars for their energy needs, a trait that has the potential to allow nectar to serve as a platform for producing and delivering toxins to nuisance and/or vector mosquito species. Impatiens walleriana (Order: Ericales, Family: Balsaminaceae) is a readily transformable and widely planted nectar plant that has been previously shown to attract mosquito nectar-feeding. However, those feeding studies were only conducted indoors and did not test if variable environmental conditions will affect nectar feeding. In this study, we tested incidence of nectar feeding from the extrafloral nectaries of I. walleriana with the mosquitoes Aedes aegypti, Ae. albopictus and Culex quinquefasciatus (Order: Diptera, Family: Culicidae) in simulated, outdoor garden settings in Mississippi and Florida. I. walleriana and other common garden plants (in a 1:4 ratio) were placed into a mesh-lined 4'x7' mesocosm along with 50 mosquitoes. To track nectar feeding, the nectar of I. walleriana was tagged with red dye and mosquitoes were analyzed for red dye fluorescence after feeding. Fluorescence analysis demonstrated that 81.9% of male and 86.6% of female mosquitoes fed on the nectar of I. walleriana within 24 hours. This suggests that mosquitoes may readily feed on impatiens nectar in outdoor garden settings at temperature and semi-tropical sites, even when alternate common garden plants are available. This attraction capacity is essential for the further consideration of I. walleriana for development as a transgenic, mosquitocidal nectar plant.
    Keywords:  Feeding; Humidity; Mesocosm; Mosquito; Nectar; Plant
  6. Heliyon. 2020 Jun;6(6): e04322
    Amarasinghe LD, Wickramarachchi PASR, Aberathna AAAU, Sithara WS, De Silva CR.
      The present study reports mosquito larvicidal potential of green synthesized silver nanoparticles by using Annona glabra leaves (An-AgNPs). Synthesized An-AgNPs were characterized by Ultraviolet-Visible spectroscopy (UV-VIS), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) technique and Fourier transform infrared spectroscopy (FTIR). Colur change from pale yellow to brick red of the plant extract and AgNO3 solution indicated the formation of An-AgNPs initially. Surface Plasmon Resonance (SPR) band at 435 nm in the UV-Vis confirmed the formation of An-AgNPs. SEM images showed that An-AgNPs were spherical in shape. FTIR proved that An-AgNPs were functionalized with biomolecules in A. glabra leaves. Based on DLS analysis the average size range of synthesized An-AgNPs was determine to be 10-100 nm and 100-1000 nm. Third instar larvae of dengue vector mosquitoes, Aedes aegypti and Aedes albopictus were subjected to larvicidal bioassays in a range of concentrations of An-AgNPs and A. glabra crude aqueous leaf extract (2-10 mg/L). An-AgNPs exhibited very high larvicidal activity against dengue vector mosquito larvae; LC50 value for Ae. aegypti at 24 h exposure to An-AgNPs (Plant extract: AgNO3 1 : 10) 5.29 mg/L; An-AgNPs (Plant extract: AgNO3 2 : 10) 2.43 mg/L while LC50 value for Ae. albopictus at 24 h exposure to An-AgNPs (Plant extract: AgNO31:10) 3.02 mg/L; An-AgNPs (Plant extract: AgNO3 2:10) 2.51 mg/L. LC50 values obtained for A. glabra leaf extract tested against Ae. aegypti and Ae. albopictus are 5.94 mg/L and 5.00 mg/L respectively at 24-hour exposure. This study further revealed that Ae. albopictus is more susceptible than to Ae. aegypti to a given concentration of An-AgNPs and to crude aqueous leaf extract of A. glabra. Larvicidal effect of An-AgNPs is superior to the crude aqueous leaf extract of A. glabra. An-AgNPs is a potent larvicide for dengue vector control.
    Keywords:  Aedes aegypti; Aedes albopictus; Annona glabra; Chemistry; Environmental science; Green synthesis; Larvicidal activity; Silver nanoparticle
  7. Viruses. 2020 Jul 02. pii: E719. [Epub ahead of print]12(7):
    Alto BW, Civana A, Wiggins K, Eastmond B, Shin D.
      Mayaro virus is a mosquito-borne Alphavirus endemic to forests of tropical South America with a sylvatic cycle involving non-human primates and Haemagogus mosquitoes. Human infection with Mayaro virus causes a febrile illness and long-lasting arthralgia and cases are often associated with exposure to tropical forest habitats. Human movement between tropical forest habitats and urban settings may allow for imported cases and subsequent local transmission by domestic mosquito Aedes aegypti. The relative importance of Ae. aegypti as a vector of Mayaro virus may depend on the pathogenic effects of the virus on fitness correlates, especially those entomological parameters that relate to vectorial capacity. We performed mosquito infection studies and compared adult survival and fecundity of females from Brazilian and Floridian populations of Ae. aegypti following oral ingestion of uninfectious (control) and Mayaro virus infectious blood. Mayaro virus infected and refractory mosquitoes had similar or 30-50% lower fecundity than control (unexposed) mosquitoes, suggesting a reproductive cost to mounting an immune response or phenotypic expression of refractoriness. Survival of adult female mosquitoes and targeted gene expression in the Toll and IMD pathways were not altered by Mayaro virus infection. Adult lifespan and fecundity estimates were independent of measured viral titer in the bodies of mosquitoes. The lack of adverse effects of infection status on female survival suggests that Mayaro virus will not alter vectorial capacity mediated by changes in this parameter.
    Keywords:  arbovirus infection; cost of infection; immune response; mosquito; reproduction; survival
  8. J Med Entomol. 2020 Jul 05. pii: tjaa136. [Epub ahead of print]
    Karisa J, Muriu S, Omuoyo D, Karia B, Ngari M, Nyamwaya D, Rono M, Warimwe G, Mwangangi J, Mbogo CM.
      The purpose of this study was to determine the ecology of the common arboviral mosquito vectors in Mombasa, Kilifi and Malindi urban areas of coastal Kenya. Mosquito larvae were collected using standard dippers and pipettes. Egg survivorship in dry soil was evaluated by collecting soil samples from dry potential larval developmental sites, re-hydrating them for hatching and rearing of the eventual larvae to adults. Adult mosquitoes were collected with CDC light traps and BG-Sentinel traps. All blood-fed females were tested for bloodmeal origin. Mosquitoes were screened for arboviruses using RT-qPCR. Overall, the predominant species were Culex quinquefasciatus (Say) 72.4% (n = 2,364) and Aedes aegypti (L.), 25.7%, (n = 838). A total of 415 larval developmental sites were identified indoors (n = 317) and outdoors (n = 98). The most productive larval developmental sites, both indoors and outdoors, were assorted small containers, water tanks, drainages, drums, and jerricans. Overall, 62% (n = 18) of the soil samples collected were positive for larvae which were used as a proxy to measure the presence of eggs. The mosquitoes fed on humans (29.8%) and chickens (3.7%). Of 259 mosquitoes tested for viral infection, 11.6% were positive for Flavivirus only. The most productive larval developmental sites for arboviral vectors indoors were small containers, water tanks, jerricans, and drums whereas small containers, water tanks, drainage channels, buckets, tires, and water troughs were the productive larval developmental sites outdoors.
    Keywords:   Aedes ; Culex ; arbovirus; ecology
  9. J Med Entomol. 2020 Jul 05. pii: tjaa133. [Epub ahead of print]
    Hernández-Rodríguez JL, Perez-Pacheco R, Vásquez-López A, Mejenes-Hernández MC, Granados-Echegoyen CA, Arcos-Cordova IDR, Pérez-Rentería C, Benítez-Alva JI, Manrique-Saide P, Huerta H.
      This report describes the presence of Aedes albopictus Skuse (Diptera: Culicidae) in Yucatan Peninsula and represents the first record of the Asian tiger invasive mosquito in Campeche State, southeastern Mexico. We collected specimens using 11,326 ovitraps put into houses of urban and rural areas, as part of the entomological surveillance by the local Ministry of Health from January 2019 to February 2020. We found Ae. albopictus in five of the 12 municipalities of Campeche (San Francisco de Campeche, Tenabo, Hecelchakán, Calkíni and Escárcega). We record 68 positive ovitraps and 226 Ae. albopictus larvae. This finding increases the number of mosquito species recorded in Campeche, Mexico, and possibly the potential for 22 arbovirus transmission.
    Keywords:   Aedes albopictus ; Campeche; Mexico; ovitraps; surveillance
  10. Sci Rep. 2020 Jul 09. 10(1): 11379
    Nabet C, Chaline A, Franetich JF, Brossas JY, Shahmirian N, Silvie O, Tannier X, Piarroux R.
      Vector control programmes are a strategic priority in the fight against malaria. However, vector control interventions require rigorous monitoring. Entomological tools for characterizing malaria transmission drivers are limited and are difficult to establish in the field. To predict Anopheles drivers of malaria transmission, such as mosquito age, blood feeding and Plasmodium infection, we evaluated artificial neural networks (ANNs) coupled to matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) and analysed the impact on the proteome of laboratory-reared Anopheles stephensi mosquitoes. ANNs were sensitive to Anopheles proteome changes and specifically recognized spectral patterns associated with mosquito age (0-10 days, 11-20 days and 21-28 days), blood feeding and P. berghei infection, with best prediction accuracies of 73%, 89% and 78%, respectively. This study illustrates that MALDI-TOF MS coupled to ANNs can be used to predict entomological drivers of malaria transmission, providing potential new tools for vector control. Future studies must assess the field validity of this new approach in wild-caught adult Anopheles. A similar approach could be envisaged for the identification of blood meal source and the detection of insecticide resistance in Anopheles and to other arthropods and pathogens.
  11. Viruses. 2020 Jul 03. pii: E720. [Epub ahead of print]12(7):
    Knap N, Korva M, Ivović V, Kalan K, Jelovšek M, Sagadin M, Zakotnik S, Strašek Smrdel K, Slunečko J, Avšič-Županc T.
      West Nile virus (WNV) is a flavivirus transmitted by mosquitoes. Birds are the reservoir for the virus; humans, horses and other mammals are dead-end hosts. Infections caused by WNV in humans can vary from asymptomatic infections to West Nile fever (WNF) or West Nile neuroinvasive disease (WNND). In 1995, a serosurvey was performed in Slovenia on forest workers, and WNV specific IgG antibodies were confirmed in 6.8% of the screened samples, indicating that WNV is circulating in Slovenia. No human disease cases were detected in Slovenia until 2013, when the first case of WNV infection was confirmed in a retrospective study in a 79-year old man with meningitis. In 2018, three patients with WNND were confirmed by laboratory tests, with detection of IgM antibodies in the cerebrospinal fluid of the patients. In one of the patients, WNV RNA was detected in the urine sample. In 2017, 2018 and 2019, a mosquito study was performed in Slovenia. Mosquitoes were sampled on 14 control locations and 35 additional locations in 2019. No WNV was detected in mosquitoes in 2017 and 2019, but we confirmed the virus in a pool of Culex sp. mosquitoes in 2018. The virus was successfully isolated, and complete genome sequence was acquired. The whole genome of the WNV was also sequenced from the patient's urine sample. The whole genome sequences of the WNV virus detected in Slovenian patient and mosquito indicate the virus most likely spread from the north, because of the geographic proximity and because the sequences cluster with the Austrian and Hungarian sequences. A sentinel study was performed on dog sera samples, and we were able to confirm IgG antibodies in 1.8% and 4.3% of the samples in 2017 and 2018, respectively. Though Slovenia is not a highly endemic country for WNV, we have established that the virus circulates in Slovenia.
    Keywords:  Slovenia; WNND; WNV; mosquitoes
  12. Trop Med Infect Dis. 2020 Jul 07. pii: E114. [Epub ahead of print]5(3):
    Ab Hamid N, Mohd Noor SN, Isa NR, Md Rodzay R, Bachtiar Effendi AM, Hafisool AA, Azman FA, Abdullah SF, Kamarul Zaman MK, Mohd Norsham MI, Amanzuri NH, Abd Khalil N, Zambari IF, Mat Rani AN, Ariffin FD, Omar T, Wasi Ahmad N, Lee HL.
      Dengue is placing huge burdens on the Malaysian healthcare system as well as the economy. With the expansion in the number of high-rise residential buildings, particularly in the urban centers, the flight range and behavior of Aedes mosquitoes may be altered in this habitat type. In this study, we aimed to expand the understanding of the vertical distribution and dispersal of Aedes in nine selected high-rise residences in Kuala Lumpur, Selangor, and Johor using ovitraps as the sampling method. We discovered that Ae. aegypti is the predominant species in all study sites. Both Ae. aegypti and Ae. albopictus are most abundant within the first three levels and could be found up to level 21 (approximately 61.1-63.0 m). Pearson correlation analyses exhibited negative correlations in eight out of nine study sites between the ovitrap indexes (OIs) within each floor level, suggesting that Aedes density decreased as the building level increased. Our findings provide information to the public health authorities on 'hot spot' floors for effective suppression of dengue transmission.
    Keywords:  Aedes; dengue; high-rise residences; mosquito; surveillance; vertical dispersal
  13. Pest Manag Sci. 2020 Jul 10.
    Cantrell CL, Zaki MA, Reichley A, Sink M, Kim SJ, Ali A.
      BACKGROUND: Mosquitoes remain one of the most significant threats to the health of humans throughout the world. This study was designed to evaluate the biting deterrent effects of a series of ester analogs of undecanoic (C:11:0) and dodecanoic acids (C:12:0) against Aedes aegypti (L), (Diptera: Culicidae), the yellow fever mosquito, using K&D and A&K bioassay systems.RESULTS: In the K&D bioassays, C:11:0 esters methyl undecanoate, propyl undecanoate, butyl undecanoate, and pentyl undecanoate, and the C:12:0 esters methyl dodecanoate, ethyl dodecanoate, propyl dodecanoate, octyl dodecanoate, and dodecyl dodecanoate were most active. All of these esters were as effective as DEET and as effective as the parent acids undecanoic acid and dodecanoic acid with biting deterrence index (BDI) values ranging from 0.80 to 0.99. In the in-vitro A&K bioassay undecanoic acid with a minimum effective dose (MED) of 3.125 μg/cm2 was the most active compound and showed higher activity than DEET (MED of 25 μg/cm2 ). The most active synthetic analog was butyl undecanoate with an MED of 12.5 μg/cm2 . The next most active analogs are the methyl ester analogs methyl undecanoate and methyl dodecanoate both with MED values of 25 μg/cm2 .
    CONCLUSION: Fatty acid synthetic esters and structural analogs are a promising source of new mosquito repelling compounds and should be investigated further. This article is protected by copyright. All rights reserved.
    Keywords:  A & K bioassay; Aedes aegypti; K & D bioassay; biting deterrence; fatty acid; mosquitoes; natural products; repellency
  14. BMC Med. 2020 Jul 09. 18(1): 186
    Brady OJ, Kharisma DD, Wilastonegoro NN, O'Reilly KM, Hendrickx E, Bastos LS, Yakob L, Shepard DS.
      BACKGROUND: Release of virus-blocking Wolbachia-infected mosquitoes is an emerging disease control strategy that aims to control dengue and other arboviral infections. Early entomological data and modelling analyses have suggested promising outcomes, and wMel Wolbachia releases are now ongoing or planned in 12 countries. To help inform government, donor, or philanthropist decisions on scale-up beyond single city releases, we assessed this technology's cost-effectiveness under alternative programmatic options.METHODS: Using costing data from existing Wolbachia releases, previous dynamic model-based estimates of Wolbachia effectiveness, and a spatially explicit model of release and surveillance requirements, we predicted the costs and effectiveness of the ongoing programme in Yogyakarta City and three new hypothetical programmes in Yogyakarta Special Autonomous Region, Jakarta, and Bali.
    RESULTS: We predicted Wolbachia to be a highly cost-effective intervention when deployed in high-density urban areas with gross cost-effectiveness below $1500 per DALY averted. When offsets from the health system and societal perspective were included, such programmes even became cost saving over 10-year time horizons with favourable benefit-cost ratios of 1.35 to 3.40. Sequencing Wolbachia releases over 10 years could reduce programme costs by approximately 38% compared to simultaneous releases everywhere, but also delays the benefits. Even if unexpected challenges occurred during deployment, such as emergence of resistance in the medium-term or low effective coverage, Wolbachia would remain a cost-saving intervention.
    CONCLUSIONS: Wolbachia releases in high-density urban areas are expected to be highly cost-effective and could potentially be the first cost-saving intervention for dengue. Sites with strong public health infrastructure, fiscal capacity, and community support should be prioritised.
    Keywords:  Cost-effectiveness analysis; Dengue; Indonesia; Maps; Model; Mosquito; Policy; Spatial; Wolbachia
  15. BMC Public Health. 2020 Jul 06. 20(1): 1065
    Vitale M, Lupone CD, Kenneson-Adams A, Ochoa RJ, Ordoñez T, Beltran-Ayala E, Endy TP, Rosenbaum PF, Stewart-Ibarra AM.
      BACKGROUND: Dengue is a major emerging infectious disease, endemic throughout the tropics and subtropics, with approximately 2.5 billion people at risk globally. Active (AS) and passive surveillance (PS), when combined, can improve our understanding of dengue's complex disease dynamics to guide effective, targeted public health interventions. The objective of this study was to compare findings from the Ministry of Health (MoH) PS to a prospective AS arbovirus research study in Machala, Ecuador in 2014 and 2015.METHODS: Dengue cases in the PS system were compared to laboratory confirmed acute dengue illness cases that entered the AS study during the study period. Variables of interest included age class and sex. Outbreak detection curves by epidemiologic week, overall cumulative incidence and age-specific incidence proportions were calculated. Descriptive statistics were tabulated for all variables of interest. Chi-square tests were performed to compare demographic characteristics between the AS and PS data sets in 2014 and 2015.
    RESULTS: 177 and 245 cases were identified from 1/1/2014 to 12/31/2015 by PS and AS, respectively; nine cases appeared in both systems. AS identified a greater number of laboratory-confirmed cases in 2014, accounting for more than 60% of dengue cases in the study area. In 2015, the opposite trend was observed with PS identifying 60% of the dengue cases in the study area. Peak transmission time in laboratory confirmed dengue illness, as noted by AS and PS was similar in 2014, whereas earlier detection (7 weeks) was observed by AS in 2015. Younger patients were more frequently identified by PS, while older patients were identified more frequently by AS. The cumulative incidence proportion for laboratory confirmed dengue illness reported via PS to the MoH was 4.12 cases per 10,000 residents in 2014, and 2.21 cases per 10,000 residents in 2015.
    CONCLUSIONS: Each surveillance system captured distinct demographic subgroups within the Machala population, possibly due to differences in healthcare seeking behaviors, access to care, emerging threats of other viruses transmitted by the same mosquito vector and/or differences in clinical presentation. Integrating AS with pre-existing PS can aid in identifying additional cases in previously underdiagnosed subpopulations, improving our understanding of disease dynamics, and facilitating the implementation of timely public health interventions.
    Keywords:  Active surveillance; Arboviral; Dengue; Ecuador; Latin America; Passive surveillance; Public health intervention
  16. Insects. 2020 Jun 30. pii: E406. [Epub ahead of print]11(7):
    Bryant WB, Ray S, Mills MK.
      Malaria is a major global health problem, where the anautogenous female mosquito Anopheles gambiae serves as a major vector. In order to combat this devastating disease, understanding mosquito physiology is paramount. Numerous studies in the vector field demonstrate that small non-coding RNAs (ncRNAs) play essential roles in numerous aspects of mosquito physiology. While our previous miRNA annotation work demonstrated expression dynamics across differing tissues, miRNAs represented less than 20% of all small ncRNAs in our small RNA-Seq libraries. To this end, we systematically classified multiple small ncRNA groups across mosquito tissues. Here we (i) determined a new enriched-midgut miRNA, (ii) updated the piRNA annotation in ovaries with a genomic map of unique-mapping piRNAs, (iii) identified pan-tissue and tissue-enriched mRNA-derived small ncRNAs, and (iv) assessed AGO1- and AGO2- loading of candidate small ncRNAs. Continued research will broaden our view of small ncRNAs and greatly aide in our understanding on how these molecules contribute to mosquito physiology.
    Keywords:  mosquito reproduction; piRNA; small RNAs; small non-coding RNA
  17. Travel Med Infect Dis. 2020 Jul 03. pii: S1477-8939(20)30311-2. [Epub ahead of print] 101815
    Fischer L, Gültekin N, Kaelin MB, Fehr J, Schlagenhauf P.
      BACKGROUND: Malaria is one of the most life-threatening vector-borne diseases globally. Recent autochthonous cases registered in several European countries have raised awareness regarding the threat of malaria reintroduction to Europe. An increasing number of imported malaria cases today occur due to international travel and migrant flows from malaria-endemic countries. The cumulative factors of the presence of competent vectors, favourable climatic conditions and evidence of increasing temperatures might lead to the re-emergence of malaria in countries where the infection was previously eliminated.METHODS: We performed a systematic literature review following PRISMA guidelines. We searched for original articles focusing on rising temperature and the receptivity to malaria transmission in Europe. We evaluated the quality of the selected studies using a standardised tool.
    RESULTS: The search resulted in 1'999 articles of possible relevance and after screening we included 10 original research papers in the quantitative analysis for the systematic review. With further increasing temperatures studies predicted a northward spread of the occurrence of Anopheles mosquitoes and an extension of seasonality, enabling malaria transmission for annual periods up to 6 months in the years 2051-2080. Highest vector stability and receptivity were predicted in Southern and South-Eastern European areas. Anopheles atroparvus, the main potential malaria vector in Europe, might play an important role under changing conditions favouring malaria transmission.
    CONCLUSION: The receptivity of Europe for malaria transmission will increase as a result of rising temperature unless socioeconomic factors remain favourable and appropriate public health measures are implemented. Our systematic review serves as an evidence base for future preventive measures.
    Keywords:  1.9 climate change; Anopheles; Breeding; Europe; Global warming; Incubation; Malaria; Plasmodium; Rising temperature
  18. PLoS One. 2020 ;15(7): e0235631
    Cirera L, Galatas B, Alonso S, Paaijmans K, Mamuquele M, Martí-Soler H, Guinovart C, Munguambe H, Luis F, Nhantumbo H, Montañà J, Bassat Q, Candrinho B, Rabinovich R, Macete E, Aide P, Alonso P, Saúte F, Sicuri E.
      BACKGROUND: As new combinations of interventions aiming at interrupting malaria transmission are under evaluation, understanding the associated economic costs and benefits is critical for decision-making. This study assessed the economic cost and cost-effectiveness of the Magude project, a malaria elimination initiative implemented in a district in southern Mozambique (i.e. Magude) between August 2015-June 2018. This project piloted a combination of two mass drug administration (MDA) rounds per year for two consecutive years, annual rounds of universal indoor residual spraying (IRS) and a strengthened surveillance and response system on the back of universal long-lasting insecticide treated net (LLIN) coverage and routine case management implemented by the National Malaria Control Program (NMCP). Although local transmission was not interrupted, the project achieved large reductions in the burden of malaria in the target district.METHODS: We collected weekly economic data, estimated costs from the project implementer perspective and assessed the incremental cost-effectiveness ratio (ICER) associated with the Magude project as compared to routine malaria control activities, the counterfactual. We estimated disability-adjusted life years (DALYs) for malaria cases and deaths and assessed the variation of the ICER over time to capture the marginal costs and effectiveness associated with subsequent phases of project implementation. We used deterministic and probabilistic sensitivity analyses to account for uncertainty and built an alternative scenario by assuming the implementation of the interventions from a governmental perspective. Economic costs are provided in constant US$2015.
    RESULTS: After three years, the Magude project averted a total of 3,171 DALYs at an incremental cost of $2.89 million and an average yearly cost of $20.7 per targeted person. At an average cost of $19.4 per person treated per MDA round, the social mobilization and distribution of door-to-door MDA contributed to 53% of overall resources employed, with personnel and logistics being the main cost drivers. The ICER improved over time as a result of decreasing costs and improved effectiveness. The overall ICER was $987 (CI95% 968-1,006) per DALY averted, which is below the standard cost-effectiveness (CE) threshold of $1,404/DALY averted, three times the gross domestic product (GDP) per capita of Mozambique, but above the threshold of interventions considered highly cost-effective (one time the GDP per capita or $468/DALY averted) and above the recently suggested thresholds based on the health opportunity cost ($537 purchasing power parity/ DALY averted). A significantly lower ICER was obtained in the implementation scenario from a governmental perspective ($441/DALY averted).
    CONCLUSION: Despite the initial high costs and volume of resources associated with its implementation, MDA in combination with other existing malaria control interventions, can be a cost-effective strategy to drastically reduce transmission in areas of low to moderate transmission in sub-Saharan Africa. However, further studies are needed to understand the capacity of the health system and financial affordability to scale up such strategies at regional or national level.
  19. Data Brief. 2020 Aug;31 105882
    Dom NC, Alhothily IA, Camalxaman SN, Ismail SNS.
      In this article, data on the demographic parameters of the Aedes albopictus were collected from those areas in Shah Alam, Malaysia that had experienced a dengue outbreak. The surveys were conducted from March to December 2017. The eggs of the Ae. albopictus were collected using ovitraps, and were analysed based on the demographic parameters in a controlled environment in an insectarium. The data were comprised of four types of biological information on the life demographic parameters of the Ae. albopictus that were monitored based on specific localities. The data were inferred information regarding egg productivity (n), egg development (%), immature development (days), and survivorship (days).
    Keywords:  Aedes albopictus; Demographic parameters; Dengue areas; Malaysia
  20. Health Promot Int. 2020 Jul 10. pii: daaa049. [Epub ahead of print]
    Allen T, Crouch A, Topp SM.
      High-income countries (HICs) in sub-tropical and tropical regions are at an increasing risk of Aedes mosquito-borne disease (MBD) outbreaks such as dengue fever. As the Aedes mosquito predominately lives and breeds in and around people's homes, community participation in MBD management is an important part of preventing MBD outbreaks. Historically, government-led strategies have dominated community participation efforts as opposed to strategies co-designed or led by the community. A scoping review was conducted to describe the community participation and empowering approaches used in Aedes mosquito management specifically in HICs, and to identify any reported outcomes of these methods. A systematic search of peer-reviewed literature using electronic databases Medline (OVID), Web of Science, Scopus and ProQuest-Science and Technology as well as grey literature, found 19 studies that matched the review criteria. The review findings highlight a lack of empirical evidence to inform participatory and empowering approaches to mosquito management in HICs. Moreover, the rationale for using predominantly government-led approaches is not clear. Further research is required to better understand best approaches and barriers to employing empowering approaches in mosquito management in HICs.
    Keywords:   Aedes mosquito; community empowerment; community participation; high-income countries
  21. J Med Entomol. 2020 Jul 08. pii: tjaa139. [Epub ahead of print]
    Westby KM, Medley KA.
      As the planet becomes increasingly urbanized, it is imperative that we understand the ecological and evolutionary consequences of urbanization on species. One common attribute of urbanization that differs from rural areas is the prevalence of artificial light at night (ALAN). For many species, light is one of the most important and reliable environmental cues, largely governing the timing of daily and seasonal activity patterns. Recently, it has been shown that ALAN can alter behavioral, phenological, and physiological traits in diverse taxa. For temperate insects, diapause is an essential trait for winter survival and commences in response to declining daylight hours in the fall. Diapause is under strong selection pressure in the mosquito, Aedes albopictus (Skuse); local adaptation and rapid evolution has been observed along a latitudinal cline. It is unknown how ALAN affects this photosensitive trait or if local adaptation has occurred along an urbanization gradient. Using a common garden experiment, we experimentally demonstrated that simulated ALAN reduces diapause incidence in this species by as much as 40%. There was no difference, however, between urban and rural demes. We also calculated diapause incidence from wild demes in urban areas to determine whether wild populations exhibited lower than predicted incidence compared to estimates from total nocturnal darkness. In early fall, lower than predicted diapause incidence was recorded, but all demes reached nearly 100% diapause before terminating egg laying. It is possible that nocturnal resting behavior in vegetation limits the amount of ALAN exposure this species experiences potentially limiting local adaptation.
    Keywords:   Aedes albopictus ; artificial light at night; common garden; diapause; urban ecology
  22. J Infect Dis. 2020 Jul 04. pii: jiaa382. [Epub ahead of print]
    Pinilla YT, Boussougou-Sambe ST, Gräßle S, Ngossanga B, Doumba-Ndalembouly AG, Weierich A, Bingoulou G, Malinga EG, Nguiffo D, Ntoumi F, Djogbénou L, Issifou S, Wondji CS, Adegnika AA, Borrmann S, .
      Our current knowledge of the clinical burden, biology, and transmission of Plasmodium malariae is extremely scarce. To start addressing some of those questions, we experimentally infected Anopheles gambiae mosquitoes with fresh P. malariae isolates obtained from asymptomatic individuals in Lambaréné, Gabon. The proportion of mosquitoes infected via direct membrane feeding assay with either P. malariae mono-infections (16%; 19/121) or co-infections (28%; 31/112) was higher after serum replacement compared to parallel groups without serum replacement (4%, 4/102; and 4%, 2/45; p<0.01 respectively). Our results show that isolates from asymptomatic carriers can be used for experimental studies of P. malariae transmission.
    Keywords:   Anopheles gambiae ; Plasmodium malariae ; Gabon; experimental transmission