bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2021‒03‒21
twenty papers selected by
Richard Halfpenny
Staffordshire University

  1. J Med Entomol. 2021 Mar 16. pii: tjab035. [Epub ahead of print]
      The vector competence of mosquitoes for pathogens has been shown to be influenced by the status of insecticide resistance in the mosquito population. However, to date, only two studies has explored the impact of insecticide resistance on arbovirus transmission. The global and widespread use of pyrethroids has led to the development of insecticide resistance in many mosquito species, including Aedes aegypti (Linnaeus) (Diptera: Culicidae), the primary vector of Zika virus. Strains of Ae. aegypti that were genetically similar, but responded differently to pyrethroid exposure, were developed using backcrossing techniques. These populations were orally infected with Zika virus and susceptibility to infection, disseminated infection, and transmission potential were evaluated. Analyses revealed differences in susceptibility to infection and disseminated infection between the pyrethroid susceptible and resistant strains of Ae. aegypti during the infection period. Here, we identify an additional challenge to that of widespread pyrethroid resistance. Specifically, resistance is associated with altered phenotypic traits that influence susceptibility to arbovirus infection and progression of infection in the mosquito, factors which ultimately influence risk of arbovirus transmission. These findings support the need to 1) consider insecticide resistance status during times of arbovirus transmission and 2) to implement insecticide resistance management/ mitigation strategies in vector control programs.
    Keywords:   Aedes aegypti ; Zika virus; insecticide resistance; pyrethroid; vector competence
  2. Front Cell Infect Microbiol. 2021 ;11 626368
      Background: Mosquito-borne diseases are rapidly spreading due to increasing international travel and trade. Routine mosquito surveillance and screening for mosquito-borne pathogens can be early indicators for local disease transmission and outbreaks. However, arbovirus detection in mosquito vectors has rarely been reported in Saudi Arabia.Methods: A total of 769,541 Aedes and Culex mosquitoes were collected by Black Hole traps during routine mosquito surveillance in the first half of 2016. Culex. quinquefasciatus and Ae. aegypti were the most prevalent species observed. Twenty-five and 24 randomly selected pools of Ae. aegypti and Cx. quinquefasciatus, respectively, were screened for arboviruses by RT-PCR.
    Results: Dengue 2 (DENV-2) and four strains of insect-specific flaviviruses, including one of cell-fusing agent virus (CFAV) and three of Phlebotomus-associated flavivirus (PAFV) were detected in pools of Ae. aegypti. We also detected 10 strains of Culex flavivirus (CxFV) in pools of Cx. quinquefasciatus. Phylogenetic analysis using whole genome sequences placed the DENV strain into the cosmopolitan 1 sub-DENV-2 genotype, and the CxFVs into the African/Caribbean/Latin American genotype. These analyses also showed that the DENV-2 strain detected in the present study was closely related to strains detected in China in 2014 and in Japan in 2018, which suggests frequent movement of DENV-2 strains among these countries. Furthermore, the phylogenetic analysis suggested at least five introductions of DENV-2 into Saudi Arabia from 2014 through 2018, most probably from India.
    Conclusions: To our knowledge, this study reports the first detection of four arboviruses DENV, CFAV, PAFV, and CxFV in mosquitoes in Saudi Arabia, which shows that they are co-circulating in Jeddah. Our findings show a need for widespread mosquito-based arbovirus surveillance programs in Saudi Arabia, which will improve our understanding of the transmission dynamics of the mosquito-borne arboviruses within the country and help early predict and mitigate the risk of human infections and outbreaks.
    Keywords:  Aedes aegypti; Culex flavivirus; Culex quinquefasciatus; dengue virus; insect specific flavivirus
  3. Malar J. 2021 Mar 17. 20(1): 154
      BACKGROUND: Understanding malaria vector's population dynamics and their spatial distribution is important to define when and where the largest infection risks occur and implement appropriate control strategies. In this study, the seasonal spatio-temporal dynamics of the malaria vector population and transmission intensity along intermittent rivers in a semi-arid area of central Ethiopia were investigated.METHODS: Mosquitoes were collected monthly from five clusters, 2 close to a river and 3 away from a river, using pyrethrum spray catches from November 2014 to July 2016. Mosquito abundance was analysed by the mixed Poisson regression model. The human blood index and sporozoite rate was compared between seasons by a logistic regression model.
    RESULTS: A total of 2784 adult female Anopheles gambiae sensu lato (s.l.) were collected during the data collection period. All tested mosquitoes (n = 696) were identified as Anopheles arabiensis by polymerase chain reaction. The average daily household count was significantly higher (P = 0.037) in the clusters close to the river at 5.35 (95% CI 2.41-11.85) compared to the clusters away from the river at 0.033 (95% CI 0.02-0.05). Comparing the effect of vicinity of the river by season, a significant effect of closeness to the river was found during the dry season (P = 0.027) and transition from dry to wet season (P = 0.032). Overall, An. arabiensis had higher bovine blood index (62.8%) as compared to human blood index (23.8%), ovine blood index (9.2%) and canine blood index (0.1%). The overall sporozoite rate was 3.9% and 0% for clusters close to and away from the river, respectively. The overall Plasmodium falciparum and Plasmodium vivax entomologic inoculation rates for An. arabiensis in clusters close to the river were 0.8 and 2.2 infective bites per person/year, respectively.
    CONCLUSION: Mosquito abundance and malaria transmission intensity in clusters close to the river were higher which could be attributed to the riverine breeding sites. Thus, vector control interventions including targeted larval source management should be implemented to reduce the risk of malaria infection in the area.
    Keywords:  Clusters; Ethiopia; Intermittent rivers; Malaria; Seasonal dynamics; Transmission intensity
  4. PLoS Negl Trop Dis. 2021 Mar;15(3): e0009182
      Climate change and variability influence temperature and rainfall, which impact vector abundance and the dynamics of vector-borne disease transmission. Climate change is projected to increase the frequency and intensity of extreme climate events. Mosquito-borne diseases, such as dengue fever, are primarily transmitted by Aedes aegypti mosquitoes. Freshwater availability and temperature affect dengue vector populations via a variety of biological processes and thus influence the ability of mosquitoes to effectively transmit disease. However, the effect of droughts, floods, heat waves, and cold waves is not well understood. Using vector, climate, and dengue disease data collected between 2013 and 2019 in Kenya, this retrospective cohort study aims to elucidate the impact of extreme rainfall and temperature on mosquito abundance and the risk of arboviral infections. To define extreme periods of rainfall and land surface temperature (LST), we calculated monthly anomalies as deviations from long-term means (1983-2019 for rainfall, 2000-2019 for LST) across four study locations in Kenya. We classified extreme climate events as the upper and lower 10% of these calculated LST or rainfall deviations. Monthly Ae. aegypti abundance was recorded in Kenya using four trapping methods. Blood samples were also collected from children with febrile illness presenting to four field sites and tested for dengue virus using an IgG enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). We found that mosquito eggs and adults were significantly more abundant one month following an abnormally wet month. The relationship between mosquito abundance and dengue risk follows a non-linear association. Our findings suggest that early warnings and targeted interventions during periods of abnormal rainfall and temperature, especially flooding, can potentially contribute to reductions in risk of viral transmission.
  5. Parasit Vectors. 2021 Mar 19. 14(1): 167
      BACKGROUND: In 2015, an outbreak of Zika virus spread across Latin America and the Caribbean (LAC). Public health programs promoted vector control behaviors, including covering water storage containers with lids. Such approaches disrupt Zika transmission by eliminating the habitats of the Aedes aegypti mosquito, which breeds in stagnant water.METHODS: A quantitative household survey and observation checklist with trained enumerators were undertaken between August and October 2018 in selected urban/peri-urban USAID implementation communities in El Salvador, Guatemala, and Honduras. The survey included questions regarding knowledge, attitudes, and practices related to Zika virus. An accompanying checklist was implemented to observe water storage containers, including for short-term and long-term water use. The characteristics of these containers were tabulated, including the presence of a lid. The lids were examined for key features to determine their potential effectiveness to prevent mosquito breeding: fully covering and sealing the container, not having holes, and not having water on them (potentially creating a secondary breeding site). Multivariate logistic regression was used to estimate the effectiveness of lid types and characteristics on the presence of larvae.
    RESULTS: Overall, in adjusted models, using an effective lid versus no lid was associated with a 94% decrease in odds of larval presence in long-term water storage containers (odds ratio = 0.06; 95% confidence interval [0.029, 0.152]); however, similar impacts were not observed for washbasins in the adjusted models. Models adjusted for household wealth, receiving a visit from a vector control technician, scrubbing the container in the last 7 days, and perception of more mosquitoes around.
    CONCLUSIONS: Effective lids, if made available and coupled with complementary behavioral messaging, may reduce transmission of Zika and other Aedes mosquito-borne diseases in the LAC region.
    Keywords:  Aedes aegypti; Behavior change; Latin America and the Caribbean; Urban; Vector control; Zika virus
  6. Sci Rep. 2021 Mar 19. 11(1): 6458
      In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.
  7. Sci Rep. 2021 Mar 16. 11(1): 6081
      Although there are many studies on the control of mosquito vectors of the yellow fever virus (YFV) in tropical forests, there are still few ecological studies regarding abiotic factors effect on these mosquitoes. Here we characterize these effects on oviposition behavior, abundance, and diversity of mosquito vectors of YFV. The study was conducted in Córrego da Luz Municipal Park, in Casimiro de Abreu, Rio de Janeiro state, Brazil, from July 2018 to December 2019. Ovitraps were placed at ground level and 3 m high. The data were tested for normality using the Shapiro-Wilk test, followed by an independent sample analysis, the Mann-Whitney test. The Shannon Diversity Index was used to evaluate the abundance of mosquitos' eggs collected at both ground level and 3 m high. We highlight the presence of Haemagogus janthinomys and Hg. leucocelaenus, primary YFV vectors in forest areas. The abundance of Hg. leucocelaenus (63%), Hg. janthinomys (75%), and Aedes terrens (58%) was higher at the height of 3 m, while Ae. albopictus (52%) was higher at ground level. Aedes albopictus was positively correlated with temperature. Culicidae monitoring is essential for assessing the YFV transmission cycle in Atlantic forest fragments.
  8. Acta Trop. 2021 Mar 10. pii: S0001-706X(21)00064-4. [Epub ahead of print] 105885
      Aedes aegypti and Aedes albopictus are mosquito vectors of numerous arboviruses of sanitary importance. Presently in Argentina, neither Ae. aegypti nor Ae. albopictus, have displaced the other species in the places where they coexist, since the introduction of the latter in 1998. In this study, we evaluated whether these species coexist at different scales (ovitrap, microhabitat and habitat) in the city of Eldorado, Misiones province, northeast Argentina. We also analyzed the seasonal variation and climate variables related to the delay in egg hatching of both species. Mosquitoes were collected weekly, from June 2017 to May 2018, using ovitraps placed in urban areas. We conclude that Ae. aegypti and Ae. albopictus coexist in the study area, at the ovitrap, microhabitat and habitat scales. Furthermore, no pronounced pattern of delayed hatching has been observed for either species; however, eggs of Ae. albopictus laid during colder weeks and less rainfall needed a greater number of immersions to hatch, while for Ae. aegypti those laid during weeks with low rainfall and high temperatures showed the longest delay in hatching response.
    Keywords:  Aedes aegypti; Aedes albopictus; Coexistence; Eggs; Hatching
  9. Malar J. 2021 Mar 17. 20(1): 151
      BACKGROUND: Attractive targeted sugar baits (ATSBs) are a promising new tool for malaria control as they can target outdoor-feeding mosquito populations, in contrast to current vector control tools which predominantly target indoor-feeding mosquitoes.METHODS: It was sought to estimate the potential impact of these new tools on Plasmodium falciparum malaria prevalence in African settings by combining data from a recent entomological field trial of ATSBs undertaken in Mali with mathematical models of malaria transmission. The key parameter determining impact on the mosquito population is the excess mortality due to ATSBs, which is estimated from the observed reduction in mosquito catch numbers. A mathematical model capturing the life cycle of P. falciparum malaria in mosquitoes and humans and incorporating the excess mortality was used to estimate the potential epidemiological effect of ATSBs.
    RESULTS: The entomological study showed a significant reduction of ~ 57% (95% CI 33-72%) in mosquito catch numbers, and a larger reduction of ~ 89% (95% CI 75-100%) in the entomological inoculation rate due to the fact that, in the presence of ATSBs, most mosquitoes do not live long enough to transmit malaria. The excess mortality due to ATSBs was estimated to be lower (mean 0.09 per mosquito per day, seasonal range 0.07-0.11 per day) than the bait feeding rate obtained from one-day staining tests (mean 0.34 per mosquito per day, seasonal range 0.28-0.38 per day).
    CONCLUSIONS: From epidemiological modelling, it was predicted that ATSBs could result in large reductions (> 30% annually) in prevalence and clinical incidence of malaria, even in regions with an existing high malaria burden. These results suggest that this new tool could provide a promising addition to existing vector control tools and result in significant reductions in malaria burden across a range of malaria-endemic settings.
    Keywords:  Malaria; Mosquito; Vector control
  10. MMWR Surveill Summ. 2021 Mar 19. 70(2): 1-35
      PROBLEM/CONDITION: Malaria in humans is caused by intraerythrocytic protozoa of the genus Plasmodium. These parasites are transmitted by the bite of an infective female Anopheles species mosquito. The majority of malaria infections in the United States occur among persons who have traveled to regions with ongoing malaria transmission. However, malaria is occasionally acquired by persons who have not traveled out of the country through exposure to infected blood products, congenital transmission, nosocomial exposure, or local mosquitoborne transmission. Malaria surveillance in the United States is conducted to provide information on its occurrence (e.g., temporal, geographic, and demographic), guide prevention and treatment recommendations for travelers and patients, and facilitate rapid transmission control measures if locally acquired cases are identified.PERIOD COVERED: This report summarizes confirmed malaria cases in persons with onset of illness in 2017 and trends in previous years.
    DESCRIPTION OF SYSTEM: Malaria cases diagnosed by blood film microscopy, polymerase chain reaction, or rapid diagnostic tests are reported to local and state health departments through electronic laboratory reports or by health care providers or laboratory staff members. Case investigations are conducted by local and state health departments, and reports are transmitted to CDC through the National Malaria Surveillance System (NMSS), the National Notifiable Diseases Surveillance System (NNDSS), or direct CDC consultations. CDC reference laboratories provide diagnostic assistance and conduct antimalarial drug resistance marker testing on blood samples submitted by health care providers or local or state health departments. This report summarizes data from the integration of all cases from NMSS and NNDSS, CDC reference laboratory reports, and CDC clinical consultations.
    RESULTS: CDC received reports of 2,161 confirmed malaria cases with onset of symptoms in 2017, including two congenital cases, three cryptic cases, and two cases acquired through blood transfusion. The number of malaria cases diagnosed in the United States has been increasing since the mid-1970s; in 2017, the number of cases reported was the highest in 45 years, surpassing the previous peak of 2,078 confirmed cases reported in 2016. Of the cases in 2017, a total of 1,819 (86.1%) were imported cases that originated from Africa; 1,216 (66.9%) of these came from West Africa. The overall proportion of imported cases originating from West Africa was greater in 2017 (57.6%) than in 2016 (51.6%). Among all cases, P. falciparum accounted for the majority of infections (1,523 [70.5%]), followed by P. vivax (216 [10.0%]), P. ovale (119 [5.5%]), and P. malariae (55 [2.6%]). Infections by two or more species accounted for 22 cases (1.0%). The infecting species was not reported or was undetermined in 226 cases (10.5%). CDC provided diagnostic assistance for 9.5% of confirmed cases and tested 8.0% of specimens with P. falciparum infections for antimalarial resistance markers. Most patients (94.8%) had symptom onset <90 days after returning to the United States from a country with malaria transmission. Of the U.S. civilian patients who reported reason for travel, 73.1% were visiting friends and relatives. The proportion of U.S. residents with malaria who reported taking any chemoprophylaxis in 2017 (28.4%) was similar to that in 2016 (26.4%), and adherence was poor among those who took chemoprophylaxis. Among the 996 U.S. residents with malaria for whom information on chemoprophylaxis use and travel region were known, 93.3% did not adhere to or did not take a CDC-recommended chemoprophylaxis regimen. Among 805 women with malaria, 27 reported being pregnant. Of these, 10 pregnant women were U.S. residents, and none reported taking chemoprophylaxis to prevent malaria. A total of 26 (1.2%) malaria cases occurred among U.S. military personnel in 2017, fewer than in 2016 (41 [2.0%]). Among all reported cases in 2017, a total of 312 (14.4%) were classified as severe malaria illnesses, and seven persons died. In 2017, CDC analyzed 117 P. falciparum-positive and six P. falciparum mixed-species samples for antimalarial resistance markers (although certain loci were untestable in some samples); identification of genetic polymorphisms associated with resistance to pyrimethamine were found in 108 (97.3%), to sulfadoxine in 77 (69.4%), to chloroquine in 38 (33.3%), to mefloquine in three (2.7%), and to atovaquone in three (2.7%); no specimens tested contained a marker for artemisinin resistance. The data completeness of key variables (species, country of acquisition, and resident status) was lower in 2017 (74.4%) than in 2016 (79.4%).
    INTERPRETATION: The number of reported malaria cases in 2017 continued a decades-long increasing trend, and for the second year in a row the highest number of cases since 1971 have been reported. Despite progress in malaria control in recent years, the disease remains endemic in many areas globally. The importation of malaria reflects the overall increase in global travel to and from these areas. Fifty-six percent of all cases were among persons who had traveled from West Africa, and among U.S. civilians, visiting friends and relatives was the most common reason for travel (73.1%). Frequent international travel combined with the inadequate use of prevention measures by travelers resulted in the highest number of imported malaria cases detected in the United States in 4 decades.
    PUBLIC HEALTH ACTIONS: The best way to prevent malaria is to take chemoprophylaxis medication during travel to a country where malaria is endemic. Adherence to recommended malaria prevention strategies among U.S. travelers would reduce the numbers of imported cases; reasons for nonadherence include prematurely stopping after leaving the area where malaria was endemic, forgetting to take the medication, and experiencing a side effect. Travelers might not understand the risk that malaria poses to them; thus, health care providers should incorporate risk education to motivate travelers to be adherent to chemoprophylaxis. Malaria infections can be fatal if not diagnosed and treated promptly with antimalarial medications appropriate for the patient's age, medical history, the likely country of malaria acquisition, and previous use of antimalarial chemoprophylaxis. Antimalarial use for chemoprophylaxis and treatment should be informed by the most recent guidelines, which are frequently updated. In 2018, two formulations of tafenoquine (i.e., Arakoda and Krintafel) were approved by the Food and Drug Administration (FDA) for use in the United States. Arakoda was approved for use by adults for chemoprophylaxis; the regimen requires a predeparture loading dose, taking the medication weekly during travel, and a short course posttravel. The Arakoda chemoprophylaxis regimen is shorter than alternative regimens, which could possibly improve adherence. This medication also might prevent relapses. Krintafel was approved for radical cure of P. vivax infections in those aged >16 years and should be co-administered with chloroquine ( In April 2019, intravenous artesunate became the first-line medication for treatment of severe malaria in the United States. Artesunate was recently FDA approved but is not yet commercially available. The drug can be obtained from CDC under an investigational new drug protocol. Detailed recommendations for preventing malaria are available to the general public at the CDC website ( Health care providers should consult the CDC Guidelines for Treatment of Malaria in the United States and contact the CDC's Malaria Hotline for case management advice when needed. Malaria treatment recommendations are available online ( and from the Malaria Hotline (770-488-7788 or toll-free 855-856-4713). Persons submitting malaria case reports (care providers, laboratories, and state and local public health officials) should provide complete information because incomplete reporting compromises case investigations and efforts to prevent infections and examine trends in malaria cases. Molecular surveillance of antimalarial drug resistance markers ( enables CDC to track, guide treatment, and manage drug resistance in malaria parasites both domestically and internationally. More samples are needed to improve the completeness of antimalarial drug resistance analysis; therefore, CDC requests that blood specimens be submitted for any case of malaria diagnosed in the United States.
  11. BMC Infect Dis. 2021 Mar 17. 21(1): 265
      BACKGROUND: Increasing arbovirus infections have been a global burden in recent decades. Many countries have experienced the periodic emergence of arbovirus diseases. However, information on the prevalence of arboviruses is largely unknown or infrequently updated because of the lack of surveillance studies, especially in Africa.METHODS: A surveillance study was conducted in Gabon, Central Africa, on arboviruses, which are a major public health concern in Africa, including: West Nile virus (WNV), dengue virus (DENV), Zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), and Rift Valley fever virus (RVFV). Serological and molecular assays were performed to investigate past infection history and the current status of infection, using serum samples collected from healthy individuals and febrile patients, respectively.
    RESULTS: The overall seroprevalence during 2014-2017 was estimated to be 25.3% for WNV, 20.4% for DENV, 40.3% for ZIKV, 60.7% for YFV, 61.2% for CHIKV, and 14.3% for RVFV. No significant differences were found in the seroprevalence of any of the viruses between the male and female populations. However, a focus on the mean age in each arbovirus-seropositive individual showed a significantly younger age in WNV- and DENV-seropositive individuals than in CHIKV-seropositive individuals, indicating that WNV and DENV caused a relatively recent epidemic in the region, whereas CHIKV had actively circulated before. Of note, this indication was supported by the detection of both WNV and DENV genomes in serum samples collected from febrile patients after 2016.
    CONCLUSIONS: This study revealed the recent re-emergence of WNV and DENV in Gabon as well as the latest seroprevalence state of the major arboviruses, which indicated the different potential risks of virus infections and virus-specific circulation patterns. This information will be helpful for public health organizations and will enable a rapid response towards these arbovirus infections, thereby preventing future spread in the country.
    Keywords:  Africa; Arboviruses; Dengue virus; Gabon; Surveillance; West Nile virus
  12. Nat Commun. 2021 03 15. 12(1): 1671
      Zika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIKV between 2013 and 2017. To identify factors that could explain these differences in dynamics between closely related mosquito-borne flaviviruses, we jointly fit a transmission dynamic model to surveillance, serological and molecular data. We estimate that the observed dynamics of ZIKV were the result of two key factors: strong seasonal effects, which created an ecologically optimal time of year for outbreaks; and introduction of ZIKV after this optimal time, which allowed ZIKV transmission to persist over multiple seasons. The ability to jointly fit to multiple data sources could help identify a similar range of possible outbreak dynamics in other settings.
  13. BMC Public Health. 2021 Mar 16. 21(1): 509
      BACKGROUND: Recent arboviral disease outbreaks highlight the value a better understanding of the spread of disease-carrying mosquitoes across spatial-temporal scales can provide. Traditional surveillance tools are limited by jurisdictional boundaries, workforce constraints, logistics, and cost; factors that in low- and middle-income countries often conspire to undermine public health protection efforts. To overcome these, we undertake a pilot study designed to explore if citizen science provides a feasible strategy for arboviral vector surveillance in small developing Pacific island contexts.METHODS: We recruited, trained, and equipped community volunteers to trap and type mosquitos within their household settings, and to report count data to a central authority by short-message-service. Mosquito catches were independently assessed to measure participants' mosquito identification accuracy. Other data were collected to measure the frequency and stability of reporting, and volunteers' experiences.
    RESULTS: Participants collected data for 78.3% of the study period, and agreement between the volunteer citizen scientists' and the reviewing entomologist's mosquito identification was 94%. Opportunity to contribute to a project of social benefit, the chance to learn new skills, and the frequency of engagement with project staff were prime motivators for participation. Unstable electricity supply (required to run the trap's fan), insufficient personal finances (to buy electricity and phone credit), and inconvenience were identified as barriers to sustained participation.
    CONCLUSIONS: While there are challenges to address, our findings suggest that citizen science offers an opportunity to overcome the human resource constraints that conspire to limit health authorities' capacity to monitor arboviral vectors across populations. We note that the success of citizen science-based surveillance is dependent on the appropriate selection of equipment and participants, and the quality of engagement and support provided.
    Keywords:  Arboviral disease; Chikungunya; Citizen science; Community participation; Dengue; Pacific; Solomon Islands; Surveillance; Vector-borne disease; Zika
  14. Front Microbiol. 2021 ;12 625539
      Midgut microbiota can participate in the detoxification and metabolism processes in insects, but there are few reports on the relationship between midgut microbiota and insecticide resistance in mosquitoes. In this study, we performed metagenomic sequencing on a susceptible strain (SS), a field-collected Hainan strain (HN), and a deltamethrin-resistant strain (RR) of Culex pipiens quinquefasciatus to understand the diversity and functions of their midgut microbiota. The results revealed differences in midgut microbiota among the three strains of Cx. pipiens quinquefasciatus. At the phylum level, Proteobacteria was the most prominent, accounting for nearly 70% of their midgut microbes. At the genus level, Aeromonas made up the highest proportion. In addition, Aeromonas, Morganella, Elizabethkingia, Enterobacter, Cedecea, and Thorsellia showed significant differences between strains. At the species level, Bacillus cereus, Enterobacter cloacae complex sp. 4DZ3-17B2, Streptomyces sp. CNQ329, and some species of Pseudomonas and Wolbachia were more abundant in the two resistant strains. Principal component analysis (PCA) showed that the SS strain had significantly different metagenomic functions than the two deltamethrin-resistant strains (HN and RR strain). The HN and RR strains differed from the SS strain in more than 10 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The analysis of species abundance and functional diversity can provide directions for future studies.
    Keywords:  Culex pipiens quinquefasciatus; deltamethrin; gut microbiota; metagenomics; resistance
  15. Pathog Glob Health. 2021 Mar 18. 1-9
      Fifty years ago, Italy was declared a malaria-free country by the World Health Organization (WHO). In remembering this important anniversary, the authors of this paper describe the long journey that led to this goal. In the century following the unification of Italy, malaria was one of the main public health problems. At the end of the 19th century, malaria cases amounted to 2 million, with 15,000-20,000 deaths per year. This manuscript examines the state of public and social health in Italy from the end of the 19th century to the beginning of the 20th century, with particular regard to the government's measures for the prevention, prophylaxis and treatment of malaria. The authors describe the main findings of Italian malariologists during the period under review, from the identification of Plasmodium as a malaria pathogen and the recognition of the Anopheles mosquito as its vector. They also make some considerations regarding the current situation and the importation of malaria by travelers and migrants from countries where the disease is still endemic.
    Keywords:  Italian malariologists; Malaria; discoveries; history; imported; travelers
  16. Malar J. 2021 Mar 17. 20(1): 150
      BACKGROUND: Mosquito larval source management (LSM) is a key outdoor malaria vector control strategy in rural communities in sub-Saharan Africa. Knowledge of this strategy is important for optimal design and implementation of effective malaria control interventions in this region. This study assessed household knowledge, perceptions and practices of mosquito LSM methods (draining stagnant water, larviciding, clearing grass/bushes and clean environment).METHODS: A cross-sectional design was used whereby 479 households were selected using two-stage sampling in Mwanza district, Malawi. A household questionnaire was administered to an adult member of the house. Respondents were asked questions on knowledge, perceptions and practices of mosquito LSM methods. Multivariable logistic regression model was used to identify factors associated with high-level knowledge of mosquito LSM methods.
    RESULTS: Majority of the respondents (64.5%) had high-level knowledge of mosquito LSM methods. Specifically, 63.7% (200/314) had positive perceptions about draining stagnant water, whereas 95.3% (223/234) practiced clean environment for malaria control and 5.2% had knowledge about larviciding. Compared to respondents with primary education, those with secondary education were more likely, whereas those without education were less likely, to have high-level knowledge of mosquito LSM methods (AOR = 3.54, 95% CI 1.45-8.63 and AOR = 0.38, 95% CI 0.23-0.64, respectively). Compared to respondents engaged in crop farming, those engaged in mixed farming (including pastoralists) and the self-employed (including business persons) were more likely to have high-level knowledge of mosquito LSM methods (AOR = 6.95, 95% CI 3.39-14.23 and AOR = 3.61, 95% CI 1.47-8.86, respectively). Respondents living in mud-walled households were less likely to have high-knowledge of mosquito LSM methods than those living in brick-walled households (AOR = 0.50, 95% CI 0.30-0.86).
    CONCLUSIONS: A high-level knowledge of mosquito LSM methods was established. However, when designing and implementing this strategy, specific attention should be paid to the uneducated, crop farmers and those living in poor households.
    Keywords:  Knowledge; Larval source management; Perceptions; Practices
  17. Sci Rep. 2021 Mar 19. 11(1): 6421
      The correct identification of mosquito vectors is often hampered by the presence of morphologically indiscernible sibling species. The Maculipennis complex is one of these groups that include both malaria vectors of primary importance and species of low/negligible epidemiological relevance, of which distribution data in Italy are outdated. Our study was aimed at providing an updated distribution of Maculipennis complex in Northern Italy through the sampling and morphological/molecular identification of specimens from five regions. The most abundant species was Anopheles messeae (2032), followed by Anopheles maculipennis s.s. (418), Anopheles atroparvus (28) and Anopheles melanoon (13). Taking advantage of ITS2 barcoding, we were able to finely characterize tested mosquitoes, classifying all the Anopheles messeae specimens as Anopheles daciae, a taxon with debated rank to which we referred as species inquirenda (sp. inq.). The distribution of species was characterized by Ecological Niche Models (ENMs), fed by recorded points of presence. ENMs provided clues on the ecological preferences of the detected species, with An. daciae sp. inq. linked to stable breeding sites and An. maculipennis s.s. more associated to ephemeral breeding sites. We demonstrate that historical Anopheles malaria vectors are still present in Northern Italy.
  18. Geospat Health. 2021 Mar 12. 16(1):
      The transition from the control phase to elimination of malaria in China through the national malaria elimination programme has focussed attention on the need for improvement of the surveillance- response systems. It is now understood that routine passive surveillance is inadequate in the parasite elimination phase that requires supplementation by active surveillance in foci where cluster cases have occurred. This study aims to explore the spatial clusters and temporal trends of malaria cases by the multivariate auto-regressive state-space model (MARSS) along the border to Myanmar in southern China. Data for indigenous cases spanning the period from 2007 to 2010 were extracted from the China's Infectious Diseases Information Reporting Management System (IDIRMS). The best MARSS model indicated that malaria transmission in the study area during 36 months could be grouped into three clusters. The estimation of malaria transmission patterns showed a downward trend across all clusters. The proposed methodology used in this study offers a simple and rapid, yet effective way to categorize patterns of foci which provide assistance for active monitoring of malaria in the elimination phase.
  19. Sci Rep. 2021 Mar 19. 11(1): 6477
      The relationship between deforestation and malaria is a spatiotemporal process of variation in Plasmodium incidence in human-dominated Amazonian rural environments. The present study aimed to assess the underlying mechanisms of malarial exposure risk at a fine scale in 5-km2 sites across the Brazilian Amazon, using field-collected data with a longitudinal spatiotemporally structured approach. Anopheline mosquitoes were sampled from 80 sites to investigate the Plasmodium infection rate in mosquito communities and to estimate the malaria exposure risk in rural landscapes. The remaining amount of forest cover (accumulated deforestation) and the deforestation timeline were estimated in each site to represent the main parameters of both the frontier malaria hypothesis and an alternate scenario, the deforestation-malaria hypothesis, proposed herein. The maximum frequency of pathogenic sites occurred at the intermediate forest cover level (50% of accumulated deforestation) at two temporal deforestation peaks, e.g., 10 and 35 years after the beginning of the organization of a settlement. The incidence density of infected anophelines in sites where the original forest cover decreased by more than 50% in the first 25 years of settlement development was at least twice as high as the incidence density calculated for the other sites studied (adjusted incidence density ratio = 2.25; 95% CI, 1.38-3.68; p = 0.001). The results of this study support the frontier malaria as a unifying hypothesis for explaining malaria emergence and for designing specific control interventions in the Brazilian Amazon.
  20. Int J Biometeorol. 2021 Mar 18.
      Efforts have been made to quantify the spatio-temporal malaria transmission intensity over India using the dynamical malaria model, namely, Vector-borne Disease Community Model of International Centre for Theoretical Physics Trieste (VECTRI). The likely effect of climate change in the variability of malaria transmission intensity over different parts of India is also investigated. The Historical data and future projection scenarios of the rainfall and temperature derived from the Coupled Model Intercomparison Project Phase 5 (CMIP5) model output are used for this purpose. The Entomological Inoculation Rate (EIR) and Vector are taken as quantifiers of malaria transmission intensity. It is shown that the maximum number of malaria cases over India occur during the Sept-Oct months, whereas the minimum during the Feb-Apr months. The malaria transmission intensity as well as length of transmission season over India is likely to increase in the future climate as a result of global warming.
    Keywords:  CMIP5 models; Climate change; Entomological inoculation rate; Malaria transmission; VECTRI; Vector