bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2023–02–26
twelve papers selected by
Richard Halfpenny, Staffordshire University



  1. Trop Med Infect Dis. 2023 Jan 20. pii: 77. [Epub ahead of print]8(2):
      In Brazil, the mosquito Aedes (Stegomyia) aegypti is considered the main vector of the dengue, chikungunya, and Zika arbovirus transmission. Recent epidemiological studies in southern Brazil have shown an increase in the incidence of dengue, raising concerns over epidemiological control, monitoring, and surveys. Therefore, this study aimed at performing a historical spatiotemporal analysis of the Ae. aegypti house indices (HI) in southern Brazil over the last 19 years. As vector infestation was associated with climatic and environmental variables, HI data from the Brazilian Ministry of Health, climate data from the Giovanni web-based application, and environmental data from the Mapbiomas project were used in this study. Our results showed an expressive increase in the number of HI surveys in the municipalities confirming the vector presence, as compared to those in 2017. Environmental variables, such as urban infrastructure, precipitation, temperature, and humidity, were positively correlated with the Ae. aegypti HI. This was the first study to analyze Ae. aegypti HI surveys in municipalities of southern Brazil, and our findings could help in developing and planning disease control strategies to improve public health.
    Keywords:  arboviruses; climate; epidemiological control; house indices; mosquito; temperature
    DOI:  https://doi.org/10.3390/tropicalmed8020077
  2. GigaByte. 2022 ;2022 gigabyte53
      The Culicidae family has two of the most important disease vector genus: Aedes spp. and Culex spp. Both of these are involved in the transmission of arboviruses. Here, we provide novel data for the geographical distribution of 2,383 specimens in the Culicidae family. We also report the percentage of houses infested with these vectors, and Shannon and Simpson diversity indices in three municipalities located in Cauca, Colombia. This dataset is relevant for research on vector-borne diseases because Aedes spp. can transmit arboviruses such as dengue, Zika and chikungunya, and Culex spp. is a well-known vector of West Nile virus and Venezuelan equine encephalitis.
    DOI:  https://doi.org/10.46471/gigabyte.53
  3. Trop Med Infect Dis. 2023 Feb 20. pii: 130. [Epub ahead of print]8(2):
      Zika virus (ZIKV) shows an enigmatic epidemiological profile in Africa. Despite its frequent detection in mosquitoes, few human cases have been reported. This could be due to the low infectious potential or low virulence of African ZIKV lineages. This study sought to assess the susceptibility of A. aegypti and C. quinquefasciatus to ZIKV strains from Senegal, Brazil, and New Caledonia. Vertical transmission was also investigated. Whole bodies, legs/wings and saliva samples were tested for ZIKV by real-time PCR to estimate infection, dissemination and transmission rates as well as the infection rate in the progeny of infected female A. aegypti. For A. aegypti, the Senegalese strain showed at 15 days post-exposure (dpe) a significantly higher infection rate (52.43%) than the Brazilian (10%) and New Caledonian (0%) strains. The Brazilian and Senegalese strains were disseminated but not detected in saliva. No A. aegypti offspring from females infected with Senegalese and Brazilian ZIKV strains tested positive. No infection was recorded for C. quinquefasciatus. We observed the incompetence of Senegalese A. aegypti to transmit ZIKV and the C. quinquefasciatus were completely refractory. The effect of freezing ZIKV had no significant impact on the vector competence of Aedes aegypti from Senegal, and vertical transmission was not reported in this study.
    Keywords:  A. aegypti; Brazil; C. quinquefasciatus; New Caledonia; Senegal; Zika virus
    DOI:  https://doi.org/10.3390/tropicalmed8020130
  4. Infect Drug Resist. 2023 ;16 821-828
       Background: Regardless of various prevention and control strategies, malaria continues to be a significant public health problem in Ethiopia. As there are few studies on malaria trend analysis in Northeastern Ethiopia, it hinders the evaluation of ongoing and prioritization of new malaria intervention strategies, particularly during the period of pandemics. Therefore, the present study investigated the trend of malaria prevalence in Northeastern Ethiopia from 2015 to 2020.
    Methods: An institution-based retrospective study was employed to assess the trend of malaria prevalence over a 6-year period (2015-2020) in three districts (Jile tumuga, Aruma fursi, and Dawachefa) of Northeastern Ethiopia. Data were extracted from clinical records of malaria cases by trained medical laboratory technologists. The associations between the prevalence of malaria and independent variables (age group, malaria transmission season, and districts) were assessed using chi-square test. P-values with a cut-off point of 0.05 were used to determine statistically significant associations.
    Results: In our study area, a total of 212,952 malaria suspected patients were diagnosed over the 6 years. Of these, 33,005 (15.5%) were confirmed malaria cases. The identified Plasmodium species were Plasmodium falciparum and P. vivax, accounting for 66.4% and 33.6%, respectively. These with the age of >15 years old were the most affected (41.9%). The highest numbers of malaria cases (34.6%) were recorded during spring season (September to November). The prevalence of Plasmodium species showed a significant association with age (X2=9.7; p=0.002), districts (X2=13.5; p<0.001), and malaria transmission season (X2=16.5; p<0.001).
    Conclusion: In our study area, P. falciparum is the dominant species. We noted that malaria remains a public health concern and fluctuates throughout the years. Therefore, national, regional, zonal, and district health bureaus should strengthen the ongoing and devise appropriate prevention and control strategies even during the period of pandemics.
    Keywords:  Northeast Ethiopia; P. falciparum and P. vivax; malaria trend; season
    DOI:  https://doi.org/10.2147/IDR.S399834
  5. GigaByte. 2022 ;2022 gigabyte57
    Consortium AIM-COST/AIM-Surv
      Human and animal vector-borne diseases, particularly mosquito-borne diseases, are emerging or re-emerging worldwide. Six Aedes invasive mosquito (AIM) species were introduced to Europe since the 1970s: Aedes aegypti, Ae. albopictus, Ae. japonicus, Ae. koreicus, Ae. atropalpus and Ae. triseriatus. Here, we report the results of AIMSurv2020, the first pan-European surveillance effort for AIMs. Implemented by 42 volunteer teams from 24 countries. And presented in the form of a dataset named "AIMSurv Aedes Invasive Mosquito species harmonized surveillance in Europe. AIM-COST Action. Project ID: CA17108". AIMSurv2020 harmonizes field surveillance methodologies for sampling different AIMs life stages, frequency and minimum length of sampling period, and data reporting. Data include minimum requirements for sample types and recommended requirements for those teams with more resources. Data are published as a Darwin Core archive in the Global Biodiversity Information Facility- Spain, comprising a core file with 19,130 records (EventID) and an occurrences file with 19,743 records (OccurrenceID). AIM species recorded in AIMSurv2020 were Ae. albopictus, Ae. japonicus and Ae. koreicus, as well as native mosquito species.
    DOI:  https://doi.org/10.46471/gigabyte.57
  6. Sci Rep. 2023 Feb 20. 13(1): 2989
      Searching for new bioactive molecules to design insecticides is a complex process since pesticides should be highly selective, active against the vector, and bio-safe for humans. Aiming to find natural compounds for mosquito control, we evaluated the insecticidal activity of essential oils (EOs) from 20 American native plants against Aedes aegypti larvae using bioassay, biochemical, and in silico analyses. The highest larvicide activity was exhibited by EOs from Steiractinia aspera (LC50 = 42.4 µg/mL), Turnera diffusa (LC50 = 70.9 µg/mL), Piper aduncum (LC50 = 55.8 µg/mL), Lippia origanoides (chemotype thymol/carvacrol) (LC50 = 61.9 µg/mL), L. origanoides (chemotype carvacrol/thymol) (LC50 = 59.8 µg/mL), Hyptis dilatata (LC50 = 61.1 µg/mL), Elaphandra quinquenervis (LC50 = 61.1 µg/mL), and Calycolpus moritzianus (LC50 = 73.29 µg/mL) after 24 h. This biological activity may be related to the disruption of the electron transport chain through the mitochondrial protein complexes. We hypothesized that the observed EOs' effect is due to their major components, where computational approaches such as homology modeling and molecular docking may suggest the possible binding pose of secondary metabolites that inhibit the mitochondrial enzymes and acetylcholinesterase activity (AChE). Our results provided insights into the possible mechanism of action of EOs and their major compounds for new insecticide designs targeting the mitochondria and AChE activity in A. aegypti for effective and safe insecticide.
    DOI:  https://doi.org/10.1038/s41598-023-30046-8
  7. Am J Trop Med Hyg. 2023 Feb 20. pii: tpmd220569. [Epub ahead of print]
      This study aimed to evaluate at a temporospatial scale, the influence of anthropogenic land cover changes in the Anopheles species community composition and diversity in two Colombian malaria-endemic regions, Bajo Cauca and Pacific. To determine variations over time, mosquitoes were collected in two time periods; land cover types were characterized on orthorectified aerial photographs, and landscape metrics were estimated for each locality and period. A temporal dissimilarity analysis to evaluated species replacement and the nestedness species loss/gain showed the influence of the species loss or gain component on Anopheles species assemblage (23%). The relationship between land cover variation and Anopheles beta diversity, evaluated by regression analysis, showed the effect of forest variation in the Anopheles community (βsim and forest r2 = 0.9323; βsne and forest r2 = 0.9425). Furthermore, a canonical correspondence analysis showed that the land cover types associated with Anopheles species presence were bare soil, shrub, wet areas, and forest. Results demonstrated the impact of land cover changes attributed to human activities on Anopheles population dynamics, over time; this was evidenced as species loss or gain, which was specific to each locality. Notably, the main malaria vectors were dominant in most localities over time, suggesting their tolerance to anthropogenic transformations; alternatively, the environmental changes are providing adequate ecological conditions for their persistence. Finally, the data generated are relevant for understanding the impact that environmental change may have on the dynamics of the neotropical malaria vectors. Thus, this research has potential implications for vector control interventions.
    DOI:  https://doi.org/10.4269/ajtmh.22-0569
  8. Malar J. 2023 Feb 21. 22(1): 61
       BACKGROUND: Insecticide-treated nets (ITN) are the cornerstone of modern malaria vector control, with nearly 3 billion ITNs delivered to households in endemic areas since 2000. ITN access, i.e. availability within the household, based on the number of ITNs and number of household members, is a pre-requisite for ITN use. Factors determining ITN use are frequently examined in published literature, but to date, large household survey data on reasons given for non-use of nets have not been explored.
    METHODS: A total of 156 DHS, MIS, and MICS surveys conducted between 2003 and 2021 were reviewed for questions on reasons why nets were not used the previous night, identifying twenty-seven surveys. The percent of nets that were reported used the previous night was calculated for the 156 surveys, and frequencies and proportions of reasons for non-use were calculated within the twenty-seven surveys. Results were stratified by household supply of ITNs in three categories (not enough", "enough", and "more than enough") and by residence (urban/rural).
    RESULTS: The proportion of nets used the previous night averaged over 70% between 2003 and 2021, with no discernible change over this period. Reported reasons for why a net goes unused fell largely into three categories-nets that are extra/being saved for future use; the perception that there is little risk of malaria (particularly in dry season); and "other" responses. Net attributes such as colour, size, shape, and texture, and concerns related to chemicals were the least frequent reasons given. Reasons for non-use of nets varied by household net supply, and in some surveys by residence. In Senegal's continuous DHS, the proportion of nets used peaked during high transmission season, and the proportion of nets that went unused due to "no/few mosquitoes" peaked during the dry season.
    CONCLUSIONS: Unused nets were primarily those being saved for later use, or were not used due to perceived low risk of malaria. Classifying reasons for non-use into broader categories facilitates the design of appropriate social and behaviour change interventions to address the major underlying reasons for non-use, where this is feasible.
    DOI:  https://doi.org/10.1186/s12936-023-04490-w
  9. GigaByte. 2022 ;2022 gigabyte59
       'MEMO: Monitoring of Exotic MOsquitoes in Belgium' is a sampling event dataset published by the Institute of Tropical Medicine (ITM) in Antwerp, Belgium. It forms part of the early detection of exotic mosquito species (EMS) along high-risk introduction routes in Belgium, where data are collected at defined points of entry (PoEs) using a standardised protocol. The MEMO dataset contains mosquito sampling counts performed between 2017 and 2020. MEMO+2020, an extension of the MEMO dataset, contains only Aedes albopictus mosquito trap counts performed in 2020. Here, we present these data published as a standardised Darwin Core archive, which includes, for each sampling event, an eventID, date, location and sampling protocol (in the event core); and an occurrenceID for each occurrence (tube), the number of collected individuals per tube, species status (present/absent), information on the identification and scientific name (in the occurrence extension).
    DOI:  https://doi.org/10.46471/gigabyte.59
  10. Malar J. 2023 Feb 22. 22(1): 64
       BACKGROUND: Despite notable progress in the control and prevention of malaria in the Horn of Africa, the disease continues to cause significant morbidity and mortality in various regions of Ethiopia, and elsewhere in the region. The transmission of malaria is affected by genetic, sociocultural, and ecological factors. Lare is an Ethiopian district adjacent to the Ethio-South Sudan border, in Gambella region. The region currently has the highest prevalence of malaria in Ethiopia. This study assesses the burden and spatiotemporal patterns of disease transmission, including the effect of climatic factors on the occurrence of malaria, across an international border crossing. This understanding can assist in crafting informed programmatic and policy decisions for interventions.
    METHODS: This study was conducted in Lare district, Southwest Ethiopia, a temperate zone. A retrospective descriptive analysis was conducted using clinical service data collected between 2011 and 2021 from the 9 health facilities of the district. Both clinically diagnosed patients and those identified using microscopy and rapid diagnostic testing (RDT) were included in the study. Additionally, climate data was incorporated into analyses. Examples of analyses include malaria burden, positivity rate, incidence, species frequency, and an ANOVA to assess inter-annual case number and meteorological factor variation.
    RESULTS: Between 2011 and 2021, a total of 96,616 suspected malaria cases were tested by microscopy or RDT, and 39,428 (40.8%) of these cases were reported as positive. There were 1276 patients admitted with 22 deaths recorded. There were further more significant fluctuations in positivity rates across years, the highest being 74.5% in 2021. Incidence varied from 18.0% in 2011 to 151.6% in 2016. The malaria parasite species most detected was Plasmodium falciparum, followed by a smaller proportion of Plasmodium vivax. The greatest proportions of P. falciparum cases were observed in 2018 and 2019, at 97.4% and 97.0% prevalence, respectively. There was significant seasonal variation in case number, the highest observed in July through September of each year. Climatic conditions of annual rainfall, temperature and humidity favored the increment of malaria cases from June until October.
    CONCLUSION: The study shows that the burden, i.e. morbidity and mortality (with fluctuating patterns) of malaria are still significant public health problems and can pose serious consequences in the district. This has implication for cross-border malaria transmission risk due to considerable border crossings. The predominant cause of the disease is P. falciparum, which causes severe complications in patients. The district has to prepare to deal with such complications for better patient care and outcomes.
    Keywords:  Community health; Lare; Malaria; Rural health; South Sudan; Western Ethiopia
    DOI:  https://doi.org/10.1186/s12936-023-04479-5
  11. Rev Bras Epidemiol. 2023 ;pii: S1415-790X2023000100416. [Epub ahead of print]26 e230018
       OBJECTIVE: To identify the spatial patterns of chikungunya fever (CHIKF) and the associated socioeconomic, demographic, and vector infestation factors in the 1st Health Region of Pernambuco (1st HRP).
    METHODS: This ecological study used a spatial analysis of Mean Incidence Rates (MIR) of probable cases of CHIKF reported among residents of the 19 municipalities of the 1st HRP, in 2015-2021. The univariate and bivariate global Moran indexes (I) were estimated. From the significant associations (p<0.05), clusters were identified using the local Moran index and maps.
    RESULTS: A predominance of the largest CHIKF rates was identified in the east. However, there was a heterogeneous distribution of rates across municipalities, which may have contributed to the absence of spatial autocorrelation of CHIKF (I=0.03; p=0.294) in univariate I. The bivariate I revealed a positive spatial correlation between CHIKF and the Municipal Human Development Index (MHDI) (I=0.245; p=0.038), but with a cluster of cities with low incidences and low MHDI in the west. There was no spatial correlation between CHIKF and the other variables analyzed: population density, Gini index, social vulnerability index, and building infestation index for Aedes aegypti.
    CONCLUSIONS: The results suggest that only the MHDI influenced the occurrence of CHIKF in the 1st HRP, so that municipalities in the west demonstrated spatial dependence between lower values of MHDI and MIR. However, this spatial correlation may have occurred due to possible underreporting in the area. These findings can assist in the (re)orientation of resources for surveillance and health care services.
    DOI:  https://doi.org/10.1590/1980-549720230018
  12. Vector Borne Zoonotic Dis. 2023 Feb 24.
      Objective: Tribal malaria is well known for its substantial share in the overall malarial load of the country. This paper examines the levels and trends of malaria incidence and mortality in the tribal population for the past two decades. Methods: Data on malaria incidence and mortality were collected from an online e-repository that provides statistical data and information on 19 sectors, including health. Results: The analysis showed that the malaria incidence and mortality in tribal-dominated regions declined at an average annual rate of 4.3% per annum between 2000 and 2020, which accompanies the tremendous progress made in malaria control at the country level during this time period. The results also showed that between 2016 and 2020, the decline in tribal-dominated regions was consistent and noteworthy in terms of magnitude, a period that marks the implementation of the national framework for malaria elimination in the country. Conclusion: The decisive fall in the incidence and mortality of malaria in the tribal-dominated region has put India on track to achieve the target of 3.3 of the Sustainable Development Goals. However, with the pandemic impacting service delivery, monitoring, and reporting, including malaria control programs, it is important to maintain the momentum of progress in malaria control.
    Keywords:  India; incidence; malaria; malaria control and elimination; mortality; tribal population
    DOI:  https://doi.org/10.1089/vbz.2022.0083