bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022–01–30
nineteen papers selected by
Richard Halfpenny, Staffordshire University



  1. J Vector Borne Dis. 2021 Apr-Jun;58(2):58(2): 135-140
       BACKGROUND & OBJECTIVES: Infections caused by arboviruses and transmitted by Aedes species mosquitoes are a serious health concern. India is endemic for diseases like Dengue, Chikungunya and recently Zika has been reported from few states. Vector control is the only way to contain these diseases, however, data regarding vectors from central India is lacking; to fulfill the lacuna we conducted this study.
    METHODS: Entomological surveys were conducted from November 2017 to December 2018 for Aedes species in Dengue endemic areas of central India. The mosquitoes were identified, pooled and tested for the presence of Dengue, Chikungunya and Zika viruses by RT-PCR. The PCR products were sequenced to identify serotypes and genotypes of viruses.
    RESULTS: A total of 2991 adults of Aedes specimens were collected and tested. Ae. aegypti (94.6%) was found to be the most abundant species. Highest mosquito density was recorded in the monsoon periods. Dengue (n=5) and Chikungunya (n=4) virus were detected from pools of female Ae. aegypti. One pool of male Ae. aegypti was positive for Dengue virus-3 and Chikungunya virus. Zika virus was not detected from any pool.
    INTERPRETATION & CONCLUSION: The findings suggest that Ae. aegypti is the principal vector of Dengue and Chikungunya, which is capable to transmit these viruses vertically. The findings have epidemiological importance and will be helpful to program managers.
    Keywords:  Aedes; Chikungunya; Dengue; Zika; vertical transmission
    DOI:  https://doi.org/10.4103/0972-9062.321753
  2. Parasit Vectors. 2022 Jan 24. 15(1): 36
       BACKGROUND: Aedes albopictus and Aedes japonicus, two invasive mosquito species in the United States, are implicated in the transmission of arboviruses. Studies have shown interactions of these two mosquito species with a variety of vertebrate hosts; however, regional differences exist and may influence their contribution to arbovirus transmission.
    METHODS: We investigated the distribution, abundance, host interactions, and West Nile virus infection prevalence of Ae. albopictus and Ae. japonicus by examining Pennsylvania mosquito and arbovirus surveillance data for the period between 2010 and 2018. Mosquitoes were primarily collected using gravid traps and BG-Sentinel traps, and sources of blood meals were determined by analyzing mitochondrial cytochrome b gene sequences amplified in PCR assays.
    RESULTS: A total of 10,878,727 female mosquitoes representing 51 species were collected in Pennsylvania over the 9-year study period, with Ae. albopictus and Ae. japonicus representing 4.06% and 3.02% of all collected mosquitoes, respectively. Aedes albopictus was distributed in 39 counties and Ae. japonicus in all 67 counties, and the abundance of these species increased between 2010 and 2018. Models suggested an increase in the spatial extent of Ae. albopictus during the study period, while that of Ae. japonicus remained unchanged. We found a differential association between the abundance of the two mosquito species and environmental conditions, percent development, and median household income. Of 110 Ae. albopictus and 97 Ae. japonicus blood meals successfully identified to species level, 98% and 100% were derived from mammalian hosts, respectively. Among 12 mammalian species, domestic cats, humans, and white-tailed deer served as the most frequent hosts for the two mosquito species. A limited number of Ae. albopictus acquired blood meals from avian hosts solely or in mixed blood meals. West Nile virus was detected in 31 pools (n = 3582 total number of pools) of Ae. albopictus and 12 pools (n = 977 total pools) of Ae. japonicus.
    CONCLUSIONS: Extensive distribution, high abundance, and frequent interactions with mammalian hosts suggest potential involvement of Ae. albopictus and Ae. japonicus in the transmission of human arboviruses including Cache Valley, Jamestown Canyon, La Crosse, dengue, chikungunya, and Zika should any of these viruses become prevalent in Pennsylvania. Limited interaction with avian hosts suggests that Ae. albopictus might occasionally be involved in transmission of arboviruses such as West Nile in the region.
    DOI:  https://doi.org/10.1186/s13071-022-05151-8
  3. Infect Genet Evol. 2022 Jan 24. pii: S1567-1348(22)00023-5. [Epub ahead of print] 105226
      We conducted mosquito-based Zika virus surveillance in São Paulo State, Brazil from 2015 to 2018. We found 81 pools positive for Aedes aegypti and one pool positive for Aedes albopictus. Infection rates were highest in the summer. Areas with human Zika cases also had clusters of Zika-positive mosquitoes.
    Keywords:  Epidemiology; Mosquito; Surveillance; Virus
    DOI:  https://doi.org/10.1016/j.meegid.2022.105226
  4. J Vector Borne Dis. 2021 Apr-Jun;58(2):58(2): 119-125
       BACKGROUND & OBJECTIVES: Dakshina Kannada is one of the districts of Karnataka state of India with high incidences of mosquito-borne diseases, especially malaria and dengue. The larval stages of the mosquitoes are very important in determining the prevalence of adult mosquitoes and associated diseases. Hence, the occurrence of mosquito species was investigated by sampling different water bodies present in the Dakshina Kannada district from June 2014 to May 2017.
    METHODS: Random sampling was carried out from permanent and temporary, artificial and natural water bodies belonging to 11 types of microhabitats using dippers and suction pumps.
    RESULTS: A maximum of 37 mosquito species belonging to 12 genera were recorded with the dominant genera being Culex. Most species have been recorded from temporary bodies of water with the highest number of species in receptacles. Monsoon is the most productive season, both in terms of occurrence and abundance followed by post-monsoon and pre-monsoon. The abundance of mosquito larvae was significantly higher in temporary water bodies compared to the permanent.
    INTERPRETATION & CONCLUSION: Abundant rainfall in the study area which produces many natural and domestic temporary water bodies accounts for mosquito breeding throughout the year.
    Keywords:  Mosquito; diversity; habitats; season
    DOI:  https://doi.org/10.4103/0972-9062.321758
  5. PLoS Negl Trop Dis. 2022 Jan;16(1): e0010028
      Cambodia has one of the highest dengue infection rates in Southeast Asia. Here we report quantitative entomological results of a large-scale cluster-randomised trial assessing the impact on vector populations of a package of vector control interventions including larvivorous guppy fish in household water containers, mosquito trapping with gravid-ovitraps, solid waste management, breeding-container coverage through community education and engagement for behavioural change, particularly through the participation of school children. These activities resulted in major reductions in Container Index, House Index, Breteau Index, Pupal Index and Adult Index (all p-values 0.002 or lower) in the Intervention Arm compared with the Control Arm in a series of household surveys conducted over a follow-up period of more than one year, although the project was not able to measure the longer-term sustainability of the interventions. Despite comparative reductions in Adult Index between the study arms, the Adult Index was higher in the Intervention Arm in the final household survey than in the first household survey. This package of biophysical and community engagement interventions was highly effective in reducing entomological indices for dengue compared with the control group, but caution is required in extrapolating the reduction in household Adult Index to a reduction in the overall population of adult Aedes mosquitoes, and in interpreting the relationship between a reduction in entomological indices and a reduction in the number of dengue cases. The package of interventions should be trialled in other locations.
    DOI:  https://doi.org/10.1371/journal.pntd.0010028
  6. PLoS One. 2022 ;17(1): e0249440
      Long lasting insecticidal nets (LLINs) are a proven tool to reduce malaria transmission, but in Africa efficacy is being reduced by pyrethroid resistance in the major vectors. A previous study that was conducted in Muleba district, Tanzania indicated possible involvement of cytochrome P450 monooxygenases in a pyrethroid resistance in An. gambiae population where pre-exposure to piperonyl butoxide (PBO) followed by permethrin exposure in CDC bottle bioassays led to partial restoration of susceptibility. PBO is a synergist that can block pyrethroid-metabolizing enzymes in a mosquito. Insecticide resistance profiles and underlying mechanisms were investigated in Anopheles gambiae and An. funestus from Muleba during a cluster randomized trial. Diagnostic dose bioassays using permethrin, together with intensity assays, suggest pyrethroid resistance that is both strong and very common, but not extreme. Transcriptomic analysis found multiple P450 genes over expressed including CYP6M2, CYP6Z3, CYP6P3, CYP6P4, CYP6AA1 and CYP9K1 in An. gambiae and CYP6N1, CYP6M7, CYP6M1 and CYP6Z1 in An. funestus. Indeed, very similar suites of P450 enzymes commonly associated with resistant populations elsewhere in Africa were detected as over expressed suggesting a convergence of mechanisms across Sub-Saharan African malaria vectors. The findings give insight into factors that may correlate with pyrethroid PBO LLIN success, broadly supporting model predictions, but revision to guidelines previously issued by the World Health Organization is warranted.
    DOI:  https://doi.org/10.1371/journal.pone.0249440
  7. PLoS Negl Trop Dis. 2022 Jan 24. 16(1): e0010071
      The dengue virus affects millions of people every year worldwide, causing large epidemic outbreaks that disrupt people's lives and severely strain healthcare systems. In the absence of a reliable vaccine against dengue or an effective treatment to manage the illness in humans, most efforts to combat dengue infections have focused on preventing its vectors, mainly the Aedes aegypti mosquito, from flourishing across the world. These mosquito-control strategies need reliable disease activity surveillance systems to be deployed. Despite significant efforts to estimate dengue incidence using a variety of data sources and methods, little work has been done to understand the relative contribution of the different data sources to improved prediction. Additionally, scholarship on the topic had initially focused on prediction systems at the national- and state-levels, and much remains to be done at the finer spatial resolutions at which health policy interventions often occur. We develop a methodological framework to assess and compare dengue incidence estimates at the city level, and evaluate the performance of a collection of models on 20 different cities in Brazil. The data sources we use towards this end are weekly incidence counts from prior years (seasonal autoregressive terms), weekly-aggregated weather variables, and real-time internet search data. We find that both random forest-based models and LASSO regression-based models effectively leverage these multiple data sources to produce accurate predictions, and that while the performance between them is comparable on average, the former method produces fewer extreme outliers, and can thus be considered more robust. For real-time predictions that assume long delays (6-8 weeks) in the availability of epidemiological data, we find that real-time internet search data are the strongest predictors of dengue incidence, whereas for predictions that assume short delays (1-3 weeks), in which the error rate is halved (as measured by relative RMSE), short-term and seasonal autocorrelation are the dominant predictors. Despite the difficulties inherent to city-level prediction, our framework achieves meaningful and actionable estimates across cities with different demographic, geographic and epidemic characteristics.
    DOI:  https://doi.org/10.1371/journal.pntd.0010071
  8. J Vector Borne Dis. 2021 Apr-Jun;58(2):58(2): 99-105
       BACKGROUND & OBJECTIVES: This study aimed to review the effectiveness of lactic acid when combined with other types of attractants for Aedes spp.
    METHODS: A systematic review was conducted according to the protocol for a systematic review and meta-analysis (PRISMA). Literature search used Cinahl, Medline/PubMed, ScienceDirect, ProQuest and Ebsco electronic databases. Research articles used in the systematic review were experimental articles that reported the effectiveness of mosquito traps using lactic acid or a combination of lactic acid with other attractants.
    RESULTS: From a total of 42 articles reviewed, there were 6 articles fulfilling the inclusion criteria. The highest synergistic combination of lactic acid in the ketone group was shown in the acetone compound, in the sulfides class, dimethyl sulfides, and in the chloroalkanes group, chloroform. The combination of lactic acid with two effective attractants can be seen in the incorporation of ammonia + caproic acid, and for the incorporation of lactic acid with three other effective attractants illustrated by combining ammonia + caproic acid + CO2.
    INTERPRETATION & CONCLUSION: Lactic acid as an attractant can be combined with other various compounds (ketone compounds, sulfides and chloroalkanes). Lactic acid increases its effectiveness in trapping Ae. aegypti and/or Ae. albopictus if combined with acetone, dimethyl sulfides, and/or chloroform.
    Keywords:  Aedes; Attractant; Lactic Acid; spp
    DOI:  https://doi.org/10.4103/0972-9062.316276
  9. PLoS Negl Trop Dis. 2022 Jan 24. 16(1): e0010171
      Aedes simpsoni complex has a wide distribution in Africa and comprises at least three described sub-species including the yellow fever virus (YFV) vector Ae. bromeliae. To date, the distribution and relative contributions of the sub-species and/or subpopulations including bionomic characteristics in relation to YF transmission dynamics remain poorly studied. In this study conducted in two areas with divergent ecosystems: peri-urban (coastal Rabai) and rural (Rift Valley Kerio Valley) in Kenya, survival rate was estimated by parity in Ae. simpsoni s.l. mosquitoes sampled using CO2-baited BG Sentinel traps. We then applied PCR targeting the nuclear internal transcribed spacer 2 (ITS2), region followed by sequencing and phylogenetic analytics to identify the sibling species in the Ae. simpsoni complex among parous and blood fed cohorts. Our results show that Ae. bromeliae was the most dominant sub-species in both areas, exhibiting high survival rates, human blood-feeding, and potentially, high vectorial capacity for pathogen transmission. We document for the first time the presence of Ae. lilii in Kenya and potentially yet-to-be described species in the complex displaying human feeding tendencies. We also infer a wide host feeding range on rodents, reptile, and domestic livestock besides humans especially for Ae. bromeliae. This feeding trend could likely expose humans to various zoonotic pathogens. Taken together, we highlight the utility of genotype-based analyses to generate precision surveillance data of vector populations for enhanced disease risk prediction and to guide cost-effective interventions (e.g. YF vaccinations).
    DOI:  https://doi.org/10.1371/journal.pntd.0010171
  10. Emerg Infect Dis. 2022 Feb;28(2): 425-428
      Mosquito control is essential to reduce vectorborne disease risk. We surveyed residents in Harris, Tarrant, and Hidalgo Counties, Texas, USA, to estimate willingness-to-pay for mosquito control and acceptance of control methods. Results show an unmet demand for expanded mosquito control that could be funded through local taxes or fees.
    Keywords:  Banacos N; Carbajal E; Dacko N; Fredregill C; Hinojosa S; Suggested citation for this article: Dickinson KL; Texas; USA. Emerg Infect Dis. 2022 Feb [date cited]. https://doi.org/10.3201/eid2802.210501; United States; et al. Public acceptance of and willingness to pay for mosquito control; meningitis/encephalitis; mosquito control; mosquito-borne; public opinion; questionnaire; vector-borne infections; viruses
    DOI:  https://doi.org/10.3201/eid2802.210501
  11. Appl Biochem Biotechnol. 2022 Jan 26.
      Warm and humid climate creates ideal conditions for mosquito breeding. The ability of these vectors to spread a number of diseases to humans causes millions of deaths every year. Indiscriminate use of synthetic insecticides leads to the development of resistance in vector mosquitoes and along with this, these pesticides cause biological magnification of toxic components and affects adversely the non-target organisms including human being. Commercially available, chemically manufactured mosquito repellent fast cards are convenient to use and quite effective but burning of such card generates a lot of smoke and might be hazardous to human health in the long run. Thus, alternative approaches are to be adopted to control the population load of vector mosquito. Like that, the present study also reveals the larvicidal effect of Duranta leaf extract against Culex mosquito. In the present study, mosquito repellent fast card has been developed by Duranta-algal mixture which has shown better result than commercially available fast card on the basis of mosquito mortality as well as the amount of gases emitted. Again, the ethanolic crude extract of Duranta leaves leads to 100% mortality of all instars (Culex pipiens) larvae at both 1000 ppm and 500 ppm concentration. Therefore, the active component of Duranta has also been investigated. In Duranta, highest area percentage and peak have been shown by propionic acid in the retention time 18.086 by GC-MS. So, it can be confirmed that the major active ingredient is propionic acid in Duranta which is responsible for the mosquitocidal properties. Occurrence of propionic acid in Duranta has also been confirmed by the HPLC analysis.
    Keywords:  Active compound; Culex sp.; Duranta repens; Fast card; Green algae; Larvicide; Plant extract
    DOI:  https://doi.org/10.1007/s12010-022-03798-8
  12. Emerg Infect Dis. 2022 Feb;28(2): 303-313
      Cache Valley virus (CVV) is a mosquitoborne virus that infects livestock and humans. We report results of surveillance for CVV in New York, USA, during 2000-2016; full-genome analysis of selected CVV isolates from sheep, horse, humans, and mosquitoes from New York and Canada; and phenotypic characterization of selected strains. We calculated infection rates by using the maximum-likelihood estimation method by year, region, month, and mosquito species. The highest maximum-likelihood estimations were for Anopheles spp. mosquitoes. Our phylogenetic analysis identified 2 lineages and found evidence of segment reassortment. Furthermore, our data suggest displacement of CVV lineage 1 by lineage 2 in New York and Canada. Finally, we showed increased vector competence of An. quadrimaculatus mosquitoes for lineage 2 strains of CVV compared with lineage 1 strains.
    Keywords:  Anopheles punctipennis; Anopheles quadrimaculatus; Cache Valley virus; New York; United States; lineage displacement; mosquitoes; surveillance; vector competence; vector-borne infections; viruses; zoonoses
    DOI:  https://doi.org/10.3201/eid2802.203810
  13. Lancet Planet Health. 2022 Jan 20. pii: S2542-5196(21)00296-5. [Epub ahead of print]
       BACKGROUND: Concern that insecticide resistant mosquitoes are threatening malaria control has driven the development of new types of insecticide treated nets (ITNs) and indoor residual spraying (IRS) of insecticide. Malaria control programmes have a choice of vector control interventions although it is unclear which controls should be used to combat the disease. The study aimed at producing a framework to easily compare the public health impact and cost-effectiveness of different malaria prevention measures currently in widespread use.
    METHODS: We used published data from experimental hut trials conducted across Africa to characterise the entomological effect of pyrethroid-only ITNs versus ITNs combining a pyrethroid insecticide with the synergist piperonyl butoxide (PBO). We use these estimates to parameterise a dynamic mathematical model of Plasmodium falciparum malaria which is validated for two sites by comparing simulated results to empirical data from randomised control trials (RCTs) in Tanzania and Uganda. We extrapolated model simulations for a series of potential scenarios likely across the sub-Saharan African region and include results in an online tool (Malaria INtervention Tool [MINT]) that aims to identify optimum vector control intervention packages for scenarios with varying budget, price, entomological and epidemiological factors.
    FINDINGS: Our model indicates that switching from pyrethroid-only to pyrethroid-PBO ITNs could averted up to twice as many cases, although the additional benefit is highly variable and depends on the setting conditions. We project that annual delivery of long-lasting, non-pyrethroid IRS would prevent substantially more cases over 3-years, while pyrethroid-PBO ITNs tend to be the most cost-effective intervention per case averted. The model was able to predict prevalence and efficacy against prevalence in both RCTs for the intervention types tested. MINT is applicable to regions of sub-Saharan Africa with endemic malaria and provides users with a method of designing intervention packages given their setting and budget.
    INTERPRETATION: The most cost-effective vector control package will vary locally. Models able to recreate results of RCTs can be used to extrapolate outcomes elsewhere to support evidence-based decision making for investment in vector control.
    FUNDING: Medical Research Council, IVCC, Wellcome Trust.
    TRANSLATION: For the French translation of the abstract see Supplementary Materials section.
    DOI:  https://doi.org/10.1016/S2542-5196(21)00296-5
  14. Trop Med Health. 2022 Jan 25. 50(1): 11
      Dengue fever is a viral infection caused by Aedes mosquitoes that has recently expanded fast in many of the WHO member states globally. Female mosquitoes, mostly Aedes aegypti and, to a smaller degree, Aedes albopictus, disseminate dengue virus. Dengue fever has been more common in recent decades all across the world, and Bangladesh is no exception. As the COVID-19 outbreak wreaks havoc, the following rise in dengue illnesses has been a source of considerable concern. As the health care has been stretched thin in these dangerous times, the vulnerable population has been left at the mercy of these two viral infections. Lack of knowledge, major legislative changes, poor eradication initiatives, and a lack of financing resources have all contributed to the increase in numbers. Stakeholders and policymakers must begin taking meaningful actions and implementing well-thought-out adjustments immediately, or the situation will worsen, resulting in the loss of thousands of innocent lives.
    Keywords:  Bangladesh; COVID-19; Challenges; Dengue fever; Public health
    DOI:  https://doi.org/10.1186/s41182-022-00401-y
  15. Emerg Infect Dis. 2022 Feb;28(2): 475-477
      A new Getah virus (GETV) strain, B254, was isolated from Culex fuscocephalus mosquitoes captured at Mount Ophir, Malaysia, in 2012. Phylogenetic analyses revealed that GETV B254 is distinct from the old Malaysia GETV MM2021 strain but closely related to group IV GETV from Russia (LEIV16275Mag), China (YN12031), and Thailand (GETV/SW/Thailand/2017).
    Keywords:  Getah virus; Malaysia; alphavirus; arbovirus; emerging; evolution; infectious diseases; mosquitoes; tropical; vector-borne infections; viruses
    DOI:  https://doi.org/10.3201/eid2802.204887
  16. Nat Commun. 2022 Jan 27. 13(1): 533
      The rapid pace of urbanization makes it imperative that we better understand the influence of climate forcing on urban malaria transmission. Despite extensive study of temperature effects in vector-borne infections in general, consideration of relative humidity remains limited. With process-based dynamical models informed by almost two decades of monthly surveillance data, we address the role of relative humidity in the interannual variability of epidemic malaria in two semi-arid cities of India. We show a strong and significant effect of humidity during the pre-transmission season on malaria burden in coastal Surat and more arid inland Ahmedabad. Simulations of the climate-driven transmission model with the MLE (Maximum Likelihood Estimates) of the parameters retrospectively capture the observed variability of disease incidence, and also prospectively predict that of 'out-of-fit' cases in more recent years, with high accuracy. Our findings indicate that relative humidity is a critical factor in the spread of urban malaria and potentially other vector-borne epidemics, and that climate change and lack of hydrological planning in cities might jeopardize malaria elimination efforts.
    DOI:  https://doi.org/10.1038/s41467-022-28145-7
  17. Sci Total Environ. 2022 Jan 21. pii: S0048-9697(22)00423-5. [Epub ahead of print] 153331
      Many studies have explored the effects of plastic particles on aquatic organisms. To date, however, few studies have reported on the effects of plastic particles on terrestrial invertebrates. Here, Culex quinquefasciatus (southern house mosquito, prey) and Pardosa pseudoannulata (wolf spider, predator) were used to explore the transmission of nanoplastics (NPs) from aquatic to terrestrial invertebrates and to verify the effects of NPs in prey on predators. Mosquito larvae were exposed to 0, 200, and 1000 NPs mL-1 polystyrene, respectively, and then fed to spiders when they matured. Results showed that ingestion of NP-exposed mosquitoes affected the growth, development, and behavior of P. pseudoannulata, and the intestinal tissue structure, intestinal flora composition, and related enzymatic activities were also impacted. These results indicate that after spiders ingested NP-exposed mosquitoes, their growth, development, and predation ability were affected. This may prolong time to maturation and decrease the ability of spiders to survive and reproduce in the environment. Thus, plastic particles likely have a wide range of effects on organisms as well as the whole ecosystem.
    Keywords:  Aquatic to terrestrial; Culex quinquefasciatus; Nanoplastics; Pardosa pseudoannulata; Polystyrene; Transmission
    DOI:  https://doi.org/10.1016/j.scitotenv.2022.153331
  18. Infect Dis Poverty. 2022 Jan 24. 11(1): 12
       BACKGROUND: Overseas imported dengue fever is an important factor in local outbreaks of this disease in the mainland of China. To better prevent and control such local outbreaks, the epidemiological characteristics and temporal-spatial distribution of overseas imported dengue fever cases in provincial-level administrative divisions (PLADs) where dengue fever is outbreak in the mainland of China were explored.
    METHODS: Using the Chinese National Notifiable Infectious Disease Reporting Information System (CNNDS), we identified overseas imported dengue fever cases in dengue fever outbreak areas in the mainland of China from 2005 to 2019 to draw the epidemic curve and population characteristic distribution of overseas imported cases in each PLAD. Based on spatial autocorrelation analysis of ArcGIS 10.5 and temporal-spatial scanning analysis of SaTScan 9.5, we analyzed the temporal-spatial distribution of overseas imported dengue fever in dengue fever outbreak areas in the mainland of China.
    RESULTS: A total of 11,407 imported cases, mainly from Southeast Asia, were recorded from 2005 to 2019 in these 13 PLADs. Of which 62.1% were imported into Yunnan and Guangdong Provinces. Among the imported cases, there were more males than females, mainly from the 21-50 age group. The hot spots were concentrated in parts of Yunnan, Guangdong and Fujian Provinces. We found the cluster of infected areas were expanding northward.
    CONCLUSIONS: Based on the analysis of overseas imported dengue cases in 13 PLADs of the mainland of China from 2005 to 2019, we obtained the epidemiological characteristics and spatial distribution of imported dengue cases. Border controls need to pay attention to key population sectors, such as 21-50 years old men and education of key populations on dengue prevention. There is a need to improve the awareness of the prevention and control of imported cases in border areas. At the same time, northern regions cannot relax their vigilance.
    Keywords:  China; Dengue fever; Epidemiology; Imported case; Temporal-spatial distribution
    DOI:  https://doi.org/10.1186/s40249-022-00937-5
  19. Sci Rep. 2022 Jan 26. 12(1): 1411
      Globally, malaria is the major public health disease caused by plasmodium species and transmitted by the bite of the female anopheles mosquito. Assessment of the trend of malaria prevalence is important in the control and prevention of the disease. Therefore, the objective of this study was to assess the six year trend of malaria prevalence at the University of Gondar Comprehensive Specialized Hospital, northwest Ethiopia, from 2014 to 2019. A retrospective laboratory registration logbook review study was conducted on the malaria blood film examination results at the University of Gondar Comprehensive Specialized Hospital. The data was collected by using a data extraction tool and entered into SPSS version 20 for analysis. Descriptive statistics were used to summarize the socio-demographic characteristics of study participants and presented by graphs, tables and texts. The binary logistic regression was also used to test the association the trend of malaria prevalence and different factors like sex, age, year, and season. From a total of 17,500 malaria blood film examinations, 1341 (7.7%) were confirmed for malaria parasites. Of the confirmed malaria cases, 47.2%, 45.6% and 7.2% were P. vivax, P. falciparum and mixed infection, respectively. The proportion of P. vivax was the predominant species in the first three study years (2014-2016) and P. falciparum became the predominant species in the last three study years (2017-2019). The odds of malaria prevalence was lower by 68%, 60% and 69% in the year 2017, 2018 and 2019 compared to 2014, respectively. It was also 1.41 times higher in males than in females. Moreover, the odds of malaria prevalence were 1.60, 1.64, 2.45 and 1.82 times higher in the age group of < 5, 5-14, 15-24 and 25-54 years old compared to the older age groups (> 54 years old), respectively. Even there was a significant declining in prevalence trend; malaria is still a major public health problem. The study showed that there was high seasonal fluctuation from year to year. Moreover, males and the younger age groups were more affected than females and old age groups, respectively. Therefore, malaria prevention and control activities should be strengthened and require extra efforts by considering these variability.
    DOI:  https://doi.org/10.1038/s41598-022-05530-2