bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒12‒20
seventeen papers selected by
Richard Halfpenny
Staffordshire University


  1. Parasit Vectors. 2020 Dec 14. 13(1): 622
    Al-Amin HM, Johora FT, Irish SR, Hossainey MRH, Vizcaino L, Paul KK, Khan WA, Haque R, Alam MS, Lenhart A.
      BACKGROUND: Arboviral diseases, including dengue and chikungunya, are major public health concerns in Bangladesh where there have been unprecedented levels of transmission reported in recent years. The primary approach to control these diseases is to control the vector Aedes aegypti using pyrethroid insecticides. Although chemical control has long been practiced, no comprehensive analysis of Ae. aegypti susceptibility to insecticides has been conducted to date. The aim of this study was to determine the insecticide resistance status of Ae. aegypti in Bangladesh and investigate the role of detoxification enzymes and altered target site sensitivity as resistance mechanisms.METHODS: Eggs of Aedes mosquitoes were collected using ovitraps from five districts across Bangladesh and in eight neighborhoods of the capital city Dhaka, from August to November 2017. CDC bottle bioassays were conducted for permethrin, deltamethrin, malathion, and bendiocarb using 3- to 5-day-old F0-F2 non-blood-fed female mosquitoes. Biochemical assays were conducted to detect metabolic resistance mechanisms, and real-time PCR was performed to determine the frequencies of the knockdown resistance (kdr) mutations Gly1016, Cys1534, and Leu410.
    RESULTS: High levels of resistance to permethrin were detected in all Ae. aegypti populations, with mortality ranging from 0 to 14.8% at the diagnostic dose. Substantial resistance continued to be detected against higher (2×) doses of permethrin (5.1-44.4% mortality). Susceptibility to deltamethrin and malathion varied between populations while complete susceptibility to bendiocarb was observed in all populations. Significantly higher levels of esterase and oxidase activity were detected in most of the test populations as compared to the susceptible reference Rockefeller strain. A significant association was detected between permethrin resistance and the presence of Gly1016 and Cys1534 homozygotes. The frequency of kdr (knockdown resistance) alleles varied across the Dhaka Aedes populations. Leu410 was not detected in any of the tested populations.
    CONCLUSIONS: The detection of widespread pyrethroid resistance and multiple resistance mechanisms highlights the urgency for implementing alternate Ae. aegypti control strategies. In addition, implementing routine monitoring of insecticide resistance in Ae. aegypti in Bangladesh will lead to a greater understanding of susceptibility trends over space and time, thereby enabling the development of improved control strategies.
    Keywords:  Aedes aegypti; Bangladesh; Bioassays; Esterase; Insecticide resistance; Kdr; Mortality; Oxidase
    DOI:  https://doi.org/10.1186/s13071-020-04503-6
  2. PLoS Negl Trop Dis. 2020 Dec 18. 14(12): e0008971
    O'Leary S, Adelman ZN.
      Aedes aegypti is a vector of dengue, chikungunya, and Zika viruses. Current vector control strategies such as community engagement, source reduction, and insecticides have not been sufficient to prevent viral outbreaks. Thus, interest in novel strategies involving genetic engineering is growing. Female mosquitoes rely on flight to mate with males and obtain a bloodmeal from a host. We hypothesized that knockout of genes specifically expressed in female mosquitoes associated with the indirect flight muscles would result in a flightless female mosquito. Using CRISPR-Cas9 we generated loss-of-function mutations in several genes hypothesized to control flight in mosquitoes, including actin (AeAct-4) and myosin (myo-fem) genes expressed specifically in the female flight muscle. Genetic knockout of these genes resulted in 100% flightless females, with homozygous males able to fly, mate, and produce offspring, albeit at a reduced rate when compared to wild type males. Interestingly, we found that while AeAct-4 was haplosufficient, with most heterozygous individuals capable of flight, this was not the case for myo-fem, where about half of individuals carrying only one intact copy could not fly. These findings lay the groundwork for developing novel mechanisms of controlling Ae. aegypti populations, and our results suggest that this mechanism could be applicable to other vector species of mosquito.
    DOI:  https://doi.org/10.1371/journal.pntd.0008971
  3. Infect Genet Evol. 2020 Dec 13. pii: S1567-1348(20)30511-6. [Epub ahead of print] 104680
    Edgerton SV, Thongsripong P, Wang C, Montaya M, Balmaseda A, Harris E, Bennett SN.
      Arthropod-borne viruses (arboviruses) comprise a significant and ongoing threat to human health, infecting hundreds of millions annually. Three such arboviruses include circumtropical dengue, Zika, and chikungunya viruses, exhibiting continuous emergence primarily via Aedes mosquito vectors. Nicaragua has experienced endemic dengue virus (DENV) transmission involving multiple serotypes since 1985, with chikungunya virus (CHIKV) reported in 2014-2015, followed by Zika virus (ZIKV) first reported in 2016. In order to identify patterns of genetic variation and selection pressures shaping the evolution of co-circulating DENV serotypes in light of the arrival of CHIKV and ZIKV, we employed whole-genome sequencing on an Illumina MiSeq platform of random-amplified total RNA libraries to characterize 42 DENV low-passage isolates, derived from viremic patients in Nicaragua between 2013 and 2016. Our approach also revealed clinically undetected co-infections with CHIKV. Of the three DENV serotypes (1, 2, and 3) co-circulating during our study, we uncovered distinct patterns of evolution using comparative phylogenetic inference. DENV-1 genetic variation was structured into two distinct co-circulating lineages with no evidence of positive selection in the origins of either lineage, suggesting they are equally fit. In contrast, the evolutionary history of DENV-2 was marked by positive selection, and a unique, divergent lineage correlated with high epidemic potential emerged in 2015 to drive an outbreak in 2016. DENV-3 genetic variation remained unstructured into lineages throughout the period of study. Thus, this study reveals insights into evolutionary and epidemiologic trends exhibited during the circulation of multiple arboviruses in Nicaragua.
    Keywords:  Chikungunya virus; Dengue virus; Evolution; Nicaragua; Phylogenetics; Positive selection
    DOI:  https://doi.org/10.1016/j.meegid.2020.104680
  4. Viruses. 2020 Dec 16. pii: E1449. [Epub ahead of print]12(12):
    Shahhosseini N, Moosa-Kazemi SH, Sedaghat MM, Wong G, Chinikar S, Hajivand Z, Mokhayeri H, Nowotny N, Kayedi MH.
      Using molecular techniques and bioinformatics tools, we studied the vector-host interactions and the molecular epidemiology of West Nile virus (WNV) in western Iran. Mosquitoes were collected during 2017 and 2018. DNA typing assays were used to study vector-host interactions. Mosquitoes were screened by RT-PCR for the genomes of five virus families. WNV-positive samples were fully sequenced and evolutionary tree and molecular architecture were constructed by Geneious software and SWISS-MODEL workspace, respectively. A total of 5028 mosquito specimens were collected and identified. The most prevalent species was Culex (Cx.) pipiens complex (57.3%). Analysis of the blood-feeding preferences of blood-fed mosquitoes revealed six mammalian and one bird species as hosts. One mosquito pool containing non-blood-fed Cx. theileri and one blood-fed Culex pipiens pipiens (Cpp.) biotype pipiens were positive for WNV. A phylogram indicated that the obtained WNV sequences belonged to lineage 2, subclade 2 g. Several amino acid substitutions suspected as virulence markers were observed in the Iranian WNV strains. The three-dimensional structural homology model of the E-protein identified hot spot domains known to facilitate virus invasion and neurotropism. The recent detection of WNV lineage 2 in mosquitoes from several regions of Iran in consecutive years suggests that the virus is established in the country.
    Keywords:  Cx. pipiens; Cx. theileri; Iran; West Nile virus; phylogeny; virulence factors
    DOI:  https://doi.org/10.3390/v12121449
  5. Parasit Vectors. 2020 Dec 14. 13(1): 621
    Gomes ECS, Cruz DLD, Santos MAVM, Souza RMC, Oliveira CMF, Ayres CFJ, Domingos RM, Pedro MDGDS, Paiva MHS, Pimentel LMLM.
      BACKGROUND: Brazil has the fourth highest prevalence of malaria of all countries in the Americas, with an estimated 42 million people at risk of contracting this disease. Although most cases occur in the Amazon region, cases of an autochthonous nature have also been registered in the extra-Amazonian region where Anopheles aquasalis and An. albitarsis are the mosquito species of greatest epidemiological interest. In 2019, the municipality of Conde (state of Paraíba) experienced an epidemic of autochthonous cases of malaria. Here we present preliminary results of an entomological and case epidemiology investigation, in an attempt to correlate the diversity and spatial distribution of species of Anopheles with the autochthonous cases of this outbreak of malaria.METHODS: Case data were collected using case report forms made available by the Conde Municipal Health Department. The entomological survey was carried out from July to November 2019. The various methods of capture included the use of battery-powered aspirators, mouth aspirators, Shannon traps, BG-Sentinel traps (with and without dry ice) and CDC light traps. Captured mosquitoes were separated, packaged and sent to the laboratory for sexing and molecular identification of the various species of anophelines. The data were tabulated and analyzed using Microsoft Excel. Spatial analysis of the data was performed using ArcGis 10 software.
    RESULTS: In 2019, 20 autochthonous cases and one imported case of malaria caused by Plasmodium vivax were diagnosed, with three cases of relapses. A total of 3713 mosquitoes were collected, of which 3390 were culicines and 323 were anophelines. Nine species of genus Anopheles were identified, with the most abundant being An. aquasalis (38.9%), followed by An. minor (18.2%) and An. albitarsis (9.0%). Spatial analysis of the data showed that the area could be considered to be at risk of malaria cases and that there was a high prevalence of Anopheles.
    CONCLUSIONS: The results presented indicate that this extra-Amazonian region has an environment conducive to maintenance of the malaria transmission cycle owing to the wide diversity of Anopheles species. This environment in combination with the high influx of people from endemic areas to the study area provides a perfect setting for the occurrence and maintenance of malaria.
    Keywords:  Anopheles; Autochthonous transmission; Extra-amazon; Malaria; Outbreak; Plasmodium vivax; Spatial analysis
    DOI:  https://doi.org/10.1186/s13071-020-04502-7
  6. BMC Genet. 2020 Dec 18. 21(Suppl 2): 142
    Augustinos AA, Misbah-Ul-Haq M, Carvalho DO, de la Fuente LD, Koskinioti P, Bourtzis K.
      BACKGROUND: Aedes aegypti is the primary vector of arthropod-borne viruses and one of the most widespread and invasive mosquito species. Due to the lack of efficient specific drugs or vaccination strategies, vector population control methods, such as the sterile insect technique, are receiving renewed interest. However, availability of a reliable genetic sexing strategy is crucial, since there is almost zero tolerance for accidentally released females. Development of genetic sexing strains through classical genetics is hindered by genetic recombination that is not suppressed in males as is the case in many Diptera. Isolation of naturally-occurring or irradiation-induced inversions can enhance the genetic stability of genetic sexing strains developed through genetically linking desirable phenotypes with the male determining region.RESULTS: For the induction and isolation of inversions through irradiation, 200 male pupae of the 'BRA' wild type strain were irradiated at 30 Gy and 100 isomale lines were set up by crossing with homozygous 'red-eye' (re) mutant females. Recombination between re and the M locus and the white (w) gene (causing a recessive white eye phenotype when mutated) and the M locus was tested in 45 and 32 lines, respectively. One inversion (Inv35) reduced recombination between both re and the M locus, and wand the M locus, consistent with the presence of a rather extended inversion between the two morphological mutations, that includes the M locus. Another inversion (Inv5) reduced recombination only between w and the M locus. In search of naturally-occurring, recombination-suppressing inversions, homozygous females from the red eye and the white eye strains were crossed with seventeen and fourteen wild type strains collected worldwide, representing either recently colonized or long-established laboratory populations. Despite evidence of varying frequencies of recombination, no combination led to the elimination or substantial reduction of recombination.
    CONCLUSION: Inducing inversions through irradiation is a feasible strategy to isolate recombination suppressors either on the M or the m chromosome for Aedes aegypti. Such inversions can be incorporated in genetic sexing strains developed through classical genetics to enhance their genetic stability and support SIT or other approaches that aim to population suppression through male-delivered sterility.
    Keywords:  Chromosomal rearrangements; Genetic sexing strains; Population suppression; Sterile insect technique; Vector control
    DOI:  https://doi.org/10.1186/s12863-020-00949-w
  7. Pest Manag Sci. 2020 Dec 13.
    Kumar G, Ojha VP, Pasi S.
      Vector borne diseases (VBD) constitute 17% of all infectious diseases that are a major public health concern all over the world. In India itself, VBD like malaria and dengue continue to account for a significant disease burden. The management of these diseases in part is dependent upon effective vector control and hence several vector control strategies are in implementation for controlling mosquito populations. However, vectors evolve over time and become capable of averting many of the used control measures, which imposes a constant need to look for novel and improved interventions. Attractive toxic sugar baits or ATSB is one such vector control strategy that is novel and highly effective at regulating vector density in a particular area. ATSBs exploit the sugar feeding behaviour of mosquitoes. They are developed by combining small amounts of toxins with sugar. A chemical attractant is also included to lure the mosquito into the toxic sugary trap. Although effective, ATSBs have been tested in limited scope around the world and totally unexplored in the Indian scenario. In the present review, we provide an in-depth account of the development of ATSBs. We also highlight the potential of ATSBs in controlling major Indian vectors of malaria and dengue. We also discuss the possible challenges that could affect the efficacy of ATSBs in India. This article is protected by copyright. All rights reserved.
    Keywords:  Attractive toxic sugar baits (ATSB); India; sugar; vector control
    DOI:  https://doi.org/10.1002/ps.6226
  8. Viruses. 2020 Dec 14. pii: E1441. [Epub ahead of print]12(12):
    Bergman A, Dahl E, Lundkvist Å, Hesson JC.
      A crucial, but unresolved question concerning mosquito-borne virus transmission is how these viruses can remain endemic in regions where the transmission is halted for long periods of time, due to mosquito inactivity in, e.g., winter. In northern Europe, Sindbis virus (SINV) (genus alphavirus, Togaviridae) is transmitted among birds by Culex mosquitoes during the summer, with occasional symptomatic infections occurring in humans. In winter 2018-19, we sampled hibernating Culex spp females in a SINV endemic region in Sweden and assessed them individually for SINV infection status, blood-feeding status, and species. The results showed that 35 out of the 767 collected mosquitoes were infected by SINV, i.e., an infection rate of 4.6%. The vast majority of the collected mosquitoes had not previously blood-fed (98.4%) and were of the species Cx. pipiens (99.5%). This is the first study of SINV overwintering, and it concludes that SINV can be commonly found in the hibernating Cx. pipiens population in an endemic region in Sweden, and that these mosquitoes become infected through other means besides blood-feeding. Further studies on mosquito ecology and viral interactions are needed to elucidate the mechanisms of the persistence of these viruses over winter.
    Keywords:  Culex torrentium; alphavirus; arbovirus; overwintering; temperate region; vectors; virus persistence
    DOI:  https://doi.org/10.3390/v12121441
  9. Acta Trop. 2020 Dec 10. pii: S0001-706X(20)31709-5. [Epub ahead of print] 105796
    Marini G, Manica M, Delucchi L, Pugliese A, Rosà R.
      West Nile Virus (WNV) is now endemic in many European countries, causing hundreds of human cases every year, with a high spatial and temporal heterogeneity. Previous studies have suggested that spring temperature might play a key role at shaping WNV transmission. Specifically, warmer temperatures in April-May might amplify WNV circulation, thus increasing the risk for human transmission later in the year. To test this hypothesis, we collated publicly available data on the number of human infections recorded in Europe between 2011 and 2019. We then applied generalized linear models to quantify the relationship between human cases and spring temperature, considering both average conditions (over years 2003-2010) and deviations from the average for subsequent years (2011-2019). We found a significant positive association both spatial (average conditions) and temporal (deviations). The former indicates that WNV circulation is higher in usually warmer regions while the latter implies a predictive value of spring conditions over the coming season. We also found a positive association with WNV detection during the previous year, which can be interpreted as an indication of the reliability of the surveillance system but also of WNV overwintering capacity. Weather anomalies at the beginning of the mosquito breeding season might act as an early warning signal for public health authorities, enabling them to strengthen in advance ongoing surveillance and prevention strategies.
    Keywords:  Culex pipiens; early warning; mosquito; public health; vector-borne disease; zoonosis
    DOI:  https://doi.org/10.1016/j.actatropica.2020.105796
  10. J Parasitol Res. 2020 ;2020 8828670
    Haile D, Ferede A, Kassie B, Abebaw A, Million Y.
      Background: Malaria is a mosquito-borne infectious disease known to cause significant numbers of morbidities and mortalities across the globe. In Ethiopia, its transmission is generally seasonal and highly unstable due to variations in topography and rainfall patterns. Studying the trends in malaria in different setups is crucial for area-specific evidence-based interventions, informed decisions, and to track the effectiveness of malaria control programs. The trend in malaria infections in the area has not been documented. Hence, this study aimed to assess the five-year trend in microscopically confirmed malaria cases in Dembecha Health Center, West Gojjam Zone, Amhara national regional state, Ethiopia.Methods: A health facility-based retrospective study was conducted in Dembecha Health Center from February to April 2018. All microscopically confirmed malaria cases registered between 2011/12 and 2015/16 were carefully reviewed from laboratory record books and analyzed accordingly.
    Results: A total of 12,766 blood films were requested over the last five years at Dembecha Health Center. The number of microscopically confirmed malaria cases was 2086 (16.34%). The result showed a fluctuating yet declining trend in malaria infections. The highest number of cases was registered in 2012/13, while the lowest was in 2015/16. Males and age groups >20 constituted 58.9% and 44.2% of the patients, respectively, being the hardest hit by malaria in the area. Malaria existed in almost every month and seasons. Plasmodium falciparum was the predominant species. The highest peak of malaria infections was observed in the late transition (October-December) 799 (38.3%) and early transition (May-June) 589 (28.2%) seasons.
    Conclusion: Although the results indicate a fluctuating yet declining trend, the prevalence of confirmed malaria cases in the area remains alarming and indicates a major public health burden. Therefore, close monitoring and intervention measures to control malaria infections in the area and also to tackle the dominant species, Plasmodium falciparum, are necessitated accordingly.
    DOI:  https://doi.org/10.1155/2020/8828670
  11. Vector Borne Zoonotic Dis. 2020 Dec 17.
    Corrin T, Ackford R, Mascarenhas M, Greig J, Waddell LA.
      Background: Eastern equine encephalitis virus (EEEV) is a mosquito-borne virus that is primarily found in North America and the Caribbean. Over the past decade there has been an increase in virus activity, including large outbreaks in human and horse populations. Predicted climate change is expected to affect the range of mosquitoes including vectors of EEEV, which may alter disease risk posing a public health concern. Methods: A scoping review (ScR) was conducted to identify and characterize the global evidence on EEEV. A thorough search was conducted in relevant bibliographic databases and government websites. Two reviewers screened titles and abstracts for relevance and the characteristics of relevant articles were extracted using a uniformly implemented data collection form. The study protocol was developed a priori and described the methods and tools used and this article follows the PRISMA-ScR guidelines for reporting ScRs. Results: The ScR included 718 relevant research articles. The majority of the articles originated from North America (97%) between 1933 and 2019. EEEV has been identified in 35 species of mosquitoes, over 200 species of birds, various domestic animals, wild mammals, reptiles, and amphibians. Articles identified in this ScR primarily covered three topic areas: epidemiology of hosts and vectors (344 articles) including surveillance results (138), pathogenesis of EEEV in hosts (193), and in vitro studies characterizing EEEV (111). Fewer articles evaluated the accuracy of diagnostic tests (63), the efficacy of mitigation strategies (62), transmission dynamics (56), treatment of EEEV in hosts (10), societal knowledge, attitudes, and perceptions (4), and economic burden (2). Conclusion: With the projected impact of climate change on mosquito populations, it is expected that the risk of EEEV could change resulting in higher disease burden or spread into previously unaffected areas. Future research efforts should focus on closing some of the important knowledge gaps identified in this ScR.
    Keywords:  EEEV; eastern equine encephalitis virus; knowledge synthesis; mosquito-borne disease; scoping review; vector-borne disease
    DOI:  https://doi.org/10.1089/vbz.2020.2671
  12. BMC Infect Dis. 2020 Dec 11. 20(1): 947
    Teoh BT, Chin KL, Samsudin NI, Loong SK, Sam SS, Tan KK, Khor CS, Abd-Jamil J, Zainal N, Wilder-Smith A, Zandi K, AbuBakar S.
      BACKGROUND: Early detection of Zika virus (ZIKV) infection during the viremia and viruria facilitates proper patient management and mosquito control measurement to prevent disease spread. Therefore, a cost-effective nucleic acid detection method for the diagnosis of ZIKV infection, especially in resource-deficient settings, is highly required.METHODS: In the present study, a single-tube reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the detection of both the Asian and African-lineage ZIKV. The detection limit, strain coverage and cross-reactivity of the ZIKV RT-LAMP assay was evaluated. The sensitivity and specificity of the RT-LAMP were also evaluated using a total of 24 simulated clinical samples. The ZIKV quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was used as the reference assay.
    RESULTS: The detection limit of the RT-LAMP assay was 3.73 ZIKV RNA copies (probit analysis, P ≤ 0.05). The RT-LAMP assay detected the ZIKV genomes of both the Asian and African lineages without cross-reacting with other arthropod-borne viruses. The sensitivity and specificity of the RT-LAMP assay were 90% (95% CI = 59.6-98.2) and 100% (95% CI = 78.5-100.0), respectively. The RT-LAMP assay detected ZIKV genome in 9 of 24 (37.5%) of the simulated clinical samples compared to 10 of 24 (41.7%) by qRT-PCR assay with a high level of concordance (κ = 0.913, P < 0.001).
    CONCLUSION: The RT-LAMP assay is applicable for the broad coverage detection of both the Asian and African ZIKV strains in resource-deficient settings.
    Keywords:  Diagnostics; Infectious disease; Mosquito; RT-LAMP; Vector; Vector-borne; ZIKV
    DOI:  https://doi.org/10.1186/s12879-020-05585-4
  13. Am J Emerg Med. 2020 Dec 08. pii: S0735-6757(20)31125-6. [Epub ahead of print]
    Ali AA, Bajric B, Isache CL, Maharaj RP.
      Chikungunya is an arboviral infection that manifests as an acute viral illness associated with an inflammatory arthritis. It was first described during an outbreak in Tanzania in 1952 and, until 2013, outbreaks had been limited in Africa, Asia, Europe and the Indian and Pacific Oceans. In late 2013, the first local transmission of Chikungunya was identified in Caribbean countries with subsequent spread throughout Central and South America. In 2019, the CDC reported 171 travel-associated cases of Chikungunya in the United States. As of October 2020, the CDC records 17 travel-associated cases of Chikungunya in six states including California, Illinois, Missouri, North Carolina, Tennessee and Texas. This is the first reported case of Chikungunya acquired in Florida with no international travel history.
    DOI:  https://doi.org/10.1016/j.ajem.2020.12.008
  14. BMC Med. 2020 Dec 17. 18(1): 399
    Sun H, Dickens BL, Jit M, Cook AR, Carrasco LR.
      BACKGROUND: Zika virus (ZIKV) emerged as a global epidemic in 2015-2016 from Latin America with its true geographical extent remaining unclear due to widely presumed underreporting. The identification of locations with potential and unknown spread of ZIKV is a key yet understudied component for outbreak preparedness. Here, we aim to identify locations at a high risk of cryptic ZIKV spread during 2015-2016 to further the understanding of the global ZIKV epidemiology, which is critical for the mitigation of the risk of future epidemics.METHODS: We developed an importation simulation model to estimate the weekly number of ZIKV infections imported in each susceptible spatial unit (i.e. location that did not report any autochthonous Zika cases during 2015-2016), integrating epidemiological, demographic, and travel data as model inputs. Thereafter, a global risk model was applied to estimate the weekly ZIKV transmissibility during 2015-2016 for each location. Finally, we assessed the risk of onward ZIKV spread following importation in each susceptible spatial unit to identify locations with a high potential for cryptic ZIKV spread during 2015-2016.
    RESULTS: We have found 24 susceptible spatial units that were likely to have experienced cryptic ZIKV spread during 2015-2016, of which 10 continue to have a high risk estimate within a highly conservative scenario, namely, Luanda in Angola, Banten in Indonesia, Maharashtra in India, Lagos in Nigeria, Taiwan and Guangdong in China, Dakar in Senegal, Maputo in Mozambique, Kinshasa in Congo DRC, and Pool in Congo. Notably, among the 24 susceptible spatial units identified, some have reported their first ZIKV outbreaks since 2017, thus adding to the credibility of our results (derived using 2015-2016 data only).
    CONCLUSION: Our study has provided valuable insights into the potentially high-risk locations for cryptic ZIKV circulation during the 2015-2016 pandemic and has also laid a foundation for future studies that attempt to further narrow this key knowledge gap. Our modelling framework can be adapted to identify areas with likely unknown spread of other emerging vector-borne diseases, which has important implications for public health readiness especially in resource-limited settings.
    Keywords:  Epidemic preparedness; Global health; Mathematical modelling; Risk assessment; Surveillance capacity; Undetected transmission; Zika virus
    DOI:  https://doi.org/10.1186/s12916-020-01845-x
  15. PLoS Negl Trop Dis. 2020 Dec 16. 14(12): e0008945
    Ba H, Auburn S, Jacob CG, Goncalves S, Duffy CW, Stewart LB, Price RN, Deh YB, Diallo MY, Tandia A, Kwiatkowski DP, Conway DJ.
      BACKGROUND: Plasmodium vivax has been recently discovered as a significant cause of malaria in Mauritania, although very rare elsewhere in West Africa. It has not been known if this is a recently introduced or locally remnant parasite population, nor whether the genetic structure reflects epidemic or endemic transmission.METHODOLOGY/PRINCIPAL FINDINGS: To investigate the P. vivax population genetic structure in Mauritania and compare with populations previously analysed elsewhere, multi-locus genotyping was undertaken on 100 clinical isolates, using a genome-wide panel of 38 single nucleotide polymorphisms (SNPs), plus seven SNPs in drug resistance genes. The Mauritanian P. vivax population is shown to be genetically diverse and divergent from populations elsewhere, indicated consistently by genetic distance matrix analysis, principal components analyses, and fixation indices. Only one isolate had a genotype clearly indicating recent importation, from a southeast Asian source. There was no linkage disequilibrium in the local parasite population, and only a small number of infections appeared to be closely genetically related, indicating that there is ongoing genetic recombination consistent with endemic transmission. The P. vivax diversity in a remote mining town was similar to that in the capital Nouakchott, with no indication of local substructure or of epidemic population structure. Drug resistance alleles were virtually absent in Mauritania, in contrast with P. vivax in other areas of the world.
    CONCLUSIONS/SIGNIFICANCE: The molecular epidemiology indicates that there is long-standing endemic transmission that will be very challenging to eliminate. The virtual absence of drug resistance alleles suggests that most infections have been untreated, and that this endemic infection has been more neglected in comparison to P. vivax elsewhere.
    DOI:  https://doi.org/10.1371/journal.pntd.0008945
  16. BMC Public Health. 2020 Dec 14. 20(1): 1913
    Kigozi SP, Kigozi RN, Sebuguzi CM, Cano J, Rutazaana D, Opigo J, Bousema T, Yeka A, Gasasira A, Sartorius B, Pullan RL.
      BACKGROUND: As global progress to reduce malaria transmission continues, it is increasingly important to track changes in malaria incidence rather than prevalence. Risk estimates for Africa have largely underutilized available health management information systems (HMIS) data to monitor trends. This study uses national HMIS data, together with environmental and geographical data, to assess spatial-temporal patterns of malaria incidence at facility catchment level in Uganda, over a recent 5-year period.METHODS: Data reported by 3446 health facilities in Uganda, between July 2015 and September 2019, was analysed. To assess the geographic accessibility of the health facilities network, AccessMod was employed to determine a three-hour cost-distance catchment around each facility. Using confirmed malaria cases and total catchment population by facility, an ecological Bayesian conditional autoregressive spatial-temporal Poisson model was fitted to generate monthly posterior incidence rate estimates, adjusted for caregiver education, rainfall, land surface temperature, night-time light (an indicator of urbanicity), and vegetation index.
    RESULTS: An estimated 38.8 million (95% Credible Interval [CI]: 37.9-40.9) confirmed cases of malaria occurred over the period, with a national mean monthly incidence rate of 20.4 (95% CI: 19.9-21.5) cases per 1000, ranging from 8.9 (95% CI: 8.7-9.4) to 36.6 (95% CI: 35.7-38.5) across the study period. Strong seasonality was observed, with June-July experiencing highest peaks and February-March the lowest peaks. There was also considerable geographic heterogeneity in incidence, with health facility catchment relative risk during peak transmission months ranging from 0 to 50.5 (95% CI: 49.0-50.8) times higher than national average. Both districts and health facility catchments showed significant positive spatial autocorrelation; health facility catchments had global Moran's I = 0.3 (p < 0.001) and districts Moran's I = 0.4 (p < 0.001). Notably, significant clusters of high-risk health facility catchments were concentrated in Acholi, West Nile, Karamoja, and East Central - Busoga regions.
    CONCLUSION: Findings showed clear countrywide spatial-temporal patterns with clustering of malaria risk across districts and health facility catchments within high risk regions, which can facilitate targeting of interventions to those areas at highest risk. Moreover, despite high and perennial transmission, seasonality for malaria incidence highlights the potential for optimal and timely implementation of targeted interventions.
    Keywords:  HMIS; Incidence; Malaria; Relative risk; Routine surveillance; Seasonality; Uganda
    DOI:  https://doi.org/10.1186/s12889-020-10007-w
  17. Infect Drug Resist. 2020 ;13 4379-4387
    Sani Kalil F, Hasen Bedaso M, Kabeta Wario S.
      Background: Malaria is the major public health problem in sub-Saharan Africa, including Ethiopia. Ongoing malaria surveillance data analysis is useful for assessing incidences, trends over time, and evaluating the effectiveness of malaria prevention and control programs.Objective: To describe trends in malaria morbidity and mortality from 2010 to 2017 using surveillance data in Bale zone, Southeast Ethiopia.
    Methods: A retrospective study was conducted. Data were extracted from a public health emergency management surveillance database of Bale zonal health department. Data were entered into Microsoft office Excels worksheet 2016 and analyzed using Epi info version 7.2 software. Descriptive statistics was employed to calculate frequencies and percentages of malaria cases, trends of malaria transmission in terms of years, plasmodium species, gender, age, geographical and seasonal distribution. Malaria morbidity were assessed using the incidence rate of malaria cases per 1,000 population at risk and analyzed by year.
    Results: A total of 16,465 malaria cases were reported over 8 years. Of these, 10,986 (66.7%) were confirmed cases by microscopy/rapid diagnostic test. The majority of the cases, 82.2%, were reported among the >5 years age group and 62.9% were males. The overall 8 years average annual incidence was 3.1 cases/1,000 population at risk. There was an increase in incidence by 26% between 2010-2012, then a fall by 85% from 2012-2014, with another increaseby 52% from 2014-2017. The majority of the confirmed cases (81.5%) were due to Plasmodium falciparum species. The overall 8 years average annual death rate from malaria was 0.15/100,000 population.
    Conclusion: Even though a substantial reduction in morbidity and mortality of malaria was achieved, the possibility of observing severe cases was higher in the study area. Hence, the prevention and control program should be sustained and adjusted to address Plasmodium falciparum species.
    Keywords:  Bale zone; Southeast Ethiopia; incidence; malaria; morbidity; mortality; trend
    DOI:  https://doi.org/10.2147/IDR.S284281