bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2022–05–08
nineteen papers selected by
Richard Halfpenny, Staffordshire University
  1. A metapopulation approach to identify targets for Wolbachia-based dengue control.
  2. Community structure and insecticide resistance of malaria vectors in northern-central Myanmar.
  3. Dengue fever as a reemerging disease in upper Egypt: Diagnosis, vector surveillance and genetic diversity using RT-LAMP assay.
  4. Spatial heterogeneity of knockdown resistance mutations in the dengue vector Aedes albopictus in Guangzhou, China.
  5. Temporal variation of high-level pyrethroid resistance in the major malaria vector Anopheles gambiae s.l. in Yaoundé, Cameroon, is mediated by target-site and metabolic resistance.
  6. Outdoor malaria vector species profile in dryland ecosystems of Kenya.
  7. Defining virus-carrier networks that shape the composition of the mosquito core virome of a local ecosystem.
  8. West Nile Virus and Other Domestic Nationally Notifiable Arboviral Diseases - United States, 2020.
  9. Culex vishnui (Diptera: Culicidae): An Overlooked Vector of Arboviruses in South-East Asia.
  10. [West Nile virus unexpectedly in the Netherlands].
  11. Analysis of entomological indices for transmission of Japanese encephalitis in Malkangiri district, Odisha State, east central India during 2015-2019.
  12. Epidemiology of Indigenous Dengue Cases in Zhejiang Province, Southeast China.
  13. Implicit versus explicit vector management strategies in models for vector-borne disease epidemiology.
  14. Back on track towards malaria elimination - lessons and innovations.
  15. Assessing the effect of seasonal malaria chemoprevention on malaria burden among children under 5 years in Burkina Faso.
  16. Malaria epidemics in Colombia, 1970-2019.
  17. Potential role of vaccines in elimination of Plasmodium vivax.
  18. Epidemiological features of malaria in Bushehr province, southwest of Iran.
  19. Malaria transmission in Africa: Its relationship with yellow fever and measles.
  1. Chaos. 2022 Apr;32(4): 041105
    A metapopulation approach to identify targets for Wolbachia-based dengue control.
    A Reyna-Lara, D Soriano-Paños, J H Arias-Castro, H J Martínez, J Gómez-Gardeñes.
      Over the last decade, the release of Wolbachia-infected Aedes aegypti into the natural habitat of this mosquito species has become the most sustainable and long-lasting technique to prevent and control vector-borne diseases, such as dengue, zika, or chikungunya. However, the limited resources to generate such mosquitoes and their effective distribution in large areas dominated by the Aedes aegypti vector represent a challenge for policymakers. Here, we introduce a mathematical framework for the spread of dengue in which competition between wild and Wolbachia-infected mosquitoes, the cross-contagion patterns between humans and vectors, the heterogeneous distribution of the human population in different areas, and the mobility flows between them are combined. Our framework allows us to identify the most effective areas for the release of Wolbachia-infected mosquitoes to achieve a large decrease in the global dengue prevalence.
    DOI:  https://doi.org/10.1063/5.0087435
  2. Parasit Vectors. 2022 May 03. 15(1): 155
    Community structure and insecticide resistance of malaria vectors in northern-central Myanmar.
    Daibin Zhong, Pyae Linn Aung, Maung Maung Mya, Xiaoming Wang, Qian Qin, Myat Thu Soe, Guofa Zhou, Myat Phone Kyaw, Jetsumon Sattabongkot, Liwang Cui, Guiyun Yan.
       BACKGROUND: Myanmar is one of the six countries in the Greater Mekong Subregion (GMS) of Southeast Asia. Malaria vectors comprise many Anopheles species, which vary in abundance and importance in malaria transmission among different geographical locations in the GMS. Information about the species composition, abundance, and insecticide resistance status of vectorial systems in Myanmar is scarce, hindering our efforts to effectively control malaria vectors in this region.
    METHODS: During October and November 2019, larvae and adult females of Anopheles mosquitoes were collected in three sentinel villages of Banmauk township in northern Myanmar. Adult female mosquitoes collected by cow-baited tent collection (CBTC) and adults reared from field-collected larvae (RFCL) were used to determine mortality rates and knockdown resistance (kdr) against deltamethrin using the standard WHO susceptibility test. Molecular species identification was performed by multiplex PCR and ITS2 PCR, followed by DNA sequencing. The kdr mutation at position 1014 of the voltage-gated sodium channel gene was genotyped by DNA sequencing for all Anopheles species tested.
    RESULTS: A total of 1596 Anopheles mosquitoes from seven morphologically identified species groups were bioassayed. Confirmed resistance to deltamethrin was detected in the populations of An. barbirostris (s.l.), An. hyrcanus (s.l.), and An. vagus, while possible resistance was detected in An. annularis (s.l.), An. minimus, and An. tessellatus. Anopheles kochi was found susceptible to deltamethrin. Compared to adults collected by CBTC, female adults from RFCL had significantly lower mortality rates in the four species complexes. A total of 1638 individuals from 22 Anopheles species were molecularly identified, with the four most common species being An. dissidens (20.5%) of the Barbirostris group, An. peditaeniatus (19.4%) of the Hyrcanus group, An. aconitus (13.4%) of the Funestus group, and An. nivipes (11.5%) of the Annularis group. The kdr mutation L1014F was only detected in the homozygous state in two An. subpictus (s.l.) specimens and in a heterozygous state in one An. culicifacies (s.l.) specimen.
    CONCLUSIONS: This study provides updated information about malaria vector species composition and insecticide resistance status in northern Myanmar. The confirmed deltamethrin resistance in multiple species groups constitutes a significant threat to malaria vector control. The lack or low frequency of target-site resistance mutations suggests that other mechanisms are involved in resistance. Continual monitoring of the insecticide resistance of malaria vectors is required for effective vector control and insecticide resistance management.
    Keywords:  Anopheles malaria vectors; Community structure; Insecticide resistance; Kdr mutation; Myanmar; Ribosomal internal transcribed spacer 2
    DOI:  https://doi.org/10.1186/s13071-022-05262-2
  3. PLoS One. 2022 ;17(5): e0265760
    Dengue fever as a reemerging disease in upper Egypt: Diagnosis, vector surveillance and genetic diversity using RT-LAMP assay.
    Mona Gaber, Alzahraa Abdelraouf Ahmad, Asmaa M El-Kady, Mohammed Tolba, Yutaka Suzuki, Shereen M Mohammed, Nahed Ahmed Elossily.
       BACKGROUND: The recent increase in dengue virus (DENV) outbreaks and the absence of an effective vaccine have highlighted the importance of developing rapid and effective diagnostic surveillance tests and mosquito-based screening programs. To establish effective control measures for preventing future DENV transmission, the present study was established to identify the main mosquito vector involved in the dengue fever (DF) outbreak in Upper Egypt in 2016 and detect the diversity of dengue virus serotypes circulating in both humans and vectors.
    METHODS: We investigated the prevalence of DENV infection and circulating serotypes in the sera of 51 humans clinically suspected of DF and 1800 field-collected Aedes aegypti adult female mosquitoes grouped into 36 pooled samples. Both DENV non-structural protein (NS1) immunochromatographic strip assay and loop-mediated isothermal amplification (LAMP) were used for screening.
    RESULTS: Overall, the rate of DENV infection in both human sera and pooled mosquito homogenate was 33.3%, as revealed by rapid dipstick immunochromatographic analysis. However, higher detection rates were observed with RT-LAMP assay of 60.8% and 44.4% for humans and vector mosquitoes, respectively. DENV-1 was the most prevalent serotype in both populations. A combination of two, three, or even four circulating serotypes was found in 87.5% of total positive pooled mosquito samples and 83.87% of DENV-positive human sera.
    CONCLUSION: The study reinforces the evidence of the reemergence of Aedes aegypti in Upper Egypt, inducing an outbreak of DENV. Mosquito-based surveillance of DENV infection is important to elucidate the viral activity rate and define serotype diversity to understand the virus dynamics in the reinfested area. Up to our knowledge, this is the first report of serotyping of DENV infection in an outbreak in Egypt using RT-LAMP assay.
    DOI:  https://doi.org/10.1371/journal.pone.0265760
  4. Parasit Vectors. 2022 May 03. 15(1): 156
    Spatial heterogeneity of knockdown resistance mutations in the dengue vector Aedes albopictus in Guangzhou, China.
    Xueli Zheng, Zihao Zheng, Shanshan Wu, Yong Wei, Lei Luo, Daibin Zhong, Guofa Zhou.
       BACKGROUND: The city of Guangzhou has been the epicenter of dengue fever in China since the 1990s, with Aedes albopictus being the primary vector. The main method used to control vectors and prevent dengue fever has been the application of chemical insecticides; however, this control strategy has resulted in the development of resistance to these insecticides in mosquitoes. Here we report our investigation of the patterns of knockdown resistance (kdr) mutations in 15 field populations of Ae. albopictus collected from 11 districts in Guangzhou.
    RESULTS: Four mutant alleles (V1016G, F1534S, F1534C, F1534L) were detected in domain II and III of the voltage-gated sodium channel (VGSC) gene. Various allele frequencies of kdr mutations were observed (3.1-25.9% for V1016G, 22.6-85.5% for F1534S, 0-29.0% for F1534L, 0.6-54.2% for F1534C). Seven kdr haplotypes (VF, VS, VL, VC, GF, GC, GS) were identified; the highest frequency of haplotypes was found for the single mutant haplotype VS (50.8%), followed by the wild-type VF haplotype (21.7%) and the single mutant haplotype VC (11.9%). Of the three double mutant haplotypes, GF was the most frequent (8.8%), followed by GC (1.2%) and GS (0.8%). Aedes albopictus showed spatial heterogeneity in deltamethrin resistance in populations collected in Guangzhou. We also observed significant differences in haplotype frequency. The frequency of the VC haplotype was significantly higher in high-risk dengue areas than in low-risk ones.
    CONCLUSIONS: The kdr allele V1016G was discovered for the first time in Guangzhou. Genetic isolation in mosquito populations and long-term insecticide selection seem to be responsible for the persistent, patchy distribution of kdr mutant alleles. The small-scale spatial heterogeneity in the distribution and frequency of kdr mutations may have important implications for vector control operations and insecticide resistance management strategies.
    Keywords:  Aedes albopictus; Guangzhou; Haplotype frequency; Insecticide resistance; Voltage-gated sodium channel gene
    DOI:  https://doi.org/10.1186/s13071-022-05241-7
  5. Med Vet Entomol. 2022 May 06.
    Temporal variation of high-level pyrethroid resistance in the major malaria vector Anopheles gambiae s.l. in Yaoundé, Cameroon, is mediated by target-site and metabolic resistance.
    Billy Tene-Fossog, Yvan Gaetan Fotso-Toguem, Nathalie Amvongo-Adjia, Hilary Ranson, Charles S Wondji.
      Constant assessment of insecticide resistance levels is mandatory to implement adequate malaria control tools, but little information is available on the annual dynamics of resistance. We, therefore, monitored variations in resistance in Anopheles gambiae s.l. over four seasons during 2 years in two localities of Yaoundé: urban Etoa-Meki and peri-urban Nkolondom. Mosquitoes were collected seasonally at larval stage and reared to adults for insecticide susceptibility tests and molecular analysis of resistance mechanisms. Anopheles coluzzii was found in Etoa-Meki and An. gambiae in Nkolondom. Low mortalities to pyrethroids were observed (permethrin <10%, deltamethrin <21%), and resistance extended to 5× and 10× diagnostic doses, revealing a marked increase compared to previous studies. A seasonal variation in resistance was observed with the highest levels within dry seasons in Etoa-Meki and rainy seasons in Nkolondom. The 1014F kdr allele shows a high frequency (0.9), associated with overexpression of metabolic genes (Cyp6M2, Cyp6P4, Cyp9K1, Cyp6Z1, and Cyp6Z2) varying significantly seasonally. This study reveals an escalation in resistance to pyrethroids in Yaoundé's malaria vectors with seasonal variations. An adequate choice of the implementation period of punctual vector control actions according to the resistance profile will help to potentiate the desired effect and thus improve its efficiency.
    Keywords:  Anopheles coluzzii; Anopheles gambiae; insecticide resistance; resistance dynamic; resistance intensity; seasons; vector control
    DOI:  https://doi.org/10.1111/mve.12577
  6. Sci Rep. 2022 May 03. 12(1): 7131
    Outdoor malaria vector species profile in dryland ecosystems of Kenya.
    Fiona Kinya, Clifford M Mutero, Rosemary Sang, Eunice A Owino, Gilbert Rotich, Edwin O Ogola, Charles S Wondji, Baldwyn Torto, David P Tchouassi.
      Outdoor biting by anopheline mosquitoes is one of the contributors to residual malaria transmission, but the profile of vectors driving this phenomenon is not well understood. Here, we studied the bionomics and genetically characterized populations of An. gambiae and An. funestus complexes trapped outdoors in three selected dryland areas including Kerio Valley, Nguruman and Rabai in Kenya. We observed a higher abundance of Anopheles funestus group members (n = 639, 90.6%) compared to those of the An. gambiae complex (n = 66, 9.4%) with An. longipalpis C as the dominant vector species with a Plasmodium falciparum sporozoite rate (Pfsp) of 5.2% (19/362). The known malaria vectors including An. funestus s.s. (8.7%, 2/23), An. gambiae (14.3%, 2/14), An. rivulorum (14.1%, 9/64), An. arabiensis (1.9%, 1/52) occurred in low densities and displayed high Pfsp rates, which varied with the site. Additionally, six cryptic species found associated with the An. funestus group harbored Pf sporozoites (cumulative Pfsp rate = 7.2%, 13/181). We detected low frequency of resistant 119F-GSTe2 alleles in An. funestus s.s. (15.6%) and An. longipalpis C (3.1%) in Kerio Valley only. Evidence of outdoor activity, emergence of novel and divergent vectors and detection of mutations conferring metabolic resistance to pyrethroid/DDT could contribute to residual malaria transmission posing a threat to effective malaria control.
    DOI:  https://doi.org/10.1038/s41598-022-11333-2
  7. Virus Evol. 2022 ;8(1): veac036
    Defining virus-carrier networks that shape the composition of the mosquito core virome of a local ecosystem.
    Konstantinos Konstantinidis, Nikolas Dovrolis, Adamantia Kouvela, Katerina Kassela, Maria Goreti Rosa Freitas, Andreas Nearchou, Michael de Courcy Williams, Stavroula Veletza, Ioannis Karakasiliotis.
      Mosquitoes are the most important vectors of emerging infectious diseases. During the past decade, our understanding of the diversity of viruses they carry has greatly expanded. Most of these viruses are considered mosquito-specific, but there is increasing evidence that these viruses may affect the vector competence of mosquitoes. Metagenomics approaches have focused on specific mosquito species for the identification of what is called the core virome. Despite the fact that, in most ecosystems, multiple species may participate in virus emergence and circulation, there is a lack of understanding of the virus-carrier/host network for both vector-borne and mosquito-specific viruses. Here, we studied the core virome of mosquitoes in a diverse local ecosystem that had 24 different mosquito species. The analysis of the viromes of these 24 mosquito species resulted in the identification of 34 viruses, which included 15 novel viruses, as determined according to the species demarcation criteria of the respective virus families. Most of the mosquito species had never been analysed previously, and a comparison of the individual viromes of the 24 mosquito species revealed novel relationships among mosquito species and virus families. Groups of related viruses and mosquito species from multiple genera formed a complex web in the local ecosystem. Furthermore, analyses of the virome of mixed-species pools of mosquitoes from representative traps of the local ecosystem showed almost complete overlap with the individual-species viromes identified in the study. Quantitative analysis of viruses' relative abundance revealed a linear relationship to the abundance of the respective carrier/host mosquito species, supporting the theory of a stable core virome in the most abundant species of the local ecosystem. Finally, our study highlights the importance of using a holistic approach to investigating mosquito viromes relationships in rich and diverse ecosystems.
    Keywords:  ecosystem; metagenomics; mosquitoes; vectors; virome
    DOI:  https://doi.org/10.1093/ve/veac036
  8. MMWR Morb Mortal Wkly Rep. 2022 May 06. 71(18): 628-632
    West Nile Virus and Other Domestic Nationally Notifiable Arboviral Diseases - United States, 2020.
    Raymond A Soto, Matthew L Hughes, J Erin Staples, Nicole P Lindsey.
      Arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bite of infected mosquitoes and ticks. West Nile virus (WNV), mainly transmitted by Culex species mosquitos, is the leading cause of domestically acquired arboviral disease in the United States (1). Other arboviruses cause sporadic cases of disease and occasional outbreaks. This report summarizes passive data for nationally notifiable domestic arboviruses in the United States reported to CDC for 2020. Forty-four states reported 884 cases of domestic arboviral disease, including those caused by West Nile (731), La Crosse (88), Powassan (21), St. Louis encephalitis (16), eastern equine encephalitis (13), Jamestown Canyon (13), and unspecified California serogroup (2) viruses. A total of 559 cases of neuroinvasive WNV disease were reported, for a national incidence of 0.17 cases per 100,000 population. Because arboviral diseases continue to cause serious illness and the locations of outbreaks vary annually, health care providers should consider arboviral infections in patients with aseptic meningitis or encephalitis that occur during periods when ticks and mosquitoes are active, perform recommended diagnostic testing, and promptly report cases to public health authorities to guide prevention strategies and messaging.
    DOI:  https://doi.org/10.15585/mmwr.mm7118a3
  9. J Med Entomol. 2022 May 06. pii: tjac044. [Epub ahead of print]
    Culex vishnui (Diptera: Culicidae): An Overlooked Vector of Arboviruses in South-East Asia.
    Pierre-Olivier Maquart, Leakena Chann, Sebastien Boyer.
      Culex vishnui Theobald, 1901, a main vector of Japanese encephalitis virus (JEV), is widely distributed in the Oriental region where it often accounts for a great part of the culicid fauna. This species also has been found naturally infected with at least 13 other arboviruses of medical and veterinary importance. Females blood feed predominantly upon pigs and birds, but may readily bite cattle and humans. Because of its abundance, medical importance, and presence throughout ecological gradients among urban, peri-urban, and rural areas, Cx. vishnui potentially may serve as a bridge vector transmitting viruses from natural and wild hosts to humans. Being zoo- and anthropophagic, omnipresent in the Oriental region, and presenting strong resistance to many insecticide families, this overlooked mosquito species may pose a serious health risk in one of the most densely populated regions of the world.
    Keywords:   Culex pseudovishnui ; Culex tritaeniorhynchus ; Japanese encephalitis; arboviruses; bridge vector
    DOI:  https://doi.org/10.1093/jme/tjac044
  10. Ned Tijdschr Geneeskd. 2022 03 28. pii: D6278. [Epub ahead of print]166
    [West Nile virus unexpectedly in the Netherlands].
    Marieta A H Braks, Janneke W Duijster, C Arjan J Stroo.
      West Nile virus (WNV) was first detected in birds, mosquitoes and subsequently in humans in the Netherlands in 2020. In 2016 , we had discussed the factors that influence the introduction, establishment and dissemination of WNV in the Netherlands and considered the probability that each of these three phases could occur in the Netherlands, and cause West Nile fever in humans, still relatively small. In the current article we evaluate on the basis of our reasoning at the time, whether we have missed important factors and/or whether new factors have appeared on the horizon. We then explain what the findings/ this progressive insight of 2020 mean for the near future.
  11. Pathog Glob Health. 2022 May 02. 1-7
    Analysis of entomological indices for transmission of Japanese encephalitis in Malkangiri district, Odisha State, east central India during 2015-2019.
    Sonia Thankachy, Smrutidhara Dash, Muthukumaravel Subramanian, Sankari Thirumal, Vijayakumar Balakrishnan, Sudhansu Sekhar Sahu.
      There have been repeated episodes of the outbreak of Japanese encephalitis (JE) in Malkangiri district of Odisha State in the recent past. In the current study, we aimed to assess the entomological parameters of JE vectors in the district. Prevalence of JE vector species, their per man hour density (PMHD), dusk index (DI), human blood index (HBI), infection status and other factors responsible for transmission of JE were assessed over 5 years (2015-2019). Culex vishnui was the predominant JE vector species (32.0%) collected, followed by Cx. whitmorei (27.1%) and Cx. tritaeniorhynchus (18.0%). The PMHD was higher in cattle shed (CS) than human dwelling (HD) and outdoor resting collection (ODRC) sites for all the JE vector species, except An. barbirostris. In particular, the PMHD of Cx. vishnui (8.02), Cx. whitmorei (5.71) and Cx. tritaeniorhynchus (5.01) were significantly higher in CS than HD and ODRC. The DI of Cx. vishnui (2.47), Cx. whitmorei (1.66) and Cx. tritaeniorhynchus (1.59) was significantly higher in CS compared to HD and ODRC. The HBI of Cx. vishnui was 0.015, whereas the HBI of Cx. tritaeniorhynchus was 0.009 in the study area. Among the 829 pools of JE vector species subjected to PCR, JE virus was isolated from one pool of Cx. vishnui. Based on the abundance of JE vectors and JE virus isolation from Cx. vishnui, it is requisite to implement systematic and long-term control measures for effective control of JE vector species in Malkangiri district, Odisha State.
    Keywords:  Cx. tritaeniorhynchus; Cx. vishnui; JE outbreak; Japanese encephalitis; Malkangiri; Odisha
    DOI:  https://doi.org/10.1080/20477724.2022.2071051
  12. Front Public Health. 2022 ;10 857911
    Epidemiology of Indigenous Dengue Cases in Zhejiang Province, Southeast China.
    Jiangping Ren, Zhiping Chen, Feng Ling, Yangmei Huang, Zhenyu Gong, Ying Liu, Zhiyuan Mao, Chunping Lin, Hao Yan, Xuguang Shi, Rong Zhang, Song Guo, Enfu Chen, Zhen Wang, Jimin Sun.
       Objective: Autochthonous transmission of the dengue virus (DENV) occurred each year from 2014 to 2018 in Zhejiang province, and became an emerging public health problem. We characterized the autochthonous transmission of the DENV and traced the source of infection for further control and prevention of dengue.
    Methods: Descriptive and spatiotemporal cluster analyses were conducted to characterize the epidemiology of autochthonous transmission of the DENV. Molecular epidemiology was used to identify the infection source.
    Results: In total, 1,654 indigenous cases and 12 outbreaks, with no deaths, were reported during 2004-2018. Before 2017, all outbreaks occurred in suburban areas. During 2017-2018, five out of eight outbreaks occurred in urban areas. The median duration of outbreaks (28 days) in 2017-2018 was shortened significantly (P = 0.028) in comparison with that in 2004-2016 (71 days). The median onset-visiting time, visiting-confirmation time, and onset-confirmation time was 1, 3, and 4 days, respectively. The DENV serotypes responsible for autochthonous transmission in Zhejiang Province were DENV 1, DENV 2, and DENV 3, with DENV 1 being the most frequently reported. Southeast Asia was the predominant source of indigenous infection.
    Conclusions: Zhejiang Province witnessed an increase in the frequency, incidence, and geographic expansion of indigenous Dengue cases in recent years. The more developed coastal and central region of Zhejiang Province was impacted the most.
    Keywords:  China; dengue; emergence; epidemiology; outbreak
    DOI:  https://doi.org/10.3389/fpubh.2022.857911
  13. J Math Biol. 2022 May 05. 84(6): 48
    Implicit versus explicit vector management strategies in models for vector-borne disease epidemiology.
    Jeffery Demers, Suzanne L Robertson, Sharon Bewick, William F Fagan.
      Throughout the vector-borne disease modeling literature, there exist two general frameworks for incorporating vector management strategies (e.g. area-wide adulticide spraying and larval source reduction campaigns) into vector population models, namely, the "implicit" and "explicit" control frameworks. The more simplistic "implicit" framework facilitates derivation of mathematically rigorous results on disease suppression and optimal control, but the biological connection of these results to real-world "explicit" control actions that could guide specific management actions is vague at best. Here, we formally define a biological and mathematical relationship between implicit and explicit control, and we provide mathematical expressions relating the strength of implicit control to management-relevant properties of explicit control for four common intervention strategies. These expressions allow the optimal control and basic reproduction number analyses typically utilized in implicit control modeling to be interpreted directly in terms of real-world actions and real-world monetary costs. Our methods reveal that only certain sub-classes of explicit control protocols are able to be represented as implicit controls, and that implicit control is a meaningful approximation of explicit control only when resonance-like synergistic effects between multiple explicit controls have negligible effects on population reduction. When non-negligible synergy exists, implicit control results, despite their mathematical tidiness, fail to provide accurate predictions regarding vector control and disease spread. Collectively, these elements build an effective bridge between analytically interesting and mathematically tractable implicit control and the challenging, action-oriented explicit control.
    Keywords:  Adulticide; Disease control; Larval source reduction; Larvicide; Mosquito control; Vector-borne disease
    DOI:  https://doi.org/10.1007/s00285-022-01742-2
  14. Lancet Reg Health West Pac. 2022 Apr;21 100473
    Back on track towards malaria elimination - lessons and innovations.
    The Lancet Regional Health-Western Pacific.
      
    DOI:  https://doi.org/10.1016/j.lanwpc.2022.100473
  15. Malar J. 2022 May 06. 21(1): 143
    Assessing the effect of seasonal malaria chemoprevention on malaria burden among children under 5 years in Burkina Faso.
    Fati Kirakoya-Samadoulougou, Vincent De Brouwere, Arnold Fottsoh Fokam, Mady Ouédraogo, Yazoumé Yé.
       BACKGROUND: In 2014, the Burkina Faso government launched the Seasonal Malaria Chemoprevention (SMC) programme. Expected benefit was a 75% reduction of all malaria episodes and a 75% drop of severe malaria episodes. This study assessed SMC efficiency on malaria morbidity in the country after 2 years of implementation.
    METHODS: Quasi-experimental design comparing changes in outcomes during the high transmission period (August-November) between SMC and non-SMC health districts before (2013-2014) and after intervention (two rounds in 2015 and 2016). Health indicators (number of uncomplicated malaria cases (UM) and severe malaria cases (SM)) from 19 health districts (8 in intervention and 11 in comparison group) were extracted from the District Health Information System (DHIS2)-based platform including health facilities data. Effect on incidence was assessed by fitting difference-in difference mixed-effects negative binomial regression model at a log scale.
    RESULTS: The two rounds of SMC were associated with a reduction of UM incidence (ratio of incidence rate ratio (IRR) 69% (95% CI 55-86%); p = 0.001) and SM incidence (ratio of IRR = 73% (55-95%), p = 0.018) among under five children.
    CONCLUSION: The two rounds of SMC had a significant effect on the reduction of malaria cases in under five children. This additional evidence on the effectiveness of SMC, using routine data, support the need to sustain its implementation and consider expansion to eligible areas not yet covered.
    Keywords:  Burkina Faso; Evaluation; Impact; Malaria; Seasonal malaria chemoprevention
    DOI:  https://doi.org/10.1186/s12936-022-04172-z
  16. Rev Soc Bras Med Trop. 2022 ;pii: S0037-86822022000100611. [Epub ahead of print]55 e05592021
    Malaria epidemics in Colombia, 1970-2019.
    Julio Cesar Padilla Rodríguez, Mario Javier Olivera, María Cristina Padilla Herrera, Edwin Pachón Abril.
       BACKGROUND: Malaria has unstable transmission in Colombia and has variable endemic-epidemic patterns. This study describes the epidemiological characteristics of malaria epidemics registered in Colombia from 1970-2019.
    METHODS: Data from 1979-2019 were collected from the National Public Health Surveillance System. The data was tabulated and pertinent descriptive analyses were carried out.
    RESULTS: Fifteen malaria outbreaks and approximately five-year-long epidemic cycles were observed in Colombia during the study period.
    CONCLUSIONS: Malaria epidemics in Colombia present a five-yearly transmission pattern, mainly due to the increased vulnerability produced by seasonal population migrations in receptive areas with active transmission.
    DOI:  https://doi.org/10.1590/0037-8682-0559-2021
  17. Parasitol Int. 2022 Apr 27. pii: S1383-5769(22)00056-3. [Epub ahead of print] 102592
    Potential role of vaccines in elimination of Plasmodium vivax.
    Michael White, Chetan E Chitnis.
      The unique biology of Plasmodium vivax, with its ability to form latent hypnozoites in the liver stage and the early appearance of gametocytes during blood stage infection, makes it difficult to target for elimination with standard malaria control tools. Here, we use modelling studies to demonstrate that vaccines that target different stages of P. vivax could greatly assist efforts to eliminate P. vivax. Combination of vaccines that target different P. vivax life cycle stages may be required to achieve high efficacy. Our simulations demonstrate that repeated rounds of mass vaccination with multi-stage vaccines can help achieve pre-elimination levels of P. vivax in both low and high transmission settings. We review the status of global efforts to develop vaccines for P. vivax malaria. We describe the status of the leading P. vivax vaccine candidates and share some thoughts on the prospects for availability of an effective vaccine for P. vivax malaria.
    Keywords:  Immunity; P. vivax; Vaccines
    DOI:  https://doi.org/10.1016/j.parint.2022.102592
  18. Ann Parasitol. 2022 ;68(1): 93-101
    Epidemiological features of malaria in Bushehr province, southwest of Iran.
    Fatemeh Najafi-Sharjabad, Amir Hossein Darabi, Ali Kazerouni, Mohammad Rayani.
      The purpose of this research was to describe the malaria situation in Bushehr province from 2011 to 2018. The current study is a descriptive cross-sectional study based on available data. Between 2011 and 2018, 715 malaria patients were registered in the Bushehr province. The data were analyzed using IBM SPSS Statistics version 22. Male patients made up 92.7% of the total, while female patients made up 7.3%. The age group of 20-29 years had the highest frequency of malaria patients (42.3%), while the age group of over 50 years had the lowest frequency patients (2.5%). Regarding nationality, (96.9%) of malaria patients were Afghans, (2.2%) were Pakistanis, (0.8%) were Iranians, and (0.1%) were Indians. The disease was reported to be the most prevalent in 2017 and the least common in 2013 (29.6% and 2.6%). During this time, malaria prevalence has risen and fallen. Bushehr county had the greatest malaria prevalence (42%) and was followed by Kangan county (20.1%) and Asaluyeh county (12.9%). In terms of parasites, Plasmodium vivax was responsible for (94%) of the cases, P. falciparum for (2.4%), and mixed infection (P. vivax and P. falciparum) for (3.6%). Regarding disease transmission, (93.6%) was imported, (1%) was relapse, (0.4%) was indigenous, and (1.3%) was relapse and imported. Bushehr province is at risk of transmitting malaria due to suitable climatic conditions for the reproduction of vector mosquitoes. As well, it confronts the threat of imported malaria, which has caused concern in recent years as a result of the increase of job-seeking migrants. Strategies of malaria control, basic measures in the field of timely diagnosis and rapid and complete treatment of patients, especially in foreign nationals, vectors control, and preventive approaches are required to eliminate malaria in this province.
    DOI:  https://doi.org/10.17420/ap6801.413
  19. PLoS One. 2022 ;17(5): e0268080
    Malaria transmission in Africa: Its relationship with yellow fever and measles.
    Oluyemi A Okunlola, Oyetunde T Oyeyemi.
       BACKGROUND: Malaria has been strongly linked to the transmission and pathophysiology of some viral diseases. Malaria and vaccine-preventable diseases often co-exist in endemic countries but the implication of their co-existence on their transmission dynamics and control is poorly understood. The study aims to evaluate the relationships between the incidence of malaria and cases of measles and yellow fever in Africa.
    METHODS: The malaria incidence, death due to malaria, measles and yellow fever data were sourced from the WHO database. Poisson and zero-inflated time-trend regression were used to model the relationships between malaria and the two vaccine-preventable diseases. P-values <0.05 were considered statistically significant.
    RESULTS: A significant negative relationship existed between malaria incidence and measles cases (P<0.05), however, malaria showed a positive relationship with yellow fever (P<0.05). The relationships between death due to malaria and measles/yellow fever cases followed similar trends but with a higher level of statistical significance (P<0.001).
    CONCLUSIONS: Malaria varied negatively with measles cases but positively with yellow fever. The relationships observed in this study could be important for the management of malaria and the studied vaccine-preventable diseases. Increase vaccination coverage and/or malaria treatment could modulate the direction of these relationships.
    DOI:  https://doi.org/10.1371/journal.pone.0268080
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