bims-mosdis 2023-03-26 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2023‒03‒26
29 papers selected by
Richard Halfpenny, Staffordshire University

Mosquito diversity (Diptera: Culicidae) and medical importance in four Cambodian forests.
Beyond eves and cracks: An interdisciplinary study of socio-spatial variation in urban malaria transmission in Ethiopia.
Effects of Seasonal Conditions on Abundance of Malaria Vector Anopheles stephensi Mosquitoes, Djibouti, 2018-2021.
Evaluation of the evolutionary genetics and population structure of Culex pipiens pallens in Shandong province, China based on knockdown resistance (kdr) mutations and the mtDNA-COI gene.
Insecticide resistance compromises the control of Aedes aegypti in Bangladesh.
Knowledge, attitudes, and practices of Anopheles mosquito control through insecticide treated nets and community-based health programs to prevent malaria in East Sumba Island, Indonesia.
Mapping current and future thermal limits to suitability for malaria transmission by the invasive mosquito Anopheles stephensi.
Culex (Phenacomyia) lactator (Diptera: Culicidae) in southern Florida, USA: a new subgenus and species country record.
Trophic preferences of Anopheles coluzzii (Diptera: Culicidae): what implications for malaria vector control in Benin?
Household modifications after the indoor residual spraying (IRS) campaign in Mozambique reduce the actual spray coverage and efficacy.
Resurgence of malaria in Uganda despite sustained indoor residual spraying and repeated long lasting insecticidal net distributions.
Influence of climate variables on dengue fever occurrence in the southern region of Thailand.
The impact of hydropower dam construction on malaria incidence: Space-time analysis in the Brazilian Amazon.
Tracking district-level performance in the context of achieving zero indigenous case status by 2027.
Economic impact of dengue in Singapore from 2010 to 2020 and the cost-effectiveness of Wolbachia interventions.
Climate change and Aedes albopictus risks in China: current impact and future projection.
Malaria outbreak facilitated by engagement in activities near swamps following increased rainfall and limited preventive measures: Oyam District, Uganda.
Epidemiological profile of arboviruses in two different scenarios: dengue circulation vs. dengue, chikungunya and Zika co-circulation.
Malaria prevalence, knowledge and associated factors among household heads in Maygaba town, Ethiopia.
First official record of Aedes (Stegomyia) albopictus (Diptera: Culicidae) in the Acre State, Northern Brazil.
Malaria hotspots and climate change trends in the hyper-endemic malaria settings of Mizoram along the India-Bangladesh borders.
Community-based house improvement for malaria control in southern Malawi: Stakeholder perceptions, experiences, and acceptability.
Assessing the effectiveness of malaria interventions at the regional level in Ghana using a mathematical modelling application.
Chikungunya Outbreak in Country with Multiple Vectorborne Diseases, Djibouti, 2019-2020.
Stratification of malaria incidence in Papua New Guinea (2011-2019): Contribution towards a sub-national control policy.
What Africa can do to accelerate and sustain progress against malaria.
Rethinking human resources and capacity building needs for malaria control and elimination in Africa.
Environmental and socio-economic determinants of the occurrence of malaria clusters in Colombia.
Plasmodium falciparum importation does not sustain malaria transmission in a semi-arid region of Kenya.

Parasit Vectors. 2023 Mar 21. 16(1): 110

Mosquito diversity (Diptera: Culicidae) and medical importance in four Cambodian forests.

Antsa Rakotonirina, Pierre-Olivier Maquart, Claude Flamand, Chea Sokha, Sébastien Boyer.

  BACKGROUND: A total of 290 mosquito species are recorded in Cambodia among which 43 are known vectors of pathogens. As Cambodia is heavily affected by deforestation, a potential change in the dynamic of vector-borne diseases (VDBs) could occur through alteration of the diversity and density of sylvatic vector mosquitoes and induce an increase in their interactions with humans. Understanding mosquito diversity is therefore critical, providing valuable data for risk assessments concerning the (re)emergence of local VBDs. Consequently, this study mainly aimed to understand the spatial and temporal distribution of sylvatic mosquito populations of Cambodia by determining which factors impact on their relative abundance and presence.METHODS: A study was conducted in 12 sites from four forests in Cambodia. All mosquitoes, collected during the dry and rainy seasons, were morphologically identified. The diversity and relative density of mosquito species in each site were calculated along with the influence of meteorological and geographical factors using a quasi-Poisson generalized linear model.
RESULTS: A total of 9392 mosquitoes were collected belonging to 13 genera and 85 species. The most represented genera were Culex, accounting for 46% of collected mosquitoes, and Aedes (42%). Besides being the most abundant species, Culex pseudovishnui and Aedes albopictus, which are known vectors of numerous arboviruses, were present in all sites during both dry and rainy seasons. The presence of mosquito species reported to be zoo-anthropophilic feeders was also observed in both forested and urban areas. Finally, this study demonstrated that altitude, temperature and precipitation impacted the abundance of mosquitoes but also influenced species community composition.
CONCLUSION: The results indicate an important diversity of mosquitoes in the four forests and an influence of meteorological and geographical factors on their community. Additionally, this work highlights in parallel the abundance of species considered to be of medical importance and therefore underlines the high risk of pathogen emergence/re-emergence in the region.

Keywords:  Cambodia; Entomology; Forest; Vector mosquitoes

DOI:  https://doi.org/10.1186/s13071-023-05729-w
PLOS Glob Public Health. 2022 ;2(4): e0000173

Beyond eves and cracks: An interdisciplinary study of socio-spatial variation in urban malaria transmission in Ethiopia.

Claudia Nieto-Sanchez, Stefanie Dens, Kalkidan Solomon, Asgedom Haile, Yue Yuan, Thomas Hawer, Delenasaw Yewhalaw, Adamu Addissie, Koen Peeters Grietens.

During the past century, the global trend of reduced malaria transmission has been concurrent with increasing urbanization. Although urbanization has traditionally been considered beneficial for vector control, the adaptation of malaria vectors to urban environments has created concerns among scientific communities and national vector control programs. Since urbanization rates in Ethiopia are among the highest in the world, the Ethiopian government developed an initiative focused on building multi-storied units organized in condominium housing. This study aimed to develop an interdisciplinary methodological approach that integrates architecture, landscape urbanism, medical anthropology, and entomology to characterize exposure to malaria vectors in this form of housing in three condominiums in Jimma Town. Mosquitoes were collected using light trap catches (LTCs) both indoor and outdoor during 2019's rainy season. Architectural drawings and ethnographic research were superposed to entomological data to detect critical interactions between uses of the space and settlement conditions potentially affecting malaria vector abundance and distribution. A total of 34 anopheline mosquitoes comprising three species (Anopheles gambiae s.l, An. pharoensis and An. coustani complex) were collected during the three months of mosquito collection. Anopheles gambiae s.l, the principal malaria vector in Ethiopia, was the predominant species of all the anophelines collected. Distribution of mosquito breeding sites across scales (household, settlement, urban landscape) is explained by environmental conditions, socio-cultural practices involving modification of existing spaces, and systemic misfits between built environment and territory. Variations in mosquito abundance and distribution in this study were mainly related to standard building practices that ignore the original logics of the territory, deficiency of water and waste disposal management systems, and adaptations of the space to fit heterogeneous lifestyles of residents. Our results indicate that contextualizing malaria control strategies in relation to vector ecology, social dynamics determining specific uses of the space, as well as building and territorial conditions could strengthen current elimination efforts. Although individual housing remains a critical unit of research for vector control interventions, this study demonstrates the importance of studying housing settlements at communal level to capture systemic interactions impacting transmission at the household level and in outdoor areas.

DOI: https://doi.org/10.1371/journal.pgph.0000173
Emerg Infect Dis. 2023 Apr;29(4): 801-805

Effects of Seasonal Conditions on Abundance of Malaria Vector Anopheles stephensi Mosquitoes, Djibouti, 2018-2021.

Alia Zayed, Manal Moustafa, Reham Tageldin, James F Harwood.

  We describe the influence of seasonal meteorologic variations and rainfall events on Anopheles stephensi mosquito populations during a 40-month surveillance study at a US military base in Djibouti. Focusing surveillance and risk mitigation for An. stephensi mosquitoes when climatic conditions are optimal presents an opportunity for malaria prevention and control in eastern Africa.

Keywords:  Anopheles stephensi; Djibouti; distribution; environmental effects; malaria; parasites; rainfall; seasonality; temperature; vector-borne infections

DOI:  https://doi.org/10.3201/eid2904.220549
BMC Genomics. 2023 Mar 24. 24(1): 145

Evaluation of the evolutionary genetics and population structure of Culex pipiens pallens in Shandong province, China based on knockdown resistance (kdr) mutations and the mtDNA-COI gene.

Chuanhui Zang, Xuejun Wang, Peng Cheng, Lijuan Liu, Xiuxia Guo, Haifang Wang, Ziwei Lou, Jingjing Lei, Wenqian Wang, Yiting Wang, Maoqing Gong, Hongmei Liu.

  BACKGROUND: Mosquitoes are important vectors for a range of diseases, contributing to high rates of morbidity and mortality in the human population. Culex pipiens pallens is dominant species of Culex mosquito in northern China and a major vector for both West Nile virus and Bancroftian filariasis. Insecticide application were largely applied to control the mosquito-mediated spread of these diseases, contributing to increasing rates of resistance in the mosquito population. The voltage-gated sodium channel (Vgsc) gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr). While these kdr mutations are known to be critical to pyrethroid resistance, their evolutionary origins remain poorly understood. Clarifying the origins of these mutations is potential to guide further vector control and disease prevention efforts. Accordingly, the present study was designed to study the evolutionary genetics of kdr mutations and their association with the population structure of Cx. p. pallens in Shandong province, China.METHODS: Adult Culex females were collected from Shandong province and subjected to morphological identification under a dissection microscope. Genomic DNA were extracted from the collected mosquitoes, the Vgsc gene were amplified via PCR and sequenced to assess kdr allele frequencies, intron polymorphisms, and kdr codon evolution. In addition, population genetic diversity and related population characteristics were assessed by amplifying and sequencing the mitochondrial cytochrome C oxidase I (COI) gene.
RESULTS: Totally, 263 Cx. p. pallens specimens were used for DNA barcoding and sequencing analyses to assess kdr allele frequencies in nine Culex populations. The kdr codon L1014 in the Vgsc gene identified two non-synonymous mutations (L1014F and L1014S) in the analyzed population. These mutations were present in the eastern hilly area and west plain region of Shandong Province. However, only L1014F mutation was detected in the southern mountainous area and Dongying city of Shandong Province, where the mutation frequency was low. Compared to other cities, population in Qingdao revealed significant genetic differentiation. Spatial kdr mutation patterns are likely attributable to some combination of prolonged insecticide-mediated selection coupled with the genetic isolation of these mosquito populations.
CONCLUSIONS: These data suggest that multiple kdr alleles associated with insecticide resistance are present within the Cx. p. pallens populations of Shandong Province, China. The geographical distributions of kdr mutations in this province are likely that the result of prolonged and extensive insecticide application in agricultural contexts together with frequent mosquito population migrations. In contrast, the low-frequency kdr mutation detected in central Shandong Province populations may originate from the limited selection pressure in this area and the relative genetic isolation. Overall, the study compares the genetic patterns revealed by a functional gene with a neutral marker and demonstrates the combined impact of demographic and selection factors on population structure.

Keywords:  COI; Culex pipiens pallens; Genetic diversity; Kdr; Population structure; Shandong province

DOI:  https://doi.org/10.1186/s12864-023-09243-2
Pest Manag Sci. 2023 Mar 21.

Insecticide resistance compromises the control of Aedes aegypti in Bangladesh.

Hasan Mohammad Al-Amin, Narayan Gyawali, Melissa Graham, Mohammad Shafiul Alam, Audrey Lenhart, Leon E Hugo, Gordana Rašić, Nigel W Beebe, Gregor J Devine.

  BACKGROUND: With no effective drugs or widely available vaccines, dengue control in Bangladesh is dependent on targeting the primary vector Aedes aegypti with insecticides and larval source management. Despite these interventions, the dengue burden is increasing in Bangladesh, and the country experienced its worst outbreak in 2019 with 101,354 hospitalized cases. This may be partially facilitated by the presence of intense insecticide resistance in vector populations. Here, we describe the intensity and mechanisms of resistance to insecticides commonly deployed against Ae. aegypti in Dhaka, Bangladesh.RESULTS: Dhaka Ae. aegypti colonies exhibited high-intensity resistance to pyrethroids. Using CDC bottle assays, we recorded 2 - 24% mortality (recorded at 24 hours) to permethrin and 48 - 94% mortality to deltamethrin, at 10x the diagnostic dose. Bioassays conducted using insecticide-synergist combinations suggested that metabolic mechanisms were contributing to pyrethroid resistance, specifically multi-function oxidases, esterases, and glutathione S-transferases. In addition, kdr alleles were detected, with a high frequency (78-98%) of homozygotes for the V1016G mutation. A large proportion (≤ 74%) of free-flying and resting mosquitoes from Dhaka colonies survived exposure to standard applications of pyrethroid aerosols in an experimental free-flight room. Although that exposure affected Ae. aegypti's immediate host-seeking behavior, the effect was transient in surviving mosquitoes.
CONCLUSION: The intense resistance characterized in this study is likely compromising the operational effectiveness of pyrethroids against Ae. aegypti in Dhaka. Switching to alternative chemical classes may offer a medium-term solution, but ultimately a more sustainable and effective approach to controlling dengue vectors is required. This article is protected by copyright. All rights reserved.

Keywords:  Aedes aegypti; insecticide resistance; kdr; metabolic resistance; operational control; pyrethroids

DOI:  https://doi.org/10.1002/ps.7462
PLOS Glob Public Health. 2022 ;2(9): e0000241

Knowledge, attitudes, and practices of Anopheles mosquito control through insecticide treated nets and community-based health programs to prevent malaria in East Sumba Island, Indonesia.

John T Bandzuh, Kacey C Ernst, Jayleen K L Gunn, Salmon Pandarangga, Linda Rambu Kuba Yowi, Sarah Hobgen, Kerry R Cavanaugh, Rambu Yetti Kalaway, Norlina Rambu Jola Kalunga, Maklon Felipus Killa, Umbu Ho Ara, Christopher K Uejio, Mary H Hayden.

With an estimated 241 million human cases and 627,000 deaths in 2020, malaria remains a significant and ongoing global health challenge. This study employs a qualitative approach to investigate knowledge, attitudes, and practices surrounding mosquito control and prevention methods in East Sumba Regency, Indonesia. While malaria is under control in much of Indonesia, transmission in Sumba Island remains high, with incidence as high as 500 per 1000 population in some areas. A qualitative study was undertaken to explore use of insecticide treated nets, (ITNs), traditional Sumbanese mosquito control methods, and the role of women, integrated health service posts, (posyandu) and community-based health workers (kaders) in combatting malaria and controlling mosquitoes. Focus group discussions (n = 7) were conducted in East Sumba Island stratified by urban/rural location and level of malaria transmission. Key informant interviews (n = 14) were conducted with religious leaders, health workers, and women's group leaders. Results indicate that environmental conditions, such as high temperatures, were common deterrents to regular ITN use. Furthermore, our results suggest that community embedded health workers, kaders, and health service posts, posyandu, play an important role in information dissemination related to mosquitoes and mosquito-borne diseases as well as the distribution and use of ITNs in East Sumba Island. The role of the posyandu and kaders could be expanded to improve malaria prevention by integration with educational campaigns, aiding ITN distributions, and malaria diagnosis and treatment. This study is the first to examine mosquito-borne disease-related knowledge, attitudes, and practices in East Sumba Island, Indonesia. Results could improve mosquito control and malaria prevention by providing insights into local knowledge of Anopheles mosquitoes and malaria as well. Tailoring mosquito control and malaria prevention strategies around local knowledge and perceptions is likely to be more acceptable and sustainable.

DOI: https://doi.org/10.1371/journal.pgph.0000241
Malar J. 2023 Mar 21. 22(1): 104

Mapping current and future thermal limits to suitability for malaria transmission by the invasive mosquito Anopheles stephensi.

Sadie J Ryan, Catherine A Lippi, Oswaldo C Villena, Aspen Singh, Courtney C Murdock, Leah R Johnson.

  BACKGROUND: Anopheles stephensi is a malaria-transmitting mosquito that has recently expanded from its primary range in Asia and the Middle East, to locations in Africa. This species is a competent vector of both Plasmodium falciparum and Plasmodium vivax malaria. Perhaps most alarming, the characteristics of An. stephensi, such as container breeding and anthropophily, make it particularly adept at exploiting built environments in areas with no prior history of malaria risk.METHODS: In this paper, global maps of thermal transmission suitability and people at risk (PAR) for malaria transmission by An. stephensi were created, under current and future climate. Temperature-dependent transmission suitability thresholds derived from recently published species-specific thermal curves were used to threshold gridded, monthly mean temperatures under current and future climatic conditions. These temperature driven transmission models were coupled with gridded population data for 2020 and 2050, under climate-matched scenarios for future outcomes, to compare with baseline predictions for 2020 populations.
RESULTS: Using the Global Burden of Disease regions approach revealed that heterogenous regional increases and decreases in risk did not mask the overall pattern of massive increases of PAR for malaria transmission suitability with An. stephensi presence. General patterns of poleward expansion for thermal suitability were seen for both P. falciparum and P. vivax transmission potential.
CONCLUSIONS: Understanding the potential suitability for An. stephensi transmission in a changing climate provides a key tool for planning, given an ongoing invasion and expansion of the vector. Anticipating the potential impact of onward expansion to transmission suitable areas, and the size of population at risk under future climate scenarios, and where they occur, can serve as a large-scale call for attention, planning, and monitoring.

Keywords:  Anopheles stephensi; Climate change; Malaria; Physiological response

DOI:  https://doi.org/10.1186/s12936-023-04531-4
J Med Entomol. 2023 Mar 22. pii: tjad023. [Epub ahead of print]

Culex (Phenacomyia) lactator (Diptera: Culicidae) in southern Florida, USA: a new subgenus and species country record.

Lawrence E Reeves, Kristin E Sloyer, Kara Tyler-Julian, Rebecca Heinig, Atom Rosales, Candelaria Domingo, Nathan D Burkett-Cadena.

  The Culex subgenus Phenacomyia is a small and poorly studied group of three mosquito species native to the American tropics. Here, we report the first detections of established populations of Culex (Phenacomyia) lactator Dyar & Knab in three counties of southern Florida. Culex lactator was first detected in May 2018 in southern Miami-Dade County, and, at this locality, was collected in subsequent years from 2018 to 2022 as both adults and immatures. Larvae and adults were subsequently collected in 2022, ~175 km northwest of the initial locality at nine sites in Collier and Lee Counties. Identification of specimens collected in these counties as Cx. lactator is supported by molecular analysis and morphological characters of the adult female, male genitalia, and larva. The host associations and vector competence of Cx. lactator have not been extensively studied, and the public health implications, if any, of the addition of this species to Florida's mosquito fauna are unclear. These collections represent the first detections of Cx. lactator, or any Phenacomyia species, in the United States, adding to a trend in which detections of established populations of mosquito species from the American tropics in Florida appear to be increasing.

Keywords:  DNA barcoding; invasive species; morphology; mosquito; taxonomy

DOI:  https://doi.org/10.1093/jme/tjad023
J Med Entomol. 2023 Mar 20. pii: tjad017. [Epub ahead of print]

Trophic preferences of Anopheles coluzzii (Diptera: Culicidae): what implications for malaria vector control in Benin?

Germain Gil Padonou, David Mahouton Zoungbédji, Arthur Sovi, Albert Sourou Salako, Alphonse Keller Konkon, Boulais Yovogan, Constantin Jesukèdè Adoha, Esdras Mahoutin Odjo, Razaki Osse, Haziz Sina, Renaud Govoétchan, Casimir Dossou Kpanou, Hermann W Sagbohan, Lamine Baba-Moussa, Martin Akogbéto.

  The main objective of the present study is to assess the preferences in terms of vertebrate hosts of Anopheles coluzzii, the main malaria vector in the pastoral area of Malanville, Benin, where rice cultivation and livestock are the main source of income for the populations. Adult mosquitoes were collected through pyrethrum spray catch, and human landing catch in two communes in Benin: Malanville, a pastoral area, and Porto-Novo, a nonpastoral area. Molecular species identification was performed through PCR within the Anopheles gambiae complex. Blood meal origin and P. falciparum sporozoite infection were determined using ELISA blood meal and circumsporozoite protein tests, respectively. Overall, 97% of females of An. gambiae s.l. were An. coluzzii, with biting behavior more pronounced outdoors in the pastoral area. In Malanville, the main vertebrate hosts on which females An. coluzzii blood fed were goats (44%), humans (24.29%), bovines (22%), and pigs (1.4%). Our results also showed that single-host blood meals (human: 24.29% or animal: 68%) were mostly observed compared to mixed blood meals (8.58%). The human biting rate (HBR) and P. falciparum sporozoite rate (SR) of An. coluzzii were 66.25 bites/man/night and 0.77%, respectively. However, in the nonpastoral zone (Porto-novo), 93.98% of samples were An. coluzzii. The latter blood-fed mostly (86.84%) on humans, with an estimated HBR of 21.53 b/m/n and SR of 5.81%. The present study revealed an opportunistic and zoophagic behavior of An. coluzzii in the Malanville area with an overall low mean SR.

Keywords:   Anopheles coluzzii ; implication; malaria; trophic preference; vector control

DOI:  https://doi.org/10.1093/jme/tjad017
PLOS Glob Public Health. 2022 ;2(4): e0000227

Household modifications after the indoor residual spraying (IRS) campaign in Mozambique reduce the actual spray coverage and efficacy.

Mercy Opiyo, Ellie Sherrard-Smith, Arlindo Malheia, Arsenio Nhacolo, Charfudin Sacoor, Ariel Nhacolo, Mara Máquina, Luis Jamu, Nelson Cuamba, Quique Bassat, Francisco Saúte, Krijn Paaijmans.

Indoor residual spraying of insecticides (IRS) is a key malaria vector control strategy. Whilst human attitude towards IRS is monitored before or shortly after implementation, human activities leading to the modification of insecticide-treated walls post-IRS are not. This could inadvertently reduce the protective effects of IRS. We monitored the extent of modifications to the sprayed indoor wall surfaces by household owners for six months post-IRS campaigns in two districts targeted for malaria elimination in southern Mozambique. In parallel, we assessed building of any additional rooms onto compounds, and mosquito net use. We quantified the contribution of wall modifications, added rooms, prolonged spray campaigns, and product residual efficacies on actual IRS coverage and relative mosquito bite reduction, using a mechanistic approach. Household owners continually modified insecticide-treated walls and added rooms onto compounds. Household surveys in southern Mozambique showed frequent modification of indoor walls (0-17.2% of households modified rooms monthly) and/or added rooms (0-16.2% of households added rooms monthly). Actual IRS coverage reduced from an assumed 97% to just 39% in Matutuine, but only from 96% to 91% in Boane, translating to 43% and 5.8% estimated increases in relative daily mosquito bites per person. Integrating post-IRS knowledge, attitude, and practice (KAP) surveys into programmatic evaluations to capture these modification and construction trends can help improve IRS program efficiency and product assessment.

DOI: https://doi.org/10.1371/journal.pgph.0000227
PLOS Glob Public Health. 2022 ;2(9): e0000676

Resurgence of malaria in Uganda despite sustained indoor residual spraying and repeated long lasting insecticidal net distributions.

Adrienne Epstein, Catherine Maiteki-Sebuguzi, Jane F Namuganga, Joaniter I Nankabirwa, Samuel Gonahasa, Jimmy Opigo, Sarah G Staedke, Damian Rutazaana, Emmanuel Arinaitwe, Moses R Kamya, Samir Bhatt, Isabel Rodríguez-Barraquer, Bryan Greenhouse, Martin J Donnelly, Grant Dorsey.

Five years of sustained indoor residual spraying (IRS) of insecticide from 2014 to 2019, first using a carbamate followed by an organophosphate, was associated with a marked reduction in the incidence of malaria in five districts of Uganda. We assessed changes in malaria incidence over an additional 21 months, corresponding to a change in IRS formulations using clothianidin with and without deltamethrin. Using enhanced health facility surveillance data, our objectives were to 1) estimate the impact of IRS on monthly malaria case counts at five surveillance sites over a 6.75 year period, and 2) compare monthly case counts at five facilities receiving IRS to ten facilities in neighboring districts not receiving IRS. For both objectives, we specified mixed effects negative binomial regression models with random intercepts for surveillance site adjusting for rainfall, season, care-seeking, and malaria diagnostic. Following the implementation of IRS, cases were 84% lower in years 4-5 (adjusted incidence rate ratio [aIRR] = 0.16, 95% CI 0.12-0.22), 43% lower in year 6 (aIRR = 0.57, 95% CI 0.44-0.74), and 39% higher in the first 9 months of year 7 (aIRR = 1.39, 95% CI 0.97-1.97) compared to pre-IRS levels. Cases were 67% lower in IRS sites than non-IRS sites in year 6 (aIRR = 0.33, 95% CI 0.17-0.63) but 38% higher in the first 9 months of year 7 (aIRR = 1.38, 95% CI 0.90-2.11). We observed a resurgence in malaria to pre-IRS levels despite sustained IRS. The timing of this resurgence corresponded to a change of active ingredient. Further research is needed to determine causality.

DOI: https://doi.org/10.1371/journal.pgph.0000676
PLOS Glob Public Health. 2022 ;2(4): e0000188

Influence of climate variables on dengue fever occurrence in the southern region of Thailand.

Fatima Ibrahim Abdulsalam, Pablo Antunez, Supabhorn Yimthiang, Warit Jawjit.

The 3-5year epidemic cycle of dengue fever in Thailand makes it a major re-emerging public health problem resulting in being a burden in endemic areas. Although the Thai Ministry of Public Health adopted the WHO dengue control strategy, all dengue virus serotypes continue to circulate. Health officers and village health volunteers implement some intervention options but there is a need to ascertain most appropriate (or a combination of) interventions regarding the environment and contextual factors that may undermine the effectiveness of such interventions. This study aims to understand the dengue-climate relationship patterns at the district level in the southern region of Thailand from 2002 to 2018 by examining the statistical association between dengue incidence rate and eight environmental patterns, testing the hypothesis of equal incidence of these. Data on environmental variables and dengue reported cases in Nakhon Si Thammarat province situated in the south of Thailand from 2002 to 2018 were analysed to (1) detect the environmental factors that affect the risk of dengue infectious disease; to (2) determine if disease risk is increasing or decreasing over time; and to (3) identify the high-risk district areas for dengue cases that need to be targeted for interventions. To identify the predictors that have a high and significant impact on reported dengue infection, three steps of analysis were used. First, we used Partial Least Squares (PLS) Regression and Poisson Regression, a variant of the Generalized Linear Model (GLM). Negative co-efficient in correspondence with the PLS components suggests that sea-level pressure, wind speed, and pan evaporation are associated with dengue occurrence rate, while other variables were positively associated. Using the Akaike information criterion in the stepwise GLM, the filtered predictors were temperature, precipitation, cloudiness, and sea level pressure with the standardized coefficients showing that the most influential variable is cloud cover (three times more than temperature and precipitation). Also, dengue occurrence showed a constant negative response to the average increase in sea-level pressure values. In southern Thailand, the predictors that have been locally determined to drive dengue occurrence are temperature, rainfall, cloud cover, and sea-level pressure. These explanatory variables should have important future implications for epidemiological studies of mosquito-borne diseases, particularly at the district level. Predictive indicators guide effective and dynamic risk assessments, targeting pre-emptive interventions.

DOI: https://doi.org/10.1371/journal.pgph.0000188
PLOS Glob Public Health. 2023 ;3(3): e0001683

The impact of hydropower dam construction on malaria incidence: Space-time analysis in the Brazilian Amazon.

Igor C Johansen, Emilio F Moran, Marcelo U Ferreira.

During the first two decades of the 21st century, Brazil carried out massive public investments on infrastructure projects, such as large hydropower dams, with potential impact on population health. Here we characterize local malaria transmission and its potential spread during the construction of three large hydropower dams in the Brazilian Amazon. We focus on Porto Velho (PVH), in Rondônia state, where the Santo Antônio and Jirau dams were built (2008-2013), and Altamira region (ATM), in Pará state, where the construction of the Belo Monte dam took place (2011-2016). Analyzed data cover 4 years before, 6 years during, and 4 years after each dam construction. In total, we utilized malaria case notifications entered into the electronic malaria notification system of the Ministry of Health of Brazil between January 2004 and December 2020 (n = 39,977,167 malaria notifications). First, we used Interrupted Time-Series Analysis (ITSA) to assess temporal changes in malaria notifications in the study sites. Then, we conducted a space-time cluster analysis to investigate the potential of malaria spread from the study sites (sources) to elsewhere (sinks). Finally, we present the sociodemographic characteristics of exported cases over time using multivariate logistic regressions. Our results show that there was no upsurge in malaria cases in the study sites and exported cases did not trigger outbreaks in other localities. Exported malaria infections originating from PVH and ATM were typically found in working age literate males involved in mining, farming or traveling. We suggest that efficient control measures, such as ensuring timely diagnosis and treatment; fostering integrated vector control; promoting health education; and prevention, detection and containment of outbreaks, if properly implemented and sustained, may prevent local and introduced malaria outbreaks during and after hydropower dam construction in the Amazon.

DOI: https://doi.org/10.1371/journal.pgph.0001683
PLOS Glob Public Health. 2023 ;3(1): e0001292

Tracking district-level performance in the context of achieving zero indigenous case status by 2027.

Chander Prakash Yadav, Syed Shah Areeb Hussain, Sanjeev Gupta, Praveen K Bharti, Manju Rahi, Amit Sharma.

India has committed to zero indigenous malaria cases by 2027 and elimination by 2030. Of 28 states and 8 union territories of India, eleven states were targeted to reach the elimination phase by 2020. However, state-level epidemiology indicates that several states of India may not be on the optimum track, and few goals set in National Framework for Malaria Elimination (NFME) for 2020 remain to be addressed. Therefore, tracking the current progress of malaria elimination in India at the district level, and identifying districts that are off track is important in understanding possible shortfalls to malaria elimination. Annual malaria case data from 2017-20 of 686 districts of India were obtained from the National Center for Vector-Borne Diseases Control (NCVBDC) and analysed to evaluate the performance of districts to achieve zero case status by 2027. A district's performance was evaluated by calculating the annual percentage change in the total number of malaria cases for the years 2018, 2019 and 2020 considering the previous year as a base year. The mean, median and maximum of these annual changes were then used to project the number of malaria cases in 2027. Based on these, districts were classified into four groups: 1) districts that are expected to reach zero case status by 2027, 2) districts that would achieve zero case status between 2028 and 2030, 3) districts that would arrive at zero case status after 2030, and 4) districts where malaria cases are on the rise. Analysis suggest, a cohort of fifteen districts require urgent modification or improvement in their malaria control strategies by identifying foci of infection and customizing interventions. They may also require new interventional tools that are being developed recently so that malaria case reduction over the years may be increased.

DOI: https://doi.org/10.1371/journal.pgph.0001292
PLOS Glob Public Health. 2021 ;1(10): e0000024

Economic impact of dengue in Singapore from 2010 to 2020 and the cost-effectiveness of Wolbachia interventions.

Stacy Soh, Soon Hoe Ho, Annabel Seah, Janet Ong, Borame Sue Dickens, Ken Wei Tan, Joel Ruihan Koo, Alex R Cook, Kelvin Bryan Tan, Shuzhen Sim, Lee Ching Ng, Jue Tao Lim.

The release of Wolbachia-infected mosquitoes is a promising disease intervention strategy that aims to control dengue and other arboviral infections. While early field trials and modelling studies suggest promising epidemiological and entomological outcomes, the overall cost effectiveness of the technology is not well studied in a resource rich setting nor under the suppression approach that aims to suppress the wild-type mosquito population through the release of Wolbachia-infected males. We used economical and epidemiological data from 2010 to 2020 to first ascertain the economic and health costs of dengue in Singapore, a high income nation where dengue is hyper-endemic. The hypothetical cost effectiveness of a national Wolbachia suppression program was then evaluated historically from 2010 to 2020. We estimated that the average economic impact of dengue in Singapore from 2010 to 2020 in constant 2010US$ ranged from $1.014 to $2.265 Billion. Using empirically derived disability weights, we estimated a disease burden of 7,645-21,262 DALYs from 2010-2020. Under an assumed steady-state running cost of a national Wolbachia suppression program in Singapore, we conservatively estimate that Wolbachia would cost an estimated $50,453-$100,907 per DALYs averted and would lead to an estimated $329.40 Million saved in economic costs over 2010 to 2020 under 40% intervention efficacy. Wolbachia releases in Singapore are expected to be highly cost-effective and its rollout must be prioritised to reduce the onward spread of dengue.

DOI: https://doi.org/10.1371/journal.pgph.0000024
Infect Dis Poverty. 2023 Mar 24. 12(1): 26

Climate change and Aedes albopictus risks in China: current impact and future projection.

Hongmei Liu, Xiaodan Huang, Xiuxia Guo, Peng Cheng, Haifang Wang, Lijuan Liu, Chuanhui Zang, Chongxing Zhang, Xuejun Wang, Guofa Zhou, Maoqing Gong.

  BACKGROUND: Future distribution of dengue risk is usually predicted based on predicted climate changes using general circulation models (GCMs). However, it is difficult to validate the GCM results and assess the uncertainty of the predictions. The observed changes in climate may be very different from the GCM results. We aim to utilize trends in observed climate dynamics to predict future risks of Aedes albopictus in China.METHODS: We collected Ae. albopictus surveillance data and observed climate records from 80 meteorological stations from 1970 to 2021. We analyzed the trends in climate change in China and made predictions on future climate for the years 2050 and 2080 based on trend analyses. We analyzed the relationship between climatic variables and the prevalence of Ae. albopictus in different months/seasons. We built a classification tree model (based on the average of 999 runs of classification and regression tree analyses) to predict the monthly/seasonal Ae. albopictus distribution based on the average climate from 1970 to 2000 and assessed the contributions of different climatic variables to the Ae. albopictus distribution. Using these models, we projected the future distributions of Ae. albopictus for 2050 and 2080.
RESULTS: The study included Ae. albopictus surveillance from 259 sites in China found that winter to early spring (November-February) temperatures were strongly correlated with Ae. albopictus prevalence (prediction accuracy ranges 93.0-98.8%)-the higher the temperature the higher the prevalence, while precipitation in summer (June-September) was important predictor for Ae. albopictus prevalence. The machine learning tree models predicted the current prevalence of Ae. albopictus with high levels of agreement (accuracy > 90% and Kappa agreement > 80% for all 12 months). Overall, winter temperature contributed the most to Ae. albopictus distribution, followed by summer precipitation. An increase in temperature was observed from 1970 to 2021 in most places in China, and annual change rates varied substantially from -0.22 ºC/year to 0.58 ºC/year among sites, with the largest increase in temperature occurring from February to April (an annual increase of 1.4-4.7 ºC in monthly mean, 0.6-4.0 ºC in monthly minimum, and 1.3-4.3 ºC in monthly maximum temperature) and the smallest in November and December. Temperature increases were lower in the tropics/subtropics (1.5-2.3 ºC from February-April) compared to the high-latitude areas (2.6-4.6 ºC from February-April). The projected temperatures in 2050 and 2080 by this study were approximately 1-1.5 °C higher than those projected by GCMs. The estimated current Ae. albopictus risk distribution had a northern boundary of north-central China and the southern edge of northeastern China, with a risk period of June-September. The projected future Ae. albopictus risks in 2050 and 2080 cover nearly all of China, with an expanded risk period of April-October. The current at-risk population was estimated to be 960 million and the future at-risk population was projected to be 1.2 billion.
CONCLUSIONS: The magnitude of climate change in China is likely to surpass GCM predictions. Future dengue risks will expand to cover nearly all of China if current climate trends continue.

Keywords:  Aedes albopictus; Observed climate change; Observed risks distribution; Projected future climate; Projected future risk distribution

DOI:  https://doi.org/10.1186/s40249-023-01083-2
PLOS Glob Public Health. 2022 ;2(8): e0000239

Malaria outbreak facilitated by engagement in activities near swamps following increased rainfall and limited preventive measures: Oyam District, Uganda.

Maureen Katusiime, Steven Ndugwa Kabwama, Gerald Rukundo, Benon Kwesiga, Lilian Bulage, Damian Rutazaana, Alex Riolexus Ario, Julie Harris.

In April 2019, the District Health Office of Oyam District, Uganda reported an upsurge in malaria cases exceeding expected epidemic thresholds, requiring outbreak response. We investigated the scope of outbreak and identified exposures for transmission to inform control measures. A confirmed case was a positive malaria rapid diagnostic test or malaria microscopy from 1 January-30 June 2019 in a resident or visitor of Acaba Sub-county, Oyam District. We reviewed medical records at health facilities to get case-patients. We conducted entomological and environmental assessments to determine vector density, and identify aquatic Anopheles habitats, conducted a case-control study to determine exposures associated with illness. Of 9,235 case-patients (AR = 33%), females (AR = 38%) were more affected than males (AR = 20%) (p<0.001). Children <18 years were more affected (AR = 37%) than adults (p<0.001). Among 83 case-patients and 83 asymptomatic controls, 65 (78%) case-patients and 33 (40%) controls engaged in activities <500m from a swamp (ORMH = 12, 95%CI 3.6-38); 18 (22%) case-patients and four (5%) controls lived <500m from rice irrigation sites (ORMH = 8.2, 95%CI 1.8-36); and 23 (28%) case-patients and four (5%) controls had water pools <100m from household for 3-5 days after rainfall (ORMH = 7.3, 95%CI 2.2-25). Twenty three (28%) case-patients and four (5%) controls did not sleep under bed nets the previous night (ORMH = 20, 95%CI 2.7-149); 68 (82%) case-patients and 43(52%) controls did not wear long-sleeved clothes during evenings (ORMH = 9.3, 95%CI 2.8-31). Indoor resting vector density was 4.7 female mosquitoes/household/night. All Anopheles aquatic habitats had Anopheles larvae. Weekly rainfall in 2019 was heavier (6.0±7.2mm) than same period in 2018 (1.8±1.8mm) (p = 0.006). This outbreak was facilitated by Anopheles aquatic habitats near homes created by human activities, following increased rainfall compounded by inadequate use of individual preventive measures. We recommended awareness on use of insecticide-treated bed nets, protective clothing, and avoiding creation of Anopheles aquatic habitats.

DOI: https://doi.org/10.1371/journal.pgph.0000239
BMC Infect Dis. 2023 Mar 22. 23(1): 177

Epidemiological profile of arboviruses in two different scenarios: dengue circulation vs. dengue, chikungunya and Zika co-circulation.

Pablo Cantalice Santos Farias, André Filipe Pastor, Juliana Prado Gonçales, Iasmyn Dayanne Santos do Nascimento, Ellida Suellen de Souza Ferraz, Thaísa Regina Rocha Lopes, Rodrigo Feliciano do Carmo, Maria Rosângela Cunha Duarte Côelho, José Valter Joaquim Silva Júnior.

  BACKGROUND: The severity and distribution of dengue virus (DENV) infections have been attributed to a complex interaction among viral, host and environmental factors. Herein, we investigated the influence of chikungunya (CHIKV) and Zika (ZIKV) viruses on the epidemiological profile of dengue cases, using Recife, Pernambuco state, Brazil, as a study model. In addition, we described and compared the epidemiological profile related to each arbovirus (DENV vs. CHIKV vs. ZIKV).METHODS: All cases of dengue, chikungunya and Zika reported to the Pernambuco Health Department in 2011-2013 (DENV circulation) and 2016-2018 (DENV, CHIKV and ZIKV co-circulation) were included in our study. The cases were classified by sex, age and race/color and their distribution was analyzed by the χ2 test. Furthermore, the data were also analyzed for co-infections. Temperature, humidity and rainfall data were analyzed using one-way ANOVA and paired t-test.
RESULTS: During 2011-2013, 15,315 dengue cases were diagnosed, most of them female, brown and 20-29 age group. Between 2016 and 2018, 15,870 dengue cases were described, which presented the same profile described above. In the two triennia, the female/male dengue ratio fluctuated significantly, ranging from 1.07 to 1.52. Regarding chikungunya, 7076 cases were reported, most of them female and brown. The female/male ratio also fluctuated significantly, ranging from 1.62 to 2.1. Two main age groups were observed in chikungunya: ≤ 19 years (minority of diagnoses) and ≥ 20 years (majority of diagnoses). In the same triennium, 266 Zika cases were reported to the Pernambuco Health Department, mainly in females and in the 0-9 and 20-39 age groups. In general, 119 co-infections were identified: 117 DENV-CHIKV, 1 CHIKV-ZIKV and 1 DENV-CHIKV-ZIKV. Concerning climate data, only the humidity in 2011 was significantly different from the other years.
CONCLUSION: The epidemiological profile of dengue cases did not change after the introduction of CHIKV and ZIKV. Females were the most diagnosed with dengue, chikungunya or Zika, however we found important differences in the age profile of these arboviruses, which should be considered by public health policies, as well as investigated in future studies of virus-host interaction.

Keywords:  Arbovirus co-circulation; Brazil; Brown; Female; Public Health

DOI:  https://doi.org/10.1186/s12879-023-08139-6
PLOS Glob Public Health. 2022 ;2(3): e0000071

Malaria prevalence, knowledge and associated factors among household heads in Maygaba town, Ethiopia.

Tsegay Gebremaryam Yhdego, Asnake Desalegn Gardew, Fitsum Tigu Yifat.

Malaria remains a leading public health issue in Ethiopia, despite wide use of insecticide-treated mosquito nets (ITNs). Consistent use of ITNs reduces malaria transmission by 90%. However, coverage and proper use of ITNs are the major challenge for most rural settings of Ethiopia. We assessed the prevalence of malaria, ITNs use and associated factors among household heads in Maygaba town, northwest Ethiopia. A cross-sectional study was carried out among 403 households using a structured questionnaire. Blood samples were collected from household heads and examined for malaria parasites by microscopy. Chi-square test and logistic regression were used to check the association between the dependent and independent variables. Of the 403 blood samples, 19 (4.7%) had malaria parasites (12 cases of Plasmodium falciparum and 7 cases of Plasmodium vivax). Majority of the respondents were aware of the cause, communicability, preventability and curability of the disease. ITNs use was identified as the main malaria prevention method. About 64% (257) of the respondents owned ITNs, of which, 66.9% (172) consistently slept under the nets during the peak malaria season. Majority of the respondents (83.6%) had positive attitude towards the benefit of sleeping under ITNs. Educational status and livelihood of the respondents had statistically significant (p < 0.05) association with malaria knowledge. Malaria infection was significantly (p < 0.05) higher among household heads aged 18-30 years (AOR = 5.982; 95% CI = 1.715-20.863). Moderate prevalence rate and acceptable ITNs ownership was detected among the community of Maygaba town. However, a considerable proportion had misconceptions about the use of ITNs. A comprehensive malaria control measures and health education about the use of ITNs should be in place for effective prevention and control of malaria in the locality.

DOI: https://doi.org/10.1371/journal.pgph.0000071
Rev Inst Med Trop Sao Paulo. 2023 ;pii: S0036-46652023000100603. [Epub ahead of print]65 e20

First official record of Aedes (Stegomyia) albopictus (Diptera: Culicidae) in the Acre State, Northern Brazil.

Ricardo da Costa Rocha, Acigelda da Silva Cardoso, Janis Lunier de Souza, Eliana da Silva Pereira, Marcio Fernandes de Amorim, Maria Socorro Martins de Souza, Cleomar de Lima Medeiros, Maria Francisca Mendes Monteiro, Dionatas Ulises de Oliveira Meneguetti, Marcia Bicudo de Paula, Andreia Fernandes Brilhante, Tamara Nunes Lima-Camara.

Aedes (Stegomyia) albopictus (Skuse, 1854) was reported in Brazil for the first time in 1986 and has shown marked expansion throughout the Brazilian territory. During a routine activity to control dengue fever conducted by the Division of Entomology of the Municipal Health Department in Rio Branco city, adults and immatures of Culicidae were collected in a peri-urban area. The identified Culicidae forms indicated that they belonged to the species Ae. albopictus. This is the first official record of the presence of Ae. albopictus in the Acre State, confirming its current presence in all Brazilian states.

DOI: https://doi.org/10.1590/S1678-9946202365020
Sci Rep. 2023 Mar 20. 13(1): 4538

Malaria hotspots and climate change trends in the hyper-endemic malaria settings of Mizoram along the India-Bangladesh borders.

Pachuau Lalmalsawma, K Balasubramani, Meenu Mariya James, Lalfakzuala Pautu, Kumar Arun Prasad, Devojit Kumar Sarma, Praveen Balabaskaran Nina.

India has made tremendous progress in reducing malaria mortality and morbidity in the last decade. Mizoram State in North-East India is one of the few malaria-endemic regions where malaria transmission has continued to remain high. As Mizoram shares international borders with Bangladesh and Myanmar, malaria control in this region is critical for malaria elimination efforts in all the three countries. For identifying hotspots for targeted intervention, malaria data from 385 public health sub-centers across Mizoram were analyzed in the Geographic Information System. Almost all the sub-centers reporting high Annual Parasite Index (> 10) are located in Mizoram's districts that border Bangladesh. Getis-Ord Gi* statistic shows most of the sub-centers located along the Bangladesh border in the Lawngtlai and Lunglei districts to be the malaria hotspots. The hotspots also extended into the Mamit and Siaha districts, especially along the borders of Lawngtlai and Lunglei. Analysis of terrain, climatic, and land use/land cover datasets obtained from the Global Modelling and Assimilation Office and satellite images show Mizoram's western part (Lawngtlai, Lunglei, and Mamit districts) to experience similar topographic and climatic conditions as the bordering Rangamati district in the Chittagong division of Bangladesh. Climatic trends in this region from 1981 to 2021, estimated by the Mann-Kendall test and Sen's slope estimates, show an increasing trend in minimum temperature, relative humidity, rainfall, and the associated shift of climatic pattern (temperate to tropical monsoon) could facilitate malaria transmission. The quasi-Poisson regression model estimates a strong association (p < 0.001) between total malaria cases, temperature range, and elevation. The Kruskal-Wallis H test shows a statistically significant association between malaria cases and forest classes (p < 0.001). A regional coordination and strategic plan are required to eliminate malaria from this hyper-endemic malaria region of North-East India.

DOI: https://doi.org/10.1038/s41598-023-31632-6
PLOS Glob Public Health. 2022 ;2(7): e0000627

Community-based house improvement for malaria control in southern Malawi: Stakeholder perceptions, experiences, and acceptability.

Tinashe A Tizifa, Steven Gowelo, Alinune N Kabaghe, Robert S McCann, Tumaini Malenga, Richard M Nkhata, Asante Kadama, Yankho Chapeta, Willem Takken, Kamija S Phiri, Michele van Vugt, Henk van den Berg, Lucinda Manda-Taylor.

House improvement (HI) refers to the full screening or closing of openings such as windows, doors, and eaves, as well as the installation of ceilings, to reduce mosquito-human contact indoors. HI is a viable supplementary intervention that reduces malaria transmission further than the existing strategies alone. In Malawi, HI has not been widely implemented and evaluated for malaria control. Concerns about lack of local evidence, durability in different epidemiological and cultural settings, and the cost of large-scale implementation are among the reasons the strategy is not utilised in many low-income countries. This study assessed community perceptions, experiences, and acceptability of community-led HI in Chikwawa district, southern Malawi. This was a qualitative study where separate focus group discussions were conducted with members from the general community (n = 3); health animators (n = 3); and HI committee members (n = 3). In-depth interviews were conducted with community members (n = 20), and key-informant interviews were conducted with health surveillance assistants and chiefs (n = 23). All interviews were transcribed and coded before performing a thematic content analysis to identify the main themes. Coded data were analysed using Nvivo 12 Plus software. Study participants had a thorough understanding of HI. Participants expressed satisfaction with HI, and they reported enabling factors to HI acceptability, such as the reduction in malaria cases in their villages and the safety and effectiveness of HI use. Participants also reported barriers to effective HI implementation, such as the unavailability and inaccessibility of some HI materials, as well as excessive heat and darkness in HI houses compared to non-HI houses. Participants indicated that they were willing to sustain the intervention but expressed the need for strategies to address barriers to ensure the effectiveness of HI. Our results showed the high knowledge and acceptability of HI by participants in the study area. Intensive and continued health education and community engagement on the significance of HI could help overcome the barriers and improve the acceptability and sustainability of the intervention.

DOI: https://doi.org/10.1371/journal.pgph.0000627
PLOS Glob Public Health. 2022 ;2(12): e0000474

Assessing the effectiveness of malaria interventions at the regional level in Ghana using a mathematical modelling application.

Timothy Awine, Sheetal P Silal.

Supporting malaria control with interfaced applications of mathematical models that enables investigating effectiveness of various interventions as well as their cost implications could be useful. Through their usage for planning, these applications may improve the prospects of attaining various set targets such as those of the National Strategic Plan policies for malaria control in Ghana. A malaria model was adapted and used for simulating the incidence of malaria in various regions of Ghana. The model and its application were developed by the Modelling and Simulation Hub Africa and calibrated using district level data in Ghana from 2012 to 2018. Average monthly rainfall at the zonal level was fitted to trigonometric functions for each ecological zone using least squares approach. These zonal functions were then used as forcing functions. Subsequently, various intervention packages were investigated to observe their impact on averting malaria incidence by 2030. Increased usage of bednets but not only coverage levels, predicted a significant proportion of cases of malaria averted in all regions. Whereas, improvements in the health system by way of health seeking, testing and treatment predicted a decline in incidence largely in all regions. With an increased coverage of SMC, to include higher age groups, a modest proportion of cases could be averted in populations of the Guinea savannah. Indoor residual spraying could also benefit populations of the Transitional forest and Coastal savannah as its impact is significant in averting incidence. Enhancing bednet usage to at least a doubling of the current usage levels and deployed in combination with various interventions across regions predicted significant reductions, in malaria incidence. Regions of the Transitional forest and Coastal savannah could also benefit from a drastic decline in incidence following a gradual introduction of indoor residual spraying on a sustained basis.

DOI: https://doi.org/10.1371/journal.pgph.0000474
Emerg Infect Dis. 2023 Apr;29(4): 826-830

Chikungunya Outbreak in Country with Multiple Vectorborne Diseases, Djibouti, 2019-2020.

Emilie Javelle, Franck de Laval, Guillaume André Durand, Aissata Dia, Cécile Ficko, Aurore Bousquet, Deborah Delaune, Sébastien Briolant, Audrey Mérens, Constance Brossier, Hervé Pommier, Florian Gala, Alain Courtiol, Quentin Savreux, Sébastien Sicard, Jean-Philippe Sanchez, Francis Robin, Fabrice Simon, Xavier de Lamballerie, Gilda Grard, Isabelle Leparc-Goffart, Vincent Pommier de Santi.

  During 2019-2020, a chikungunya outbreak occurred in Djibouti City, Djibouti, while dengue virus and malaria parasites were cocirculating. We used blotting paper to detect arbovirus emergence and confirm that it is a robust method for detecting and monitoring arbovirus outbreaks remotely.

Keywords:  Africa; Chikungunya virus; Djibouti; arboviruses; chikungunya; dengue fever; dengue virus; malaria; military personnel; outbreak; parasites; vector-borne infections; viruses

DOI:  https://doi.org/10.3201/eid2904.221850
PLOS Glob Public Health. 2022 ;2(11): e0000747

Stratification of malaria incidence in Papua New Guinea (2011-2019): Contribution towards a sub-national control policy.

Osama Seidahmed, Sharon Jamea, Serah Kurumop, Diana Timbi, Leo Makita, Munir Ahmed, Tim Freeman, William Pomat, Manuel W Hetzel.

Malaria risk in Papua New Guinea (PNG) is highly heterogeneous, between and within geographical regions, which is operationally challenging for control. To enhance targeting of malaria interventions in PNG, we investigated risk factors and stratified malaria incidence at the level of health facility catchment areas. Catchment areas and populations of 808 health facilities were delineated using a travel-time accessibility approach and linked to reported malaria cases (2011-2019). Zonal statistics tools were used to calculate average altitude and air temperature in catchment areas before they were spatially joined with incidence rates. In addition, empirical Bayesian kriging (EBK) was employed to interpolate incidence risk strata across PNG. Malaria annual incidence rates are, on average, 186.3 per 1000 population in catchment areas up to 600 m, dropped to 98.8 at (800-1400) m, and to 24.1 cases above 1400 m altitude. In areas above the two altitudinal thresholds 600m and 1400m, the average annual temperature drops below 22°C and 17°C, respectively. EBK models show very low- to low-risk strata (<100 cases per 1000) in the Highlands, National Capital District and Bougainville. In contrast, patches of high-risk (>200 per 1000) strata are modelled mainly in Momase and Islands Regions. Besides, strata with moderate risk (100-200) predominate throughout the coastal areas. While 35.7% of the PNG population (estimated 3.33 million in 2019) lives in places at high or moderate risk of malaria, 52.2% (estimated 4.88 million) resides in very low-risk areas. In five provinces, relatively large proportions of populations (> 50%) inhabit high-risk areas: New Ireland, East and West New Britain, Sandaun and Milne Bay. Incidence maps show a contrast in malaria risk between coastal and inland areas influenced by altitude. However, the risk is highly variable in low-lying areas. Malaria interventions should be guided by sub-national risk levels in PNG.

DOI: https://doi.org/10.1371/journal.pgph.0000747
PLOS Glob Public Health. 2022 ;2(6): e0000262

What Africa can do to accelerate and sustain progress against malaria.

Fredros Okumu, Margaret Gyapong, Núria Casamitjana, Marcia C Castro, Maurice A Itoe, Friday Okonofua, Marcel Tanner.

After a longstanding global presence, malaria is now largely non-existent or suppressed in most parts of the world. Today, cases and deaths are primarily concentrated in sub-Saharan Africa. According to many experts, this persistence on the African continent reflects factors such as resistance to insecticides and drugs as well as insufficient access to essential commodities such as insecticide-treated nets and effective drugs. Crucially, however, this narrative ignores many central weaknesses in the fight against malaria and instead reinforces a narrow, commodity-driven vision of disease control. This paper therefore describes the core challenges hindering malaria programs in Africa and highlights key opportunities to rethink current strategies for sustainable control and elimination. The epidemiology of malaria in Africa presents far greater challenges than elsewhere and requires context-specific initiatives tailored to national and sub-national targets. To sustain progress, African countries must systematically address key weaknesses in its health systems, improve the quality and use of data for surveillance-responses, improve both technical and leadership competencies for malaria control, and gradually reduce overreliance on commodities while expanding multisectoral initiatives such as improved housing and environmental sanitation. They must also leverage increased funding from both domestic and international sources, and support pivotal research and development efforts locally. Effective vaccines and drugs, or other potentially transformative technologies such as genedrive modified mosquitoes, could further accelerate malaria control by complementing current tools. However, our underlying strategies remain insufficient and must be expanded to include more holistic and context-specific approaches critical to achieve and sustain effective malaria control.

DOI: https://doi.org/10.1371/journal.pgph.0000262
PLOS Glob Public Health. 2022 ;2(5): e0000210

Rethinking human resources and capacity building needs for malaria control and elimination in Africa.

Halima Mwenesi, Charles Mbogo, Núria Casamitjana, Marcia C Castro, Maurice A Itoe, Friday Okonofua, Marcel Tanner.

Despite considerable success in controlling malaria worldwide, progress toward achieving malaria elimination has largely stalled. In particular, strategies to overcome roadblocks in malaria control and elimination in Africa are critical to achieving worldwide malaria elimination goals-this continent carries 94% of the global malaria case burden. To identify key areas for targeted efforts, we combined a comprehensive review of current literature with direct feedback gathered from frontline malaria workers, leaders, and scholars from Africa. Our analysis identified deficiencies in human resources, training, and capacity building at all levels, from research and development to community involvement. Addressing these needs will require active and coordinated engagement of stakeholders as well as implementation of effective strategies, with malaria-endemic countries owning the relevant processes. This paper reports those valuable identified needs and their concomitant opportunities to accelerate progress toward the goals of the World Health Organization's Global Technical Strategy for Malaria 2016-2030. Ultimately, we underscore the critical need to re-think current approaches and expand concerted efforts toward increasing relevant human resources for health and capacity building at all levels if we are to develop the relevant competencies necessary to maintain current gains while accelerating momentum toward malaria control and elimination.

DOI: https://doi.org/10.1371/journal.pgph.0000210
Acta Trop. 2023 Mar 17. pii: S0001-706X(23)00079-7. [Epub ahead of print] 106892

Environmental and socio-economic determinants of the occurrence of malaria clusters in Colombia.

Johanna Tapias Rivera, Juan David Gutiérrez.

  This study identifies the environmental and socio-economic determinants of clusters of high malaria incidence in Colombia during the period of 2008-2019. The malaria cases were obtained from the National System of Surveillance in Public Health, with 798,897 cases reported in the 986 Colombian municipalities evaluated during the study period. Spatial autocorrelation of incidence was examined with global and local indices. Clusters were identified in the Amazon, Pacific, and Uraba-Bajo Cauca-Alto Sinú regions. The factors associated with a municipality belonging to a high-incidence cluster were identified using a logistic regression model with mixed effects and showed a positive association for the variables (forest coverage and minimum multi-year average rainfall). An inverse relationship was observed for aqueduct coverage and the odds of belonging to a cluster. A 1% increase in forest coverage was associated with a 4.2% increase in the odds of belonging to a malaria cluster. The association with minimum multi-year average rainfall was positive (OR = 1.0011; 95% CI 1.0005-1.0027). A 1% increase in aqueduct coverage was associated with a 4.3% decrease in the odds of belonging to malaria cluster. The identification of malaria cluster determinants in Colombia could help guide surveillance and disease control policies.

Keywords:  cluster; forest coverage; malaria; municipality; rainfall

DOI:  https://doi.org/10.1016/j.actatropica.2023.106892
PLOS Glob Public Health. 2022 ;2(8): e0000807

Plasmodium falciparum importation does not sustain malaria transmission in a semi-arid region of Kenya.

Christine F Markwalter, Diana Menya, Amy Wesolowski, Daniel Esimit, Gilchrist Lokoel, Joseph Kipkoech, Elizabeth Freedman, Kelsey M Sumner, Lucy Abel, George Ambani, Hannah R Meredith, Steve M Taylor, Andrew A Obala, Wendy P O'Meara.

Human movement impacts the spread and transmission of infectious diseases. Recently, a large reservoir of Plasmodium falciparum malaria was identified in a semi-arid region of northwestern Kenya historically considered unsuitable for malaria transmission. Understanding the sources and patterns of transmission attributable to human movement would aid in designing and targeting interventions to decrease the unexpectedly high malaria burden in the region. Toward this goal, polymorphic parasite genes (ama1, csp) in residents and passengers traveling to Central Turkana were genotyped by amplicon deep sequencing. Genotyping and epidemiological data were combined to assess parasite importation. The contribution of travel to malaria transmission was estimated by modelling case reproductive numbers inclusive and exclusive of travelers. P. falciparum was detected in 6.7% (127/1891) of inbound passengers, including new haplotypes which were later detected in locally-transmitted infections. Case reproductive numbers approximated 1 and did not change when travelers were removed from transmission networks, suggesting that transmission is not fueled by travel to the region but locally endemic. Thus, malaria is not only prevalent in Central Turkana but also sustained by local transmission. As such, interrupting importation is unlikely to be an effective malaria control strategy on its own, but targeting interventions locally has the potential to drive down transmission.

DOI: https://doi.org/10.1371/journal.pgph.0000807