bims-mosdis 2022-05-15 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2022‒05‒15
twenty-two papers selected by
Richard Halfpenny
Staffordshire University

Relationship between temperature and Anopheles gambiae sensu lato mosquitoes' susceptibility to pyrethroids and expression of metabolic enzymes.
Yearly variations of the genetic structure of Aedes aegypti (Linnaeus) (Diptera: Culicidae) in the Philippines (2017-2019).
Outbreak Investigation: Jamestown Canyon Virus Surveillance in Field-Collected Mosquitoes (Diptera: Culicidae) From Wisconsin, USA, 2018-2019.
Natural Aedes-Borne Virus Infection Detected in Male Adult Aedes aegypti (Diptera: Culicidae) Collected From Urban Settings in Mérida, Yucatán, México.
Evaluation of the effectiveness of the california mosquito-borne virus surveillance & response plan, 2009-2018.
[Sustainable and precise Anopheles control to maintain malaria elimination in China].
Vector control in China, from malaria endemic to elimination and challenges ahead.
The combined impact of LLINs, house screening, and pull-push technology for improved malaria control and livelihoods in rural Ethiopia: study protocol for household randomised controlled trial.
Snow-Covered Tires Generate Microhabitats That Enhance Overwintering Survival of Aedes albopictus (Diptera: Culicidae) in the Midwest, USA.
Spatial dispersal of <em>Aedes albopictus</em> mosquitoes captured by the modified sticky ovitrap in Selangor, Malaysia.
Blood feeding habits of mosquitoes: hardly a bite in South America.
A persistent behavioral state enables sustained predation of humans by mosquitoes.
Multi-omics analysis identifies a CYP9K1 haplotype conferring pyrethroid resistance in the malaria vector Anopheles funestus in East Africa.
Model to support intervention prioritization for the control of Aedes aegypti in Brazil: a multi-criteria approach.
Estimation of Plasmodium falciparum transmission using multiepitope chimeric antigen in the postelimination phase in Yunnan, China.
Dengue: A Growing Problem With New Interventions.
Malaria from hyperendemicity to elimination along international borders in Yunnan, China during 2003‒2020: a case study.
Malaria transmission structure in the Peruvian Amazon through antibody signatures to Plasmodium vivax.
Understanding the epidemiology, clinical characteristics, knowledge and barriers to treatment and prevention of malaria among returning international laborers in northern Vietnam: a mixed-methods study.
Assessment of the Costs Related to West Nile Virus Monitoring in Lombardy Region (Italy) between 2014 and 2018.
Receptivity to malaria: meaning and measurement.
[Harder maintained than achieved: Challenges of maintaining malaria-free in China].

Parasit Vectors. 2022 May 08. 15(1): 163

Relationship between temperature and Anopheles gambiae sensu lato mosquitoes' susceptibility to pyrethroids and expression of metabolic enzymes.

Thomas Peprah Agyekum, John Arko-Mensah, Paul Kingsley Botwe, Jonathan Nartey Hogarh, Ibrahim Issah, Samuel Kweku Dadzie, Duah Dwomoh, Maxwell Kelvin Billah, Thomas Robins, Julius Najah Fobil.

  BACKGROUND: Malaria remains one of the most devastating diseases globally, and the control of mosquitoes as the vector is mainly dependent on chemical insecticides. Elevated temperatures associated with future warmer climates could affect mosquitoes' metabolic enzyme expression and increase insecticide resistance, making vector control difficult. Understanding how mosquito rearing temperatures influence their susceptibility to insecticide and expression of metabolic enzymes could aid in the development of novel tools and strategies to control mosquitoes in a future warmer climate. This study evaluated the effects of temperature on the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to pyrethroids and their expression of metabolic enzymes.METHODS: Anopheles gambiae s.l. eggs obtained from laboratory-established colonies were reared under eight temperature regimes (25, 28, 30, 32, 34, 36, 38, and 40 °C). Upon adult emergence, 3- to 5-day-old female non-blood-fed mosquitoes were used for susceptibility tests following the World Health Organization (WHO) bioassay protocol. Batches of 20-25 mosquitoes from each temperature regime (25-34 °C) were exposed to two pyrethroid insecticides (0.75% permethrin and 0.05% deltamethrin). In addition, the levels of four metabolic enzymes (α-esterase, β-esterase, glutathione S-transferase [GST], and mixed-function oxidase [MFO]) were examined in mosquitoes that were not exposed and those that were exposed to pyrethroids.
RESULTS: Mortality in An. gambiae s.l. mosquitoes exposed to deltamethrin and permethrin decreased at temperatures above 28 °C. In addition, mosquitoes reared at higher temperatures were more resistant and had more elevated enzyme levels than those raised at low temperatures. Overall, mosquitoes that survived after being exposed to pyrethroids had higher levels of metabolic enzymes than those that were not exposed to pyrethroids.
CONCLUSIONS: This study provides evidence that elevated temperatures decreased An. gambiae s.l. mosquitoes' susceptibility to pyrethroids and increased the expression of metabolic enzymes. This evidence suggests that elevated temperatures projected in a future warmer climate could increase mosquitoes' resistance to insecticides and complicate malaria vector control measures. This study therefore provides vital information, and suggests useful areas of future research, on the effects of temperature variability on mosquitoes that could guide vector control measures in a future warmer climate.

Keywords:  Anopheles gambiae; Bioassay; Biochemical analysis; Climate change; Insecticide; Metabolic enzyme; Susceptibility

DOI:  https://doi.org/10.1186/s13071-022-05273-z
Infect Genet Evol. 2022 May 05. pii: S1567-1348(22)00093-4. [Epub ahead of print] 105296

Yearly variations of the genetic structure of Aedes aegypti (Linnaeus) (Diptera: Culicidae) in the Philippines (2017-2019).

Frances Edillo, Rhoniel Ryan Ymbong, Maureen Mathilde Cabahug, Dinesse Labiros, Mark Windy Suycano, Louis Lambrechts, Anavaj Sakuntabhai.

  Dengue is the fastest emerging arboviral disease in the world, imposing a substantial health and economic burden in the tropics and subtropics. The mosquito, Aedes aegypti, is the primary vector of dengue in the Philippines. We examined the genetic structure of Ae. aegypti populations collected from the Philippine major islands (Luzon, Visayas and Mindanao), each with highland (Baguio city, Cebu city mountains and Maramag, Bukidnon, respectively) and lowland sites (Quezon city; Liloan, Cebu and Cagayan de Oro [CDO] city, respectively) during the wet (2017-2018 and 2018-2019) and dry seasons (2018 and 2019). Mosquitoes (n = 1800) were reared from field-collected eggs and immatures, and were analyzed using 12 microsatellite loci. Generalized linear model analyses revealed yearly variations between highlands and lowlands in the major islands as supported by Bayesian clustering analyses on: 1) stronger selection (inbreeding coefficient, FIS = 0.52) in 2017-2018 than in 2018-2019 (FIS = 0.32) as influenced by rainfall, 2) the number of non-neutral loci indicating selection, and 3) differences of effective population size although at p = 0.05. Across sites except Baguio and CDO cities: 1) FIS varied seasonally as influenced by relative humidity (RH), and 2) the number of non-neutral loci varied as influenced by RH and rainfall indicating selection. Human-mediated activities and not isolation by distance influenced genetic differentiations of mosquito populations within (FST = 0.04) the major islands and across sites (global FST = 0.16). Gene flow (Nm) and potential first generation migrants among populations were observed between lowlands and highlands within and across major islands. Our results suggest that dengue control strategies in the epidemic wet season are to be changed into whole year-round approach, and water pipelines are to be installed in rural mountains to prevent the potential breeding sites of mosquitoes.

Keywords:  Aedes aegypti; Dengue; Philippines; Population structure; Weather

DOI:  https://doi.org/10.1016/j.meegid.2022.105296
Front Public Health. 2022 ;10 818204

Outbreak Investigation: Jamestown Canyon Virus Surveillance in Field-Collected Mosquitoes (Diptera: Culicidae) From Wisconsin, USA, 2018-2019.

Melissa R Farquhar, Nicholas B Thrun, Bradley J Tucker, Lyric C Bartholomay.

  During the summers of 2017-2019, 60 human cases of Jamestown Canyon virus-associated disease were reported in the State of Wisconsin, U.S.A; by comparison, there were 28 cases in the 5 years prior. Jamestown Canyon virus (JCV, Peribunyaviridae: Orthobunyavirus) is a zoonotic, mosquito-borne virus that is endemic throughout North America. The proposed transmission cycle for JCV involves horizontal transmission by a variety of mammal-feeding mosquito species and deer hosts, and transseasonal maintenance by vertical transmission in Aedes mosquito species. Although some of the earliest work on JCV transmission and disease was done in Wisconsin (WI), little is known about the spectrum of mosquitoes that are currently involved in transmission and maintenance of JCV, which is key to inform the approach to control and prevent JCV transmission, and to understand why case numbers have increased dramatically in recent years. Therefore, we undertook an intensive surveillance effort in Sawyer and Washburn counties, WI between April and August of 2018 and 2019, in an area with a concentration of JCV human cases. Larval and adult stages of mosquitoes were surveyed using larval dippers and emergence traps, light traps, resting boxes, a Shannon-style trap, and backpack aspirator. In total, 14,949 mosquitoes were collected in 2018, and 28,056 in 2019; these specimens represent 26 species in 7 genera. Suspect vector species were tested for JCV by polymerase chain reaction (PCR); of 23 species that were tested, only Aedes provocans yielded JCV positive results. In 2018, a single pool of Ae. provocans tested positive. In 2019, with more focused early season surveillance, we detected JCV in 4 pools of adult mosquitoes, and one pool that consisted of lab-raised adults that were collected as larvae. Material from all of these PCR-positive samples also yielded infectious virus in cell culture. Overall, these data provide new insight into the seasonality and habitat preferences for 26 mosquito species in Northern WI, which will be useful to inform future surveillance efforts for JCV. The results underscore the importance of Ae. provocans as a vector species involved in transseasonal maintenance of JCV in this region.

Keywords:  Aedes provocans; Midwest USA; arbovirus; spring Aedes; vertical transmission

DOI:  https://doi.org/10.3389/fpubh.2022.818204
J Med Entomol. 2022 May 10. pii: tjac048. [Epub ahead of print]

Natural Aedes-Borne Virus Infection Detected in Male Adult Aedes aegypti (Diptera: Culicidae) Collected From Urban Settings in Mérida, Yucatán, México.

Oscar D Kirstein, Guadalupe Ayora Talavera, Zhuoran Wei, Karina J Ciau-Carrilo, Edgar Koyoc-Cardeña, Henry Puerta-Guardo, Ester Rodríguez-Martín, Anuar Medina-Barreiro, Azael Che Mendoza, Anne L Piantadosi, Pablo Manrique-Saide, Gonzalo M Vazquez-Prokopec.

  Aedes-borne viruses (ABVs) such as dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) contribute significantly to the global burden of infectious diseases, disproportionately affecting disadvantaged populations from tropical and subtropical urban areas. ABVs can be transmitted from female mosquitoes to their progeny by vertical transmission via transovarial and/or trans-egg vertical transmission and contribute to the maintenance of infected-mosquito populations year-round in endemic regions. This study describes the natural infection rate of DENV, CHIKV, and ZIKV in field-caught male Aedes (Sergentomyia) aegypti (Linnaeus) mosquitoes from Mérida, Yucatán, México, as a proxy for the occurrence of vertical virus transmission. We used indoor sequential sampling with Prokopack aspirators to collect all mosquitoes inside houses from ABV hotspots areas. Collections were performed in a DENV and CHIKV post-epidemic phase and during a period of active ZIKV transmission. We individually RT-qPCR tested all indoor collected Ae. aegypti males (1,278) followed by Sanger sequencing analysis for final confirmation. A total of 6.7% male mosquitoes were positive for ABV (CHIKV = 5.7%; DENV = 0.9%; ZIKV = 0.1%) and came from 21.0% (30/143) houses infested with males. Most ABV-positive male mosquitoes were positive for CHIKV (84.8%). The distribution of ABV-positive Ae. aegypti males was aggregated in a few households, with two houses having 11 ABV-positive males each. We found a positive association between ABV-positive males and females per house. These findings suggested the occurrence of vertical arbovirus transmission within the mosquito populations in an ABV-endemic area and, a mechanism contributing to viral maintenance and virus re-emergence among humans in post-epidemic periods.

Keywords:   Aedes ; density; infection; male; transmission

DOI:  https://doi.org/10.1093/jme/tjac048
PLoS Negl Trop Dis. 2022 May 09. 16(5): e0010375

Evaluation of the effectiveness of the california mosquito-borne virus surveillance & response plan, 2009-2018.

Mary E Danforth, Robert E Snyder, Emma T N Lonstrup, Christopher M Barker, Vicki L Kramer.

Local vector control and public health agencies in California use the California Mosquito-Borne Virus Surveillance and Response Plan to monitor and evaluate West Nile virus (WNV) activity and guide responses to reduce the burden of WNV disease. All available data from environmental surveillance, such as the abundance and WNV infection rates in Culex tarsalis and the Culex pipiens complex mosquitoes, the numbers of dead birds, seroconversions in sentinel chickens, and ambient air temperatures, are fed into a formula to estimate the risk level and associated risk of human infections. In many other areas of the US, the vector index, based only on vector mosquito abundance and infection rates, is used by vector control programs to estimate the risk of human WNV transmission. We built models to determine the association between risk level and the number of reported symptomatic human disease cases with onset in the following three weeks to identify the essential components of the risk level and to compare California's risk estimates to vector index. Risk level calculations based on Cx. tarsalis and Cx. pipiens complex levels were significantly associated with increased human risk, particularly when accounting for vector control area and population, and were better predictors than using vector index. Including all potential environmental components created an effective tool to estimate the risk of WNV transmission to humans in California.

DOI: https://doi.org/10.1371/journal.pntd.0010375
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2022 Apr 11. 34(2): 117-119

[Sustainable and precise Anopheles control to maintain malaria elimination in China].

Q Y Liu.

  Malaria caused a heavy disease, economic and social burdens in China. Following 70-year concerted efforts, China has been awarded a malaria-free certification by the WHO on June 2021. This paper summarizes the control strategies of Anopheles vectors from malaria control to post-elimination stages in China, emphasizes the risk of imported malaria cases caused re-transmission and the challenges of Anopheles control after malaria elimination in China. Sustainable and precise vector control is still required in China during the post-elimination stage to consolidate malaria elimination achievements in the country. In addition, China's innovative vector control strategies, technologies and experiences will contribute to global malaria control and elimination programs.

Keywords:   Anopheles ; Elimination; Malaria; Vector control

DOI:  https://doi.org/10.16250/j.32.1374.2022069
Infect Dis Poverty. 2022 May 13. 11(1): 54

Vector control in China, from malaria endemic to elimination and challenges ahead.

Xinyu Feng, Jun Feng, Li Zhang, Hong Tu, Zhigui Xia.

  BACKGROUND: Vector control is an important approach to preventing and controlling malaria. From the malaria epidemic to malaria elimination in China, vector control has played an essential and irreplaceable role in the historical process. This review systematically summarizes the evolution, adjustment, and optimization of vector control strategy towards elimination and discusses the challenges ahead.MAIN TEXT: This review first summarizes the evolution of vector control strategies during different stages of malaria epidemic, control, elimination, and post-elimination in China. We then distill the vector control experience and lessons in different stages. We discuss the current and future challenges and propose future research directions and developments for novel malaria vector control strategies.
RESULTS: Vector control has played an invaluable role in achieving malaria elimination. China adopted different prevention and control measures in response to the different malaria-endemic situations and vector distributions. Firstly, baseline surveys were initiated to establish the entomological data and helped clarify the prevention priorities and targets. Secondly, targeted and adjusted vector control strategies were conducted in various regions according to the local epidemic characteristics and different vector species. Thirdly, scientific research facilitated efficient vector-control strategies. In addition, the overall economic and social development have promoted environmental improvement, personal protection, and health care. Prediction of the vector distribution was integrated into risk assessment strategies, allowing for sustaining achievements in risk areas.
CONCLUSIONS: The tailored and adapted vector control strategies have played a critical role in China's malaria prevention, control, and elimination. Achievements and lessons learned on vector control from this progress would provide a practical reference in coping with the challenges and potential barriers other countries face in the global effort to eliminate malaria.

Keywords:  Anopheles; China; Elimination; Endemic; Malaria; Mosquito; Vector control

DOI:  https://doi.org/10.1186/s40249-022-00971-3
BMC Public Health. 2022 May 10. 22(1): 930

The combined impact of LLINs, house screening, and pull-push technology for improved malaria control and livelihoods in rural Ethiopia: study protocol for household randomised controlled trial.

Abebe Asale, Menale Kassie, Zewdu Abro, Bayu Enchalew, Aklilu Belay, Peter O Sangoro, David P Tchouassi, Clifford M Mutero.

  BACKGROUND: The combined application of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are commonly used malaria interventions that target indoor Anopheles vectors. Recent studies on the effects of house screening (HS) and LLINs have demonstrated a reduction in indoor vector densities and malaria when the interventions are combined. In addition, complementary interventions are needed to curb co-occurring pest populations which pose menace to agricultural crop productivity and food security. However, interventions that impact malaria mainly centre on public health strategies, overlooking subtle but important component of agricultural measures. Addressing the coexisting risks of malaria and crop pests could contribute to improved livelihood of communities.METHODS: A four-armed household, cluster-randomized, controlled study will be conducted to assess the combined impact of HS, LLINs and push-pull agricultural technology (PPT) against clinical malaria in children in Ethiopia. The unit of randomization will be the household, which includes a house and its occupants. A total of 838 households will be enrolled in this study. In this trial 246 households will receive LLINs and HS, 250 will receive LLINs, HS and PPT, 175 households will receive LLINs and PPT. The remaining 167 houses which receive LLINs only will be used as control. One child aged ≤14 years will be enrolled per household in each treatment and followed for clinical malaria using active case detection to estimate malaria incidence for two malaria transmission seasons.
DISCUSSION: Episodes of clinical malaria, density of indoor biting malaria vectors, sporozoite infection rate, improved crop infestation rate, crop yield gain, livestock productivity and cost effectiveness analysis will be the end points of this study. Socio-economic, social demographic, cost-effectiveness analysis will be conducted using qualitative and participatory methods to explore the acceptability of HS and PPT. Documenting the combined impact of LLINs, HS and PPT on the prevalence of clinical malaria and crop pest damage will be the first of its kind.
TRIAL REGISTRATION: Pan African Clinical Trials Registry, PACTR202006878245287. 24/06/2020. https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=11101 .

Keywords:  Ethiopia; House screening; Jabi Tehnan; Long-lasting insecticidal nets; Malaria; Push pull technology; Randomized control trial; Study protocol; Vector control

DOI:  https://doi.org/10.1186/s12889-022-12919-1
Environ Entomol. 2022 May 11. pii: nvac023. [Epub ahead of print]

Snow-Covered Tires Generate Microhabitats That Enhance Overwintering Survival of Aedes albopictus (Diptera: Culicidae) in the Midwest, USA.

Katie M Susong, Bradley J Tucker, Gebienna M Bron, Patrick Irwin, John Mitchell Kirsch, Daniel Vimont, Chris Stone, Susan M Paskewitz, Lyric C Bartholomay.

  The Asian tiger mosquito, Aedes albopictus (Skuse), is a public health threat because it can potentially transmit multiple pathogenic arboviruses, exhibits aggressive diurnal biting, and is highly invasive. As Ae. albopictus moved northward into the United States, the limits of expansion were predicted as locations with a mean January temperature warmer than -2.5°C. We postulated that the range of Ae. albopictus could exceed these temperature limits if eggs in diapause overwinter in tires that provide an insulating effect from extreme temperatures. Fifteen tires with Ae. albopictus and Aedes triseriatus (Say) eggs, a native cold hardy species, were placed outside at five locations along a latitudinal gradient in Wisconsin and Illinois during the winter of 2018-2019; notably, in January 2019, a regional arctic air event brought the lowest temperatures recorded in over 20 yr. External and internal tire temperatures were recorded at 3 hr intervals, and egg survival was recorded after six months. Aedes albopictus eggs survived only from tires at northernmost locations. The mean internal January temperature of tires that supported survival was -1.8°C, while externally the mean temperature was -5.3°C, indicating that tires provided an average of +3.5°C of insulation. Tires that supported egg survival also had over 100 mm of snow cover during January. In the absence of snow cover, tires across the study area provided an average +0.79°C [95% CI 0.34-1.11] insulation. This work provides strong argument for the inclusion of microhabitats in models of dispersal and establishment of Ae. albopictus and other vector species.

Keywords:   Ae. albopictus ; Midwest USA; microhabitat; overwintering; tires

DOI:  https://doi.org/10.1093/ee/nvac023
Geospat Health. 2022 May 11. 17(1):

Spatial dispersal of <em>Aedes albopictus</em> mosquitoes captured by the modified sticky ovitrap in Selangor, Malaysia.

Muhammad Aidil Roslan, Romano Ngui, Muhammad Fathi Marzuki, Indra Vythilingam, Aziz Shafie, Sabri Musa, Wan Yusoff Wan Sulaiman.

Dengue is a major mosquito-borne disease in many tropical and sub-tropical countries worldwide, with entomological surveillance and control activities as the key management approaches. This study aimed to explore the spatial dispersal of the vector Aedes albopictus, captured by the modified sticky ovitrap (MSO) in residential areas with low-rise buildings in Selangor, Malaysia. Distribution maps were created and shown as temporally distinguished classes based on hotspot analysis by Getis-Ord; spatial autocorrelation assessed by semivariograms using the exponential Kernel function; and universal Kriging showing areas with estimated high and low vector densities. Distribution, hotspot and interpolated maps were analysed based on the total number of mosquitoes by month and week. All maps in the present study were generated and visualised in ArcMap. Spatial autocorrelation of Ae. albopictus based on the monthly occurrence of Ae. albopictus was found in March, April, October, November and December 2018, and when based on the weekly numbers, in weeks 1, 2, 3, 5, 7, 12, 14, 25, 26, 27, 31, 33, 42, 49 and 52. Semivariograms, based on the monthly and weekly numbers of Ae. albopictus, indicated spatial autocorrelation of the species extending between 50 and 70 m. The mosquito density maps reported in this study may provide beneficial information to facilitate implementation of more efficient entomological control activities.

DOI: https://doi.org/10.4081/gh.2022.1025
Parasitol Res. 2022 May 14.

Blood feeding habits of mosquitoes: hardly a bite in South America.

Karelly Melgarejo-Colmenares, María Victoria Cardo, Darío Vezzani.

  Mosquito blood feeding plays a key role in epidemiology. Despite its importance and large number of studies worldwide, less attention has been paid in South America. We summarized some general concepts and methodological issues related to the study of mosquito blood feeding habits, and compiled and analyzed all published information regarding the subject in the continent until 2020. Available literature comprised 152 scientific studies, that pursued different approaches: human landing catches (102 studies), baited trap (19), and blood meal analyses of collected specimens (38). Among the latter, 23 used serological and 15 molecular techniques. Species most frequently studied were those incriminated in malaria transmission, whereas relevant vectors such as Aedes aegypti, Ae. albopictus, and Haemagogus janthinomys were surprisingly neglected. Brazil was the leading country both in number of works and species studied. For over 70% of the species and three out of 13 South American countries there is no single information on mosquito blood feeding habits. Data from baited traps included 143 mosquito species, 83.9% of which were attracted to humans, either exclusively (10.5%) or in combination with other vertebrates (73.4%). Host blood identification of field collected specimens provided data on 102 mosquito species, and 60.8% of these fed on humans (55.9% combined with other vertebrates). Only 17 of the 73 species assessed by both methods yielded similar feeding patterns. Finally, supplementary tables are provided in a comprehensive summary of all information available and information gaps are highlighted for future research in the continent.

Keywords:  Baited traps; Blood meal analysis; Host feeding patterns; Host preference; Human landing; Mosquito-borne diseases

DOI:  https://doi.org/10.1007/s00436-022-07537-0
Elife. 2022 May 12. pii: e76663. [Epub ahead of print]11

A persistent behavioral state enables sustained predation of humans by mosquitoes.

Trevor R Sorrells, Anjali Pandey, Adriana Rosas-Villegas, Leslie B Vosshall.

  Predatory animals pursue prey in a noisy sensory landscape, deciding when to continue or abandon their chase. The mosquito Aedes aegypti is a micropredator that first detects humans at a distance through sensory cues such as carbon dioxide. As a mosquito nears its target it senses more proximal cues such as body heat that guide it to a meal of blood. How long the search for blood continues after initial detection of a human is not known. Here we show that a 5-second optogenetic pulse of fictive carbon dioxide induced a persistent behavioral state in female mosquitoes that lasted for more than 10 minutes. This state is highly specific to females searching for a blood meal and was not induced in recently blood-fed females or in males, who do not feed on blood. In males that lack the gene fruitless, which controls persistent social behaviors in other insects, fictive carbon dioxide induced a long-lasting behavior response resembling the predatory state of females. Finally, we show that the persistent state triggered by detection of fictive carbon dioxide enabled females to engorge on a blood meal mimic offered up to 14 minutes after the initial 5-second stimulus. Our results demonstrate that a persistent internal state allows female mosquitoes to integrate multiple human sensory cues over long timescales, an ability that is key to their success as an apex micropredator of humans.

Keywords:  genetics; genomics; neuroscience

DOI:  https://doi.org/10.7554/eLife.76663
Mol Ecol. 2022 May 11.

Multi-omics analysis identifies a CYP9K1 haplotype conferring pyrethroid resistance in the malaria vector Anopheles funestus in East Africa.

Jack Hearn, Carlos S Djoko Tagne, Sulaiman S Ibrahim, Billy Tene-Fossog, Leon M J Mugenzi, Helen Irving, Jacob M Riveron, Gareth D Weedall, Charles S Wondji.

Metabolic resistance to pyrethroids is a menace to the continued effectiveness of malaria vector controls. Its molecular basis is complex and varies geographically across Africa. Here, we used a multi-omics approach, followed-up with functional validation to show that a directionally selected haplotype of a cytochrome P450, CYP9K1 is a major driver of resistance in Anopheles funestus. A PoolSeq GWAS using mosquitoes alive and dead after permethrin exposure, from Malawi and Cameroon, detected candidate genomic regions, but lacked consistency across replicates. Targeted sequencing of candidate resistance genes detected several SNPs associated with known pyrethroid resistance QTLs. The most significant SNPs were in the cytochrome P450 CYP304B1 (Cameroon), CYP315A1 (Uganda) and the ABC transporter gene ABCG4 (Malawi). However, when comparing field resistant mosquitoes to laboratory susceptible, the pyrethroid resistance locus rp1 and SNPs around the ABC transporter ABCG4 were consistently significant, except for Uganda where SNPs in the P450 CYP9K1 was markedly significant. In vitro heterologous metabolism assays with recombinant CYP9K1 revealed that it metabolises type II pyrethroid (deltamethrin; 64% depletion) but not type I (permethrin; 0%), while moderately metabolising DDT (17%). CYP9K1 exhibited reduced genetic diversity in Uganda underlying an extensive selective sweep. Furthermore, a glycine to alanine (G454A) amino acid change in CYP9K1 was fixed in Ugandan mosquitoes but not in other An. funestus populations. This study sheds further light on the evolution of metabolic resistance in a major malaria vector by implicating more genes and variants that can be used to design field-applicable markers to better track resistance Africa-wide.

DOI: https://doi.org/10.1111/mec.16497
BMC Public Health. 2022 May 10. 22(1): 932

Model to support intervention prioritization for the control of Aedes aegypti in Brazil: a multi-criteria approach.

Lucas A Dos Santos, Ana Flávia A Dos Santos, Amanda G de Assis, João F da Costa Júnior, Ricardo P de Souza.

  BACKGROUND: Despite continuous strategic investments to mitigate the complexity involving arboviruses control, it is still necessary to further research methods and techniques to achieve in depth knowledge and shorter response times in the application of intervention activities. Consequently, the current work focused its efforts on the development of a multicriteria decision support model for the prioritization of prompt response activities for Aedes aegypti control, based on a case study in the city of Natal/RN.METHOD: The research was carried out in three stages: a) preliminary; b) modelling and choice; and c) finalization; the second stage was made possible by the Flexible and Interactive Tradeoff (FITradeoff) method for ranking problematic. Furthermore, the research encompassed ten actors who were involved in the model construction, eight internal and two external to the Natal Zoonoses Control Center (ZCC-Natal) as well as the observation of four operating scenarios for arboviruses control, based on transmission levels; and, evaluation of eleven alternatives from six different criteria perspectives.
RESULTS: Rankings of the interventions evaluated in each of the four control operation scenarios present in the city of Natal/RN were obtained, considering technical criteria guided by the Pan American Health Organization (PAHO).
CONCLUSIONS: As a result, it was developed a structured decision-making model that could help decision makers to minimize the effects and risks associated with the proliferation of the vector.

Keywords:  Arbovirus control; Epidemiological surveillance; MCDA; Multicriteria decision analysis

DOI:  https://doi.org/10.1186/s12889-022-13006-1
Parasitol Int. 2022 May 06. pii: S1383-5769(22)00061-7. [Epub ahead of print]89 102597

Estimation of Plasmodium falciparum transmission using multiepitope chimeric antigen in the postelimination phase in Yunnan, China.

Meixue Yao, Lishun Xiao, Xiaodong Sun, Xiao Hao, Zurui Lin, Qiongqiong Bai, Dehui Yin.

  BACKGROUND: The continuous monitoring of malaria transmission intensity is still required to maintain elimination status after reaching the malaria elimination stage. In this study, serological surveillance with multiepitope artificial antigen was used to assess the transmission of Plasmodium falciparum in Yunnan, China, where malaria elimination has just been achieved, to provide data to support malaria control in the postelimination period.METHODS: Samples were collected in three border counties and one inland county in Yunnan Province in 2016 using a stratified whole-group sampling method. Fingerstick blood was collected from all participants, and antibodies to Malaria Random Constructed Antigen-1 (M. RCAg-1) were detected by indirect ELISA. The transmission intensity of P. falciparum malaria was estimated using a catalytic conversion model based on the maximum likelihood of generating a community seroconversion rate (SCR).
RESULTS: A total of 5566 samples were collected. There was no statistically significant difference in antibody level between the inland county and the nonendemic area, but the antibody level in border counties was significantly higher than those in the inland county and the nonendemic control area. No seropositive cases were found in Yanjin County, and the seropositivity rate increased with age in the three border counties. The highest intensity of P. falciparum malaria transmission was in Zhenkang County (SCR = 0.0030, CI: 0.0029, 0.0031), followed by Gengma County (SCR = 0.0013, CI: 0.0012, 0.0015) and Yingjiang County (SCR = 0.00088, CI: 0.00083, 0.00090).
CONCLUSION: The transmission intensity of P. falciparum malaria in Yunnan Province has obviously decreased in recent years, but for the border areas where malaria has just been eliminated, the transmission intensity will not immediately drop to zero, and it still needs to be monitored for a period of time to maintain malaria elimination status.

Keywords:  China; Elimination; Multiepitope chimeric antigens; Plasmodium falciparum; Serology; Surveillance

DOI:  https://doi.org/10.1016/j.parint.2022.102597
Pediatrics. 2022 May 11. pii: e2021055522. [Epub ahead of print]

Dengue: A Growing Problem With New Interventions.

Joshua M Wong, Laura E Adams, Anna P Durbin, Jorge L Muñoz-Jordán, Katherine A Poehling, Liliana M Sánchez-González, Hannah R Volkman, Gabriela Paz-Bailey.

Dengue is the disease caused by 1 of 3 distinct, but closely related dengue viruses (DENV-1-4) that are transmitted by Aedes spp. mosquito vectors. It is the most common arboviral disease worldwide, with the greatest burden in tropical and sub-tropical regions. In the absence of effective prevention and control measures, dengue is projected to increase in both disease burden and geographic range. Given its increasing importance as an etiology of fever in the returning traveler or the possibility of local transmission in regions in the United States with competent vectors, as well as the risk for large outbreaks in endemic US territories and associated states, clinicians should understand its clinical presentation and be familiar with appropriate testing, triage, and management of patients with dengue. Control and prevention efforts reached a milestone in June 2021 when the Advisory Committee on Immunization Practices (ACIP) recommended Dengvaxia for routine use in children aged 9 to 16 years living in endemic areas with laboratory confirmation of previous dengue virus infection. Dengvaxia is the first vaccine against dengue to be recommended for use in the United States and one of the first to require laboratory testing of potential recipients to be eligible for vaccination. In this review, we outline dengue pathogenesis, epidemiology, and key clinical features for front-line clinicians evaluating patients presenting with dengue. We also provide a summary of Dengvaxia efficacy, safety, and considerations for use as well as an overview of other potential new tools to control and prevent the growing threat of dengue .

DOI: https://doi.org/10.1542/peds.2021-055522
Infect Dis Poverty. 2022 May 10. 11(1): 51

Malaria from hyperendemicity to elimination along international borders in Yunnan, China during 2003‒2020: a case study.

Hui Liu, Yaowu Zhou, Yan Deng, Zurui Lin, Canglin Zhang, Qiyan Chen, Chun Wei, Kaixia Duan, Peng Tian, Hongning Zhou, Jianwei Xu.

  BACKGROUND: Border malaria is one of the most intractable problems hindering malaria elimination worldwide. Movement of both the human population and anopheline mosquitoes infected with Plasmodium spp. can cause cross-border malaria transmission. The Yunnan border area was still hyperendemic for malaria in the early part of this century. The objective of this case study was to analyze the strategies, interventions and impacts of malaria control and elimination in the Yunnan border area.MAIN TEXT: A total of 10,349 malaria cases and 17.1 per 10,000 person-years of annual parasite incidence (API) were reported in the border area in 2003. Based on natural village-based stratification, integrated interventions, including mass drug administration for radical cures and preventive treatment, clinically presumptive treatment of all febrile patients for malaria and indoor residual spraying or dipping bed nets with insecticides were successfully carried out from 2003 to 2013. The overall API was reduced to 0.6 per 10,000 person-years by 2013, while effective cross-border collaboration interventions dramatically reduced the malaria burden in the neighbouring border areas of Myanmar. From 2014 forward, the comprehensive strategy, including universal coverage of surveillance to detect malaria cases, a rapid response to possible malaria cases and effective border collaboration with neighbouring areas, successfully eliminated malaria and prevented reintroduction of malaria transmission in the Yunnan border area.
CONCLUSIONS: In Yunnan malaria burden has successfully reduced by dynamically accurate stratification and comprehensive interventions; and then the region achieved elimination and prevented reintroduction of malaria transmission through intensive surveillance, rapid response and border collaboration. Other border areas should perform their own intervention trials to develop their own effective strategy.

Keywords:  Border area; China; Control; Elimination; International collaboration; Malaria; Yunnan

DOI:  https://doi.org/10.1186/s40249-022-00972-2
PLoS Negl Trop Dis. 2022 May 09. 16(5): e0010415

Malaria transmission structure in the Peruvian Amazon through antibody signatures to Plasmodium vivax.

Jason Rosado, Gabriel Carrasco-Escobar, Oscar Nolasco, Katherine Garro, Hugo Rodriguez-Ferruci, Mitchel Guzman-Guzman, Alejandro Llanos-Cuentas, Joseph M Vinetz, Narimane Nekkab, Michael T White, Ivo Mueller, Dionicia Gamboa.

BACKGROUND: The landscape of malaria transmission in the Peruvian Amazon is temporally and spatially heterogeneous, presenting different micro-geographies with particular epidemiologies. Most cases are asymptomatic and escape routine malaria surveillance based on light microscopy (LM). Following the implementation of control programs in this region, new approaches to stratify transmission and direct efforts at an individual and community level are needed. Antibody responses to serological exposure markers (SEM) to Plasmodium vivax have proven diagnostic performance to identify people exposed in the previous 9 months.METHODOLOGY: We measured antibody responses against 8 SEM to identify recently exposed people and determine the transmission dynamics of P. vivax in peri-urban (Iquitos) and riverine (Mazán) communities of Loreto, communities that have seen significant recent reductions in malaria transmission. Socio-demographic, geo-reference, LM and qPCR diagnosis data were collected from two cross-sectional surveys. Spatial and multilevel analyses were implemented to describe the distribution of seropositive cases and the risk factors associated with exposure to P. vivax.
PRINCIPAL FINDINGS: Low local transmission was detected by qPCR in both Iquitos (5.3%) and Mazán (2.7%); however, seroprevalence indicated a higher level of (past) exposure to P. vivax in Mazán (56.5%) than Iquitos (38.2%). Age and being male were factors associated with high odds of being seropositive in both sites. Higher antibody levels were found in individuals >15 years old. The persistence of long-lived antibodies in these individuals could overestimate the detection of recent exposure. Antibody levels in younger populations (<15 years old) could be a better indicator of recent exposure to P. vivax.
CONCLUSIONS: The large number of current and past infections detected by SEMs allows for detailed local epidemiological analyses, in contrast to data from qPCR prevalence surveys which did not produce statistically significant associations. Serological surveillance will be increasingly important in the Peruvian Amazon as malaria transmission is reduced by continued control and elimination efforts.

DOI: https://doi.org/10.1371/journal.pntd.0010415
BMC Infect Dis. 2022 May 13. 22(1): 460

Understanding the epidemiology, clinical characteristics, knowledge and barriers to treatment and prevention of malaria among returning international laborers in northern Vietnam: a mixed-methods study.

Kimberly A Edgel, Sara Canavati, Hoi Thi Le, Tho Huy Tran, Kinh Van Nguyen, Trung Vu Nguyen, Nga Thi Nguyen, Hoa Mai Tran, Thang Duc Ngo, Duong Thanh Tran, Binh Thi Huong Nguyen, Long Khanh Tran, Thu Minh Nguyen, Rosalie J Whedbee, Ekaterina I Milgotina, Nicholas J Martin.

  BACKGROUND: With the decline in local malaria transmission in Vietnam as a result of the National Malaria Control Program (NMCP) elimination activities, a greater focus on the importation and potential reintroduction of transmission are essential to support malaria elimination objectives.METHODS: We conducted a multi-method assessment of the demographics, epidemiology, and clinical characteristics of imported malaria among international laborers returning from African or Southeast Asian countries to Vietnam. Firstly, we conducted a retrospective review of hospital records of patients from January 2014 to December 2016. Secondly, we conducted a mixed-methods prospective study for malaria patients admitted to the study sites from January 2017 to May 2018 using a structured survey with blood sample collection for PCR analysis and in-depth interviews. Data triangulation of the qualitative and quantitative data was used during analysis.
RESULTS: International laborers were young (median age 33.0 years IQR 28.0-39.5 years), predominantly male (92%) adults returning mostly from the African continent (84%) who stayed abroad for prolonged periods (median time 13.5 months; IQR 6.0-331.5 months) and were involved in occupations that exposed them to a higher risk of malaria infection. Epidemiological trends were also similar amongst study strands and included the importation of Plasmodium falciparum primarily from African countries and P. vivax from Southeast Asian countries. Of 11 P. malariae and P. ovale infections across two study strands, 10 were imported from the African continent. Participants in the qualitative arm demonstrated limited knowledge about malaria prior to travelling abroad, but reported knowledge transformation through personal or co-worker's experience while abroad. Interestingly, those who had a greater understanding of the severity of malaria presented to the hospital for treatment sooner than those who did not; median of 3 days (IQR 2.0-7.0 days) versus 5 days (IQR 4.0-9.5 days) respectively.
CONCLUSION: To address the challenges to malaria elimination raised by a growing Vietnamese international labor force, consideration should be given to appropriately targeted interventions and malaria prevention strategies that cover key stages of migration including pre-departure education and awareness, in-country prevention and prophylaxis, and malaria screening upon return.

Keywords:  Key populations; Malaria elimination; Malaria importation; Migration; Plasmodium falciparum; Plasmodium malariae; Plasmodium ovale; Plasmodium vivax; Population movement; Vietnam

DOI:  https://doi.org/10.1186/s12879-022-07322-5
Int J Environ Res Public Health. 2022 May 03. pii: 5541. [Epub ahead of print]19(9):

Assessment of the Costs Related to West Nile Virus Monitoring in Lombardy Region (Italy) between 2014 and 2018.

Francesco Defilippo, Michele Dottori, Davide Lelli, Mario Chiari, Danilo Cereda, Marco Farioli, Rosa Chianese, Monica Pierangela Cerioli, Francesca Faccin, Sabrina Canziani, Tiziana Trogu, Enrica Sozzi, Ana Moreno, Antonio Lavazza, Umberto Restelli.

  In Italy, the West Nile Virus surveillance plan considers a multidisciplinary approach to identify the presence of the virus in the environment (entomological, ornithological, and equine surveillance) and to determine the risk of infections through potentially infected donors (blood and organ donors). The costs associated with the surveillance program for the Lombardy Region between 2014 and 2018 were estimated. The costs of the program were compared with a scenario in which the program was not implemented, requiring individual blood donation nucleic acid amplification tests (NAT) to detect the presence of WNV in human samples throughout the seasonal period of vector presence. Considering the five-year period, the application of the environmental/veterinary surveillance program allowed a reduction in costs incurred in the Lombardy Region of 7.7 million EUR. An integrated surveillance system, including birds, mosquito vectors, and dead-end hosts such as horses and humans, can prevent viral transmission to the human population, as well as anticipate the detection of WNV using NAT in blood and organ donors. The surveillance program within a One Health context has given the possibility to both document the expansion of the endemic area of WNV in northern Italy and avoid most of the NAT-related costs.

Keywords:  NAT; blood donors; horses; human; mosquitoes; surveillance

DOI:  https://doi.org/10.3390/ijerph19095541
Malar J. 2022 May 08. 21(1): 145

Receptivity to malaria: meaning and measurement.

Joshua O Yukich, Kim Lindblade, Jan Kolaczinski.

  "Receptivity" to malaria is a construct developed during the Global Malaria Eradication Programme (GMEP) era. It has been defined in varied ways and no consistent, quantitative definition has emerged over the intervening decades. Despite the lack of consistency in defining this construct, the idea that some areas are more likely to sustain malaria transmission than others has remained important in decision-making in malaria control, planning for malaria elimination and guiding activities during the prevention of re-establishment (POR) period. This manuscript examines current advances in methods of measurement. In the context of a decades long decline in global malaria transmission and an increasing number of countries seeking to eliminate malaria, understanding and measuring malaria receptivity has acquired new relevance.

Keywords:  Elimination; Malaria transmission measurement; Receptivity; Transmission networks

DOI:  https://doi.org/10.1186/s12936-022-04155-0
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2022 Apr 21. 34(2): 109-111

[Harder maintained than achieved: Challenges of maintaining malaria-free in China].

G D Zhu, Q Gao, J Cao.

  On June 2021, China was certified malaria-free by WHO. However, the global number and death of malaria cases have recently increased, and the malaria vectors will continue to inhabit in China, resulting in a high difficulty in consolidation of malaria elimination achievements. Hereby, we analyze the current challenges and propose the future priority of the national malaria control program in China, in order to provide insights into prevention of re-establishment of imported malaria in the country.

Keywords:  Challenge; Consolidation; Elimination; Malaria

DOI:  https://doi.org/10.16250/j.32.1374.2022087