bims-mosdis 2023-03-19 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2023–03–19
fiveteen papers selected by
Richard Halfpenny, Staffordshire University

Anopheles rufipes implicated in malaria transmission both indoors and outdoors alongside Anopheles funestus and Anopheles arabiensis in rural south-east Zambia.
Species composition and insecticide resistance in malaria vectors in Ellibou, southern Côte d'Ivoire and first finding of Anopheles arabiensis in Côte d'Ivoire.
The interplay between malaria vectors and human activity accounts for high residual malaria transmission in a Burkina Faso village with universal ITN coverage.
Trends of insecticide resistance monitoring in mainland Tanzania, 2004-2020.
Residual malaria transmission and the role of Anopheles arabiensis and Anopheles melas in central Senegal.
Fine-scale spatial distribution of deltamethrin resistance and population structure of Anopheles funestus and Anopheles arabiensis populations in Southern Mozambique.
Survey of mosquito species and mosquito-borne viruses in residential areas along the Sino-Vietnam border in Yunnan Province in China.
Evaluating the mosquito host range of Getah virus and the vector competence of selected medically important mosquitoes in Getah virus transmission.
First report of natural Wolbachia infections in mosquitoes from Cuba.
West Nile Virus diffusion in temperate regions and climate change. A systematic review.
Entomological survey of malaria vectors in Dashtestan County, South of Iran.
Sociodemographic and environmental factors associated with dengue, Zika, and chikungunya among adolescents from two Brazilian capitals.
Spatio-temporal analysis of environmental and climatic factors impacts on malaria morbidity in Ondo State, Nigeria.
A phylogenetic study of dengue virus in urban Vietnam shows long-term persistence of endemic strains.
Malaria Control by Mass Drug Administration With Artemisinin Plus Piperaquine on Grande Comore Island, Union of Comoros.

Malar J. 2023 Mar 16. 22(1): 95

Anopheles rufipes implicated in malaria transmission both indoors and outdoors alongside Anopheles funestus and Anopheles arabiensis in rural south-east Zambia.

Kochelani Saili, Christiaan de Jager, Onyango P Sangoro, Theresia E Nkya, Freddie Masaninga, Mwansa Mwenya, Andy Sinyolo, Busiku Hamainza, Emmanuel Chanda, Ulrike Fillinger, Clifford M Mutero.

   BACKGROUND: The primary malaria vector-control interventions, indoor residual spraying and long-lasting insecticidal nets, are effective against indoor biting and resting mosquito species. Consequently, outdoor biting and resting malaria vectors might elude the primary interventions and sustain malaria transmission. Varied vector biting and resting behaviour calls for robust entomological surveillance. This study investigated the bionomics of malaria vectors in rural south-east Zambia, focusing on species composition, their resting and host-seeking behaviour and sporozoite infection rates.
METHODS: The study was conducted in Nyimba District, Zambia. Randomly selected households served as sentinel houses for monthly collection of mosquitoes indoors using CDC-light traps (CDC-LTs) and pyrethrum spray catches (PSC), and outdoors using only CDC-LTs for 12 months. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were further identified using molecular techniques. Plasmodium falciparum sporozoite infection was determined using sandwich enzyme-linked immunosorbent assays.
RESULTS: From 304 indoor and 257 outdoor light trap-nights and 420 resting collection, 1409 female Anopheles species mosquitoes were collected and identified morphologically; An. funestus (n = 613; 43.5%), An. gambiae sensu lato (s.l.)(n = 293; 20.8%), Anopheles pretoriensis (n = 282; 20.0%), Anopheles maculipalpis (n = 130; 9.2%), Anopheles rufipes (n = 55; 3.9%), Anopheles coustani s.l. (n = 33; 2.3%), and Anopheles squamosus (n = 3, 0.2%). Anopheles funestus sensu stricto (s.s.) (n = 144; 91.1%) and Anopheles arabiensis (n = 77; 77.0%) were the dominant species within the An. funestus group and An. gambiae complex, respectively. Overall, outdoor CDC-LTs captured more Anopheles mosquitoes (mean = 2.25, 95% CI 1.22-3,28) than indoor CDC-LTs (mean = 2.13, 95% CI 1.54-2.73). Fewer resting mosquitoes were collected with PSC (mean = 0.44, 95% CI 0.24-0.63). Sporozoite infectivity rates for An. funestus, An. arabiensis and An. rufipes were 2.5%, 0.57% and 9.1%, respectively. Indoor entomological inoculation rates (EIRs) for An. funestus s.s, An. arabiensis and An. rufipes were estimated at 4.44, 1.15 and 1.20 infectious bites/person/year respectively. Outdoor EIRs for An. funestus s.s. and An. rufipes at 7.19 and 4.31 infectious bites/person/year, respectively.
CONCLUSION: The findings of this study suggest that An. rufipes may play an important role in malaria transmission alongside An. funestus s.s. and An. arabiensis in the study location.

Keywords:  Anopheles arabiensis; Anopheles funestus; Anopheles rufipes; Entomological inoculation rate; Vector-control; Zambia

DOI:  https://doi.org/10.1186/s12936-023-04489-3
Malar J. 2023 Mar 13. 22(1): 93

Species composition and insecticide resistance in malaria vectors in Ellibou, southern Côte d'Ivoire and first finding of Anopheles arabiensis in Côte d'Ivoire.

Bédjou P N'Dri, Nadja C Wipf, Jasmina Saric, Behi K Fodjo, Giovanna Raso, Jürg Utzinger, Pie Müller, Chouaïbou S Mouhamadou.

   BACKGROUND: Knowing the species composition and insecticide resistance status of the target vector population is important to guide malaria vector control. The aim of this study was to characterize the malaria vector population in terms of species composition, insecticide susceptibility status and potential underlying resistance mechanisms in Ellibou, southern Côte d'Ivoire.
METHODS: A 1-year longitudinal entomological survey was conducted using light traps and pyrethroid spray catches to sample adult mosquitoes in combination with larval sampling. The susceptibility status of Anopheles gambiae sensu lato (s.l.) to bendiocarb, deltamethrin, DDT and malathion was assessed using the World Health Organization insecticide susceptibility test. Additionally, An. gambiae specimens were screened for knockdown (kdr) and acetylcholineesterase (ace1) target site resistance alleles, and the expression levels of eight metabolic resistance genes, including seven cytochrome P450 monooxygenases (P450s) and one glutathione S-transferase (GST), measured with reverse transcription quantitative real-time polymerase chain reaction (qPCR).
RESULTS: Overall, 2383 adult mosquitoes from 12 different taxa were collected with Culex quinquefasciatus and An. gambiae being the predominant taxa. Molecular identification of An. gambiae s.l. revealed the presence of Anopheles arabiensis, Anopheles coluzzii, An. gambiae sensu stricto (s.s.) and Anopheles coluzzii/An. gambiae s.s. hybrids. Anopheles gambiae mosquitoes were resistant to all insecticides except malathion. PCR diagnostics revealed the presence of ace1-G280S and the kdr L995F, L995S and N1570Y target-site mutations. Additionally, several genes were upregulated, including five P450s (i.e., CYP6P3, CYP6M2, CYP9K1, CYP6Z1, CYP6P1) and GSTE2.
CONCLUSION: This is the first documented presence of An. arabiensis in Côte d'Ivoire. Its detection - together with a recent finding further north of the country - confirms its existence in the country, which is an early warning sign, as An. arabiensis shows a different biology than the currently documented malaria vectors. Because the local An. gambiae population was still susceptible to malathion, upregulation of P450s, conferring insecticide resistance to pyrethroids, together with the presence of ace1, suggest negative cross-resistance. Therefore, organophosphates could be an alternative insecticide class for indoor residual spraying in the Ellibou area, while additional tools against the outdoor biting An. arabiensis will have to be considered.

Keywords:  Anopheles arabiensis; Anopheles gambiae; Côte d’Ivoire; Insecticide resistance; Malaria; Metabolic resistance

DOI:  https://doi.org/10.1186/s12936-023-04456-y
Parasit Vectors. 2023 Mar 15. 16(1): 101

The interplay between malaria vectors and human activity accounts for high residual malaria transmission in a Burkina Faso village with universal ITN coverage.

Eleonora Perugini, Wamdaogo M Guelbeogo, Federica Guglielmo, Cristiana Poggi, Eugenio Gabrieli, Hilary Ranson, Alessandra Della Torre, Marco Pombi.

   BACKGROUND: Mosquito and human behaviour interaction is a key determinant of the maximum level of protection against malaria that can be provided by insecticide-treated nets (ITNs). Nevertheless, scant literature focuses on this interaction, overlooking a fundamental factor for efficient malaria control. This study aims to estimate malaria transmission risk in a Burkina Faso village by integrating vector biting rhythms with some key information about human habits.
METHODS: Indoor/outdoor human landing catches were conducted for 16 h (16:00-08:00) during 8 nights (September 2020) in Goden village. A survey about net usage and sleeping patterns was submitted to half the households (October-December 2020). A subsample of collected specimens of Anopheles gambiae sensu lato was molecularly processed for species identification, Plasmodium detection from heads-thoraxes and L1014F pyrethroid-resistance allele genotyping. Hourly mosquito abundance was statistically assessed by GLM/GAM, and the entomological inoculation rate (EIR) was corrected for the actual ITN usage retrieved from the questionnaire.
RESULTS: Malaria transmission was mainly driven by Anopheles coluzzii (68.7%) followed by A. arabiensis (26.2%). The overall sporozoite rate was 2% with L1014F estimated frequency of 0.68 (N = 1070 out of 15,201 A. gambiae s.l. collected). No major shift in mosquito biting rhythms in response to ITN or differences between indoor and outdoor catches were detected. Impressive high biting pressure (mean 30.3 mosquitoes/person/hour) was exerted from 20:00 to 06:00 with a peak at 4:00. Human survey revealed that nearly all inhabitants were awake before 20:00 and after 7:00 and at least 8.7% had no access to bednets. Adjusting for anthropological data, the EIR dropped from 6.7 to 1.2 infective bites/person/16 h. In a scenario of full net coverage and accounting only for the human sleeping patterns, the daily malaria transmission risk not targetable by ITNs was 0.69 infective bites.
CONCLUSIONS: The high mosquito densities and interplay between human/vector activities means that an estimated 10% of residual malaria transmission cannot be prevented by ITNs in the village. Locally tailored studies, like the current one, are essential to explore the heterogeneity of human exposure to infective bites and, consequently, to instruct the adoption of new vector control tools strengthening individual and community protection.

Keywords:  Anopheles arabiensis; Anopheles coluzzii; Biting rhythms; Entomological inoculation rate; Human exposure; Residual malaria transmission

DOI:  https://doi.org/10.1186/s13071-023-05710-7
Malar J. 2023 Mar 17. 22(1): 100

Trends of insecticide resistance monitoring in mainland Tanzania, 2004-2020.

Patrick Tungu, Bilali Kabula, Theresia Nkya, Pendael Machafuko, Edward Sambu, Bernard Batengana, Wema Sudi, Yahaya A Derua, Victor Mwingira, Denis Masue, Robert Malima, Chonge Kitojo, Naomi Serbantez, Erik J Reaves, Charles Mwalimu, Samwel L Nhiga, Mohamed Ally, Humphrey R Mkali, Joseph J Joseph, Adeline Chan, Jeremiah Ngondi, Shabbir Lalji, Ssanyu Nyinondi, Erin Eckert, Richard Reithinger, Stephen Magesa, William N Kisinza.

   BACKGROUND: Insecticide resistance is a serious threat to the continued effectiveness of insecticide-based malaria vector control measures, such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). This paper describes trends and dynamics of insecticide resistance and its underlying mechanisms from annual resistance monitoring surveys on Anopheles gambiae sensu lato (s.l.) populations conducted across mainland Tanzania from 2004 to 2020.
METHODS: The World Health Organization (WHO) standard protocols were used to assess susceptibility of the wild female An. gambiae s.l. mosquitoes to insecticides, with mosquitoes exposed to diagnostic concentrations of permethrin, deltamethrin, lambdacyhalothrin, bendiocarb, and pirimiphos-methyl. WHO test papers at 5× and 10× the diagnostic concentrations were used to assess the intensity of resistance to pyrethroids; synergist tests using piperonyl butoxide (PBO) were carried out in sites where mosquitoes were found to be resistant to pyrethroids. To estimate insecticide resistance trends from 2004 to 2020, percentage mortalities from each site and time point were aggregated and regression analysis of mortality versus the Julian dates of bioassays was performed.
RESULTS: Percentage of sites with pyrethroid resistance increased from 0% in 2004 to more than 80% in the 2020, suggesting resistance has been spreading geographically. Results indicate a strong negative association (p = 0.0001) between pyrethroids susceptibility status and survey year. The regression model shows that by 2020 over 40% of An. gambiae mosquitoes survived exposure to pyrethroids at their respective diagnostic doses. A decreasing trend of An. gambiae susceptibility to bendiocarb was observed over time, but this was not statistically significant (p = 0.8413). Anopheles gambiae exhibited high level of susceptibility to the pirimiphos-methyl in sampled sites.
CONCLUSIONS: Anopheles gambiae Tanzania's major malaria vector, is now resistant to pyrethroids across the country with resistance increasing in prevalence and intensity and has been spreading geographically. This calls for urgent action for efficient malaria vector control tools to sustain the gains obtained in malaria control. Strengthening insecticide resistance monitoring is important for its management through evidence generation for effective malaria vector control decision.

Keywords:  Insecticide resistance; Malaria vectors; Resistance trends; Tanzania

DOI:  https://doi.org/10.1186/s12936-023-04508-3
J Med Entomol. 2023 Mar 18. pii: tjad020. [Epub ahead of print]

Residual malaria transmission and the role of Anopheles arabiensis and Anopheles melas in central Senegal.

Ousmane Sy, Pape C Sarr, Benoit S Assogba, Mouhamed A Nourdine, Assane Ndiaye, Lassana Konaté, Ousmane Faye, Martin J Donnelly, Oumar Gaye, David Weetman, Elhadji A Niang.

  Understanding the behavior and ecology of local malaria vectors is essential for the effectiveness of the commonly used vector-targeted malaria control tools in areas of low malaria transmission. This study was conducted to determine species composition, biting behavior and infectivity of the major Anopheles vectors of Plasmodium falciparum in low transmission settings in central Senegal. Adult mosquitoes were collected using human landing catches during 2 consecutive nights and Pyrethrum Spray Catches in 30-40 randomly selected rooms, from July 2017 to December 2018 in 3 villages. Anopheline mosquitoes were morphologically identified using conventional keys; their reproductive status assessed by ovary dissections, and a sub-sample of Anopheles gambiae s.l. were identified to species level using polymerase chain reaction (PCR). Plasmodium sporozoite infections were detected using real-time quantitative PCR. During this study 3684 Anopheles were collected of which 97% were An. gambiae s.l., 0.6% were Anopheles funestus, and 2.4% were Anopheles pharoensis. Molecular identification of 1,877 An. gambiae s.l. revealed a predominance of Anopheles arabiensis (68.7%), followed by Anopheles melas (28.8%), and Anopheles coluzzii (2.1%). The overall human-biting rate of An. gambiae s.l. was highest in the inland site of Keur Martin with 4.92 bites per person per night, while it was similar in the deltaic site, Diofior (0.51) and the coastal site, Mbine Coly (0.67). Parity rates were similar in An. arabiensis (45%) and An. melas (42%). Sporozoite infections were detected in both An. arabiensis and An. melas with the respective infection rates of 1.39% (N = 8) and 0.41% (N = 1). Results suggest that low residual malaria in central Senegal is transmitted by An. arabiensis and An. melas. Consequently, both vectors will need to be targeted as part of malaria elimination efforts in this area of Senegal.

Keywords:  Senegal; elimination; hotspots; malaria; qPCR

DOI:  https://doi.org/10.1093/jme/tjad020
Malar J. 2023 Mar 14. 22(1): 94

Fine-scale spatial distribution of deltamethrin resistance and population structure of Anopheles funestus and Anopheles arabiensis populations in Southern Mozambique.

Smita Das, Mara Máquina, Keeley Phillips, Nelson Cuamba, Dulcisaria Marrenjo, Francisco Saúte, Krijn P Paaijmans, Silvie Huijben.

   BACKGROUND: Insecticide resistance in malaria vectors can be spatially highly heterogeneous, yet population structure analyses frequently find relatively high levels of gene flow among mosquito populations. Few studies have contemporaneously assessed phenotypic, genotypic and population structure analysis on mosquito populations and none at fine geographical scales. In this study, genetic diversity, population structure, and insecticide resistance profiles of Anopheles funestus and Anopheles arabiensis were examined across mosquito populations from and within neighbouring villages.
METHODS: Mosquitoes were collected from 11 towns in southern Mozambique, as well as from different neighbourhoods within the town of Palmeira, during the peak malaria transmission season in 2016. CDC bottle bioassay and PCR assays were performed with Anopheles mosquitoes at each site to determine phenotypic and molecular insecticide resistance profiles, respectively. Microsatellite analysis was conducted on a subsample of mosquitoes to estimate genetic diversity and population structure.
RESULTS: Phenotypic insecticide resistance to deltamethrin was observed in An. funestus sensu stricto (s.s.) throughout the area, though a high level of mortality variation was seen. However, 98% of An. funestus s.s. were CYP6P9a homozygous resistant. An. arabiensis was phenotypically susceptible to deltamethrin and 99% were kdr homozygous susceptible. Both Anopheles species exhibited high allelic richness and heterozygosity. Significant deviations from Hardy-Weinberg equilibrium were observed, and high linkage disequilibrium was seen for An. funestus s.s., supporting population subdivision. However, the FST values were low for both anophelines (- 0.00457 to 0.04213), Nm values were high (9.4-71.8 migrants per generation), AMOVA results showed almost 100% genetic variation among and within individuals, and Structure analysis showed no clustering of An. funestus s.s. and An. arabiensis populations. These results suggest high gene flow among mosquito populations.
CONCLUSION: Despite a relatively high level of phenotypic variation in the An. funestus population, molecular analysis shows the population is admixed. These data indicate that CYP6P9a resistance markers do not capture all phenotypic variation in the area, but also that resistance genes of high impact are likely to easily spread in the area. Conversely, other strategies, such as transgenic mosquito release programmes will likely not face challenges in this locality.

Keywords:  Anopheles funestus; Anopheles gambiae; Gene flow; Insecticide resistance; Malaria; Population genetics; Surveillance

DOI:  https://doi.org/10.1186/s12936-023-04522-5
Front Microbiol. 2023 ;14 1105786

Survey of mosquito species and mosquito-borne viruses in residential areas along the Sino-Vietnam border in Yunnan Province in China.

Fengjuan Tian, Jimin He, Shanlin Shang, Zhongyan Chen, Yumei Tang, Man Lu, Changzhi Huang, Xiaofang Guo, Yigang Tong.

  Mosquitoes are capable of carrying complex pathogens, and their feeding habits on the mammalian blood can easily mediate the spread of viruses. Surveillance of mosquito-based arbovirus enables the early prevention and control of mosquito-borne arboviral diseases. The climate and geography of Yunnan Province in China are ideal for mosquitoes. Yunnan shares borders with several other countries; therefore, there exists a high risk of international transmission of mosquito-mediated infectious diseases. Previous studies have focused more on the Sino-Laos and Sino-Myanmar borders. Therefore, we focused on the neighborhoods of Malipo and Funing counties in Wenshan Prefecture, Yunnan Province, China, which are located along the Sino-Vietnam border, to investigate the species of mosquitoes and mosquito-borne viruses in the residential areas of this region. This study collected 10,800 mosquitoes from 29 species of 8 genera and grouped to isolate mosquito-borne viruses. In total, 62 isolates were isolated and classified into 11 viral categories. We demonstrated a new distribution of mosquito-borne viruses among mosquitoes in border areas, including Tembusu and Getah viruses, which can cause animal outbreaks. In addition, Dak Nong and Sarawak viruses originating from Vietnam and Malaysia, respectively, were identified for the first time in China, highlighting the complexity of mosquito-borne viruses in the Sino-Vietnam border region. The awareness of the importance of viral surveillance and prevention measures in border areas should be further encouraged to prevent future outbreaks of potentially infectious diseases.

Keywords:  Sino–Vietnam border; arbovirus; mosquito; mosquito-borne viruses; virus isolation

DOI:  https://doi.org/10.3389/fmicb.2023.1105786
Parasit Vectors. 2023 Mar 15. 16(1): 99

Evaluating the mosquito host range of Getah virus and the vector competence of selected medically important mosquitoes in Getah virus transmission.

Faustus Akankperiwen Azerigyik, Astri Nur Faizah, Daisuke Kobayashi, Michael Amoa-Bosompem, Ryo Matsumura, Izumi Kai, Toshinori Sasaki, Yukiko Higa, Haruhiko Isawa, Shiroh Iwanaga, Tomoko Ishino.

   BACKGROUND: The Getah virus (GETV) is a mosquito-borne Alphavirus (family Togaviridae) that is of significant importance in veterinary medicine. It has been associated with major polyarthritis outbreaks in animals, but there are insufficient data on its clinical symptoms in humans. Serological evidence of GETV exposure and the risk of zoonotic transmission makes GETV a potentially medically relevant arbovirus. However, minimal emphasis has been placed on investigating GETV vector transmission, which limits current knowledge of the factors facilitating the spread and outbreaks of GETV.
METHODS: To examine the range of the mosquito hosts of GETV, we selected medically important mosquitoes, assessed them in vitro and in vivo and determined their relative competence in virus transmission. The susceptibility and growth kinetics of GETVs in various mosquito-derived cell lines were also determined and quantified using plaque assays. Vector competency assays were also conducted, and quantitative reverse transcription-PCR and plaque assays were used to determine the susceptibility and transmission capacity of each mosquito species evaluated in this study.
RESULTS: GETV infection in all of the investigated mosquito cell lines resulted in detectable cytopathic effects. GETV reproduced the fastest in Culex tritaeniorhynchus- and Aedes albopictus-derived cell lines, as evidenced by the highest exponential titers we observed. Regarding viral RNA copy numbers, mosquito susceptibility to infection, spread, and transmission varied significantly between species. The highest vector competency indices for infection, dissemination and transmission were obtained for Cx. tritaeniorhynchus. This is the first study to investigate the ability of Ae. albopictus and Anopheles stephensi to transmit GETV, and the results emphasize the role and capacity of other mosquito species to transmit GETV upon exposure to GETV, in addition to the perceived vectors from which GETV has been isolated in nature.
CONCLUSIONS: This study highlights the importance of GETV vector competency studies to determine all possible transmission vectors, especially in endemic regions.

Keywords:  Alphavirus; Arbovirus; Culex tritaeniorhynchus; Getah virus; Mosquito-borne; Susceptibility; Transmission; Vector competence

DOI:  https://doi.org/10.1186/s13071-023-05713-4
Acta Trop. 2023 Mar 10. pii: S0001-706X(23)00078-5. [Epub ahead of print] 106891

First report of natural Wolbachia infections in mosquitoes from Cuba.

Armando Ruiz, Gladys Gutiérrez-Bugallo, Rosmari Rodríguez-Roche, Lissette Pérez, Raúl González-Broche, Luis A Piedra, Liss C Martínez, Zulema Menéndez, Anubis Vega-Rúa, Juan A Bisset.

  Mosquitoes are extensively responsible for the transmission of pathogens. Novel strategies using Wolbachia could transform that scenario, since these bacteria manipulate mosquito reproduction, and can confer a pathogen transmission-blocking phenotype in culicids. Here, we screened the Wolbachia surface protein region by PCR in eight Cuban mosquito species. We confirmed the natural infections by sequencing and assessed the phylogenetic relationships among the Wolbachia strains detected. We identified four Wolbachia hosts: Aedes albopictus, Culex quinquefasciatus, Mansonia titillans, and Aedes mediovittatus (first report worldwide). Knowledge of Wolbachia strains and their natural hosts is essential for future operationalization of this vector control strategy in Cuba.

Keywords:  Wolbachia; culicid; endosymbiont; vector control; wsp gene

DOI:  https://doi.org/10.1016/j.actatropica.2023.106891
Infez Med. 2022 ;31(1): 20-30

West Nile Virus diffusion in temperate regions and climate change. A systematic review.

Chiara D'Amore, Pierantonio Grimaldi, Tiziana Ascione, Valeria Conti, Carmine Sellitto, Gianluigi Franci, Samadi Hossein Kafil, Pasquale Pagliano.

  West Nile virus (WNV) is a member of the Japanese encephalitis serocomplex, which was first described in 1937 as neurotropic virus in Uganda in 1937. Subsequently, WNV was identified in the rest of the old-world and from 1999 in North America. Birds are the primary hosts, and WNV is maintained in a bird-mosquito-bird cycle, with pigs as amplifying hosts and humans and horses as incidental hosts. WNV transmission is warranted by mosquitoes, usually of the Culex spp., with a tendency to spill over when mosquitoes' populations build up. Other types of transmissions have been described in endemic areas, as trough transplanted organs and transfused blood, placenta, maternal milk, and in some occupational settings. WNV infections in North America and Europe are generally reported during the summer and autumn. Extreme climate phenomena and soil degradation are important events which contribute to expansion of mosquito population and consequently to the increasing number of infections. Draught plays a pivotal role as it makes foul water standing in city drains and catch basins richer of organic material. The relationship between global warming and WNV in climate areas is depicted by investigations on 16,298 WNV cases observed in the United States during the period 2001-2005 that showed that a 5°C increase in mean maximum weekly temperature was associated with a 32-50% higher incidence of WNV infection. In Europe, during the 2022 season, an increase of WNV cases was observed in Mediterranean countries where 1,041 cases were reported based on ECDC data. This outbreak can be associated to the climate characteristics reported during this period and to the introduction of a new WNV-1 lineage. In conclusion, current climate change is causing an increase of mosquito circulation that supports the widest spread of some vector-borne virus including WNV diffusion in previously non-permissible areas. This warrant public health measures to control vectors circulation to reduce WNV and to screen blood and organ donations.

Keywords:  WNV; complications; encephalitis; meningitis; treatment

DOI:  https://doi.org/10.53854/liim-3101-4
J Parasit Dis. 2023 Mar;47(1): 161-166

Entomological survey of malaria vectors in Dashtestan County, South of Iran.

Zahra Nasiri, Zahra-Sadat Hosseinizadeh, Zeinab Sayyadi, Hamzeh Alipour.

  Anopheline mosquitoes are responsible for transmission of some diseases such as malaria. This study was carried out in five villages of Dashtestan county, Bushehr province, south of Iran with mountainous and plain areas. Anopheles larvae were sampled once a month from May to July 2021 by dipping method using standard dippers. Adults were captured by the total catch technique. In this study, 1062 Anopheles mosquitoes were collected including 850 adults and 212 larvae. Samples were A. superpictus, A. stephensi, A. dthali and A. fluviatilis. The dominant species at all sites (larvae and adults) were A. dthali (31.35%), A. superpictus (28.93%), A. stephensi (27.77%), and A. fluviatilis (11.95%), respectively. Among adults, A. stephensi was the most frequent species, but among larvae, A. dthali was the dominant species. The highest number of A. dthali was captured from Dalaki village with 35%, while A. superpictus and A. fluviatilis were not caught at this station. The minimum collected adults of all species occurred in Bashirabad. This result showed that A. stephensi plays an important role in south Iran, which is under the elimination phase. The fauna and niches of Anopheles has different patterns depending on ecological, climatic, and topographic features. These items affect host preferences, feeding behaviors, and distribution of these species. A monthly or annual entomological survey is necessary in regions with mobile populations since imported malaria is a problematic issue in the elimination programs of Iran.

Keywords:  Anopheles; Culicidae; Iran; Total catch

DOI:  https://doi.org/10.1007/s12639-022-01555-6
PLoS Negl Trop Dis. 2023 Mar 16. 17(3): e0011197

Sociodemographic and environmental factors associated with dengue, Zika, and chikungunya among adolescents from two Brazilian capitals.

Ana Paula Razal Dalvi, Gerusa Gibson, Alberto Novaes Ramos, Katia V Bloch, Geziel Dos Santos de Sousa, Thiago Luiz Nogueira da Silva, José Ueleres Braga, Marcia C Castro, Guilherme Loureiro Werneck.

Among the emerging and reemerging arboviral diseases, Zika, dengue and chikungunya deserve special attention due to their wide geographical distribution and clinical severity. The three arboviruses are transmitted by the same vector and can present similar clinical syndromes, bringing challenges to their identification and register. Demographic characteristics and individual and contextual social factors have been associated with the three arboviral diseases. However, little is known about such associations among adolescents, whose relationships with the social environment are different from those of adult populations, implying potentially different places, types, and degrees of exposure to the vector, particularly in the school context. This study aims to identify sociodemographic and environmental risk factors for the occurrence of Zika, dengue, and chikungunya in a cohort of adolescents from the Study of Cardiovascular Risks in Adolescents-ERICA-in the cities of Rio de Janeiro/RJ and Fortaleza/CE, from January 2015 to March 2019. Cases were defined as adolescents with laboratory or clinical-epidemiological diagnosis of Zika, dengue, or chikungunya, notified and registered in the Information System for Notifiable Diseases (SINAN). The cases were identified by linkage between the databases of the ERICA cohort and of SINAN. Multilevel Cox regression was employed to estimate hazard ratios (HR) as measures of association and respective 95% confidence intervals (95%CI). In comparison with adolescents living in lower socioeconomic conditions, the risk of becoming ill due to any of the three studied arboviral diseases was lower among those living in better socioeconomic conditions (HR = 0.43; 95%CI: 0.19-0.99; p = 0.047) and in the adolescents who attended school in the afternoon period (HR = 0.17; 95%CI: 0.06-0.47; p<0.001). When compared to areas whose Building Infestation Index (BII) for Aedes aegypti was considered satisfactory, a BII in the school region classified as "alert" and "risk" was associated with a higher risk of arboviral diseases (HR = 1.62, 95%CI: 0.98-2.70; p = 0.062; HR = 3.72, 95%CI: 1.27-10.9; p = 0.017, respectively). These findings indicate that living in less favored socioeconomic conditions, attending school in the morning, and having a high BII for Ae. aegypti in school's region can contribute to an increased risk of infection by Zika, dengue, or chikungunya in adolescents. The identification of residential or school areas based on those variables can contribute to the implementation of control measures in population groups and priority locations.

DOI: https://doi.org/10.1371/journal.pntd.0011197
Heliyon. 2023 Mar;9(3): e14005

Spatio-temporal analysis of environmental and climatic factors impacts on malaria morbidity in Ondo State, Nigeria.

Dave Eleojo Ekpa, Eunice A Salubi, Johnson Adedeji Olusola, Dare Akintade.

  This study examined the spatio-temporal dynamics of malaria epidemiological patterns considering environmental(vegetation, water bodies, slope, elevation) and climatic factors (rainfall, temperature and relative humidity) in Ondo State, Nigeria, from 2013 to 2017 using ArcGIS 10.4 and QGIS software. The factors influencing malaria were studied using a multi-criteria analysis (Analytical Hierarchical Process-AHP). The trend analysis revealed an increase in cases over time, indicating a significant increase in the occurrence of malaria in all study areas. The most important climatic variable impacting malaria transmission in the study was temperature. Nevertheless, other environmental and climatic factors causing transmission include vegetation, water bodies, slopes, elevation, rainfall, and relative humidity. With the exception of Okitipupa, the study identified high-risk locations (vulnerable areas/hot spots) in almost all of the local government areas, while Ondo East, Akure South, Akoko South West, and Owo are the most vulnerable areas. The findings reveal that the malaria incidence is high in the developed LGAs having more towns where temperature is higher due to several anthropogenesis activities, high population and increased land-use. Thus, in-depth epidemiological studies on malaria should be undertaken in Ondo State and other regions of Nigeria considering environmental factors impacting malaria incidence as this will enable one to ascertain the major factors influencing the disease, thereby taking adequate measures to curb the increase in incidence.

Keywords:  Climatic factors; Environmental; Malaria; Morbidity; Spatio-temporal

DOI:  https://doi.org/10.1016/j.heliyon.2023.e14005
Virus Evol. 2023 ;9(1): vead012

A phylogenetic study of dengue virus in urban Vietnam shows long-term persistence of endemic strains.

James Ashall, Sonal Shah, Joseph R Biggs, Jui-Ning R Chang, Yalda Jafari, Oliver J Brady, Huynh Kim Mai, Le Thuy Lien, Hung Do Thai, Hien Anh Thi Nguyen, Dang Duc Anh, Chihiro Iwasaki, Noriko Kitamura, Marnix Van Loock, Guillermo Herrera-Taracena, Freya Rasschaert, Liesbeth Van Wesenbeeck, Lay-Myint Yoshida, Julius Clemence R Hafalla, Stephane Hue, Martin L Hibberd.

  Dengue virus (DENV) causes repeated outbreaks of disease in endemic areas, with patterns of local transmission strongly influenced by seasonality, importation via human movement, immunity, and vector control efforts. An understanding of how each of these interacts to enable endemic transmission (continual circulation of local virus strains) is largely unknown. There are times of the year when no cases are reported, often for extended periods of time, perhaps wrongly implying the successful eradication of a local strain from that area. Individuals who presented at a clinic or hospital in four communes in Nha Trang, Vietnam, were initially tested for DENV antigen presence. Enrolled positive individuals then had their corresponding household members invited to participate, and those who enrolled were tested for DENV. The presence of viral nucleic acid in all samples was confirmed using quantitative polymerase chain reaction, and positive samples were then whole-genome sequenced using an amplicon and target enrichment library preparation techniques and Illumina MiSeq sequencing technology. Generated consensus genome sequences were then analysed using phylogenetic tree reconstruction to categorise sequences into clades with a common ancestor, enabling investigations of both viral clade persistence and introductions. Hypothetical introduction dates were additionally assessed using a molecular clock model that calculated the time to the most recent common ancestor (TMRCA). We obtained 511 DENV whole-genome sequences covering four serotypes and more than ten distinct viral clades. For five of these clades, we had sufficient data to show that the same viral lineage persisted for at least several months. We noted that some clades persisted longer than others during the sampling time, and by comparison with other published sequences from elsewhere in Vietnam and around the world, we saw that at least two different viral lineages were introduced into the population during the study period (April 2017-2019). Next, by inferring the TMRCA from the construction of molecular clock phylogenies, we predicted that two of the viral lineages had been present in the study population for over a decade. We observed five viral lineages co-circulating in Nha Trang from three DENV serotypes, with two likely to have remained as uninterrupted transmission chains for a decade. This suggests clade cryptic persistence in the area, even during periods of low reported incidence.

Keywords:  dengue; persistence; phylogenetics; pransmission; sequencing; virus

DOI:  https://doi.org/10.1093/ve/vead012
Open Forum Infect Dis. 2023 Mar;10(3): ofad076

Malaria Control by Mass Drug Administration With Artemisinin Plus Piperaquine on Grande Comore Island, Union of Comoros.

Changsheng Deng, Wanting Wu, Yueming Yuan, Guoming Li, Hongying Zhang, Shaoqin Zheng, Mingqiang Li, Ruixiang Tan, Yuxin Wang, Julie Nadia, Danhong Feng, Di Li, Zhibing Wu, Qin Xu, Changqing Li, Zhenhua Wang, Yuan Liang, Johannes S P Doehl, Xinzhuan Su, Affane Bacar, Kamal Said Abdallah, Hafidhou Mohamed, Ahamada Msa Mliva, Thomas E Wellems, Jianping Song.

   Background: Mass drug administration (MDA) is a powerful tool for malaria control, but the medicines to use, dosing, number of rounds, and potential selection of drug resistance remain open questions.
Methods: Two monthly rounds of artemisinin-piperaquine (AP), each comprising 2 daily doses, were administered across the 7 districts of Grande Comore Island. In 3 districts, low-dose primaquine (PMQLD) was also given on the first day of each monthly round. Plasmodium falciparum malaria rates, mortality, parasitemias, adverse events, and genetic markers of potential drug resistance were evaluated.
Results: Average population coverages of 80%-82% were achieved with AP in 4 districts (registered population 258 986) and AP + PMQLD in 3 districts (83 696). The effectiveness of MDA was 96.27% (95% confidence interval [CI], 95.27%-97.06%; P < .00001) in the 4 AP districts and 97.46% (95% CI, 94.54%-98.82%; P < .00001) in the 3 AP + PMQLD districts. In comparative statistical modeling, the effectiveness of the 2 monthly rounds on Grande Comore Island was nearly as high as that of 3 monthly rounds of AP or AP + PMQLD in our earlier study on Anjouan Island. Surveys of pre-MDA and post-MDA samples showed no significant changes in PfK13 polymorphism rates, and no PfCRT mutations previously linked to piperaquine resistance in Southeast Asia were identified.
Conclusions: MDA with 2 monthly rounds of 2 daily doses of AP was highly effective on Grande Comore Island. The feasibility and lower expense of this 2-month versus 3-month regimen of AP may offer advantages for MDA programs in appropriate settings.

Keywords:  Plasmodium falciparum malaria; artemisinin-based combination therapy; chloroquine resistance transporter (PfCRT); pfK13 kelch-propeller mutations; piperaquine resistance

DOI:  https://doi.org/10.1093/ofid/ofad076