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Marcombe S, Maithaviphet S, Reyburn R, Kunlaya K, Silavong K, Hongvanthong B, Vanisaveth V, Sengsavath V, Banouvong V, Chindavongsa K, Khamlome B, Shortus M. Bionomics of malaria vectors in Lao PDR, 2018-2020: entomological surveillance as a key tool for malaria elimination. Malar J 2023; 22:319. [PMID: 37865735 PMCID: PMC10589990 DOI: 10.1186/s12936-023-04754-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 10/13/2023] [Indexed: 10/23/2023] Open
Abstract
BACKGROUND The Lao PDR National Strategic Plan for malaria control and elimination for year 2021-2025 emphasizes the importance of routine entomological surveillance being conducted in areas with high transmission and in active malaria foci in elimination targeted areas. The collection of entomological surveillance data that is closely linked to recent epidemiological data is crucial for improving impact, as it contributes to the evidence package that supports operational and strategic decision-making of national malaria programmes, as they accelerate their last mile of elimination. METHODS The Center for Malariology Parasitology and Epidemiology (CMPE) entomology team conducted entomological surveillance activities at 13 sentinel sites in 8 provinces and at active transmission foci sites from 2018 to 2020. The techniques used for the mosquito collection were indoor and outdoor human landing collections (from houses and from cultivation areas) and cattle baited net trap collections. RESULTS There were 5601 Anopheles mosquito females captured and identified throughout the study, on both human and cow bait. They represented 15 different species or species complexes. The primary malaria vectors as well as the secondary vectors were present in all collection sites in the south, indicating that people living in these rural areas with high malaria incidence are exposed to the vectors. The vectors were highly zoophilic, but they still bite humans throughout the night with a high peak of activity before midnight, both indoors and outdoors. Overall, 17% of the malaria vectors were collected indoors when the people are sleeping. This confirms the importance of bed net use during the night. Thirty-two percent of primary and secondary vectors were collected outdoors at times when people are usually awake and outdoors, which shows that people are exposed to potentially infectious mosquitoes and the importance of personal protection at these times. The findings showed that residual transmission may occur outdoors in the villages, and outside the villages in cultivation fields and forested areas. Epidemiological data showed that transmission was higher in surveillance sites which were targeted as part of a malaria response rather than sentinel sites. CONCLUSIONS Understanding where and how transmission is persisting, monitoring and mapping vector species distribution in areas with active transmission, monitoring biting trends, and designing evidence based and effective vector control interventions are critical to accelerating progress toward malaria elimination. In this context, the role of entomological surveillance combined with epidemiological data should be considered as a cornerstone in achieving malaria elimination.
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Affiliation(s)
| | - Santi Maithaviphet
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Rita Reyburn
- World Health Organization, Saphanthong Tai Rd, Vientiane, Laos
| | | | - Khambang Silavong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Bouasy Hongvanthong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Viengxay Vanisaveth
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Viengphone Sengsavath
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Vilasack Banouvong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | | | - Boualam Khamlome
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Matthew Shortus
- World Health Organization, Saphanthong Tai Rd, Vientiane, Laos
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Vu NS, Hertz JC, Martin NJ, Tran TC, Fiorenzano JM, Tran PV, Nguyen HV, Dang AD, Tran DN, Motoki MT. Mosquitoes (Diptera: Culicidae) from Villages and Forest Areas of Rural Communes in Khanh Hoa and Binh Phuoc Provinces, Vietnam. JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:2264-2273. [PMID: 34144599 PMCID: PMC8577722 DOI: 10.1093/jme/tjab106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Indexed: 06/12/2023]
Abstract
This study presents the diversity of mosquitoes collected from communes, endemic with malaria and dengue, located in Khanh Hoa and Binh Phuoc Provinces, Vietnam. A total of 10,288 mosquitoes were collected in the village and forested sites using standard larval dippers, cow-baited traps, ultra-violet light traps, and mechanical aspirators. Mosquito taxa were identified morphologically and species complexes/groups were further characterized molecularly. Five genera of mosquitoes were morphologically identified: Anopheles Meigen (21 species), Aedes Meigen (2 species), Culex Linnaeus (5 species), Mansonia Blanchard sp., and Armigeres Theobald sp. The PCR-based identification methods allowed the distinction of members of Maculatus Group, Funestus Group, and Dirus Complex; and DNA barcodes enabled the further identification of the Barbirostris Complex. Data reported here include the first report of An. saeungae Taai & Harbach and An. wejchoochotei Taai & Harbach from Vietnam, and re-emphasizes the significance of using molecular data in an integrated systematic approach to identify cryptic species and better understand their role in disease transmission.
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Affiliation(s)
- Nam S Vu
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | | | | | - Tu C Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | | | - Phong V Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Hoang V Nguyen
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Anh D Dang
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Duong N Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Maysa T Motoki
- Vysnova Partners Inc., Landover, MD, USA
- Department of Entomology, Natural Museum of Natural History, Smithsonian Institution, Museum Support Center, Suitland, MD, USA
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Maquart PO, Fontenille D, Rahola N, Yean S, Boyer S. Checklist of the mosquito fauna (Diptera, Culicidae) of Cambodia. ACTA ACUST UNITED AC 2021; 28:60. [PMID: 34374642 PMCID: PMC8354007 DOI: 10.1051/parasite/2021056] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 07/04/2021] [Indexed: 11/14/2022]
Abstract
Between 2016 and 2020, the Medical and Veterinary Entomology unit of the Institut Pasteur du Cambodge collected over 230,000 mosquitoes. Based on this sampling effort, a checklist of 290 mosquito species in Cambodia is presented. This is the first attempt to list the Culicidae fauna of the country. We report 49 species for the first time in Cambodia. The 290 species belong to 20 genera: Aedeomyia (1 sp.), Aedes (55 spp.), Anopheles (53 spp.), Armigeres (26 spp.), Coquillettidia (3 spp.), Culex (57 spp.), Culiseta (1 sp.), Ficalbia (1 sp.), Heizmannia (10 spp.), Hodgesia (3 spp.), Lutzia (3 spp.), Malaya (2 spp.), Mansonia (5 spp.), Mimomyia (7 spp.), Orthopodomyia (3 spp.), Topomyia (4 spp.), Toxorhynchites (4 spp.), Tripteroides (6 spp.), Uranotaenia (27 spp.), and Verrallina (19 spp.). The Cambodian Culicidae fauna is discussed in its Southeast Asian context. Forty-three species are reported to be of medical importance, and are involved in the transmission of pathogens.
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Affiliation(s)
- Pierre-Olivier Maquart
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
| | - Didier Fontenille
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia - MIVEGEC, University of Montpellier, CNRS, IRD, 911 Avenue Agropolis, 34394 Montpellier, France
| | - Nil Rahola
- MIVEGEC, University of Montpellier, CNRS, IRD, 911 Avenue Agropolis, 34394 Montpellier, France
| | - Sony Yean
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
| | - Sébastien Boyer
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
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Marcombe S, Maithaviphet S, Bobichon J, Phommavan N, Nambanya S, Corbel V, Brey PT. New insights into malaria vector bionomics in Lao PDR: a nationwide entomology survey. Malar J 2020; 19:396. [PMID: 33168012 PMCID: PMC7654023 DOI: 10.1186/s12936-020-03453-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 10/18/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In Laos, the malaria burden remains high despite a significant reduction of cases during the last decade. In the context of the disease elimination by 2030, a nationwide entomological survey was conducted to better understand the distribution, abundance and behaviour of major malaria vectors (Anopheles spp.) in the country. METHODS Mosquito collections were implemented in ten villages from ten provinces during the rainy and dry seasons of 2014 and 2015 by using human landing catch (HLC) and cow bait collection (CBC) methods. After morphological identification in the field, molecular identification of the sibling species of Anopheles mosquitoes from the Funestus, Leucosphyrus, and Maculatus groups were determined using PCR specific alleles. A screening of Plasmodium falciparum and Plasmodium vivax infections in the vectors was carried out by quantitative PCR assays. RESULTS A total of 14,146 adult mosquitoes representing 25 different Anopheles species were collected and morphologically identified. Molecular identification revealed the presence of 12 sibling species within the main primary vector groups, including Anopheles maculatus, Anopheles rampae, Anopheles sawadwongporni, Anopheles pseudowillmori, Anopheles dravidicus, Anopheles minimus, Anopheles aconitus, Anopheles pampanai, Anopheles harrisoni, Anopheles dirus, Anopheles baimaii, Anopheles nemophilous. Anopheles maculatus and An. minimus were predominant during both the dry and rainy seasons, but showed highly zoophilic preferences (Zoophilic index of 98% and 95%, respectively). Overall, 22% of the total malaria vectors were collected between 10:00 PM and 5:00 AM indoors when people are sleeping. Twenty-seven percent of primary and secondary vectors were collected outdoors before 10:00 PM or after 5:00 AM, times when people are usually awake and outdoors. Only two specimens were positive for P. falciparum, one An. aconitus from Phongsaly and one An. minimus from Vientiane Province CONCLUSIONS: The results indicate that people living in rural areas in Laos are constantly exposed to malaria vectors throughout the year and specifically outdoors. The use of LLINs/IRS remains important but innovative tools and new strategies are needed to address locally, the early and outdoor malaria transmission. Lack of expertise in general entomological methods may further exacerbate the situation.
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Affiliation(s)
| | - Santi Maithaviphet
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Julie Bobichon
- Institut Pasteur du Laos, Ministry of Health, Vientiane, Lao PDR
| | | | - Simone Nambanya
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Vincent Corbel
- Institut de Recherche Pour Le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC, UM1-CNRS 5290-IRD 224), Montpellier, France
| | - Paul T Brey
- Institut Pasteur du Laos, Ministry of Health, Vientiane, Lao PDR
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High diversity of mosquito vectors in Cambodian primary schools and consequences for arbovirus transmission. PLoS One 2020; 15:e0233669. [PMID: 32502226 PMCID: PMC7274438 DOI: 10.1371/journal.pone.0233669] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 05/12/2020] [Indexed: 11/19/2022] Open
Abstract
Only few data exist in Cambodia on mosquito diversity and their potential role as vectors. Many arboviruses, such as dengue and Japanese encephalitis, are endemic and mostly affect children in the country. This research sets out to evaluate vector relative abundance and diversity in primary schools in Cambodia in an attempt to explain the apparent burden of dengue fever, severe dengue (DEN), Japanese encephalitis (JE), other arboviral diseases and malaria among children, 15 years and under, attending selected primary schools through vector surveys. Entomological surveys were implemented in primary schools in two provinces of Cambodia to assess the potential risk of exposure of schoolchildren to mosquito vector species. Light traps and BG traps were used to collect adult mosquitoes in 24 schools during the rainy and dry seasons of 2017 and 2018 in Kampong Cham and Tboung Khmum provinces. A total of 61 species were described, including Aedes, Culex and Anopheles species. The relative abundance and biodiversity of mosquito species were dependent on the month and school. Of the 37,725 mosquitoes caught during the study, three species accounted for three-quarters of the relative abundance: Culex vishnui, Anopheles indefinitus and Culex quinquefasciatus. More importantly, nearly 90% of the mosquitoes caught in the schools were identified as potential vectors of pathogens including Japanese encephalitis, dengue, and malaria parasites. Our results showed that schools in Cambodia represent a risk for vector-borne disease transmission and highlight the importance of implementing vector control in schools in Cambodia to decrease the risk of transmission.
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Miot EF, Calvez E, Aubry F, Dabo S, Grandadam M, Marcombe S, Oke C, Logan JG, Brey PT, Lambrechts L. Risk of arbovirus emergence via bridge vectors: case study of the sylvatic mosquito Aedes malayensis in the Nakai district, Laos. Sci Rep 2020; 10:7750. [PMID: 32385369 PMCID: PMC7210265 DOI: 10.1038/s41598-020-64696-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 04/03/2020] [Indexed: 12/20/2022] Open
Abstract
Many emerging arboviruses of global public health importance, such as dengue virus (DENV) and yellow fever virus (YFV), originated in sylvatic transmission cycles involving wild animals and forest-dwelling mosquitoes. Arbovirus emergence in the human population typically results from spillover transmission via bridge vectors, which are competent mosquitoes feeding on both humans and wild animals. Another related, but less studied concern, is the risk of 'spillback' transmission from humans into novel sylvatic cycles. We colonized a sylvatic population of Aedes malayensis from a forested area of the Nakai district in Laos to evaluate its potential as an arbovirus bridge vector. We found that this Ae. malayensis population was overall less competent for DENV and YFV than an urban population of Aedes aegypti. Olfactometer experiments showed that our Ae. malayensis colony did not display any detectable attraction to human scent in laboratory conditions. The relatively modest vector competence for DENV and YFV, combined with a lack of detectable attraction to human odor, indicate a low potential for this sylvatic Ae. malayensis population to act as an arbovirus bridge vector. However, we caution that opportunistic blood feeding on humans by sylvatic Ae. malayensis may occasionally contribute to bridge sylvatic and human transmission cycles.
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Affiliation(s)
- Elliott F Miot
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France. .,Sorbonne Université, Collège doctoral, Paris, France. .,Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao PDR.
| | - Elodie Calvez
- Arbovirus and Emerging Viral diseases Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Fabien Aubry
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
| | - Stéphanie Dabo
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
| | - Marc Grandadam
- Arbovirus and Emerging Viral diseases Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Sébastien Marcombe
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Catherine Oke
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - James G Logan
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Paul T Brey
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Louis Lambrechts
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France.
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Marcombe S, Thammavong P, Luangamath P, Chonephetsarath S, Phommavanh N, Lakeomany K, Nilaxay S, Rahmani Z, Saverton PJ, Abdullateef OH, Forward J, Jacob AE, Khadam S, Ali W, Boer C, Kakinuma H, Hawkins J, Longstreeth R, Portwood NM, Smee M, Brown N, Kuyucu NC, Lechmere S, Stieger G, Maithaviphet S, Nambanya S, Brey PT, Jones AK. Malaria and Dengue Mosquito Vectors from Lao PDR Show a Lack of the rdl Mutant Allele Responsible for Cyclodiene Insecticide Resistance. JOURNAL OF MEDICAL ENTOMOLOGY 2020; 57:815-823. [PMID: 31807752 DOI: 10.1093/jme/tjz227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Indexed: 06/10/2023]
Abstract
The gamma-aminobutyric acid (GABA) receptor, RDL, plays important roles in neuronal signaling and is the target of highly effective insecticides. A mutation in RDL, commonly A296S, underlies resistance to several insecticides such as cyclodienes. Even though the use of cyclodienes has been banned, the occurrence of mutations substituting A296 is notably high in mosquitoes from several countries. Here, we report a survey investigating the prevalence of the Rdl mutant allele in mosquitoes from Laos, a country where mosquito-borne diseases such as malaria and dengue fever are health concerns. Anopheles and Aedes mosquitoes were collected from 12 provinces in Laos. Adult bioassays on Aedes aegypti (Linnaeus) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) showed that all the populations tested were susceptible to dieldrin (4%) following WHO protocols. Exon 7 from a total of 791 mosquitoes was sequenced to identify the amino acid encoded for at 296 of RDL. Only one of these mosquitoes, Anopheles maculatus rampae Harbach and Somboon (Diptera: Culicidae) from Attapeu, carried the mutant allele being heterozygous for A296S. We therefore found a general lack of the Rdl mutant allele indicating that mosquitoes from Laos are not exposed to insecticides that act on the GABA receptor compared to mosquitoes in several other countries. Identifying the prevalence of the Rdl mutation may help inform the potential use of alternative insecticides that act on the GABA receptor should there be a need to replace pyrethroids in order to prevent/manage resistance.
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Affiliation(s)
- Sebastien Marcombe
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Phoutmany Thammavong
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Phonesavanh Luangamath
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | | | - Nothasin Phommavanh
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Khaitong Lakeomany
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Somphat Nilaxay
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Zuhal Rahmani
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Penelope J Saverton
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Omobolanle H Abdullateef
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Jordan Forward
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Anna E Jacob
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Safina Khadam
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Wlaa Ali
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Chloé Boer
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Hayato Kakinuma
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Joseph Hawkins
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Rosie Longstreeth
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Natalie M Portwood
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Madeleine Smee
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Natasha Brown
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Nursu C Kuyucu
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Susannah Lechmere
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Gabriela Stieger
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
| | - Santi Maithaviphet
- Center for Malariology, Parasitology and Entomology, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Simone Nambanya
- Center for Malariology, Parasitology and Entomology, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Paul T Brey
- Institut Pasteur du Laos, Department of Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Andrew K Jones
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK
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