1
|
Sa-Ngamuang C, Lawpoolsri S, Su Yin M, Barkowsky T, Cui L, Prachumsri J, Haddawy P. Assessment of malaria risk in Southeast Asia: a systematic review. Malar J 2023; 22:339. [PMID: 37940923 PMCID: PMC10631000 DOI: 10.1186/s12936-023-04772-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 10/26/2023] [Indexed: 11/10/2023] Open
Abstract
BACKGROUND Several countries in Southeast Asia are nearing malaria elimination, yet eradication remains elusive. This is largely due to the challenge of focusing elimination efforts, an area where risk prediction can play an essential supporting role. Despite its importance, there is no standard numerical method to quantify the risk of malaria infection. Thus, there is a need for a consolidated view of existing definitions of risk and factors considered in assessing risk to analyse the merits of risk prediction models. This systematic review examines studies of the risk of malaria in Southeast Asia with regard to their suitability in addressing the challenges of malaria elimination in low transmission areas. METHODS A search of four electronic databases over 2010-2020 retrieved 1297 articles, of which 25 met the inclusion and exclusion criteria. In each study, examined factors included the definition of the risk and indicators of malaria transmission used, the environmental and climatic factors associated with the risk, the statistical models used, the spatial and temporal granularity, and how the relationship between environment, climate, and risk is quantified. RESULTS This review found variation in the definition of risk used, as well as the environmental and climatic factors in the reviewed articles. GLM was widely adopted as the analysis technique relating environmental and climatic factors to malaria risk. Most of the studies were carried out in either a cross-sectional design or case-control studies, and most utilized the odds ratio to report the relationship between exposure to risk and malaria prevalence. CONCLUSIONS Adopting a standardized definition of malaria risk would help in comparing and sharing results, as would a clear description of the definition and method of collection of the environmental and climatic variables used. Further issues that need to be more fully addressed include detection of asymptomatic cases and considerations of human mobility. Many of the findings of this study are applicable to other low-transmission settings and could serve as a guideline for further studies of malaria in other regions.
Collapse
Affiliation(s)
- Chaitawat Sa-Ngamuang
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand
| | - Saranath Lawpoolsri
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Myat Su Yin
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand
| | - Thomas Barkowsky
- Bremen Spatial Cognition Center (BSCC), University of Bremen, Bremen, Germany
| | - Liwang Cui
- Division of Infectious Diseases and International Medicine, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, USA
| | - Jetsumon Prachumsri
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Peter Haddawy
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand.
- Bremen Spatial Cognition Center (BSCC), University of Bremen, Bremen, Germany.
| |
Collapse
|
2
|
Rakotonirina A, Maquart PO, Flamand C, Sokha C, Boyer S. Mosquito diversity (Diptera: Culicidae) and medical importance in four Cambodian forests. Parasit Vectors 2023; 16:110. [PMID: 36945055 PMCID: PMC10029166 DOI: 10.1186/s13071-023-05729-w] [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: 12/29/2022] [Accepted: 03/06/2023] [Indexed: 03/23/2023] Open
Abstract
BACKGROUND A total of 290 mosquito species are recorded in Cambodia among which 43 are known vectors of pathogens. As Cambodia is heavily affected by deforestation, a potential change in the dynamic of vector-borne diseases (VDBs) could occur through alteration of the diversity and density of sylvatic vector mosquitoes and induce an increase in their interactions with humans. Understanding mosquito diversity is therefore critical, providing valuable data for risk assessments concerning the (re)emergence of local VBDs. Consequently, this study mainly aimed to understand the spatial and temporal distribution of sylvatic mosquito populations of Cambodia by determining which factors impact on their relative abundance and presence. METHODS A study was conducted in 12 sites from four forests in Cambodia. All mosquitoes, collected during the dry and rainy seasons, were morphologically identified. The diversity and relative density of mosquito species in each site were calculated along with the influence of meteorological and geographical factors using a quasi-Poisson generalized linear model. RESULTS A total of 9392 mosquitoes were collected belonging to 13 genera and 85 species. The most represented genera were Culex, accounting for 46% of collected mosquitoes, and Aedes (42%). Besides being the most abundant species, Culex pseudovishnui and Aedes albopictus, which are known vectors of numerous arboviruses, were present in all sites during both dry and rainy seasons. The presence of mosquito species reported to be zoo-anthropophilic feeders was also observed in both forested and urban areas. Finally, this study demonstrated that altitude, temperature and precipitation impacted the abundance of mosquitoes but also influenced species community composition. CONCLUSION The results indicate an important diversity of mosquitoes in the four forests and an influence of meteorological and geographical factors on their community. Additionally, this work highlights in parallel the abundance of species considered to be of medical importance and therefore underlines the high risk of pathogen emergence/re-emergence in the region.
Collapse
Affiliation(s)
- Antsa Rakotonirina
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, 983, Phnom Penh, Cambodia.
| | - Pierre-Olivier Maquart
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, 983, Phnom Penh, Cambodia
| | - Claude Flamand
- Epidemiology Unit, Institut Pasteur du Cambodge, 983, Phnom Penh, Cambodia
- Mathematical Modeling of Infectious Diseases Unit, Institut Pasteur, Université Paris Cité, UMR2000, CNRS, Paris, France
| | - Chea Sokha
- Wildlife Health Program, Wildlife Conservation Society, Phnom Penh, Cambodia
| | - Sébastien Boyer
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, 983, Phnom Penh, Cambodia
- Ecology & Emergence of Arthropod-Borne Pathogens Unit, Department of Global Health, Institut Pasteur, CNRS UMR2000, Paris, France
| |
Collapse
|
3
|
Maquart PO, Chann L, Boyer S. Culex vishnui (Diptera: Culicidae): An Overlooked Vector of Arboviruses in South-East Asia. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1144-1153. [PMID: 35522221 DOI: 10.1093/jme/tjac044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Indexed: 06/14/2023]
Abstract
Culex vishnui Theobald, 1901, a main vector of Japanese encephalitis virus (JEV), is widely distributed in the Oriental region where it often accounts for a great part of the culicid fauna. This species also has been found naturally infected with at least 13 other arboviruses of medical and veterinary importance. Females blood feed predominantly upon pigs and birds, but may readily bite cattle and humans. Because of its abundance, medical importance, and presence throughout ecological gradients among urban, peri-urban, and rural areas, Cx. vishnui potentially may serve as a bridge vector transmitting viruses from natural and wild hosts to humans. Being zoo- and anthropophagic, omnipresent in the Oriental region, and presenting strong resistance to many insecticide families, this overlooked mosquito species may pose a serious health risk in one of the most densely populated regions of the world.
Collapse
Affiliation(s)
- Pierre-Olivier Maquart
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Leakena Chann
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Sebastien Boyer
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| |
Collapse
|
4
|
Traore I, Coulibaly ZI, Allali KB, Tangena JAA, Konan YL, Yapi A, Dosso M. Mosquito (Diptera: Culicidae) Larval Ecology in Rubber Plantations and Rural Villages in Dabou (Côte d'Ivoire). ECOHEALTH 2022; 19:259-272. [PMID: 35759112 DOI: 10.1007/s10393-022-01594-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 03/18/2022] [Indexed: 06/15/2023]
Abstract
In Côte d'Ivoire, rubber cultivation has more than doubled since 2010. These mass agricultural areas require a large workforce with little information on how this environment might impact risk of mosquito-borne diseases. The objective of this study was to assess the larval ecology of mosquitoes in rubber areas of Dabou, Côte d'Ivoire. From January to June 2017, an entomological survey was conducted of mature (MP) and immature (IP) rubber plantations, as well as in villages surrounded by rubber plantations (SV) and remote from rubber plantations (RV). The number and type of potential and positive breeding sites were recorded, and mosquito larval densities and diversity were estimated. Seven genera divided into 31 species including major vector such as Anopheles gambiae s.l. and Aedes aegypti were identified. A total of 1,660 waterbodies were identified with a larvae positivity rate of 63.1%. A majority of waterbodies were identified in SV (N = 875, 53.4% positivity rate), followed by MP (N = 422, 81.8% positivity rate), IP (N = 194, 72.2% positivity rate) and least in RV (N = 169, 57.4% positivity rate). The most important breeding sites for disease vectors were leaf axils in IP (N = 108, 77.1%), latex collection cups in MP (N = 332, 96.2%) and the containers abandoned in the SV (N = 242, 51.8%) as well as in the RV (N = 59, 60.8%). All these results allow us to affirm that the cultivation of rubber trees has an impact on the larval ecology by increasing the number of available sites and favoring a high larval density and diversity.
Collapse
Affiliation(s)
- Issouf Traore
- Entomology and Herpetology Unit, Institut Pasteur of Côte d'Ivoire, 01 BP490 Abidjan01, Abidjan, Côte d'Ivoire.
- Félix Houphouët-Boigny University, UFR Biosciences 22 BP 582 Abidjan 22, Abidjan, Côte d'Ivoire.
| | | | - Kouadio Bernard Allali
- Entomology and Herpetology Unit, Institut Pasteur of Côte d'Ivoire, 01 BP490 Abidjan01, Abidjan, Côte d'Ivoire
| | | | - Yao Lucien Konan
- Malaria Service, National Institute of Public Hygiene, BP.V 14 Abidjan, Abidjan, Côte d'Ivoire
| | - Ahoua Yapi
- Félix Houphouët-Boigny University, UFR Biosciences 22 BP 582 Abidjan 22, Abidjan, Côte d'Ivoire
| | - Mireille Dosso
- Entomology and Herpetology Unit, Institut Pasteur of Côte d'Ivoire, 01 BP490 Abidjan01, Abidjan, Côte d'Ivoire
| |
Collapse
|
5
|
Buxton M, Machekano H, Gotcha N, Nyamukondiwa C, Wasserman RJ. Are Vulnerable Communities Thoroughly Informed on Mosquito Bio-Ecology and Burden? INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17218196. [PMID: 33171954 PMCID: PMC7672552 DOI: 10.3390/ijerph17218196] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 09/24/2020] [Accepted: 09/25/2020] [Indexed: 11/25/2022]
Abstract
Mosquitoes account for a significant burden of morbidity and mortality globally. Despite evidence of (1) imminent anthropogenic climate and environmental changes, (2) vector-pathogen spatio-temporal dynamics and (3) emerging and re-emerging mosquito borne infections, public knowledge on mosquito bio-ecology remain scant. In particular, knowledge, attitude and practices (KAPs) on mosquitoes are often neglected despite otherwise expensive remedial efforts against consequent infections and other indirect effects associated with disease burden. To gather baseline KAPs that identify gaps for optimising vector-borne disease control, we surveyed communities across endemic and non-endemic malaria sub-districts (Botswana). The study revealed limited knowledge of mosquitoes and their infections uniformly across endemic and non-endemic areas. In addition, a significant proportion of respondents were concerned about mosquito burdens, although their level of personal, indoor and environmental protection practices varied significantly across sub-districts. Given the limited knowledge displayed by the communities, this study facilitates bridging KAP gaps to minimise disease burdens by strengthening public education. Furthermore, it provides a baseline for future studies in mosquito bio-ecology and desirable control practices across differential spheres of the rural–urban lifestyle, with implications for enhanced livelihoods as a consequence of improved public health.
Collapse
|
6
|
Fontenille D, Powell JR. From Anonymous to Public Enemy: How Does a Mosquito Become a Feared Arbovirus Vector? Pathogens 2020; 9:E265. [PMID: 32260491 PMCID: PMC7238163 DOI: 10.3390/pathogens9040265] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/01/2020] [Accepted: 04/02/2020] [Indexed: 01/17/2023] Open
Abstract
The past few decades have seen the emergence of several worldwide arbovirus epidemics (chikungunya, Zika), the expansion or recrudescence of historical arboviruses (dengue, yellow fever), and the modification of the distribution area of major vector mosquitoes such as Aedes aegypti and Ae. albopictus, raising questions about the risk of appearance of new vectors and new epidemics. In this opinion piece, we review the factors that led to the emergence of yellow fever in the Americas, define the conditions for a mosquito to become a vector, analyse the recent example of the new status of Aedes albopictus from neglected mosquito to major vector, and propose some scenarios for the future.
Collapse
Affiliation(s)
- Didier Fontenille
- MIVEGEC unit, Université de Montpellier, Institut de Recherche pour le Développement (IRD), CNRS, BP 64501, 34394 Montpellier, France
| | - Jeffrey R. Powell
- Department of Ecology and Evolutionary Biology, Yale University, 21 Sachem Street, New Haven, CT 06511-8934, USA;
| |
Collapse
|
7
|
Motoki MT, Fonseca DM, Miot EF, Demari-Silva B, Thammavong P, Chonephetsarath S, Phommavanh N, Hertz JC, Kittayapong P, Brey PT, Marcombe S. Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People's Democratic Republic. Parasit Vectors 2019; 12:477. [PMID: 31610813 PMCID: PMC6792217 DOI: 10.1186/s13071-019-3740-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 10/04/2019] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. METHODS We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. RESULTS We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. CONCLUSIONS Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.
Collapse
Affiliation(s)
- Maysa Tiemi Motoki
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic. .,Vysnova Partners Inc., Landover, MD, USA. .,Walter Reed Biosystematics Unit, Smithsonian Institution, Museum Support Center, MRC-534, Suitland, MD, 20746, USA.
| | - Dina Madera Fonseca
- Center for Vector Biology and Department of Entomology, Rutgers University, New Brunswick, NJ, USA
| | - Elliott Frederic Miot
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic.,Université Pierre et Marie Curie, Cellule Pasteur UPMC, Paris, France.,Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, Paris, France.,Centre National de la Recherche Scientifique, Unité Mixte de Recherche 2000, Paris, France
| | - Bruna Demari-Silva
- Department of Epidemiology, Faculty of Public Health, University of Sao Paulo, Sao Paulo, Brazil
| | - Phoutmany Thammavong
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic
| | - Somsanith Chonephetsarath
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic
| | - Nothasine Phommavanh
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic
| | | | | | - Paul Trevor Brey
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic
| | - Sebastien Marcombe
- Medical Entomology and Vector Borne Disease Unit, Institut Pasteur du Laos, Vientiane, Lao People's Democratic Republic
| |
Collapse
|
8
|
Abstract
For the control and elimination of malaria, information on the local vector dynamics is essential. This information provides guidance on appropriate and timely deployment of vector control tools and their subsequent success. The data on the dynamics of local mosquito populations can be collected using many different Anopheles sampling methods. Dependent on the objectives, resources, time, and local environment, different traps and methods can be chosen. This chapter describes the sampling of adult populations, focusing on the important preparatory stages and some of the widely used sampling methods. The trapping methods discussed in this chapter are the human landing catch, human-baited net trap, animal landing catch, animal-baited net trap, CDC miniature light trap, Biogents Suna trap, peripheral net collection, pyrethrum collection, exit/entry trap, and resting shelter. For optimal deployment in the field, a step-by-step description of the sampling methods is given.
Collapse
|
9
|
Motoki MT, Vongphayloth K, Rueda LM, Miot EF, Hiscox A, Hertz JC, Brey PT. New records and updated checklist of mosquitoes (Diptera: Culicidae) from Lao People's Democratic Republic, with special emphasis on adult and larval surveillance in Khammuane Province. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2019; 44:76-88. [PMID: 31124228 DOI: 10.1111/jvec.12331] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 02/14/2019] [Indexed: 06/09/2023]
Abstract
A list of mosquitoes from the Nakai Nam Theun National Protected Area along the Nam Theun, Nam Mon, Nam Noy, and Nam On rivers, Nakai District, Khammuane Province, Lao People's Democratic Republic (Lao PDR) is presented. Fifty-four mosquito taxa were identified, including 15 new records in the Lao PDR. A fragment of the mtDNA cytochrome c oxidase subunit I (COI) gene, barcode region, was generated for 34 specimens, and together with four specimens already published, it represented 23 species in eight genera. In addition, an updated checklist of 170 mosquito taxa from Lao PDR is provided based on field collections from Khammuane Province, the literature, and specimens deposited in the Smithsonian Institution, National Museum of Natural History (SI-NMNH), Washington, DC, U.S.A. This paper provides additional information about the biodiversity of mosquito fauna in Lao PDR.
Collapse
Affiliation(s)
- Maysa T Motoki
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Samsenthai Rd., Ban Kao-gnot, P.O. Box 3560, Vientiane, Lao PDR
- Walter Reed Biosystematics Unit, Entomology Department, Smithsonian Institution, MSC MRC 514, Suitland, MD, U.S.A
| | - Khamsing Vongphayloth
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Samsenthai Rd., Ban Kao-gnot, P.O. Box 3560, Vientiane, Lao PDR
| | - Leopoldo M Rueda
- Walter Reed Biosystematics Unit, Entomology Department, Smithsonian Institution, MSC MRC 514, Suitland, MD, U.S.A
| | - Elliott F Miot
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Samsenthai Rd., Ban Kao-gnot, P.O. Box 3560, Vientiane, Lao PDR
- Université Pierre et Marie Curie, Cellule Pasteur UPMC, Paris, France
- Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, Paris, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 2000, Paris, France
| | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | | | - Paul T Brey
- Medical Entomology and Vector-Borne Disease Unit, Institut Pasteur du Laos, Samsenthai Rd., Ban Kao-gnot, P.O. Box 3560, Vientiane, Lao PDR
| |
Collapse
|
10
|
Tangena JAA, Thammavong P, Chonephetsarath S, Logan JG, Brey PT, Lindsay SW. Field evaluation of personal protection methods against outdoor-biting mosquitoes in Lao PDR. Parasit Vectors 2018; 11:661. [PMID: 30558671 PMCID: PMC6296151 DOI: 10.1186/s13071-018-3239-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 11/28/2018] [Indexed: 11/10/2022] Open
Abstract
Background Protecting people outdoors against mosquito-borne diseases is a major challenge. Here we compared commercially available personal protection methods to identify the most effective method for outdoor use in northern Lao PDR. Methods From June to August 2016 the protective efficacy of treatments were compared in a secondary forest during the afternoon and a village during the evening. Comparisons were made using a replicated Latin square design between: (i) short permethrin-treated overalls; (ii) long permethrin-treated overalls; (iii) short untreated overalls with para-menthane-3,8-diol (PMD) applied topically; (iv) short permethrin-treated overalls plus PMD applied topically; (v) short untreated overalls with metofluthrin coils in a metal casing worn on a belt; and (vi) long untreated overalls. Short untreated overalls served as the control. Cone tests were conducted on the treated and untreated fabric before and after field experiments. A questionnaire survey was used to measure social acceptability. Results Mosquito coils in a metal casing worn on a belt resulted in 92.3% (95% confidence interval, CI: 88.9–94.6%). landing protection from female mosquitoes in the afternoon and 68.8% (95% CI: 41.7–83.3%) protection in the evening compared to short untreated clothing. PMD was protective both when combined with short permethrin-treated overalls (afternoon, 68.2%, 95% CI: 52.6–78.7%; evening, 52.3%, 95% CI: 33.8–65.7%) and when used in combination with short untreated overalls (afternoon, 55.0%, 95% CI: 41.7–65.2%; evening, 25.2%, 95% CI: 9.4–38.2%). Whilst long permethrin-treated overalls were protective (afternoon, 61.1%, 95% CI: 51.4–68.8%; evening, 43.0%, 95% CI: 25.5–56.4%), short permethrin-treated overalls and long untreated overalls were not. Exposure to new permethrin-treated fabric in cone tests resulted in 25.0% (95% CI, 17.8–32.2%) and 26.2% (95% CI 16.7–35.8%) mortality for susceptible Ae. albopictus and susceptible Ae. aegypti, respectively. There was a loss of efficacy of permethrin-treated clothing after use in the field, with 3 min knockdown rates of Ae. albopictus and 1 h knockdown of Ae. aegypti decreasing over time. Participants considered all treatments acceptable. Conclusions The portable mosquito coils were highly protective against outdoor biting mosquitoes, although there are safety concerns related to its use. The combination of permethrin-treated clothing and PMD repellent represent an alternative treatment for protection against outdoor-biting mosquitoes. Electronic supplementary material The online version of this article (10.1186/s13071-018-3239-0) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Julie-Anne A Tangena
- Medical Entomology & Biology of Disease Vectors Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR.
| | - Phoutmany Thammavong
- Medical Entomology & Biology of Disease Vectors Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Somsanith Chonephetsarath
- Medical Entomology & Biology of Disease Vectors Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - James G Logan
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK.,ARCTEC, London School of Hygiene and Tropical Medicine, London, UK
| | - Paul T Brey
- Medical Entomology & Biology of Disease Vectors Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Steve W Lindsay
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK.,Department of Biosciences, Durham University, Durham, UK
| |
Collapse
|
11
|
Tangena JAA, Marcombe S, Thammavong P, Chonephetsarath S, Somphong B, Sayteng K, Grandadam M, Sutherland IW, Lindsay SW, Brey PT. Bionomics and insecticide resistance of the arboviral vector Aedes albopictus in northern Lao PDR. PLoS One 2018; 13:e0206387. [PMID: 30359425 PMCID: PMC6201963 DOI: 10.1371/journal.pone.0206387] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 10/11/2018] [Indexed: 12/21/2022] Open
Abstract
In the last four decades there has been a staggering increase in the geographical range of the arboviral vector Aedes albopictus (Skuse, 1894). This species is now found in every continent except Antarctica, increasing the distribution of arboviral diseases such as dengue and chikungunya. In Lao PDR dengue epidemics occur regularly, with cases of chikungunya also reported. As treatment methods for arboviral diseases is limited, the control of the vector mosquitoes are essential. There is a paucity of information on the bionomics and resistance status of this mosquito for successful vector control efforts. Here we describe the bionomics and insecticide resistance status of Ae. albopictus in Laos to identify opportunities for control. Adult Ae. albopictus were collected using human-baited double bed net (HDN) traps in forests, villages and rubber plantations and tested for alpha- and flaviviruses with RT-PCR. Surveys were also conducted to identify larval habitats. Seven adult and larval populations originating from Vientiane Capital and Luang Prabang province were tested against DDT, malathion, permethrin, deltamethrin and, temephos following WHO protocols. Aedes albopictus were found throughout the year, but were six-fold greater in the rainy season than the dry season. Adult females were active for 24 hours, with peak of behaviour at 18.00 h. The secondary forest and rubber plantation samples showed evidence of Pan-flaviviruses, while samples from the villages did not. More than half of the emerged Ae. albopictus were collected from mature rubber plantations (53.9%; 1,533/2,845). Most Ae. albopictus mosquitoes emerged from latex collection cups (19.7%; 562/2,845), small water containers (19.7%; 562/2,845) and tyres (17.4%; 495/2,845). Adult mosquitoes were susceptible to pyrethroids, apart from one population in Vientiane city. All populations were resistant to DDT (between 27-90% mortality) and all except one were resistant to malathion (20-86%). Three of the seven larval populations were resistant to temephos (42-87%), with suspected resistance found in three other populations (92-98%).This study demonstrates that rural areas in northern Laos are potential hot spots for arboviral disease transmission. Multiple-insecticide resistance was found. Aedes albopictus control efforts in villages need to expand to include secondary forests and rubber plantations, with larval source management and limited use of insecticides.
Collapse
Affiliation(s)
- Julie-Anne A. Tangena
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| | - Sébastien Marcombe
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| | - Phoutmany Thammavong
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| | | | - Boudsady Somphong
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| | - Kouxiong Sayteng
- Arbovirology and Emerging Viruses Laboratory, Institut Pasteur du Laos, Vientiane, Laos
| | - Marc Grandadam
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| | - Ian W. Sutherland
- United States Naval Medical Research Center—Asia, PSA SEMBAWANG, Singapore
- United States Navy Entomology Center of Excellence, NAS Jacksonville, Florida, United States of America
| | - Steve W. Lindsay
- Department of Biosciences, Durham University, Durham, United Kingdom
| | - Paul T. Brey
- Medical Entomology and Vector-Borne Disease Laboratory Institut Pasteur du Laos, Vientiane, Laos
| |
Collapse
|
12
|
Lover AA, Dantzer E, Hongvanthong B, Chindavongsa K, Welty S, Reza T, Khim N, Menard D, Bennett A. Prevalence and risk factors for asymptomatic malaria and genotyping of glucose 6-phosphate (G6PD) deficiencies in a vivax-predominant setting, Lao PDR: implications for sub-national elimination goals. Malar J 2018; 17:218. [PMID: 29859089 PMCID: PMC5984820 DOI: 10.1186/s12936-018-2367-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 05/23/2018] [Indexed: 12/27/2022] Open
Abstract
Background Lao People Democratic Republic (PDR; Laos), a landlocked country in Southeast Asia, has made important progress in reducing malaria morbidity and mortality in the past 5–6 years, and the northern provinces have very low reported incidence. To support national progress towards elimination, it is critical to verify and understand these changes in disease burden. Methods A two-stage cluster cross-sectional survey was conducted in four districts within four northern provinces (Khua, Phongsaly Province; Paktha, Bokeo Province; Nambak, Luang Prabang, and Muang Et, Huaphanh Province). During September and October 2016, demographics and malaria risk factors were collected from a total of 1492 households. A total of 5085 persons consented to collection of blood samples for testing, by rapid diagnostic test (RDT) and polymerase chain reaction (PCR)-based testing. Risk factors for infection were examined using logistic regression; and a randomized subset of males was tested for glucose-6-phosphate dehydrogenase (G6PD) deficiencies using a combined PCR and sequencing approach. Results There were zero positives by RDT, and PCR detected Plasmodium infections in 39 (0.77%; 95% CI 0.40–1.47%) of 5082 analysable samples. The species distribution was Plasmodium vivax (28 total); Plasmodium falciparum/P. vivax (5); P. falciparum (3), Plasmodium malariae (2), and P. vivax/P. malariae (1). In multivariable analysis, the main risk factors included having any other cases within the household [aOR 12.83 (95% CI 4.40 to 37.38), p < 0.001]; and lack of bed net ownership within the household [aOR 10.91 (95% 5.42–21.94), p < 0.001]; age, sex and forest-travel were not associated with parasitaemia. A total of 910 males were tested for the six most common G6PDd in SE Asia; and 30 (3.3%; 95% CI 2.1–5.1%) had a G6PD variant allele associated with G6PD deficiency, with the majority being the Union (14) and Viangchan (11) polymorphisms, with smaller numbers of Canton and Mahidol. Conclusion This is the first rigorous PCR-based population survey for malaria infection in Northern Lao PDR, and found a very low prevalence of asymptomatic Plasmodium infections by standard PCR methods, with P. vivax predominating in the surveyed districts. Clustering of cases within households, and lack of a bed nets suggest reactive case detection, and scale-up of coverage should be prioritized. The predominance of infections with P. vivax, combined with moderate levels of serious G6PD deficiencies highlight the need for careful rollout of primaquine towards elimination goals. Electronic supplementary material The online version of this article (10.1186/s12936-018-2367-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Andrew A Lover
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA.
| | - Emily Dantzer
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | - Bouasy Hongvanthong
- Center for Malariology, Parasitology and Entomology (CMPE), Ministry of Health, Vientiane, Lao PDR
| | | | - Susie Welty
- Global Strategic Information, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | - Tania Reza
- Global Strategic Information, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | | | - Didier Menard
- Malaria Genetic and Resistance Group, Institut Pasteur, Paris, France
| | - Adam Bennett
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| |
Collapse
|
13
|
Tangena JAA, Thammavong P, Lindsay SW, Brey PT. Risk of exposure to potential vector mosquitoes for rural workers in Northern Lao PDR. PLoS Negl Trop Dis 2017; 11:e0005802. [PMID: 28742854 PMCID: PMC5544251 DOI: 10.1371/journal.pntd.0005802] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 08/04/2017] [Accepted: 07/12/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND One major consequence of economic development in South-East Asia has been a rapid expansion of rubber plantations, in which outbreaks of dengue and malaria have occurred. Here we explored the difference in risk of exposure to potential dengue, Japanese encephalitis (JE), and malaria vectors between rubber workers and those engaged in traditional forest activities in northern Laos PDR. METHODOLOGY/PRINCIPAL FINDINGS Adult mosquitoes were collected for nine months in secondary forests, mature and immature rubber plantations, and villages. Human behavior data were collected using rapid participatory rural appraisals and surveys. Exposure risk was assessed by combining vector and human behavior and calculating the basic reproduction number (R0) in different typologies. Compared to those that stayed in the village, the risk of dengue vector exposure was higher for those that visited the secondary forests during the day (odds ratio (OR) 36.0), for those living and working in rubber plantations (OR 16.2) and for those that tapped rubber (OR 3.2). Exposure to JE vectors was also higher in the forest (OR 1.4) and, similar when working (OR 1.0) and living in the plantations (OR 0.8). Exposure to malaria vectors was greater in the forest (OR 1.3), similar when working in the plantations (OR 0.9) and lower when living in the plantations (OR 0.6). R0 for dengue was >2.8 for all habitats surveyed, except villages where R0≤0.06. The main malaria vector in all habitats was Anopheles maculatus s.l. in the rainy season and An. minimus s.l. in the dry season. CONCLUSIONS/SIGNIFICANCE The highest risk of exposure to vector mosquitoes occurred when people visit natural forests. However, since rubber workers spend long periods in the rubber plantations, their risk of exposure is increased greatly compared to those who temporarily enter natural forests or remain in the village. This study highlights the necessity of broadening mosquito control to include rubber plantations.
Collapse
Affiliation(s)
- Julie-Anne A. Tangena
- Department of Medical Entomology & Biology of Disease Vectors, Institut Pasteur du Laos, Vientiane, Lao PDR
- School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom
- * E-mail:
| | - Phoutmany Thammavong
- Department of Medical Entomology & Biology of Disease Vectors, Institut Pasteur du Laos, Vientiane, Lao PDR
| | - Steve W. Lindsay
- School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom
| | - Paul T. Brey
- Department of Medical Entomology & Biology of Disease Vectors, Institut Pasteur du Laos, Vientiane, Lao PDR
| |
Collapse
|