Bionomics of malaria vectors in Lao PDR, 2018-2020: entomological surveillance as a key tool for malaria elimination.
Anopheles
Bionomics
Entomology surveillance
Laos
Malaria
Vector
Journal
Malaria journal
ISSN: 1475-2875
Titre abrégé: Malar J
Pays: England
ID NLM: 101139802
Informations de publication
Date de publication:
21 Oct 2023
21 Oct 2023
Historique:
received:
30
05
2023
accepted:
13
10
2023
medline:
2
11
2023
pubmed:
22
10
2023
entrez:
21
10
2023
Statut:
epublish
Résumé
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. 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. 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. 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.
Sections du résumé
BACKGROUND
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
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
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
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.
Identifiants
pubmed: 37865735
doi: 10.1186/s12936-023-04754-5
pii: 10.1186/s12936-023-04754-5
pmc: PMC10589990
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
319Subventions
Organisme : World Health Organization
ID : 001
Pays : International
Informations de copyright
© 2023. BioMed Central Ltd., part of Springer Nature.
Références
Kounnavong S, Gopinath D, Hongvanthong B, Khamkong C, Sichanthongthip O. Malaria elimination in Lao PDR: the challenges associated with population mobility. Infect Dis Poverty. 2017;6:81.
doi: 10.1186/s40249-017-0283-5
pubmed: 28438218
pmcid: 5404311
WHO. World malaria report 2021. Geneva: World Health Organization; 2021.
Ministry of Health. National Strategic Plan for Malaria Control and Elimination 2016–2020. Vientiane, 2016.
Killeen GF. Characterizing, controlling and eliminating residual malaria transmission. Malar J. 2014;13:330.
doi: 10.1186/1475-2875-13-330
pubmed: 25149656
pmcid: 4159526
Marcombe S, Maithaviphet S, Bobichon J, Phommavan N, Nambanya S, Corbel V, et al. New insights into malaria vector bionomics in Lao PDR: a nationwide entomology survey. Malar J. 2020;19:396.
doi: 10.1186/s12936-020-03453-9
pubmed: 33168012
pmcid: 7654023
Savada AM, Whitaker DP. Laos: a country study. 3rd ed. Washington: Federal Research Division, Library of Congress; 1995.
Rattanarithikul R, Harrison BA, Harbach RE, Panthusiri P, Coleman R. Illustrated keys to the mosquitoes of Thailand IV. Anopheles. Southeast Asian J Trop Med Public Health. 2006;37(Suppl 2):1–128.
pubmed: 17262930
World bank data. https://data.worldbank.org/indicator/SP.POP.GROW?locations=LA . Accessed 20 Oct 2023.
Meek SR. Vector control in some countries of Southeast Asia: comparing the vectors and the strategies. Ann Trop Med Parasitol. 1995;89:135–47.
doi: 10.1080/00034983.1995.11812944
pubmed: 7605123
Kobayashi J, Nambanya S, Miyagi I, Vanachone B, Manivong K, Koubouchan T, et al. Collection of anopheline mosquitos in three villages endemic for malaria in Khammouane, Lao PDR. Southeast Asian J Trop Med Public Health. 1997;28:20.
pubmed: 9561618
Toma T, Miyagi I, Okazawa T, Kobayashi J, Saita S, Tuzuki A, et al. Entomological surveys on malaria in Khammouane Province, Lao PDR, in 1999 and 2000. Southeast Asian J Trop Med Public Health. 2002;33:532–46.
pubmed: 12693588
Vythilingam I, Phetsouvanh R, Keokenchanh K, Yengmala V, Vanisaveth V, Phompida S, et al. The prevalence of Anopheles (Diptera: Culicidae) mosquitoes in Sekong Province, Lao PDR in relation to malaria transmission. Trop Med Int Health. 2003;8:525–35.
doi: 10.1046/j.1365-3156.2003.01052.x
pubmed: 12791058
Motoki MT, Vongphayloth K, Rueda LM, Miot EF, Hiscox A, Hertz JC, et al. 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. J Vector Ecol. 2019;44:76–88.
doi: 10.1111/jvec.12331
pubmed: 31124228
Kobayashi J, Somboon P, Keomanila H, Inthavongsa S, Nambanya S, Inthakone S, et al. Malaria prevalence and a brief entomological survey in a village surrounded by rice fields in Khammouan province, Lao PDR. Trop Med Int Health. 2000;5:17–21.
doi: 10.1046/j.1365-3156.2000.00516.x
pubmed: 10672201
Harbach RE, Gingrich JB, Pang LW. Some entomological observations on malaria transmission in a remote village in northwestern Thailand. J Am Mosq Control Assoc. 1987;3:296–301.
pubmed: 3333058
Vantaux A, Riehle MM, Piv E, Farley EJ, Chy S, Kim S, et al. Anopheles ecology, genetics and malaria transmission in northern Cambodia. Sci Rep. 2021;11:6458.
doi: 10.1038/s41598-021-85628-1
pubmed: 33742030
pmcid: 7979810
Trung HD, Bortel WV, Sochantha T, Keokenchanh K, Briët OJT, Coosemans M. Behavioural heterogeneity of Anopheles species in ecologically different localities in Southeast Asia: a challenge for vector control. Trop Med Int Health. 2005;10:251–62.
doi: 10.1111/j.1365-3156.2004.01378.x
pubmed: 15730510
Suwonkerd W, Ritthison W, Ngo CT, Tainchum K, Bangs MJ, Chareonviriyaphap T. Vector biology and malaria transmission in Southeast Asia. In: Manguin S, editor. Anopheles mosquitoes-new insights into malaria vectors. London: IntechOpen; 2013.
Nguyen TQ, Nguyen MD, Pham VX, Ro HM, Edstein MD, Chow WK, et al. Entomological survey in two communes with residual malaria transmission in Gia Lai Province in the central highlands of Vietnam. Malar J. 2021;20:403.
doi: 10.1186/s12936-021-03941-6
pubmed: 34656112
pmcid: 8520203
Marcombe S, Bobichon J, Somphong B, Phommavan N, Maithaviphet S, Nambanya S, et al. Insecticide resistance status of malaria vectors in Lao PDR. PLoS ONE. 2017;12:e0175984.
doi: 10.1371/journal.pone.0175984
pubmed: 28437449
pmcid: 5402946
Martin JA, Hendershot AL, Saá Portilla IA, English DJ, Woodruff M, Vera-Arias CA, et al. Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study. Malar J. 2020;19:354.
doi: 10.1186/s12936-020-03426-y
pubmed: 33008438
pmcid: 7532652
Chaccour C, Killeen GF. Mind the gap: residual malaria transmission, veterinary endectocides and livestock as targets for malaria vector control. Malar J. 2016;15:24.
doi: 10.1186/s12936-015-1063-y
pubmed: 26755345
pmcid: 4709969
Maia MF, Abonuusum A, Lorenz LM, Clausen PH, Bauer B, Garms R, et al. The effect of deltamethrin-treated net fencing around cattle enclosures on outdoor-biting mosquitoes in Kumasi, Ghana. PLoS ONE. 2012;7:e45794.
doi: 10.1371/journal.pone.0045794
pubmed: 23029245
pmcid: 3446911
Khemrattrakool P, Yanola J, Lumjuan N, Somboon P. Pyriproxyfen-treated polypropylene sheets and resting boxes for controlling mosquitoes in livestock operations. Insects. 2019;10:55.
doi: 10.3390/insects10020055
pubmed: 30781681
pmcid: 6410238