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Sambe BS, Sarr I, Diagne A, Diatta AS, Faye J, Diagne N, Diaw SOM, Mbodj AF, Sané R, Wotodjo AN, Diouf B, Thiam A, Diamanka A, Faye N, Sembène PM, Sarr FD, Dia I, Vigan-Womas I, Sokhna C, Toure-Balde A, Niang M. Persistent carriage of subpatent Plasmodium falciparum parasites associated with clinical malaria in a low transmission area in Senegal. Int J Infect Dis 2024; 147:107211. [PMID: 39151787 DOI: 10.1016/j.ijid.2024.107211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 08/05/2024] [Accepted: 08/11/2024] [Indexed: 08/19/2024] Open
Abstract
OBJECTIVES In low malaria transmission areas, the elimination of the disease has been hampered partly by the existence of a reservoir of subpatent Plasmodium falciparum infections within communities. This reservoir, often undetected, serves as a source of parasites and contributes to ongoing transmission and clinical malaria cases. METHODS This study, spanning a period of 9 years from June 2014 to December 2022, examined individual variations and long-term subpatent P. falciparum carriage in two matched cohorts of 44 individuals each living in Dielmo village in the Sudanian area of Senegal. Biannual blood samples, collected in June/July and December of each year, underwent P. falciparum diagnosis by quantitative polymerase chain reaction. QGIS and R analytical tools were used to map infections, assess the occurrence and clustering of subpatent and clinical P. falciparum infections, and determine the risk of infection in the vicinity of asymptomatic P. falciparum carriers. RESULTS The point frequency and long-term P. falciparum carriage were significantly higher among the quantitative polymerase chain reaction (qPCR) positive cohort compared to the negative cohort across the 16 cross-sectional surveys analyzed in this study (19.76% vs 10.99%, P-value <0.001). Asymptomatic carriage events in qPCR-positive group were 18.86 ± 1.72% and significantly greater (P-value = 0.001) than in the qPCR-negative group (11.32 ± 1.32%). The relative risk of P. falciparum infection or clinical malaria calculated with a 95% confidence interval significantly increased in the vicinity of infected individuals and was 1.44 (P-value = 0.53) and 2.64 (P-value = 0.04) when at least one individual in the direct (household) or indirect (block of households) vicinity is infected, respectively. The risk increased to 3.64 (P-value <0.001) if at least 1/5 of individuals in the indirect vicinity were P. falciparum-infected. CONCLUSIONS The study provides a detailed qualitative and quantitative analysis of the asymptomatic P. falciparum reservoir and its temporal and spatial dynamics within two subgroups of P. falciparum-infected and non-infected individuals in Dielmo village. It identified high-risk populations known as "hotpops" and hotspots that could be targeted by innovative interventions to accelerate the elimination of malaria in Dielmo village.
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Affiliation(s)
- Babacar Souleymane Sambe
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Ibrahima Sarr
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal; Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | - Aissatou Diagne
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal; Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | - Arona Sabène Diatta
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Joseph Faye
- Institut Pasteur de Dakar, Pôle Epidémiologie, Recherche Clinique et Science des données, Dakar, Senegal
| | | | - Serigne Ousmane Mbacké Diaw
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Adja Fatou Mbodj
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Rokhaya Sané
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal; Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | | | - Babacar Diouf
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Alassane Thiam
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Arfang Diamanka
- Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | - Ngor Faye
- Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | - Papa Mbacké Sembène
- Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar Fann, Senegal
| | - Fatoumata Diene Sarr
- Institut Pasteur de Dakar, Pôle Epidémiologie, Recherche Clinique et Science des données, Dakar, Senegal
| | - Ibrahima Dia
- Institut Pasteur de Dakar, Pôle Zoologie Médicale, Dakar, Senegal
| | - Inès Vigan-Womas
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Cheikh Sokhna
- EMR - MINES, Campus International IRD-UCAD de Hann, Dakar, Senegal
| | - Aissatou Toure-Balde
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal
| | - Makhtar Niang
- Institut Pasteur de Dakar, Pôle Immunophysiopathologie et Maladies Infectieuses, 36 avenue Pasteur, Dakar, Senegal.
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Gueye A, Ngom EHM, Diagne A, Ndoye BB, Dione ML, Sambe BS, Sokhna C, Diallo M, Niang M, Dia I. Host feeding preferences of malaria vectors in an area of low malaria transmission. Sci Rep 2023; 13:16410. [PMID: 37775717 PMCID: PMC10542387 DOI: 10.1038/s41598-023-43761-z] [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: 06/28/2023] [Accepted: 09/28/2023] [Indexed: 10/01/2023] Open
Abstract
Studying the behaviour and trophic preferences of mosquitoes is an important step in understanding the exposure of vertebrate hosts to vector-borne diseases. In the case of human malaria, transmission increases when mosquitoes feed more on humans than on other animals. Therefore, understanding the spatio-temporal dynamics of vectors and their feeding preferences is essential for improving vector control measures. In this study, we investigated the feeding behaviour of Anopheles mosquitoes at two sites in the Sudanian areas of Senegal where transmission is low following the implementation of vector control measures. Blood-fed mosquitoes were collected monthly from July to November 2022 by pyrethrum spray catches in sleeping rooms of almost all houses in Dielmo and Ndiop villages, and blood meals were identified as from human, bovine, ovine, equine and chicken by ELISA. Species from the An. gambiae complex were identified by PCR. The types and numbers of potential domestic animal hosts were recorded in each village. The Human Blood Index (HBI) and the Manly Selection Ratio (MSR) were calculated to determine whether hosts were selected in proportion to their abundance. Spatio-temporal variation in HBI was examined using the Moran's index. A total of 1251 endophilic Anopheles females were collected in 115 bedrooms, including 864 blood fed females of 6 species. An. arabiensis and An. funestus were predominant in Dielmo and Ndiop, respectively. Of the 864 blood meals tested, 853 gave a single host positive result mainly on bovine, equine, human, ovine and chicken in decreasing order in both villages. Overall, these hosts were not selected in proportion to their abundance. The human host was under-selected, highlighting a marked zoophily for the vectors. Over time and space, the HBI were low with no obvious trend, with higher and lower values observed in each of the five months at different points in each village. These results highlight the zoophilic and exophagic behaviour of malaria vectors. This behaviour is likely to be a consequence of the distribution and use of LLINs in both villages and may increase risk of residual outdoor transmission. This underlines the need to study the feeding host profile of outdoor resting populations and how domestic animals may influence malaria epidemiology in order to tailor effective malaria vector control strategies in the two villages.
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Affiliation(s)
- Assiyatou Gueye
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - El Hadji Malick Ngom
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Aissatou Diagne
- Pole Immunophysiopathologie et Maladies Infectieuses, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Baye Bado Ndoye
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Mamadou Lamine Dione
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Babacar Souleymane Sambe
- Pole Immunophysiopathologie et Maladies Infectieuses, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Cheikh Sokhna
- UMR Vecteurs Infections Tropicales et Mediterraneennes (VITROME), Campus International UCAD-IRD, Route des Peres Maristes, BP 1386, Dakar, Senegal
| | - Mawlouth Diallo
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Makhtar Niang
- Pole Immunophysiopathologie et Maladies Infectieuses, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal
| | - Ibrahima Dia
- Pole de Zoologie Medicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal.
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Sandfort M, Monteiro W, Lacerda M, Nguitragool W, Sattabongkot J, Waltmann A, Salje H, Vantaux A, Witkowski B, Robinson LJ, Mueller I, White M. The spatial signature of Plasmodium vivax and Plasmodium falciparum infections: quantifying the clustering of infections in cross-sectional surveys and cohort studies. Malar J 2023; 22:75. [PMID: 36870976 PMCID: PMC9985228 DOI: 10.1186/s12936-023-04515-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
BACKGROUND Over the last decades, enormous successes have been achieved in reducing malaria burden globally. In Latin America, South East Asia, and the Western Pacific, many countries now pursue the goal of malaria elimination by 2030. It is widely acknowledged that Plasmodium spp. infections cluster spatially so that interventions need to be spatially informed, e.g. spatially targeted reactive case detection strategies. Here, the spatial signature method is introduced as a tool to quantify the distance around an index infection within which other infections significantly cluster. METHODS Data were considered from cross-sectional surveys from Brazil, Thailand, Cambodia, and Solomon Islands, conducted between 2012 and 2018. Household locations were recorded by GPS and finger-prick blood samples from participants were tested for Plasmodium infection by PCR. Cohort studies from Brazil and Thailand with monthly sampling over a year from 2013 until 2014 were also included. The prevalence of PCR-confirmed infections was calculated at increasing distance around index infections (and growing time intervals in the cohort studies). Statistical significance was defined as prevalence outside of a 95%-quantile interval of a bootstrap null distribution after random re-allocation of locations of infections. RESULTS Prevalence of Plasmodium vivax and Plasmodium falciparum infections was elevated in close proximity around index infections and decreased with distance in most study sites, e.g. from 21.3% at 0 km to the global study prevalence of 6.4% for P. vivax in the Cambodian survey. In the cohort studies, the clustering decreased with longer time windows. The distance from index infections to a 50% reduction of prevalence ranged from 25 m to 3175 m, tending to shorter distances at lower global study prevalence. CONCLUSIONS The spatial signatures of P. vivax and P. falciparum infections demonstrate spatial clustering across a diverse set of study sites, quantifying the distance within which the clustering occurs. The method offers a novel tool in malaria epidemiology, potentially informing reactive intervention strategies regarding radius choices of operations around detected infections and thus strengthening malaria elimination endeavours.
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Affiliation(s)
- Mirco Sandfort
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France.
- Sorbonne Université, Collège Doctoral, Paris, France.
| | - Wuelton Monteiro
- Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil
- Universidade do Estado do Amazonas, Manaus, Brazil
| | - Marcus Lacerda
- Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil
- Universidade do Estado do Amazonas, Manaus, Brazil
- Instituto de Pesquisas Leônidas e Maria Deane, Manaus, Brazil
| | - Wang Nguitragool
- Department of Molecular Tropical Medicine & Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Andreea Waltmann
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Henrik Salje
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Leanne J Robinson
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
- Burnet Institute, Melbourne, Australia
| | - Ivo Mueller
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Michael White
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France
- G5 Épidémiologie et Analyse des Maladies Infectieuses, Département de Santé Globale, Institut Pasteur, Paris, France
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Quang HH, Chavchich M, Trinh NTM, Manh ND, Edstein MD, Martin NJ, Edgel KA. Cross-sectional survey of asymptomatic malaria in Dak Nong province in the Central Highlands of Vietnam for the malaria elimination roadmap. PLoS One 2021; 16:e0258580. [PMID: 34669697 PMCID: PMC8528296 DOI: 10.1371/journal.pone.0258580] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 09/30/2021] [Indexed: 12/25/2022] Open
Abstract
Asymptomatic parasite carriers represent a "silent" infective reservoir for malaria transmission and contributes to malaria persistence. However, limited data are available on asymptomatic malaria in Vietnam. Between November 2018 and March 2019, we conducted a malaria epidemiological survey of asymptomatic people (children ≥ 10 years old and adults ≥18 years old, n = 2,809) residing in three communes in Tuy Duc district, Dak Nong province in the Central Highlands of Vietnam. Based on the national stratification of malaria risk, Dak Buk So, Dak Ngo and Quang Truc communes were classified by the National Malaria Control Programme as low, moderate and high malaria endemic areas, respectively. Using participants' finger prick blood samples, malaria parasites were detected by one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The median age (Interquartile Range) for adults and children were 35 years (26-50) and 12 years (11-14), respectively. The prevalence of asymptomatic malaria was 1.7% (22/1,328), 3.5% (31/890) and 12.2% (72/591) for participants from Dak Buk So, Dak Ngo and Quang Truc, respectively. The prevalence of asymptomatic malaria was lower in children compared to adults: 2.6% (9/352) versus 4.7% (116/2,457) (Odds Ratio 0.53, 95% Confidence Interval 0.28 to1.02). Ownership of long-lasting insecticide-treated bed nets and hammocks was 97.1%, 99.0% and 94.7% for participants in Dak Buk So, Dak Ngo and Quang Truc, respectively, however, only 66.0%, 57.3% and 42.8% of the participants reported using bed nets every night. Of the several risk factors examined, going to the forest two weeks prior to enrolment into the study and sleeping in the forest had a significant association with participants being infected with asymptomatic malaria in Quang Truc, but not in the other two communes. Knowledge of the prevalence and distribution of asymptomatic malaria will help design and evaluate future intervention strategies for malaria elimination in Vietnam.
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Affiliation(s)
- Huynh Hong Quang
- Institute of Malariology, Parasitology and Entomology, Quy Nhon, Vietnam
| | - Marina Chavchich
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
| | | | | | - Michael D. Edstein
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
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