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Barrett C, Chiphwanya J, Mkwanda S, Matipula DE, Ndhlovu P, Chaponda L, Turner JD, Giorgi E, Betts H, Martindale S, Taylor MJ, Read JM, Kelly-Hope LA. The national distribution of lymphatic filariasis cases in Malawi using patient mapping and geostatistical modelling. PLoS Negl Trop Dis 2024; 18:e0012056. [PMID: 38527064 PMCID: PMC11018277 DOI: 10.1371/journal.pntd.0012056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 04/15/2024] [Accepted: 03/10/2024] [Indexed: 03/27/2024] Open
Abstract
BACKGROUND In 2020 the World Health Organization (WHO) declared that Malawi had successfully eliminated lymphatic filariasis (LF) as a public health problem. Understanding clinical case distributions at a national and sub-national level is important, so essential care packages can be provided to individuals living with LF symptoms. This study aimed to develop a national database and map of LF clinical cases across Malawi using geostatistical modelling approaches, programme-identified clinical cases, antigenaemia prevalence and climate information. METHODOLOGY LF clinical cases identified through programme house-to-house surveys across 90 sub-district administrative boundaries (Traditional Authority (TA)) and antigenaemia prevalence from 57 sampled villages in Malawi were used in a two-step geostatistical modelling process to predict LF clinical cases across all TAs of the country. First, we modelled antigenaemia prevalence in relation to climate covariates to predict nationwide antigenaemia prevalence. Second, we modelled clinical cases for unmapped TAs based on our antigenaemia prevalence spatial estimates. PRINCIPLE FINDINGS The models estimated 20,938 (95% CrI 18,091 to 24,071) clinical cases in unmapped TAs (70.3%) in addition to the 8,856 (29.7%), programme-identified cases in mapped TAs. In total, the overall national number of LF clinical cases was estimated to be 29,794 (95% CrI 26,957 to 32,927). The antigenaemia prevalence and clinical case mapping and modelling found the highest burden of disease in Chikwawa and Nsanje districts in the Southern Region and Karonga district in the Northern Region of the country. CONCLUSIONS The models presented in this study have facilitated the development of the first national LF clinical case database and map in Malawi, the first endemic country in sub-Saharan Africa. It highlights the value of using existing LF antigenaemia prevalence and clinical case data together with modelling approaches to produce estimates that may be used for the WHO dossier requirements, to help target limited resources and implement long-term health strategies.
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Affiliation(s)
- Carrie Barrett
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - John Chiphwanya
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Square Mkwanda
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Dorothy E. Matipula
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Paul Ndhlovu
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Limbikani Chaponda
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Joseph D. Turner
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Emanuele Giorgi
- Lancaster Medical School, South West Drive, Bailrigg, Lancaster, United Kingdom
| | - Hannah Betts
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Sarah Martindale
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Mark J. Taylor
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Jonathan M. Read
- Lancaster Medical School, South West Drive, Bailrigg, Lancaster, United Kingdom
| | - Louise A. Kelly-Hope
- Centre for Neglected Tropical Disease, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
- Department of Livestock and One Health, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
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Chiphwanya J, Mkwanda S, Kabuluzi S, Mzilahowa T, Ngwira B, Matipula DE, Chaponda L, Ndhlova P, Katchika P, Mahebere Chirambo C, Moses P, Kumala J, Chiumia M, Barrett C, Betts H, Fahy J, Rebollo Polo M, Reimer L, Stanton MC, Thomas B, Freer S, Molyneux DH, Bockarie MJ, Mackenzie CD, Taylor MJ, Martindale S, Kelly-Hope LA. Elimination of lymphatic filariasis as a public health problem in Malawi. PLoS Negl Trop Dis 2024; 18:e0011957. [PMID: 38363794 PMCID: PMC10903958 DOI: 10.1371/journal.pntd.0011957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 02/29/2024] [Accepted: 02/01/2024] [Indexed: 02/18/2024] Open
Abstract
BACKGROUND Lymphatic filariasis (LF) is a parasitic disease transmitted by mosquitoes, causing severe pain, disfiguring, and disabling clinical conditions such as lymphoedema and hydrocoele. LF is a global public health problem affecting 72 countries, primarily in Africa and Asia. Since 2000, the World Health Organization (WHO) has led the Global Programme to Eliminate Lymphatic Filariasis (GPELF) to support all endemic regions. This paper focuses on the achievements of the Malawi LF Elimination Programme between 2000 and 2020 to eliminate LF as a public health problem, making it the second sub-Saharan country to receive validation from the WHO. METHODOLOGY/PRINCIPAL FINDINGS The Malawi LF Programme addressed the widespread prevalence of LF infection and disease across the country, using the recommended WHO GPELF strategies and operational research initiatives in collaboration with key national and international partners. First, to stop the spread of infection (i.e., interrupt transmission) and reduce the circulating filarial antigen prevalence from as high as 74.4% to below the critical threshold of 1-2% prevalence, mass drug administration (MDA) using a two-drug regime was implemented at high coverage rates (>65%) of the total population, with supplementary interventions from other programmes (e.g., malaria vector control). The decline in prevalence was monitored and confirmed over time using several impact assessment and post-treatment surveillance tools including the standard sentinel site, spot check, and transmission assessment surveys and alternative integrated, hotspot, and easy-access group surveys. Second, to alleviate suffering of the affected populations (i.e., control morbidity) the morbidity management and disability prevention (MMDP) package of care was implemented. Specifically, clinical case estimates were obtained via house-to-house patient searching activities; health personnel and patients were trained in self-care protocols for lymphoedema and/or referrals to hospitals for hydrocoele surgery; and the readiness and quality of treatment and services were assessed with new survey tools. CONCLUSIONS Malawi's elimination of LF will ensure that future generations are not infected and suffer from the disfiguring and disabling disease. However, it will be critical that the Malawi LF Elimination programme remains vigilant, focussing on post-elimination surveillance and MMDP implementation and integration into routine health systems to support long-term sustainability and ongoing success. SUMMARY Lymphatic filariasis, also known as elephantiasis, is a disabling, disfiguring, and painful disease caused by a parasite that infected mosquitoes transmit to millions of people worldwide. Since 2000, the Global Programme to Eliminate Lymphatic Filariasis (GPELF) has supported endemic countries such as Malawi in south-eastern Africa, to eliminate the disease as a public health problem. The Malawi National LF Elimination Programme has worked tirelessly over the past two decades to implement the GPELF recommended strategies to interrupt the transmission with a two-drug regime, and to alleviate suffering in patients with lymphoedema and/or hydrocoele through morbidity management and disability prevention. Additionally, the LF Programme has collaborated with national and international stakeholders to implement a range of supplementary operational research projects to address outstanding knowledge gaps and programmatic barriers. In 2020, the World Health Organisation validated that Malawi had successfully eliminated LF as a public health problem, making it the second country in sub-Saharan Africa to achieve this, which is remarkable given that Malawi previously had very high infection rates. The LF Programme now remains vigilant, putting its efforts towards post-elimination surveillance and the continued implementation of care for patients with chronic conditions. Malawi's elimination of LF will ensure that future generations are not affected by this devastating disease.
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Affiliation(s)
| | | | | | - Themba Mzilahowa
- Malaria Alert Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
- Centre for Health, Agriculture, Development Research, and Consulting, Blantyre, Malawi
| | - Bagrey Ngwira
- Centre for Health, Agriculture, Development Research, and Consulting, Blantyre, Malawi
| | | | | | | | | | | | - Philemon Moses
- Centre for Health, Agriculture, Development Research, and Consulting, Blantyre, Malawi
| | - Justin Kumala
- Malaria Alert Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Martin Chiumia
- Malaria Alert Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Carrie Barrett
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Hannah Betts
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Joan Fahy
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Maria Rebollo Polo
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- World Health Organization, Geneva, Switzerland
| | - Lisa Reimer
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Michelle C. Stanton
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Brent Thomas
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Sian Freer
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - David H. Molyneux
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Moses J. Bockarie
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- School of Community Health Sciences, Njala University, Bo, Sierra Leone
| | - Charles D. Mackenzie
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Mark J. Taylor
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Sarah Martindale
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Louise A. Kelly-Hope
- Centre for Neglected Tropical Diseases, Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
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Maekawa Y, Pemba D, Kumala J, Gowelo S, Higa Y, Futami K, Sawabe K, Tsuda Y. DNA barcoding of mosquitoes collected through a nationwide survey in 2011 and 2012 in Malawi, Southeast Africa. Acta Trop 2021; 213:105742. [PMID: 33159897 DOI: 10.1016/j.actatropica.2020.105742] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 09/09/2020] [Accepted: 09/24/2020] [Indexed: 01/20/2023]
Abstract
We conducted a nationwide survey of mosquito distribution in Malawi from November 2011 to April 2012, and from July to September 2012. Using dried specimens of mosquito adults collected during the survey, we analyzed their cytochrome c oxidase subunit I (COI) gene sequences, prepared specimens, and registered the genetic information (658 bp) of 144 individuals belonging to 51 species of 10 genera in GenBank. Using the obtained genetic information, we analyzed the degree of intraspecific variation and investigated the various species from morphological and genetic perspectives. Moreover, we conducted phylogenetic analysis of the medically important species distributed from Africa to Asia and explored their geographical differentiation. Results showed that individuals morphologically classified as Culex univittatus complex included a individual of Cx. perexiguus which, to date, have not been reported in southern Africa. Furthermore, Mansonia uniformis, distributed in Africa and Asia, was revealed to belong to genetically distinct populations, with observed morphological differences of the samples suggesting that they are separate species. The results of genetic analysis further suggested that Cx. ethiopicus is not a synonym of Cx. bitaeniorhynchus, but that it is an independent species; although, in this study, the only definite morphological difference observed was in the shape of the wing scales. Further morphological and genetic investigation of individuals of these species, including larvae, is highly recommended.
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Biting patterns of malaria vectors of the lower Shire valley, southern Malawi. Acta Trop 2019; 197:105059. [PMID: 31194960 DOI: 10.1016/j.actatropica.2019.105059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 06/06/2019] [Accepted: 06/07/2019] [Indexed: 12/13/2022]
Abstract
Assessing the biting behaviour of malaria vectors plays an integral role in understanding the dynamics of malaria transmission in a region. Biting times and preference for biting indoors or outdoors varies among mosquito species and across regions. These behaviours may also change over time in response to vector control measures such as long-lasting insecticidal nets (LLINs). Data on these parameters can provide the sites and times at which different interventions would be effective for vector control. This study assessed the biting patterns of malaria vectors in Chikwawa district, southern Malawi. The study was conducted during the dry and wet seasons in 2016 and 2017, respectively. In each season, mosquitoes were collected indoors and outdoors for 24 nights in six houses per night using the human landing catch. Volunteers were organized into six teams of two individuals, whereby three teams collected mosquitoes indoors and the other three collected mosquitoes outdoors each night, and the teams were rotated among twelve houses. All data were analyzed using Poisson log-linear models. The most abundant species were Anopheles gambiae sensu lato (primarily An. arabiensis) and An. funestus s.l. (exclusively An. funestus s.s.). During the dry season, the biting activity of An. gambiaes.l. was constant outdoors across the categorized hours (18:00 h to 08:45 h), but highest in the late evening hours (21:00 h to 23:45 h) during the wet season. The biting activity of An. funestus s.l. was highest in the late evening hours (21:00 h to 23:45 h) during the dry season and in the late night hours (03:00 h to 05:45 h) during the wet season. Whereas the number of An. funestuss.l. biting was constant (P = 0.662) in both seasons, that of An. gambiaes.l. was higher during the wet season than in the dry season (P = 0.001). Anopheles gambiae s.l. was more likely to bite outdoors than indoors in both seasons. During the wet season, An. funestus s.l. was more likely to bite indoors than outdoors but during the dry season, the bites were similar both indoors and outdoors. The biting activity that occurred in the early and late evening hours, both indoors and outdoors coincides with the times at which individuals may still be awake and physically active, and therefore unprotected by LLINs. Additionally, a substantial number of anopheline bites occurred outdoors. These findings imply that LLINs would only provide partial protection from malaria vectors, which would affect malaria transmission in this area. Therefore, protection against bites by malaria mosquitoes in the early and late evening hours is essential and can be achieved by designing interventions that reduce vector-host contacts during this period.
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Mzilahowa T, Luka-Banda M, Uzalili V, Mathanga DP, Campbell CH, Mukaka M, Gimnig JE. Risk factors for Anopheles mosquitoes in rural and urban areas of Blantyre District, southern Malawi. Malawi Med J 2017; 28:154-158. [PMID: 28321278 DOI: 10.4314/mmj.v28i4.2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Although urban malaria transmission is low and seasonal, it remains a major public health problem. This study aimed at demonstrating the presence of Anopheles mosquitoes and their potential to transmit malaria in urban settings. METHODS Two cross-sectional surveys were carried out in Blantyre District, Malawi, during the dry and wet seasons of 2008 and 2010, respectively. A map of Blantyre was divided into a grid of 400 cells, of which 60 cells were randomly selected. Five households located within 100 m from the centre of each selected cell were enrolled, a standard questionnaire was administered, and indoor resting mosquitoes were sampled. RESULTS In 2008 and 2010, a total of 960 and 1045 mosquitoes were collected, respectively. Anopheles funestus comprised 9.9% (n = 95) and 10.3% (n = 108) during the two surveys, respectively. Anopheles gambiae sensu lato (s.l.) was rarely detected during the second survey (n = 6; 0.6%). Molecular identification was performed on samples collected during the first survey, and An. funestus sensu stricto (s.s.) was the only sibling species detected. All the Anopheles mosquitoes were collected from households located in rural areas of Blantyre and none from urban areas. In univariate analysis, the presence of open eaves was associated with increased Anopheles prevalence, both during the dry (incidence rate ratio, IRR = 4.3; 95% CI 2.4 - 7.6) and wet (IRR = 2.47; 95% CI 1.7 - 3.59) seasons. Chances of detecting Anopheles spp. decreased with increasing altitude (IRR = 0.996; 95% CI 0.995 - 0.997) and during the dry season, but increased during the wet season (IRR = 1.0017; 95% CI 1.0012 - 1.0023). These factors remained significant following a multiple Poisson regression analysis. No association was found between insecticide-treated bednet ownership and the number of Anopheles mosquitoes detected. CONCLUSIONS The presence of An. funestus s.s and An. gambiae s.l. in the periphery of Blantyre city was an indication that malaria transmission was potentially taking place in these areas.
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Affiliation(s)
- Themba Mzilahowa
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Madalitso Luka-Banda
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Veronica Uzalili
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Don P Mathanga
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Carl H Campbell
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
| | - Mavuto Mukaka
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - John E Gimnig
- Entomology Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Conn JE, Norris DE, Donnelly MJ, Beebe NW, Burkot TR, Coulibaly MB, Chery L, Eapen A, Keven JB, Kilama M, Kumar A, Lindsay SW, Moreno M, Quinones M, Reimer LJ, Russell TL, Smith DL, Thomas MB, Walker ED, Wilson ML, Yan G. Entomological Monitoring and Evaluation: Diverse Transmission Settings of ICEMR Projects Will Require Local and Regional Malaria Elimination Strategies. Am J Trop Med Hyg 2015; 93:28-41. [PMID: 26259942 PMCID: PMC4574272 DOI: 10.4269/ajtmh.15-0009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/20/2015] [Indexed: 01/29/2023] Open
Abstract
The unprecedented global efforts for malaria elimination in the past decade have resulted in altered vectorial systems, vector behaviors, and bionomics. These changes combined with increasingly evident heterogeneities in malaria transmission require innovative vector control strategies in addition to the established practices of long-lasting insecticidal nets and indoor residual spraying. Integrated vector management will require focal and tailored vector control to achieve malaria elimination. This switch of emphasis from universal coverage to universal coverage plus additional interventions will be reliant on improved entomological monitoring and evaluation. In 2010, the National Institutes for Allergies and Infectious Diseases (NIAID) established a network of malaria research centers termed ICEMRs (International Centers for Excellence in Malaria Research) expressly to develop this evidence base in diverse malaria endemic settings. In this article, we contrast the differing ecology and transmission settings across the ICEMR study locations. In South America, Africa, and Asia, vector biologists are already dealing with many of the issues of pushing to elimination such as highly focal transmission, proportionate increase in the importance of outdoor and crepuscular biting, vector species complexity, and "sub patent" vector transmission.
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Affiliation(s)
- Jan E. Conn
- *Address correspondence to Jan E. Conn, Griffin Laboratory, The Wadsworth Center, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY 12159. E-mail:
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Smith EL, Mkwanda SZ, Martindale S, Kelly-Hope LA, Stanton MC. Lymphatic filariasis morbidity mapping: a comprehensive examination of lymphoedema burden in Chikwawa district, Malawi. Trans R Soc Trop Med Hyg 2014; 108:751-8. [PMID: 25282001 DOI: 10.1093/trstmh/tru150] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Managing lymphatic filariasis (LF) morbidity and reducing disability is one of the two primary goals of the Global Programme to Eliminate Lymphatic Filariasis. However, in order to achieve this, the geographical distribution of LF morbidity needs to be better estimated. METHODS All cases of lymphoedema within a single health centre catchment area (pop. 42 000) in the southern region of Malawi were examined. Maps of lymphoedema burden were produced and trends in patient demographics, severity of lymphoedema (Dreyer staging) and health-seeking behaviour were explored. The number of lymphoedema cases was compared with records maintained by the Ministry of Health, Malawi. RESULTS A total of 69 lymphoedema cases were identified (32 per 10 000 population), of which 48 (70%) were female and 21 (30%) male. The majority of cases (51/69) had Dreyer stage 2-3, and almost all (65/69) had experienced acute attacks as a result of their lymphoedema. This burden was much greater than that estimated by Ministry of Health (33 cases). CONCLUSIONS Current case detection methods underestimate the burden of lymphoedema in Malawi. There is a continued need to develop new LF morbidity identification and surveillance approaches to ensure that future morbidity management strategies are effectively targeted.
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Affiliation(s)
- Emma L Smith
- Centre for Neglected Tropical Diseases, Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Square Z Mkwanda
- National Lymphatic Filariasis Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Sarah Martindale
- Centre for Neglected Tropical Diseases, Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Louise A Kelly-Hope
- Centre for Neglected Tropical Diseases, Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Michelle C Stanton
- Centre for Neglected Tropical Diseases, Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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Shawa ST, Mwase ET, Pedersen EM, Simonsen PE. Lymphatic filariasis in Luangwa District, South-East Zambia. Parasit Vectors 2013; 6:299. [PMID: 24499525 PMCID: PMC3853755 DOI: 10.1186/1756-3305-6-299] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 10/04/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Past case reports and recent data from LF mapping surveys indicate that LF occurs in Zambia, but no studies have been carried out to document its epidemiology and health implications. The present study assessed infection, disease, transmission and human perception aspects of LF in an endemic area of Luangwa District, South-East Zambia, as a background for planning and implementation of control. METHODS Two neighbouring rural communities were registered and a questionnaire survey undertaken. Clinical examination, and sampling of blood for circulating filarial antigens (CFA; marker of adult worm infection) and antibodies to Bm14 antigen (marker of exposure to transmission), were carried out during the daytime. Blood from CFA positive individuals was examined for microfilariae (mf) at night. Vector surveys were carried out in selected households, using light traps. RESULTS 985 individuals aged ≥ 1 year were registered. The CFA prevalence increased with age from 1.2% in age group 1-14 years to 20.6% in age group 50+ years (overall 8.6%). Wuchereria bancrofti mf were identified in 10.9% of CFA positive individuals (corresponding to a community prevalence of 0.9%). Prevalence and intensity of Bm14 antibodies were much higher in individuals ≥ 30 years than in younger individuals (57.2 vs. 19.3%; 0.594 vs. 0.241 OD-values). Elephantiasis and hydrocele were well known clinical manifestations in the area, but only one case of hydrocele was detected in the study population. Identified potential vectors were Anopheles funestus and An. gambiae. CONCLUSION The study confirmed that LF was endemic in the study communities, but infection and disease prevalence was low. Several indications, including a marked recent decline in CFA prevalence, suggest that transmission in the area is on the decrease, perhaps because of intensive application of malaria control measures targeting the Anopheles vectors. It is recommended that mass drug administration is initiated to accelerate this positive trend of decline in LF transmission in the area.
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Affiliation(s)
| | | | | | - Paul E Simonsen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Thorvaldsensvej 57, 1871 Frederiksberg C, Denmark.
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Mzilahowa T, Hastings IM, Molyneux ME, McCall PJ. Entomological indices of malaria transmission in Chikhwawa district, Southern Malawi. Malar J 2012; 11:380. [PMID: 23171123 PMCID: PMC3536595 DOI: 10.1186/1475-2875-11-380] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 11/08/2012] [Indexed: 12/02/2022] Open
Abstract
Background Although malaria is highly prevalent throughout Malawi, little is known of its transmission dynamics. This paper describes the seasonal activity of the different vectors, human biting indices, sporozoite rates and the entomological inoculation rate in a low-lying rural area in southern Malawi. Methods Vectors were sampled over 52 weeks from January 2002 to January 2003, by pyrethrum knockdown catch in two villages in Chikhwawa district, in the Lower Shire Valley. Results In total, 7,717 anophelines were collected of which 55.1% were Anopheles gambiae sensu lato and 44.9% were Anopheles funestus. Three members of the An. gambiae complex were identified by PCR: Anopheles arabiensis (75%) was abundant throughout the year, An. gambiae s.s. (25%) was most common during the wet season and Anopheles quadriannulatus occurred at a very low frequency (n=16). An. funestus was found in all samples but was most common during the dry season. Anopheles gambiae s.s. and An. funestus were highly anthropophilic with human blood indices of 99.2% and 96.3%, respectively. Anopheles arabiensis had fed predominantly on humans (85.0%) and less commonly on cattle (10.9%; 1.2% of blood meals were of mixed origin). Plasmodium falciparum (192/3,984) and Plasmodium malariae (1/3,984) sporozoites were detected by PCR in An. arabiensis (3.2%) and An. funestus (4.5%), and in a significantly higher proportion of An. gambiae s.s. (10.6%)(p<0.01). All three vectors were present throughout the year and malaria transmission occurred in every month, although with greatest intensity during the rainy season (January to April). The combined human blood index exceeded 92% and the P. falciparum sporozoite rate was 4.8%, resulting in estimated inoculation rates of 183 infective bites/ person per annum, or an average rate of ~15 infective bites/person/month. Conclusions The results demonstrate the importance of An. gambiae s.s., An. arabiensis and An. funestus in driving the high levels of malaria transmission in the south of Malawi. Sustained and high coverage or roll out of current approaches to malaria control (primarily insecticide-treated bed nets and indoor residual house spraying) in the area are likely to reduce the observed high malaria transmission rate and consequently the incidence of human infections, unless impeded by increasing resistance of vectors to insecticides.
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Affiliation(s)
- Themba Mzilahowa
- Liverpool School of Tropical Medicine, Liverpool, Pembroke Place, UK.
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Onapa AW, Pedersen EM, Reimert CM, Simonsen PE. A role for Mansonia uniformis mosquitoes in the transmission of lymphatic filariasis in Uganda? Acta Trop 2007; 101:159-68. [PMID: 17316535 DOI: 10.1016/j.actatropica.2007.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Revised: 11/27/2006] [Accepted: 12/08/2006] [Indexed: 11/21/2022]
Abstract
The possible role of Mansonia uniformis mosquitoes in the transmission of lymphatic filariasis was assessed in an endemic area of Uganda, by examining their diurnal biting cycle, host preference and ability to support the development of experimental and natural Wuchereria bancrofti infections. Anopheles gambiae s.l. served as controls. Human landing catches revealed that outdoor biting peaked early in the evening (19:00-20:00h), while indoor biting peaked around midnight (23:00-24:00h). By far the majority of indoor collected M. uniformis had derived their blood meals from humans. Both biting and feeding behaviour were therefore compatible with a potential for transmission. In experimentally fed M. uniformis (total of 1915), the microfilariae were seen to ex-sheath and to start migration, but the L1s accumulated in the thorax and only few developed further. In dissections from Day 11 onwards, 4.6% (43/932) of M. uniformis had L2 larvae and 0.7% (7/932) had L3 larvae of W. bancrofti. The corresponding figures for An. gambiae s.l. were 13.4% and 4.6%, respectively. Dissection of wild caught M. uniformis (total of 6823) did not reveal any natural infections with W. bancrofti infective larvae, whereas wild caught An. gambiae s.l. had an infective rate of 1.3%. Other filarial species, and mermithids, were common in M. uniformis. It is concluded that M. uniformis has a limited potential to support development of W. bancrofti to the infective stage, and it does not appear to play a role as a vector under natural conditions.
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Affiliation(s)
- Ambrose W Onapa
- Vector Control Division, Ministry of Health, P.O. Box 1661, Kampala, Uganda
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