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Shaw C, McLure A, Graves PM, Lau CL, Glass K. Lymphatic filariasis endgame strategies: Using GEOFIL to model mass drug administration and targeted surveillance and treatment strategies in American Samoa. PLoS Negl Trop Dis 2023; 17:e0011347. [PMID: 37200375 DOI: 10.1371/journal.pntd.0011347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 05/31/2023] [Accepted: 04/29/2023] [Indexed: 05/20/2023] Open
Abstract
American Samoa underwent seven rounds of mass drug administration (MDA) for lymphatic filariasis (LF) from 2000-2006, but subsequent surveys found evidence of ongoing transmission. American Samoa has since undergone further rounds of MDA in 2018, 2019, and 2021; however, recent surveys indicate that transmission is still ongoing. GEOFIL, a spatially-explicit agent-based LF model, was used to compare the effectiveness of territory-wide triple-drug MDA (3D-MDA) with targeted surveillance and treatment strategies. Both approaches relied on treatment with ivermectin, diethylcarbamazine, and albendazole. We simulated three levels of whole population coverage for 3D-MDA: 65%, 73%, and 85%, while the targeted strategies relied on surveillance in schools, workplaces, and households, followed by targeted treatment. In the household-based strategies, we simulated 1-5 teams travelling village-to-village and offering antigen (Ag) testing to randomly selected households in each village. If an Ag-positive person was identified, treatment was offered to members of all households within 100m-1km of the positive case. All simulated interventions were finished by 2027 and their effectiveness was judged by their 'control probability'-the proportion of simulations in which microfilariae prevalence decreased between 2030 and 2035. Without future intervention, we predict Ag prevalence will rebound. With 3D-MDA, a 90% control probability required an estimated ≥ 4 further rounds with 65% coverage, ≥ 3 rounds with 73% coverage, or ≥ 2 rounds with 85% coverage. While household-based strategies were substantially more testing-intensive than 3D-MDA, they could offer comparable control probabilities with substantially fewer treatments; e.g. three teams aiming to test 50% of households and offering treatment to a 500m radius had approximately the same control probability as three rounds of 73% 3D-MDA, but used < 40% the number of treatments. School- and workplace-based interventions proved ineffective. Regardless of strategy, reducing Ag prevalence below the 1% target threshold recommended by the World Health Organization was a poor indicator of the interruption of LF transmission, highlighting the need to review blanket elimination targets.
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Affiliation(s)
- Callum Shaw
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia
| | - Angus McLure
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia
| | - Patricia M Graves
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, Queensland, Australia
| | - Colleen L Lau
- School of Public Health, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Kathryn Glass
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia
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Potential strategies for strengthening surveillance of lymphatic filariasis in American Samoa after mass drug administration: Reducing 'number needed to test' by targeting older age groups, hotspots, and household members of infected persons. PLoS Negl Trop Dis 2020; 14:e0008916. [PMID: 33370264 PMCID: PMC7872281 DOI: 10.1371/journal.pntd.0008916] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 02/09/2021] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
Under the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted mass drug administration (MDA) from 2000-2006. Despite passing Transmission Assessment Surveys (TAS) in 2011/2012 and 2015, American Samoa failed TAS-3 in 2016, with antigen (Ag) prevalence of 0.7% (95%CI 0.3-1.8%) in 6-7 year-olds. A 2016 community survey (Ag prevalence 6.2% (95%CI 4.4-8.5%) in age ≥8 years) confirmed resurgence. Using data from the 2016 survey, this study aims to i) investigate antibody prevalence in TAS-3 and the community survey, ii) identify risk factors associated with being seropositive for Ag and anti-filarial antibodies, and iii) compare the efficiency of different sampling strategies for identifying seropositive persons in the post-MDA setting. Antibody prevalence in TAS-3 (n = 1143) were 1.6% for Bm14 (95%CI 0.9-2.9%), 7.9% for Wb123 (95%CI 6.4-9.6%), and 20.2% for Bm33 (95%CI 16.7-24.3%); and in the community survey (n = 2507), 13.9% for Bm14 (95%CI 11.2-17.2%), 27.9% for Wb123 (95%CI 24.6-31.4%), and 47.3% for Bm33 (95%CI 42.1-52.6%). Multivariable logistic regression was used to identify risk factors for being seropositive for Ag and antibodies. Higher Ag prevalence was found in males (adjusted odds ratio [aOR] 3.01), age ≥18 years (aOR 2.18), residents of Fagali'i (aOR 15.81), and outdoor workers (aOR 2.61). Ag prevalence was 20.7% (95%CI 9.7-53.5%) in households of Ag-positive children identified in TAS-3. We used NNTestav (average number needed to test to identify one positive) to compare the efficiency of the following strategies for identifying persons who were seropositive for Ag and each antibody: i) TAS of 6-7 year-old children, ii) population representative surveys of older age groups, and iii) targeted surveillance of subpopulations at higher risk of being seropositive (older ages, householders of Ag-positive TAS children, and known hotspots). For Ag, NNTestav ranged from 142.5 for TAS, to <5 for households of index children. NNTestav was lower in older ages, and highest for Ag, followed by Bm14, Wb123 and Bm33 antibodies. We propose a multi-stage surveillance strategy, starting with population-representative sampling (e.g. TAS or population representative survey of older ages), followed by strategies that target subpopulations and/or locations with low NNTestav. This approach could potentially improve the efficiency of identifying remaining infected persons and residual hotspots. Surveillance programs should also explore the utility of antibodies as indicators of transmission.
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Mayfield HJ, Sturrock H, Arnold BF, Andrade-Pacheco R, Kearns T, Graves P, Naseri T, Thomsen R, Gass K, Lau CL. Supporting elimination of lymphatic filariasis in Samoa by predicting locations of residual infection using machine learning and geostatistics. Sci Rep 2020; 10:20570. [PMID: 33239779 PMCID: PMC7689447 DOI: 10.1038/s41598-020-77519-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 11/11/2020] [Indexed: 11/26/2022] Open
Abstract
The global elimination of lymphatic filariasis (LF) is a major focus of the World Health Organization. One key challenge is locating residual infections that can perpetuate the transmission cycle. We show how a targeted sampling strategy using predictions from a geospatial model, combining random forests and geostatistics, can improve the sampling efficiency for identifying locations with high infection prevalence. Predictions were made based on the household locations of infected persons identified from previous surveys, and environmental variables relevant to mosquito density. Results show that targeting sampling using model predictions would have allowed 52% of infections to be identified by sampling just 17.7% of households. The odds ratio for identifying an infected individual in a household at a predicted high risk compared to a predicted low risk location was 10.2 (95% CI 4.2-22.8). This study provides evidence that a 'one size fits all' approach is unlikely to yield optimal results when making programmatic decisions based on model predictions. Instead, model assumptions and definitions should be tailored to each situation based on the objective of the surveillance program. When predictions are used in the context of the program objectives, they can result in a dramatic improvement in the efficiency of locating infected individuals.
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Affiliation(s)
- Helen J Mayfield
- Research School of Population Health, Australian National University, Canberra, Australia.
| | - Hugh Sturrock
- Global Health Group, University of California, San Francisco, San Francisco, USA
| | - Benjamin F Arnold
- Proctor Foundation, University of California, San Francisco, San Francisco, USA
| | | | - Therese Kearns
- Menzies School of Health Research, Charles Darwin University, Brisbane, Australia
| | - Patricia Graves
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD, Australia
| | | | | | - Katherine Gass
- Neglected Tropical Diseases Support Center, Task Force for Global Heath, Decatur, GA, USA
| | - Colleen L Lau
- Research School of Population Health, Australian National University, Canberra, Australia
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Noordin R, Yunus MH, Robinson K, Won KY, Babu S, Fischer PU, Hisam S, Mahmud R. Laboratory Evaluation of a Rapid IgG4 Antibody Test (BLF Rapid™) for Bancroftian Filariasis. Am J Trop Med Hyg 2019; 99:1587-1590. [PMID: 30350768 DOI: 10.4269/ajtmh.18-0566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
At the end phase of the Global Programme to Eliminate Lymphatic Filariasis, antibody testing may have a role in decision-making for bancroftian filariasis-endemic areas. This study evaluated the diagnostic performance of BLF Rapid™, a prototype immunochromatographic IgG4-based test using BmSXP recombinant protein, for detection of bancroftian filariasis. The test was evaluated using 258 serum samples, comprising 96 samples tested at Universiti Sains Malaysia (in-house) and 162 samples tested independently at three international laboratories in the USA and India, and two laboratories in Malaysia. The independent testing involved 99 samples from Wuchereria bancrofti microfilaria or antigen positive individuals and 63 samples from people who were healthy or had other infections. The in-house evaluation showed 100% diagnostic sensitivity and specificity. The independent evaluations showed a diagnostic sensitivity of 84-100% and 100% specificity (excluding non-lymphatic filarial infections). BLF Rapid has potential as a surveillance diagnostic tool to make "Transmission Assessment Survey"-stopping decisions and conduct post-elimination surveillance.
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Affiliation(s)
- Rahmah Noordin
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Pulau Pinang, Malaysia
| | - Muhammad Hafiznur Yunus
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Pulau Pinang, Malaysia
| | - Keri Robinson
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Kimberly Y Won
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Subash Babu
- National Institutes of Health-International Center for Excellence in Research, National Institute of Research in Tuberculosis, Chennai, India
| | - Peter U Fischer
- Infectious Diseases Division, Washington University School of Medicine, St. Louis, Missouri
| | - Shamilah Hisam
- Parasitology Unit, Institute for Medical Research, Kuala Lumpur, Malaysia
| | - Rohela Mahmud
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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McCann RS, van den Berg H, Takken W, Chetwynd AG, Giorgi E, Terlouw DJ, Diggle PJ. Reducing contamination risk in cluster-randomized infectious disease-intervention trials. Int J Epidemiol 2019; 47:2015-2024. [PMID: 30376050 DOI: 10.1093/ije/dyy213] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2018] [Indexed: 11/13/2022] Open
Abstract
Background Infectious disease interventions are increasingly tested using cluster-randomized trials (CRTs). These trial settings tend to involve a set of sampling units, such as villages, whose geographic arrangement may present a contamination risk in treatment exposure. The most widely used approach for reducing contamination in these settings is the so-called fried-egg design, which excludes the outer portion of all available clusters from the primary trial analysis. However, the fried-egg design ignores potential intra-cluster spatial heterogeneity and makes the outcome measure inherently less precise. Whereas the fried-egg design may be appropriate in specific settings, alternative methods to optimize the design of CRTs in other settings are lacking. Methods We present a novel approach for CRT design that either fully includes or fully excludes available clusters in a defined study region, recognizing the potential for intra-cluster spatial heterogeneity. The approach includes an algorithm that allows investigators to identify the maximum number of clusters that could be included for a defined study region and maintain randomness in both the selection of included clusters and the allocation of clusters to either the treatment group or control group. The approach was applied to the design of a CRT testing the effectiveness of malaria vector-control interventions in southern Malawi. Conclusions Those planning CRTs to evaluate interventions should consider the approach presented here during trial design. The approach provides a novel framework for reducing the risk of contamination among the CRT randomization units in settings where investigators determine the reduction of contamination risk as a high priority and where intra-cluster spatial heterogeneity is likely. By maintaining randomness in the allocation of clusters to either the treatment group or control group, the approach also permits a randomization-valid test of the primary trial hypothesis.
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Affiliation(s)
- Robert S McCann
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Amanda G Chetwynd
- Department of Mathematics and Statistics, Lancaster University, Lancaster, United Kingdom
| | - Emanuele Giorgi
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Dianne J Terlouw
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Clinical Research Program, Blantyre, Malawi.,Clinical Sciences Department, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Peter J Diggle
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
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Joseph H, Sullivan S, Wood P, Melrose W, Taleo F, Graves P. Investigation of Mixture Modelling Algorithms as a Tool for Determining the Statistical Likelihood of Serological Exposure to Filariasis Utilizing Historical Data from the Lymphatic Filariasis Surveillance Program in Vanuatu. Trop Med Infect Dis 2019; 4:tropicalmed4010045. [PMID: 30857178 PMCID: PMC6473238 DOI: 10.3390/tropicalmed4010045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/01/2019] [Accepted: 03/03/2019] [Indexed: 11/16/2022] Open
Abstract
As the prevalence of lymphatic filariasis declines, it becomes crucial to adequately eliminate residual areas of endemicity and implement surveillance. To this end, serological assays have been developed, including the Bm14 Filariasis CELISA which recommends a specific optical density cut-off level. We used mixture modelling to assess positive cut-offs of Bm14 serology in children in Vanuatu using historical OD (Optical Density) ELISA values collected from a transmission assessment survey (2005) and a targeted child survey (2008). Mixture modelling is a statistical technique using probability distributions to identify subpopulations of positive and negative results (absolute cut-off value) and an 80% indeterminate range around the absolute cut-off (80% cut-off). Depending on programmatic choices, utilizing the lower 80% cut-off ensures the inclusion of all likely positives, however with the trade-off of lower specificity. For 2005, country-wide antibody prevalence estimates varied from 6.4% (previous cut-off) through 9.0% (absolute cut-off) to 17.3% (lower 80% cut-off). This corroborated historical evidence of hotspots in Pentecost Island in Penama province. For 2008, there were no differences in the prevalence rates using any of the thresholds. In conclusion, mixture modelling is a powerful tool that allows closer monitoring of residual transmission spots and these findings supported additional monitoring which was conducted in Penama in later years. Utilizing a statistical data-based cut-off, as opposed to a universal cut-off, may help guide program decisions that are better suited to the national program.
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Affiliation(s)
- Hayley Joseph
- The Walter and Eliza Hall Institute of Medical Research, Division of Population Health and Immunity, Melbourne, VIC 3052, Australia.
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC 3052, Australia.
| | - Sarah Sullivan
- Neglected Tropical Diseases Support Center, The Task Force for Global Health, Decatur, GA 30030, USA.
| | - Peter Wood
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD 4878, Australia.
- Great Barrier Reef Legacy, Cairns, QLD 4877, Australia.
| | - Wayne Melrose
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD 4878, Australia.
| | - Fasihah Taleo
- Vector Borne Disease Unit, Ministry of Health, Port Vila, Vanuatu.
| | - Patricia Graves
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD 4878, Australia.
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Lau CL, Sheridan S, Ryan S, Roineau M, Andreosso A, Fuimaono S, Tufa J, Graves PM. Detecting and confirming residual hotspots of lymphatic filariasis transmission in American Samoa 8 years after stopping mass drug administration. PLoS Negl Trop Dis 2017; 11:e0005914. [PMID: 28922418 PMCID: PMC5619835 DOI: 10.1371/journal.pntd.0005914] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 09/28/2017] [Accepted: 08/28/2017] [Indexed: 11/18/2022] Open
Abstract
The Global Programme to Eliminate Lymphatic Filariasis (LF) aims to eliminate the disease as a public health problem by 2020 by conducting mass drug administration (MDA) and controlling morbidity. Once elimination targets have been reached, surveillance is critical for ensuring that programmatic gains are sustained, and challenges include timely identification of residual areas of transmission. WHO guidelines encourage cost-efficient surveillance, such as integration with other population-based surveys. In American Samoa, where LF is caused by Wuchereria bancrofti, and Aedes polynesiensis is the main vector, the LF elimination program has made significant progress. Seven rounds of MDA (albendazole and diethycarbamazine) were completed from 2000 to 2006, and Transmission Assessment Surveys were passed in 2010/2011 and 2015. However, a seroprevalence study using an adult serum bank collected in 2010 detected two potential residual foci of transmission, with Og4C3 antigen (Ag) prevalence of 30.8% and 15.6%. We conducted a follow up study in 2014 to verify if transmission was truly occurring by comparing seroprevalence between residents of suspected hotspots and residents of other villages. In adults from non-hotspot villages (N = 602), seroprevalence of Ag (ICT or Og4C3), Bm14 antibody (Ab) and Wb123 Ab were 1.2% (95% CI 0.6-2.6%), 9.6% (95% CI 7.5%-12.3%), and 10.5% (95% CI 7.6-14.3%), respectively. Comparatively, adult residents of Fagali'i (N = 38) had significantly higher seroprevalence of Ag (26.9%, 95% CI 17.3-39.4%), Bm14 Ab (43.4%, 95% CI 32.4-55.0%), and Wb123 Ab 55.2% (95% CI 39.6-69.8%). Adult residents of Ili'ili/Vaitogi/Futiga (N = 113) also had higher prevalence of Ag and Ab, but differences were not statistically significant. The presence of transmission was demonstrated by 1.1% Ag prevalence (95% CI 0.2% to 3.1%) in 283 children aged 7-13 years who lived in one of the suspected hotspots; and microfilaraemia in four individuals, all of whom lived in the suspected hotspots, including a 9 year old child. Our results provide field evidence that integrating LF surveillance with other surveys is effective and feasible for identifying potential hotspots, and conducting surveillance at worksites provides an efficient method of sampling large populations of adults.
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Affiliation(s)
- Colleen L. Lau
- Department of Global Health, Research School of Population Health, The Australian National University, Canberra, Australia
- Children’s Health and Environment Program, Child Health Research Centre, The University of Queensland, Brisbane, Australia
| | - Sarah Sheridan
- Department of Global Health, Research School of Population Health, The Australian National University, Canberra, Australia
| | - Stephanie Ryan
- Australian Institute of Tropical Health and Medicine and College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, Australia
| | - Maureen Roineau
- Australian Institute of Tropical Health and Medicine and College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, Australia
| | - Athena Andreosso
- Australian Institute of Tropical Health and Medicine and College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, Australia
| | - Saipale Fuimaono
- Department of Public Health, American Samoa Department of Health, Pago Pago, American Samoa
| | - Joseph Tufa
- Department of Public Health, American Samoa Department of Health, Pago Pago, American Samoa
| | - Patricia M. Graves
- Australian Institute of Tropical Health and Medicine and College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, Australia
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Kshirsagar NA, Gogtay NJ, Garg BS, Deshmukh PR, Rajgor DD, Kadam VS, Thakur PA, Gupta A, Ingole NS, Lazdins-Helds JK. Efficacy and tolerability of treatment with single doses of diethylcarbamazine (DEC) and DEC plus albendazole (ABZ) for three consecutive years in lymphatic filariasis: a field study in India. Parasitol Res 2017; 116:2683-2694. [PMID: 28785847 DOI: 10.1007/s00436-017-5577-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 07/28/2017] [Indexed: 11/29/2022]
Abstract
Lymphatic filariasis (LF) affects 73 countries, causes morbidity and impedes socioeconomic development. We had found no difference in safety and micro (Mf) and macro filarial action of single-dose diethylcarbamazine (DEC) and DEC + albendazole (ABZ) in an F01 study done in India (year 2000). There was a programmatic need to evaluate safety and efficacy of multiple annual treatments (F02). Subjects (155) from the F01 study, meeting inclusion-exclusion criteria, were enrolled in F02 and treated with further two annual doses of DEC or DEC + ABZ. Efficacy was evaluated for Mf positivity by peripheral smear (PS) and nucleopore (NP) filter, circulating filarial antigen (CFA) and filarial dance sign (FDS) positivity and Mf count at yearly follow-up. Safety was assessed for 5 days after drug administration. Total of 139 subjects evaluated for efficacy (69 DEC and 70 DEC + ABZ group). Mf positivity prevalence declined progressively by 95% (PS), 66% (NP), and 95% (PS) and 86% (NP); CFA positivity prevalence declined by 15% and 9%; FDS by 100% each; Mf count declined by 75.5 and 76.9% with three annual treatment of DEC and DEC + ABZ, respectively. Addition of ABZ did not show any advantage over DEC given as three annual rounds for LF. DEC and DEC + ABZ were well tolerated. There was no correlation between result of CFA and FDS, (both claimed to be indicative of adult worm). Analysis of published studies and our data indicate that macrofilaricidal effect of DEC/DEC + ABZ may be seen in children and not adults, with three or more annual dosing.
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Affiliation(s)
- Nilima A Kshirsagar
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India. .,National Chair Clinical Pharmacology, ICMR Govt. of India, National Institute for Research in Reproductive Health (NIRRH), J. M. Street, Parel, Mumbai, 400012, India.
| | - N J Gogtay
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India
| | - B S Garg
- Department of Community Medicine, Mahatma Gandhi Institute of Medical Sciences, Wardha, 442102, India
| | - P R Deshmukh
- Department of Community Medicine, Mahatma Gandhi Institute of Medical Sciences, Wardha, 442102, India
| | - D D Rajgor
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India
| | - V S Kadam
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India
| | - P A Thakur
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India
| | - A Gupta
- Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, New MS Building, 1st Floor, Parel, Mumbai, 400012, India
| | - N S Ingole
- Department of Pathology, Mahatma Gandhi Institute of Medical Sciences, Wardha, 442102, India
| | - J K Lazdins-Helds
- World Health Organization (WHO), Special Program for Research and Training in Tropical Diseases, Product Research and Development, 20 Avenue Appia, Geneva 27, 1211, Geneva, CH, Switzerland
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Detecting infection hotspots: Modeling the surveillance challenge for elimination of lymphatic filariasis. PLoS Negl Trop Dis 2017; 11:e0005610. [PMID: 28542274 PMCID: PMC5453617 DOI: 10.1371/journal.pntd.0005610] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 06/01/2017] [Accepted: 04/28/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND During the past 20 years, enormous efforts have been expended globally to eliminate lymphatic filariasis (LF) through mass drug administration (MDA). However, small endemic foci (microfoci) of LF may threaten the presumed inevitable decline of infections after MDA cessation. We conducted microsimulation modeling to assess the ability of different types of surveillance to identify microfoci in these settings. METHODS Five or ten microfoci of radius 1, 2, or 3 km with infection marker prevalence (intensity) of 3, 6, or 10 times background prevalence were placed in spatial simulations, run in R Version 3.2. Diagnostic tests included microfilaremia, immunochromatographic test (ICT), and Wb123 ELISA. Population size was fixed at 360,000 in a 60 x 60 km area; demographics were based on literature for Sub-Saharan African populations. Background ICT prevalence in 6-7 year olds was anchored at 1.0%, and the prevalence in the remaining population was adjusted by age. Adults≥18 years, women aged 15-40 years (WCBA), children aged 6-7 years, or children≤5 years were sampled. Cluster (CS), simple random sampling (SRS), and TAS-like sampling were simulated, with follow-up testing of the nearest 20, 100, or 500 persons around each infection-marker-positive person. A threshold number of positive persons in follow-up testing indicated a suspected microfocus. Suspected microfoci identified during surveillance and actual microfoci in the simulation were compared to obtain a predictive value positive (PVP). Each parameter set was referred to as a protocol. Protocols were scored by efficiency, defined as the most microfoci identified, the fewest persons requiring primary and follow-up testing, and the highest PVP. Negative binomial regression was used to estimate aggregate effects of different variables on efficiency metrics. RESULTS All variables were significantly associated with efficiency metrics. Additional follow-up tests beyond 20 did not greatly increase the number of microfoci detected, but significantly negatively impacted efficiency. Of 3,402 protocols evaluated, 384 (11.3%) identified all five microfoci (PVP 3.4-100.0%) and required testing 0.73-35.6% of the population. All used SRS and 378 (98.4%) only identified all five microfoci if they were 2-3 km diameter or high-intensity (6x or 10x); 374 (97.4%) required ICT or Wb123 testing to identify all five microfoci, and 281 (73.0%) required sampling adults or WCBA. The most efficient CS protocols identified two (40%) microfoci. After limiting to protocols with 1-km radius microfoci of 3x intensity (n = 378), eight identified all five microfoci; all used SRS and ICT and required testing 31.2-33.3% of the population. The most efficient CS and TAS-like protocols as well as those using microfilaremia testing identified only one (20%) microfocus when they were limited to 1-km radius and 3x intensity. CONCLUSION In this model, SRS, ICT, and sampling of adults maximized microfocus detection efficiency. Follow-up sampling of more persons did not necessarily increase protocol efficiency. Current approaches towards surveillance, including TAS, may not detect small, low-intensity LF microfoci that could remain after cessation of MDA. The model provides many surveillance protocols that can be selected for optimal outcomes.
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Pullan RL, Sturrock HJW, Soares Magalhães RJ, Clements ACA, Brooker SJ. Spatial parasite ecology and epidemiology: a review of methods and applications. Parasitology 2012; 139:1870-87. [PMID: 23036435 PMCID: PMC3526959 DOI: 10.1017/s0031182012000698] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 03/11/2012] [Accepted: 04/03/2012] [Indexed: 12/21/2022]
Abstract
The distributions of parasitic diseases are determined by complex factors, including many that are distributed in space. A variety of statistical methods are now readily accessible to researchers providing opportunities for describing and ultimately understanding and predicting spatial distributions. This review provides an overview of the spatial statistical methods available to parasitologists, ecologists and epidemiologists and discusses how such methods have yielded new insights into the ecology and epidemiology of infection and disease. The review is structured according to the three major branches of spatial statistics: continuous spatial variation; discrete spatial variation; and spatial point processes.
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Swaminathan S, Perumal V, Adinarayanan S, Kaliannagounder K, Rengachari R, Purushothaman J. Epidemiological assessment of eight rounds of mass drug administration for lymphatic filariasis in India: implications for monitoring and evaluation. PLoS Negl Trop Dis 2012; 6:e1926. [PMID: 23209865 PMCID: PMC3510097 DOI: 10.1371/journal.pntd.0001926] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 10/14/2012] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Monitoring and evaluation guidelines of the programme to eliminate lymphatic filariasis require impact assessments in at least one sentinel and one spot-check site in each implementation unit (IU). Transmission assessment surveys (TAS) that assess antigenaemia (Ag) in children in IUs that have completed at least five rounds of mass drug administration (MDA) each with >65% coverage and with microfilaria (Mf) levels <1% in the monitored sites form the basis for stopping the MDA. Despite its rigour, this multi-step process is likely to miss sites with transmission potential ('hotspots') and its statistical assumptions for sampling and threshold levels for decision-making have not been validated. We addressed these issues in a large-scale epidemiological study in two primary health centres in Thanjavur district, India, endemic for bancroftian filariasis that had undergone eight rounds of MDA. METHODOLOGY/PRINCIPAL FINDINGS The prevalence and intensity of Mf (per 60 µl blood) were 0.2% and 0.004 respectively in the survey that covered >70% of 50,363 population. The corresponding values for Ag were 2.3% and 17.3 Ag-units respectively. Ag-prevalence ranged from 0.7 to 0.9%, in children (2-10 years) and 2.7 to 3.0% in adults. Although the Mf-levels in the survey and the sentinel/spot check sites were <1% and Ag-level was <2% in children, we identified 7 "residual" (Mf-prevalence ≥ 1%, irrespective of Ag-status in children) and 17 "transmission" (at least one Ag-positive child born during the MDA period) hotspots. Antigenaemic persons were clustered both at household and site levels. We identified an Ag-prevalence of ~1% in children (equivalent to 0.4% community Mf-prevalence) as a possible threshold value for stopping MDA. CONCLUSIONS/SIGNIFICANCE Existence of 'hotspots' and spatial clustering of infections in the study area indicate the need for developing good surveillance strategies for detecting 'hotspots', adopting evidence-based sampling strategies and evaluation unit size for TAS.
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Affiliation(s)
- Subramanian Swaminathan
- Vector Control Research Centre, Indian Council of Medical Research, Indira Nagar, Pondicherry, India.
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Drexler N, Washington CH, Lovegrove M, Grady C, Milord MD, Streit T, Lammie P. Secondary mapping of lymphatic filariasis in Haiti-definition of transmission foci in low-prevalence settings. PLoS Negl Trop Dis 2012; 6:e1807. [PMID: 23071849 PMCID: PMC3469481 DOI: 10.1371/journal.pntd.0001807] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2012] [Accepted: 07/19/2012] [Indexed: 11/24/2022] Open
Abstract
To eliminate Lymphatic filariasis (LF) as a public health problem, the World Health Organization (WHO) recommends that any area with infection prevalence greater than or equal to 1% (denoted by presence of microfilaremia or antigenemia) should receive mass drug administration (MDA) of antifilarial drugs for at least five consecutive rounds. Areas of low-antigen prevalence (< 1%) are thought to pose little risk for continued transmission of LF. Five low-antigen prevalence communes in Haiti, characterized as part of a national survey, were further assessed for transmission in this study. An initial evaluation of schoolchildren was performed in each commune to identify antigen-positive children who served as index cases for subsequent community surveys conducted among households neighboring the index cases. Global positioning system (GPS) coordinates and immunochromatographic tests (ICT) for filarial antigenemia were collected on approximately 1,600 persons of all ages in the five communes. The relationship between antigen-positive cases in the community and distance from index cases was evaluated using multivariate regression techniques and analyses of spatial clustering. Community surveys demonstrated higher antigen prevalence in three of the five communes than was observed in the original mapping survey; autochthonous cases were found in the same three communes. Regression techniques identified a significantly increased likelihood of being antigen-positive when living within 20 meters of index cases when controlling for age, gender, and commune. Spatial clustering of antigen-positive cases was observed in some, but not all communes. Our results suggest that localized transmission was present even in low-prevalence settings and suggest that better surveillance methods may be needed to detect microfoci of LF transmission.
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Affiliation(s)
- Naomi Drexler
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
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Application of the Filariasis CELISA Antifilarial IgG(4) Antibody Assay in Surveillance in Lymphatic Filariasis Elimination Programmes in the South Pacific. J Trop Med 2011; 2011:492023. [PMID: 21961018 PMCID: PMC3180782 DOI: 10.1155/2011/492023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 07/21/2011] [Indexed: 11/17/2022] Open
Abstract
Elimination of lymphatic filariasis (LF) in the Pacific Island Countries and Territories (PICT) has been defined as <0.1% circulating filarial antigen (CFA) prevalence in children born after the implementation of successful mass drug administrations (MDAs). This research assessed the feasibility of CFA and antibody testing in three countries; Tonga, Vanuatu, and Samoa. Transmission is interrupted in Vanuatu and Tonga as evidenced by no CFA positive children and a low antibody prevalence and titre. Transmission is ongoing in Samoa with microfilaraemic (Mf) and CFA positive children and a high antibody prevalence and titre. Furthermore, areas of transmission were identified with Mf positive adults, but no CFA positive children. These areas had a high antibody prevalence in children. In conclusion, CFA testing in children alone was not useful for identifying areas of residual endemicity in Samoa. Thus, it would be beneficial to include antibody serology in the PICT surveillance strategy.
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Wamae CN, Njenga SM, Ngugi BM, Mbui J, Njaanake HK. Evaluation of effectiveness of diethylcarbamazine/albendazole combination in reduction of Wuchereria bancrofti infection using multiple infection parameters. Acta Trop 2011; 120 Suppl 1:S33-8. [PMID: 20933491 DOI: 10.1016/j.actatropica.2010.09.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 06/24/2010] [Accepted: 09/17/2010] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To evaluate the effect of multiple rounds of annual single dose of DEC (6 mg/kg) or albendazole (400mg) given alone or in combination on Wuchereria bancrofti microfilaraemia, anti-filarial IgG1 and IgG4 and antigenaemia. METHODS A total of 170 participants were randomly assigned to albendazole (n = 62), DEC (n = 54), and DEC plus albendazole (DEC/ALB) combination (n = 54). Blood samples were collected at pre-treatment in 1998, at 1 week and 6 months after the first treatment and thereafter before subsequent treatments in 1999 and 2000. Effects of treatment on W. bancrofti infection were determined by changes in levels of microfilaraemia, antifilarial antibodies and circulating filarial antigen. RESULTS Comparison of geometric mean microfilariae intensities between DEC/ALB combination and DEC or albendazole single therapy groups after two rounds of annual treatment and 24 months follow-up showed that combination therapy resulted in a greater reduction of microfilaraemia than single therapy with either albendazole (p < 0.001) or DEC alone (p = 0.146). The overall levels of anti-filarial antibodies decreased significantly (p = 0.028 for IgG1 and p < 0.043 for IgG4) in all treatment groups at 24 months follow-up. Additionally, overall reduction in geometric mean circulating filarial antigen levels at 24 months was 44%, 60% and 85% for albendazole, DEC and DEC/ALB groups, respectively. CONCLUSIONS These study findings suggest that albendazole improved efficacy of DEC and mass administration of a combination of the two drugs would therefore enhance the interruption of transmission of W. bancrofti in endemic areas. This information has important implications for the ongoing Global Program for Elimination of Lymphatic Filariasis.
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Affiliation(s)
- C N Wamae
- Kenya Medical Research Institute, PO Box 54840-00200, Nairobi, Kenya.
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First evidence of spatial clustering of lymphatic filariasis in an Aedes polynesiensis endemic area. Acta Trop 2011; 120 Suppl 1:S39-47. [PMID: 21172296 DOI: 10.1016/j.actatropica.2010.12.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 11/24/2022]
Abstract
Successful elimination of lymphatic filariasis (LF) requires accurate identification of residual foci of transmission and stringent surveillance strategies to combat potential resurgence. This is challenging in areas where the day-biting Aedes polynesiensis is endemic, such as Samoa, since in previous studies no geographical clustering of infection has been demonstrated. Another challenge for this low prevalence phase is the choice of diagnostic assay as testing for circulating filarial antigen (CFA) or microfilariae (Mf) alone may not have adequate sensitivity. This could be solved by using the commercially available filariasis Cellabs enzyme linked immunosorbent assay (CELISA) to measure antibody. In the current study five Samoan villages were chosen based on previous epidemiological assessments to represent a range of infection prevalences. CFA, Mf, and antibody levels in children ≤ 10 years had been recorded and results linked to household of residence and/or primary school of attendance. To ascertain the location of exposure, two scenarios based on potential foci of transmission around communities and schools were explored. Both scenarios revealed significant spatial clusters of households with infected individuals and a relationship to antibody positive children when they were included in the spatial analysis. Fasitoo-Tai had the highest LF prevalence and largest geographical spatial clusters for both scenarios. In Falefa, spatial clusters were detected only for the primary school scenario. In Tafua, which spanned an area of 19.5 km(2), no spatial clusters were detected. Lastly, in Siufaga, the village with the lowest LF prevalence, significant clustering of infected individuals was observed and, for the primary school scenario, this was geographically related to exposure. These promising findings are the first published evidence of spatial clustering of LF in a day-biting Ae. polynesiensis endemic area.
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Agrawal VK, Sashindran VK. Lymphatic Filariasis in India : Problems, Challenges and New Initiatives. Med J Armed Forces India 2011; 62:359-62. [PMID: 27688542 DOI: 10.1016/s0377-1237(06)80109-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 02/28/2006] [Indexed: 12/01/2022] Open
Abstract
Filariasis is a major public health problem in India and inspite of existence of the National Filaria Control Programme since 1955, currently there may be up to 31 million microfilaraemics, 23 million cases of symptomatic filariasis, and about 473 million individuals potentially at risk of infection. Over the last 10 years advances have led to new diagnostic/ treatment tools and control strategies for filariasis. The new control strategy aims at transmission control through mass treatment and at disease control through individual patient management. As a signatory to 50(th) World Health Assembly resolution on global elimination of lymphatic filariasis in 1997, revised filariasis control program was launched in India in 13 districts in seven endemic states where mass drug administration was undertaken. Single dose mass administration annually in combination with other techniques has already eliminated lymphatic filariasis from Japan, Taiwan, South Korea and Solomon Islands and markedly reduced the transmission in China. Very high treatment coverage (probably > 85%) is required to achieve interruption of transmission and elimination in India. Hence, there is an urgent need for effective drug delivery strategies that are adapted to regional differences. This requires powerful advocacy tools and strategies as well as procedures for monitoring and evaluating the impact of elimination programme.
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Affiliation(s)
- V K Agrawal
- Reader, Department of Community Medicine, AFMC, Pune 410040
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Kumar P, Prajapati P, Saxena D, Kavishwar AB, Kurian G. An evaluation of coverage and compliance of mass drug administration 2006 for elimination of lymphatic filariasis in endemic areas of gujarat. Indian J Community Med 2011; 33:38-42. [PMID: 19966995 PMCID: PMC2782227 DOI: 10.4103/0970-0218.39242] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Accepted: 12/16/2007] [Indexed: 11/15/2022] Open
Abstract
Background: Mass drug administration (MDA) means once-in-a-year administration of diethyl carbamazine (DEC) tablet to all people (excluding children under 2 years, pregnant women and severely ill persons) in identified endemic areas. It aims at cessation of transmission of lymphatic filariasis. Objective: What has been the coverage and compliance of MDA in Gujarat during the campaign in December 2006? Study Design: Cross-sectional population based house-to-house visit. Setting: Urban and rural areas in Gujarat identified as endemic for filariasis where MDA 2006 was undertaken. Study Variables: Exploratory - Rural and urban districts; Outcome - coverage, compliance, actual coverage, side effects. Analysis: Percentage and proportions. Results: Twenty-six clusters, each comprising 32 households from six endemic districts, yielded an eligible population of 4164. The coverage rate was 85.2% with variation across different areas. The compliance with drug ingestion was 89% with a gap of 11% to be targeted by intensive IEC. The effective coverage (75.8%) was much below the target (85%). Side effects of DEC were minimum, transient and drug-specific. Overall coverage was marginally better in rural areas. The causes of poor coverage and compliance have been discussed and relevant suggestions have been made.
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Affiliation(s)
- Pradeep Kumar
- Department of Community Medicine, Government Medical College, Surat - 395 001, India
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Le Comber SC, Rossmo DK, Hassan AN, Fuller DO, Beier JC. Geographic profiling as a novel spatial tool for targeting infectious disease control. Int J Health Geogr 2011; 10:35. [PMID: 21592339 PMCID: PMC3123167 DOI: 10.1186/1476-072x-10-35] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 05/18/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Geographic profiling is a statistical tool originally developed in criminology to prioritise large lists of suspects in cases of serial crime. Here, we use two data sets--one historical and one modern--to show how it can be used to locate the sources of infectious disease. RESULTS First, we re-analyse data from a classic epidemiological study, the 1854 London cholera outbreak. Using 321 disease sites as input, we evaluate the locations of 13 neighbourhood water pumps. The Broad Street pump--the outbreak's source--ranks first, situated in the top 0.2% of the geoprofile. We extend our study with an analysis of reported malaria cases in Cairo, Egypt, using 139 disease case locations to rank 59 mosquitogenic local water sources, seven of which tested positive for the vector Anopheles sergentii. Geographic profiling ranks six of these seven sites in positions 1-6, all in the top 2% of the geoprofile. In both analyses the method outperformed other measures of spatial central tendency. CONCLUSIONS We suggest that geographic profiling could form a useful component of integrated control strategies relating to a wide variety of infectious diseases, since evidence-based targeting of interventions is more efficient, environmentally friendly and cost-effective than untargeted intervention.
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Affiliation(s)
- Steven C Le Comber
- Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, UK.
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Mirghani SE, Nour BYM, Bushra SM, Elhassan IM, Snow RW, Noor AM. The spatial-temporal clustering of Plasmodium falciparum infection over eleven years in Gezira State, The Sudan. Malar J 2010; 9:172. [PMID: 20565854 PMCID: PMC2903606 DOI: 10.1186/1475-2875-9-172] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 06/18/2010] [Indexed: 12/02/2022] Open
Abstract
Background Malaria infection and disease exhibit microgeographic heterogeneity which if predictable could have implications for designing small-area intervention. Here, the space-time clustering of Plasmodium falciparum infections using data from repeat cross-sectional surveys in Gezira State, a low transmission area in northern Sudan, is investigated. Methods Data from cross-sectional surveys undertaken in January each year from 1999-2009 in 88 villages in the Gezira state were assembled. During each survey, about a 100 children between the ages two to ten years were sampled to examine the presence of P. falciparum parasites. In 2009, all the villages were mapped using global positioning systems. Cluster level data were analysed for spatial-only and space-time clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic. Results Over the study period, 96,022 malaria slide examinations were undertaken and the P. falciparum prevalence was 8.6% in 1999 and by 2009 this had reduced to 1.6%. The cluster analysis showed the presence of one significant spatial-only cluster in each survey year and one significant space-time cluster over the whole study period. The primary spatial-only clusters in 10/11 years were either contained within or overlapped with the primary space-time cluster. Conclusion The results of the study confirm the generally low malaria transmission in the state of Gezira and the presence of spatial and space-time clusters concentrated around a specific area in the south of the state. Improved surveillance data that allows for the analysis of seasonality, age and other risk factors need to be collected to design effective small area interventions as Gezira state targets malaria elimination.
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Affiliation(s)
- Samia E Mirghani
- Malaria Public Health and Epidemiology Group, Centre for Geographic Medicine, KEMRI - University of Oxford - Wellcome Trust Collaborative Programme, Kenyatta National Hospital Grounds, Nairobi, Kenya
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Boyd A, Won KY, McClintock SK, Donovan CV, Laney SJ, Williams SA, Pilotte N, Streit TG, Beau de Rochars MVE, Lammie PJ. A community-based study of factors associated with continuing transmission of lymphatic filariasis in Leogane, Haiti. PLoS Negl Trop Dis 2010; 4:e640. [PMID: 20351776 PMCID: PMC2843627 DOI: 10.1371/journal.pntd.0000640] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 02/04/2010] [Indexed: 11/30/2022] Open
Abstract
Seven rounds of mass drug administration (MDA) have been administered in Leogane, Haiti, an area hyperendemic for lymphatic filariasis (LF). Sentinel site surveys showed that the prevalence of microfilaremia was reduced to <1% from levels as high as 15.5%, suggesting that transmission had been reduced. A separate 30-cluster survey of 2- to 4-year-old children was conducted to determine if MDA interrupted transmission. Antigen and antifilarial antibody prevalence were 14.3% and 19.7%, respectively. Follow-up surveys were done in 6 villages, including those selected for the cluster survey, to assess risk factors related to continued LF transmission and to pinpoint hotspots of transmission. One hundred houses were mapped in each village using GPS-enabled PDAs, and then 30 houses and 10 alternates were chosen for testing. All individuals in selected houses were asked to participate in a short survey about participation in MDA, history of residence in Leogane and general knowledge of LF. Survey teams returned to the houses at night to collect blood for antigen testing, microfilaremia and Bm14 antibody testing and collected mosquitoes from these communities in parallel. Antigen prevalence was highly variable among the 6 villages, with the highest being 38.2% (Dampus) and the lowest being 2.9% (Corail Lemaire); overall antigen prevalence was 18.5%. Initial cluster surveys of 2- to 4-year-old children were not related to community antigen prevalence. Nearest neighbor analysis found evidence of clustering of infection suggesting that LF infection was focal in distribution. Antigen prevalence among individuals who were systematically noncompliant with the MDAs, i.e. they had never participated, was significantly higher than among compliant individuals (p<0.05). A logistic regression model found that of the factors examined for association with infection, only noncompliance was significantly associated with infection. Thus, continuing transmission of LF seems to be linked to rates of systematic noncompliance. Lymphatic filariasis (LF) is a mosquito-borne parasitic disease that affects an estimated 120 million people worldwide with over 1 billion at risk for infection. LF is considered to be a leading cause of permanent disability worldwide due to the clinical manifestations of the disease. A global effort was established to eliminate LF by 2020 through interruption of transmission by annual mass administrations of anti-parasitic drugs. In Leogane, Haiti, seven rounds of drug administration have been administered and, though infection levels have dropped, transmission has not been interrupted. In this study the authors examined factors that could contribute to continuing transmission of LF in Haiti. Ongoing transmission was confirmed by high infection rates among young children. Infection was found to cluster at the household level within communities. The factor most associated with this transmission was systematic noncompliance with drug administration (i.e. never taking the medication). While increased health education and awareness campaigns may improve noncompliance, new tools and approaches may be needed to stop transmission of LF in Haiti. Understanding obstacles and solutions from the Haiti program could aid elimination programs in other countries.
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Affiliation(s)
- Alexis Boyd
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Kimberly Y. Won
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
| | - Shannon K. McClintock
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Catherine V. Donovan
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Sandra J. Laney
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Steven A. Williams
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Nils Pilotte
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Thomas G. Streit
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | | | - Patrick J. Lammie
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
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Abstract
The spatial scan statistic is one of the main epidemiological tools to test for the presence of disease clusters in a geographical region. While the statistical significance of the most likely cluster is correctly assessed using the model assumptions, secondary clusters tend to have conservatively highP-values. In this paper, we propose a sequential version of the spatial scan statistic to adjust for the presence of other clusters in the study region. The procedure removes the effect due to the more likely clusters on less significant clusters by sequential deletion of the previously detected clusters. Using the Northeastern United States geography and population in a simulation study, we calculated the type I error probability and the power of this sequential test under different alternative models concerning the locations and sizes of the true clusters. The results show that the type I error probability of our method is close to the nominalαlevel and that for secondary clusters its power is higher than the standard unadjusted scan statistic.
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Huppatz C, Durrheim D, Lammie P, Kelly P, Melrose W. Eliminating lymphatic filariasis--the surveillance challenge. Trop Med Int Health 2008; 13:292-4. [PMID: 18397392 DOI: 10.1111/j.1365-3156.2008.02002.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Gunawardena GSA, Ismail MM, Bradley MH, Karunaweera ND. Impact of the 2004 mass drug administration for the control of lymphatic filariasis, in urban and rural areas of the Western province of Sri Lanka. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2007; 101:335-41. [PMID: 17524248 DOI: 10.1179/136485907x176364] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Lymphatic filariasis is targeted to be eliminated globally, at least as a public-health problem, by 2020. The comprehensive strategy for achieving this goal includes the interruption of the transmission of the causative parasites, by drastically reducing the prevalences of microfilaraemia in at-risk communities. In a descriptive, comparative, cross-sectional and community-based study, the impact of the 2004 mass drug administration (MDA) on filarial infection, in selected areas of the Western province of Sri Lanka, has now been assessed 1-2 and 11 months after the administration of the diethylcarbamazine-albendazole combination employed. Using the cluster-sampling method, urban study populations were selected in the Colombo districts and rural ones were selected in the Gampaha district. After obtaining informed written consent, 2 ml venous blood were collected, between 20.00 and 24.00 hours, from each subject. Personal details and drug compliance in the 2004 MDA were recorded. The samples of 'night' blood were checked for microfilariae, using membrane filtration, and for filarial antigenaemia, using commercial (NOW) immunochromatographic test kits. Eighty-four (4.10%) of the 2034 subjects examined 1-2 months after the 2004 MDA but only four (0.20%) of the 1974 subjects checked 11 months after the MDA were found antigenaemic and/or microfilaraemic (P<0.001). Between the two follow-ups, the overall prevalences of both antigenaemia (4.03% v. 0.15%; P<0.001) and microfilaraemia (0.20% v. 0.05%; P=0.38) fell, although only the reduction in antigenaemia was statistically significant. The prevalence of infection (as indicated by antigenaemia and/or microfilaraemia) fell significantly within each of the two study districts (P<0.001). Although, when the prevalence of infection was high, drug compliance appeared to be an important determinant of the reduction of antigenaemia (P=0.04), the 20% difference in compliance between urban and rural areas had no apparent effect on the corresponding prevalences of infection recorded at either follow-up.
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Affiliation(s)
- G S A Gunawardena
- Department of Parasitology, Faculty of Medicine, University of Colombo, PO Box 271, Kynsey Road, Colombo 8, Sri Lanka.
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Rolka H, Burkom H, Cooper GF, Kulldorff M, Madigan D, Wong WK. Issues in applied statistics for public health bioterrorism surveillance using multiple data streams: research needs. Stat Med 2007; 26:1834-56. [PMID: 17221940 DOI: 10.1002/sim.2793] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The objective of this report is to provide a basis to inform decisions about priorities for developing statistical research initiatives in the field of public health surveillance for emerging threats. Rapid information system advances have created a vast opportunity of secondary data sources for information to enhance the situational and health status awareness of populations. While the field of medical informatics and initiatives to standardize healthcare-seeking encounter records continue accelerating, it is necessary to adapt analytic and statistical methodologies to mature in sync with sibling information science technologies. One major right-of-passage for statistical inference is to advance the optimal application of analytic methodologies for using multiple data streams in detecting and characterizing public health population events of importance. This report first describes the problem in general and the data context, then delineates more specifically the practical nature of the problem and the related issues. Approaches currently applied to data with time-series, statistical process control and traditional inference concepts are described with examples in the section on Statistics and the Role of the Analytic Surveillance Data Monitor. These are the techniques that are providing substance to surveillance professionals and enabling use of multiple data streams. The next section describes use of a more complex approach that takes temporal as well as spatial dimensions into consideration for detection and situational awareness regarding event distributions. The space-time statistic has successfully been used to detect and track public health events of interest. Important research questions which are summarized at the end of this report are described in more detail with respect to the methodological application in the respective sections. This was thought to help elucidate the research requirements as summarized later in the report. Following the description of the space-time scan statistical application; this report extends to a less traditional area of promise given what has been observed in recent application of analytic methods. Bayesian networks (BNs) represent a conceptual step with advantages of flexibility for the public health surveillance community. Progression from traditional to the more extending statistical concepts in the context of the dynamic status quo of responsibility and challenge, leads to a conclusion consisting of categorical research needs. The report is structured by design to inform judgment about how to build on practical systems to achieve better analytic outcomes for public health surveillance. There are references to research issues throughout the sections with a summarization at the end, which also includes items previously unmentioned in the report.
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Affiliation(s)
- Henry Rolka
- Centers for Disease Control and Prevention (CDC), Division of Emergency Preparedness and Response, National Center for Public Health Informatics, 1600 Clifton Rd., NE. MS D45, Atlanta, GA 30333, USA.
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Duczmal L, Kulldorff M, Huang L. Evaluation of Spatial Scan Statistics for Irregularly Shaped Clusters. J Comput Graph Stat 2006. [DOI: 10.1198/106186006x112396] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lammie PJ, Weil G, Noordin R, Kaliraj P, Steel C, Goodman D, Lakshmikanthan VB, Ottesen E. Recombinant antigen-based antibody assays for the diagnosis and surveillance of lymphatic filariasis - a multicenter trial. FILARIA JOURNAL 2004; 3:9. [PMID: 15347425 PMCID: PMC519021 DOI: 10.1186/1475-2883-3-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 09/03/2004] [Indexed: 11/10/2022]
Abstract
The development of antifilarial antibody responses is a characteristic feature of infection with filarial parasites. It should be possible to exploit this fact to develop tools to monitor the progress of the global program to eliminate lymphatic filariasis (LF); however, assays based on parasite extracts suffer from a number of limitations, including the paucity of parasite material, the difficulty of assay standardization and problems with assay specificity. In principle, assays based on recombinant filarial antigens should address these limitations and provide useful tools for diagnosis and surveillance of LF. The present multicenter study was designed to compare the performance of antibody assays for filariasis based on recombinant antigens Bm14, WbSXP, and BmR1. Coded serum specimens were distributed to five participating laboratories where assays for each antigen were conducted in parallel. Assays based on Bm14, WbSXP, or BmR1 demonstrated good sensitivity (>90%) for field use and none of the assays demonstrated reactivity with specimens from persons with non-filarial helminth infections. Limitations of the assays are discussed. Well-designed field studies are now needed to assess sampling methodology and the application of antibody testing to the monitoring and surveillance of LF elimination programs.
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Affiliation(s)
- Patrick J Lammie
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, MS-F13, 4770 Buford Highway, Atlanta, Georgia, 30341, USA
| | - Gary Weil
- Infectious Diseases Division, Campus Box 8051, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Rahmah Noordin
- Institute for Research in Molecular Medicine and School of Medical Sciences, Universiti Sains Malaysia, Malaysia
| | - Perumal Kaliraj
- Centre for Biotechnology, Anna University, Chennai – 600 025, India
| | - Cathy Steel
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - David Goodman
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, MS-F13, 4770 Buford Highway, Atlanta, Georgia, 30341, USA
| | | | - Eric Ottesen
- Emory University Lymphatic Filariasis Support Center, 1518 Clifton Road, Atlanta, Georgia, 30322, USA
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