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Ma L, Nouhoum D, Wang W, Zhang Z, Hou X, Yu X, Deng W, Guan J, Huang S, Wu X. A case of severe hookworm infection. ZHONG NAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF CENTRAL SOUTH UNIVERSITY. MEDICAL SCIENCES 2022; 47:814-822. [PMID: 35837783 PMCID: PMC10930016 DOI: 10.11817/j.issn.1672-7347.2022.210593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Indexed: 06/15/2023]
Abstract
With the improvement of sanitation, the infection rate of hookworm is greatly reduced and the severe infected case is rarely reported. Combined morphological and molecular biological examinations, a severe hookworm infection patient was diagnosed in Department of Laboratorial Examination, Quanzhou First Affiliated Hospital of Fujian Medical University. The morphological methods such as direct fecal smear microscopy, saturated brine flotation and hookworm larvae culture methods were used to identify the eggs and larvae from stool samples of the patient. There were a large number of hookworm eggs in patient's stool samples, and the average count was 60 840 per gram by modified Kato method, which belonged to severe hookworm infection. Meanwhile, to distinguish the hookworm species, the semi-nested RT-PCR assay was employed to detect hookworm internal transcribed spacer series from eggs in patient's stool samples, and the result showed that the hookworm species was confirmed to be Necator americanus.
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Affiliation(s)
- Linghui Ma
- Department of Laboratorial Examination, Quanzhou First Affiliated Hospital of Fujian Medical University, Quanzhou Fujian 362000.
| | - Dibo Nouhoum
- Department of Prevention and Control, Hunan Institute of Schistosomiasis Control, Yueyang Hunan 414021
| | - Wanni Wang
- Department of Laboratorial Examination, Quanzhou First Affiliated Hospital of Fujian Medical University, Quanzhou Fujian 362000
| | - Zhishan Zhang
- Department of Laboratorial Examination, Quanzhou First Affiliated Hospital of Fujian Medical University, Quanzhou Fujian 362000
| | - Xunya Hou
- Department of Prevention and Control, Hunan Institute of Schistosomiasis Control, Yueyang Hunan 414021
- Key Laboratory of Immunization and Transmission Control of Schistosomiasis in Hunan Province, Yueyang Hunan 414125
| | - Xinling Yu
- Department of Prevention and Control, Hunan Institute of Schistosomiasis Control, Yueyang Hunan 414021
- Key Laboratory of Immunization and Transmission Control of Schistosomiasis in Hunan Province, Yueyang Hunan 414125
| | - Weicheng Deng
- Department of Prevention and Control, Hunan Institute of Schistosomiasis Control, Yueyang Hunan 414021
- Key Laboratory of Immunization and Transmission Control of Schistosomiasis in Hunan Province, Yueyang Hunan 414125
| | - Jie Guan
- Department of Pathology, Hunan Aerospace Hospital, Changsha 410006
| | - Shuaiqin Huang
- Key Laboratory of Immunization and Transmission Control of Schistosomiasis in Hunan Province, Yueyang Hunan 414125.
- Departmentof Parasitology, School of Basic Medical Sciences, Central South University, Changsha 410078, China.
| | - Xiang Wu
- Key Laboratory of Immunization and Transmission Control of Schistosomiasis in Hunan Province, Yueyang Hunan 414125.
- Departmentof Parasitology, School of Basic Medical Sciences, Central South University, Changsha 410078, China.
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Kaliappan S, Ramanujam K, Manuel M, Farzana J, Janagaraj V, Laxmanan S, Muliyil J, Sarkar R, Kang G, Walson J, Ajjampur S. Soil-transmitted helminth infections after mass drug administration for lymphatic filariasis in rural southern India. Trop Med Int Health 2021; 27:81-91. [PMID: 34704320 DOI: 10.1111/tmi.13697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES Targeted deworming is the current strategy for control of morbidity associated with soil-transmitted helminths (STH) among at-risk populations: preschool-aged children, school-aged children and women of childbearing age. We report the prevalence and intensity of STH in a district after lymphatic filariasis (LF) mass drug administration (MDA) in southern India where albendazole was co-administered from 2001. METHODS Children aged 2 to 15 years and adults (defined as ≥15 years) in a rural administrative block of Tamil Nadu were recruited using a probability proportional to size method. Stool samples were screened and eggs per gram (EPG) determined by Kato-Katz method. Multilevel logistic regression (MLR) and multilevel negative binomial regression (MNBR) analyses were used to identify factors associated with infection and intensity, respectively. RESULTS Of 862 participants who provided samples, 60 (7.0%; 95% confidence interval (CI): 5.3-8.7) were positive for STH with a predominance of hookworm infections (n = 57, 6.6%; 95% CI: 5.0-8.3). Increasing age (odds ratio (OR): 1.09; 95% CI: 1.04-1.15) and regular usage of the toilet (OR: 0.32; 95% CI: 0.12-0.88) were independently associated with hookworm infection and age was significantly associated with increasing intensity of hookworm infection (infection intensity ratio (IIR): 1.28; 95% CI: 1.19-1.37). A brief review of STH prevalence in endemic settings before and after the stoppage of LF MDA indicated that, in most settings, a substantial reduction in STH prevalence is seen. CONCLUSION Community-wide MDA in all age groups in these post-LF MDA districts with low prevalence and light intensity infections could result in transmission interruption of STH.
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Affiliation(s)
- Saravanakumar Kaliappan
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Karthikeyan Ramanujam
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Malathi Manuel
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Jasmine Farzana
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Venkateshprabhu Janagaraj
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Selvi Laxmanan
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Jayaprakash Muliyil
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Rajiv Sarkar
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Gagandeep Kang
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
| | - Judd Walson
- Departments of Global Health, Medicine (Infectious Disease), Paediatrics & Epidemiology, University of Washington, Seattle, Washington, USA
| | - Sitara Ajjampur
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College Vellore, Tamil Nadu, India
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Coffeng LE, Levecke B, Hattendorf J, Walker M, Denwood MJ. Survey Design to Monitor Drug Efficacy for the Control of Soil-Transmitted Helminthiasis and Schistosomiasis. Clin Infect Dis 2021; 72:S195-S202. [PMID: 33906226 PMCID: PMC8201552 DOI: 10.1093/cid/ciab196] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Background Control of soil-transmitted helminthiasis and schistosomiasis relies heavily on regular preventive chemotherapy. Monitoring drug efficacy is crucial to provide early warning of treatment failures. The World Health Organization (WHO) recommends a survey design in which only egg-positive individuals are retested after treatment. Although this practice makes more efficient use of resources, it may lead to biased drug efficacy estimates. Methods We performed a simulation study to assess the potential for bias when evaluating drug efficacy using the World Health Organization–recommended survey design, and to identify alternative designs for evaluating drug efficacy that are less affected by bias. These designs were also based on selection of egg-positive individuals, but involve retesting them a second time at baseline and up to 2 times at follow-up. The utility of the different designs was compared fairly by constraining them to the same budget. Results The standard procedure of selecting egg-positive individuals can introduce a substantial positive bias in drug efficacy due to regression toward the mean, particularly when infection levels or drug efficacy are low. This bias was completely eliminated by using a second baseline sample, conditionally on the first sample being excluded from analysis. Precision of estimates can be improved by increasing the number of thick smears and/or samples per person at follow-up, despite fewer individuals being tested within the same budget. Conclusions We present optimized survey designs to monitor drug efficacy in field settings, which are highly relevant for sustained control of soil-transmitted helminths and schistosomiasis, as well as onchocerciasis and lymphatic filariasis.
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Affiliation(s)
- Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Bruno Levecke
- Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium
| | - Jan Hattendorf
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Martin Walker
- Department of Pathobiology and Population Sciences and London Centre for Neglected Tropical Disease Research, Royal Veterinary College , Hatfield, United Kingdom
| | - Matthew J Denwood
- Department of Veterinary and Animal Sciences, University of Copenhagen, Denmark
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Ajjampur SSR, Kaliappan SP, Halliday KE, Palanisamy G, Farzana J, Manuel M, Abraham D, Laxmanan S, Aruldas K, Rose A, Kennedy DS, Oswald WE, Pullan RL, Galagan SR, Ásbjörnsdóttir K, Anderson RM, Muliyil J, Sarkar R, Kang G, Walson JL. Epidemiology of soil transmitted helminths and risk analysis of hookworm infections in the community: Results from the DeWorm3 Trial in southern India. PLoS Negl Trop Dis 2021; 15:e0009338. [PMID: 33930024 PMCID: PMC8184002 DOI: 10.1371/journal.pntd.0009338] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 06/07/2021] [Accepted: 03/29/2021] [Indexed: 12/17/2022] Open
Abstract
Since 2015, India has coordinated the largest school-based deworming program globally, targeting soil-transmitted helminths (STH) in ~250 million children aged 1 to 19 years twice yearly. Despite substantial progress in reduction of morbidity associated with STH, reinfection rates in endemic communities remain high. We conducted a community based parasitological survey in Tamil Nadu as part of the DeWorm3 Project—a cluster-randomised trial evaluating the feasibility of interrupting STH transmission at three geographically distinct sites in Africa and Asia—allowing the estimation of STH prevalence and analysis of associated factors. In India, following a comprehensive census, enumerating 140,932 individuals in 36,536 households along with geospatial mapping of households, an age-stratified sample of individuals was recruited into a longitudinal monitoring cohort (December 2017-February 2018) to be followed for five years. At enrolment, a total of 6089 consenting individuals across 40 study clusters provided a single adequate stool sample for analysis using the Kato-Katz method, as well as answering a questionnaire covering individual and household level factors. The unweighted STH prevalence was 17.0% (95% confidence interval [95%CI]: 16.0–17.9%), increasing to 21.4% when weighted by age and cluster size. Hookworm was the predominant species, with a weighted infection prevalence of 21.0%, the majority of which (92.9%) were light intensity infections. Factors associated with hookworm infection were modelled using mixed-effects multilevel logistic regression for presence of infection and mixed-effects negative binomial regression for intensity. The prevalence of both Ascaris lumbricoides and Trichuris trichiura infections were rare (<1%) and risk factors were therefore not assessed. Increasing age (multivariable odds ratio [mOR] 21.4, 95%CI: 12.3–37.2, p<0.001 for adult age-groups versus pre-school children) and higher vegetation were associated with an increased odds of hookworm infection, whereas recent deworming (mOR 0.3, 95%CI: 0.2–0.5, p<0.001) and belonging to households with higher socioeconomic status (mOR 0.3, 95%CI: 0.2–0.5, p<0.001) and higher education level of the household head (mOR 0.4, 95%CI: 0.3–0.6, p<0.001) were associated with lower odds of hookworm infection in the multilevel model. The same factors were associated with intensity of infection, with the use of improved sanitation facilities also correlated to lower infection intensities (multivariable infection intensity ratio [mIIR] 0.6, 95%CI: 0.4–0.9, p<0.016). Our findings suggest that a community-based approach is required to address the high hookworm burden in adults in this setting. Socioeconomic, education and sanitation improvements alongside mass drug administration would likely accelerate the drive to elimination in these communities. Trial Registration:NCT03014167. Approximately 1 in 5 people in India are infected with soil transmitted helminths (STH), leading to anaemia and malnutrition. To tackle this large burden of infection, the government of India launched one of the world’s largest school-based deworming programs in 2015 aiming to deworm all pre-school and school-aged children between 1 to 19 years of age twice yearly on the National Deworming Days. Deworming programs, including those in India, are focused on pre-school aged children, school aged children and women of reproductive age group. However, prevailing environmental and socioeconomic conditions, including poor sanitation, can contribute to high rates of reinfection from untreated adults and children. The DeWorm3 Project is a cluster-randomised trial evaluating the feasibility of interrupting STH transmission with community wide deworming of all individuals aged one to 99 years of age or older. As part of the study, we conducted a parasitological survey in the Deworm3 trial site in rural Tamil Nadu. Here we present the factors associated with STH infection and burden in these communities.
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Affiliation(s)
- Sitara S. R. Ajjampur
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
- * E-mail:
| | | | - Katherine E. Halliday
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
- The DeWorm3 Project, University of Washington, Seattle, Washington, United States of America
| | - Gokila Palanisamy
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Jasmine Farzana
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Malathi Manuel
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Dilip Abraham
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Selvi Laxmanan
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Kumudha Aruldas
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Anuradha Rose
- Department of Community Medicine, Christian Medical College, Vellore, India
| | - David S. Kennedy
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - William E. Oswald
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Rachel L. Pullan
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Sean R. Galagan
- The DeWorm3 Project, University of Washington, Seattle, Washington, United States of America
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| | - Kristjana Ásbjörnsdóttir
- The DeWorm3 Project, University of Washington, Seattle, Washington, United States of America
- Department of Epidemiology, University of Washington, Seattle, Washington, United States of America
| | - Roy M. Anderson
- School of Public Health, Faculty of Medicine, Imperial College, London, United Kingdom
| | - Jayaprakash Muliyil
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Rajiv Sarkar
- Indian Institute of Public Health, Shillong, India
| | - Gagandeep Kang
- The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India
| | - Judd L. Walson
- The DeWorm3 Project, University of Washington, Seattle, Washington, United States of America
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
- Department of Medicine (Infectious Diseases) and Pediatrics, University of Washington, Seattle, Washington, United States of America
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Coffeng LE, Malizia V, Vegvari C, Cools P, Halliday KE, Levecke B, Mekonnen Z, Gichuki PM, Sayasone S, Sarkar R, Shaali A, Vlaminck J, Anderson RM, de Vlas SJ. Impact of Different Sampling Schemes for Decision Making in Soil-Transmitted Helminthiasis Control Programs. J Infect Dis 2021; 221:S531-S538. [PMID: 31829425 PMCID: PMC7289558 DOI: 10.1093/infdis/jiz535] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Starting and stopping preventive chemotherapy (PC) for soil-transmitted helminthiasis is typically based on the prevalence of infection as measured by Kato-Katz (KK) fecal smears. Kato-Katz-based egg counts can vary highly over repeated stool samples and smears. Consequentially, the sensitivity of KK-based surveys depends on the number of stool samples per person and the number of smears per sample. Given finite resources, collecting multiple samples and/or smears means screening fewer individuals, thereby lowering the statistical precision of prevalence estimates. Using population-level data from various epidemiological settings, we assessed the performance of different sampling schemes executed within the confines of the same budget. We recommend the use of single-slide KK for determining prevalence of moderate-to-heavy intensity infection and policy decisions for starting and continuing PC; more sensitive sampling schemes may be required for policy decisions involving stopping PC. Our findings highlight that guidelines should include specific guidance on sampling schemes.
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Affiliation(s)
- Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Veronica Malizia
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Carolin Vegvari
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Piet Cools
- Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Katherine E Halliday
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Bruno Levecke
- Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Zeleke Mekonnen
- Jimma University Institute of Health, Jimma University, Jimma, Ethiopia
| | - Paul M Gichuki
- Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya
| | - Somphou Sayasone
- Lao Tropical and Public Health Institute, Ministry of Health, Vientiane, Lao People's Democratic Republic
| | - Rajiv Sarkar
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Ame Shaali
- Laboratory Division, Public Health Laboratory-Ivo de Carneri, Chake Chake, United Republic of Tanzania
| | - Johnny Vlaminck
- Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Roy M Anderson
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Keller L, Palmeirim MS, Ame SM, Ali SM, Puchkov M, Huwyler J, Hattendorf J, Keiser J. Efficacy and Safety of Ascending Dosages of Moxidectin and Moxidectin-albendazole Against Trichuris trichiura in Adolescents: A Randomized Controlled Trial. Clin Infect Dis 2021; 70:1193-1201. [PMID: 31044235 DOI: 10.1093/cid/ciz326] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 04/22/2019] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Preventive chemotherapy is the main strategy to control soil-transmitted helminth (STH) infections. Albendazole and mebendazole are ubiquitously used, but they are not sufficiently effective against Trichuris trichiura. Moxidectin might be a useful addition to the small drug armamentarium. However, the optimal dosage of moxidectin alone and in combination with albendazole against T. trichiura and other STHs has not yet been determined. METHODS A Phase II, randomized, placebo-controlled, dose-finding trial was conducted in 2 secondary schools on Pemba Island, Tanzania. Using a computer-generated list, T. trichiura-infected adolescents were randomly assigned to 7 treatment arms: 8, 16, or 24 mg of moxidectin monotherapy; 8, 16, or 24 mg of moxidectin plus 400 mg of albendazole combination therapy; or placebo. The primary outcome was cure rate (CR) against T. trichiura, analyzed 13 to 20 days after treatment by quadruple Kato-Katz thick smears. RESULTS A total of 290 adolescents were enrolled (41 or 42 per arm). CRs against T. trichiura were 43, 46, and 44% for 8, 16, and 24 mg of moxidectin alone, respectively; 60, 62, and 66% for the same moxidectin dosages plus 400 mg of albendazole, respectively; and 12% for placebo. The moxidectin-albendazole arms also revealed higher CRs and egg reduction rates against hookworm than the monotherapy arms. Moxidectin and its combination with albendazole were well tolerated. CONCLUSIONS Moxidectin-albendazole is superior to moxidectin. There is no benefit of using doses above 8 mg, which is the recommended dose for onchocerciasis. The moxidectin-albendazole combination of 8 mg plus 400 mg should be investigated further to develop recommendations for appropriate control of STH infections. CLINICAL TRIALS REGISTRATION NCT03501251.
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Affiliation(s)
- Ladina Keller
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Marta S Palmeirim
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Shaali M Ame
- Public Health Laboratory Ivo de Carneri, Chake Chake, Republic of Tanzania
| | - Said M Ali
- Public Health Laboratory Ivo de Carneri, Chake Chake, Republic of Tanzania
| | - Maxim Puchkov
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Technology, , Basel, Switzerland
| | - Jörg Huwyler
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Technology, , Basel, Switzerland
| | - Jan Hattendorf
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jennifer Keiser
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
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O'Halloran DM. Considerations for anthelmintic resistance emergence in hookworm at a single locus. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2021. [PMCID: PMC8906071 DOI: 10.1016/j.crpvbd.2020.100006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Over 800 million people are infected with hookworms around the world. Hookworms of the genus Ancylostoma and Necator are examples of nematodes that harbor the ability to enter a host by penetrating the skin, and after entry the infective larvae migrate to the small intestine where they encounter host-specific signals that initiate developmental pathways and culminate in maturation to the adult stage. Currently no vaccine is available for the treatment of hookworm infection. The control strategy is limited to anthelmintic drugs, which run the risk of losing efficacy as resistance grows. Genetic resistance has developed against all classes of anthelmintic drugs against livestock parasites, and recently markers of anthelmintic resistance in human hookworm populations have been reported. As anthelmintic resistance develops in human populations of hookworm, new drugs and novel control methods like vaccines will be required in the future to control hookworm transmission. This review outlines how population genetics and anthelmintic resistance could interact at a single locus to influence current control strategies. This review outlines how population genetics and anthelmintic resistance may interact to influence current control strategies. Altering mutation rate modifies rate of emergence of anthelmintic resistance. Genotypic fitness changes the efficacy of anthelmintic administration.
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Palmeirim MS, Bosch F, Ame SM, Ali SM, Hattendorf J, Keiser J. Efficacy, safety and acceptability of a new chewable formulation versus the solid tablet of mebendazole against hookworm infections in children: An open-label, randomized controlled trial. EClinicalMedicine 2020; 27:100556. [PMID: 33150325 PMCID: PMC7599302 DOI: 10.1016/j.eclinm.2020.100556] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 09/08/2020] [Accepted: 09/09/2020] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND Soil-transmitted helminths (STHs) infect almost 1·5 billion people worldwide. The control of STH infections is based on preventive chemotherapy using either albendazole or mebendazole. Before being widely used, a sufficient body of evidence on efficacy, safety and acceptability is warranted for the new chewable child-friendly formulation of mebendazole that was recently developed. METHODS We conducted a randomised controlled superiority trial in four primary schools and kindergartens on Pemba Island, Tanzania. We considered eligible children aged 3 to 12 years with a hookworm infection intensity of at least 50 eggs per gram (EPG) of stool and no chronic diseases. Participants were allocated to treatment arms (ratio 1:1) using a computer generated random sequence. Our primary outcome was geometric mean based egg reduction rate (ERR) against hookworm assessed 14-21 days post-treatment. This trial complete and is registered with ClinicalTrials.gov, number NCT03995680 (June 24, 2019). FINDINGS 397 children were eligible and randomised into the solid (198) or chewable (199) tablet arms, of whom 393 were analysed. We found no significant difference between both formulations in terms of ERR (solid 70·8% versus chewable 68·5%, difference in ERRgeometric mean 2·3%-points, 95% CI -7·8 to 12·6, p = 0.65) and CR (11·2 versus 12·7%, 95% CI -4·9 to 7·9, p = 0.65) against hookworm infections. Adverse events were mild in both treatment arms. INTERPRETATIONS Though we could not demonstrate superiority in terms of efficacy of the new formulation, the difference between arms was small and therefore, the chewable formulation could be safely used as an alternative to swallowable tablets, in particular in young children who may have swallowing difficulties. This might help increase compliance and, consequently, enhance the effect of preventive chemotherapy.
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Affiliation(s)
- Marta S. Palmeirim
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, and University of Basel, P.O. Box, CH-4002, Basel, Switzerland
| | - Felix Bosch
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, and University of Basel, P.O. Box, CH-4002, Basel, Switzerland
| | - Shaali M. Ame
- Public Health Laboratory Ivo de Carneri, Chake, Tanzania
| | - Said M. Ali
- Public Health Laboratory Ivo de Carneri, Chake, Tanzania
| | - Jan Hattendorf
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, and University of Basel, Basel, Switzerland
| | - Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, and University of Basel, P.O. Box, CH-4002, Basel, Switzerland
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Kulinkina AV, Sarkar R, Mohan VR, Walz Y, Kaliappan SP, Ajjampur SSR, Ward H, Naumova EN, Kang G. Prediction of hookworm prevalence in southern India using environmental parameters derived from Landsat 8 remotely sensed data. Int J Parasitol 2019; 50:47-54. [PMID: 31756313 DOI: 10.1016/j.ijpara.2019.10.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 09/30/2019] [Accepted: 10/03/2019] [Indexed: 11/20/2022]
Abstract
Soil-transmitted helminth infections propagate poverty and slow economic growth in low-income countries. As with many other neglected tropical diseases, environmental conditions are important determinants of soil-transmitted helminth transmission. Hence, remotely sensed data are commonly utilised in spatial risk models intended to inform control strategies. In the present study, we build upon the existing modelling approaches by utilising fine spatial resolution Landsat 8 remotely sensed data in combination with topographic variables to predict hookworm prevalence in a hilly tribal area in southern India. Hookworm prevalence data collected from two field surveys were used in a random forest model to investigate the predictive capacity of 15 environmental variables derived from two remotely sensed images acquired during dry and rainy seasons. A variable buffer radius (100-1000 m) was applied to the point-prevalence locations in order to integrate environmental conditions around the village centroids into the modelling approach and understand where transmission is more likely. Elevation and slope were the most important variables in the models, with lower elevation and higher slope correlating with higher transmission risk. A modified normalised difference water index was among other recurring important variables, likely responsible for some seasonal differences in model performance. The 300 m buffer distance produced the best model performance in this setting, with another spike at 700 m, and a marked drop-off in R2 values at 1000 m. In addition to assessing a large number of environmental correlates with hookworm transmission, the study contributes to the development of standardised methods of spatial linkage of continuous environmental data with point-based disease prevalence measures for the purpose of spatially explicit risk profiling.
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Affiliation(s)
- Alexandra V Kulinkina
- Department of Public Health and Community Medicine, Tufts University School of Medicine, Boston, MA, USA; Partners In Health, Neno, Malawi.
| | - Rajiv Sarkar
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Venkata R Mohan
- Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
| | - Yvonne Walz
- Institute for Environment and Human Security, United Nations University, Bonn, Germany
| | | | - Sitara S R Ajjampur
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Honorine Ward
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India; Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center, Boston, MA, USA
| | - Elena N Naumova
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India; Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA, USA
| | - Gagandeep Kang
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
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10
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Muliyil DE, Rose A, Senthamizh SV, Chatterjee T, Helan J, Kang G, Muliyil J. Prevalence and Risk Factors of Vitamin A Deficiency in Children and Women of Childbearing Age in a Southern Indian Tribal Population: A Cross-Sectional Study. Indian J Community Med 2019; 44:162-165. [PMID: 31333297 PMCID: PMC6625259 DOI: 10.4103/ijcm.ijcm_213_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Night blindness and keratomalacia continue to be a problem among the tribal children and pregnant women residing in Jawadhi hills. OBJECTIVES The objective of the study is to determine the prevalence and risk factors of Vitamin A deficiency (VAD) among children aged 1-8 years and women of reproductive age in a southern Indian tribal population. MATERIALS AND METHODS A cross-sectional study was done among children aged 1-8 years and women aged 15-45 years residing in Jawadhi hills. Participants were randomly selected by cluster sampling. Their sociodemographic characteristics and frequency of consumption of Vitamin A rich food were collected through a structured questionnaire. Anthropometric measures and serum retinol levels, using high-performance liquid chromatography, were estimated for all participants. RESULTS A total of 166 children and 211 women participated in this study. The prevalence of VAD among the children (1-8 years) was 10.2% (95% confidence interval [CI] 5.5%-14.9%) and among women of the reproductive age group was 3.8% (95% CI: 1.2%-6.4%). Dietary intake was not associated with serum retinol levels. Low educational status of the head of the household (adjusted odds ratio [aOR] = 8.9) and pregnancy (aOR = 11.6) was significantly associated with an increased risk of VAD among children and women, respectively. CONCLUSIONS The prevalence of VAD among children is a moderate public health problem. Strategies must focus on pregnant women and children from families with more than four children.
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Affiliation(s)
- Divya Elizabeth Muliyil
- Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India,Address for correspondence: Dr. Divya Elizabeth Muliyil, Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India. E-mail:
| | - Anuradha Rose
- Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
| | - Sowmiya V Senthamizh
- Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
| | - Tara Chatterjee
- Department of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Jasmin Helan
- Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
| | - Gangandeep Kang
- Department of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Jayaprakash Muliyil
- Department of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
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11
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Hu Z, Chen H, Huang L, Chen S, Huang Z, Qin S, Zhong J, Qin X, Li S. Correlation between hematological parameters and ancylostomiasis: A retrospective study. J Clin Lab Anal 2018; 33:e22705. [PMID: 30390342 DOI: 10.1002/jcla.22705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/05/2018] [Accepted: 10/05/2018] [Indexed: 01/21/2023] Open
Abstract
OBJECTIVE Our aim intended to determine the relationship between hematological parameters (neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], and eosinophil-to-lymphocyte ratio [ELR]) and ancylostomiasis. METHODS There were 140 patients with ancylostomiasis and 159 healthy controls enrolled in this study. All data were collected from electronic medical records of the First Affiliated Hospital of Guangxi Medical University. RESULTS The levels of NLR, PLR, and ELR in ancylostomiasis patients were significantly higher than those in the healthy controls (all P = 0.000). A receiver operating characteristic curve was generated to assess the diagnostic efficacy of these three hematological parameters. ELR (AUC = 0.850; sensitivity = 75.00%; specificity = 86.80%) showed the superior AUC than those of NLR (AUC = 0.718; sensitivity = 53.57%; specificity = 88.68%) and PLR (AUC = 0.806; sensitivity = 68.57%; specificity = 86.79%), respectively. A multivariate regression model using the two selected indices (RBC and ELR) was established with the model's sensitivity and specificity reached 82.86% and 96.23%, respectively. In the ancylostomiasis patient group, NLR (r = -0.452, P = 0.000) and PLR (r = -0.357, P = 0.000) were reversely associated with eosinophils. CONCLUSION The pretreatment levels of the three hematological parameters (NLR, PLR, and ELR) may serve as valuable indicators for distinguishing patients with ancylostomiasis from healthy controls. NLR and PLR are negatively associated with the previous indicator, eosinophils.
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Affiliation(s)
- Zuojian Hu
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Huaping Chen
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Li Huang
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Siyuan Chen
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Zhili Huang
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Shanzi Qin
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Jianing Zhong
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Xue Qin
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Shan Li
- Department of Laboratory Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning, China
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12
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Coffeng LE, Truscott JE, Farrell SH, Turner HC, Sarkar R, Kang G, de Vlas SJ, Anderson RM. Comparison and validation of two mathematical models for the impact of mass drug administration on Ascaris lumbricoides and hookworm infection. Epidemics 2018; 18:38-47. [PMID: 28279454 PMCID: PMC5340859 DOI: 10.1016/j.epidem.2017.02.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 01/31/2017] [Accepted: 02/01/2017] [Indexed: 11/02/2022] Open
Abstract
The predictions of two mathematical models of the transmission dynamics of Ascaris lumbricoides and hookworm infection and the impact of mass drug administration (MDA) are compared, using data from India. One model has an age structured partial differential equation (PDE) deterministic framework for the distribution of parasite numbers per host and sexual mating. The second model is an individual-based stochastic model. Baseline data acquired prior to treatment are used to estimate key transmission parameters, and forward projections are made, given the known MDA population coverage. Predictions are compared with observed post-treatment epidemiological patterns. The two models could equally well predict the short-term impact of deworming on A. lumbricoides and hookworm infection levels, despite being fitted to different subsets and/or summary statistics of the data. As such, the outcomes give confidence in their use as aids to policy formulation for the use of PCT to control A. lumbricoides and hookworm infection. The models further largely agree in a qualitative sense on the added benefit of semi-annual vs. annual deworming and targeting of the entire population vs. only children, as well as the potential for interruption of transmission. Further, this study also illustrates that long-term predictions are sensitive to modelling assumptions about which age groups contribute most to transmission, which depends on human demography and age-patterns in exposure and contribution to the environmental reservoir of infection, the latter being notoriously difficult to empirically quantify.
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Affiliation(s)
- Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
| | - James E Truscott
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, London WC2 1 PG, United Kingdom
| | - Sam H Farrell
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, London WC2 1 PG, United Kingdom
| | - Hugo C Turner
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, London WC2 1 PG, United Kingdom
| | - Rajiv Sarkar
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore 632004, Tamil Nadu, India
| | - Gagandeep Kang
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore 632004, Tamil Nadu, India
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Roy M Anderson
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, London WC2 1 PG, United Kingdom
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13
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Werkman M, Wright JE, Truscott JE, Easton AV, Oliveira RG, Toor J, Ower A, Ásbjörnsdóttir KH, Means AR, Farrell SH, Walson JL, Anderson RM. Testing for soil-transmitted helminth transmission elimination: Analysing the impact of the sensitivity of different diagnostic tools. PLoS Negl Trop Dis 2018; 12:e0006114. [PMID: 29346366 PMCID: PMC5773090 DOI: 10.1371/journal.pntd.0006114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 11/14/2017] [Indexed: 12/27/2022] Open
Abstract
In recent years, an increased focus has been placed upon the possibility of the elimination of soil-transmitted helminth (STH) transmission using various interventions including mass drug administration. The primary diagnostic tool recommended by the WHO is the detection of STH eggs in stool using the Kato-Katz (KK) method. However, detecting infected individuals using this method becomes increasingly difficult as the intensity of infection decreases. Newer techniques, such as qPCR, have been shown to have greater sensitivity than KK, especially at low prevalence. However, the impact of using qPCR on elimination thresholds is yet to be investigated. In this paper, we aim to quantify how the sensitivity of these two diagnostic tools affects the optimal prevalence threshold at which to declare the interruption of transmission with a defined level of confidence. A stochastic, individual-based STH transmission model was used in this study to simulate the transmission dynamics of Ascaris and hookworm. Data from a Kenyan deworming study were used to parameterize the diagnostic model which was based on egg detection probabilities. The positive and negative predictive values (PPV and NPV) were calculated to assess the quality of any given threshold, with the optimal threshold value taken to be that at which both were maximised. The threshold prevalence of infection values for declaring elimination of Ascaris transmission were 6% and 12% for KK and qPCR respectively. For hookworm, these threshold values are lower at 0.5% and 2% respectively. Diagnostic tests with greater sensitivity are becoming increasingly important as we approach the elimination of STH transmission in some regions of the world. For declaring the elimination of transmission, using qPCR to diagnose STH infection results in the definition of a higher prevalence, than when KK is used.
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Affiliation(s)
- Marleen Werkman
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
| | - James E. Wright
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
| | - James E. Truscott
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
| | - Alice V. Easton
- Helminth Immunology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda MD, United States of America
| | - Rita G. Oliveira
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
| | - Jaspreet Toor
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
| | - Alison Ower
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
| | - Kristjana H. Ásbjörnsdóttir
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| | - Arianna R. Means
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| | - Sam H. Farrell
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
| | - Judd L. Walson
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| | - Roy M. Anderson
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, United Kingdom
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14
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Truscott JE, Werkman M, Wright JE, Farrell SH, Sarkar R, Ásbjörnsdóttir K, Anderson RM. Identifying optimal threshold statistics for elimination of hookworm using a stochastic simulation model. Parasit Vectors 2017; 10:321. [PMID: 28666452 PMCID: PMC5493114 DOI: 10.1186/s13071-017-2256-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 06/12/2017] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND There is an increased focus on whether mass drug administration (MDA) programmes alone can interrupt the transmission of soil-transmitted helminths (STH). Mathematical models can be used to model these interventions and are increasingly being implemented to inform investigators about expected trial outcome and the choice of optimum study design. One key factor is the choice of threshold for detecting elimination. However, there are currently no thresholds defined for STH regarding breaking transmission. METHODS We develop a simulation of an elimination study, based on the DeWorm3 project, using an individual-based stochastic disease transmission model in conjunction with models of MDA, sampling, diagnostics and the construction of study clusters. The simulation is then used to analyse the relationship between the study end-point elimination threshold and whether elimination is achieved in the long term within the model. We analyse the quality of a range of statistics in terms of the positive predictive values (PPV) and how they depend on a range of covariates, including threshold values, baseline prevalence, measurement time point and how clusters are constructed. RESULTS End-point infection prevalence performs well in discriminating between villages that achieve interruption of transmission and those that do not, although the quality of the threshold is sensitive to baseline prevalence and threshold value. Optimal post-treatment prevalence threshold value for determining elimination is in the range 2% or less when the baseline prevalence range is broad. For multiple clusters of communities, both the probability of elimination and the ability of thresholds to detect it are strongly dependent on the size of the cluster and the size distribution of the constituent communities. Number of communities in a cluster is a key indicator of probability of elimination and PPV. Extending the time, post-study endpoint, at which the threshold statistic is measured improves PPV value in discriminating between eliminating clusters and those that bounce back. CONCLUSIONS The probability of elimination and PPV are very sensitive to baseline prevalence for individual communities. However, most studies and programmes are constructed on the basis of clusters. Since elimination occurs within smaller population sub-units, the construction of clusters introduces new sensitivities for elimination threshold values to cluster size and the underlying population structure. Study simulation offers an opportunity to investigate key sources of sensitivity for elimination studies and programme designs in advance and to tailor interventions to prevailing local or national conditions.
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Affiliation(s)
- James E Truscott
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, W2 1PG, London, UK. .,The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD, UK.
| | - Marleen Werkman
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, W2 1PG, London, UK.,The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD, UK
| | - James E Wright
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, W2 1PG, London, UK.,The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD, UK
| | - Sam H Farrell
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, W2 1PG, London, UK
| | - Rajiv Sarkar
- Division of Gastrointestinal Sciences, Christian Medical College, Vellore, 632004, India
| | - Kristjana Ásbjörnsdóttir
- The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD, UK.,Department of Global Health, University of Washington, Seattle, USA
| | - Roy M Anderson
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, W2 1PG, London, UK.,The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD, UK
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15
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Werkman M, Truscott JE, Toor J, Wright JE, Anderson RM. The past matters: estimating intrinsic hookworm transmission intensity in areas with past mass drug administration to control lymphatic filariasis. Parasit Vectors 2017; 10:254. [PMID: 28535806 PMCID: PMC5493118 DOI: 10.1186/s13071-017-2177-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 05/05/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Current WHO guidelines for soil-transmitted helminth (STH) control focus on mass drug administration (MDA) targeting preschool-aged (pre-SAC) and school-aged children (SAC), with the goal of eliminating STH as a public health problem amongst children. Recently, attention and funding has turned towards the question whether MDA alone can result in the interruption of transmission for STH. The lymphatic filariasis (LF) elimination programme, have been successful in reaching whole communities. There is the possibility of building upon the infrastructure created for these LF-programmes to enhance the control of STH. Using hookworm as an example, we explore what further MDA coverage might be required to induce interruption of transmission for hookworm in the wake of a successful LF programme. RESULTS Analyses based on the model of STH transmission and MDA impact predict the effects of previous LF control by MDA over five years, on a defined baseline prevalence of STH in an area with a defined transmission intensity (the basic reproductive number R0). If the LF MDA programme achieved a high coverage (70, 70 and 60% for pre-SAC, SAC and adults, respectively) we expect that in communities with a hookworm prevalence of 15%, after 5 years of LF control, the intrinsic R0 value in that setting is 2.47. By contrast, if lower LF coverages were achieved (40, 40 and 30% for pre-SAC, SAC and adults, respectively), with the same prevalence of 15% at baseline (after 5 years of LF MDA), the intrinsic hookworm R0 value is predicted to be 1.67. The intrinsic R0 value has a large effect on the expected successes of follow-up STH programmes post LF MDA. Consequently, the outcomes of identical programmes may differ between these communities. CONCLUSION To design the optimal MDA intervention to eliminate STH infections, it is vital to have information on historical MDA programmes and baseline prevalence to estimate the intrinsic transmission intensity for the defined setting (R0). The baseline prevalence alone is not sufficient to inform policy for the control of STH, post cessation of LF MDA, since this will be highly dependent on the intensity and effectiveness of past programmes and the intrinsic transmission intensity of the dominant STH species in any given setting.
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Affiliation(s)
- Marleen Werkman
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, W2 1PG United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD United Kingdom
| | - James E. Truscott
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, W2 1PG United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD United Kingdom
| | - Jaspreet Toor
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, W2 1PG United Kingdom
| | - James E. Wright
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, W2 1PG United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD United Kingdom
| | - Roy M. Anderson
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London, W2 1PG United Kingdom
- The DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD United Kingdom
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