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Faiad SM, Williams MA, Goodman M, Sokolow S, Olden JD, Mitchell K, Andriantsoa R, Gordon Jones JP, Andriamaro L, Ravoniarimbinina P, Rasamy J, Ravelomanana T, Ravelotafita S, Ravo R, Rabinowitz P, De Leo GA, Wood CL. Temperature affects predation of schistosome-competent snails by a novel invader, the marbled crayfish Procambarus virginalis. PLoS One 2023; 18:e0290615. [PMID: 37703262 PMCID: PMC10499222 DOI: 10.1371/journal.pone.0290615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 08/12/2023] [Indexed: 09/15/2023] Open
Abstract
The human burden of environmentally transmitted infectious diseases can depend strongly on ecological factors, including the presence or absence of natural enemies. The marbled crayfish (Procambarus virginalis) is a novel invasive species that can tolerate a wide range of ecological conditions and colonize diverse habitats. Marbled crayfish first appeared in Madagascar in 2005 and quickly spread across the country, overlapping with the distribution of freshwater snails that serve as the intermediate host of schistosomiasis-a parasitic disease of poverty with human prevalence ranging up to 94% in Madagascar. It has been hypothesized that the marbled crayfish may serve as a predator of schistosome-competent snails in areas where native predators cannot and yet no systematic study to date has been conducted to estimate its predation rate on snails. Here, we experimentally assessed marbled crayfish consumption of uninfected and infected schistosome-competent snails (Biomphalaria glabrata and Bulinus truncatus) across a range of temperatures, reflective of the habitat range of the marbled crayfish in Madagascar. We found that the relationship between crayfish consumption and temperature is unimodal with a peak at ~27.5°C. Per-capita consumption increased with body size and was not affected either by snail species or their infectious status. We detected a possible satiation effect, i.e., a small but significant reduction in per-capita consumption rate over the 72-hour duration of the predation experiment. Our results suggest that ecological parameters, such as temperature and crayfish weight, influence rates of consumption and, in turn, the potential impact of the marbled crayfish invasion on snail host populations.
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Affiliation(s)
- Sara M. Faiad
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, United States of America
| | - Maureen A. Williams
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, United States of America
- Department of Biology, McDaniel College, Westminster, MD, United States of America
| | - Maurice Goodman
- Hopkins Marine Station, Dept. of Oceans and of Earth System Science, Doerr School of Sustainability, Stanford University, Stanford, CA, United States of America
| | - Susanne Sokolow
- Hopkins Marine Station, Dept. of Oceans and of Earth System Science, Doerr School of Sustainability, Stanford University, Stanford, CA, United States of America
- Marine Science Institute, University of California, Santa Barbara, Santa Barbara, CA, United States of America
| | - Julian D. Olden
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, United States of America
| | - Kaitlyn Mitchell
- Hopkins Marine Station, Dept. of Oceans and of Earth System Science, Doerr School of Sustainability, Stanford University, Stanford, CA, United States of America
| | - Ranja Andriantsoa
- Réseau International Schistosomiase Environnement Aménagement et Lutte (RISEAL) Madagascar, Madagascar
| | | | - Luciano Andriamaro
- Réseau International Schistosomiase Environnement Aménagement et Lutte (RISEAL) Madagascar, Madagascar
| | | | - Jeanne Rasamy
- Réseau International Schistosomiase Environnement Aménagement et Lutte (RISEAL) Madagascar, Madagascar
- Department of Zoology and Animal Biodiversity, University of Antananarivo, Antananarivo, Madagascar
| | - Tsilavina Ravelomanana
- Réseau International Schistosomiase Environnement Aménagement et Lutte (RISEAL) Madagascar, Madagascar
- Department of Zoology and Animal Biodiversity, University of Antananarivo, Antananarivo, Madagascar
| | - Salohy Ravelotafita
- Department of Zoology and Animal Biodiversity, University of Antananarivo, Antananarivo, Madagascar
| | - Ranaivosolo Ravo
- Department of Zoology and Animal Biodiversity, University of Antananarivo, Antananarivo, Madagascar
| | - Peter Rabinowitz
- Department of Environmental/Occupational Health Sciences, Global Health, University of Washington, Seattle, WA, United States of America
- Center for One Health Research (COHR), University of Washington, Seattle, WA, United States of America
| | - Giulio A. De Leo
- Hopkins Marine Station, Dept. of Oceans and of Earth System Science, Doerr School of Sustainability, Stanford University, Stanford, CA, United States of America
- Woods Institute for the Environment, Stanford University, Stanford, CA, United States of America
| | - Chelsea L. Wood
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, United States of America
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Norbury LJ, Shirakashi S, Power C, Nowak BF, Bott NJ. Praziquantel use in aquaculture - Current status and emerging issues. Int J Parasitol Drugs Drug Resist 2022; 18:87-102. [PMID: 35220160 PMCID: PMC8881684 DOI: 10.1016/j.ijpddr.2022.02.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 02/13/2022] [Accepted: 02/17/2022] [Indexed: 12/02/2022]
Abstract
Parasitic diseases are major constraints in fish mariculture. The anthelmintic praziquantel (PZQ) can effectively treat a range of flatworm parasites in a variety of fish species and has potential for broader application than its current use in the global aquaculture industry. In this review we report on PZQ's current use in the aquaculture industry and discuss its efficacy against various flatworm parasites of fish. Routes of PZQ administration are evaluated, along with issues related to palatability, pharmacokinetics and toxicity in fish, while PZQ's effects on non-target species, environmental impacts, and the development of drug-resistance are discussed.
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Affiliation(s)
- Luke J Norbury
- School of Science, STEM College, RMIT University, Bundoora, 3083, Victoria, Australia
| | - Sho Shirakashi
- Aquaculture Research Institute, Kindai University, Wakayama, 649-2211, Japan
| | - Cecilia Power
- School of Science, STEM College, RMIT University, Bundoora, 3083, Victoria, Australia
| | - Barbara F Nowak
- School of Science, STEM College, RMIT University, Bundoora, 3083, Victoria, Australia; Institute for Marine and Antarctic Studies, University of Tasmania, Launceston, 7250, Tasmania, Australia
| | - Nathan J Bott
- School of Science, STEM College, RMIT University, Bundoora, 3083, Victoria, Australia.
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Zacharia A, Mushi V, Makene T. A systematic review and meta-analysis on the rate of human schistosomiasis reinfection. PLoS One 2020; 15:e0243224. [PMID: 33270752 PMCID: PMC7714137 DOI: 10.1371/journal.pone.0243224] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 11/17/2020] [Indexed: 11/19/2022] Open
Abstract
While praziquantel mass drug administration is currently the most widely used method in the control of human schistosomiasis, it does not prevent subsequent reinfection hence persistent transmission. Towards schistosomiasis elimination, understanding the reinfection rate is crucial in planning for the future interventions. However, there is scarcity of information on the global reinfection rate of schistosomiasis. This systematic review and meta-analysis aimed at summarizing studies that estimated the reinfection rate of human schistosomiasis. Three data bases (PubMed, Hinari and Google Scholar) were thoroughly searched to retrieve original research articles presenting data on reinfection rate of human schistosomiasis. Study quality and risk of bias was assessed based on Joanna Briggs Institute critical appraisal checklist. Meta-analysis was conducted using statistical R version 3.6.2 and R Studio using "meta" and "metafor" packages. Random effect model was employed to estimate pooled reinfection rates. Heterogeneity was determined using Cochran's Q (chi-square)-test and Higgins I2 statistics. A total of 29 studies met inclusion criteria to be included in this review. All studies had at least satisfactory (5-9 scores) quality. The overal mean and pooled reinfection rates of schistosomiasis were 36.1% (±23.3%) and 33.2% (95% CI, 26.5-40.5%) respectively. For intestinal schistosomiasis, the mean and pooled reinfection rates were 43.9% (±20.6%) and 43.4% (95% CI, 35.8-51.4%), and that for urogenital schistosomiasis were 17.6% (±10.8%) and 19.4% (95% CI, 12.3%- 29.2%) respectively. Cochran's Q (chi-square)-test and Higgins I2 statistic indicated significant heterogeneity across studies (p-values < 0.001, I2 values > 95%). Results of subgroup analysis showed that, the type of Schistosoma species, participants' age group, sample size and geographical area had influence on disparity variation in reinfection rate of schistosomiasis (p < 0.1). Despite the control measures in place, the re-infection rate is still high, specifically on intestinal schistosomiasis as compared to urogenital schistosomiasis. Achieving 2030 sustainable development goal 3 on good health and wellbeing intensive programmatic strategies for schistosomiasis elimination should be implemented. Among such strategies to be used at national level are repeated mass drug administration at least every six months, intensive snails control and health education.
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Affiliation(s)
- Abdallah Zacharia
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Vivian Mushi
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Twilumba Makene
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
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4
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Faust CL, Osakunor DNM, Downs JA, Kayuni S, Stothard JR, Lamberton PHL, Reinhard-Rupp J, Rollinson D. Schistosomiasis Control: Leave No Age Group Behind. Trends Parasitol 2020; 36:582-591. [PMID: 32430274 DOI: 10.1016/j.pt.2020.04.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/15/2020] [Accepted: 04/17/2020] [Indexed: 01/11/2023]
Abstract
Despite accelerating progress towards schistosomiasis control in sub-Saharan Africa, several age groups have been eclipsed by current treatment and monitoring strategies that mainly focus on school-aged children. As schistosomiasis poses a threat to people of all ages, unfortunate gaps exist in current treatment coverage and associated monitoring efforts, preventing subsequent health benefits to preschool-aged children as well as certain adolescents and adults. Expanding access to younger ages through the forthcoming pediatric praziquantel formulation and improving treatment coverage in older ages is essential. This should occur alongside formal inclusion of these groups in large-scale monitoring and evaluation activities. Current omission of these age groups from treatment and monitoring exacerbates health inequities and has long-term consequences for sustainable schistosomiasis control.
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Affiliation(s)
- Christina L Faust
- Wellcome Centre for Integrative Parasitology, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK.
| | - Derick N M Osakunor
- Institute of Immunology and Infection Research, University of Edinburgh, Ashworth Laboratories, King's Buildings, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Jennifer A Downs
- Center for Global Health, Department of Medicine, Weill Cornell Medicine, New York, NY 10065, USA
| | - Sekeleghe Kayuni
- Department of Tropical Disease Biology, Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK; MASM Medi Clinics Limited, Medical Aid Society of Malawi (MASM), Blantyre, Malawi
| | - J Russell Stothard
- Department of Tropical Disease Biology, Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Poppy H L Lamberton
- Wellcome Centre for Integrative Parasitology, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK
| | | | - David Rollinson
- Global Schistosomiasis Alliance, Natural History Museum, London SW7 5BD, UK
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Mogeni P, Vandormael A, Cuadros D, Appleton C, Tanser F. Impact of community piped water coverage on re-infection with urogenital schistosomiasis in rural South Africa. eLife 2020; 9:54012. [PMID: 32178761 PMCID: PMC7108860 DOI: 10.7554/elife.54012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 03/10/2020] [Indexed: 12/15/2022] Open
Abstract
Previously, we demonstrated that coverage of piped water in the seven years preceding a parasitological survey was strongly predictive of Schistosomiasis haematobium infection in a nested cohort of 1976 primary school children (Tanser, 2018). Here, we report on the prospective follow up of infected members of this nested cohort (N = 333) for two successive rounds following treatment. Using a negative binomial regression fitted to egg count data, we found that every percentage point increase in piped water coverage was associated with 4.4% decline in intensity of re-infection (incidence rate ratio = 0.96, 95% CI: 0.93–0.98, p=0.004) among the treated children. We therefore provide further compelling evidence in support of the scaleup of piped water as an effective control strategy against Schistosoma haematobium transmission.
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Affiliation(s)
- Polycarp Mogeni
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,School of Nursing and Public Health, University of KwaZulu-Natal, KwaZulu-Natal, South Africa.,KwaZulu-Natal Innovation and Sequencing Platform (KRISP), University of KwaZulu-Natal, KwaZulu-Natal, South Africa
| | - Alain Vandormael
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,School of Nursing and Public Health, University of KwaZulu-Natal, KwaZulu-Natal, South Africa.,KwaZulu-Natal Innovation and Sequencing Platform (KRISP), University of KwaZulu-Natal, KwaZulu-Natal, South Africa.,Heidelberg Institute of Global Health, Faculty of Medicine, University of Heidelberg, Heidelberg, Germany
| | - Diego Cuadros
- Department of Geography and Geographic Information Science, University of Cincinnati, Cincinnati, United States.,Health Geography and Disease Modeling Laboratory, University of Cincinnati, Cincinnati, United States
| | - Christopher Appleton
- School of Life Sciences, University of KwaZulu-Natal, KwaZulu-Natal, South Africa
| | - Frank Tanser
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,School of Nursing and Public Health, University of KwaZulu-Natal, KwaZulu-Natal, South Africa.,Lincoln International Institute for Rural Health, University of Lincoln, Lincoln, United Kingdom
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6
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Martel RA, Osei BG, Kulinkina AV, Naumova EN, Abdulai AA, Tybor D, Kosinski KC. Assessment of urogenital schistosomiasis knowledge among primary and junior high school students in the Eastern Region of Ghana: A cross-sectional study. PLoS One 2019; 14:e0218080. [PMID: 31194804 PMCID: PMC6563970 DOI: 10.1371/journal.pone.0218080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Accepted: 05/24/2019] [Indexed: 11/29/2022] Open
Abstract
Background Knowledge of urogenital schistosomiasis can empower individuals to limit surface water contact and participate in mass drug administration campaigns, but nothing is currently known about the schistosomiasis knowledge that schoolchildren have in Ghana. We developed and implemented a survey tool aiming to assess the knowledge of urogenital schistosomiasis (treatment, transmission, prevention, symptoms) among science teaches and primary and junior high school students in the Eastern Region of Ghana. Methods We developed a 22-question knowledge survey tool and administered it to 875 primary and 938 junior high school students from 74 schools in 37 communities in the Eastern Region of Ghana. Teachers (n = 57) answered 20 questions matched to student questions. We compared knowledge scores (as percent of correct answers) across topics, gender, and class year and assessed associations with teacher’s knowledge scores using t-tests, chi-squared tests, univariate, and multivariate linear regression, respectively. Results Students performed best when asked about symptoms (mean±SD: 76±21% correct) and prevention (mean±SD: 69±25% correct) compared with transmission (mean±SD: 50±15% correct) and treatment (mean±SD: 44±23% correct) (p<0.0005). Teachers performed best on prevention (mean±SD: 93±12% correct, p<0.0005) and poorest on treatment (mean±SD: 69±16% correct, p<0.001). When listing five facts about urogenital schistosomiasis, teachers averaged 2.9±1.2 correct. Multiple regression models suggest that gender, class year, teacher score, and town of residency explain ~27% of variability in student scores. On average, junior high school students outperformed primary school students by 10.2 percentage points (CI95%: 8.6–11.8); boys outperformed girls by 3.5 percentage points (CI95%: 2.3–4.7). Conclusions Our survey parsed four components of student and teacher knowledge. We found strong knowledge in several realms, as well as knowledge gaps, especially on transmission and treatment. Addressing relevant gaps among students and science teachers in UGS-endemic areas may help high-risk groups recognize risky water contact activities, improve participation in mass drug administration, and spark interest in science by making it practical.
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Affiliation(s)
- Rachel A. Martel
- Department of Community Health, Tufts University School of Arts and Sciences, Medford, Massachusetts, United States of America
| | - Bernard Gyamfi Osei
- University College of Agriculture and Environmental Studies, Bunso, Eastern Region, Ghana
| | - Alexandra V. Kulinkina
- Department of Civil and Environmental Engineering, Tufts University School of Engineering, Medford, Massachusetts, United States of America
| | - Elena N. Naumova
- Department of Civil and Environmental Engineering, Tufts University School of Engineering, Medford, Massachusetts, United States of America
- Division of Nutrition Data Science, Friedman School of Nutrition Science and Policy, Tufts University, Boston, Massachusetts, United States of America
| | | | - David Tybor
- Department of Public Health and Community Medicine, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Karen Claire Kosinski
- Department of Community Health, Tufts University School of Arts and Sciences, Medford, Massachusetts, United States of America
- * E-mail:
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Wright JE, Werkman M, Dunn JC, Anderson RM. Current epidemiological evidence for predisposition to high or low intensity human helminth infection: a systematic review. Parasit Vectors 2018; 11:65. [PMID: 29382360 PMCID: PMC5791198 DOI: 10.1186/s13071-018-2656-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 01/17/2018] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The human helminth infections include ascariasis, trichuriasis, hookworm infections, schistosomiasis, lymphatic filariasis (LF) and onchocerciasis. It is estimated that almost 2 billion people worldwide are infected with helminths. Whilst the WHO treatment guidelines for helminth infections are mostly aimed at controlling morbidity, there has been a recent shift with some countries moving towards goals of disease elimination through mass drug administration, especially for LF and onchocerciasis. However, as prevalence is driven lower, treating entire populations may no longer be the most efficient or cost-effective strategy. Instead, it may be beneficial to identify individuals or demographic groups who are persistently infected, often termed as being "predisposed" to infection, and target treatment at them. METHODS The authors searched Embase, MEDLINE, Global Health, and Web of Science for all English language, human-based papers investigating predisposition to helminth infections published up to October 31st, 2017. The varying definitions used to describe predisposition, and the statistical tests used to determine its presence, are summarised. Evidence for predisposition is presented, stratified by helminth species, and risk factors for predisposition to infection are identified and discussed. RESULTS In total, 43 papers were identified, summarising results from 34 different studies in 23 countries. Consistent evidence of predisposition to infection with certain species of human helminth was identified. Children were regularly found to experience greater predisposition to Ascaris lumbricoides, Schistosoma mansoni and S. haematobium than adults. Females were found to be more predisposed to A. lumbricoides infection than were males. Household clustering of infection was identified for A. lumbricoides, T. trichiura and S. japonicum. Ascaris lumbricoides and T. trichiura also showed evidence of familial predisposition. Whilst strong evidence for predisposition to hookworm infection was identified, findings with regards to which groups were affected were considerably more varied than for other helminth species. CONCLUSION This review has found consistent evidence of predisposition to heavy (and light) infection for certain human helminth species. However, further research is needed to identify reasons for the reported differences between demographic groups. Molecular epidemiological methods associated with whole genome sequencing to determine 'who infects whom' may shed more light on the factors generating predisposition.
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Affiliation(s)
- James E. Wright
- 0000 0001 2113 8111grid.7445.2Department of Infectious Disease Epidemiology, Imperial College London, St. Mary’s Campus, London, W2 1PG UK
- 0000 0001 2113 8111grid.7445.2London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Campus, London, W2 1PG UK
- 0000 0001 2172 097Xgrid.35937.3bThe DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD UK
| | - Marleen Werkman
- 0000 0001 2113 8111grid.7445.2Department of Infectious Disease Epidemiology, Imperial College London, St. Mary’s Campus, London, W2 1PG UK
- 0000 0001 2113 8111grid.7445.2London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Campus, London, W2 1PG UK
- 0000 0001 2172 097Xgrid.35937.3bThe DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD UK
| | - Julia C. Dunn
- 0000 0001 2113 8111grid.7445.2Department of Infectious Disease Epidemiology, Imperial College London, St. Mary’s Campus, London, W2 1PG UK
- 0000 0001 2113 8111grid.7445.2London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Campus, London, W2 1PG UK
| | - Roy M. Anderson
- 0000 0001 2113 8111grid.7445.2Department of Infectious Disease Epidemiology, Imperial College London, St. Mary’s Campus, London, W2 1PG UK
- 0000 0001 2113 8111grid.7445.2London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Campus, London, W2 1PG UK
- 0000 0001 2172 097Xgrid.35937.3bThe DeWorm3 Project, The Natural History Museum of London, London, SW7 5BD UK
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8
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Nyati-Jokomo Z, Chimbari MJ. Risk factors for schistosomiasis transmission among school children in Gwanda district, Zimbabwe. Acta Trop 2017; 175:84-90. [PMID: 28377221 DOI: 10.1016/j.actatropica.2017.03.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 03/29/2017] [Accepted: 03/29/2017] [Indexed: 11/28/2022]
Abstract
INTRODUCTION A nationwide cross sectional schistosomiasis survey conducted in 2011 in 280 primary schools found a prevalence rate of 22.7%. This warranted an intervention with Mass Drug Administration at all schools in line with WHO guidelines. This study aimed to identify risk factors for schistosomiasis transmission among Grade 3 children at two primary schools in Gwanda district. METHODS A descriptive cross sectional survey which was part of a larger study on Malaria and Bilharzia in Southern Africa (MABISA) was conducted. Grade 3 children (n=120) attending two purposively selected rural primary schools in Dombo and Ntalale in Gwanda were respondents. Data on socio-demographic characteristics and risk factors which included knowledge and practices were collected using a pretested interviewer administered questionnaire. RESULTS Of the 120 children, 98 (81.7%) of the children indicated that they did not consistently use the toilet. The other risk factors for schistosomiasis were bathing and swimming in rivers and dams 80 (66.7%), watering the vegetable gardens using unprotected water sources 77 (64.7%) and crossing rivers on their way to school barefooted 31.7%. History of schistosomiasis cases based on self-reporting indicated that of the 9 children 7 were girls. There was poor knowledge of schistosomiasis among the children with 54% of the children indicating that they had never heard about the disease. Misconceptions on the causes of schistosomiasis which included drinking dirty water, mosquitoes and flies as the causes of schistosomiasis were reported by the children. Parents were cited as the least disseminators of information on schistosomiasis with only 4 out of the 120 children having received information from their parents. CONCLUSION Frequent contact with unprotected water sources, non-use of the toilet, and lack of information on schistosomiasis could predispose the children to infection. There is need to raise awareness about schistosomiasis in schools and the community to reduce the risk of contracting schistosomiasis due to risky behaviour.
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Affiliation(s)
- Zibusiso Nyati-Jokomo
- Department of Community Medicine, College of Health Sciences, University of Zimbabwe, Zimbabwe.
| | - Moses J Chimbari
- University of KwaZulu-Natal, College of Health Sciences, School of Nursing and Public Health, Howard Campus, Durban, South Africa
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9
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Mari L, Ciddio M, Casagrandi R, Perez-Saez J, Bertuzzo E, Rinaldo A, Sokolow SH, De Leo GA, Gatto M. Heterogeneity in schistosomiasis transmission dynamics. J Theor Biol 2017; 432:87-99. [PMID: 28823529 PMCID: PMC5595357 DOI: 10.1016/j.jtbi.2017.08.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 06/30/2017] [Accepted: 08/15/2017] [Indexed: 01/30/2023]
Abstract
Transmission dynamics of schistosomiasis presents multiple heterogeneity sources. A comprehensive framework for heterogeneous disease transmission is proposed. Heterogeneous multigroup communities can be more prone to parasite transmission. Presence of multiple water sources can hinder parasite transmission. Spatial and temporal heterogeneities can have nontrivial implications for endemicity.
Simple models of disease propagation often disregard the effects of transmission heterogeneity on the ecological and epidemiological dynamics associated with host-parasite interactions. However, for some diseases like schistosomiasis, a widespread parasitic infection caused by Schistosoma worms, accounting for heterogeneity is crucial to both characterize long-term dynamics and evaluate opportunities for disease control. Elaborating on the classic Macdonald model for macroparasite transmission, we analyze families of models including explicit descriptions of heterogeneity related to differential transmission risk within a community, water contact patterns, the distribution of the snail host population, human mobility, and the seasonal fluctuations of the environment. Through simple numerical examples, we show that heterogeneous multigroup communities may be more prone to schistosomiasis than homogeneous ones, that the availability of multiple water sources can hinder parasite transmission, and that both spatial and temporal heterogeneities may have nontrivial implications for disease endemicity. Finally, we discuss the implications of heterogeneity for disease control. Although focused on schistosomiasis, results from this study may apply as well to other parasitic infections with complex transmission cycles, such as cysticercosis, dracunculiasis and fasciolosis.
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Affiliation(s)
- Lorenzo Mari
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, 20133 Milano, Italy.
| | - Manuela Ciddio
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, 20133 Milano, Italy
| | - Renato Casagrandi
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, 20133 Milano, Italy
| | - Javier Perez-Saez
- Laboratory of Ecohydrology, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Enrico Bertuzzo
- Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari Venezia, 30170 Venezia Mestre, Italy
| | - Andrea Rinaldo
- Laboratory of Ecohydrology, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; Dipartimento ICEA, Università di Padova, 35131 Padova, Italy
| | - Susanne H Sokolow
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA; Marine Science Institute, University of California, Santa Barbara, CA 93106, USA
| | - Giulio A De Leo
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA
| | - Marino Gatto
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, 20133 Milano, Italy
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Simoonga C, Kazembe LN. Using the hierarchical ordinal regression model to analyse the intensity of urinary schistosomiasis infection in school children in Lusaka Province, Zambia. Infect Dis Poverty 2017; 6:43. [PMID: 28219411 PMCID: PMC5319044 DOI: 10.1186/s40249-017-0262-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 02/16/2017] [Indexed: 12/19/2022] Open
Abstract
Background Urinary schistosomiasis has been a major public health problem in Zambia for many years. However, the disease profile may vary in different locale due to the changing ecosystem that contributes to the risk of acquiring the disease. The objective of this study was to quantify risk factors associated with the intensity of urinary schistosomiasis infection in school children in Lusaka Province, Zambia, in order to better understand local transmission. Methods Data were obtained from 1 912 school children, in 20 communities, in the districts of Luangwa and Kafue in Lusaka Province. Both individual- and community-level covariates were incorporated into an ordinal logistic regression model to predict the probability of an infection being a certain intensity in a three-category outcome response: 0 = no infection, 1 = light infection, and 2 = moderate/heavy infection. Random effects were introduced to capture unobserved heterogeneity. Results Overall, the risk of urinary schistosomiasis was strongly associated with age, altitude at which the child lived, and sex. Weak associations were observed with the normalized difference vegetation index, maximum temperature, and snail abundance. Detailed analysis indicated that the association between infection intensities and age and altitude were category-specific. Particularly, infection intensity was lower in children aged between 5 and 9 years compared to those aged 10 to 15 years (OR = 0.72, 95% CI = 0.51–0.99). However, the age-specific risk changed at different levels of infection, such that when comparing children with light infection to those who were not infected, age was associated with a lower odds (category 1 vs category 0: OR = 0.71, 95% CI: 0.50–0.99), yet such a relation was not significant when considering children who were moderately or heavily infected compared to those with a light or no infection (category 2 vs category 0: OR = 0.96, 95% CI: 0.45–1.64). Overall, we observed that children living in the valley were less likely to acquire urinary schistosomiasis compared to those living in plateau areas (OR = 0.48, 95% CI: 0.16–0.71). However, category-specific effects showed no significant association in category 1 (light infection), whereas in category 2 (moderate/high infection), the risk was still significantly lower for those living in the valley compared to those living in plateau areas (OR = 0.18, 95% CI: 0.04–0.75). Conclusions This study demonstrates the importance of understanding the dynamics and heterogeneity of infection in control efforts, and further suggests that apart from the well-researched factors of Schistosoma intensity, various other factors influence transmission. Control programmes need to take into consideration the varying infection intensities of the disease so that effective interventions can be designed. Electronic supplementary material The online version of this article (doi:10.1186/s40249-017-0262-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christopher Simoonga
- Ministry of Health, Ndeke House, Haile Selassie Avenue, P.O. Box 30205, Lusaka, Zambia
| | - Lawrence N Kazembe
- Mathematical Sciences Department, Chancellor College, University of Malawi, P.O. Box 280, Zomba, Malawi. .,Statistics and Population Studies Department, University of Namibia, Private Bag 13301, Windhoek, Namibia.
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11
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Sokolow SH, Wood CL, Jones IJ, Swartz SJ, Lopez M, Hsieh MH, Lafferty KD, Kuris AM, Rickards C, De Leo GA. Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best. PLoS Negl Trop Dis 2016; 10:e0004794. [PMID: 27441556 PMCID: PMC4956325 DOI: 10.1371/journal.pntd.0004794] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 05/31/2016] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Despite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control. METHODOLOGY We evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted. PRINCIPAL FINDINGS Widespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century. CONCLUSIONS/SIGNIFICANCE Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.
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Affiliation(s)
- Susanne H. Sokolow
- Hopkins Marine Station, Stanford University, Pacific Grove, California, United States of America
- Marine Science Institute, and Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
| | - Chelsea L. Wood
- Michigan Society of Fellows, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Isabel J. Jones
- Hopkins Marine Station, Stanford University, Pacific Grove, California, United States of America
| | - Scott J. Swartz
- Hopkins Marine Station, Stanford University, Pacific Grove, California, United States of America
| | - Melina Lopez
- Hopkins Marine Station, Stanford University, Pacific Grove, California, United States of America
| | - Michael H. Hsieh
- Children's National Health System, Washington, D.C., United States of America
- The George Washington University, Washington, D.C., United States of America
- Biomedical Research Institute, Rockville, Maryland, United States of America
| | - Kevin D. Lafferty
- Marine Science Institute, and Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Western Ecological Research Center, U.S. Geological Survey, Santa Barbara, California, United States of America
| | - Armand M. Kuris
- Marine Science Institute, and Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Chloe Rickards
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Giulio A. De Leo
- Hopkins Marine Station, Stanford University, Pacific Grove, California, United States of America
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12
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Grimes JET, Tadesse G, Mekete K, Wuletaw Y, Gebretsadik A, French MD, Harrison WE, Drake LJ, Gardiner IA, Yard E, Templeton MR. School Water, Sanitation, and Hygiene, Soil-Transmitted Helminths, and Schistosomes: National Mapping in Ethiopia. PLoS Negl Trop Dis 2016; 10:e0004515. [PMID: 26954688 PMCID: PMC4783033 DOI: 10.1371/journal.pntd.0004515] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 02/14/2016] [Indexed: 12/21/2022] Open
Abstract
Background It is thought that improving water, sanitation, and hygiene (WASH) might reduce the transmission of schistosomes and soil-transmitted helminths, owing to their life cycles. However, few large-scale studies have yet assessed the real extent of associations between WASH and these parasites. Methodology/Principal Findings In the 2013–2014 Ethiopian national mapping of infections with these parasites, school WASH was assessed alongside infection intensity in children, mostly between 10 and 15 years of age. Scores were constructed reflecting exposure to schistosomes arising from water collection for schools, from freshwater sources, and the adequacy of school sanitation and hygiene facilities. Kendall’s τb was used to test the WASH scores against the school-level arithmetic mean intensity of infection with each parasite, in schools with at least one child positive for the parasite in question. WASH and parasitology data were available for 1,645 schools. More frequent collection of water for schools, from open freshwater sources was associated with statistically significantly higher Schistosoma mansoni infection intensity (Kendall’s τb = 0.097, 95% confidence interval, CI: 0.011 to 0.18), better sanitation was associated with significantly lower Ascaris lumbricoides intensity (Kendall’s τb = -0.067, 95% CI: -0.11 to -0.023) and borderline significant lower hookworm intensity (Kendall’s τb = -0.039, 95% CI: -0.090 to 0.012, P = 0.067), and better hygiene was associated with significantly lower hookworm intensity (Kendall’s τb = -0.076, 95% CI: -0.13 to -0.020). However, no significant differences were observed when comparing sanitation and infection with S. mansoni or Trichuris trichiura, or hygiene and infection with A. lumbricoides or T. trichiura. Conclusions/Significance Improving school WASH may reduce transmission of these parasites. However, different forms of WASH appear to have different effects on infection with the various parasites, with our analysis finding the strongest associations between water and S. mansoni, sanitation and A. lumbricoides, and hygiene and hookworm. Water, sanitation, and hygiene (WASH) are potentially important control measures for parasitic worms, but few large-scale and well-designed research studies have aimed to quantify the relationships between WASH and infections with these parasites, or demonstrated the practicality of integrating WASH assessments into large-scale worm mapping. Here we use data from 80,475 children in 1,645 schools visited during the 2013–2014 Ethiopian national mapping of schistosomiasis and soil-transmitted helminthiases, to compare school WASH conditions with the mean intensity of infection with these parasites, using Kendall’s τb, a statistic that assesses for correlation between two variables by comparing their rankings. More frequent collection of water for schools was associated with statistically significantly (P < 0.05) higher-intensity intestinal schistosomiasis infections, better sanitation significantly with lower roundworm burdens, and better hygiene with significantly lower hookworm burdens. No statistically significant associations (P > 0.05) were found for sanitation and intestinal schistosomiasis or whipworm infections, or hygiene and roundworm or whipworm infections, but better sanitation was associated with a borderline statistically significantly less hookworm infections (P = 0.067). The results suggest that WASH improvements might have different impacts on infection with the various parasites. These differences should be borne in mind when designing WASH interventions to reduce transmission of, and prevent infection with, these parasites.
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Affiliation(s)
- Jack E. T. Grimes
- Department of Civil and Environmental Engineering, South Kensington Campus, Imperial College London, London, United Kingdom
- * E-mail:
| | | | | | - Yonas Wuletaw
- Ethiopian Public Health Institute, Addis Ababa, Ethiopia
| | | | - Michael D. French
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Wendy E. Harrison
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Lesley J. Drake
- Partnership for Child Development, Department of Infectious Disease Epidemiology, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Iain A. Gardiner
- Partnership for Child Development, Department of Infectious Disease Epidemiology, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Elodie Yard
- Partnership for Child Development, Department of Infectious Disease Epidemiology, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Michael R. Templeton
- Department of Civil and Environmental Engineering, South Kensington Campus, Imperial College London, London, United Kingdom
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13
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Anderson RM, Turner HC, Farrell SH, Truscott JE. Studies of the Transmission Dynamics, Mathematical Model Development and the Control of Schistosome Parasites by Mass Drug Administration in Human Communities. ADVANCES IN PARASITOLOGY 2016; 94:199-246. [PMID: 27756455 DOI: 10.1016/bs.apar.2016.06.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Schistosomiasis is global in extent within developing countries, but more than 90% of the at-risk population lives in sub-Saharan Africa. In total, 261 million people are estimated to require preventive treatment. However, with increasing drug availability through donation, the World Health Organization has set a goal of increasing coverage to 75% of at-risk children in endemic countries and elimination in some regions. In this chapter, we discuss key biological and epidemiological processes involved in the schistosome transmission cycle and review the history of modelling schistosomiasis and the impact of mass drug administration, including both deterministic and stochastic approaches. In particular, we look at the potential impact of the WHO 2020 schistosomiasis treatment goals.
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Affiliation(s)
- R M Anderson
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - H C Turner
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - S H Farrell
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - J E Truscott
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
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14
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Fulford AJ, Webster M, Ouma JH, Kimani G, Dunne DW. Puberty and Age-related Changes in Susceptibility to Schistosome Infection. ACTA ACUST UNITED AC 2013; 14:23-6. [PMID: 17040685 DOI: 10.1016/s0169-4758(97)01168-x] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent data from outbreaks of schistosomiasis in immunologically naive populations have refuelled the debate concerning the nature or existence of protective, acquired immunity to schistosomiasis in humans. Data from endemic communities provide some compelling evidence for an abrupt change in reinfection rates that coincides with puberty. We suggest that the hormonal changes of adrenarche may hold the key to understanding the relative resistance to infection found in adults.
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Affiliation(s)
- A J Fulford
- Division of Microbiology and Parasitology, Department of Pathology, University of Cambridge, Tennis Court Rd, Cambridge, UK CB2 1QP
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15
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Basra A, Mombo-Ngoma G, Melser MC, Diop DA, Würbel H, Mackanga JR, Fürstenau M, Zoleko RM, Adegnika AA, Gonzalez R, Menendez C, Kremsner PG, Ramharter M. Efficacy of mefloquine intermittent preventive treatment in pregnancy against Schistosoma haematobium infection in Gabon: a nested randomized controlled assessor-blinded clinical trial. Clin Infect Dis 2012; 56:e68-75. [PMID: 23175561 DOI: 10.1093/cid/cis976] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Urogenital schistosomiasis is a major public health problem in sub-Saharan Africa, and routine programs for screening and treatment of pregnant women are not established. Mefloquine-currently evaluated as a potential alternative to sulfadoxine-pyrimethamine as intermittent preventive treatment against malaria in pregnancy (IPTp)-is known to exhibit activity against Schistosoma haematobium. In this study we evaluated the efficacy of mefloquine IPTp against S. haematobium infection in pregnant women. METHODS Pregnant women with S. haematobium infection presenting at 2 antenatal health care centers in rural Gabon were invited to participate in this nested randomized controlled, assessor-blinded clinical trial comparing sulfadoxine-pyrimethamine with mefloquine IPTp. Study drugs were administered twice during pregnancy with a 1- month interval after completion of the first trimester. RESULTS Sixty-five pregnant women were included in this study. Schistosoma haematobium egg excretion rates showed a median reduction of 98% (interquartile range [IQR], 70%-100%) in the mefloquine group compared to an increase of 20% (IQR, -186% to 75%) in the comparator group. More than 80% of patients showed at least 50% reduction of egg excretion and overall cure rate was 47% (IQR, 36%-70%) 6 weeks after the second administration of mefloquine IPTp. CONCLUSION When used as IPTp for the prevention of malaria, mefloquine shows promising activity against concomitant S. haematobium infection leading to an important reduction of egg excretion in pregnant women. Provided that further studies confirm these findings, the use of mefloquine may transform future IPTp programs into a 2-pronged intervention addressing 2 of the most virulent parasitic infections in pregnant women in sub-Saharan Africa. CLINICAL TRIALS REGISTRATION NCT01132248; ATMR2010020001429343.
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Affiliation(s)
- Arti Basra
- Centre de Recherches Médicales de Lambaréné, Université des Sciences de la Santé, Libreville, Gabon
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16
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Lyke KE, Wang A, Dabo A, Arama C, Daou M, Diarra I, Plowe CV, Doumbo OK, Sztein MB. Antigen-specific B memory cell responses to Plasmodium falciparum malaria antigens and Schistosoma haematobium antigens in co-infected Malian children. PLoS One 2012; 7:e37868. [PMID: 22693628 PMCID: PMC3367916 DOI: 10.1371/journal.pone.0037868] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 04/30/2012] [Indexed: 11/19/2022] Open
Abstract
Polyparasitism is common in the developing world. We have previously demonstrated that schistosomiasis-positive (SP) Malian children have age-dependent protection from malaria compared to matched schistosomiasis-negative (SN) children. Evidence of durable immunologic memory to malaria antigens is conflicting, particularly in young children and the effect of concomitant schistomiasis upon acquisition of memory is unknown. We examined antigen-specific B memory cell (MBC) frequencies (expressed as percentage of total number of IgG-secreting cells) in 84 Malian children aged 4–14 to malaria blood-stage antigens, apical membrane antigen 1 (AMA-1) and merozoite surface protein 1 (MSP-1) and to schistosomal antigens, Soluble Worm Antigenic Preparation (SWAP) and Schistosoma Egg Antigen (SEA), at a time point during the malaria transmission season and a follow-up dry season visit. We demonstrate, for the first time, MBC responses to S. haematobium antigens in Malian children with urinary egg excretion and provide evidence of seasonal acquisition of immunologic memory, age-associated differences in MBC acquisition, and correlation with circulating S. haematobium antibody. Moreover, the presence of a parasitic co-infection resulted in older children, aged 9–14 years, with underlying S. haematobium infection having significantly more MBC response to malaria antigens (AMA1 and MSP1) than their age-matched SN counterparts. We conclude that detectable MBC response can be measured against both malaria and schistosomal antigens and that the presence of S. haematobium may be associated with enhanced MBC induction in an age-specific manner.
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Affiliation(s)
- Kirsten E Lyke
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
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17
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Bourke CD, Maizels RM, Mutapi F. Acquired immune heterogeneity and its sources in human helminth infection. Parasitology 2011; 138:139-59. [PMID: 20946693 PMCID: PMC3021922 DOI: 10.1017/s0031182010001216] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 07/18/2010] [Accepted: 07/18/2010] [Indexed: 12/13/2022]
Abstract
Similarities in the immunobiology of different parasitic worm infections indicate that co-evolution of humans and helminths has shaped a common anti-helminth immune response. However, recent in vitro and immuno-epidemiological studies highlight fundamental differences and plasticity within host-helminth interactions. The 'trade-off' between immunity and immunopathology inherent in host immune responses occurs on a background of genetic polymorphism, variable exposure patterns and infection history. For the parasite, variation in life-cycle and antigen expression can influence the effector responses directed against them. This is particularly apparent when comparing gastrointestinal and tissue-dwelling helminths. Furthermore, insights into the impact of anti-helminthic treatment and co-infection on acquired immunity suggest that immune heterogeneity arises not from hosts and parasites in isolation, but also from the environment in which immune responses develop. Large-scale differences observed in the epidemiology of human helminthiases are a product of complex host-parasite-environment interactions which, given potential for exposure to parasite antigens in utero, can arise even before a parasite interacts with its human host. This review summarizes key differences identified in human acquired immune responses to nematode and trematode infections of public health importance and explores the factors contributing to these variations.
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Affiliation(s)
- C D Bourke
- Institute of Immunology and Infection Research, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH93JT, UK.
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18
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Abbasi I, King CH, Muchiri EM, Hamburger J. Detection of Schistosoma mansoni and Schistosoma haematobium DNA by loop-mediated isothermal amplification: identification of infected snails from early prepatency. Am J Trop Med Hyg 2010; 83:427-32. [PMID: 20682894 DOI: 10.4269/ajtmh.2010.09-0764] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Monitoring post-control transmission of schistosomes by examining humans becomes less effective as infection rates among humans decrease. Molecular monitoring of prepatent schistosome infection in snails by the polymerase chain reaction (PCR) has been used for studying human-to-snail transmission, and snail prepatent infection rates were found to correspond to infection prevalence and average intensity in human populations contacting the sites studied. We have now developed loop-mediated isothermal amplification (LAMP) assays for identifying Schistosoma mansoni and S. haematobium to facilitate large-scale evaluation of post-intervention transmission potential. LAMP primers were designed based on the Sm1-7 and DraI repeated sequences of the corresponding schistosomes, and amplification by LAMP of these 121-basepair highly abundant sequences provided a detection sensitivity of 0.1 fg of genomic DNA. When these LAMP assays were applied for examining infected laboratory snails, it was possible to identify infection from the first day after exposure to miracidia. The potential advantages of these assays are discussed.
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Affiliation(s)
- Ibrahim Abbasi
- Hebrew University, Hadassah Medical School, Jerusalem, Israel
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Garba A, Pion S, Cournil A, Milet J, Schneider D, Campagne G, Chippaux JP, Boulanger D. Risk factors for Schistosoma haematobium infection and morbidity in two villages with different transmission patterns in Niger. Acta Trop 2010; 115:84-9. [PMID: 20171156 DOI: 10.1016/j.actatropica.2010.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 01/15/2010] [Accepted: 02/11/2010] [Indexed: 11/18/2022]
Abstract
A better control of major neglected tropical diseases such as schistosomiasis is urgently needed to reduce their impact on public health in developing countries. To optimize the efficiency of intervention campaigns, we assessed the influence of individual human factors on the level of Schistosoma haematobium infection and morbidity in a typical Sahelian country (Niger). Random samples of 246 and 257 individuals were selected from general census in two villages with distinct patterns of schistosome transmission. One village (Lossa) is located in an area of perennial transmission whereas transmission is seasonal in the other village (Tara). Despite comparable levels of both egg excretion and lower tract pathology in the two villages, the inhabitants of Lossa had a higher risk (OR: 2.1, 95% CI: 1.1-3.9) of developing upper tract lesions compared to those living in Tara. In both villages, bladder lesions were more serious in males than in females. Children between 7 and 15 years old were the most at risk to experience heavy infections (OR: 3.4, 95% CI: 2.1-5.7), bladder (OR: 4.5, 95% CI: 2.6-7.8) and upper tract (OR: 10.4, 95% CI: 2.4-45.0) lesions, independently of gender and village. These results confirm that targeted intervention campaigns should include foci regardless of their schistosome transmission pattern and focus on the school-aged population.
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Affiliation(s)
- Amadou Garba
- Centre de Recherche Médicale et Sanitaire, BP 10887, Niamey, Niger
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20
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Pinot de Moira A, Fulford AJC, Kabatereine NB, Kazibwe F, Ouma JH, Dunne DW, Booth M. Microgeographical and tribal variations in water contact and Schistosoma mansoni exposure within a Ugandan fishing community. Trop Med Int Health 2007; 12:724-35. [PMID: 17550469 DOI: 10.1111/j.1365-3156.2007.01842.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To explore patterns of water contact and Schistosoma mansoni exposure by age, sex, tribe and space within a single village. METHODS For 10 months, we systematically observed water contacts made by the 800 inhabitants of a small Ugandan fishing village. In order to estimate cercarial exposure, times spent in water were weighted by snail infection levels, time of day and degree of immersion. RESULTS There were marked differences in water contact patterns between the two main tribes, which inhabited geographically distinct ends of the village resulting in geographically distinct spatial patterns of water contact. The distributions of the intermediate hosts, Biomphalaria sudanica and Biomphalaria stanleyi, also appeared to differ over small distances. This led to quite different exposure patterns between the two tribes, particularly amongst females. CONCLUSIONS Schistosoma mansoni exposure can vary markedly within a single village. Such non-homogenous patterns of exposure are likely to have wider implications for schistosomiasis control programmes and research studies.
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Mutapi F, Mduluza T, Gomez-Escobar N, Gregory WF, Fernandez C, Midzi N, Maizels RM. Immuno-epidemiology of human Schistosoma haematobium infection: preferential IgG3 antibody responsiveness to a recombinant antigen dependent on age and parasite burden. BMC Infect Dis 2006; 6:96. [PMID: 16764709 PMCID: PMC1523344 DOI: 10.1186/1471-2334-6-96] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 06/09/2006] [Indexed: 11/17/2022] Open
Abstract
Background Schistosomiasis is a major parasitic disease affecting over 200 million people in the developing world with a further 400 million people at risk of infection. The aim of this study was to identify a single antigen from adult Schistosoma haematobium worms and subsequently use this antigen to study the development of schistosome-acquired immunity in a human population. Methods The full-length cDNA sequence of a S. haematobium protein, a putative orthologue of the S. mansoni tegumental antigen Sm13, was obtained from a cDNA library of adult S. haematobium worms and named Sh13 following a small-scale expressed sequence tags (EST) project. The recombinant Sh13 protein expressed in E. coli, was used to investigate immuno-epidemiological patterns in 147 Zimbabweans (7–18 years old) exposed to S. haematobium. Results Sequence analysis of the full-length cDNA sequence of the S. haematobium protein Sh13, indicated that the protein has an N-terminal signal peptide and encodes an 85-amino acid mature protein with a highly conserved predicted transmembrane domain (86 % identity with the S. mansoni tegumental antigen Sm13). The recombinant Sh13 protein was used in ELISA assays to determine the reactivity of sera from the study participants. Antibody responses against Sh13 were predominantly IgG3 isotype compared to responses against crude worm antigens which were predominantly IgG1 and IgG4. The relationship between anti-Sh13 IgG3 levels and infection intensity varied significantly with host age. The youngest children (7–10 years old) had relatively low levels of both infection and anti-Sh13 IgG3. In older children (11–12 years old) rising infection levels were accompanied by a significant increase in anti-Sh13 IgG3 levels. Subsequently, infection intensity declined significantly in 13–18 year olds but levels of the antibody continued to rise. The changing relationship between infection intensity and anti-Sh13 IgG3 levels with host age is consistent with the profile of a protective immune response predicted from theoretical work. Conclusion We have identified and characterised a novel S. haematobium antigen Sh13, a putative tegumental protein, and shown that it is recognised predominantly by IgG3 antibodies from people infected with/exposed to S. haematobium parasites. We have also shown that, the anti-Sh13 IgG3 response is maximal in older individuals with the lowest infection intensity, and that the age profile of the relationship between anti-Sh13 IgG3 and infection intensity is consistent with that predicted by theoretical work for a protective response stimulated by and directed against adult worms.
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Affiliation(s)
- Francisca Mutapi
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh, EH9 3J, UK
| | - Takafira Mduluza
- Department of Biochemistry, University of Zimbabwe, P.O. Box 167, Mount Pleasant, Harare, Zimbabwe
| | - Natalia Gomez-Escobar
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh, EH9 3J, UK
- Medical Research Council, PO Box 273, Banjul, Gambia
| | - William F Gregory
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh, EH9 3J, UK
| | - Cecilia Fernandez
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh, EH9 3J, UK
- Cátedra de Inmunología, Facultad de Química, Universidad de la República, Casilla de Correo 1157, Montevideo, Uruguay
| | - Nicholas Midzi
- National Institute of Health Research, Box CY 570, Causeway, Harare, Zimbabwe
| | - Rick M Maizels
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Rd, Edinburgh, EH9 3J, UK
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Abebe F, Erko B, Gemetchu T, Gundersen SG. Control of Biomphalaria pfeifferi population and schistosomiasis transmission in Ethiopia using the soap berry endod (Phytolacca dodecandra), with special emphasis on application methods. Trans R Soc Trop Med Hyg 2006; 99:787-94. [PMID: 16099007 DOI: 10.1016/j.trstmh.2005.04.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2004] [Revised: 04/20/2005] [Accepted: 04/21/2005] [Indexed: 10/25/2022] Open
Abstract
The endod (Phytolacca dodecandra)-based schistosomiasis mansoni control project was implemented in Ethiopia between 1994 and 1999. The aim was to develop an effective, cheap and sustainable method of controlling schistosomiasis. First, different formulations of the Ethiopian endod strain 44 (E-44) were compared for potency in the laboratory. Secondly, spray and drip-feeding methods were compared for simplicity and effectiveness in the field. Lastly, the efficacy of endod powder soap was compared with the endod spray method. In Bati stream, endod powder soap was distributed to the residents every weekend at laundry sites. In Worke stream, endod was sprayed along a 1-km stretch of the stream at 3-month intervals. No endod was applied in Harbu stream. The immediate and long-term effects of endod application on the snail population and schistosomal infection were determined. Using the spray method, 100% snail mortality could be obtained, and it was simpler and more effective than the drip-feeding method. Snail mortality ranged from 20 to 100% using endod soap. There was a progressive decline in the snail population and infection in Bati stream compared with Worke stream, mainly due to sustained use of endod soap. The advantages and disadvantages of the different endod delivery systems are discussed.
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Affiliation(s)
- F Abebe
- Institute for Community Medicine, Department of International Health, University of Oslo, Norway.
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Woolhouse ME. Immunoepidemiology of human schistosomes: taking the theory into the field. ACTA ACUST UNITED AC 2005; 10:196-202. [PMID: 15275473 DOI: 10.1016/0169-4758(94)90030-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Much is known about human immune responses to schistosome infection, but it has proved difficult to determine the impact of these responses on schistosome epidemiology in the field. In this paper, Mark Woolhouse compares epidemiological patterns from field data with the predictions o f simple mathematical models of different immunological processes. The comparison gives some indications as to which types of immune response may be important, and of their strength and duration. The results are consistent with a significant impact of a process similar to 'concomitant' immunity, with a possible role for anti-fecundity effects.
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Affiliation(s)
- M E Woolhouse
- Department of Zoology, University of Oxford, South Parks Road, Oxford, UK OX I 3PS
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24
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Galvani AP. AGE-DEPENDENT EPIDEMIOLOGICAL PATTERNS AND STRAIN DIVERSITY IN HELMINTH PARASITES. J Parasitol 2005; 91:24-30. [PMID: 15856867 DOI: 10.1645/ge-191r1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Field studies of schistosomes and the major intestinal nematodes Trichuris trichiura and Ascaris lumbricoides repeatedly demonstrate that the intensity and prevalence of infection exhibit marked dependency on host age. Peak levels of infection typically occur in hosts aged between 10 and 14 yr in endemically infected communities. It has widely been assumed that the slow acquisition of resistance in adults is caused by repeated exposure to the same antigenic repertoire of a single parasite strain. Consequently, these empirical patterns have previously been taken to suggest that human immunity to helminth parasites confers poor protection against reinfection. Here, an alternative explanation is suggested on the basis of results from a simplified model of helminth transmission. It is proposed that the empirical observations can be attributed to the circulation of multiple helminth strains that each elicit highly protective immunity. If this hypothesis is correct, estimates of epidemiological parameters from field data and the potential for control of helminth diseases might require reevaluation.
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Affiliation(s)
- Alison P Galvani
- Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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25
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Abebe F, Birkeland KI, Gaarder PI, Petros B, Gundersen SG. The relationships between dehydroepiandrosterone sulphate (DHEAS), the intensity of Schistosoma mansoni infection and parasite-specific antibody responses. A cross-sectional study in residents of endemic communities in north-east Ethiopia. APMIS 2003; 111:319-28. [PMID: 12716389 DOI: 10.1034/j.1600-0463.2003.1110205.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
There are speculations that the puberty-related hormone dehydroepiandrosterone sulphate (DHEAS) might influence the intensity of infection and immune responses during Schistosoma infections. We studied the relationships between DHEAS, intensity of Schistosoma mansoni infection and humoral immune responses in 135 residents of Ethiopia. Serum levels of eight antibody isotypes against worm and egg antigens were determined by ELISA. DHEAS was measured with an immunoluminometric assay. There was a significant negative correlation between serum levels of DHEAS and intensity of S. mansoni infection. A significant increase in serum levels of DHEAS in the age group 15-19 years was accompanied by a progressive decline in the intensity of infection. Peak level of DHEAS coincided with the lowest intensity of infection in the age group 20-29 years. Multiple regression analysis showed that DHEAS alone had a significant (p<0.0001) negative effect when the effect of age was removed. Age also had a significant (p<0.0001) negative effect on the intensity of infection, after removing the effect of DHEAS. The two predictive variables accounted for 34.4% of the decline in the intensity of infection. Age accounted for 24.9%, whereas DHEAS accounted for 15.2% when the effect of each of the variables was removed. DHEAS had significant negative effects on AWA-specific IgG (p=0.02) and IgG1 (p=0.018) and SEA-specific IgG1 (p=0.009), after adjusting for the effect of age.
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Affiliation(s)
- F Abebe
- Institute of General Practice, Department of International Health, Blindern, Oslo, Norway.
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26
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Sanderson L, Bartlett A, Whitfield PJ. In vitro and in vivo studies on the bioactivity of a ginger (Zingiber officinale) extract towards adult schistosomes and their egg production. J Helminthol 2002; 76:241-7. [PMID: 12363378 DOI: 10.1079/joh2002116] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The bioactivity of an ethyl acetate extract of ginger (Zingiber officinale) towards Schistosoma mansoni adult pairs, both cultured in vitro and in vivo in laboratory mice, was investigated by monitoring worm mortality and fecundity. In vitro, a concentration of 200 mg l(-1) of extract killed almost all worms within 24 h. Male worms seemed more susceptible than female under these conditions. Cumulative egg output of surviving worm pairs in vitro was considerably reduced when exposed to the extract. For example, after 4 days of exposure to 50 mg l(-1), cumulative egg output was only 0.38 eggs per worm pair compared with 36.35 for untreated worms. In vivo efficacy of the extract was tested by oral and subcutaneous delivery of 150 mg kg(-1) followed by assessment of worm survival and fecundity. Neither delivery route produced any significant reduction in worm numbers compared with untreated controls. Worm fecundity was assessed in vivo by cumulative egg counts per liver at 55 days post infection with mice treated subcutaneously. Such infections showed egg levels in the liver of about 2000 eggs per worm pair in 55 days, in both treated and control mice, with no significant difference between the two groups. To ensure that density-dependent effects did not confound this analysis, a separate experiment demonstrated no such influence on egg output per worm pair, at intensities between 1 and 23 worms per mouse.
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Affiliation(s)
- L Sanderson
- Division of Life Sciences, King's College London, Franklin Wilkins Building, 150 Stamford Street, London, SE1 9NN, UK
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27
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Friedman JF, Kurtis JD, McGarvey ST, Fraga AL, Silveira A, Pizziolo V, Gazzinelli G, LoVerde P, Corrêa-Oliveira R. Comparison of self-reported and observed water contact in an S. mansoni endemic village in Brazil. Acta Trop 2001; 78:251-9. [PMID: 11311188 DOI: 10.1016/s0001-706x(01)00094-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Estimates of exposure are critical for immuno-epidemiologic and intervention studies in human schistosomiasis. Direct observation of human water contact patterns is both costly and time consuming. To address these issues, we determined whether individuals residing in a Schistosoma mansoni endemic village in Brazil could accurately self-report their water contact patterns. We compared the results of a water contact questionnaire to the present gold standard, direct observation of water contact in 86 volunteers, aged 8--29. We administered a survey to estimate volunteers' frequency and type of water contact and directly measured each volunteers' water contact patterns during 5 weeks of detailed water contact observations. We found a poor correlation between self reported frequency of contact and directly observed exposure (rho=0.119, P=NS). The questionnaire data was supplemented by information about average body surface area of exposure and duration of contact for specific activities derived from observations of this cohort. This 'supplemented questionnaire' data was significantly correlated with their exposure index (rho=0.227, P=0.05). It provides a starting point from which questionnaires may develop to provide a more cost-effective and less labor intensive method of assessing water contact exposure at the level of the individual.
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Affiliation(s)
- J F Friedman
- International Health Institute, Brown University, Box G-B497, Providence, RI 02912, USA.
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28
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Mutapi F, Ndhlovu PD, Hagan P, Woolhouse ME. A comparison of re-infection rates with Schistosoma haematobium following chemotherapy in areas with high and low levels of infection. Parasite Immunol 1999; 21:253-9. [PMID: 10320623 DOI: 10.1046/j.1365-3024.1999.00227.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two groups of children (6-15 years) from a Schistosoma haematobium endemic area were followed for 9 months after praziquantel treatment. Seventy-three children came from an area of high infection while 67 children came from an area of low infection. Pre-treatment infection prevalence in the high infection area (76.6%) was significantly higher than that in low infection area (36.3%). Levels of anti-SEA immunoglobulin (Ig)A and IgM were significantly higher and levels of IgG3 significantly lower in children from the low infection area. Nine months after treatment, infection prevalence was significantly higher in the high infection area (29.0%) (where re-infection rates were higher) than in the low infection area (12.9%). Children from the high infection area were six times more likely to get re-infected than those from the low infection area, while younger children were 30 times more likely to get re-infected than older children. These results are discussed in relation to differences in transmission and the development of acquired immunity. Pre-treatment levels of IgM and the difference between IgE and IgG4 were positively associated with re-infection in the high infection area. These results are discussed in relation to the interpretation of simple correlations between infection and some antibody levels and the inference of causal relationships between observed epidemiological and immunological patterns.
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Affiliation(s)
- F Mutapi
- Wellcome Trust Centre for the Epidemiology of Infectious Diseases, Department of Zoology, South Parks Road, University of Oxford, Oxford, OX1 3PS, UK
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29
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Shaw DJ, Vercruysse J, Picquet M, Sambou B, Ly A. The effect of different treatment regimens on the epidemiology of seasonally transmitted Schistosoma haematobium infections in four villages in the Senegal River Basin, Senegal. Trans R Soc Trop Med Hyg 1999; 93:142-50. [PMID: 10450436 DOI: 10.1016/s0035-9203(99)90288-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
This paper describes the present epidemiological situation of Schistosoma haematobium in 4 villages in the middle valley of the Senegal River Basin, in terms of level and intensity of infection, seasonality of transmission, and intermediate hosts, and the effect of different treatment schedules with praziquantel on the overall infection levels and re-infection rates. The longitudinal study involving 7 surveys was carried out between June 1995 and March 1997 in Diatar, Guia, Donaye and Niandane. The prevalence and intensity of infection remained low throughout the survey (< 55% and < 12 eggs/10 mL urine), and there were no systematic differences in the prevalence or intensity of infection between men and women. Before treatment, infections were highly aggregated in individuals and were concentrated in children (aged < 15 years) with 85% of the potential contamination; no individual aged > 24 years produced > 50 eggs/10 mL urine. Using WHO guidelines mass treatment was given to all Diatar and Guia villagers in December 1995, whereas in Donaye and Niandane only individuals positive for eggs were treated. Six weeks post-treatment cure rates in all villages were > 80%, with marked declines in levels of infection (< 20% and < 4.5 eggs/10 mL). By March 1997 infection levels in Donaye and Niandane had returned to pre-treatment levels, whereas in the 2 mass-treated villages (Diatar and Guia) infection levels were still markedly reduced compared to pre-treatment levels. Rates of conversion were very low between all surveys; however, there was an apparent high level of reversion (> 20%), due to the alternation of individuals apparently positive and negative between surveys. Water and infected snails were present from June to March. Therefore, owing to the high aggregation of infections in children, the low overall infection levels and the transmission period, it is suggested that in this area the best treatment schedule would be selective treatment of school-aged children in March/April, probably on an annual basis.
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Affiliation(s)
- D J Shaw
- Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Belgium
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30
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Ofoezie IE, Asaulu SO, Christensen NO, Madsen H. Patterns of infection with Schistosoma haematobium in lakeside resettlement communities at the Oyan Reservoir in Ogun State, south-western Nigeria. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 1997; 91:187-97. [PMID: 9307661 DOI: 10.1080/00034983.1997.11813129] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Patterns of infection with Schistosoma haematobium were studied in 1991 and 1992 in two, lakeside, resettlement communities at the newly established Oyan Reservoir in Ogun State, Nigeria. Prevalence and intensity of S. haematobium infection and frequency of haematuria and proteinuria all increased markedly from 1991 to 1992, indicating intensive transmission. This was confirmed in an incidence study. In both years, infection patterns were highly age-dependent, with peaks in those aged 10-14 years. These patterns deviate from those seen during a survey carried out in the same communities in 1988, providing strong evidence that infection had changed from an epidemic to an endemic stage. Although sex, tribe, religion, occupation, and village of residence had little if any effect on infection pattern, the patterns in settled and migrant groups differed considerably. The study provided a thorough elucidation of the complexity and instability of transmission of S. haematobium in a resettlement community characterized by social instability and extensive population movements. Although haematuria was very common, the subjects knew little about its cause.
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Affiliation(s)
- I E Ofoezie
- Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife, Nigeria
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31
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Fulford AJ, Ouma JH, Kariuki HC, Thiongo FW, Klumpp R, Kloos H, Sturrock RF, Butterworth AE. Water contact observations in Kenyan communities endemic for schistosomiasis: methodology and patterns of behaviour. Parasitology 1996; 113 ( Pt 3):223-41. [PMID: 8811848 DOI: 10.1017/s0031182000082007] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A descriptive analysis of observed water contact activities in seven Kenyan (Akamba) communities is presented. The patterns of contact with time of day, month of year, type of activity, degree of immersion, use of soap, use of 'kithima' and day of week are all considered, with particular attention given to how these vary with age and sex. It is noted that (a) patterns of contact vary dramatically between these culturally rather similar communities, (b) contact usually peaks in the second decade of life, (c) generally females, especially young women, spend more time at the water than males and (d) simple (unweighted) total observed duration of contact gives a relatively inflated estimate of exposure in adults, especially young women. The methodology of observation and data handling is described in some detail.
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Affiliation(s)
- A J Fulford
- Department of Pathology, University of Cambridge, UK.
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32
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Woolhouse ME, Hasibeder G, Chandiwana SK. On estimating the basic reproduction number for Schistosoma haematobium. Trop Med Int Health 1996; 1:456-63. [PMID: 8765453 DOI: 10.1046/j.1365-3156.1996.d01-88.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Existing estimates of the basic reproduction number, Ro, for human schistosomes are mostly in the range 1-4, implying that schistosomes should be relatively easy to eliminate from endemic areas, which is contrary to practical experience. An estimate of Ro for a site in Zimbabwe is obtained here using a mathematical model explicitly incorporating two features believed to be epidemiologically significant; age-dependent exposure and acquired immunity. Parameter estimates are, as far as possible, obtained independently, but the coefficients representing man-snail and snail-man transmission, as well as parameters representing effects of acquired immunity, must be estimated indirectly by fitting the model to field data. Heterogeneity in human exposure and contamination is crudely incorporated by considering "wormy' and non-wormy' fractions of the population. The results suggest Ro to be in the range 4-5 or more, higher than previous estimates and despite only moderate levels of infection at this site. It is shown that this estimate is sensitive to the form of the underlying model. The application of less realistic models may lead to less reliable estimates of Ro.
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Woolhouse ME, Ndamba J, Bradley DJ. The interpretation of intensity and aggregation data for infections of Schistosoma haematobium. Trans R Soc Trop Med Hyg 1994; 88:520-6. [PMID: 7992326 DOI: 10.1016/0035-9203(94)90144-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The relationships between mean intensities of infection, the aggregation of infection among hosts, and host age are analysed using data from 2 large (> 3000 individuals) field studies of Schistosoma haematobium infection. The data show a convex relationship between mean intensity and age, a convex relationship between an inverse index of aggregation and age, and an age-dependent relationship between the mean and aggregation of infection intensity when levels of infection are high. These patterns are qualitatively compared with the output of mathematical models based on an immigration-death process (model I), and incorporating age-dependent changes in the distribution of exposure to infection as suggested by field data (model II), or reductions in the rate of infection as a function of either current (model III) or cumulative (model IV) parasite burdens, that is, density-dependent processes without or with memory, respectively. Models II and III were able to reproduce observed patterns, but model IV, which is a possible representation of acquired immunity, was not. These results are consistent with the following assumptions: (i) age-related patterns of aggregation can be generated without recourse to density-dependent processes; (ii) the epidemiological impact of density-dependent processes depends on whether these act with or without memory; and (iii) any acquired immunity to human S. haematobium infection may be significantly less than life-long.
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Woolhouse ME. A theoretical framework for the immunoepidemiology of blocking antibodies to helminth infection. Parasite Immunol 1994; 16:415-24. [PMID: 7808762 DOI: 10.1111/j.1365-3024.1994.tb00369.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Epidemiological evidence is widely cited in support of the hypothesis that certain antibody responses to human helminth, especially schistosome, infection exhibit blocking activity. This evidence includes positive correlations between antibody levels and the rate of re-establishment of infection following chemotherapy, antibody levels which peak in younger and more susceptible age classes, lower ratios of blocking antibodies to others in older and less susceptible age classes. In this paper simple mathematical models are used to explore expected age-specific relationships between antibody levels, parasite burdens and re-establishment rates for different combinations of protective, neutral and blocking immune responses. In general, all the above cited patterns may be generated without invoking blocking activity, especially if the abilities to produce different antibody responses have different immunological memories, i.e. persist for different lengths of time in the absence of continued exposure to antigen. None of these patterns, including a positive correlation between antibody levels and rates of re-establishment following chemotherapy, offers unambiguous evidence for blocking activity. Blocking activity is also predicted to affect the shape of the age-intensity curve and the relationship between susceptibility to infection and age in ways which are not necessarily consistent with the epidemiological evidence. The importance of the blocking activity, which has been convincingly demonstrated in vitro, to population level immunoepidemiological patterns in the field therefore remains uncertain.
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Needham CS, Lillywhite JE, Didier JM, Bianco AE, Bundy DA. Age-dependency of serum isotype responses and antigen recognition in human whipworm (Trichuris trichiura) infection. Parasite Immunol 1993; 15:683-92. [PMID: 7533282 DOI: 10.1111/j.1365-3024.1993.tb00583.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The present study examines the age-dependency of parasite-specific isotype responses and antigen recognition profiles of individuals within a Trichuris trichiura endemic community, in order to evaluate the significance of serum antibodies as determinants of observed age-related patterns of infection intensity. A high degree of individual heterogeneity is observed in isotype responses to separated T. trichiura antigens by Western blot. Recognition by IgG1 antibodies exhibits marked age-dependency. The age-profiles of IgG1 responses to selected antigens of 16-17 kDa and 90 kDa molecular weight reflect the age-related changes in current infection intensity at the population level. Similarly, mean age patterns of IgG2 responses to a 90 kDa antigen, and mean IgG4 responses to a 16-17 kDa antigen reflect mean infection levels. IgG3 responses are negligible, and for methodological reasons, both IgE and IgM specificities are not presented. IgA responses to separated antigens of 16-17 kDa and 90 kDa, exhibit age-profiles which may suggest the development of an IgA-mediated acquired resistance to T. trichiura with age. IgA levels remain elevated throughout early adulthood, when infection intensity levels markedly decrease, supporting the hypothesis that IgA antibodies may be significant in generating the convex nature of the age-infection profile of T. trichiura.
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Affiliation(s)
- C S Needham
- Wellcome Research Centre for Parasitic Infections, Department of Biology, Imperial College, London, UK
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Maizels RM, Bundy DA, Selkirk ME, Smith DF, Anderson RM. Immunological modulation and evasion by helminth parasites in human populations. Nature 1993; 365:797-805. [PMID: 8413664 DOI: 10.1038/365797a0] [Citation(s) in RCA: 402] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Helminth parasites are highly prevalent in human communities in developing countries. In an endemic area an infected individual may harbour parasitic worms for most of his or her life, and the ability of these infections to survive immunological attack has long been a puzzle. But new techniques are starting to expose the diverse mechanisms by which these agents modulate or evade their hosts' defences, creating a dynamic interaction between the human immune system and the parasite population.
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Affiliation(s)
- R M Maizels
- Wellcome Research Centre for Parasitic Infections, Department of Biology, Imperial College of Science, Technology and Medicine, London, UK
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38
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Woolhouse ME. A theoretical framework for immune responses and predisposition to helminth infection. Parasite Immunol 1993; 15:583-94. [PMID: 7877835 DOI: 10.1111/pim.1993.15.10.583] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Many field studies of human helminth infections have reported a positive correlation between parasite burdens and the rate of re-establishment of infection following chemotherapy, i.e., predisposition. Some studies have also reported the relationships between re-establishment and exposure and immune responses. The interpretation of these data is made difficult by the complexity of the underlying immunoepidemiological processes. In this paper, simple mathematical models are used to explore expected patterns, especially in relation to host age. These patterns are determined by rates of infection, parasite life expectancy, the level of immunological responsiveness, the duration of immunological memory, and may be greatly affected by the immunogenic roles of different parasite stages. In general, acquired immunity is predicted to reduce the degree of predisposition. This reduction is age-dependent and may generate 'negative predisposition' in some age classes. Age-dependent reductions in the correlation between re-establishment and exposure are also predicted. The correlation between re-establishment and protective immune responses is also predicted to be age-dependent, but may remain positive for all ages despite significant acquired immunity. The results suggest that great care is needed in the interpretation of immunoepidemiological data from treatment-reinfection studies.
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Abstract
Field studies of parasitic helminths in endemically infected human communities have provided quantitative information on the relationships between parasite burdens, immune responses and age. There are considerable difficulties in the interpretation of these immunoepidemiological data due to the complexities of the biological processes generating the observed patterns. In this paper simple mathematical models are used to explore the expected patterns of variation with host age in parasite burdens, the aggregation of parasites among hosts, levels of immune response, and the correlation between parasite burdens and immune responses. These relationships reflect rates of infection, rates of parasite mortality, the strength of the immune response, and the duration of immunological memory. The models generate some complex and counterintuitive patterns. The analysis suggests that some of these patterns might serve to (i) distinguish effects due to acquired immunity from effects due to age-dependent exposure, (ii) identify potentially protective immune responses, and (iii) identify the parasite stages important in the development of acquired immunity. The results imply that previous analyses of immunoepidemiological data may have been overly simplistic and, especially, that patterns believed to be inconsistent with protective immunity may have been incorrectly interpreted.
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Needham CS, Bundy DA, Lillywhite JE, Didier JM, Simmons I, Bianco AE. The relationship between Trichuris trichiura transmission intensity and the age-profiles of parasite-specific antibody isotypes in two endemic communities. Parasitology 1992; 105 ( Pt 2):273-83. [PMID: 1454425 DOI: 10.1017/s0031182000074205] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study compares parasite-specific antibody responses in two Caribbean communities with high and low levels of Trichuris trichiura transmission. The age-dependency of antibody levels suggest that IgG1 and IgG2 levels relate to the current intensity of infection (as assessed by density of eggs in stool (e.p.g.) and reflect the age-intensity profile at the population level. IgG4, IgE and IgA levels persist into early adulthood and the subsequent decline is gradual. In the low transmission area, lower infection levels are reflected in lower parasite-specific antibody levels (of all isotypes) in the community as a whole. Despite a significantly greater past experience of infection in the high transmission area, antibody levels are not maintained at significantly higher levels throughout adulthood. The production of IgA appears to require a threshold for triggering, and a vigorous IgA response is maintained into early adulthood only in the high transmission village where peak intensity is greatest and the age-convexity of intensity is most marked. Experimental and theoretical studies focusing on the dynamic nature of host-helminth interactions in hosts exposed to high and low infection levels, and the putative role of acquired immunity, are discussed in relation to the data presented.
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Affiliation(s)
- C S Needham
- Department of Biology, Imperial College, London, U.K
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Abstract
In this review Paul Hagan will focus on the results of the reinfection studies that have been completed on Schistosoma mansoni in Kenya and Brazil and on S. haematobium in The Gambia. The review will also draw on the data from other immunological, molecular and epidemiological studies that have provided information that may be relevant to an understanding of immunity in human schistosomiasis. No attempt will be made to describe the latest advances that have been reported from studies of the animal models of schistosomiasis; these are adequately dealt with elsewhere.
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Affiliation(s)
- P Hagan
- Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 IAA, UK
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Chandiwana SK, Woolhouse ME. Heterogeneities in water contact patterns and the epidemiology of Schistosoma haematobium. Parasitology 1991; 103 Pt 3:363-70. [PMID: 1780173 DOI: 10.1017/s0031182000059874] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Variations in the amount of water contact made by individuals and in the amount of water contact made at different sites may have significant impacts on patterns of human schistosome infection. Previous studies have reported variations in the rate of water contact and differences in the sites used between age/sex classes, but there is limited information on variations in individual water contact behaviour. In this paper we report and analyse observations of essentially all water contacts made over a two week period by all individuals in a rural community in eastern Zimbabwe. The mean rate of water contact was 0.43 contacts/person/day. These data were over-dispersed, ranging from zero to 3.3 contacts/person/day; 90% of contacts were made by only 37% of the population. Contact rates were related to age (highest in 8 to 10-year-olds) but not sex, with substantial variation unaccounted for by these variables. Age and sex classes differed in types of water-related activities and the time of day of contact. A greater diversity of sites was used by children than by adults and by males than by females. Individual contact rates were correlated with intensities of infection, although the risk of infection per contact was estimated to be highest in 2 to 4-year-old children and higher for males than females. Five contact sites were used during the study period, with more than 50% of contacts occurring at just 2 sites. Different age and sex classes used different sites and there were additional site-related differences in types of activity and the time of day of use. The implications of these water contact patterns for schistosome epidemiology are discussed. In particular the results provide strong quantitative support for control programmes aimed at heavily used sites (e.g. focal mollusciciding) or at the minority of individuals making most water contacts (e.g. targeted chemotherapy).
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Woolhouse ME. On the application of mathematical models of schistosome transmission dynamics. I. Natural transmission. Acta Trop 1991; 49:241-70. [PMID: 1684260 DOI: 10.1016/0001-706x(91)90077-w] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The many mathematical models of the transmission dynamics of schistosomes that have been published since 1965 have had little impact on field studies or on the design of schistosome control programmes. At least in part, this is due to limited interaction between theoretician and field worker, resulting in unrealistic models that are not easily applied to field data. This review aims to make explicit the assumptions and limitations of existing models and their relationships with field data. A basic model is described which considers the mean number of schistosomes per person and the prevalence of patent infections of snails. Various modifications to this model are introduced. These include: prepatent infections of snails; loss of infection of snails; the effects of snail population dynamics; the effects of miracidia and cercariae population dynamics; miracidia searching efficiency; reservoir hosts; heterogeneous patterns of transmission; seasonality; and predisposition to infection. Variation in levels of infection with age and the effects of acquired immunity to infection are also considered. Published models of schistosome transmission dynamics are reviewed within this framework. Approaches to the modelling of schistosome control measures are considered in a companion paper. It is suggested that future theoretical studies give greater attention to the details of snail population dynamics, heterogeneous patterns of transmission and the effects of acquired immunity. There is a need for field studies explicitly designed to provide estimates of transmission parameters and for studies of the epidemiological effects of acquired immunity.
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Woolhouse ME, Watts CH, Chandiwana SK. Heterogeneities in transmission rates and the epidemiology of schistosome infection. Proc Biol Sci 1991; 245:109-14. [PMID: 1682933 DOI: 10.1098/rspb.1991.0095] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Previous theoretical studies have suggested that heterogeneities in transmission rates can have significant effects on the epidemiology of parasite infections. However, the magnitude of these effects in practice remains uncertain because of the difficulty of quantifying such heterogeneities under natural conditions. In this paper we consider the effects of heterogeneous rates of contact with infective water bodies on the basic reproductive rate, R0, of human schistosomes. In particular, we examine the theoretical effects of differences in the distribution of contacts among individuals and among sites. We find that an individual's contribution to R0 depends not only on the net contact rate but also on how these contacts are distributed among sites--the contact pattern. Our analysis of field data suggests a substantial impact of heterogeneous contact rates on R0 in practice. Significant reductions in R0 may be possible if schistosomiasis control efforts are targeted at certain sites and, especially, certain individuals.
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Woolhouse ME, Taylor P, Matanhire D, Chandiwana SK. Acquired immunity and epidemiology of Schistosoma haematobium. Nature 1991; 351:757-9. [PMID: 1905786 DOI: 10.1038/351757a0] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Human immune responses to schistosome infection have been characterized in detail. But there has been controversy over the relative importance of ecological factors (variation in exposure to infection) and immunological factors (acquired immunity) in determining the relationships between levels of infection and age typically found in areas where infection is endemic. Independent effects of exposure and age on the rates of reinfection with Schistosoma haematobium after chemotherapy have been demonstrated in the Gambia and Zimbabwe. This age effect could be the result of acquired immunity to infection. Indeed, allowing for variation in exposure and age, low rates of reinfection in the Gambia are correlated with high amounts of specific IgE antibodies--human IgE can kill S. mansoni schistosomulae in vitro. Further, animals can acquire immunologically mediated resistance to S. mansoni infection, although nonimmunological factors could also be involved. Acquisition of this immunity seems to be related to the cumulative effects of repeated infection and provides only partial protection. These characteristics are consistent with immuno-epidemiological data for both S. mansoni and S. haematobium infections of humans. We have now analysed age-prevalence data for human infection with S. haematobium, and find patterns of variation that are indeed consistent with the epidemiological effects of acquired immunity predicted by mathematical models.
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