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Kabululu ML, Johansen MV, Lightowlers M, Trevisan C, Braae UC, Ngowi HA. Aggregation of Taenia solium cysticerci in pigs: Implications for transmission and control. Parasite Epidemiol Control 2023; 22:e00307. [PMID: 37261135 PMCID: PMC10227459 DOI: 10.1016/j.parepi.2023.e00307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 04/02/2023] [Accepted: 05/19/2023] [Indexed: 06/02/2023] Open
Abstract
Parasite aggregation within hosts is a fundamental feature of parasite distributions, whereby the majority of parasites are harboured by a minority of hosts. Parasite aggregation can influence their transmission and hence control. In this narrative review, possible sources of aggregation of Taenia solium cysticerci in pigs are discussed, along with implications for control of the parasite. While heavy T. solium infections in pigs could most likely be associated with ingestion of high doses of infective parasite eggs, consistent with coprophagic behaviour of pigs, lighter infections indicate a role of indirect routes of transmission to pigs, mostly from lower infection doses. Light infections are likely to be missed by commonly used diagnostic methods - tongue examination or meat inspection - and end up in the food chain. Hence, they entail a 'hidden' risk and are of a particular public health concern, especially in areas where meat is consumed raw or undercooked. To be effective and sustainable, control strategies against T. solium likely require a broader understanding of, and consideration for parasite transmission dynamics. More importantly, a holistic One Health approach incorporating interventions on humans, pigs and the environment will likely have a larger, more successful and sustainable impact.
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Affiliation(s)
| | | | - Marshall Lightowlers
- Department of Biosciences, Melbourne Veterinary School, University of Melbourne, Werribee, Victoria, Australia
| | - Chiara Trevisan
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
- Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Uffe C. Braae
- One Health Center for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine, Basseterre, Saint Kitts and Nevis
| | - Helena A. Ngowi
- Department of Veterinary Medicine and Public Health, College of Veterinary Medicine and Biomedical Sciences, Sokoine University of Agriculture, Morogoro, Tanzania
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Gonzales-Gustavson E, Pray IW, Gamboa R, Muro C, Vilchez P, Gomez-Puerta L, Vargas-Calla A, Bonnet G, Pizzitutti F, Garcia HH, Gonzalez AE, O’Neal SE. Evaluating the Role of Corrals and Insects in the Transmission of Porcine Cysticercosis: A Cohort Study. Pathogens 2023; 12:597. [PMID: 37111483 PMCID: PMC10143142 DOI: 10.3390/pathogens12040597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 04/05/2023] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
The widespread dispersion of pigs infected with cysticercosis across endemic villages, low cyst burden among infected pigs, and low prevalence of taeniasis all suggest that pig ingestion of human feces is not the only mode of transmission for Taenia solium. Our objective was to evaluate the risk of porcine cysticercosis associated with exposure to human feces, dung beetles, and flies in an endemic community setting. We used a cluster-randomized cohort design to compare the risk of developing antibodies and infection among 120 piglets raised in either free-roaming (FR), standard corral (SC), or netted corral environments (NC). We collected monthly blood samples to detect serum antibodies and necropsied all pigs after 10 months to identify cysts. A total of 66 piglets developed antibodies with the relative risk of seropositivity in FR vs. all corralled pigs increasing significantly after 18 weeks. Of 108 necropsied pigs, 15 had T. solium cysts, all belonging to the FR group. Corrals were protective against infection but less so against seropositivity. NC, which did not completely exclude insects, did not provide added protection against seropositivity as compared to SC. The results of this study suggest that dung beetles and flies do not play an important role in infection.
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Affiliation(s)
- Eloy Gonzales-Gustavson
- Departamento de Salud Animal y Salud Pública, Universidad Nacional Mayor de San Marcos, Lima 15081, Peru
| | - Ian W. Pray
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, OR 97239, USA
| | - Ricardo Gamboa
- Center of Global Health, Universidad Peruana Cayetano Heredia, Lima 15202, Peru
| | - Claudio Muro
- Center of Global Health, Universidad Peruana Cayetano Heredia, Lima 15202, Peru
| | - Percy Vilchez
- Center of Global Health, Universidad Peruana Cayetano Heredia, Lima 15202, Peru
| | - Luis Gomez-Puerta
- Departamento de Salud Animal y Salud Pública, Universidad Nacional Mayor de San Marcos, Lima 15081, Peru
| | - Ana Vargas-Calla
- Departamento de Salud Animal y Salud Pública, Universidad Nacional Mayor de San Marcos, Lima 15081, Peru
| | - Gabrielle Bonnet
- Centre for the Mathematical Modeling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London WC1H 9SH, UK
| | | | - Hector H. Garcia
- Center of Global Health, Universidad Peruana Cayetano Heredia, Lima 15202, Peru
- Cysticercosis Unit, National Institute of Neurological Sciences, Lima 15003, Peru
| | - Armando E. Gonzalez
- Departamento de Salud Animal y Salud Pública, Universidad Nacional Mayor de San Marcos, Lima 15081, Peru
| | - Seth E. O’Neal
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, OR 97239, USA
- Center of Global Health, Universidad Peruana Cayetano Heredia, Lima 15202, Peru
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Larkins A, Bruce M, Ash A. A Spatial Autocorrelation Method for Taenia solium Risk Mapping: The Case of Lao PDR. Trop Med Infect Dis 2023; 8:tropicalmed8040221. [PMID: 37104347 PMCID: PMC10146971 DOI: 10.3390/tropicalmed8040221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/06/2023] [Accepted: 04/09/2023] [Indexed: 04/28/2023] Open
Abstract
BACKGROUND The World Health Organization has identified Taenia solium mapping tools as an important development for intensifying control in hyperendemic areas. Taenia solium has also been identified as a priority by the Lao PDR government. There is a limited understanding of the distribution of T. solium due to inherent diagnostic challenges. METHOD Global and local autocorrelation statistics were applied to available risk factor data sourced from national censuses to map the risk of Taenia solium in Lao PDR. RESULTS Approximately 50% of villages could be considered hot spots for one or more risk factors. Different risk factor hot spots co-occurred in 30% of villages. Twenty per cent of villages were classified as hot spots for the proportion of households owning pigs and another risk factor. Northern Lao PDR was the dominant high-risk area. This is consistent with passive reports, limited surveys, and anecdotal reports. One smaller area in southern Lao PDR was also identified as high-risk. This is of particular interest because T. solium has not previously been investigated in this area. CONCLUSIONS The methods applied provide a simple, rapid, and versatile approach that allows endemic countries to begin mapping the risk of T. solium at a sub-national level.
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Affiliation(s)
- Andrew Larkins
- School of Medical, Molecular and Forensic Sciences, Murdoch University, Perth, WA 6150, Australia
- Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, WA 6150, Australia
| | - Mieghan Bruce
- Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, WA 6150, Australia
- School of Veterinary Medicine, Murdoch University, Perth, WA 6150, Australia
| | - Amanda Ash
- School of Medical, Molecular and Forensic Sciences, Murdoch University, Perth, WA 6150, Australia
- Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, WA 6150, Australia
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Van Damme I, Pray I, Mwape KE, Trevisan C, Coudenys F, Mubanga C, Mwelwa C, Vaernewyck V, Dorny P, O'Neal SE, Gabriël S. Movements of free-range pigs in rural communities in Zambia: an explorative study towards future ring interventions for the control of Taenia solium. Parasit Vectors 2022; 15:150. [PMID: 35477431 PMCID: PMC9044682 DOI: 10.1186/s13071-022-05264-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 03/30/2022] [Indexed: 11/13/2022] Open
Abstract
Background Taenia solium typically affects resource-poor communities where pigs are allowed to roam freely, and sanitation and hygiene levels are suboptimal. Sustainable, long-term strategies are urgently needed to control the disease. Geographically targeted interventions, i.e. screening or treatment of taeniosis among people living near infected pigs (defined as ring screening and ring treatment, respectively), have been shown to be effective control options in Peru. However, these results might not be directly generalizable to sub-Saharan African settings. Pig movements play a vital role in the transmission and, consequently, the success of ring interventions against T. solium. The aim of the present study was to explore roaming patterns of pigs in T. solium endemic communities in Zambia as a first step toward evaluating whether ring interventions should be considered as a treatment option in Zambia. Methods In total, 48 free-roaming pigs in two rural neighborhoods in the Eastern Province of Zambia were tracked using a Global Positioning System (GPS) receiver. Tracking took place in April (end of the rainy season) 2019 and October (end of the dry season) 2019. The number of revisitations and the time spent within rings of different radii (50, 100 and 250 m) around the coordinates of each pig owner’s household were calculated for each pig. Results The total tracking time for 43 pigs in the final analysis set ranged between 43 and 94 h. Pigs spent a median of 31% and 13% of the tracked time outside the 50- and 100-m radius, respectively, although large variations were observed between pigs. Overall, 25 pigs (58%) went outside the 250-m ring at least once, and individual excursions lasting up to 16 h were observed. In the dry season, 17 out of 23 pigs went outside the 250-m radius compared to only eight out of 20 pigs in the rainy season (P = 0.014). Conclusions In our study sites in Zambia, the majority of pigs spent most of their time within 50 or 100 m of their owner’s home, and these results are comparable with those on Peruvian pigs. Both radii could therefore be considered reasonable options in future ring interventions. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05264-0.
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Affiliation(s)
- Inge Van Damme
- Laboratory of Foodborne Parasitic Zoonoses, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium
| | - Ian Pray
- School of Public Health, Oregon Health & Science University-Portland State University, Portland, USA
| | - Kabemba E Mwape
- Department of Clinical Studies, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Chiara Trevisan
- Laboratory of Foodborne Parasitic Zoonoses, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.,Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Fien Coudenys
- Laboratory of Foodborne Parasitic Zoonoses, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium
| | - Chishimba Mubanga
- Department of Clinical Studies, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Chembesofu Mwelwa
- Department of Clinical Studies, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Victor Vaernewyck
- Laboratory of Foodborne Parasitic Zoonoses, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium
| | - Pierre Dorny
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Seth E O'Neal
- School of Public Health, Oregon Health & Science University-Portland State University, Portland, USA.,Center for Global Health-Tumbes, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Sarah Gabriël
- Laboratory of Foodborne Parasitic Zoonoses, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
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Pray IW, Pizzitutti F, Bonnet G, Gonzales-Gustavson E, Wakeland W, Pan WK, Lambert WE, Gonzalez AE, Garcia HH, O’Neal SE. Validation of a spatial agent-based model for Taenia solium transmission ("CystiAgent") against a large prospective trial of control strategies in northern Peru. PLoS Negl Trop Dis 2021; 15:e0009885. [PMID: 34705827 PMCID: PMC8575314 DOI: 10.1371/journal.pntd.0009885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 11/08/2021] [Accepted: 10/08/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The pork tapeworm (Taenia solium) is a parasitic helminth that imposes a major health and economic burden on poor rural populations around the world. As recognized by the World Health Organization, a key barrier for achieving control of T. solium is the lack of an accurate and validated simulation model with which to study transmission and evaluate available control and elimination strategies. CystiAgent is a spatially-explicit agent based model for T. solium that is unique among T. solium models in its ability to represent key spatial and environmental features of transmission and simulate spatially targeted interventions, such as ring strategy. METHODS/PRINCIPAL FINDINGS We validated CystiAgent against results from the Ring Strategy Trial (RST)-a large cluster-randomized trial conducted in northern Peru that evaluated six unique interventions for T. solium control in 23 villages. For the validation, each intervention strategy was replicated in CystiAgent, and the simulated prevalences of human taeniasis, porcine cysticercosis, and porcine seroincidence were compared against prevalence estimates from the trial. Results showed that CystiAgent produced declines in transmission in response to each of the six intervention strategies, but overestimated the effect of interventions in the majority of villages; simulated prevalences for human taenasis and porcine cysticercosis at the end of the trial were a median of 0.53 and 5.0 percentages points less than prevalence observed at the end of the trial, respectively. CONCLUSIONS/SIGNIFICANCE The validation of CystiAgent represented an important step towards developing an accurate and reliable T. solium transmission model that can be deployed to fill critical gaps in our understanding of T. solium transmission and control. To improve model accuracy, future versions would benefit from improved data on pig immunity and resistance, field effectiveness of anti-helminthic treatment, and factors driving spatial clustering of T. solium infections including dispersion and contact with T. solium eggs in the environment.
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Affiliation(s)
- Ian W. Pray
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, United States of America
| | - Francesco Pizzitutti
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, United States of America
| | - Gabrielle Bonnet
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, United States of America
| | - Eloy Gonzales-Gustavson
- Tropical and Highlands Veterinary Research Institute, School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, EL Mantaro, Peru
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Wayne Wakeland
- Systems Science Program, Portland State University, Portland, Oregon, United States of America
| | - William K. Pan
- Duke Global Health Institute & Nicholas School of Environment, Duke University, Durham, North Carolina, United States of America
| | - William E. Lambert
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, United States of America
| | - Armando E. Gonzalez
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Hector H. Garcia
- School of Sciences, Department of Microbiology, Universidad Peruana Cayetano Heredia, Lima, Peru
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
| | - Seth E. O’Neal
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, United States of America
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
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Alarcon P, Dominguez-Salas P, Fèvre EM, Rushton J. The Importance of a Food Systems Approach to Low and Middle Income Countries and Emerging Economies: A Review of Theories and Its Relevance for Disease Control and Malnutrition. FRONTIERS IN SUSTAINABLE FOOD SYSTEMS 2021. [DOI: 10.3389/fsufs.2021.642635] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Our review explores the changing food production, distribution and consumption environment in low and middle-income countries and emerging economies as a basis for framing how to study food systems in order to address public health issues of food safety and nutrition. It presents the state of knowledge on existing food systems science and its use in terms of sustainable actions for food safety and public health. The review identifies a knowledge gap in food system mapping and governance, with value chain mapping of key commodities often missing. Despite a number of initiatives, the application of food systems methods is highly variable in scope and quality. Most analyses concentrate on specific commodities, rarely taking into account the need for a whole diet approach when looking at nutrition or the assessment of a range of infectious agents and their interactions when looking at food safety. Of the studies included in the review there is a growing observation of “informal” food systems, a term used inconsistently and one that requires revision. “Informal” food systems link to the formal sector to provide food security, yet with trade-offs between economic efficiencies and food safety. Efforts to improve food safety are hampered by inadequate food safety capacities and a lack of policy coherence leading to: inadequate investment; fragmented food quality control systems; weak or non-existent traceability mechanisms; weak foodborne disease surveillance; obsolete food regulation; and weak regulatory enforcement. In-depth food systems assessments can complement risk analysis to identify risky behaviors and understand institutional settings in order to improve codes of practice and enforcement. Methods for looking at food safety from a food systems perspective are emerging, yet existing nutrition and food systems science are not advancing sufficiently in response to nutritional public health problems. There is an urgency for improved understanding of the structure and drivers of the food systems, for better planning of changes that leads to nutrients access and healthy levels of eating. It is proposed that countries and international institutions provide an atlas of food system maps for the key commodities based on an agreed common methodology and developed by multidisciplinary teams.
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Dixon MA, Winskill P, Harrison WE, Basáñez MG. Taenia solium taeniasis/cysticercosis: From parasite biology and immunology to diagnosis and control. ADVANCES IN PARASITOLOGY 2021; 112:133-217. [PMID: 34024358 DOI: 10.1016/bs.apar.2021.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Infection with the pork tapeworm (Taenia solium) is responsible for a substantial global burden of disease, not only restricted to its impact on human health, but also resulting in a considerable economic burden to smallholder pig farmers due to pig cysticercosis infection. The life-cycle, parasitology and immunology of T. solium are complex, involving pigs (the intermediate host, harbouring the larval metacestode stage), humans (the definitive host, harbouring the adult tapeworm, in addition to acting as accidental intermediate hosts) and the environment (the source of infection with eggs/proglottids). We review the parasitology, immunology, and epidemiology of the infection associated with each of the T. solium life-cycle stages, including the pre-adult/adult tapeworm responsible for human taeniasis; post-oncosphere and cysticercus associated with porcine and human cysticercosis, and the biological characteristics of eggs in the environment. We discuss the burden associated, in endemic settings, with neurocysticercosis (NCC) in humans, and the broader cross-sectoral economic impact associated both with NCC and porcine cysticercosis, the latter impacting food-value chains. Existing tools for diagnostics and control interventions that target different stages of the T. solium transmission cycle are reviewed and their limitations discussed. Currently, no national T. solium control programmes have been established in endemic areas, with further work required to identify optimal strategies according to epidemiological setting. There is increasing evidence suggesting that cross-sectoral interventions which target the parasite in both the human and pig host provide the most effective approaches for achieving control and ultimately elimination. We discuss future avenues for research on T. solium to support the attainment of the goals proposed in the revised World Health Organisation neglected tropical diseases roadmap for 2021-2030 adopted at the 73rd World Health Assembly in November 2020.
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Affiliation(s)
- Matthew A Dixon
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, London, United Kingdom; MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, London, United Kingdom; Schistosomiasis Control Initiative Foundation (SCI Foundation), London, United Kingdom
| | - Peter Winskill
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, London, United Kingdom
| | - Wendy E Harrison
- Schistosomiasis Control Initiative Foundation (SCI Foundation), London, United Kingdom
| | - Maria-Gloria Basáñez
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, London, United Kingdom; MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, London, United Kingdom.
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Pesantes MA, Moyano LM, Sommerville C. Neurocysticercosis in Northern Peru: Qualitative Insights from men and women about living with seizures. PLoS Negl Trop Dis 2020; 14:e0008715. [PMID: 33035212 PMCID: PMC7577431 DOI: 10.1371/journal.pntd.0008715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 10/21/2020] [Accepted: 08/14/2020] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Neurocysticercosis (NCC) is a helminthic disease of the central nervous system, and it is one of the leading causes of seizures and symptomatic epilepsy in countries with tropical regions like Peru. Studies of people with epilepsy in Peru's northern coast have consistently found that between 30% and 50% of epilepsy cases is associated with NCC. There are few studies that report on the differences in incidence and prevalence of NCC by sex, and to our knowledge, none that consider the gendered dimensions of having epilepsy. METHODOLOGY This qualitative study based on individual interviews (n = 9) and focus group discussions (n = 12) explored the challenges of diagnosis and the implications for everyday activities among men and women with epilepsy as well as the views of their family members on the impact of such condition. PRINCIPAL FINDINGS The explanatory models used by women to discuss their condition reflect low levels of decision-making power in areas such a reproductive health, health care access and treatment. For some women domestic violence is also a probable cause for seizures among women. The implications of living with neurocysticercosis and the accompanying seizures were reported differently by men and women. While women were mostly concerned about their capacity to perform their domestic responsibilities and their roles as mothers and caregivers; men were mostly concerned about the impact on their income generation activities. Women and men shared concern about the consequences of their condition on the wellbeing of their families. CONCLUSIONS/SIGNIFICANCE NCC is a disrupting experience for men and women in ways that reflect their position and roles in society: Women as caregivers within the home, men as income generators outside the home. Further gender research is needed to better understand and address the differential impacts of NCC and health system responses as well as gendered dimensions of prevalence and incidence. (268 words).
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Affiliation(s)
- Maria Amalia Pesantes
- CRONICAS, Centre of Excellence in Chronic Conditions, Universidad Peruana Cayetano Heredia, Miraflores, Lima, Peru
| | - Luz Maria Moyano
- Center for Global Health, Tumbes Facilities, Universidad Peruana Cayetano Heredia, Puerto el Cura Pizarro, Tumbes, Peru
| | - Claire Sommerville
- Gender Centre, Graduate Institute of International and Development Studies, Switzerland
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Pray IW, Wakeland W, Pan W, Lambert WE, Garcia HH, Gonzalez AE, O'Neal SE. Understanding transmission and control of the pork tapeworm with CystiAgent: a spatially explicit agent-based model. Parasit Vectors 2020; 13:372. [PMID: 32709250 PMCID: PMC7379812 DOI: 10.1186/s13071-020-04226-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 07/14/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The pork tapeworm, Taenia solium, is a serious public health problem in rural low-resource areas of Latin America, Africa and Asia, where the associated conditions of nuerocysticercosis (NCC) and porcine cysticercosis cause substantial health and economic harms. An accurate and validated transmission model for T. solium would serve as an important new tool for control and elimination, as it would allow for comparison of available intervention strategies, and prioritization of the most effective strategies for control and elimination efforts. METHODS We developed a spatially-explicit agent-based model (ABM) for T. solium ("CystiAgent") that differs from prior T. solium models by including a spatial framework and behavioral parameters such as pig roaming, open human defecation, and human travel. In this article, we introduce the structure and function of the model, describe the data sources used to parameterize the model, and apply sensitivity analyses (Latin hypercube sampling-partial rank correlation coefficient (LHS-PRCC)) to evaluate model parameters. RESULTS LHS-PRCC analysis of CystiAgent found that the parameters with the greatest impact on model uncertainty were the roaming range of pigs, the infectious duration of human taeniasis, use of latrines, and the set of "tuning" parameters defining the probabilities of infection in humans and pigs given exposure to T. solium. CONCLUSIONS CystiAgent is a novel ABM that has the ability to model spatial and behavioral features of T. solium transmission not available in other models. There is a small set of impactful model parameters that contribute uncertainty to the model and may impact the accuracy of model projections. Field and laboratory studies to better understand these key components of transmission may help reduce uncertainty, while current applications of CystiAgent may consider calibration of these parameters to improve model performance. These results will ultimately allow for improved interpretation of model validation results, and usage of the model to compare available control and elimination strategies for T. solium.
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Affiliation(s)
- Ian W Pray
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, OR, USA.
| | - Wayne Wakeland
- Systems Science Program, Portland State University, Portland, OR, USA
| | - William Pan
- Global Health Institute, Duke University, Durham, NC, USA
| | - William E Lambert
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, OR, USA
| | - Hector H Garcia
- School of Sciences, Department of Microbiology, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Armando E Gonzalez
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Seth E O'Neal
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, OR, USA
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Garcia HH, Gonzalez AE, Gilman RH. Taenia solium Cysticercosis and Its Impact in Neurological Disease. Clin Microbiol Rev 2020; 33:e00085-19. [PMID: 32461308 PMCID: PMC7254859 DOI: 10.1128/cmr.00085-19] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Taenia solium neurocysticercosis (NCC) is endemic in most of the world and contributes significantly to the burden of epilepsy and other neurological morbidity. Also present in developed countries because of immigration and travel, NCC is one of few diseases targeted for eradication. This paper reviews all aspects of its life cycle (taeniasis, porcine cysticercosis, human cysticercosis), with a focus on recent advances in its diagnosis, management, and control. Diagnosis of taeniasis is limited by poor availability of immunological or molecular assays. Diagnosis of NCC rests on neuroimaging findings, supported by serological assays. The treatment of NCC should be approached in the context of the particular type of infection (intra- or extraparenchymal; number, location, and stage of lesions) and has evolved toward combined symptomatic and antiparasitic management, with particular attention to modulating inflammation. Research on NCC and particularly the use of recently available genome data and animal models of infection should help to elucidate mechanisms of brain inflammation, damage, and epileptogenesis.
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Affiliation(s)
- Hector H Garcia
- Center for Global Health, Universidad Peruana Cayetano Heredia, Lima, Peru
- Cysticercosis Unit, Instituto Nacional de Ciencias Neurológicas, Lima, Peru
| | - Armando E Gonzalez
- Center for Global Health, Universidad Peruana Cayetano Heredia, Lima, Peru
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Robert H Gilman
- Department of International Health, Johns Hopkins School of Public Health, Baltimore, Maryland, USA
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Lescano AG, Pray IW, Gonzalez AE, Gilman RH, Tsang VCW, Gamboa R, Guezala MC, Aybar V, Rodriguez S, Moulton LH, Leontsini E, Gonzalvez G, O'Neal SE, Garcia HH, For The Cysticercosis Working Group In Peru. Clustering of Necropsy-Confirmed Porcine Cysticercosis Surrounding Taenia solium Tapeworm Carriers in Peru. Am J Trop Med Hyg 2019; 100:314-322. [PMID: 30560769 DOI: 10.4269/ajtmh.18-0296] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The pork tapeworm, Taenia solium, is among the leading causes of preventable epilepsy in the world and is common in rural areas of developing countries where sanitation is limited and pigs have access to human feces. Prior studies in rural villages of Peru have observed clusters of T. solium cysticercosis among pigs that live near human tapeworm carriers. Such spatial analyses, however, have been limited by incomplete participation and substandard diagnostic tests. In this study, we evaluated the association between necropsy-confirmed cysticercosis in pigs and their distance to T. solium tapeworm carriers in six villages in northern Peru. A total of six (1.4%) tapeworm carriers were detected using copro-antigen enzyme-linked immunosorbent assay and seven of 10 (70%) pigs belonging to the tapeworm carriers were found with viable cyst infection on necropsy. This was significantly greater than the prevalence of viable cyst infection among pigs living < 500 m (11%) and > 500 m (0.5%) from a tapeworm carrier (P < 0.001 for distance trend). Similar statistically significant prevalence gradients were observed after adjustment for possible confounders and for other pig-level outcomes including infection with > 10 viable cysts, degenerated cyst infection, and serological outcomes. This investigation confirms that porcine cysticercosis clusters strongly around tapeworm carriers in endemic rural regions of northern Peru and supports interventions that target these hotspots.
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Affiliation(s)
- Andres G Lescano
- Emerging Diseases and Climate Change Research Unit, School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru.,Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Ian W Pray
- School of Public Health, Oregon Health and Science University and Portland State University, Portland, Oregon
| | - Armando E Gonzalez
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.,School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Robert H Gilman
- Research Department, Asociación Benéfica PRISMA (Proyectos en Informatica, Salud, Medicina y Agricultura), Lima, Peru.,Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.,Department of Microbiology, School of Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Victor C W Tsang
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Ricardo Gamboa
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - M Claudia Guezala
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
| | - Viterbo Aybar
- School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru.,Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Silvia Rodriguez
- Instituto de Ciencias Neurológicas, Cysticercosis Unit, Lima, Peru
| | - Lawrence H Moulton
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Elli Leontsini
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Guillermo Gonzalvez
- Department of Microbiology, School of Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Seth E O'Neal
- School of Public Health, Oregon Health and Science University and Portland State University, Portland, Oregon
| | - Hector H Garcia
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.,Instituto de Ciencias Neurológicas, Cysticercosis Unit, Lima, Peru.,Department of Microbiology, School of Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru.,Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Lima, Peru
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12
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Li T, Chen X, Wang H, Openshaw JJ, Zhong B, Felt SA, Ito A, Luby SP. High prevalence of taeniasis and Taenia solium cysticercosis in children in western Sichuan, China. Acta Trop 2019; 199:105133. [PMID: 31415736 DOI: 10.1016/j.actatropica.2019.105133] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 07/26/2019] [Accepted: 08/09/2019] [Indexed: 12/27/2022]
Abstract
Data in China on human Taenia infections, including Taenia solium cysticercosis, is largely lacking. We aimed to determine the prevalence of taeniasis with all three human Taenia species as well as T. solium cysticercosis in primary school-aged children in minority areas of western Sichuan, China. During April 2016 to December 2017, we did a cross-sectional study in five western Sichuan Province primary schools in Liangshan (3 schools), Ganzi (1 school) and Aba (1 school) prefectures. Diagnosis of taeniasis was made by stool microscopy for presence of Taenia eggs, as well as recovery of taeniid tapeworms or proglottids by medicinal treatment followed by species identification using multiplex PCR. Diagnosis of T. solium cysticercosis was made serologically using an ELISA with low-molecular-weight antigens purified from T. solium cyst fluid to detect specific IgG antibodies. A total of 1672 children were screened for taeniasis and 1639 were evaluated for cysticercosis antibodies. Overall prevalence of taeniasis was 7.5% but was as high as 15.6% at one school site (e.g., Shuiluo). Of the three known human Taenia species, adult T. solium tapeworms were detected in 42 children from four of the five schools (all three schools in Liangshan and one in Aba), giving a prevalence of T. solium taeniasis of 2.5% (95% confidence interval 0-6.7%). Cysticercosis antibody seropositivity by school varied from 2.3% to 15.6% (overall 7.5%). T. solium taeniasis carriers were more likely to have cysticercosis antibodies than children without T. solium taeniasis (43.6% vs 6.6%). Schools with higher prevalences of T. solium taeniasis were more likely to have children with human cysticercosis IgG antibodies. This study shows a high prevalence of taeniasis and T. solium cysticercosis in primary school-aged children in minority areas of western Sichuan, suggesting an urgent necessity for school-based disease control.
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Affiliation(s)
- Tiaoying Li
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Sichuan Province, Chengdu, Sichuan, People's Republic of China.
| | - Xingwang Chen
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Sichuan Province, Chengdu, Sichuan, People's Republic of China
| | - Hao Wang
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Sichuan Province, Chengdu, Sichuan, People's Republic of China
| | - John J Openshaw
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University, Stanford, CA, USA
| | - Bo Zhong
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Sichuan Province, Chengdu, Sichuan, People's Republic of China
| | - Stephen A Felt
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Akira Ito
- Department of Parasitology and Laboratory of NTDs, Asahikawa Medical University, Asahikawa, Japan
| | - Stephen P Luby
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University, Stanford, CA, USA
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13
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Ito A, Li T, Wandra T, Dekumyoy P, Yanagida T, Okamoto M, Budke CM. Taeniasis and cysticercosis in Asia: A review with emphasis on molecular approaches and local lifestyles. Acta Trop 2019; 198:105075. [PMID: 31295430 DOI: 10.1016/j.actatropica.2019.105075] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 05/14/2019] [Accepted: 07/05/2019] [Indexed: 02/07/2023]
Abstract
Taeniasis is an important parasitic condition in Asia, especially since all three human-infecting Taenia spp., Taenia solium, Taenia saginata, and Taenia asiatica are found in this region. These three species are believed to be sympatrically distributed, with the largest disease burden found in remote and rural areas where people raise pigs and cattle in a traditional manner. Recent studies revealed that T. asiatica and T. saginata are genetically-related sister species that are not completely reproductively isolated from each other. Current evidence indicates that most T. asiatica adult worms are hybrid-derived descendants. Moving forward, nuclear DNA analysis will be critical in further assessing the species circulating locally. Lifestyle choices, such as the consumption of undercooked meat, are important in maintaining the life cycles of these parasites. In addition, poor hygiene and sanitation, in highly endemic areas, make disease control difficult, resulting in the need for sustainable education programs. An overview of the present situation of taeniasis and cysticercosis in Asia is provided, followed by a discussion of molecular approaches to species assessment and the impact of human lifestyles on parasite transmission.
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Affiliation(s)
- Akira Ito
- Department of Parasitology and Laboratory of NTDs, Asahikawa Medical University, Asahikawa, Japan.
| | - Tiaoying Li
- Institute of Parasitic Diseases, Sichuan Centers for Disease Control and Prevention, Chengdu, People's Republic of China
| | - Toni Wandra
- Directorate of Postgraduate, Sari Mutiara Indonesia University, Medan, Indonesia
| | - Paron Dekumyoy
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Tetsuya Yanagida
- Laboratory of Veterinary Parasitology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Munehiro Okamoto
- Center for Human Evolution Modeling Research, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Christine M Budke
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine & Biomedical Sciences, Texas A & M University, College Station, Texas, USA
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14
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The World Health Organization 2030 goals for Taenia solium: Insights and perspectives from transmission dynamics modelling: CystiTeam Group for Epidemiology and Modelling of Taenia solium Taeniasis/Cysticercosis. Gates Open Res 2019; 3:1546. [PMID: 31701092 PMCID: PMC6820453 DOI: 10.12688/gatesopenres.13068.2] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2019] [Indexed: 12/14/2022] Open
Abstract
Taenia solium (TS), responsible for porcine cysticercosis, human taeniasis and (neuro)cysticercosis, was included in the World Health Organization neglected tropical disease (NTD) roadmap published in 2012. Targets set in this roadmap have not been met, but T. solium has been included in the consultation process for the new 2030 goals proposed for priority NTDs. Taenia solium transmission dynamics models can contribute to this process. A recent review has compared existing T. solium transmission models, identifying their similarities and differences in structure, parameterization and modelled intervention approaches. While a formal model comparison to investigate the impact of interventions is yet to be conducted, the models agree on the importance of coverage for intervention effectiveness and on the fact that human- and pig-focused interventions can be optimally combined. One of these models, cystiSim, an individual-based, stochastic model has been used to assess field-applicable interventions, some currently under evaluation in on-going trials in Zambia. The EPICYST, population-based, deterministic model has highlighted, based on simulating a generic sub-Saharan Africa setting, the higher efficacy (measured as the percentage of human cysticercosis cases prevented) of biomedical interventions (human and pig treatment and pig vaccination) compared to improved husbandry, sanitation, and meat inspection. Important questions remain regarding which strategies and combinations thereof provide sustainable solutions for severely resource-constrained endemic settings. Defining realistic timeframes to achieve feasible targets, and establishing suitable measures of effectiveness for these targets that can be quantified with current monitoring and evaluation tools, are current major barriers to identifying validated strategies. Taenia solium transmission models can support setting achievable 2030 goals; however, the refinement of these models is first required. Incorporating socio-economic elements, improved understanding of underlying biological processes, and consideration of spatial dynamics are key knowledge gaps that need addressing to support model development.
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The World Health Organization 2030 goals for Taenia solium: Insights and perspectives from transmission dynamics modelling: CystiTeam Group for Epidemiology and Modelling of Taenia solium Taeniasis/Cysticercosis. Gates Open Res 2019. [PMID: 31701092 DOI: 10.12688/gatesopenres.13068.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Taenia solium (TS), responsible for porcine cysticercosis, human taeniasis and (neuro)cysticercosis, was included in the World Health Organization neglected tropical disease (NTD) roadmap published in 2012. Targets set in this roadmap have not been met, but T. solium has been included in the consultation process for the new 2030 goals proposed for priority NTDs. Taenia solium transmission dynamics models can contribute to this process. A recent review has compared existing T. solium transmission models, identifying their similarities and differences in structure, parameterization and modelled intervention approaches. While a formal model comparison to investigate the impact of interventions is yet to be conducted, the models agree on the importance of coverage for intervention effectiveness and on the fact that human- and pig-focused interventions can be optimally combined. One of these models, cystiSim, an individual-based, stochastic model has been used to assess field-applicable interventions, some currently under evaluation in on-going trials in Zambia. The EPICYST, population-based, deterministic model has highlighted, based on simulating a generic sub-Saharan Africa setting, the higher efficacy (measured as the percentage of human cysticercosis cases prevented) of biomedical interventions (human and pig treatment and pig vaccination) compared to improved husbandry, sanitation, and meat inspection. Important questions remain regarding which strategies and combinations thereof provide sustainable solutions for severely resource-constrained endemic settings. Defining realistic timeframes to achieve feasible targets, and establishing suitable measures of effectiveness for these targets that can be quantified with current monitoring and evaluation tools, are current major barriers to identifying validated strategies. Taenia solium transmission models can support setting achievable 2030 goals; however, the refinement of these models is first required. Incorporating socio-economic elements, improved understanding of underlying biological processes, and consideration of spatial dynamics are key knowledge gaps that need addressing to support model development.
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16
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Pray IW, Muro C, Gamboa R, Vilchez P, Wakeland W, Pan W, Lambert WE, Garcia HH, O'Neal SE. Seasonal patterns in risk factors for Taenia solium transmission: a GPS tracking study of pigs and open human defecation in northern Peru. Parasit Vectors 2019; 12:352. [PMID: 31311596 PMCID: PMC6636017 DOI: 10.1186/s13071-019-3614-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/10/2019] [Indexed: 11/17/2022] Open
Abstract
Background Taenia solium (cysticercosis) is a parasitic cestode that is endemic in rural populations where open defecation is common and free-roaming pigs have access to human feces. The purpose of this study was to examine the roaming patterns of free-range pigs, and identify areas where T. solium transmission could occur via contact with human feces. We did this by using GPS trackers to log the movement of 108 pigs in three villages of northern Peru. Pigs were tracked for approximately six days each and tracking was repeated in the rainy and dry seasons. Maps of pig ranges were analyzed for size, distance from home, land type and contact with human defecation sites, which were assessed in a community-wide defecation survey. Results Consistent with prior GPS studies and spatial analyses, we found that the majority of pigs remained close to home during the tracking period and had contact with human feces in their home areas: pigs spent a median of 79% (IQR: 61–90%) of their active roaming time within 50 m of their homes and a median of 60% of their contact with open defecation within 100 m of home. Extended away-from-home roaming was predominately observed during the rainy season; overall, home range areas were 61% larger during the rainy season compared to the dry season (95% CI: 41–73%). Both home range size and contact with open defecation sites showed substantial variation between villages, and contact with open defecation sites was more frequent among pigs with larger home ranges and pigs living in higher density areas of their village. Conclusions Our study builds upon prior work showing that pigs predominately roam and have contact with human feces within 50–100 m of the home, and that T. solium transmission is most likely to occur in these concentrated areas of contact. This finding, therefore, supports control strategies that target treatment resources to these areas of increased transmission. Our finding of a seasonal trend in roaming ranges may be useful for control programs relying on pig interventions, and in the field of transmission modeling, which require precise estimates of pig behavior and risk. Electronic supplementary material The online version of this article (10.1186/s13071-019-3614-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ian W Pray
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, USA.
| | - Claudio Muro
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
| | - Ricardo Gamboa
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
| | - Percy Vilchez
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
| | - Wayne Wakeland
- Systems Science Program, Portland State University, Portland, Oregon, USA
| | - William Pan
- Global Health Institute, Duke University, Durham, North Carolina, USA
| | - William E Lambert
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, USA
| | - Hector H Garcia
- Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru.,School of Sciences, Department of Microbiology, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Seth E O'Neal
- School of Public Health, Oregon Health & Science University and Portland State University, Portland, Oregon, USA.,Center for Global Health Tumbes, Universidad Peruana Cayetano Heredia, Tumbes, Peru
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Singh G, Sander JW. Historical perspective: The British contribution to the understanding of neurocysticercosis. JOURNAL OF THE HISTORY OF THE NEUROSCIENCES 2019; 28:332-344. [PMID: 30933663 DOI: 10.1080/0964704x.2018.1564523] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Neurocysticercosis, or brain infestation with the larval stage of Taenia solium, is the most common risk factor for epilepsy in many endemic regions of the world. Hardly any cases are seen in Western developed countries, including Britain. However, a sizeable number (n = 450) was seen among British soldiers returning from deputation to India, then a British colony, first reported by Col. MacArthur at the Queen Alexandria Military Hospital in 1931. Here, we review the influence of the perceptive observations of British Army medics on the understanding of the parasitic disorder. The majority of these people presented with epilepsy. Among the contributions of the army medics were establishing the diagnosis, initially by histological examination of subcutaneous and muscular infestation, and later by radiography, clarifying the prognosis and the role of medical and surgical treatments and uncovering the close relationship between the larval (cysticercosis) and adult (intestinal tapeworm) stages of T. solium.
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Affiliation(s)
- Gagandeep Singh
- a Department of Neurology, Dayanand Medical College , Ludhiana , India
- b NIHR University College London Hospitals Biomedical Research Centre , UCL Queen Square Institute of Neurology , London , UK
| | - Josemir W Sander
- b NIHR University College London Hospitals Biomedical Research Centre , UCL Queen Square Institute of Neurology , London , UK
- c Chalfont Centre for Epilepsy , Bucks , UK
- d Stichting Epilepsie Instellingen Nederland (SEIN) , Heemstede , The Netherlands
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18
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Strategies for tackling Taenia solium taeniosis/cysticercosis: A systematic review and comparison of transmission models, including an assessment of the wider Taeniidae family transmission models. PLoS Negl Trop Dis 2019; 13:e0007301. [PMID: 30969966 PMCID: PMC6476523 DOI: 10.1371/journal.pntd.0007301] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 04/22/2019] [Accepted: 03/13/2019] [Indexed: 01/03/2023] Open
Abstract
Background The cestode Taenia solium causes the neglected (zoonotic) tropical disease cysticercosis, a leading cause of preventable epilepsy in endemic low and middle-income countries. Transmission models can inform current scaling-up of control efforts by helping to identify, validate and optimise control and elimination strategies as proposed by the World Health Organization (WHO). Methodology/Principal findings A systematic literature search was conducted using the PRISMA approach to identify and compare existing T. solium transmission models, and related Taeniidae infection transmission models. In total, 28 modelling papers were identified, of which four modelled T. solium exclusively. Different modelling approaches for T. solium included deterministic, Reed-Frost, individual-based, decision-tree, and conceptual frameworks. Simulated interventions across models agreed on the importance of coverage for impactful effectiveness to be achieved. Other Taeniidae infection transmission models comprised force-of-infection (FoI), population-based (mainly Echinococcus granulosus) and individual-based (mainly E. multilocularis) modelling approaches. Spatial structure has also been incorporated (E. multilocularis and Taenia ovis) in recognition of spatial aggregation of parasite eggs in the environment and movement of wild animal host populations. Conclusions/Significance Gaps identified from examining the wider Taeniidae family models highlighted the potential role of FoI modelling to inform model parameterisation, as well as the need for spatial modelling and suitable structuring of interventions as key areas for future T. solium model development. We conclude that working with field partners to address data gaps and conducting cross-model validation with baseline and longitudinal data will be critical to building consensus-led and epidemiological setting-appropriate intervention strategies to help fulfil the WHO targets. Taenia solium infection in humans (taeniosis and neurocysticercosis) and pigs (cysticercosis) presents a significant global public health and economic challenge. The World Health Organization has called for validated strategies and wider consensus on which strategies are suitable for different epidemiological settings to support successful T. solium control and elimination efforts. Transmission models can be used to inform these strategies. Therefore, a modelling review was undertaken to assess the current state and gaps relating to T. solium epidemiological modelling. The literature surrounding models for other Taeniidae family infections was also considered, identifying approaches to aid further development of existing T. solium models. A variety of different modelling approaches have been used for T. solium including differences in structural and parametric assumptions associated with T. solium transmission biology. Despite these differences, all models agreed on the importance of coverage on intervention effectiveness. Other Taeniidae family models highlighted the need for incorporating spatial structure when necessary to capture aggregation of transmission stages in the environment and movement of animal hosts.
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de Coster T, Van Damme I, Baauw J, Gabriël S. Recent advancements in the control of Taenia solium: A systematic review. Food Waterborne Parasitol 2018; 13:e00030. [PMID: 32095601 PMCID: PMC7034013 DOI: 10.1016/j.fawpar.2018.e00030] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/14/2018] [Accepted: 09/17/2018] [Indexed: 01/07/2023] Open
Abstract
The combined health and economic impact of Taenia solium urges for control and, if possible, elimination of this neglected parasitic zoonosis. Up till now there is still no consensus about the most cost-effective and feasible approaches for control. The objective of this systematic review is to identify and summarize the evidence in English scientific literature on the control and elimination of T. solium since 2014, based on the rapidly evolving field of evidence on control and elimination of T. solium. The search resulted in the identification of 458 records of which 31 were included, covering 13 field trials and 18 articles containing experimental data, mathematical models, and other information directly relevant the control of T. solium. Recent field studies confirm that combinations of interventions or multiple rounds are more successful in obtaining rapid reductions in transmission and parasite occurrence, with the quick impact of the combination of human and pig treatment confirmed in a South Asian and Peruvian context. Moreover, elimination of transmission through a one-year intensive program, combining human and pig treatment/vaccination was described in a Peruvian study. Recent studies also provide more data on the positive impact of specific health education, as well as newly developed electronic educational tools, providing opportunities for area specific community-engaged participatory interventions. Once control has been achieved, monitoring of migration of both potentially infected people and pigs from outside the control area is important for sustained disease control. Combined intervention field studies demonstrate sharp decreases in disease occurrence. New, specific, efficient, electronic educational tools are available. Elimination of Taenia solium in a Peruvian endemic area has been described. Integration of Taenia solium control in other NTD control programs can be effective.
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Affiliation(s)
- T de Coster
- Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - I Van Damme
- Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - J Baauw
- Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - S Gabriël
- Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium
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20
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Ng-Nguyen D, Traub RJ, Nguyen VAT, Breen K, Stevenson MA. Spatial distribution of Taenia solium exposure in humans and pigs in the Central Highlands of Vietnam. PLoS Negl Trop Dis 2018; 12:e0006810. [PMID: 30235251 PMCID: PMC6168177 DOI: 10.1371/journal.pntd.0006810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 10/02/2018] [Accepted: 09/01/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Taenia solium, a pork-borne parasitic zoonosis, is the cause of taeniasis and cysticercosis in humans. In Vietnam, poor sanitation, the practice of outdoor defecation and consumption of raw/undercooked pork have been associated with infection/exposure to T. solium in both humans and pigs. The broad-scale geographic distribution of the prevalence of T. solium varies throughout the country with infection restricted to isolated foci in the north and a more sporadic geographic distribution in the Central Highlands and the south. While cross-sectional studies have allowed the broad-scale geographic distribution of T. solium to be described, details of the geographic distribution of T. solium at finer spatial scales have not been described in detail. This study provides a descriptive spatial analysis of T. solium exposure in humans and pigs and T. solium taeniasis in humans within individual households in village communities of Dak Lak in the Central Highlands of Vietnam. METHODOLOGY/PRINCIPAL FINDINGS We used Ripley's K-function to describe spatial dependence in T. solium exposure positive and negative human and pig households and T. solium taeniasis exposure positive and negative households in villages within the districts of Buon Don, Krong Nang and M'Drak of Dak Lak province in the Central Highlands of Vietnam. The prevalence of exposure to T. solium in pigs in Dak Lak province was 9 (95% CI 5 to 17) cases per 1000 pigs at risk. The prevalence of exposure to the parasite in humans was somewhat higher at 5 (95% CI 3 to 8) cases per 100 individuals at risk. Spatial aggregations of T. solium exposure-positive pig and human households occurred in some, but not all of the villages in the three study districts. Human exposure-positive households were found to be aggregated within a distance of 200 to 300 m in villages in Krong Nang district compared with distances of up to 1500 m for pig exposure-positive households in villages in M'Drak district. Although this study demonstrated the aggregation of households in which either T. solium exposure- or taeniasis-positive individuals were present, we were unable to identify an association between the two due to the very low number of T. solium taeniasis-positive households. CONCLUSIONS Spatial aggregations of T. solium exposure-positive pig and human households occurred in some, but not all of the villages in the three study districts. We were unable to definitively identify reasons for these findings but speculate that they were due to a combination of demographic, anthropological and micro-environmental factors. To more definitively identify characteristics that increase cysticercosis risk we propose that cross-sectional studies similar in design to that described in this paper should be applied in other provinces of Vietnam.
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Affiliation(s)
- Dinh Ng-Nguyen
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia
- Faculty of Animal Sciences and Veterinary Medicine, Tay Nguyen University, Dak Lak, Vietnam
| | - Rebecca Justine Traub
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Van-Anh Thi Nguyen
- Faculty of Animal Sciences and Veterinary Medicine, Tay Nguyen University, Dak Lak, Vietnam
| | - Kathleen Breen
- Department of Livestock, Montana Veterinary Diagnostic Lab, Bozeman, Montana, United States of America
| | - Mark Anthony Stevenson
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia
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Abstract
PURPOSE OF REVIEW Cestodes infections in humans are among the most prevalent parasitosis worldwide. Although tapeworm infection is often asymptomatic, they can be associated with a range of symptoms. The landscape of cestode infections is changing with rapid diagnosis techniques and advanced molecular diagnosis aiding in identification of species specific epidemiology. RECENT FINDINGS Traditional descriptions of species by location have been challenged with molecular diagnostic techniques, which show variation in distribution of species, thought to be because of globalization and importation of disease. MAIN THEMES IN LITERATURE Epidemiology, molecular diagnostic techniques. SUMMARY Infection by tapeworms is often asymptomatic or accompanied by mild symptoms though can occasionally cause severe disease and contribute to anemia and malnutrition. Tapeworm infection is most prevalent in resource-poor countries but the distribution is worldwide. Epidemiology of infection is changing because of molecular diagnostics, which allow more accurate tracking of species.
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Affiliation(s)
- Camille Webb
- Division of Infectious Disease Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas, USA
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