The Incidence of Human Cysticercosis in a Rural Community of Eastern Zambia

PLoS Neglected Tropical Diseases, Mar 2013

A community-based longitudinal study was performed in the Eastern Province of Zambia, in which repeated serological samplings were done to determine the incidence of human cysticercosis. Three sampling rounds were carried out at six months intervals. A total of 867 participants presented for all three samplings. All samples were tested for the presence of cysticercus antigens using a monoclonal antibody-based enzyme-linked immunosorbent assay (sero-Ag-ELISA), while a randomly selected sub-sample of 161 samples from each sampling round was tested for specific antibodies using a commercial enzyme-linked immunoelectrotransfer blot (EITB) assay. Stool samples (n = 226) were also collected during the final round of sampling for taeniosis diagnosis by coprology and coproantigen ELISA. Cysticercosis seroprevalence varied from 12.2% to 14.5% (sero-Ag) and from 33.5% to 38.5% (sero-Ab) during the study period. A taeniosis prevalence of 11.9% was determined. Incidence rates of 6300 (sero-Ag, per 100000 persons-year) and 23600 (sero-Ab, per 100000 persons-year) were determined. Seroreversion rates of 44% for sero-Ag and 38.7% for sero-Ab were recorded over the whole period. In conclusion, this study has shown the dynamic nature of T. solium infections; many of the people at risk become (re)infected due to the high environmental contamination, with a high number turning seronegative within a year after infection. An important number of infections probably never fully establish, leading to transient antibody responses and short-term antigen presence.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

http://www.plosntds.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371/journal.pntd.0002142&representation=PDF

The Incidence of Human Cysticercosis in a Rural Community of Eastern Zambia

et al. (2013) The Incidence of Human Cysticercosis in a Rural Community of Eastern Zambia. PLoS Negl Trop Dis 7(3): e2142. doi:10.1371/journal.pntd.0002142 The Incidence of Human Cysticercosis in a Rural Community of Eastern Zambia Kabemba E. Mwape 0 Isaac K. Phiri 0 Nicolas Praet 0 Niko Speybroeck 0 John B. Muma 0 Pierre Dorny 0 Sarah Gabrie l 0 Ana Flisser, Universidad Nacional Auto noma de Mexico, Mexico 0 1 Department of Clinical Studies, School of Veterinary Medicine, University of Zambia , Lusaka , Zambia , 2 Department of Veterinary Tropical Diseases, Faculty of Veterinary Sciences, University of Pretoria , Pretoria , South Africa , 3 Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium, 4 Institute of Health and Society, Universite Catholique de Louvain , Brussels , Belgium , 5 Department of Disease Control, School of Veterinary Medicine, University of Zambia , Lusaka , Zambia , 6 Laboratory of Veterinary Parasitology, Faculty of Veterinary Medicine, Ghent University , Merelbeke , Belgium A community-based longitudinal study was performed in the Eastern Province of Zambia, in which repeated serological samplings were done to determine the incidence of human cysticercosis. Three sampling rounds were carried out at six months intervals. A total of 867 participants presented for all three samplings. All samples were tested for the presence of cysticercus antigens using a monoclonal antibody-based enzyme-linked immunosorbent assay (sero-Ag-ELISA), while a randomly selected sub-sample of 161 samples from each sampling round was tested for specific antibodies using a commercial enzyme-linked immunoelectrotransfer blot (EITB) assay. Stool samples (n = 226) were also collected during the final round of sampling for taeniosis diagnosis by coprology and coproantigen ELISA. Cysticercosis seroprevalence varied from 12.2% to 14.5% (sero-Ag) and from 33.5% to 38.5% (sero-Ab) during the study period. A taeniosis prevalence of 11.9% was determined. Incidence rates of 6300 (sero-Ag, per 100000 persons-year) and 23600 (sero-Ab, per 100000 persons-year) were determined. Seroreversion rates of 44% for sero-Ag and 38.7% for sero-Ab were recorded over the whole period. In conclusion, this study has shown the dynamic nature of T. solium infections; many of the people at risk become (re)infected due to the high environmental contamination, with a high number turning seronegative within a year after infection. An important number of infections probably never fully establish, leading to transient antibody responses and short-term antigen presence. - Funding: The study received financial support from the Flemish Interuniversity Co-operation, Research Initiatives Programme, Zambia (VLIR-UOS.ZIUS2008RIP8961). Support was also obtained from the Belgian Cooperation in the framework of the institutional collaboration between the Institute of Tropical Medicine in Antwerp, Belgium, and the University of Pretoria, Pretoria, South Africa. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Human (neuro) cysticercosis, an infection caused by the metacestode larval stage of the pork tapeworm Taenia solium, is a serious but neglected zoonotic disease and a major public health problem in many developing countries of Latin America, Asia and Africa [1,2]. Humans are the definitive hosts harbouring the adult tapeworm (leading to taeniosis). Carriers of the tapeworm shed eggs into the environment that are infective not only to the pig intermediate host (leading to porcine cysticercosis) but also to humans who then act as an accidental intermediate host [3] leading to human cysticercosis. When the larval stages invade the nervous system they cause neurocysticercosis (NCC), which is the most important parasitic disease affecting the nervous system and accounts for about 30% of all acquired epilepsy cases in endemic areas [4]. In terms of Disability Adjusted Life Years (DALYs), the global burden of epilepsy is estimated at 7.8 million DALYs with 6.5 million of these occurring in T. solium endemic regions of the world [5]. The few community based human prevalence studies carried out in Africa have indicated sero-prevalences of human cysticercosis ranging from 722% [e.g. 6,7,8]. In a recent study in Zambia, a sero-prevalence of 5.8% has been recorded in a rural community in the eastern part of Zambia [9]. Studies that report incidence of human cysticercosis are even more scarce and absent for Sub-Saharan Africa. Two longitudinal studies in villages in Peru indicated human cysticercosis incidence rates of 25% and 8% by specific antibody analysis [10]. In a simulation model based on data obtained in a rural community in Ecuador an annual incidence rate of 14% was described [11]. Obviously, more information is needed on the transmission dynamics of th (...truncated)


This is a preview of a remote PDF: http://www.plosntds.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371/journal.pntd.0002142&representation=PDF

Kabemba E. Mwape, Isaac K. Phiri, Nicolas Praet, Niko Speybroeck, John B. Muma, Pierre Dorny, Sarah Gabriël. The Incidence of Human Cysticercosis in a Rural Community of Eastern Zambia, PLoS Neglected Tropical Diseases, 2013, Volume 7, Issue 3, DOI: 10.1371/journal.pntd.0002142