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CURATOR

Postdoctoral Fellow, Ross University

PINBOARD SUMMARY

Control of Taenia solium is crucial as it affects the poorest of the poor and their livestock

Introduction: Taenia solium taeniosis/cysticercosis (TSTC) is ranked the most important foodborne parasitic disease globally. Despite an internationally agreed „Road Map‟ for elimination, control has yet to be trialled in sub-Saharan Africa. Intervention tools exist for both human taeniosis and porcine cysticercosis but are not accessible in sub-Saharan Africa. Studies from South-west Tanzania recorded a human taeniosis, human cysticercosis (Ab-ELISA), and porcine cysticercosis (Ag-ELISA) prevalence of 5.2%, 45.3% and 30.0%, respectively. Aim: Demonstrate the impact of two international funded projects in Tanzania aiming at reducing the prevalence of TSTC in humans and pigs. Methods: A Danida-funded project (2010-2016) focussed on improving livelihood of smallholder pig producers by providing education, pig pen models and pig feed and anthelmintic treatment. A Bill and Melinda Gates funded project (2012-2016) assessed the effect of praziquantel Mass Drug Administration (provided by Ministry of Health against schistosomiasis) on human taeniosis and porcine cysticercosis. Both projects were carried out in Mbeya Region, South-west Tanzania. Results: General knowledge regarding TSTC increased among trained farmers and professionals, prevalence of human taeniosis and porcine cysticercosis declined, farmers livelihood improved and research capacity was extensively built. At national level, a policy brief was produced and TSTC was adopted as a national health priority. Internationally, TSTC in Tanzania was recognised and included in the list of countries targeting disease elimination. A computer based education tool “The Vicious Worm” was developed in English and Swahili, providing evidence-based efficient health education on a programmatic level. Conclusion: TSTC is highly endemic in Tanzania and now recognised as a national health priority. Using a combination of human and pig treatment with education targeting health and pig management was able to reduce the prevalence of TSTC in the area. However, a sustainable control strategy will require a cross-sectoral approach, availability of drugs/vaccine for humans and pigs, health and pig management education, a point-of-care test for detecting taeniosis and cysticercosis and political commitment. With the available knowledge, a proof-of-concept is ready to be trialled in sub-Saharan Africa, paving the road for a sustainable and cost-effective One Health model for control and elimination of T. solium.

7 ITEMS PINNED

Temporal fluctuations in the sero-prevalence of Taenia solium cysticercosis in pigs in Mbeya Region, Tanzania.

Abstract: Porcine cysticercosis is an emerging agricultural problem in sub-Saharan Africa. This has been documented primarily through cross-sectional studies, however detailed knowledge of the transmission dynamics of this disease in sub-Saharan Africa is lacking. This study aims to describe seasonal variations in sero-prevalence of antigen ELISA positive porcine cysticercosis in an endemic area.A longitudinal study composed of three cross-sectional surveys was carried out in Mbeya Region, Tanzania; the first two six months apart (March/April 2012 and October/November 2012) and the last eight months later (July/August 2013). Venous blood was collected from pigs in 22 villages and analysed using Ag-ELISA.In each survey between 800-1000 serum samples were collected. The first survey revealed a cysticercosis sero-prevalence of 15% (n = 822, 95% CI: 13-18%). The sero-prevalence had significantly increased to 24% (p < 0.001, χ2-test, n = 812, 95% CI: 21-27%) at the time of the 6 month follow-up. At 14-months the sero-prevalence had dropped to 20% (p = 0.053, χ2-test, n = 998, 95% CI: 18-23%). Overall, this was a reduction in sero-prevalence compared with a study conducted in 2007 in the same area, where 31% (186/600) of pigs were found positive.Confined pigs did not have a lower sero-prevalence compared to free roaming pigs in any of the three surveys. Several factors may have contributed to the observed fluctuations such as African swine fever or seasonal variation in local crop production practices. Also, as the Ag-ELISA assay used is not species specific, variation in transmission of Taenia hydatigena could potentially influence the results. The observed fluctuations contradict a theoretical model which predicts a stable equilibrium, which only considers a two-compartment (pig and human) model excluding the effect of the environment. Whether the disease has an endemic equilibrium, or undergoes fluctuations dependent on extrinsic and/or socio-economic factors remains to be elucidated.

Pub.: 05 Dec '14, Pinned: 09 Jun '17

Feedstuff and poor latrines may put pigs at risk of cysticercosis--A case-control study.

Abstract: Attempts to control Taenia solium in low-income countries have been unsuccessful or unsustainable. This could indicate a 'missing link' in our understanding of the transmission dynamics of the parasite and possibly the magnitude of environmental contamination. We aimed to identify risk factors associated with porcine cysticercosis using a case-control study design, utilising known information on persistent or multiple infections of porcine cysticercosis. The study, a combination of questionnaire interviews and observational surveys, was conducted in July 2014 in the two districts Mbeya and Mbozi, Tanzania. Study households were identified based on their status regarding porcine cysticercosis prevalence and allocated into cases or controls based on previous porcine cysticercosis presence. This resulted in 43 farmers in the case group and 50 farmers in the control group, from 20 villages. Potato peels were said to be given to pigs either raw or boiled by 46% of the farmers. Based on logistic regression porcine cysticercosis could be associated with absence or a completely open latrine (p=0.035, OR 5.98, CI: 1.33-43.02) compared to an enclosed latrine. Feeding potato peels to pigs was also associated with increased risk of infection (p=0.007, OR 3.45, CI: 1.43-8.79). Logistic analysis including the pig management system indicated pigs kept in elevated pens (p=0.049, OR 5.33, CI: 1.08-32.27) and on a dirt floor (p=0.041, OR 9.87, CI: 1.29-114.55) were more likely to be infected compared to a cemented floor. Whether potato peels are contaminated with Taenia eggs before they reach the household or whether the contamination is from water or dirty hands during the process of peeling, remains to be confirmed. This study suggests that detailed assessment of a number of areas of pig management is essential for designing effective control programmes.

Pub.: 26 Aug '15, Pinned: 09 Jun '17

Taenia solium taeniosis/cysticercosis and the co-distribution with schistosomiasis in Africa.

Abstract: This study aimed to map the distribution of Taenia solium taeniosis/cysticercosis and the co-distribution with schistosomiasis in Africa. These two major neglected tropical diseases are presumed to be widely distributed in Africa, but currently the level of co-distribution is unclear.A literature search on T. solium taeniosis/cysticercosis was performed to compile all known studies on the presence of T. solium and apparent prevalence of taeniosis and porcine cysticercosis in Africa. Studies were geo-referenced using an online gazetteer. A Bayesian framework was used to combine the epidemiological data on the apparent prevalence with external information on test characteristics to estimate informed district-level prevalence of taeniosis and porcine cysticercosis. Districts with T. solium taeniosis/cysticercosis presence were cross-referenced with the Global Neglected Tropical Diseases Database for schistosomiasis presence.The search strategies identified 141 reports of T. solium in Africa from 1985 to 2014 from a total of 476 districts in 29 countries, 20 with porcine cysticercosis, 22 with human cysticercosis, and 16 with taeniosis, in addition to 2 countries identified from OIE reports. All 31 countries were considered, on national scale, to have co-distribution with schistosomiasis. Presence of both parasites was confirmed in 124 districts in 17 countries. The informed prevalence of taeniosis and porcine cysticercosis were estimated for 14 and 41 districts in 10 and 13 countries, respectively.With the paucity of data, T. solium infection is grossly under-reported and expected to be more widespread than this study suggests. In areas where co-distribution occurs there is a need for increased emphasis on evaluation of integrated intervention approaches for these two helminth infections and allocation of resources for evaluating the extent of adverse effects caused by mass drug administration.

Pub.: 13 Jun '15, Pinned: 09 Jun '17

Are we ready for Taenia solium cysticercosis elimination in sub-Saharan Africa?

Abstract: The World Health Organization announced in November 2014 at the fourth international meeting on 'the control of neglected zoonotic diseases - from advocacy to action', that intervention tools for eliminating Taenia solium taeniosis/cysticercosis (TSTC) are in place. The aim of this work was to elucidate theoretical outcomes of various control options suggested for TSTC elimination in sub-Saharan Africa (SSA) over a 4-year period. Our current knowledge regarding T. solium epidemiology and control primarily builds on studies from Latin America. A simple transmission model - built on data from Latin America - has been used to predict the effect of various interventions such as mass treatment of humans, vaccination and treatment of pigs, and health education of communities, potentially leading to change in bad practices and reducing transmission risks. Based on simulations of the transmission model, even a 4-year integrated One Health approach fails to eliminate TSTC from a small community and in all simulations, the prevalence of human taeniosis and porcine cysticercosis start to rise as soon as the programmes end. Our current knowledge regarding transmission and burden of TSTC in SSA is scarce and while claiming to be tool ready, the selection of diagnostic and surveillance tools, as well as the algorithms and stepwise approaches for control and elimination of TSTC remain major challenges.

Pub.: 21 Apr '16, Pinned: 09 Jun '17

Effect of National Schistosomiasis Control Programme on Taenia solium taeniosis and porcine cysticercosis in rural communities of Tanzania

Abstract: Taenia solium is found throughout sub-Saharan Africa and co-endemic with schistosomiasis in many regions. Taenia solium leads to taeniosis and neurocysticercosis - the leading cause of preventable epilepsy globally. This study aimed to assess the effects of the National Schistosomiasis Control Programme on prevalence of taeniosis and porcine cysticercosis over a four year period in Tanzania. School-based mass drug administration (MDA) of praziquantel was carried out based on schistosomiasis endemicity. Four human and five porcine cross-sectional surveys were carried out from 2012 to 2015 in Mbozi and Mbeya district in Tanzania. Three rounds of school-based MDA of praziquantel were delivered in Mbozi and two in Mbeya. The prevalence of taeniosis and porcine cysticercosis was estimated annually. Stool samples were collected from humans and prevalence of taeniosis estimated by copro-Ag-ELISA. Blood samples from pigs were collected to estimate cysticercosis prevalence by Ag-ELISA. “Track-and-treat” of taeniosis cases was carried out after each survey. In total 12082 stool samples and 4579 porcine serum samples were collected. Significantly fewer children (≤ 15) from Mbozi were infected throughout the study than children from Mbeya who showed a significant decrease in copro-Ag prevalence after the first treatment only. During the final survey in Mbozi the prevalence of taeniosis in adults (1.8%) was significantly lower (p = 0.031, OR 0.40, CI: 0.17–0.89), compared to baseline (4.1%). The prevalence of porcine cysticercosis (8%) had also dropped significantly (p = 0.002, OR 0.49, CI: 0.32–0.76) in this district compared to baseline (13%), whereas no significant difference was seen in Mbeya compared to baseline. The study suggests that three rounds of MDA targeting schistosomiasis in school-aged children combined with ‘track-and-treat’ contributed to a reduction in prevalence of T. solium in this population, and also had a spillover effect on adults in treated areas as well as reducing the prevalence of T. solium in the intermediate pig host population. Elimination of T. solium in this area would require a One Health approach.

Pub.: 28 Aug '16, Pinned: 09 Jun '17

CystiSim - An Agent-Based Model for Taenia solium Transmission and Control.

Abstract: Taenia solium taeniosis/cysticercosis was declared eradicable by the International Task Force for Disease Eradication in 1993, but remains a neglected zoonosis. To assist in the attempt to regionally eliminate this parasite, we developed cystiSim, an agent-based model for T. solium transmission and control. The model was developed in R and available as an R package (http://cran.r-project.org/package=cystiSim). cystiSim was adapted to an observed setting using field data from Tanzania, but adaptable to other settings if necessary. The model description adheres to the Overview, Design concepts, and Details (ODD) protocol and consists of two entities-pigs and humans. Pigs acquire cysticercosis through the environment or by direct contact with a tapeworm carrier's faeces. Humans acquire taeniosis from slaughtered pigs proportional to their infection intensity. The model allows for evaluation of three interventions measures or combinations hereof: treatment of humans, treatment of pigs, and pig vaccination, and allows for customary coverage and efficacy settings. cystiSim is the first agent-based transmission model for T. solium and suggests that control using a strategy consisting of an intervention only targeting the porcine host is possible, but that coverage and efficacy must be high if elimination is the ultimate goal. Good coverage of the intervention is important, but can be compensated for by including an additional intervention targeting the human host. cystiSim shows that the scenarios combining interventions in both hosts, mass drug administration to humans, and vaccination and treatment of pigs, have a high probability of success if coverage of 75% can be maintained over at least a four year period. In comparison with an existing mathematical model for T. solium transmission, cystiSim also includes parasite maturation, host immunity, and environmental contamination. Adding these biological parameters to the model resulted in new insights in the potential effect of intervention measures.

Pub.: 17 Dec '16, Pinned: 09 Jun '17