Control of Taenia solium taeniasis/cysticercosis: past practices and new possibilities

Comparison of Kato-Katz, PCR and coproantigen for the diagnosis of Taenia solium taeniasis

Four methods were compared for the diagnosis of human taeniasis caused by Taenia solium. Fecal samples from persons living in a T. solium endemic region of Madagascar were examined for taeniid eggs by the Kato–Katz method. Subsequently, samples positive (n = 16) and negative (n = 200) for T. solium eggs were examined by (i) amplification of the fragment of small subunit of the mitochondrial ribosomal RNA (rrnS) gene using conventional polymerase chain reaction (PCR) and (ii) a nested PCR of a fragment of the T. solium Tso31 gene. Additionally, 12 egg-positive and all egg-negative samples were tested for coproantigen detection. A further 9 egg-positive fecal samples were examined using both PCRs. Of the 12 egg-positive samples tested by PCRs and coproantigen methods, 9 (75%) were positive by rrnS PCR, 3 (25%) using Tso31-nested PCR and 9 (75%) by coproantigen testing. None of the 200 egg-negative fecal samples was positive in either rrnS or Tso31-nested PCR. Twenty of the 25 egg-positive samples (80%) were positive in rrnS PCR, and DNA sequencing of PCR amplicons was obtained from 18 samples, all confirmed to be T. solium. Twelve of the 25 egg-positive samples (48%) were positive in the Tso31-nested PCR, all of which were also positive by rrnS PCR. It is suggested that species-specific diagnosis of T. solium taeniasis may be achieved by either coprological examination to detect eggs or coproantigen testing, followed by rrnS PCR and DNA sequencing to confirm the tapeworm species in egg-positive or coproantigen-positive samples.

Confirmation by necropsy of a high prevalence of porcine cysticercosis in a rural district of Madagascar

Neurocysticercosis is recognized as an important health issue in the Malagasy population. To date, investigations into prevalence of infection with the causative agent, Taenia solium, in the parasite's natural animal intermediate hosts, have relied on serological methods which have been found to be non-specific. We determined the prevalence of porcine cysticercosis among pigs from a contiguous area of the Betafo and Mandoto administrative districts, Vakinankaratra Region, Madagascar. One hundred and four slaughter-weight pigs were examined by detailed necropsy examination including slicing of the heart, tongue, masseter muscles, diaphragm and carcase musculature. Thirty-seven animals (35.6%) were found infected with T. solium, representing one of the highest rates of infection ever reported, worldwide. These findings highlight the importance of T. solium in Madagascar and support the need for increased efforts to prevent the parasite's transmission to reduce its burden on the health of the Malagasy population.

Taenia solium taeniasis and Cysticercosis Prevalence and Control Practice in China

Taenia solium taeniasis/cysticercosis is an important global food-borne zoonosis transmitted between humans and pigs. In China, the prevalence of Theridion solium taeniasis/cysticercosis has been marked decline in recent decades based on the data revealed by both national surveys and field prevalence investigations. Health education and promotion, meat inspection, and chemotherapy are unquestionably the main control measures for diseases. It is worth noting that a variety of socio-ecological variables have been identified in the process of controlling T. solium taeniasis/cysticercosis. It has become difficult for pigs to come into direct or indirect contact with or consume human excreta as pig farming practices have been shifted from traditional backyard farms to large-scale commercial pig raising systems that are still in progress. The human toilet revolution in rural areas of China has ensured hygienic separation of human excreta from contact, and thereby preventing human excreta from polluting the soil, feeds, and water. These two important fundamental preventive measures are crucial to establishing an environmental restriction between humans and pigs cannot be overlooked for interrupting or limiting T. solium transmission. In this chapter, we reviewed the epidemiology, traditional measures, and ecological determinants that significantly contributed to the dramatic decline of taeniasis/cysticercosis in China.

Stakeholders' Knowledge, Attitude, and Perceptions on the Control of Taenia solium in Kamuli and Hoima Districts, Uganda

Taenia (T.) solium is a zoonotic parasite causing three diseases: Taeniasis and cysticercosis in humans and porcine cysticercosis in pigs. Although biomedically, the transmission of the parasite can be easily interrupted at six points along the life cycle, the contextual factors that may influence the adoption of these control strategies in Uganda remain unclear. This study assessed the stakeholders' knowledge, attitudes, and perceptions relating to the six control strategies for T. solium infections in Kamuli and Hoima districts, Uganda. A total of 22 focus group discussions (FGD) were conducted with pig farmers, community leaders, pig/pork traders, animal health assistants, and human health assistants. In addition, nine key informant interviews were held with senior officials in the ministries of agriculture and health and other relevant agencies at the district level. The results showed differential, limited, and fragmented knowledge on T. solium infections among stakeholders. Pig farmers, community leaders, and pig/pork traders had almost no knowledge and were often confused regarding the differences existing between T. solium and other gastro-intestinal infections in pigs and humans. Pig confinement, pit latrine construction, coverage, maintenance, and sustained use are influenced by cultural, socio-economic, and physical/ environmental factors of the study population and area. Proper sensitisation programmes and health education interventions should target all, but with appropriately focused material to suit the different stakeholder categories. Reminders or nudges may be needed to ensure that increase in knowledge translates to changes in practise. Intervention programmes should also aim to overcome challenges created by the various contextual factors operating in the specific endemic areas.

Implementation of Taenia solium control measures in Bali, Indonesia: Survey findings and a historical overview

Historically, cysticercosis cases caused by infection with the larval stage of the Taenia solium tapeworm have occurred sporadically in Bali, with taeniasis carriers found primarily in villages located in the Kubu subdistrict of Karangasem. As Bali is a well-known tourist destination, living standards are relatively high on the island, except for an area located beneath the northeast slope of the active volcano Mt. Agung (Alt. 3031 m), which includes Kubu. Over the last 30 years, pigs originating from this area have been found with T. solium cysticerci, whereas pigs from other parts of the island have not been shown to be infected. Out of 108 individuals screened via fecal sample examination in Kubu during 2019, 3 cases of T. solium taeniasis (2.8%) were identified. There was no significant difference in taeniasis prevalence from surveys conducted in 2011-2016 (1.0%, 11/1089) (p = 0.123). Out of 110 humans and 140 pigs tested serologically in Kubu during 2019, no cases of cysticercosis were identified. This is in contrast to a seroprevalence of 4.1% (42/1025) in humans during 2011-2016 and a seroprevalence of 13.1% (43/329) in pigs during 2011-2013. Over the last decade, improved drinking water and sanitary systems have been employed in addition to health education targeting primary school children, including emphasis on washing hands before eating and after defecation. This review provides previously unpublished survey data and a historical overview of T. solium infection in Bali and offers guidance on best practices to ensure that remaining pockets of transmission are addressed.

Impact of a 3-year mass drug administration pilot project for taeniasis control in Madagascar

Taenia solium is endemic in Madagascar and presents a significant burden on the population and the health system. The parasite cycles through humans who host the adult tapeworm, and pigs that host the larval stages. Accidental infection of humans may occur with the larval stages which encyst in the nervous central system causing neurocysticercosis, a major cause of seizure disorders and a public health problem. One of the interventions to facilitate the control of the disease is mass drug administration (MDA) of the human population with taeniacide. Here we describe a pilot project conducted in Antanifotsy district of Madagascar from 2015 to 2017 where three annual rounds of MDA (praziquantel, 10mg/Kg) were undertaken in 52 villages. Changes in the prevalence of taeniasis were assessed before, during and after the treatments. A total of 221,308 treatments were given to all eligible people above 5 years of age representing a 95% coverage of the targeted population. No major adverse effects were notified related to the implementation of the MDA. The prevalence of taeniasis was measured using Kato-Katz and copro-antigen techniques. Analyses undertaken combining the results of the Kato-Katz with copro-antigen, or using the Kato-Katz results alone, showed that there was a significant reduction in taeniasis 4 months after the last MDA, but 12 months later (16 months after the last MDA) the taeniasis prevalence had returned to its original levels. Results of the pilot project emphasize the need of a multi-sectorial One-Health approach for the sustained control of T. solium.

The parasite Taenia solium causes neurocysticercosis in humans in its larval stage and is the main cause of seizure disorders in poor communities that keep pigs (the intermediate host). Diagnosis and treatment of neurocysticercosis remains beyond the reach of the general population in Madagascar. Prevention is therefore the most suitable strategy for combating this disease. Mass drug administration (MDA) is used to treat communities for several parasitic diseases such as schistosomiasis. Infection with the T. solium tapeworm in people can be treated with MDA using praziquantel. Here, we conducted a pilot project in Madagascar, giving over 220,000 treatments to people in 52 villages once per year, for 3 consecutive years. The effects on taeniasis seemed to be encouraging when assessed 4 months after finishing the treatment, but 16 months later, the parasite’s prevalence had returned to its original level. MDA was effective in providing temporary control of taeniasis, but parasite transmission was not interrupted. With respect to T. solium, this highlights the need of incorporating other interventions such as vaccination and medication in pigs, improved pig husbandry and meat inspection to tackle the whole cycle of the parasite.

Use of Veterinary Vaccines for Livestock as a Strategy to Control Foodborne Parasitic Diseases

Foodborne diseases (FBDs) are a major concern worldwide since they are associated with high mortality and morbidity in the human population. Among the causative agents of FBDs, Taenia solium, Echinococcus granulosus, Toxoplasma gondii, Cryptosporidium spp., and Trichinella spiralis are listed in the top global risk ranking of foodborne parasites. One common feature between them is that they affect domestic livestock, encompassing an enormous risk to global food production and human health from farm to fork, infecting animals, and people either directly or indirectly. Several approaches have been employed to control FBDs caused by parasites, including veterinary vaccines for livestock. Veterinary vaccines against foodborne parasites not only improve the animal health by controlling animal infections but also contribute to increase public health by controlling an important source of FBDs. In the present review, we discuss the advances in the development of veterinary vaccines for domestic livestock as a strategy to control foodborne parasitic diseases.

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

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.

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

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.

Accurate diagnosis of lesions suspected of being caused by Taenia solium in body organs of pigs with naturally acquired porcine cysticercosis

The definitive method for diagnosis of porcine cysticercosis is the detection of cysticerci at necropsy. Cysts are typically located in the striated muscle and brain. Until recently Taenia solium cysticerci have not been definitively identified in other tissue locations, despite several comprehensive investigations having been undertaken which included investigation of body organs other than muscle and brain. Recently a study conducted in Zambia reported 27% infection with T. solium in the liver of pigs with naturally acquired porcine cysticercosis, as well as some T. solium infection in the lungs and spleen of some animals. We investigated the cause of lesions in sites other than the muscle or brain in a total of 157 pigs from T. solium endemic regions of Uganda and Nepal which were subjected to extensive investigations at necropsy. Lesions which had the potential to be caused by T. solium were characterised by macroscopic and microscopic examination, histology as well as DNA characterisation by PCR-RFLP and sequencing. Lesions were confirmed as being caused by Taenia hydatigena (both viable and non-viable), by T. asiatica and Echinococcus granulosus (in Nepal) and nematode infections. No T. solium-related lesions or cysticerci were identified in any tissue other than muscle and brain. It is recommended that future evaluations of porcine cysticercosis in aberrant tissue locations include DNA analyses that take appropriate care to avoid the possibility of contamination of tissue specimens with DNA from a different tissue location or a different animal. The use of appropriate control samples to confirm the absence of cross-sample contamination is also recommended.

Can We Recommend Practical Interventions to Prevent Neurocysticercosis?

The cystiSim model was used to compare strategies for the control of Taenia solium. A three-monthly intervention in pigs for 3 years was substantially more effective than biannual treatment for taeniasis in the human population for 5 years. The intervention period could be shortened further by combining pig and human interventions.

Implementation of a practical and effective pilot intervention against transmission of Taenia solium by pigs in the Banke district of Nepal

Taenia solium is a zoonotic cestode parasite which causes human neurocysticercosis. Pigs transmit the parasite by acting as the intermediate host. An intervention was implemented to control transmission of T. solium by pigs in Dalit communities of Banke District, Nepal. Every 3 months, pigs were vaccinated with the TSOL18 recombinant vaccine (Cysvax, IIL, India)) and, at the same time, given an oral treatment with 30mg/kg oxfendazole (Paranthic 10% MCI, Morocco). The prevalence of porcine cysticercosis was determined in both an intervention area as well as a similar no intervention control area, among randomly selected, slaughter-age pigs. Post mortem assessments were undertaken both at the start and at the end of the intervention. Participants conducting the post mortem assessments were blinded as to the source of the animals being assessed. At the start of the intervention the prevalence of porcine cysticercosis was 23.6% and 34.5% in the control and intervention areas, respectively. Following the intervention, the prevalence of cysticercosis in pigs from the control area was 16.7% (no significant change), whereas no infection was detected after complete slicing of all muscle tissue and brain in animals from the intervention area (P = 0.004). These findings are discussed in relation to the feasibility and sustainability of T. solium control. The 3-monthly vaccination and drug treatment intervention in pigs used here is suggested as an effective and practical method for reducing T. solium transmission by pigs. The results suggest that applying the intervention over a period of years may ultimately reduce the number of tapeworm carriers and thereby the incidence of NCC.

Neurocysticercosis is a disease caused by a parasitic infection of the brain. The parasite responsible, Taenia solium, is transmitted by pigs where human sanitation is poor and pigs roam freely. Neurocysticercosis is responsible for many cases of epilepsy in people living in poor, developing countries. The feasibility and sustainability of implementing control measures have been major impediments to reducing the incidence of neurocysticercosis. Recently, two new commercial products have become available which together offer the possibility of interrupting the parasite’s transmission by pigs–the TSOL18 vaccine (Cysvax, IIL, India) and an oxfendazole formulation (Paranthic 10%, MCI, Morocco) licensed for use in pigs for the treatment of cysticercosis. Here we describe the impact of implementing vaccination plus drug treatment of pigs in the Banke district of Nepal. The intervention eliminated the risk of transmission of T. solium by the animals vaccinated and treated during the trial. Application of the vaccination and drug treatment program used here, possibly with strategic use of anthelmintics also in the human population, is an effective option for reducing the incidence of neurocysticercosis in Nepal and elsewhere.

Overview of Taenia solium cysticercosis in West Africa

Human and porcine cysticercosis is endemic in West Africa, where epilepsy is relatively common, but rarely reported due to fear of stigmatization. Neurocysticercosis, caused by Taenia solium, tends to affect the poor in developing countries and control is hampered by inadequate infrastructure and financial resources coupled with lack of adequate information about its significance and distribution. The risk factors for human cysticercosis are closely associated with the characteristics of smallholder or backyard pig farming systems prevalent in this region. Poverty, ignorance and lack of political will militate against successful eradication, while tools for effective diagnosis, prevention and treatment, including vaccines for pigs, are not yet available in many countries. Cysticercosis was targeted for control by The World Health Organization global plan for 2008-2015; however, measures for control are yet to be undertaken in a coordinated manner in West Africa. Diagnostic tools, including neuroimaging facilities, should be strategically situated and made accessible to rural populations in West Africa. Community education in combination with a multipronged approach consisting of vaccination of pigs using TSOL18 vaccine and treatment with oxfendazole along with mass chemotherapy of humans with praziquantel could eliminate taeniasis and should be considered. In-depth and extensive epidemiological studies are required in West Africa in order to fully elucidate the prevalence of T. solium and to support more coordinated and effective control of human and porcine cysticercosis.

Recent advancements in the control of Taenia solium: A systematic review

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.

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Combined intervention field studies demonstrate sharp decreases in disease occurrence.

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New, specific, efficient, electronic educational tools are available.

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Elimination of Taenia solium in a Peruvian endemic area has been described.

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Integration of Taenia solium control in other NTD control programs can be effective.

Improved methods to capture the total societal benefits of zoonotic disease control: Demonstrating the cost-effectiveness of an integrated control programme for Taenia solium, soil transmitted helminths and classical swine fever in northern Lao PDR

BACKGROUND

Control and elimination of zoonotic diseases requires robust information about their effect on both human and livestock health in order to enable policy formulation and the allocation of resources. This study aimed to evaluate the cost-effectiveness of controlling Taenia solium taeniasis/cysticercosis in both humans and pigs, and soil-transmitted helminths (STH) in humans by integrating their control to on-going human and animal health control programmes in northern Lao People's Democratic Republic.

METHOD

A cross-sectional study was carried out in 49 households, focusing on the prevalence of T. solium taenias/cysticercosis and soil transmitted helminths before and after a twelve month intervention. The village data was collected using a semi-structured questionnaire through a door-to-door survey. The village data was then projected to the wider northern Lao PDR population using stochastic modelling and cost-effectiveness ratio (after aggregating the net cost to capture both human and animal health parameters) and GDP per capita as a threshold, to determine the cost-effectiveness of the integrated control of T. solium taeniasis/ cysticercosis and STH, assuming linear scaling out of the intervention. The zoonotic DALY (zDALY) approach was also used as an alternative method of estimating the cost-effectiveness ratio of controlling T. solium taeniasis/cysticercosis in humans and pigs.

FINDINGS

Using cost-effectiveness analysis after aggregating the net cost and control of T. solium taeniasis/cysticercosis alone as the base case, the study found that simultaneous control of T. solium taeniasis/cysticercosis in humans and pigs, STH in humans and Classical Swine Fever (CSF) in pigs was USD 14 per DALY averted and USD 234 per zDALY averted using zDALY method hence considered highly cost-effective whereas controlling T. solium taeniasis/cysticercosis without incorporating STH and CSF was the least cost-effective (USD 3,672 per DALY averted). Additionally, the cost-effectiveness of controlling T. solium taeniasis/cysticercosis in people and pigs using zDALY as an alternative method was USD 3,662 per zDALY averted which was quite close to our findings using the aggregate net cost method.

CONCLUSION

The study showed that control of T. solium taeniasis/cysticercosis alone in humans and pigs is not cost-effective in northern Lao PDR whereas control of STH is. Consequently, integrating T. solium taeniasis/cysticercosis control with other cost-effective programmes such as STH and CSF markedly improved the cost-effectiveness of the intervention. This is especially important in low resource countries where control of zoonotic neglected tropical diseases could be integrated with the human and animal health sectors to optimize use of the limited resources.

TRIAL REGISTRATION

Australia New Zealand Clinical Trials Registry (ANZCTR) ACTRN12614001067662.

Co-occurrence of swine cysticercosis due to Taenia solium and Taenia hydatigena in ethnic minority villages at the Thai-Myanmar border

As part of the international joint projects working towards the control of taeniosis/cysticercosis in Asia Pacific, epidemiological studies on Taenia solium cysticercosis have been carried out in high-incidence populations, such as minority groups in Thailand. To assess the epidemiology of cysticercotic infections in pigs in the hill-tribe minority villages (Karen) in Tak province, Thailand, we conducted serological screening and necropsies. The patterns of antibody response to T. solium antigens were then investigated using immunoblot assays. Of the 188 pig serum samples tested for antibody responses to partially purified low-molecular-weight antigens of T. solium cyst fluid, positive responses were detected in 37 samples (19.7%). Based on these results, 16 pigs (10 seropositive and 6 seronegative) were necropsied for investigation of cysticerci and intestinal parasites. All seropositive pigs were coinfected with both T. solium and Taenia hydatigena cysticerci, except one, which was infected with T. hydatigena alone. Three of the six seronegative pigs were confirmed to be infected with T. hydatigena. Pigs infected with T. solium showed much stronger antibody responses than those infected with T. hydatigena. Our results demonstrate the co-occurrence of two swine cysticercoses due to T. solium and T. hydatigena in the studied areas. This study also reveals the importance of direct confirmation of the presence of cysticerci by necropsy after serological screening. In addition to the prevalence of swine cysticercosis in these endemic areas, our findings also reveal potential implications for the development of serological diagnostic assays for swine cysticercosis.

Human taeniasis/cysticercosis: a potentially emerging parasitic disease in Europe

Taenia saginata (T. saginata)/Taenia solium (T. solium) taeniasis/cysticercosis disease complexes remain a significant challenge for food safety and public health. Human taeniasis is an infectious disease caused by the ingestion of the metacestode larval stage, the cysticerci of T. saginata in beef or T. solium in pork. Humans can also become infected via the ingestion of T. solium eggs. In this case, the cysticerci can establish in the central nervous system, causing the infection called neurocysticercosis. T. solium is of higher importance than T. saginata because the former species can cause neurocysticercosis in humans, a major cause of neurological morbidity in the world. The taeniasis/cysticercosis complex is included in the list of neglected zoonotic diseases by the World Health Organization and Food and Agriculture Organization, with T. solium being the number one foodborne parasite; it occurs mostly in developing countries, such as regions of Asia, Africa and Latin America, where the disease remains endemic. Long absent in Western Europe and other developed countries, cysticercosis has been recently re-emerged as a result of immigration, travel and commerce. In this review, cysticercosis is presented with special emphasis on some aspects of this neglected disease: the main clinical manifestations, risk factors and epidemiology. In addition, any recent advances in diagnostic approaches and treatment are discussed. Finally, the complexities involved in the control of the disease and the need to revise current management strategies are highlighted.

Prevalence and risk factors for Taenia solium cysticercosis in school-aged children: A school based study in western Sichuan, People's Republic of China

Background

Taenia solium cysticercosis affects millions of impoverished people worldwide and can cause neurocysticercosis, an infection of the central nervous system which is potentially fatal. Children may represent an especially vulnerable population to neurocysticercosis, due to the risk of cognitive impairment during formative school years. While previous epidemiologic studies have suggested high prevalence in rural China, the prevalence in children as well as risk factors and impact of disease in low-resource areas remain poorly characterized.

Methodology/Principal findings

Utilizing school based sampling, we conducted a cross-sectional study, administering a questionnaire and collecting blood for T. solium cysticercosis antibodies in 2867 fifth and sixth grade students across 27 schools in west Sichuan. We used mixed-effects logistic regression models controlling for school-level clustering to study associations between risk factors and to characterize factors influencing the administration of deworming medication. Overall prevalence of cysticercosis antibodies was 6%, but prevalence was significantly higher in three schools which all had prevalences of 15% or higher. Students from households owning pigs (adjusted odds ratio [OR] 1.81, 95% CI 1.08–3.03), from households reporting feeding their pigs human feces (adjusted OR 1.49, 95% CI 1.03–2.16), and self-reporting worms in their feces (adjusted OR 1.85, 95% CI 1.18–2.91) were more likely to have cysticercosis IgG antibodies. Students attending high prevalence schools were more likely to come from households allowing pigs to freely forage for food (OR 2.26, 95% CI 1.72–2.98) and lacking a toilet (OR 1.84, 95% CI 1.38–2.46). Children who were boarding at school were less likely to have received treatment for gastrointestinal worms (adjusted OR 0.58, 95% CI 0.42–0.80).

Conclusions/Significance

Our study indicates high prevalences of cysticercosis antibodies in young school aged children in rural China. While further studies to assess potential for school-based transmission are needed, school-based disease control may be an important intervention to ensure the health of vulnerable pediatric populations in T. solium endemic areas.

The zoonotic tapeworm, Taenia solium, affects millions of impoverished people worldwide and can cause neurocysticercosis (NCC), an infection of the central nervous system which is potentially fatal. Hypothetically, children may be a vulnerable population to infection as neurological problems and cognitive impairment caused by NCC during formative school years may lead to poor academic performance, contributing to drop-out rates and, eventually, propagating cycles of poverty. We carried out a school-based study of T. solium cysticerosis in primary school-aged children in rural western Sichuan. Our results indicate high levels of T. solium exposure in young school-aged children in rural China. While further studies to assess disease transmission within schools are needed, school-based disease control may be an important intervention to ensure the health of pediatric populations at risk for infection.

Identification and control of sources of Taenia solium infection – the attempts to eradicate the parasite

Taenia solium is a parasite causing porcine cysticercosis and human taeniosis and cysticercosis, parasitic zoonoses with a serious public health and economic influence. It has been globally ranked as the top foodborne parasite by the Food and Agriculture Organisation of the United Nations (FAO) and the World Health Organisation (WHO). This parasite is transmitted mainly in countryside regions where animals are free roaming, having access to human faeces, and infected pork is widely available. More developed countries eliminated cysticercosis; nonetheless, there are insufficient data about the current endemicity status of T. solium, due to increased human migration from endemic areas. Formally submitted statistics on cysticercosis in pigs are extremely inadequate. This is the result of not reporting all cases of the disease by some countries and lack of molecular verification during identification of the parasite. There is a need to develop diagnostic tests with increased sensitivity and specificity. The purpose of the present review is to summarise current knowledge about diagnostic and control methods concerning T. solium infection. The article does not address the diagnostics of human cysticercosis, since there is a distinct medical field which should be discussed separately. The paper focuses mainly on identifying the sources of T. solium infection, presenting the methods to detect and control porcine cysticercosis and taeniosis in humans.

Identification and Control of Sources of Taenia Solium Infection - the Attempts To Eradicate the Parasite

Taenia solium is a parasite causing porcine cysticercosis and human taeniosis and cysticercosis, parasitic zoonoses with a serious public health and economic influence. It has been globally ranked as the top foodborne parasite by the Food and Agriculture Organisation of the United Nations (FAO) and the World Health Organisation (WHO). This parasite is transmitted mainly in countryside regions where animals are free roaming, having access to human faeces, and infected pork is widely available. More developed countries eliminated cysticercosis; nonetheless, there are insufficient data about the current endemicity status of T. solium, due to increased human migration from endemic areas. Formally submitted statistics on cysticercosis in pigs are extremely inadequate. This is the result of not reporting all cases of the disease by some countries and lack of molecular verification during identification of the parasite. There is a need to develop diagnostic tests with increased sensitivity and specificity. The purpose of the present review is to summarise current knowledge about diagnostic and control methods concerning T. solium infection. The article does not address the diagnostics of human cysticercosis, since there is a distinct medical field which should be discussed separately. The paper focuses mainly on identifying the sources of T. solium infection, presenting the methods to detect and control porcine cysticercosis and taeniosis in humans.

Metazoan Parasite Vaccines: Present Status and Future Prospects

Eukaryotic parasites and pathogens continue to cause some of the most detrimental and difficult to treat diseases (or disease states) in both humans and animals, while also continuously expanding into non-endemic countries. Combined with the ever growing number of reports on drug-resistance and the lack of effective treatment programs for many metazoan diseases, the impact that these organisms will have on quality of life remain a global challenge. Vaccination as an effective prophylactic treatment has been demonstrated for well over 200 years for bacterial and viral diseases. From the earliest variolation procedures to the cutting edge technologies employed today, many protective preparations have been successfully developed for use in both medical and veterinary applications. In spite of the successes of these applications in the discovery of subunit vaccines against prokaryotic pathogens, not many targets have been successfully developed into vaccines directed against metazoan parasites. With the current increase in -omics technologies and metadata for eukaryotic parasites, target discovery for vaccine development can be expedited. However, a good understanding of the host/vector/pathogen interface is needed to understand the underlying biological, biochemical and immunological components that will confer a protective response in the host animal. Therefore, systems biology is rapidly coming of age in the pursuit of effective parasite vaccines. Despite the difficulties, a number of approaches have been developed and applied to parasitic helminths and arthropods. This review will focus on key aspects of vaccine development that require attention in the battle against these metazoan parasites, as well as successes in the field of vaccine development for helminthiases and ectoparasites. Lastly, we propose future direction of applying successes in pursuit of next generation vaccines.

Transplastomic plants yield a multicomponent vaccine against cysticercosis

Low cost vaccines against cysticercosis are needed to fight this parasitosis, especially in developing countries. Herein polycistron arrangements were designed to accomplish the simultaneous expression of multiple protective antigens from Taenia solium in the plant cell as an attractive biofactory and delivery vehicle of vaccines. Transplastomic plants carrying synthetic polycistrons were able to simultaneously express the KETc1, KETc7, KETc12, GK1, and TSOL18/HP6-Tsol antigens; which retained their antigenicity and ability to induce humoral responses in BALB/c mice. These clones may be useful for the production of low-cost cysticercosis vaccine prototypes.

A hyperendemic focus of Taenia solium transmission in the Banke District of Nepal

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The prevalence of porcine cysticercosis was determined in pigs from the Banke District of Nepal.

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Slaughter-age animals were selected at random and underwent detailed necropsy examination.

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Thirty two of 110 animals were found to harbour T. solium cysticerci.

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This is one of the highest levels of porcine cysticercosis described for any region in the world.

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Measures are warranted to control this zoonotic disease in Nepal.

Neurocysticercosis is a major cause of epilepsy in countries where Taenia solium is endemic and the parasite is a major cause of food-borne disease globally. Pigs are the natural intermediate host involved in transmission of the parasite. T. solium is known to be endemic in Nepal, however there is limited reliable data about the prevalence of the disease in Nepal. The aim of this study was to determine accurately the prevalence of porcine cysticercosis in slaughter age pigs in an area of Nepal where pigs are known to be free-roaming. Pigs were obtained from the Udaypur Village Development Committee (VDC) and Hirminiya & Betahani VDC of the Banke district in Nepal. One hundred and ten animals of slaughter age (approximately 8–16 months old) were purchased, slaughtered and the heart, liver, brain and half the body skeletal musculature were sliced using hand knives and the number and viability of T. solium cysts determined. Thirty two of the 110 animals were found to harbour T. solium cysticerci (29%), of which 30 (27%) were found to have viable cysticerci (93% of the infected animals). This is one of the highest prevalences of porcine cysticercosis that has been reported to date from the results of necropsy on randomly selected animals. This study highlights a high rate of transmission of T. solium in the Banke District of Nepal. It encourages further investigation of human and porcine cysticercosis in Nepal, as well as implementation of efforts to reduce transmission of the parasite and the associated human disease.

Piloting the effectiveness of pig health education in combination with oxfendazole treatment on prevention and/or control of porcine cysticercosis, gastrointestinal parasites, African swine fever and ectoparasites in Angónia District, Mozambique

A community-based intervention combining health education (HE) and treatment of pigs for control of porcine cysticercosis (PC), gastrointestinal (GI) helminths, African swine fever (ASF) and external parasites was tested involving six villages of resource-poor smallholder pig farmers. Farmers and pigs of six rural villages were randomly allocated into group 1 (HE), which served as controls, and group 2 (HE + OFZ) pigs received a single oral dose of 30 mg/kg OFZ. Farmers were trained in pig health, housing and feeding. The proportion of farmers with confined pigs, the adoption rate of the introduced pig pen, the sero-prevalence of PC and ASF, the prevalence and intensity of GI nematodes and the prevalence of ectoparasites were measured at 9, 15 and 24 months after initiation and compared to a baseline survey to seek the effectiveness of the interventions. There was no clear effect of the intervention on the sero-prevalence of PC, but analysis of the rate of change in prevalence between the two groups showed significant effect with the rate of change to lower prevalence in the HE + OFZ group compared to the HE group. Although HE managed to improve the farmer's knowledge in the control and prevention of ASF and ectoparasites, there was no significant reduction in the sero-prevalence of ASF and the prevalence of ectoparasites throughout the two-year period. The reported ineffectiveness of the intervention in this study suggested that more research is needed to develop more effective methods for controlling PC, ASF and pig parasites.

Seroprevalence and awareness of porcine cysticercosis across different pig production systems in south-central Cambodia

Background

Taeniasis/cysticercosis, caused by the pork tapeworm Taenia solium, represents an important public health and economic burden in endemic countries. However, there is a paucity of data on infection among pigs in many parts of Southeast Asia, particularly Cambodia. We aimed to estimate seroprevalence of porcine cysticercosis, and investigate husbandary practices and knowledge of the disease among livestock workers, across different pig sector units in south-central Cambodia.

Methods

A cross sectional survey was conducted among pig smallholders, commercial farms, slaughterhouses and traders/middlemen from south-central Cambodia, selected through multistage sampling in proportion to local pig populations sizes. Questionnaires were administered to 163 pig workers to obtain data pig production, trading and slaughtering practices. Sera from 620 pigs were tested for Taenia antigens using a commercial ELISA-based test. Associations between seroprevalence and pig husbandry practices were assessed using generalised linear mixed models, adjusting for random-effects at herd-level.

Results

Of 620 pigs sampled, 29 (4.7%) tested positive for Taenia antigens. Seropositivity was associated with type of pig sector unit (P = 0.008), with the highest seroprevalence among pigs sampled from traders/middlemen (16.7%; 95% CI: 4.4%-37.8%), smallholders (7.6%; 95% CI: 3.8%-14.1%) and slaughterhouses (4.1%; 95% CI: 2.0%-7.5%), while none of the pigs sampled from small/medium or large commercial farms tested positive. Although the vast majority of pigs were penned, practices that might facilitate human-to-pig transmission, such as use of household waste and surface water sources to feed pigs, were prevalent among smallholders. However these were not found to be significantly associated with infection. Of 163 interviewed pig workers, 115 (70.5%) were aware of porcine cysticercosis, and 78 (47.8%) also knew it could affect humans. Twenty-six (16.0%) reported having noticed lesions typical of cysticercosis in their pigs.

Conclusions

Despite most pigs being kept confined in pens rather than raised in free-roaming systems, porcine cysticercosis appears to be endemic in south-central Cambodia and is associated with smallholder production. Further investigation is needed to identify which Taenia species are causing infections among pigs, and how seroprevalence and zoonotic risk may vary across the country, to understand the risks to public health and assess where interventions might be needed.

Neglected tropical diseases: progress towards addressing the chronic pandemic

The concept of neglected tropical diseases (NTDs) emerged more than a decade ago and has been recognised as a valid way to categorise diseases that affect the poorest individuals. Substantial progress in control and elimination has been achieved and policy momentum has been generated through continued bilateral, philanthropic, and non-governmental development organisation (NGDO) support, and donations of drugs from pharmaceutical companies. WHO has defined a Roadmap to reach 2020 targets, which was endorsed by member states in a World Health Assembly Resolution in 2013. NTDs have been included within the Sustainable Development Goal targets and are a crucial component of universal health coverage, conceptualised as "leaving no one behind". WHO reported that more than 1 billion people in 88 countries have benefited from preventive chemotherapy in 2014. The research agenda has defined the need for affordable products (diagnostics, drugs and insecticides). However challenges such as insecurity and weak health systems continue to prevail in the poorest countries, inhibiting progress in scaling up and also in achieving Roadmap goals.

Cysticercosis/taeniasis endemicity in Southeast Asia: Current status and control measures

The parasitic zoonoses cysticercosis/taeniasis is among the 17 major Neglected Tropical Diseases (NTDs) identified by the WHO as a focus for research and control. It is caused by a larval stage (cysticercus) infection of Taenia solium tapeworm in both humans and pigs. Cysticercosis occurs in many resource-poor countries, especially those with warm and mild climates in the regions of Latin America (LA), Asia and Sub-Saharan Africa (SSA). The prevalence of human cysticercosis is marked in those areas where individuals are traditionally keen to consume raw or insufficiently cooked pork and/or where the husbandry of pigs is improper. The worldwide burden of cysticercosis is unclear and notably, large-scale control initiatives are lacking in all regions. This review focuses on the current endemic status of cysticercosis caused by T. solium infection in both humans and pigs living in 13 Southeast Asian countries. We will also emphasize epidemiological data as well as prevention and control of human neurocysticercosis.

Reprint of "Assessing the impact of a joint human-porcine intervention package for Taenia solium control: Results of a pilot study from northern Lao PDR"

Following confirmation that a remote village of approximately 300 inhabitants in northern Lao PDR was hyperendemic for the Neglected Tropical Disease Taenia solium, a pilot human-porcine therapeutic control intervention was implemented between October 2013 and November 2014. Mass drug administration with a three day albendazole 400mg protocol was offered to all eligible humans in October 2013 and March 2014. At these times, and again in October 2014, eligible village pigs received the anti-cysticercosis TSOL18 vaccination and an oral dose of oxfendazole anthelmintic at 30mg/kg, both repeated one month later. Community and individual human taeniasis prevalences were estimated via copro-antigen ELISA of volunteered human faecal samples prior to October 2013, and again in January 2015, in order to examine the short term impact of the intervention.

Control of Taenia solium taeniasis/cysticercosis: The best way forward for sub-Saharan Africa?

Taenia solium taeniasis/cysticercosis is a neglected parasitic zoonosis with significant economic and public health impacts. Control measures can be broadly grouped into community health education, improvements in hygiene and sanitary conditions, proper meat handling at household and community level, improved standards of meat inspection, pig management, treatment of individual patients and possibly human populations, and treatment and/or vaccination of porcine populations. This manuscript looks critically into currently existing control options and provides suggestions on which (combination of) tools would be most effective in the control of T. solium taeniasis/cysticercosis in sub-Saharan Africa. Field data and disease transmission simulations suggest that implementation of a single intervention control strategy will not lead to a satisfactory reduction of disease morbidity or transmission. A feasible strategy to combat T. solium taeniasis/cysticercosis would include a combination of approaches focussing on both human (health education and treatment) and animal host (management, treatment and vaccination), which can vary for different communities and different geographical locations. Selection of the specific strategy depends on cost-effectiveness analyses based on solid field data, currently unavailable, though urgently needed; as well as on health priorities and resources of the country. A One Health approach involving medical, veterinary, environmental and social sectors is essential for T. solium to be controlled and eventually eliminated. Finally the success of any intervention is largely dependent on the level of societal and political acceptance, commitment and engagement.

The societal cost of Taenia solium cysticercosis in Tanzania

Taenia solium is a zoonotic parasite prevalent in many low income countries throughout Latin America, Asia and sub-Saharan Africa, including Tanzania. The parasite is recognized as a public health threat; however the burden it poses on populations of Tanzania is unknown. The aim of this study was to estimate the societal cost of T. solium cysticercosis in Tanzania, by assessing both the health and economic burden. The societal cost of T. solium cysticercosis was assessed in humans and pigs based on data obtained by a systematic review. Experts' opinion was sought in cases where data were not retrievable. The health burden was assessed in terms of annual number of neurocysticercosis (NCC) associated epilepsy incident cases, deaths and disability-adjusted life years (DALYs), while the economic burden was assessed in terms of direct and indirect costs imposed by NCC-associated epilepsy and potential losses due to porcine cysticercosis. Based on data retrieved from the systematic review and burden assessments, T. solium cysticercosis contributed to a significant societal cost for the population. The annual number of NCC-associated epilepsy incident cases and deaths were 17,853 (95% Uncertainty Interval (UI), 5666-36,227) and 212 (95% UI, 37-612), respectively. More than 11% (95% UI, 6.3-17) of the pig population was infected with the parasite when using tongue examination as diagnostic method. For the year 2012 the number of DALYs per thousand person-years for NCC-associated epilepsy was 0.7 (95% UI, 0.2-1.6). Around 5 million USD (95% UI, 797,535-16,933,477) were spent due to NCC-associated epilepsy and nearly 3 million USD (95% UI, 1,095,960-5,366,038) were potentially lost due to porcine cysticercosis. Our results show that T. solium imposes a serious public health, agricultural and economic threat for Tanzania. We urge that a One Health approach, which involves the joint collaboration and effort of veterinarians, medical doctors, agricultural extension officers, researchers and relevant governmental agencies, is taken to find sustainable solutions for prevention, control and elimination of T. solium.

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

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.

Taenia solium is the leading cause of preventable epilepsy and the highest ranking foodborne parasite in terms of disease burden worldwide. Currently there are no large scale control programmes implemented against T. solium, but efficacious intervention tools are there, making control programmes the next step forward. Because of the zoonotic properties of the parasite, existing in both humans and pigs, a combination of intervention tools is likely to be needed. cystiSim is an agent-based disease model that provides insight into which intervention tools, and the frequency of administration of these tools, are needed to yield an effect on disease prevalence. cystiSim is a valuable tool in designing future control programmes and will assist in the elimination of T. solium as a public health problem.

Vaccination against parasites - status quo and the way forward

Although vaccination against various pathogens is integral to health management of swine, vaccines against parasites have not yet been commercialized for the use in pigs. The incentive to develop and commercialize anti-parasitic vaccines in swine are twofold; on the one hand parasitic diseases which are economically important, such as ascarosis and neonatal coccidiosis, could be controlled in a sustainable manner; on the other hand, the transmission of zoonotic parasites, such as Toxoplasma gondii or Cysticercus cellulosae, could be effectively interrupted. Although experimental research indicates that vaccination against a number of porcine parasites is feasible, development and commercialization of potential vaccines so far has been very slow, as our knowledge on the host-parasite interplay in porcine parasitic infections is still very limited. In the light of growing concerns regarding consumer health and antiparasitic drug resistance, however, it is timely to re-direct R&D efforts to the development of biological control options.

Monitoring the outcomes of interventions against Taenia solium: options and suggestions

There is an increasing interest in reducing the incidence of human neurocysticercosis, caused by infection with the larval stage of Taenia solium. Several intervention trials are currently assessing various options for control of T. solium transmission. A critical aspect of these trials will be the evaluation of whether the interventions have been successful. However, there is no consensus about the most appropriate or valuable methods that should be used. Here, we undertake a critical assessment of the diagnostic tests which are currently available for human T. solium taeniasis and human and porcine cysticercosis, as well as their suitability for evaluation of intervention trial outcomes. Suggestions are made about which of the measures that are available for evaluation of T. solium interventions would be most suitable, and which methodologies are the most appropriate given currently available technologies. Suggestions are also made in relation to the most urgent research needs in order to address deficiencies in current diagnostic methods.

Assessing the impact of a joint human-porcine intervention package for Taenia solium control: Results of a pilot study from northern Lao PDR

Following confirmation that a remote village of approximately 300 inhabitants in northern Lao PDR was hyperendemic for the Neglected Tropical Disease Taenia solium, a pilot human-porcine therapeutic control intervention was implemented between October 2013 and November 2014. Mass drug administration with a three day albendazole 400mg protocol was offered to all eligible humans in October 2013 and March 2014. At these times, and again in October 2014, eligible village pigs received the anti-cysticercosis TSOL18 vaccination and an oral dose of oxfendazole anthelmintic at 30mg/kg, both repeated one month later. Community and individual human taeniasis prevalences were estimated via copro-antigen ELISA of volunteered human faecal samples prior to October 2013, and again in January 2015, in order to examine the short term impact of the intervention.

Taenia solium Taeniasis and Cysticercosis in Southeast Asia

Human taeniasis/cysticercosis caused by the pork tapeworm Taenia solium has been identified as a potentially eradicable disease by the International Task Force for Disease Eradication of the World Health Organization. In southeast Asia, T. solium taeniasis/cysticercosis is considered one of the major neglected tropical diseases afflicting the region. In the last few decades, a considerable effort has been invested toward establishing the epidemiology and burden of disease in several southeast Asian countries. Moreover, further evidence is emerging as to understanding the dynamics of disease transmission and cultural, political, and socioeconomic factors influencing the success of control and eradication efforts within the region. However, despite major collaborations by several champion groups, advances have been slow and little remains known about the complete epidemiology of taeniasis/cysticercosis and the barriers to programmatic success. This review article aims to address the above issues with a further focus on the challenges to control and eradicate taeniasis/cysticercosis within the southeast Asia region.

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

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.

Eliminating the Neglected Tropical Diseases: Translational Science and New Technologies

Today, the World Health Organization recognizes 17 major parasitic and related infections as the neglected tropical diseases (NTDs). Despite recent gains in the understanding of the nature and prevalence of NTDs, as well as successes in recent scaled-up preventive chemotherapy strategies and other health interventions, the NTDs continue to rank among the world’s greatest global health problems. For virtually all of the NTDs (including those slated for elimination under the auspices of a 2012 London Declaration for NTDs and a 2013 World Health Assembly resolution [WHA 66.12]), additional control mechanisms and tools are needed, including new NTD drugs, vaccines, diagnostics, and vector control agents and strategies. Elimination will not be possible without these new tools. Here we summarize some of the key challenges in translational science to develop and introduce these new technologies in order to ensure success in global NTD elimination efforts.

Anamnestic responses in pigs to the Taenia solium TSOL18 vaccine and implications for control strategies

Specific antibody responses were assessed in pigs immunized with the Taenia solium vaccine TSOL18. Anti-TSOL18 responses were compared 2 weeks after secondary immunization, where the interval between primary and secondary immunization was 4, 8, 12, 16 or 20 weeks. All animals responded to the vaccine and there was no diminution in antibody responses in animals receiving their second injection after an interval up to 20 weeks. Pigs receiving vaccinations at an interval of 12 weeks developed significantly increased antibody responses compared with animals receiving immunizations 4 weeks apart (P = 0.046). The ability to deliver TSOL18 vaccination effectively where the revaccination schedule can be delayed for up to 12-16 weeks in pigs increases the options available for designing T. solium control interventions that incorporate TSOL18 vaccination.

Tapeworm cysts in the brain: can we prevent it happening?

Imagine the consternation; you are a member of an orthodox Jewish family and you and another family member are diagnosed with larvae of a pork tapeworm in your brain. You have recurrent seizures as a result. Ridiculous? Not for members of a Jewish community in New York where a Mexican domestic worker harbouring a Taenia solium tapeworm had apparently contaminated the family's food with eggs from her tapeworm1.

Evaluation of activity of triclabendazole against Taenia solium metacestode in naturally infected pigs

OBJECTIVE

To assess the efficacy of triclabendazole (TCBZ) in porcine cysticercosis.

METHODS

Eighteen naturally infected cysticercosis pigs were divided into 3 groups of 6 individuals each. The first group was treated orally with TCBZ at a single dose of 30 mg/kg of body weight, the second group was treated orally with oxfendazole at a single dose of 30 mg/kg of body weight and the third group received a placebo (control group). All animals were kept under the same management conditions. The pigs were euthanized 17 wk post-treatment and the number of surviving cysts in muscles was assessed and compared between groups.

RESULTS

All pigs treated with oxfendazole had only degenerated cysts in their carcasses. In contrast, TCBZ had very little effect against the parasitic cysts. Cysts from pigs in the TCBZ group looked apparently normal after treatment. However, histological evaluation showed a mild to moderate degree of inflammation.

CONCLUSIONS

TCBZ is not an efficacious drug against Taenia solium cysticercosis in swine using a single dose.

Sensitivity of partial carcass dissection for assessment of porcine cysticercosis at necropsy

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Taenia solium cyst distribution was determined in the carcass musculature of 209 naturally exposed pigs.

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81% of the infected animals had cysts in the tongue, masticatory muscles and/or heart muscles.

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Dissection of a limited proportion of the muscles of pigs could be used to assess the outcomes of cysticercosis control.

Many interventions against Taenia solium are evaluated by assessing changes in the prevalence of porcine cysticercosis ascertained by carcass dissection. Financial and logistical difficulties often prohibit dissection of entire pig carcasses. We assessed 209 pigs from rural areas of Cameroon and Peru for the presence of T. solium cysticerci and determined the distribution of parasites within the musculature of infected animals. Considering the presence of cysts in the tongue, masticatory muscles and heart, 31 of the 38 (81%) naturally infected animals were identified as having cysts. Dissection of only the tongue, masticatory muscles and heart provides a relatively sensitive and highly specific method for diagnosis of porcine cysticercosis.

Recent advances and perspectives in molecular epidemiology of Taenia solium cysticercosis

Cysticercosis caused by accidental ingestion of eggs of Taenia solium is spreading all over the world through globalization and is one of the most neglected, neglected tropical diseases (NTDs) or neglected zoonotic diseases (NZDs). In the present study, the reason why T. solium cysticercosis has been neglected is discussed at first, and followed with an overview on the most recent advances and perspectives in molecular approaches for epidemiology of T. solium taeniasis/cysticercosis, since although taeniasis does not constitute recognized zoonoses, transmission and complete development are dependent on human definitive hosts. Main topics are discussions on (1) the two, Asian and Afro/American, genotypes of T. solium, (2) comparative analysis of mitochondrial (haploid) and nuclear (diploid) genes, and (3) the presence of hybrids of these two genotypes which indicates out-crossing of two genotypes in hermaphrodite tapeworms in Madagascar. Additional topics are on (4) the usefulness of phylogeographic analyses to discuss where the infection was acquired from, and (5) miscellaneous unsolved topics around these genetic diversity of T. solium.

Flatworms have lost the right open reading frame kinase 3 gene during evolution

All multicellular organisms studied to date have three right open reading frame kinase genes (designated riok-1, riok-2 and riok-3). Current evidence indicates that riok-1 and riok-2 have essential roles in ribosome biosynthesis, and that the riok-3 gene assists this process. In the present study, we conducted a detailed bioinformatic analysis of the riok gene family in 25 parasitic flatworms (platyhelminths) for which extensive genomic and transcriptomic data sets are available. We found that none of the flatworms studied have a riok-3 gene, which is unprecedented for multicellular organisms. We propose that, unlike in other eukaryotes, the loss of RIOK-3 from flatworms does not result in an evolutionary disadvantage due to the unique biology and physiology of this phylum. We show that the loss of RIOK-3 coincides with a loss of particular proteins associated with essential cellular pathways linked to cell growth and apoptosis. These findings indicate multiple, key regulatory functions of RIOK-3 in other metazoan species. Taking advantage of a known partial crystal structure of human RIOK-1, molecular modelling revealed variability in nucleotide binding sites between flatworm and human RIOK proteins.

The present situation and towards the prevention and control of neurocysticercosis on the tropical island, Bali, Indonesia

Neurocysticercosis (NCC), which is caused by accidental ingestion of eggs of the pork tapeworm, Taenia solium, was common in Bali, Indonesia until the early 1990s. However, improved education on hygiene and sanitation, a move to keeping pigs indoors, and improvement of economic and living conditions have substantially reduced the occurrence of NCC in Bali. Since 2011, T. solium tapeworm carriers (T. solium taeniasis) and heavily infected pigs and dogs have exclusively been detected from villages in mountainous regions of northeastern Bali where NCC and ocular cysticercosis (OCC) cases have also been identified. In response to this continued area of high infection, a one-day workshop was convened to discuss how to prevent and control this potentially lethal zoonotic parasitic infection in Bali. This review presents an overview of the current status of T. solium taeniasis and cysticercosis in Indonesia and proposes a strategy for the prevention and control of this zoonosis in Bali.

Vaccination against helminth parasite infections

Helminth parasites infect over one fourth of the human population and are highly prevalent in livestock worldwide. In model systems, parasites are strongly immunomodulatory, but the immune system can be driven to expel them by prior vaccination. However, no vaccines are currently available for human use. Recent advances in vaccination with recombinant helminth antigens have been successful against cestode infections of livestock and new vaccines are being tested against nematode parasites of animals. Numerous vaccine antigens are being defined for a wide range of helminth parasite species, but greater understanding is needed to define the mechanisms of vaccine-induced immunity, to lay a rational platform for new vaccines and their optimal design. With human trials underway for hookworm and schistosomiasis vaccines, a greater integration between veterinary and human studies will highlight the common molecular and mechanistic pathways, and accelerate progress towards reducing the global health burden of helminth infection.