Induction of protection against porcine cysticercosis by vaccination with recombinant oncosphere antigens

Characterisation of protective vaccine antigens from the thiol-containing components of excretory/secretory material of Ostertagia ostertagi

Previous vaccination trials have demonstrated that thiol proteins affinity purified from Ostertagia ostertagi excretory-secretory products (O. ostertagi ES-thiol) are protective against homologous challenge. Here we have shown that protection induced by this vaccine was consistent across four independent vaccine-challenge experiments. Protection is associated with reduced cumulative faecal egg counts across the duration of the trials, relative to control animals. To better understand the diversity of antigens in O. ostertagi ES-thiol we used high-resolution shotgun proteomics to identify 490 unique proteins in the vaccine preparation. The most numerous ES-thiol proteins, with 91 proteins identified, belong to the sperm-coating protein/Tpx/antigen 5/pathogenesis-related protein 1 (SCP/TAPS) family. This family includes previously identified O. ostertagi vaccine antigens O. ostertagi ASP-1 and ASP-2. The ES-thiol fraction also has numerous proteinases, representing three distinct classes, including: metallo-; aspartyl- and cysteine proteinases. In terms of number of family members, the M12 astacin-like metalloproteinases, with 33 proteins, are the most abundant proteinase family in O. ostertagi ES-thiol. The O. ostertagi ES-thiol proteome provides a comprehensive database of proteins present in this vaccine preparation and will guide future vaccine antigen discovery projects.

Development and evaluation of time-resolved rapid immunofluorescence test for detection of TSOL18 specific antibody in porcine cysticercosis infections

BACKGROUND

Porcine cysticercosis, a serious zoonotic parasitic disease, is caused by the larvae of Taenia solium and has been acknowledged by the World Organization for Animal Health. The current detection methods of Cysticercus cellulosae cannot meet the needs of large-scale and rapid detection in the field. We hypothesized that the immunofluorescence chromatography test strip (ICS) for detecting Cysticercus cellulosae, according to optimization of a series of reaction systems was conducted, and sensitivity, specificity, and stability testing, and was finally compared with ELISA. This method utilizes Eu3+-labeled time-resolved fluorescent microspheres (TRFM) coupled with TSOL18 antigen to detect TSOL18 antibodies in infected pig sera.

RESULTS

ICS and autopsy have highly consistent diagnostic results (n = 133), as determined by Cohen's κ analysis (κ = 0.925). And the results showed that the proposed ICS are high sensitivity (0.9459) with specificity (0.9792). The ICS was unable to detect positive samples of other parasites. It can be stored for at least six months at 4℃.

CONCLUSIONS

In summary, we established a TRFM-ICS method with higher sensitivity and specificity than indirect ELISA. Results obtained from serum samples can be read within 10 min, indicating a rapid, user-friendly test suitable for large-scale field detection.

The mRNA Vaccine Technology Era and the Future Control of Parasitic Infections

Despite intensive long-term efforts, with very few exceptions, the development of effective vaccines against parasitic infections has presented considerable challenges, given the complexity of parasite life cycles, the interplay between parasites and their hosts, and their capacity to escape the host immune system and to regulate host immune responses. For many parasitic diseases, conventional vaccine platforms have generally proven ill suited, considering the complex manufacturing processes involved and the costs they incur, the inability to posttranslationally modify cloned target antigens, and the absence of long-lasting protective immunity induced by these antigens. An effective antiparasite vaccine platform is required to assess the effectiveness of novel vaccine candidates at high throughput. By exploiting the approach that has recently been used successfully to produce highly protective COVID mRNA vaccines, we anticipate a new wave of research to advance the use of mRNA vaccines to prevent parasitic infections in the near future. This article considers the characteristics that are required to develop a potent antiparasite vaccine and provides a conceptual foundation to promote the development of parasite mRNA-based vaccines. We review the recent advances and challenges encountered in developing antiparasite vaccines and evaluate the potential of developing mRNA vaccines against parasites, including those causing diseases such as malaria and schistosomiasis, against which vaccines are currently suboptimal or not yet available.

The Genomes of Two Strains of Taenia crassiceps the Animal Model for the Study of Human Cysticercosis

Human cysticercosis by Taenia solium is the major cause of neurological illness in countries of Africa, Southeast Asia, and the Americas. Publication of four cestode genomes (T. solium, Echinococcus multilocularis, E. granulosus and Hymenolepis microstoma) in the last decade, marked the advent of novel approaches on the study of the host-parasite molecular crosstalk for cestode parasites of importance for human and animal health. Taenia crassiceps is another cestode parasite, closely related to T. solium, which has been used in numerous studies as an animal model for human cysticercosis. Therefore, characterization of the T. crassiceps genome will also contribute to the understanding of the human infection. Here, we report the genome of T. crassiceps WFU strain, reconstructed to a noncontiguous finished resolution and performed a genomic and differential expression comparison analysis against ORF strain. Both strain genomes were sequenced using Oxford Nanopore (MinION) and Illumina technologies, achieving high quality assemblies of about 107 Mb for both strains. Dotplot comparison between WFU and ORF demonstrated that both genomes were extremely similar. Additionally, karyotyping results for both strains failed to demonstrate a difference in chromosome composition. Therefore, our results strongly support the concept that the absence of scolex in the ORF strain of T. crassiceps was not the result of a chromosomal loss as proposed elsewhere. Instead, it appears to be the result of subtle and extensive differences in the regulation of gene expression. Analysis of variants between the two strains identified 2,487 sites with changes distributed in 31 of 65 scaffolds. The differential expression analysis revealed that genes related to development and morphogenesis in the ORF strain might be involved in the lack of scolex formation.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

Advances in the treatment, diagnosis, control and scientific understanding of taeniid cestode parasite infections over the past 50 years

In the past 50 years, enormous progress has been made in the diagnosis, treatment and control of taeniid cestode infections/diseases and in the scientific understanding thereof. Most interest in this group of parasites stems from the serious diseases that they cause in humans. It is through this lens that we summarize here the most important breakthroughs that have made a difference to the treatment of human diseases caused by these parasites, reduction in transmission of the taeniid species associated with human disease, or understanding of the parasites' biology likely to impact diagnosis or treatment in the foreseeable future. Key topics discussed are the introduction of anti-cestode drugs, including benzimidazoles and praziquantel, and the development of new imaging modalities that have transformed the diagnosis and post-treatment monitoring of human echinococcoses and neurocysticercosis. The availability of new anti-cestode drugs for use in dogs and a detailed understanding of the transmission dynamics of Echinococcus granulosus sensu lato have underpinned successful programs that have eliminated cystic echinococcosis in some areas of the world and greatly reduced the incidence of infection in others. Despite these successes, cystic and alveolar echinococcosis and neurocysticercosis continue to be prevalent in many parts of the world, requiring new or renewed efforts to prevent the associated taeniid infections. Major advances made in the development of practical vaccines against E. granulosus and Taenia solium will hopefully assist in this endeavour, as might the understanding of the parasites' biology that have come from an elucidation of the nuclear genomes of each of the most important taeniid species causing human diseases.

Vaccine for a neglected tropical disease Taenia solium cysticercosis: fight for eradication against all odds

INTRODUCTION

Taenia solium infection is among the 17 most neglected tropical diseases identified by World Health Organization and to be eradicated by 2030. This parasite infects the central nervous system (Neurocysticercosis [NCC]) and intestine [Taeniasis]). NCC is the most frequent cause of acquired epilepsy in endemic regions and Taeniasis is responsible for the widespread malnutrition and abdominal discomfort among children. Epilepsy caused by T. solium is preventable and the total elimination of NCC can be achieved by good hygiene, mass therapy, and most importantly vaccination of pigs or humans. Vaccine for pig is available but not widely in use and for humans it's still elusive.

AREA COVERED

Several vaccine candidates for porcine cysticercosis have been tried like TSOL18, SP3Vac, KETc7, TSOL45, etc. with good success in the limited field trial. This review highlights some seminal contributions for the anti-cestode vaccine, the associated challenges, current status, suggestive future directions, and the need of vaccine for human use.

EXPERT OPINION

Though several vaccines are available, none is being widely used due to lack of awareness, economic constraints, accessibility, etc. Hence, there is a need for a newer, economic, and reliable vaccine for humans or pigs use to reduce the disease burden.

Immunodiagnostic usefulness of monoclonal antibodies specific to conformational epitopes of Taenia solium oncosphere protein TSOL18

Taenia solium oncosphere protein TSOL18 is the host-protective antigen against porcine cysticercosis. Little attention has been given to use it as target molecule in immunodiagnostic tests. The objective of this paper is to describe the immunodiagnostic potential of monoclonal antibodies (MoAbs) raised against conformational epitopes of TSOL18. Three murine IgG1 MoAbs (25D12C1, 21C2D2, 10H1F2) against three different conformational epitopes of TSOL18 were produced and evaluated with an inhibition enzyme-linked immunosorbent assay (i-ELISA) for the detection of anti-TSOL18 and anti-oncosphere antibodies. Serum samples from pigs immunized with TSOL18 inhibited the binding of the three MoAbs to TSOL18 antigen in i-ELISA. The highest inhibition of anti-TSOL18 antibodies in immunized pigs was observed with MoAb 25D12C1. Ten field sera (12.19%) from 82 non-vaccinated and non-infected pigs showed anti-oncosphere antibodies inhibiting the binding of MoAb 25D12C1. Anti-oncosphere antibodies in pigs experimentally infected with T. solium eggs inhibited the binding of MoAb 25D12C1 from 2 to 8 week-post infection. It is concluded that MoAb 25D12C1 has excellent immunodiagnostic potentials to detect anti-oncosphere antibodies in the intermediate hosts at early exposure to T. solium eggs. Further investigations on potential use of MoAb 25D12C1 in a capture antigen ELISA for the detection of post-oncospheral antigens in infected pigs cannot be overemphasized.

•

We describe the potential usefulness of the monoclonal antibody 25D12C1 to TSOL18 protein.

•

Serum samples from pigs immunized with TSOL18 inhibited the binding of 25D12C1 in an inhibition enzyme-linked immunosorbent assay (i-ELISA) for the detection of anti-TSOL18 and anti-oncosphere antibodies.

•

Anti-oncosphere antibodies in pigs infected with T. solium eggs inhibited also the binding of 25D12C1.

•

It is concluded that MoAb i-ELISA using 25D12C1 has the potential to identify animals exposed to T. solium infection.

Neurocysticercosis: Current Perspectives on Diagnosis and Management

Porcine cysticercosis, human taeniasis, and (neuro)cysticercosis are endemic in many low- and middle-income countries (LMIC) where they present a significant health burden to affected communities. Neurocysticercosis (NCC) is one of the leading causes of human epilepsy in many hyperendemic regions in Latin America, Asia, and sub-Saharan Africa. The World Health Organization (WHO) reports an estimated 2.5-8.3 million cases of NCC annually with a disability-adjusted life year (DALY) burden of 2.8 million, but as for all neglected tropical diseases (NTDs), these values are likely to be underestimated. Diagnosis of NCC is complex and most accurately diagnosed using clinical neuroimaging that is unavailable in most hyperendemic regions in LMIC. On January 28, 2021, WHO will launch its road map for the NTDs' "Ending the neglect to attain the Sustainable Development Goals: a road map for neglected tropical diseases 2021-2030." Taeniasis/cysticercosis is targeted for control success considered as steady increase in the number of countries with intensified control in hyperendemic areas [increasing from 2 (3%) in 2020 to 4 (6%) in 2023, to 9 (14%) by 2025, and to 17 (27%) by 2030]. Cross-cutting targets that include 100% access to at least basic water supply, sanitation, and hygiene in areas endemic for NTDs and 75% integrated treatment coverage for preventative chemotherapy will additionally impact on the taeniasis/cysticercosis/NCC complex. With no vaccine available for humans, prevention of infection depends on communication to the public of the life cycle of a complex zoonosis to promote behavior change, underpinned by practical control measures including treatment of human taeniasis and (neuro)cysticercosis with albendazole and praziquantel [widely used as part of the mass drug administration (MDA) deworming programs], surgery where appropriate, and effective vaccination and deworming for pigs supported by meat inspection. Here, we review recent advances in tools and implementation for Taenia solium taeniasis/(neuro)cysticercosis (TSTC) control and milestones on the onward path to elimination.

Data-driven analyses of behavioral strategies to eliminate cysticercosis in sub-Saharan Africa

Background

The multi-host taeniosis/cysticercosis disease system is associated with significant neurological morbidity, as well as economic burden, globally. We investigated whether lower cost behavioral interventions are sufficient for local elimination of human cysticercosis in Boulkiemdé, Sanguié, and Nayala provinces of Burkina Faso.

Methodology/Principal findings

Province-specific data on human behaviors (i.e., latrine use and pork consumption) and serological prevalence of human and pig disease were used to inform a deterministic, compartmental model of the taeniosis/cysticercosis disease system. Parameters estimated via Bayesian melding provided posterior distributions for comparing transmission rates associated with human ingestion of Taenia solium cysticerci due to undercooking and human exposure to T. solium eggs in the environment. Reductions in transmission via these pathways were modeled to determine required effectiveness of a market-focused cooking behavior intervention and a community-led sanitation and hygiene program, independently and in combination, for eliminating human cysticercosis as a public health problem (<1 case per 1000 population). Transmission of cysticerci due to consumption of undercooked pork was found to vary significantly across transmission settings. In Sanguié, the rate of transmission due to undercooking was 6% higher than that in Boulkiemdé (95% CI: 1.03, 1.09; p-value < 0.001) and 35% lower than that in Nayala (95% CI: 0.64, 0.66; p-value < 0.001). We found that 67% and 62% reductions in undercooking of pork consumed in markets were associated with elimination of cysticercosis in Nayala and Sanguié, respectively. Elimination of active cysticercosis in Boulkiemdé required a 73% reduction. Less aggressive reductions of 25% to 30% in human exposure to Taenia solium eggs through sanitation and hygiene programs were associated with elimination in the provinces.

Conclusions/Significance

Despite heterogeneity in effectiveness due to local transmission dynamics and behaviors, education on the importance of proper cooking, in combination with community-led sanitation and hygiene efforts, has implications for reducing morbidity due to cysticercosis and neurocysticercosis.

It is important to consider context-specific behaviors and transmission pathways when designing scalable and sustainable intervention strategies for neglected tropical diseases (NTDs). To reduce the morbidity and mortality associated with cysticercosis, suites of interventions have been recommended but are inconsistently implemented due to cost and feasibility-related constraints. This study investigated the potential of a cooking intervention to interrupt transmission via undercooked pork in marketplaces of Burkina Faso. The sensitivity of Taenia solium parasite to temperatures attainable via improved cooking strategies provides a low-cost, human-centered approach to prevent consumption of infected pork meals. By accounting for differential behavior and the relative role of this transmission route across three provinces, we show how the potential of cysticercosis elimination (as a public health problem) varies across behavior-focused interventions. Further investigation into intervention strategies against human and pig cysticercosis warrants data-driven analyses that account for local variation in transmission behaviors.

Zoonotic Taenia infections with focus on cysticercosis due to Taenia solium in swine and humans

Zoonotic taeniasis caused by the adult stage of Taenia solium, Taenia saginata or Taenia asiatica are considered neglected tropical diseases by the World Health Organization. The life cycle of these 3 metazoan species is very similar and includes an intermediate host: pigs in the case of T. solium and T. asiatica, and cattle in the case of T. saginata. By eating meat (pork/T. solium, T. asiatica; beef/T. saginata) containing live cysticerci, humans develop taeniasis, which is practically asymptomatic but is the main risk factor for intermediate hosts to become infected. T. saginata causes bovine cysticercosis, while T. solium and T. asiatica cause swine cysticercosis, of veterinary and economic importance. T. solium cysticerci cause neurological disease in humans: neurocysticercosis. Cysticerci develop after ingesting microscopic eggs released from a human tapeworm carrier. Here we describe the life stages of the parasites, diagnosis, pathogenesis, symptomatology of neurocysticercosis, and prevention and control measures. Highlighting the need to validate diagnostic tools, treatments and vaccination in endemic areas, with the challenge of addressing the most vulnerable populations that lack resources. If people understand the transmission route, avoid eating uncooked or insufficiently cooked meat and have adequate hygienic habits, the life cycle of the 3 zoonotic Taenia species may be interrupted. In addition, we describe the growing field of immune response and immunomodulation elicited by the parasites, which may provide essential tools for diagnosis, treatment, control of taeniasis/cysticercosis, as well as for identification of parasite-derived immunomodulators that could aid in the treatment of emerging inflammatory diseases worldwide.

TSOL18 vaccine and oxfendazole for control of Taenia solium cysticercosis in pigs: A field trial in endemic areas of Tanzania

A field trial was conducted in Tanzania to determine the effectiveness of TSOL18 vaccine used concurrently with oxfendazole (OFZ), and of OFZ alone, on T. solium cysticercosis determined by organ and half carcase dissection of slaughter age pigs. This study followed a quasi-experimental group design. Suitable trial sites were randomly allocated to either treatment group T1 (OFZ treatment alone [30mg/kg, Paranthic 10%]) or T2 (TSOL18 [1ml, Cysvax] plus OFZ). Three 4-monthly treatments were administered to eligible pigs. A random selection of pigs were necropsied at baseline and at endline, 2–3.5 months after the final treatment. Additionally, untreated pigs from T1 and T2 areas were necropsied at endline to provide contemporaneous comparisons with T1 and T2 pigs. Baseline prevalence of viable T. solium cysticerci for T1 was 25.5% (Exact 95% CI: 13.9, 40.3; n = 12/47), and for T2 was 12.0% (CI: 6.4, 20.0; n = 12/100). At endline, prevalence was 2.8% for T1 (CI: 0.1, 14.5, n = 1/36) and 0% for T2 (CI: 0, 4.7, n = 0/77). Among untreated pigs, three had viable cysticerci, one from T1 area (12.5%, CI: 0.3, 52.7; n = 1/8) and two from T2 area (5.7%, CI: 0.7, 19.2, n = 2/35). Fisher’s exact test showed significant changes in prevalence from baseline to endline in both groups (T1: p = 0.005, T2: p = 0.001). Firth’s penalized Maximum Likelihood method suggested the changes were not significant relative to their controls (T1: p = 0.245, T2: p = 0.076). These findings showed a significant reduction in the prevalence of viable cysticerci from baseline to endline after both interventions. However, the changes could not be definitively attributed to the interventions due, in part, to small numbers of control pigs. Concurrent administration of the TSOL18 and OFZ cleared infection among assessed pigs whereas infection remained after treatment with OFZ only. Further studies including larger sample sizes would be required for more definitive conclusions. A One Health approach is recommended for rapid and sustainable impact.

The pork tapeworm T. solium affects the health and income of poor people in endemic areas. A pig vaccine—TSOL18, and a drug—oxfendazole (OFZ) present options for its control. In this study we assessed the effectiveness of the two tools against the parasite in pigs. We provided one group of pigs (T1) with a concurrent administration of TSOL18 and OFZ, and another group (T2) with OFZ only, in three rounds at 4 months intervals. We compared infection prevalence before and after the interventions by detection of cysticerci through carcase dissections. In addition, untreated pigs from the T1 and T2 areas were also sacrificed to serve as controls. We found a significant reduction in prevalence within the groups after the interventions. However, the reductions were not significant when compared with the reductions in the control groups, hence could not be definitively attributed to the interventions. Further, concurrent administration of TSOL18 and OFZ cleared infection among assessed pigs whereas OFZ alone did not clear the infection. Further studies would be required to make more definitive conclusions. We advocate for a One Health approach for a more rapid and sustainable impact.

Taenia solium insulin receptors: promising candidates for cysticercosis treatment and prevention

Insulin signaling pathway is an ancient and highly conserved pathway known to play critical roles in cell growth, control and metabolic regulation. In this study, we identified and characterized two insulin receptor genes (TsIR-1316 and TsIR-4810) from Taenia solium. TsIR-1316 was grouped with E. multilocularis insulin receptor (EmIR-1) and TsIR-4810 was closer to Taenia pisiformis insulin-like growth factor receptor (TpIR) on the same branch with a very high bootstrap value. TsIR-1316 was located on the integument of larvae and adult worms, as well as the ovary of adults and eggs. Alternatively, TsIR-4810 was located in the parenchyma and reproductive organs of the adult worms. By using in vitro cultivation systems with Cysticercus pisiformis as a model, we demonstrated that anti-TsIRs-LBD antibodies could effectively block the insulin signaling pathway, resulting in reduced phosphorylation of the insulin receptor as well as lower levels of glucose uptake and glycogen synthesis. The rabbits immunized with TsIR-1316-LBD, TsIR-4810-LBD and TsIR-1316-LBD + TsIR-4810-LBD produced protection against infection of T. pisiformis as demonstrated by a 94.6%, 96% and 80% reduction of establishment of larvae, respectively. These data suggested that TsIR-1316-LBD and TsIR-4810-LBD are promising vaccine candidates or novel drug targets against swine cysticercosis.

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.

How to eliminate taeniasis/cysticercosis: porcine vaccination and human chemotherapy (Part 2)

BACKGROUND

The application of effective vaccines against pig cysticercosis and mass chemotherapy against pig cysticercosis and human taeniasis have shown the feasibility of interrupting the parasite's life cycle in endemic areas.

METHODS

A mathematical model that divides the population into susceptible, infected, and vaccinated individuals is formulated. The model is based upon the life cycle of the parasite. Computer numerical simulation experiments to evaluate the impact of pig vaccination under different vaccination schedules, and combined intervention strategies including pig vaccination and anthelmintic treatment against human taeniasis are carried out.

RESULTS

Vaccination against either pig cysticercosis or against human taeniasis will influence the transmission dynamics not only among vaccinees but also the dynamics of the other hosts as well. When the protective efficacy and/or the coverage rate is less than 100%, different mass interventions like vaccinating the pig population twice in combination with chemotherapeutic treatment against human taeniasis, the elimination of the infection in both pigs and humans can also be achieved.

CONCLUSIONS

Our mathematical model has the potential for planning, and designing effective intervention strategies including both mass vaccination and/or chemotherapeutic treatment to eliminate pig cysticercosis, human taeniasis and human neurocysticercosis. The model can be adapted to any given community with mild, moderate endemicity, or even in hyperendemic regions.

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.

Mathematical model of the life cycle of taenia-cysticercosis: transmission dynamics and chemotherapy (Part 1)

BACKGROUND

Taenia solium is the aetiological agent of human taeniasis, pig cysticercosis and human neurocysticercosis, which are serious public health problems, especially in developing countries.

METHODS

A mathematical model of the transmission dynamics of taeniasis-cysticercosis is formulated. The model consists of a coupled system of differential equations, which are density-dependent equations for describing the flow of the parasite through the life cycle. The model is hybrid since it comprises deterministic equations with stochastic elements which describe changes in the mean parasite burden and incorporates the overall pattern of the parasites' distribution.

RESULTS

Sensitivity and bifurcation analyses were carried out to determine the range of values of the model. The model can reproduce the observed epidemiological patterns of human taeniasis, pig and human cysticercosis. For example, for a wide range of parameter values, the mean intensity of adult worms tends to rapidly stabilize in one parasite per individual host. From this model, we also derived a Susceptible-Infected model to describe the prevalence of infection in humans and pigs. Chemotherapeutic interventions against pig cysticercosis or human taeniasis may reduce rapidly and effectively the mean intensity of human taeniasis, pig cysticercosis and human cysticercosis. This effect can be achieved even if the protective efficacy of the drug is of the order of 90% and the coverage rate is 90%. This means that health in humans infected either with adult worms or cysticerci may be achieved by the application of anthelmintic drugs against pig cysticercosis. However, treatment against human cysticercosis alone, does not influence neither human teniasis nor pig cysticercosis. This is because human cysticercosis infection does not influence the value of the basic reproductive number (Ro).

CONCLUSIONS

Even coverage of 100% in the administration of anthelmintics did not eliminate the infection. Then elimination of the infection in all hosts does not seem a feasible goal to achieve by administering only chemotherapeutic interventions. Throughout the manuscript a discussion of our model in the context of other models of taeniasis-cysticercosis is presented.

Analysis of Immune Responses in Mice Orally Immunized with Recombinant pMG36e-SP-TSOL18/Lactococcus lactis and pMG36e-TSOL18/Lactococcus lactis Vaccines of Taenia solium

Cysticercosis is a cosmopolitan zoonotic parasitic disease infected by larval of Taenia solium (T. solium). Several drugs for the treatment of cysticercosis, such as praziquantel, albendazole, and mebendazole, have certain toxicity and side effects. Considering that there is no vaccine available, we studied a new vaccine for cysticercosis in this study. The complete TSOL18 gene and the optimized SP-TSOL18 gene fragments were obtained using PCR-based accurate synthesis method. The secretory and intracellular recombinant pMG36e-SP-TSOL18/Lactococcus lactis (L. lactis) and pMG36e-TSOL18/L. lactis vaccines of T. solium were prepared. Immune responses in mice orally immunized with these two recombinant L. lactis vaccines were analyzed by the determination of specific antibodies (IgG, IgG1, IgG2a, and sIgA) in serum, spleen lymphocyte proliferation, and cytokines (IL-2, IFN-γ, IL-4, and IL-10) in spleen lymphocyte culture supernatant. Our results showed that, after the first immunization, in these two recombinant L. lactis vaccine groups, the levels of serum specific IgG, IgG2a, and IgG1 increased on 14–56 d and reached the highest level on days 42, 42, and 28, respectively. The level of specific sIgA of intestinal mucosa also increased on 14–56 d and reached the highest level on day 42. The level of spleen lymphocyte proliferation increased on 14–56 d and reached the highest level on day 42. The levels of IL-2, IFN-γ, IL-4, and IL-10 in spleen lymphocyte culture supernatant increased on 14–56 d and reached the highest level on days 42, 42, 28, and 28, respectively. These results indicated that the recombinant pMG36e-SP-TSOL18/L. lactis and pMG36e-TSOL18/L. lactis vaccines can induce specific cellular, humoral, and mucosal immune responses in mice with oral vaccination. More importantly, the recombinant pMG36e-SP-TSOL18/L. lactis vaccine has a better immune effect. In summary, these results demonstrated the possibility of using L. lactis strain as a vector to deliver protective antigens of T. solium.

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.

Mapping the residual incidence of taeniasis and cysticercosis in Colombia, 2009-2013, using geographical information systems: Implications for public health and travel medicine

BACKGROUND

In Colombia, taeniasis and cysticercosis have been significantly reduced over the past decades, however still reported with implications for public health and travel medicine.

METHODS

An observational, retrospective study, in which the incidence of taeniasis and cysticercosis (ICD-10 codes B68s/B69s) in Colombia, 2009-2013, was estimated based on data extracted from the Individual Health Records System (Registro Individual de Prestación de Servicios, RIPS) was performed. The Geographic Information System (GIS) generated national maps showing the distribution of taeniasis and cysticercosis by department by year.

RESULTS

During the period, 3626 cases were reported (median 796/year), for a cumulative crude national rate of 7.7 cases/100,000pop; 58.2% corresponded to male; 57% were <40 year-old (10.2% < 9.9 year-old). Cases were 57.6% neurocysticercosis, the rest were taeniasis due to T. solium, T. saginata, ocular cysticercosis and cysticerci in other organs. Bolivar, a touristic department, had the highest cumulated incidence rate (16.17 cases/100,000pop), as also evident across the map series developed in this study.

CONCLUSION

Despite the limitations of this study, data presented provide recent estimates of national taeniasis and cysticercosis incidence in the country useful in public health and for travel medicine practitioners, as some highly touristic areas presented higher disease incidence. Improved control, particularly of taeniasis, should be an attainable goal, which among other strategies would require improved sanitation and health education to prevent transmission, but also enhanced surveillance.

Exploiting Helminth-Host Interactomes through Big Data

Helminths facilitate their parasitic existence through the production and secretion of different molecules, including proteins. Some helminth proteins can manipulate the host's immune system, a phenomenon that is now being exploited with a view to developing therapeutics for inflammatory diseases. In recent years, hundreds of helminth genomes have been sequenced, but as a community we are still taking baby steps when it comes to identifying proteins that govern host-helminth interactions. The information generated from genomic, immunomic, and proteomic studies, as well as from cutting-edge approaches such as proteogenomics, is leading to a substantial volume of big data that can be utilised to shed light on fundamental biology and provide solutions for the development of bioactive-molecule-based therapeutics.

Modelling the risk of Taenia solium exposure from pork produced in western Kenya

The tapeworm Taenia solium is the parasite responsible for neurocysticercosis, a neglected tropical disease of public health importance, thought to cause approximately 1/3 of epilepsy cases across endemic regions. The consumption of undercooked infected pork perpetuates the parasite’s life-cycle through the establishment of adult tapeworm infections in the community. Reducing the risk associated with pork consumption in the developing world is therefore a public health priority. The aim of this study was to estimate the risk of any one pork meal in western Kenya containing a potentially infective T. solium cysticercus at the point of consumption, an aspect of the parasite transmission that has not been estimated before. To estimate this, we used a quantitative food chain risk assessment model built in the @RISK add-on to Microsoft Excel. This model indicates that any one pork meal consumed in western Kenya has a 0.006 (99% Uncertainty Interval (U.I). 0.0002–0.0164) probability of containing at least one viable T. solium cysticercus at the point of consumption and therefore being potentially infectious to humans. This equates to 22,282 (99% U.I. 622–64,134) potentially infective pork meals consumed in the course of one year within Busia District alone. This model indicates a high risk of T. solium infection associated with pork consumption in western Kenya and the work presented here can be built upon to investigate the efficacy of various mitigation strategies for this locality.

Taenia solium is a serious zoonotic helminth which is thought to be responsible for approximately 1/3^rd of epilepsy cases in the developing world. The work presented in this paper aimed to understand what the risk is of acquiring T. solium taeniosis from pork slaughtered and consumed in western Kenya. In order to do this we built a stochastic risk assessment model to investigate the safety of pork reaching the consumer in terms of the risk of having viable T. solium cysts in any one portion of meat consumed. We found that pork represents a high risk product in this study area and therefore control strategies are urgently needed to reduce the public health risk posed by this product.

Assessing the impact of intervention strategies against Taenia solium cysticercosis using the EPICYST transmission model

BACKGROUND

The pork tapeworm, Taenia solium, and associated human infections, taeniasis, cysticercosis and neurocysticercosis, are serious public health problems, especially in developing countries. The World Health Organization (WHO) has set goals for having a validated strategy for control and elimination of T. solium taeniasis/cysticercosis by 2015 and interventions scaled-up in selected countries by 2020. Timely achievement of these internationally-endorsed targets requires that the relative benefits and effectiveness of potential interventions be explored rigorously within a quantitative framework.

METHODS

A deterministic, compartmental transmission model (EPICYST) was developed to capture the dynamics of the taeniasis/cysticercosis disease system in the human and pig hosts. Cysticercosis prevalence in humans, an outcome of high epidemiological and clinical importance, was explicitly modelled. A next generation matrix approach was used to derive an expression for the basic reproduction number, R 0. A full sensitivity analysis was performed using a methodology based on Latin-hypercube sampling partial rank correlation coefficient index.

RESULTS

EPICYST outputs indicate that chemotherapeutic intervention targeted at humans or pigs would be highly effective at reducing taeniasis and cysticercosis prevalence when applied singly, with annual chemotherapy of humans and pigs resulting, respectively, in 94 and 74% of human cysticercosis cases averted. Improved sanitation, meat inspection and animal husbandry are less effective but are still able to reduce prevalence singly or in combination. The value of R 0 for taeniasis was estimated at 1.4 (95% Credible Interval: 0.5-3.6).

CONCLUSIONS

Human- and pig-targeted drug-focussed interventions appear to be the most efficacious approach from the options currently available. The model presented is a forward step towards developing an informed control and elimination strategy for cysticercosis. Together with its validation against field data, EPICYST will be a valuable tool to help reach the WHO goals and to conduct economic evaluations of interventions in varying epidemiological settings.

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.

Elimination of Taenia solium Transmission in Northern Peru

BACKGROUND

Taeniasis and cysticercosis are major causes of seizures and epilepsy. Infection by the causative parasite Taenia solium requires transmission between humans and pigs. The disease is considered to be eradicable, but data on attempts at regional elimination are lacking. We conducted a three-phase control program in Tumbes, Peru, to determine whether regional elimination would be feasible.

METHODS

We systematically tested and compared elimination strategies to show the feasibility of interrupting the transmission of T. solium infection in a region of highly endemic disease in Peru. In phase 1, we assessed the effectiveness and feasibility of six intervention strategies that involved screening of humans and pigs, antiparasitic treatment, prevention education, and pig replacement in 42 villages. In phase 2, we compared mass treatment with mass screening (each either with or without vaccination of pigs) in 17 villages. In phase 3, we implemented the final strategy of mass treatment of humans along with the mass treatment and vaccination of pigs in the entire rural region of Tumbes (107 villages comprising 81,170 people and 55,638 pigs). The effect of the intervention was measured after phases 2 and 3 with the use of detailed necropsy to detect pigs with live, nondegenerated cysts capable of causing new infection. The necropsy sampling was weighted in that we preferentially included more samples from seropositive pigs than from seronegative pigs.

RESULTS

Only two of the strategies implemented in phase 1 resulted in limited control over the transmission of T. solium infection, which highlighted the need to intensify the subsequent strategies. After the strategies in phase 2 were implemented, no cyst that was capable of further transmission of T. solium infection was found among 658 sampled pigs. One year later, without further intervention, 7 of 310 sampled pigs had live, nondegenerated cysts, but no infected pig was found in 11 of 17 villages, including all the villages in which mass antiparasitic treatment plus vaccination was implemented. After the final strategy was implemented in phase 3, a total of 3 of 342 pigs had live, nondegenerated cysts, but no infected pig was found in 105 of 107 villages.

CONCLUSIONS

We showed that the transmission of T. solium infection was interrupted on a regional scale in a highly endemic region in Peru. (Funded by the Bill and Melinda Gates Foundation and others.).

Pediatric neurocysticercosis: current challenges and future prospects

Neurocysticercosis (NCC) is an acquired infection of the nervous system caused by encysted larvae of Taenia solium. It is a major cause of epilepsy in the tropics and the commonest cause of focal seizures in North Indian children. T. solium teniasis-cysticercosis is considered a parasitic "Neglected Tropical Diseases" endemic throughout Southeast Asia. NCC in children has pleomorphic manifestations depending on the location, number and viability of the cysts, and host response. Even with advancing knowledge of the disease manifestations, many aspects related to diagnosis and treatment, particularly in children, still remain controversial and pose challenges to clinical practice. There is no gold standard test to diagnose NCC and the management recommendations are still emerging. This review provides an overview of diagnosis of NCC in children and its management with special focus on current challenges and future prospects.

Towards the development of an oral vaccine against porcine cysticercosis: expression of the protective HP6/TSOL18 antigen in transgenic carrots cells

The Taenia solium HP6/TSOL18 antigen was produced in carrot cells, yielding an immunogenic protein that induced significant protection in an experimental murine model against T. crassiceps cysticercosis when orally administered. This result supports the potential of HP6/TSOL18-carrot as a low-cost anti-cysticercosis vaccine candidate. Cysticercosis is a zoonosis caused by Taenia solium that can be prevented by interrupting the parasite life cycle through pig vaccination. Several injectable vaccine candidates have been reported, but the logistic difficulties and costs for its application limited its use in nationwide control programs. Oral plant-based vaccines can deal with this limitation, because of their easy administration and low cost. A stable expression of the HP6/TSOL18 anti-T. solium cysticercosis protective antigen in carrot calli transformed with an optimized transgene is herein reported. An antigen accumulation up to 14 µg g(-1) of dry-weight biomass was achieved in the generated carrot lines. Mouse immunization with one of the transformed calli induced both specific IgG and IgA anti-HP6/TSOL18 antibodies. A statistically significant reduction in the expected number of T. crassiceps cysticerci was observed in mice orally immunized with carrot-made HP6/TSOL18, in a similar extent to that obtained by subcutaneous immunization with recombinant HP6/TSOL18 protein. In this study, a new oral plant-made version of the HP6/TSOL18 anti-cysticercosis vaccine is reported. The vaccine candidate should be further tested against porcine cysticercosis.

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.

Isolated intramuscular cysticercosis: Clinicopathological features, diagnosis and management - A review

Cysticercosis is an emerging parasitic disease affecting worldwide population. There is large volume of data present in the literature for neurocysticercosis. The isolated intramuscular involvement of cysticercosis is uncommon and there are only sporadic case reports available. There is no review available in the literature which gives in detail clinicoradiological features and management of isolated intramuscular cysticercosis. Knowledge about such a presentation is important especially in developing countries and to differentiate the condition from a variety of other similar conditions.

Managing neurocysticercosis: challenges and solutions

Taenia solium neurocysticercosis (NCC) is a major cause of neurological morbidity in the world. Variability in the neuropathology and clinical presentation of NCC often make it difficult to diagnose and manage. Diagnosis of NCC can be challenging especially in endemic and resource-limited countries where laboratory and imaging techniques are often lacking. NCC management can also be challenging as current treatment options are limited and involve symptomatic agents, antiparasitic agents, or surgery. Although antiparasitic treatment probably reduces the number of active lesions and long-term seizure frequency, its efficacy is limited and strategies to improve treatment regimens are warranted. Treatment decisions should be individualized in relation to the type of NCC. Initial measures should focus on symptomatic management, with antiparasitic therapy only to be considered later on, when appropriate. Symptomatic treatment remains the cornerstone in NCC management which should not only focuses on epilepsy, but also on other manifestations that cause considerable burden (recurrent headaches, cognitive decline). Accurate patients’ categorization, better antiparasitic regimens, and definition of new clinical outcomes for trials on NCC could improve management quality and prognosis of NCC. Prevention strategies targeting tapeworm carriers and infected pigs are yielding good results in local models. If local elimination of transmission is confirmed and replicated, this will open the door to cysticercosis eradication efforts worldwide.

Occurrence of porcine cysticercosis in free-ranging pigs delivered to slaughter points in Arapai, Soroti district, Uganda

Poverty, hunger and the need for production of pigs with meagre or zero inputs have made most farmers release their pigs to range freely, thus creating a pig-human cycle that maintains Taenia solium, the pig tapeworm and cause of porcine cysticercosis, in the ecosystem. A preliminary study was designed to establish the prevalence of porcine cysticercosis by postmortem examination of the tongue and carcass of free-range pigs from February to April 2014 in Arapai subcounty, Soroti district, eastern Uganda. The tongue of each pig was extended and examined before deep incisions were made and the cut surfaces were examined. The rest of the carcasses were examined for cysts. Out of 178 pigs examined, 32 were qualitatively positive for porcine cysticercosis, representing a prevalence of 18.0%. This high prevalence represents a marked risk to the communities in the study area of neurocysticercosis, a debilitating parasitic zoonosis. Proper human waste disposal by use of pit latrines, confinement of free-range pigs and treatment with albendazole and oxfendazole are recommended.

Optimized codon usage enhances the expression and immunogenicity of DNA vaccine encoding Taenia solium oncosphere TSOL18 gene

Cysticercosis due to larval cysts of Taenia solium, is a serious public health problem affecting humans in numerous regions worldwide. The oncospheral stage-specific TSOL18 antigen is a promising candidate for an anti-cysticercosis vaccine. It has been reported that the immunogenicity of the DNA vaccine may be enhanced through codon optimization of candidate genes. The aim of the present study was to further increase the efficacy of the cysticercosis DNA vaccine; therefore, a codon optimized recombinant expression plasmid pVAX1/TSOL18 was developed in order to enhance expression and immunogenicity of TSOL18. The gene encoding TSOL18 of Taenia solium was optimized, and the resulting opt-TSOL18 gene was amplified and expressed. The results of the present study showed that the codon-optimized TSOL18 gene was successfully expressed in CHO-K1 cells, and immunized mice vaccinated with opt-TSOL18 recombinant expression plasmids demonstrated opt‑TSOL18 expression in muscle fibers, as determined by immunohistochemistry. In addition, the codon-optimized TSOL18 gene produced a significantly greater effect compared with that of TSOL18 and active spleen cells were markedly stimulated in vaccinated mice. 3H-thymidine incorporation was significantly greater in the opt-TSOL18 group compared with that of the TSOL18, pVAX and blank control groups (P<0.01). In conclusion, the eukaryotic expression vector containing the codon-optimized TSOL18 gene was successfully constructed and was confirmed to be expressed in vivo and in vitro. The expression and immunogenicity of the codon-optimized TSOL18 gene were markedly greater compared with that of the un-optimized gene. Therefore, these results may provide the basis for an optimized TSOL18 gene vaccine against cysticercosis.

Clinical symptoms, diagnosis, and treatment of neurocysticercosis

The infection of the nervous system by the cystic larvae of Taenia solium (neurocysticercosis) is a frequent cause of seizure disorders. Neurocysticercosis is endemic or presumed to be endemic in many low-income countries. The lifecycle of the worm and the clinical manifestations of neurocysticercosis are well established, and CT and MRI have substantially improved knowledge of the disease course. Improvements in immunodiagnosis have further advanced comprehension of the pathophysiology of this disease. This knowledge has led to individualised treatment approaches that account for the involvement of parenchymal or extraparenchymal spaces, the number and form of parasites, and the extent of degeneration and associated inflammation. Clinical investigations are focused on development of effective treatments and reduction of side-effects induced by treatment, such as seizures, hydrocephalus, infarcts, and neuroinjury.

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.

Coadministration of protoxin Cry1Ac from Bacillus thuringiensis with metacestode extract confers protective immunity to murine cysticercosis

The Bacillus thuringiensis Cry1Ac protoxin (pCry1Ac) is a promising mucosal immunogen and adjuvant that induces protective immunity against Naegleria fowleri and malaria infection models. We determined whether pCry1Ac acted as a protective adjuvant against infection with Taenia crassiceps. BALB/C mice were thrice i.p. immunized with (i) pCry1Ac, (ii) metacestode extract, (iii) extract + pCry1Ac or (iv) vehicle, challenged with metacestodes on day 26 and then sacrificed 35 days later. Cysticerci in the peritoneal cavity were counted, while the serum antibody response and cytokines were analysed after immunization and during infection. Only immunization with pCry1Ac plus extract conferred a significant protection (up to 47%). This group presented fluctuating antibody peaks during infection and the highest IgG1 and IgM titres. Immunization with extract alone elicited high IgG1 and the highest IgG2a responses after 25 days of infection, while nonimmunized mice presented a poor, mixed-Th1/Th2 response during infection. Sharp peaks of TNFα and IFN-γ occurred immediately after the first immunization with extract, especially in the presence of pCry1Ac, but not after the challenge, while in the control and pCry1Ac-alone groups, cytokines were only detected after the challenge. The data support the protective-adjuvant effect of co-administration of pCry1Ac in cysticercosis.

Evolution, molecular epidemiology and perspectives on the research of taeniid parasites with special emphasis on Taenia solium

Human cysticercosis is known since old historical times in Greece and China; however, human infections by tapeworms have accompanied human beings for more that hundred thousand years. The disease is tightly bound to poverty and lack of hygiene, and has been eradicated in developed countries, but continues being a public health problem in developing countries of Latin-American, Sub-Saharan Africa and Asia, and is also remerging in a number of non endemic countries. It is considered a neglected disease. Here we revise a number of key scientific contributions on taeniid biology that open new avenues for more effective approaches to the control of cysticercosis. The evolution of flatworms and class Cestoda is analyzed, with special emphasis on the emergence of taeniid parasites and the colonization of the human species by tapeworms. The complex molecular host-parasite interplay in this relationship as result of co-evolution between two distantly related organisms. The relevant host and parasite's factors, in the prospect of identifying species-specific molecular markers useful in epidemiological studies carried out in endemic countries. The new possibilities arising with the characterization of the genomes for several species of tapeworms, including a deeper understanding of these organisms, as well as improved tools for diagnosis, vaccination and drug treatment. The need to revise the current control and management strategies for this tropical neglected disease.

Validity of the Enzyme-linked Immunoelectrotransfer Blot (EITB) for naturally acquired porcine cysticercosis

The Enzyme-linked Immunoelectrotransfer Blot (EITB) has been used widely as a screening test for Taenia solium cysticercosis in swine. However, the relation between seropositivity and infection in pig populations from endemic areas has not been well defined. The aim of this study is to relate EITB seropositivity with infection and infection burden, analyse the trade-off between sensitivity and specificity with various cut-off points for the EITB assay, and finally describe the serology changes in a cohort of rural pigs raised under natural conditions. A group of 107 pigs that were used as controls during a vaccination field trial in Peru was our study population. The prevalence of porcine cysticercosis determined by necropsy examination was 16.82% (18/107) in these animals. Using EITB reactivity to ≥ 1 band as a cut-off point for the assay, the sensitivity was 88.89% (65.29-98.62, 95% CI) and the specificity was 48.31% (37.59-59.16, 95% CI). Comparing other cut-off points, involving up to as many as 7 reactive bands, a reactivity of ≥ 3 bands provided the best trade-offs in sensitivity and specificity. Using this cut-off point for the assay, the sensitivity was 77.77% (52.36-93.59, 95% CI) and the specificity was 76.40% (66.22-84.76, 95% CI). A significant association was found between cyst counts over 100 cysts and reactivity to ≥ 3 bands in the EITB assay (Fisher's exact test, p<0.05). The results of this study suggest that the use of the EITB assay to study porcine cysticercosis may require setting different cut-offs under field and experimental conditions, and depending upon the objective of the screening process.

Characterization of the carbohydrate components of Taenia solium oncosphere proteins and their role in the antigenicity

This study examines the carbohydrate composition of Taenia solium whole oncosphere antigens (WOAs), in order to improve the understanding of the antigenicity of the T. solium. Better knowledge of oncosphere antigens is crucial to accurately diagnose previous exposure to T. solium eggs and thus predict the development of neurocysticercosis. A set of seven lectins conjugates with wide carbohydrate specificity were used on parasite fixations and somatic extracts. Lectin fluorescence revealed that D-mannose, D-glucose, D-galactose and N-acetyl-D-galactosamine residues were the most abundant constituents of carbohydrate chains on the surface of T. solium oncosphere. Lectin blotting showed that posttranslational modification with N-glycosylation was abundant while little evidence of O-linked carbohydrates was observed. Chemical oxidation and enzymatic deglycosylation in situ were performed to investigate the immunoreactivity of the carbohydrate moieties. Linearizing or removing the carbohydrate moieties from the protein backbones did not diminish the immunoreactivity of these antigens, suggesting that a substantial part of the host immune response against T. solium oncosphere is directed against the peptide epitopes on the parasite antigens. Finally, using carbohydrate probes, we demonstrated for the first time that the presence of several lectins on the surface of the oncosphere was specific to carbohydrates found in intestinal mucus, suggesting a possible role in initial attachment of the parasite to host cells.

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

Neurocysticercosis continues to be a major health burden on humans living in many regions of the world, despite the availability of highly effective taeniacides and identification of the cause, Taenia solium, as being potentially eradicable. Several T. solium control trials have been undertaken, generally achieving limited success and none that has been fully documented has achieved what was demonstrated to be a sustainable level of disease control. Pigs act as intermediate hosts for T. solium and two new control tools have become available for application in pigs – single-dose oxfendazole treatment of porcine cysticercosis and the TSOL18 vaccine. Three potential intervention scenarios for pigs are compared for control of cysticercosis, using either oxfendazole or vaccination. A control scenario involving vaccination plus oxfendazole treatment delivered at 4 monthly intervals was predicted to achieve the best outcome, with no pigs slaughtered at 12 months of age having viable T. solium cysticerci. Now that new control tools are available, there are opportunities to concentrate research attention on evaluation of novel control scenarios leading to the implementation of effective and sustainable control programmes and a reduction in the global burden of neurocysticercosis.

Priorities for research and control of cestode zoonoses in Asia

Globally, cestode zoonoses cause serious public health problems, particularly in Asia. Among all neglected zoonotic diseases, cestode zoonoses account for over 75% of global disability adjusted life years (DALYs) lost. An international symposium on cestode zoonoses research and control was held in Shanghai, China between 28th and 30th October 2012 in order to establish joint efforts to study and research effective approaches to control these zoonoses. It brought together 96 scientists from the Asian region and beyond to exchange ideas, report on progress, make a gap analysis, and distill prioritizing settings with a focus on the Asian region. Key objectives of this international symposium were to agree on solutions to accelerate progress towards decreasing transmission, and human mortality and morbidity caused by the three major cestode zoonoses (cystic echinococcosis, alveolar echinococcosis, and cysticercosis); to critically assess the potential to control these diseases; to establish a research and validation agenda on existing and new approaches; and to report on novel tools for the study and control of cestode zoonoses.

Prevention and control of Taenia solium taeniasis/cysticercosis in Peru

Taenia solium is endemic in most of the world, causing seizures and other neurological symptoms. Transmission is mainly maintained in rural areas by a human to pig cycle. Despite claims on its eradicability, sustainable interruption of transmission has not yet been reported. This manuscript reviews the conceptual basis for control, available diagnostic and control tools, and recent experiences on control in the field performed in Peru along the past decade.

Development of the S3Pvac vaccine against porcine Taenia solium cysticercosis: a historical review

Herein we present a review of our research dealing with vaccination against experimental and naturally acquired porcine Taenia solium cysticercosis using Taenia crassiceps-derived antigens. Results strongly support that the different versions of S3Pvac vaccine are indeed effective against porcine T. solium cysticercosis. Immunological results related to vaccination prove that protection is at least partially mediated by specific immunity. The data also support the validity of T. crassiceps murine cysticercosis as an effective tool to identify vaccine candidates against some metacestode infections.

Edible vaccines against veterinary parasitic diseases--current status and future prospects

Protection of domestic animals against parasitic infections remains a major challenge in most of the developing countries, especially in the surge of drug resistant strains. In this circumstance vaccination seems to be the sole practical strategy to combat parasites. Most of the presently available live or killed parasitic vaccines possess many disadvantages. Thus, expression of parasitic antigens has seen a continued interest over the past few decades. However, only a limited success was achieved using bacterial, yeast, insect and mammalian expression systems. This is witnessed by an increasing number of reports on transgenic plant expression of previously reported and new antigens. Oral delivery of plant-made vaccines is particularly attractive due to their exceptional advantages. Moreover, the regulatory burden for veterinary vaccines is less compared to human vaccines. This led to an incredible investment in the field of transgenic plant vaccines for veterinary purpose. Plant based vaccine trials have been conducted to combat various significant parasitic diseases such as fasciolosis, schistosomosis, poultry coccidiosis, porcine cycticercosis and ascariosis. Besides, passive immunization by oral delivery of antibodies expressed in transgenic plants against poultry coccidiosis is an innovative strategy. These trials may pave way to the development of promising edible veterinary vaccines in the near future. As the existing data regarding edible parasitic vaccines are scattered, an attempt has been made to assemble the available literature.

State of the art of Taenia solium as compared to Taenia asiatica

Three species of tapeworms infect humans in their adult stage (Taenia solium, Taenia saginata and Taenia asiatica). The 3 are flat, opaque white or yellowish, and exceptional long segmented parasites, measuring 1 to 12 m in their adult stage. In this review, the development of the knowledge regarding the first species, mainly focused on understanding how the larval stage or cysticercus is transmitted to humans, is described. The second species is a cosmopolitan parasite that only causes taeniosis and not cysticercosis; therefore, it will not be included. Information on the third species, which is presently being produced, since this species was recognized as such only at the end of the 20th century, will be discussed at the end of this review.