Efficacy of ivermectin and oxfendazole against Taenia solium cysticercosis and other parasitoses in naturally infected pigs

Understanding the pathogenic mechanisms and therapeutic effects in neurocysticercosis

Despite being a leading cause of acquired seizures in endemic regions, the pathological mechanisms of neurocysticercosis are still poorly understood. This study aims to investigate the impact of anthelmintic treatment on neuropathological features in a rat model of neurocysticercosis. Rats were intracranially infected with Taenia solium oncospheres and treated with albendazole + praziquantel (ABZ), oxfendazole + praziquantel (OXF), or untreated placebo (UT) for 7 days. Following the last dose of treatment, brain tissues were evaluated at 24 h and 2 months. We performed neuropathological assessment for cyst damage, perilesional brain inflammation, presence of axonal spheroids, and spongy changes. Both treatments showed comparable efficacy in cyst damage and inflammation. The presence of spongy change correlated with spheroids counts and were not affected by anthelmintic treatment. Compared to white matter, gray matter showed greater spongy change (91.7% vs. 21.4%, p < 0.0001), higher spheroids count (45.2 vs. 0.2, p = 0.0001), and increased inflammation (72.0% vs. 21.4%, p = 0.003). In this rat model, anthelmintic treatment destroyed brain parasitic cysts at the cost of local inflammation similar to what is described in human neurocysticercosis. Axonal spheroids and spongy changes as markers of damage were topographically correlated, and not affected by anthelmintic treatment.

Knowledge, attitudes and practices regarding porcine cysticercosis control among smallholder pig farmers in Kongwa and Songwe districts, Tanzania: A cross-sectional study

Taenia solium taeniasis/cysticercosis (TSTC) is a parasitic zoonotic disease that is endemic in several developing countries, causing serious public health and economic impacts. A cross-sectional study was conducted to assess knowledge, attitudes and practices (KAP) related to porcine cysticercosis (PCC) transmission, prevention and control among smallholder pig farmers in Kongwa and Songwe Districts in Tanzania. A semi-structured questionnaire was administered to 692 smallholder pig farmers from randomly selected households. STATA software version 17 was used to analyse quantitative data, summarize farmers' KAP about PCC and calculate performance scores. Nearly half (42%) of the respondents had little knowledge regarding PCC, only 17% of the respondents had good practices towards prevention/control of PCC and 72% had a positive attitude towards PCC- prevention/control measures. The majority (73%) of smallholder pig farmers admitted deworming their pigs regularly, whereas 76% reported deworming themselves and their family members regularly. Albendazole and ivermectin are the most commonly used medications for deworming people and pigs, respectively. According to the findings, the majority of smallholder pig farmers in Kongwa and Songwe Districts showed a good attitude towards PCC prevention/control measures but had limited knowledge of the PCC life cycle and control. In addition, only one in five farmers was engaged in good practices. The findings revealed further that farmers are engaged in risky behaviours that aid the spread and perpetuation of the T. solium parasite in the study area. It is recommended that farmers should be given proper health education on the T. solium transmission cycle and preventive/control practices to limit PCC transmission.

Co-infection of pigs with Taenia solium cysticercosis and gastrointestinal parasites in Eastern and Western Uganda

A study was carried out in Kamuli and Hoima districts in Eastern and Western regions of Uganda to determine the Taenia solium porcine cysticercosis (PCC) and gastrointestinal (GI) parasites co-infection status in pigs. One hundred sixty-one households were selected randomly and visited between November and December 2019. A household questionnaire was administered, and faecal and blood samples were collected from at least one pig older than 3 months per household. A blood sample was obtained from a jugular venipuncture, and a rectal faecal sample was obtained. Taenia spp. circulating antigen levels in the sample sera were tested using a commercial enzyme-linked immunosorbent assay kit, apDia™ cysticercosis Ag ELISA. The modified McMaster technique was used to identify and quantify the GI parasites. The apparent animal-level seroprevalence for PCC was 4.8% (95% CI 2.7–7.1) and differed across the two districts (p = 0.018). At the pig herd level, the prevalence was 9.7% (95% CI 5.5–14.4). The prevalence of the different nematode eggs and coccidian oocysts in the two districts was as follows: strongyles 79.0% (95% CI 74.3–83.6), coccidia 73.3% (95% CI 68.3–78.6), Trichuris spp. 7.4% (95% CI 4.9–10.6), Strongyloides ransomi 2.1 (95% CI 0.7–3.5) and Ascaris spp. 4.9 (95% CI 2.8–7.4). Overall, across the two districts, the arithmetic mean for the oocysts per gram (OPG) for coccidia was 2042.2 ± 5776.1, and eggs per gram (EPG) were the highest in strongyles 616.1 ± 991. Overall, 57.4% of the porcine cysticercosis seropositive pigs were also positive for at least one of the gastrointestinal helminths which included strongyles, Strongyloides ransomi, Trichuris spp. and Ascaris spp. The co-infection status of pigs with both PCC and GI parasites demonstrated by this study can provide an incentive for integrating the control and management of both parasites with oxfendazole. Further studies are required to understand the feasibility of using oxfendazole including cost–benefit analysis and the acceptability by local stakeholders for the control of T. solium cysticercosis and gastrointestinal parasites in pigs.

Validating efficacy of Sericocomopsis hildebrandtii, Carissa edulis, and Ximenia americana in treating Taenia solium cysticercosis in pigs: A randomized controlled trial

Ethnoveterinary use of plants dates back to ancient times. This study aimed to validate purported efficacy of Sericocomopsis hildebrandtii and a concoction of Carissa edulis and Ximenia americana in treating Taenia solium cysticercosis in pigs. Twenty-four infected pigs were randomly allocated to T1, T2, and T0 groups, each with eight pigs. Each T1 pig was provided with 8 g of S. hildebrandtii root powder, whereas each T2 pig was given 8 g of the concoction. T0 was a control. The pigs were slaughtered 16 weeks post treatment and carcase dissections were performed to establish cyst numbers. T1 cyst numbers were significantly lower than those of T0 (p = .004) and T2 (p = .013). No difference was observed between T2 and T0. This study validated efficacy of S. hildebrandtii but not of X. americana and C. edulis. Further studies are necessary for validation and documentation of plants of ethnoveterinary importance.

Evidence for Transmission of Taenia solium Taeniasis/Cysticercosis in a Rural Area of Northern Rwanda

Cysticercosis is a parasitic infection caused by the metacestode larval stage (cysticercus) of Taenia solium. In humans, cysticercosis may infect the central nervous system and cause neurocysticercosis, which is responsible for over 50,000 deaths per year worldwide and is the major cause of preventable epilepsy cases, especially in low-income countries. Cysticercosis infection is endemic in many less developed countries where poor hygiene conditions and free-range pig management favor their transmission. A cross-sectional study was conducted in 680 children from a rural primary school in Gakenke district (Northern province of Rwanda). Stool samples were collected from participants and analyzed using the Kato-Katz method (KK), formol-ether concentration (FEC), and/or copro-antigen enzyme-linked immunosorbent assay (CoAg-ELISA) to detect taeniasis. Blood samples were collected and analyzed using enzyme-linked immunoelectrotransfer blot (EITB) and antigen enzyme-linked immunosorbent assay (Ag-ELISA) to detect human cysticercosis. The overall proportion of taeniasis positivity was 0.3% (2/680), and both cases were also confirmed by CoAg-ELISA. A total of 13.3% (76/572) of the children studied were positive to cysticercosis (T. solium-specific serum antibodies detected by EITB), of whom 38.0% (27/71) had viable cysticercus (T. solium antigens by Ag-ELISA). This study provides evidence of the highest cysticercosis prevalence reported in Rwanda in children to date. Systematic investigations into porcine and human cysticercosis as well as health education and hygiene measures for T. solium control are needed in Gakenke district.

Population Pharmacokinetic Model of Oxfendazole and Metabolites in Healthy Adults following Single Ascending Doses

Oxfendazole is a potent veterinary benzimidazole anthelmintic under transition to humans for the treatment of multiple parasitic infectious diseases. The first-in-human study evaluating the disposition of oxfendazole and its metabolites in healthy adults following single ascending oral doses from 0.5 to 60 mg/kg of body weight shows that oxfendazole pharmacokinetics is substantially nonlinear, which complicates correlating oxfendazole dose to exposure. To quantitatively capture the relation between oxfendazole dose and exposure, a population pharmacokinetic model for oxfendazole and its metabolites, oxfendazole sulfone and fenbendazole, in humans was developed using a nonlinear mixed-effect modeling approach. Our final model incorporated mechanistic characterization of dose-limited bioavailability as well as different oxfendazole metabolic processes and provided insight into the significance of presystemic metabolism in oxfendazole and metabolite disposition. Oxfendazole clinical pharmacokinetics was best described by a one-compartment model with nonlinear absorption and linear elimination. Oxfendazole apparent clearance and apparent volume of distribution were estimated to be 2.57 liters/h and 35.2 liters, respectively, at the lowest dose (0.5 mg/kg), indicating that oxfendazole is a low extraction drug with moderate distribution. The disposition of both metabolites was adequately characterized by a one-compartment model with formation rate-limited elimination. Fenbendazole formation from oxfendazole was primarily through systemic metabolism, while both presystemic and systemic metabolism were critical to the formation of oxfendazole sulfone. Our model adequately captured the concentration-time profiles of both oxfendazole and its two metabolites in healthy adults over a wide dose range. The model can be used to predict oxfendazole disposition under new dosing regimens to support dose optimization in humans.

Prevalence and risk assessment of porcine cysticercosis in Ngozi province, Burundi

Cysticercosis is a major zoonotic disease in many developing countries leading to substantial economic and public health impacts on affected communities. Due to a lack of updated data on T. solium cysticercosis in Burundi, the present study was carried out to determine the prevalence of porcine cysticercosis and to identify potential associated risk factors in Ngozi province. This study was conducted in Ngozi and Marangara communes of Ngozi province during January and February 2020. A multistage random sampling strategy was used. Tongue palpation was performed on pigs to diagnose cysticercosis. Randomly selected heads of pig keeping households were interviewed to assess the risk factors for porcine cysticercosis. A logistic regression model was used to analyse the main risk factors associated with porcine cysticercosis. In total, 496 pigs from 321 households distributed in 16 hills, randomly selected in Ngozi and Marangara communes were inspected. The apparent prevalence by tongue palpation in Ngozi province was 15.5% (95% CI: 12.3-18.7%). In Ngozi and in Marangara communes, the prevalence was 22.9% (95% CI: 17.7-28.2%) and 8.1% (95% CI: 4.6-11.4%), respectively. The true prevalence was estimated at 31% for the province, with a prevalence of 45.8% in Ngozi and 16.2% in Marangara commune, respectively. Pig farming systems including free ranging, tethering and penned part of the day (OR = 3.5; 95% CI: 2.1-6.1; p ≤  0.001) and lack of meat inspection at home slaughter (OR = 2.5; 95% CI: 1.1-5.6; p = 0.019) were significant risk factors associated with porcine cysticercosis. The present findings show that porcine cysticercosis is highly endemic in Ngozi province and that pig management systems currently used in the area permit pigs to have access to human stool. Moreover, lack of meat inspection during home slaughter potentially gives the possibility for household and community members to eat infected pork. Total confinement of pigs, improved hygiene and sanitation in households, and improvement of meat inspection through awareness campaigns and overall health education of the community should be implemented to control T. solium infections.

Pharmacokinetics, Safety, and Tolerability of Oxfendazole in Healthy Adults in an Open-Label Phase 1 Multiple Ascending Dose and Food Effect Study

Neurocysticercosis and trichuriasis are difficult-to-treat parasitic infections that affect more than 1.5 billion people worldwide. Oxfendazole, a potent broad-spectrum benzimidazole anthelmintic approved for use in veterinary medicine, has shown substantial antiparasitic activity against neurocysticercosis and intestinal helminths in preclinical studies. As part of a program to transition oxfendazole from veterinary medicine to human use, phase I multiple ascending dose and food effect studies were conducted. Thirty-six healthy adults were enrolled in an open-label study which evaluated (i) the pharmacokinetics and safety of oxfendazole following multiple ascending doses of oxfendazole oral suspension at 3, 7.5, and 15 mg/kg once daily for 5 days and (ii) the effect of food on oxfendazole pharmacokinetics and safety after a single 3-mg/kg dose administered following an overnight fast or the consumption of a fatty breakfast. Following multiple oral dose administration, the intestinal absorption of oxfendazole was rapid, with the time to maximum concentration of drug in serum (Tmax) ranging from 1.92 to 2.56 h. A similar half-life of oxfendazole (9.21 to 11.8 h) was observed across all dose groups evaluated, and oxfendazole exhibited significantly less than a dose-proportional increase in exposure. Oxfendazole plasma exposures were higher in female subjects than in male subjects. Following daily administration, oxfendazole reached a steady state in plasma on study day 3, with minimal accumulation. Food delayed the oxfendazole Tmax by a median of 6.88 h and resulted in a 49.2% increase in the maximum observed drug concentration in plasma (Cmax) and an 86.4% increase in the area under the concentration-time curve (AUC). Oxfendazole was well tolerated in all study groups, and there were no major safety signals identified in this study. (This study has been registered at ClinicalTrials.gov under identifier NCT03035760.).

Endemicity of Taenia solium cysticercosis in pigs from Mbeya Rural and Mbozi districts, Tanzania

BACKGROUND

Taenia solium taeniasis/cysticercosis is a disease of substantial economic and public health importance particularly in low-income countries. The disease was reported to be endemic in Mbeya Rural and Mbozi districts, in the southern highlands of Tanzania, the major pig production area in the country. In 2008, using B158/B60 antigen detection enzyme-linked immunosorbent assay (Ag-ELISA), porcine cysticercosis prevalence of up to 32% was reported in the districts. A number of interventions have been implemented in selected villages including an integrated approach consisting of improving pig confinement and selective treatment of pigs with oxfendazole. Mass drug administration with praziquantel targeting schistosomiasis, with an expected effect on T. solium, was also provided to school-age children in the area. This study aimed at providing an update on prevalence and intensities of porcine cysticercosis; and assessing farmers' knowledge, attitudes and practices which could be associated to disease transmission in the area. The study involved a questionnaire survey conducted using face-to-face household interviews with 890 consenting farmers; and carcass dissections performed on 282 pigs randomly selected from the surveyed households.

RESULTS

Twenty-six pigs (9.2%) were infected with T. solium; of which two-thirds (65.4%) had light to moderate infection intensities (1-1000 cysticerci), and one-third (34.6%) had heavy intensities (> 1000 cysticerci). Questionnaire results showed that only 5.7% of the respondents perceived T. solium cysticercosis to be an important disease in pigs. About 18.5% of the respondents were aware of T. solium taeniasis, but 32% of them were unaware of how the infection is acquired. Half of the respondents had seen cysticerci in pork, of whom 61% were not aware that consumption of infected pork could cause taeniasis. Latrines were observed to often (90%) lack doors with 45% considered accessible to pigs.

CONCLUSIONS

This study provided an evidence that the disease was still endemic in the area. Poor knowledge of farmers, attitudes, and risky practices responsible for disease perpetuation were also revealed. A One Health approach targeting the whole area incorporating improvement of farmer knowledge regarding disease transmission needs to be trialed as a feasible approach to control.

Taenia solium taeniosis and cysticercosis literature in Tanzania provides research evidence justification for control: A systematic scoping review

Background

Despite Taenia solium taeniosis/cysticercosis (TSTC) having been put high on the global agenda of neglected tropical diseases (NTDs), which over the last years has received a lot of attention, there has been no control programmes in place in sub-Saharan Africa, a highly endemic region. This could be attributed to lack of awareness of many stakeholders on the burden and impact of T. solium. This information is essential in guiding TSTC policies, practices and research agendas as well as encouraging cross-sectoral collaboration in the control of this important zoonotic parasite using a One Health approach. National elimination of the parasite is the foundation for global eradication. This will require that substantial country-level information is provided to all key stakeholders. We have mapped out TSTC research evidence in Tanzania to inform on disease burden and potential for integrated control measures.

Methodology/Principal findings

A scoping review of all TSTC studies undertaken in Tanzania and published up to December 2018 was conducted. The articles were searched from PUBMED, AJOL, Google Scholar and Google in general. Fifty-one (51) articles met the inclusion criteria and were reviewed. Prevalence of taeniosis of 2.3% - 5.2% was estimated based on copro-antigen ELISA while human cysticercosis of >16% was estimated based on serum antigen ELISA (Ag-ELISA) or IgG Western Blot. Neurocysticercosis (NCC) contributed significantly to epilepsy in adults. Farm prevalence of porcine cysticercosis were 6.0% - 17.4% (lingual examination) and 1.5% - 33.3% (Ag-ELISA). Slaughter-slab prevalence were 0% - 18.2% (routine meat inspection). Lacking latrines, watering pigs with river or pond water, and feeding pigs with potato peels were associated with porcine cysticercosis prevalence. Washing hands by dipping method increased the risk of human cysticercosis. In 2012, the number of DALYs/1000 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. Three rounds of annual treatment of school-age children with praziquantel significantly reduced prevalence of taeniosis and porcine cysticercosis. Health education was efficacious in improving knowledge and attitudes favourable for control of TSTC while a single dose of oxfendazole 30 mg/kg body weight was efficacious in eliminating T. solium cysticerci from pig musculature.

Conclusions/Significance

The observed high burden of TSTC and the significant contribution of NCC to epilepsy in Tanzania warrant urgent interventions. Evaluation of best control options should make use of disease transmission dynamics models such as cystiSim, taking into account findings from the field based intervention studies. In addition, locally adapted management guidelines for people suffering from NCC are urgently needed.

Oral nitazoxanide treatment of experimental neurocysticercosis induces gluconeogenesis in Taenia crassiceps cysticerci

Neurocysticercosis is the most frequent helminthiasis of the central nervous system and is caused by the presence of Taenia solium cysticerci. Nitazoxanide (NTZ) is an antifolate containing the pyrrolopyrimidine-based nucleus that exerts its antiprotozoal activity due to interference with the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme which is essential to anaerobic energy metabolism. The aim of this work was to determine the effect of NTZ on the energetic metabolism of Taenia crassiceps cysticerci intracranially inoculated BALB /c mice. The infected animals were treated with a single oral dose of NTZ 30 days after the inoculation. Analysis of the organic acids was performed through high performance liquid chromatography. Glucose was detected only in the treated groups, alongside with a significant decrease in lactate, pyruvate and oxaloacetate concentrations which indicate an increase in gluconeogenesis. The non-detection of alpha-ketoglutarate indicated the use of the fumarate reductase pathway in all groups. It was possible to confirm the drugs mode of action due to the non-detection of acetate in the treated groups. There was an increase in the fatty acids oxidation. Therefore it was possible to observe that NTZ induces gluconeogenesis as well as the increase of alternative energetic pathways such as fatty acids oxidation in T. crassiceps cysticerci.

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.

Oxfendazole: a promising agent for the treatment and control of helminth infections in humans

INTRODUCTION

Oxfendazole (methyl [5-(phenylsulphinyl)-1H benzimidazole-2-yl] carbamate) has a particularly long metabolic half-life in ruminants, and its metabolite fenbendazole also has anthelminthic action. A very limited number of drugs are available for the treatment of some zoonotic helminth infections, such as neurocysticercosis and echinococcosis. More recent work has expanded oxfendazole's nonclinical safety profile and demonstrated its safety and bioavailability in healthy human volunteers, thus advancing the possibility of a new and greatly needed option for antiparasitic treatment of geohelminths and tissue parasites. Areas covered: The present article reviews evidence supporting the safety and efficacy of oxfendazole against both gut and tissue dwelling helminths in animals, as well as more recent safety and pharmacokinetic data supporting its potential for use in human parasitoses. Expert commentary: The pharmacokinetics, safety, and wide spectrum of efficacy of oxfendazole are consistently demonstrated in intestinal helminth infections of animals as well as in tissue dwelling larval cestode and trematode infections in diverse animal species. Now supported by first-in-human safety and pharmacokinetic data, oxfendazole becomes a promising alternative to the limited portfolio of antiparasitic drugs available to treat helminthic diseases of humans.

Use of Ivermectin in Neurocysticercosis: A Case Report

Patient: Female, 25

Final Diagnosis: Neurocysticercosis

Symptoms: Headache • seizure

Medication: —

Clinical Procedure: Lumber puncture

Specialty: Infectious Diseases

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.

Effectiveness of an integrated intervention in the control of endo- and ectoparasites of pigs kept by smallholder farmers in Mbeya rural and Mbozi districts, Tanzania

This study was conducted to evaluate effectiveness of an integrated management intervention in the control of endo- and ectoparasites of pigs kept by smallholder farmers in Mbeya Rural and Mbozi districts of southern highlands of Tanzania. A repeated cross-sectional group randomization design was employed, with 10 villages in the intervention group and six villages in the control group. The intervention consisted of improving pig confinement, feeds and feeding practices, and strategic anthelmintic treatment of pigs with oxfendazole, to primarily control Taenia solium (porcine) cysticercosis and nematodes; and with ivermectin to control ectoparasites and nematodes. Blood and faecal samples, ectoparasite specimens and skin scrapings were collected at baseline and two follow-up rounds, at an interval of seven months. A total of 482, 460 and 421 pigs were sampled in 221, 196 and 139 households at baseline, first and second follow-up visits respectively. Sero-prevalence of PC, prevalence and burden of gastrointestinal (GI) nematodes and prevalence of ectoparasites were determined using Ag-ELISA, McMaster faecal egg counting technique and body searches/skin scrapings, respectively. Mann Whitney test was used to measure intervention effect by comparing changes from baseline values of prevalence and faecal egg counts between the two groups. No significant difference (p > 0.05) was observed between the two groups, in changes from baseline of sero-prevalence of PC. The intervention significantly reduced prevalence of Trichuris suis (p = 0.044) and mean faecal egg counts of Ascaris suum (p = 0.02) from baseline to first follow-up. The intervention showed a substantial effect on the prevalence of ectoparasites as it significantly reduced overall prevalence of ectoparasites (p = 0.026), lice (p = 0.045), ticks (p = 0.049) and mites (p = 0.013) from baseline to first follow-up, and prevalence of ectoparasites, lice and mites from baseline to second follow-up (p = 0.052, p = 0.03, p = 0.017 respectively). This study has demonstrated a moderate effect of the intervention on controlling GI nematodes and ectoparasites, but no effect on sero-prevalence of PC. The reported ineffectiveness of the intervention against PC is probably an underestimation because serology is not able to provide quantitative data. It may also be a result of reduced compliance as this was a field study. Nevertheless, further studies are needed to better understand transmission dynamics of PC and explore One Health approaches including treatment of the human population against taeniosis to better secure public health.

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.

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.

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.

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.

Severe seizures in pigs naturally infected with Taenia solium in Tanzania

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Pigs with neurocysticercosis can develop clinical signs and suffer from seizures.

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Autonomic signs were chewing motions with foamy salivation and ear stiffening.

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Motor signs included tonic muscle contractions and tremor.

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Stereotypic walking in circles was observed on several occasions.

Neurocysticercosis (NCC) caused by Taenia solium is a serious neurological disease. In humans neurological symptoms have been thoroughly studied and documented, however, there is limited information on clinical signs in pigs infected with T. solium cysticerci. Among the scientific community, it is in fact believed that pigs with NCC rarely show neurological signs. The aim of this study was to describe clinical manifestations associated with NCC in pigs and correlate the manifestations to the number and distribution of cysticerci in brains of naturally infected pigs in Tanzania. Sixteen infected and 15 non-infected control pigs were observed for 14 days during daylight hours, and subsequently videotaped for another 14 consecutive days using close circuit television cameras. All occurrences of abnormal behaviour (trembling, twitching, mouth and ear paralysis, ataxia, dribbling, salivating, eye blinking, walking in circles) were recorded. At the end of the recording period, pigs were slaughtered and their brains dissected, cysticerci counted and locations noted. During the recording period, two infected pigs were observed having seizures. Some of the observed autonomic signs during a seizure were chewing motions with foamy salivation and ear stiffening. Motor signs included tonic muscle contractions followed by a sudden diminution in all muscle function leading to collapse of the animal. Stereotypic walking in circles was observed on several occasions. At dissection, both pigs had a high number of brain cysticerci (241 and 247 cysticerci). The two pigs with seizures were also older (36 months) compared to the others (18.3 months, ± 8.2 standard deviation). Results of this study have shown that pigs with NCC can develop clinical signs and suffer from seizures like humans with symptomatic NCC. Results of this study could potentially open up a new experimental pathway to explore the aetiology of neurological symptoms in humans with NCC associated epilepsy.

Successful Antiparasitic Treatment for Cysticercosis is Associated with a Fast and Marked Reduction of Circulating Antigen Levels in a Naturally Infected Pig Model

Taenia solium cysticercosis is a common parasitic infection of humans and pigs. We evaluated the posttreatment evolution of circulating parasite-specific antigen titers in 693 consecutive blood samples from 50 naturally infected cysticercotic pigs, which received different regimes of antiparasitic drugs (N = 39, 7 groups), prednisone (N = 5), or controls (N = 6). Samples were collected from baseline to week 10 after treatment, when pigs were euthanized and carefully dissected at necropsy. Antigen levels decreased proportionally to the efficacy of treatment and correlated with the remaining viable cysts at necropsy (Pearson's p = 0.67, P = 0.000). A decrease of 5 times in antigen levels (logarithmic scale) compared with baseline was found in 20/26 pigs free of cysts at necropsy, compared with 1/24 of those who had persisting viable cysts (odds ratio [OR] = 76.7, 95% confidence interval [CI] = 8.1-3308.6, P < 0.001). Antigen monitoring reflects the course of infection in the pig. If a similar correlation exists in infected humans, this assay may provide a minimally invasive and easy monitoring assay to assess disease evolution and efficacy of antiparasitic treatment in human neurocysticercosis.

Risk factors for prevalence of pig parasitoses in Mbeya Region, Tanzania

A cross-sectional study was carried out to determine risk factors for prevalence of common endo- and ectoparasites of pigs kept by smallholder farmers in Mbozi and Mbeya (Rural) districts of Mbeya Region, in Tanzania. A total of 482 pigs from 220 households of 16 villages, eight in each district were randomly selected and examined. Prevalence of Taenia solium cysticercosis was 11.5%, gastrointestinal nematodes 63.7% and ectoparasites 21.2% based on Ag-ELISA, McMaster technique and full body searches/ear scrapings, respectively. Nematode eggs identified were strongyles (Oesophagostomum spp. and Trichostrongylus spp.), Ascaris suum, Trichuris suis and Strongyloides ransomi with prevalence of 57.4%, 17.5%, 5.3% and 1.1%, respectively. Four groups of ectoparasites were identified, i.e. lice (Haematopinus suis), ticks (Rhipicephalus spp., Amblyomma spp., Haemaphysalis spp. and Boophilus spp.), fleas (Ctenocephalides canis) and mites (Sarcoptes scabiei var. suis and Demodex phylloides), with prevalence of 19.1%, 2.1%, 0.4%, and 1.2%, respectively. Pigs in Mbeya (Rural) District had higher odds for porcine cysticercosis (OR=2.63, 95% CI: [1.22-5.55]). Poor pen hygiene and infrequent antiparasitic treatment were identified to be risk factors for prevalence of nematode infections (OR=1.95 [1.09-3.52] and OR=1.78 [1.06-2.94], respectively). The odds for high nematode burdens increased in cases of poor pen hygiene (OR=4.20 [2.54-6.62]) and poor feed quality (OR=3.7 [1.66-8.33]). Pigs not treated with antiparasitic drugs within the last three months had higher odds for ectoparasite (OR=4.0 [1.78-9.09]) and lice infestations (OR=8.33 [1.96-14.28]) than treated pigs. This study has shown that parasitoses constitute a major burden for smallholder pigs in Mbeya Region and major risk factors included infrequent antiparasitic treatment, poor pen hygiene and poor feed quality. Cost-effective intervention strategies are needed to improve pork production, secure pig welfare and ensure safe pork for human consumption.

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

Background

This study aimed to map the distribution of Taenia solium taeniosis/cysticercosis and the co-distribution with schistosomiasis in Africa. These two major neglected tropical diseases are presumed to be widely distributed in Africa, but currently the level of co-distribution is unclear.

Methods

A literature search on T. solium taeniosis/cysticercosis was performed to compile all known studies on the presence of T. solium and apparent prevalence of taeniosis and porcine cysticercosis in Africa. Studies were geo-referenced using an online gazetteer. A Bayesian framework was used to combine the epidemiological data on the apparent prevalence with external information on test characteristics to estimate informed district-level prevalence of taeniosis and porcine cysticercosis. Districts with T. solium taeniosis/cysticercosis presence were cross-referenced with the Global Neglected Tropical Diseases Database for schistosomiasis presence.

Results

The search strategies identified 141 reports of T. solium in Africa from 1985 to 2014 from a total of 476 districts in 29 countries, 20 with porcine cysticercosis, 22 with human cysticercosis, and 16 with taeniosis, in addition to 2 countries identified from OIE reports. All 31 countries were considered, on national scale, to have co-distribution with schistosomiasis. Presence of both parasites was confirmed in 124 districts in 17 countries. The informed prevalence of taeniosis and porcine cysticercosis were estimated for 14 and 41 districts in 10 and 13 countries, respectively.

Conclusions

With the paucity of data, T. solium infection is grossly under-reported and expected to be more widespread than this study suggests. In areas where co-distribution occurs there is a need for increased emphasis on evaluation of integrated intervention approaches for these two helminth infections and allocation of resources for evaluating the extent of adverse effects caused by mass drug administration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0938-7) contains supplementary material, which is available to authorized users.

Control of cysticercosis in Madagascar: beware of the pitfalls

Taenia solium cysticercosis is a zoonosis of public health importance in areas where the disease is endemic, with significant economic impacts on human health and the swine industry. Several gaps remain in the epidemiology of the parasite and the strategies of control in developing countries. We detail the key factors to consider in Madagascar in terms of the porcine husbandry system, Taenia transmission cycle, and diagnosis of cysticercosis in pigs, in order to better estimate the sanitary and economic impacts of this parasitic disease as well as to define an integrated control program.