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.

Preliminary assessment of the computer-based Taenia solium educational program 'The Vicious Worm' on knowledge uptake in primary school students in rural areas in eastern Zambia.

OBJECTIVE: The zoonotic helminth Taenia solium is endemic in Zambia, causing human (taeniasis and (neuro)cysticercosis) and pig (porcine cysticercosis) diseases with high health, social and economic burdens. We aimed to evaluate the impact of a health educational program intended to lead to powerful and cumulative improvements in knowledge, attitudes and practices that decrease parasite transmission and disease occurrence. METHODS: Half-day health education workshops were conducted in three primary schools in the highly endemic Eastern Province of Zambia, using the computer-based T. solium educational program 'The Vicious Worm'. Questionnaires were administered before and after the educational component to determine the program's impact on knowledge uptake in primary school students. RESULTS: In total, 99 students participated: 38 males and 61 females, with a median age of 14 years (range 10-18 years). Baseline general knowledge of T. solium, including awareness of the different human and pig disease states, and disease diagnosis, treatment and prevention, was quite high (average score 62%) and consistent across all three study areas. Participants' knowledge had significantly increased after the educational component, particularly regarding parasite transmission and disease prevention. CONCLUSION: Preliminary assessment of 'The Vicious Worm' indicates it is an effective tool for the short-term T. solium education of primary school students in Zambia. Follow-up studies are planned to assess the longer term impact of the program on knowledge uptake in the study neighbourhoods. Inclusion of tailored 'The Vicious Worm' educational workshops should be considered in integrated cysticercosis control programs in endemic areas of sub-Saharan Africa.

Control trial of porcine cysticercosis in Uganda using a combination of the TSOL18 vaccination and oxfendazole.

BACKGROUND: Neurocysticercosis caused by Taenia solium when the parasite lodges in the central nervous system, is an important cause of human seizures and mortality in sub-Saharan Africa. The parasite is prevalent in many regions of Uganda. Pigs are intermediate hosts for T. solium, and we evaluated a T. solium control program in pigs, involving vaccination of pigs with the TSOL18 vaccine and treatment with oxfendazole. METHODS: The study was conducted in two districts of Eastern Uganda involving the rural village communities of Bukedea (intervention area) and Kumi (control area) during 2016-2017. Seven hundred and thirty-four households were enrolled in the study. Pigs in the intervention area received intramuscular immunizations with TSOL18 (Cysvax™) and an oral medication with 30 mg/kg oxfendazole (Paranthic™) at approximately 3-monthly intervals for 18 months. Porcine cysticercosis was evaluated by post-mortem examination. At the beginning of the study, 111 pigs were examined. In an interim evaluation in the intervention area, 55 pigs were evaluated 12 months after starting the project. At the end of the study approximately 3 months after the final intervention, 55 pigs from the intervention area and 56 pigs from the control area were evaluated. RESULTS: The prevalence of porcine cysticercosis for the two sites was 16.2% at the beginning of the study (17.2% in the intervention area and 15.1% in the control area) with no statistically significant difference (P = 0.759) between the two study sites. Among the 110 animals assessed from the intervention site (55 at the interim evaluation and 55 at the final evaluation), no pig with viable T. solium cysts was found. There was a statistically significant difference between the prevalence at baseline (17.2%) and at the end of the study (0%) in the intervention area (P = 0.001) and a statistically significant difference between the intervention (0%) and control areas (5.4%) (P = 0.041) at the end of the study. CONCLUSIONS: Three-monthly concurrent vaccination of pigs with the TSOL18 vaccine and medication with oxfendazole eliminated T. solium transmission by the animals involved in the study. Application of vaccination with medication in pigs has the potential to reduce transmission of T. solium in Uganda and other endemic countries.

Performance of Ag-ELISA in the diagnosis of Taenia solium cysticercosis in naturally infected pigs in Tanzania.

BACKGROUND: Taenia solium is a zoonotic parasite responsible for neurocysticercosis-a major cause of late-onset acquired epilepsy in humans. Lack of affordable, specific and sensitive diagnostic tools hampers control of the parasite. This study assessed the performance of an antigen detection enzyme-linked immunosorbent assay (Ag-ELISA) in the diagnosis of viable T. solium cysticercosis in naturally infected slaughter-age pigs in an endemic area in Tanzania. METHODS: A total of 350 pigs were bled before they were slaughtered and their carcases examined. Serum was analyzed for circulating antigens by using a monoclonal antibody-based B158/B60 Ag-ELISA. Each carcase was examined for the presence of Taenia hydatigena cysticerci and half carcase musculature together with the whole brain, head muscles, tongue, heart and diaphragm were sliced with fine cuts (< 0.5 cm) to reveal and enumerate T. solium cysticerci. Half carcase dissection can detect at least 84% of infected pigs. Prevalence and their 95% confidence intervals (CI) were calculated in Stata 12. Sensitivity, specificity, predictive values and likelihood ratios were determined. RESULTS: Twenty-nine pigs (8.3%, 95% CI: 5.6-11.7%) had viable T. solium cysticerci while 11 pigs had T. hydatigena cysticerci (3.1%, 95% CI: 1.6-5.5%). No co-infection was observed. Sixty-eight pigs (19.4%, 95% CI: 15.4-20%) tested positive on Ag-ELISA; of these, 24 had T. solium cysticerci and 7 had T. hydatigena cysticerci. Sensitivity and specificity were determined to be 82.7% and 86.3%, respectively. Positive and negative predictive values were 35.2% and 98.2%, respectively. Likelihood ratios for positive and negative Ag-ELISA test results were 6.0 and 0.2, respectively. There was a significant positive correlation between the titre of circulating antigens and intensity of T. solium cysticerci (r(348) = 0.63, P < 0.001). CONCLUSIONS: The Ag-ELISA test characteristics reported in this study indicate that the test is more reliable in ruling out T. solium cysticercosis in pigs, than in confirming it. Hence, a negative result will almost certainly indicate that a pig has no infection, but a positive result should always be interpreted with caution. Estimates of T. solium prevalence based on Ag-ELISA results should, therefore, be adjusted for test performance characteristics and occurrence of T. hydatigena.

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.

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.

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

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

Taenia solium from a community perspective: Preliminary costing data in the Katete and Sinda districts in Eastern Zambia.

The tapeworm Taenia solium is endemic in Zambia, however its socioeconomic cost is unknown. During a large-scale interventional study conducted in Zambia, baseline economic costs of human and porcine T. solium infections were measured. Questionnaire surveys were conducted within three neighbourhoods in Zambia's Eastern province in 2015 and 2016. A human health questionnaire, capturing costs of clinical symptoms commonly attributable to human cysticercosis and taeniasis, was conducted in randomly selected households (n = 267). All pig-keeping households were administered a pig socioeconomic questionnaire (n = 271) that captured pig demographic data, costs of pig-keeping, and economic losses from porcine cysticercosis. Of all respondents 62% had reportedly experienced at least one of the surveyed symptoms. Seizure-like episodes were reported by 12%, severe chronic headaches by 36%, and vision problems by 23% of respondents. These complaints resulted in 147 health care consultations and 17 hospitalizations in the five years preceding the study, and an estimated productivity loss of 608 working days per year. Of all pigs 69% were bought within villages. Nearly all adult pigs were sold to local traders, and tongue palpation for detection of cysticerci was commonly performed. Reportedly, 95% of pig owners could not sell tongue-positive pigs, while infected pigs fetched only 45% of the normal sale value. These preliminary costing data indicate that human and porcine T. solium infections substantially impact endemic areas of Eastern Zambia. A full socioeconomic burden assessment may enable improved T. solium management in sub-Saharan Africa.

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

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

Evaluation of two GnRH-I based vaccine formulations on the testes function of entire Suffolk cross ram lambs.

A modified GnRH peptide (CHWSYGLRPG-NH(2)) was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and formulated with Quil A saponin or a sustained release injectible PLGA (poly(lactide-co-glycolide)/triacetin). For the Quil A formulations, two administrations of TT conjugate at 3-weekly intervals were followed by two booster injections with the DT conjugate in entire ram lambs. With the PLGA formulations, only two injections were administered; the first containing TT and the second DT at 6-weekly intervals. Evaluation was carried out by comparing the specific antibody levels produced in relationship to hormone profiles and testicular changes. The Quil A formulation was considered the most effective, as it caused significant reduction in testosterone and follicle stimulating hormone levels, resulting in marked suppression of spermatogenesis.

Part II: influence of dimerization of a modified GnRH-I peptide sequence on a male antifertility vaccine.

PROBLEM: In the previous paper, we described how the tetanus toxoid (TT) conjugated monomer, CHWSYGLRPG-NH2, induced high neutralizing antibody titres, which resulted in decreased levels of testosterone and subsequent antifertility. However, its counterpart HWSYGLRPGC, induced low avidity antibody titres. We wanted to know whether peptide dimerization would improve the efficacy of both peptides. METHOD OF STUDY: Male Sprague-Dawley rats were immunized with modified dimerized GnRH-I peptides (HWSYGLRPGCCGPRLGYSWH and GPRLGYSWHCCHWSYGLRPG-NH2), with or without conjugation to TT. RESULTS: The unconjugated dimers were not effective in causing castration, although the first peptide dimer did induce production of antibodies. When conjugated to TT, both dimers showed the same level of efficacy in causing castration as each other. However, there were differences in antibody binding to native GnRH. CONCLUSIONS: Dimerization and conjugation to a carrier improved the antifertility efficacy of HWSYGLRPGC, whereas the conjugated monomer CHWSYGLRPG-NH2 showed a greater level of consistent castration than its conjugated dimer.

Influence of carrier protein conjugation site and terminal modification of a GnRH-I peptide sequence in the development of a highly specific anti-fertility vaccine. Part I.

PROBLEM: We previously immunoneutralized gonadotrophin releasing hormone (GnRH), using an analogue of GnRH (des-1 GnRH-I), conjugated to tetanus toxoid via a carbodiimide reaction. The castration effect on the reproductive system was not consistent in all the treated animals. Therefore, we examined the possibility that conjugation to the carrier protein via the N- or C-terminal could have an effect on efficacy. METHOD OF STUDY: GnRH analogue sequences were synthesized consisting of an additional cysteine at either terminal and specific conjugation was carried out using a bifunctional linker agent. RESULTS: Conjugation of the monomer through the N-terminal proved to be a highly effective means of causing immunocastration in terms of decreased gonadotrophin and testosterone concentrations and testicular size, whereas conjugation through the C-terminal proved to be ineffective. This was reflected in the ability of the antibodies to bind native GnRH, but not the levels of the anti-GnRH antibodies. CONCLUSION: Immunoneutralization efficacy was attributed to the importance of preserving the GnRH C-terminal.

Immune responses to a GnRH-based anti-fertility immunogen, induced by different adjuvants and subsequent effect on vaccine efficacy.

A modified GnRH peptide (CHWSYGLRPG-NH2) was conjugated to tetanus toxoid and formulated with different adjuvants (non-ionic surfactant vesicles, aluminium hydroxide, Quil A, PLGA (poly(lactide-co-glycolide)/triacetin), and Quil A/PLGA). A comparison of the anti-fertility efficacy of the formulations was made by examining specific antibody levels, antibody subclasses, endocrine ablation and gonadal atrophy. The production of IgG2b antibody provided the best correlation for castration. PLGA was considered the most effective adjuvant as it produced a consistent anti-fertility response in all the treated animals.