Comparative evaluation of an indirect ELISA test for diagnosis of swine cysticercosis employing antigen from Taenia solium and Taenia crassiceps metacestodes

What about the Cytoskeletal and Related Proteins of Tapeworms in the Host's Immune Response? An Integrative Overview

Recent advances have increased our understanding of the molecular machinery in the cytoskeleton of mammalian cells, in contrast to the case of tapeworm parasites, where cytoskeleton remains poorly characterized. The pertinence of a better knowledge of the tapeworm cytoskeleton is linked to the medical importance of these parasitic diseases in humans and animal stock. Moreover, its study could offer new possibilities for the development of more effective anti-parasitic drugs, as well as better strategies for their surveillance, prevention, and control. In the present review, we compile the results of recent experiments on the cytoskeleton of these parasites and analyze how these novel findings might trigger the development of new drugs or the redesign of those currently used in addition to supporting their use as biomarkers in cutting-edge diagnostic tests.

Swine cysticercosis and associated risk factors in non-technified pig breeding in semi-arid region of Sergipe state, Brazil

The aim of this study was to determine the frequency of Taenia solium anti-metacestode antibodies in slaughtered pigs in a semi-arid region of the "Alto Sertão" of Sergipe state, Brazil, and verify the risk factors associated with swine cysticercosis. For this, 230 samples of swine blood from two slaughterhouses were collected and analyzed by indirect ELISA. The pigs came from five non-technical properties in the semi-arid region of the Alto Sertão of Sergipe state. Searches for cysts in the skeletal muscles of the pigs were performed during slaughter. In addition, an epidemiological questionnaire was applied to the pigs' original properties to determine risk factors. Besides that, the official health services database was evaluated for confirmed cases of neurocysticercosis and taeniasis in humans in the last 5 years, living in the studied region. Seropositivity in pigs was 12.6%, with no significant difference between males and females. No cysts were found in the carcasses of the slaughtered pigs. A positive association was found for properties that discharge domestic sewage into the environment, in river or streams, increasing the risk of positivity by 5.72 times. When analyzing the database of official agencies, there were no records of cases of neurocysticercosis or taeniasis in the resident population in the last 5 years. However, there were frequent cases of idiopathic epilepsy. The results demonstrate that study area is endemic for swine cysticercosis and serves as a warning of the possibility of the occurrence of the taeniasis-cysticercosis complex.

Further evaluation of recombinant Tsol-p27 by enzyme-linked immunoelectrotransfer blot for the serodiagnosis of cysticercosis in pigs from Mozambique

BACKGROUND

Porcine cysticercosis has a negative impact on human health and the meat industry, as it makes infected meat unaproprieted for consuption and it is the main etiology of epileptic seizures in developing countries. There are multiple serological assays that use crude antigens with high sensitivity and specificity for the diagnosis of both porcine and human cysticercosis. Nonetheless, antigen preparation is time-consuming, needs a well-equipped laboratory and trained personnel and places those manipulating the meat at great risk for infection. New serodiagnostic approaches to the diagnosis of porcine and human cysticercosis have been directed towards the development of recombinant deoxyribonucleic acid technology for the generation of synthetic proteins that can serve as simplified, low-cost and harmless substitutes for native antigens. The aim of the present study was to further evaluate the recombinant Tsol-p27 protein as a target molecule in immunoassays for the serodiagnosis of porcine cysticercosis. From these data, we hoped to develop recommendations regarding its use in the serodiagnosis of porcine cysticercosis.

RESULTS

We studied a panel of 83 naturally infected pig sera from Angónia District, Mozambique, an endemic area for porcine and human cysticercosis. These sera were previously tested by antigen enzyme-linked immunosorbent assay (Ag-ELISA) to detect antigens of T. solium. The serum panel was processed by enzyme-linked immunoelectrotransfer blot (EITB) assay against the recombinant Tsol-p27 protein and the Ag-ELISA assay results were used to compare and evaluate the performance of Tsol-p27 for the diagnosis of cysticercosis. Out of 83 sera, 24 (29.0%) were positive for Tsol-p27 and 59 (71%) were negative in the same assay. From the 37 sera that tested positive to Ag-ELISA, 11 (13.3%) were positive to Tsol-p27, while from 46 sera that tested negative to Ag-ELISA, 33 (39.7%) also tested negative to Tsol-p27. The sensitivity and specificity of Tsol-p27 was 29.7% and 71.7%, respectively, while the positive predictive value and negative predictive value were 45.8% and 55.9%, respectively, as calculated using Medcalc® version 15.0 software (MedCalc Software, Ostend, Belgium).

CONCLUSION

While Tsol-p27 recombinant protein might be suitable for testing human sera, its performance in pigs is not acceptable, so other recombinant proteins should be evaluated alone or multiplexed.

Serological responses in porcine cysticercosis: a link with the parasitological outcome of infection

An oral infection model with Taenia solium whole proglottids was used to study host-parasite relationships and the mechanisms underlying resistance to infection in pigs. In addition, an attempt was made to link the parasitological findings to serological data. Groups of six piglets aged 1, 3 and 5 months were infected and slaughtered 3 months p.i. Circulating antibody and antigen levels were monitored weekly. At autopsy total cyst counts were performed. Although the detailed carcass dissection at necropsy revealed a high variation in the number of cysts, the trend was that the number of viable cysts decreased with the age at which the animals were infected. The kinetics of the antigen levels throughout the course of the infection differed markedly between the three age groups of the experimental infection model. In the younger animals, a fast increase in titres of circulating antigen was observed in most animals, reaching a plateau as early as 2 weeks p.i. Besides its faster increase, antigen levels in pigs infected at younger ages also reached higher levels than in older animals and were associated with weaker antibody responses. Results also demonstrated that a relationship exists between the number of cysts and the titre of circulating antigen. This is promising in view of the development of an assay to quantify the progress of an active T. solium infection and would be a useful tool in epidemiological studies to assess the infection burden and the risk of transmission of the disease. The use of specific antibody-detection assays combined with circulating antigen detection could improve our understanding of this relationship.

A Bayesian approach for estimating values for prevalence and diagnostic test characteristics of porcine cysticercosis

Several diagnostic techniques are used to estimate the prevalence of the zoonotic tapeworm Taenia solium in pigs, but none of these tests are perfect, making interpretation of results difficult. A Bayesian approach was used to estimate values for the prevalence and diagnostic test characteristic of porcine cysticercosis by combining results of four imperfect tests. Village pigs (N = 868) slaughtered in Lusaka (Zambia), were bled, and tongue and routine meat inspected; and serum antibody and parasite antigen concentrations were determined by ELISA. A model, based on a multinomial distribution and including all possible interactions between the individual tests required 31 parameters to be estimated, but actually allowed only 15 parameters (i.e. had 15 degrees of freedom) to be estimated. Therefore, prior expert opinion on specificity and (in)-dependence of the tests was entered in the model, resulting in a reduction of the number of parameters to be estimated. The estimated prevalence of porcine cysticercosis was 0.642 (95% confidence interval 0.54-0.91). The performances of the tests were (sensitivity (se)-specificity (sp)): tongue inspection (se 0.210-sp 1.000), meat inspection (se 0.221-sp 1.000), Ab-ELISA (se 0.358-sp 0.917), Ag-ELISA (se 0.867-sp 0.947). To validate the estimates obtained from the model we performed a second study: 65 randomly purchased Zambian village pigs were bled for serum antibody and antigen determination, their tongue and meat inspected; and in addition, the carcasses were dissected for total cysticercus counts (gold standard). Cysticerci were found in 31 pigs (prevalence 0.477, 95% confidence interval 0.35-0.60), overlapping with the estimated prevalence in the first study. Sensitivity and specificity values obtained for the aforementioned tests in this study were in agreement with those estimated. A Bayesian analysis framework offers the possibility to combine prior opinion with experimental data to more accurately estimate the real prevalence of porcine cysticercosis in the absence of a gold standard.

Epidemiological survey of swine cysticercosis in two rural communities of West-Cameroon

To determine the prevalence of porcine cysticercosis, a survey was carried out in 27 villages belonging to two rural communities of West-Cameroon (Bafou and Bamendou). Between January and August, 2000, a total of 707 pigs were examined serologically and by tongue inspection. Serum samples were examined for circulating parasite antigen using a monoclonal antibody-based sandwich enzyme-linked-immunosorbent assay (Ag-ELISA) and for antibodies against cysticerci (Ab-ELISA). Seventy eight samples (11.0%) were found positive in the Ag-ELISA and 154 (21.8%) in the Ab-ELISA, while by tongue inspection on the same animals cysticerci were detected in 43 pigs (6.1%). Gibbs sampling using results of these three tests indicated that the estimated prevalence of porcine cysticercosis was 10.9%. Analysis of the Ag-ELISA results demonstrated that adult pigs showed a significantly higher seroprevalence (15%) than young ones (8.4%). There was no statistical difference in cysticercosis prevalence in pigs raised in households with or without a latrine. Animals that were reported to be usually confined were significantly less infected (9.9%) than free-roaming pigs (16.2%). Infection rates were significantly higher in pigs that had access to human faeces (13.8%) than those which did not have access (9.1%). This study has identified some community behavioural and environmental practices that should be modified to prevent continuous transmission of porcine cysticercosis.