Diagnostic efficacy of monoclonal antibody based sandwich enzyme linked immunosorbent assay (ELISA) for detection of Fasciola gigantica excretory/secretory antigens in both serum and stool

Advances in diagnostic approaches to Fasciola infection in animals and humans: An overviews

Fasciolosis, caused by Fasciola hepatica and F. gigantica, is an impediment to the livestock industry’s expansion and has a massively negative socio-economic impact due to its widespread prevalence in livestock. It is a waterborne zoonosis affecting human populations in the countries where rural economies are associated with livestock rearing. Conventional diagnosis of Fasciola infection is done by detecting parasite eggs in the faeces of infected animals or by immunological methods. Accurate and quick immunodiagnosis of Fasciola infection in animals and humans is based on the detection of antibodies and specific antigens expressed in the prepatent stage of the parasite. Both molecular and serodiagnostic tests developed thus far have enhanced the reliability of Fasciola diagnosis in both man and animals but are not widely available in resource-poor nations. A pen-side diagnostic test based on a lateral flow assay or a DNA test like loop-mediated isothermal amplification (LAMP) would be simple, fast, and cost-effective, enabling clinicians to treat animals in a targeted manner and avoid the development of drug resistance to the limited flukicides. This review focuses on the recent advances made in the diagnosis of this parasite infection in animals and humans.

Field evaluation of the enhanced MM3-COPRO ELISA test for the diagnosis of Fasciola hepatica infection in sheep

Fasciolosis is a severe zoonosis responsible for major economic losses in livestock. The enhanced MM3-COPRO test (eMM3-COPRO) and the commercial version BIO K 201 (Bio-X Diagnostics, Rochefort, Belgium) are widely used as immunodiagnostic tools for the specific detection of coproantigens released by Fasciola during the late prepatent and patent stages of infection. However, performance of the eMM3-COPRO has never been evaluated under field conditions. To address this gap, a large number of ovine faecal samples, collected in a region where fasciolosis is endemic (Galicia, NW Spain), were analyzed. Two groups of sheep flocks were selected according to the Fasciola infection status: ‘Fasciola-free’ and ‘Fasciola-infected’ flocks. ‘Fasciola-free’ flocks were seronegative flocks with no history of fasciolosis detected by either coproscopy or necropsy in the last 5 years. Faecal samples from these sheep were used to calculate a cut-off value for infection (OD = 0.021). The cut-off was calculated using a bootstrap resampling method that enables estimation of the sampling distribution of the statistical parameters without making assumptions about the underlying data distribution. ‘Fasciola-infected’ flocks were characterized by high seroprevalence, a history of fasciolosis and periodical treatment with flukicides. Samples from these flocks were used to estimate the diagnostic accuracy of the eMM3-COPRO relative to coproscopy, which although limited by poor sensitivity is the only reference test available for diagnosing fasciolosis in vivo. To overcome this limitation, all animals classified positive by eMM3-COPRO were treated with triclabendazole and then retested. The eMM3-COPRO displayed higher sensitivity than coproscopy, as it detected coproantigens in all samples with positive coproscopy and in 12% of samples with negative coproscopy. The test also proved highly specific as coproantigens disappeared after the treatment. The eMM3-COPRO was less time consuming than coproscopy, particularly when the procedure involved numerous samples, and showed promise as a tool for monitoring flukicide efficacy.

Recent Developments in Recombinant Proteins for Diagnosis of Human Fascioliasis

Fascioliasis is an important neglected tropical disease that causes severe injury to the bile ducts and liver. Therefore, a rapid and accurate method for detection of Fasciola hepatica infection plays a vital role in early treatment. Currently, the diagnosis of fascioliasis is mainly conducted via serological tests using the excretory/secretory (E/S) products, which might cross-react with antigens from other helminth parasitic diseases. Hence, the development of serodiagnosis test using recombinant antigens may contribute to differentiate fascioliasis from other helminth infections. In the past 20 years, many attempts have been made to exert different F. hepatica recombinant antigens to obtain a well-established standard assay with high accuracy. In this review, we address recent studies that refer to the development of serodiagnosis tests for diagnosis of human fascioliasis based on the candidate recombinant antigens produced by different approaches. Meanwhile, in the present review, some main factors have been highlighted to improve the accuracy of diagnostic tests such as the effect of refolding methods to recover antigens' tertiary structure as well as applying a mixture of recombinant antigens with the highest sensitivity and specificity to improve the accuracy of diagnostic tests.

Fascioliasis and fasciolopsiasis: Current knowledge and future trends

Food-borne zoonotic trematodiases are classified as neglected diseases by the World Health Organization. Among them, fascioliasis is caused worldwide by Fasciola hepatica and F. gigantica, and represent a huge problem in livestock production and human health in endemic areas. Fasciolopsis buski, restricted to specific regions of Asia, causes fasciolopsiasis. The incidence of these trematodiases is underestimated due to under-reporting and to the lack of sensitive and widely accepted tool for their diagnosis. This, together with a rising trend in reporting of drug resistance and the need for an effective vaccine against these parasites, pose a challenge in the effective control of these diseases. Here, the latest reports on fascioliasis outbreaks between 2000 and 2020 and the most recent advances in their epidemiology, diagnosis, treatment and control are revised. Finally, future needs in the field of fascioliasis and fasciolopsiasis are presented, which could be addressed based on current knowledge and by means of new emerging technologies.

Development of Cytochrome B, a new candidate gene for a high accuracy detection of Fasciola eggs in fecal specimens

Fasciolosis among domestic ruminants has resulted in a decrease in the production of milk products and has occasionally led to the deaths of young ruminants due to of acute infections. This study aimed to discriminate between the eggs of Fasciola gigantica and other trematode eggs in samples collected from ruminant feces specimens using PCR-based methods with the new candidate gene Cytochrome B (CYTB). A species-specific primer was developed with a high degree of sensitivity (3.285 pg). The primer was able to amplify the F. gigantica genomic DNA and there were no positive results with the other related trematodes (Paramphistomum sp., Orthocoelium sp., Fischoederius sp., Calicophoron sp., Echinostoma revolutum, E. cinetorchis, E. ilocanum and Isthmiophora hortensis), freshwater snails (Lymnaea auricularia, Bithynia siamensis, Indoplanorbis exustus, Melanoides tuberculata, Tarebia granifera) or definitive hosts (Bos primigenius and Bubalus bubalis). The minimum concentration of DNA from eggs that could be give a positive result was 3.285 pg. Moreover, the results of the study confirmed the existence of F. gigantica in Nakhon Pathom Province with a high prevalence (28.57%) and revealed the area of infection through epidemiological mapping. Thus, the species-specific primer and epidemiological data in this study may be helpful for use in epidemiological studies, phylogenetic studies and veterinary studies in the future.

Single Domain Antibodies as New Biomarker Detectors

Biomarkers are defined as indicators of biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. Biomarkers have been widely used for early detection, prediction of response after treatment, and for monitoring the progression of diseases. Antibodies represent promising tools for recognition of biomarkers, and are widely deployed as analytical tools in clinical settings. For immunodiagnostics, antibodies are now exploited as binders for antigens of interest across a range of platforms. More recently, the discovery of antibody surface display and combinatorial chemistry techniques has allowed the exploration of new binders from a range of animals, for instance variable domains of new antigen receptors (V_NAR) from shark and variable heavy chain domains (V_HH) or nanobodies from camelids. These single domain antibodies (sdAbs) have some advantages over conventional murine immunoglobulin owing to the lack of a light chain, making them the smallest natural biomarker binders thus far identified. In this review, we will discuss several biomarkers used as a means to validate diseases progress. The potential functionality of modern singe domain antigen binders derived from phylogenetically early animals as new biomarker detectors for current diagnostic and research platforms development will be described.

A. AS, Abidi SMA. Immunolocalization and immunodetection of the excretory/secretory (ES) antigens of Fasciola gigantica

The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance. Along with Fasciola hepatica, F. gigantica incurs huge economic losses to the agricultural sector. Because of unavailability of an effective and commercial vaccine, the earliest diagnosis of the disease is the only way to control the disease. The conventional coprological techniques are able to detect the disease only after the parasites get matured and starts releasing their eggs with the faeces of host, therefore prepatent infection remain undiagnosed. The alternative method is by serological tests that uses circulatory antigens. Despite high sensitivity, their reliability is quite low because of the common antigens shared between different helminth parasites. To overcome this, investigation was shifted to identify the copro-antigens which could be more sensitive and reliable. In the present study, we tried to identify some of the immunodominant proteins from the Excretory Secretory (ES) product of F. gigantica which can be further characterized and used for early detection of infection and also as drug and vaccine candidates. The ES products of F. gigantica were collected and used for raising the polyclonal antibody in rabbit. The polypeptide profile was generated as well as immunogenic polypeptides were identified. The Source of ES antigen was immunolocalized using confocal microscopy and dot blot assay was performed to diagnose field infection. The polypeptide profile of ES products revealed a total of 24 polypeptides out of which 12 immunogenic polypeptides were identified by western blotting. Confocal micrographs showed the immunolocalization of antigens in the intestinal caecae, vitalline glands, gonads as well as in the tegument of the worm. The dot blot assay confirmed the utility of ES products for the detection of field infection. Subsequently, cross reactivity was found negative with Gigantocotyle explanatum; an amphitome parasite of same habitat. However, the cross reactivity with other helminths needs to be worked out.

Immunodiagnosis of Human Fascioliasis: An Update of Concepts and Performances of the Serological Assays

Human Fascioliasis (HF) is a foodborne neglected parasitic disease caused by Fasciola hepatica and Fasciola gigantica. New epidemiological data suggest that the endemic areas of the disease are expanding and HF is being reported from areas where it was previously not observed. Diagnosis of HF is challenging. Performances of parasitological approaches, based on the detection of parasite's egg in the stool, are not satisfactory. Currently serological methods for the diagnosis of HF are mainly based on detection of anti-Fasciola antibodies in serum. Although, there have been some improvement in the development of immunological diagnostic tests for the diagnosis of HF, yet these tests suffer from insufficiency in sensitivity or/and specificity. Detection of antigens, rather than antibodies, seems to be a suitable approach in the diagnosis of HF. Antigen can be detected in sera or stool of the fascioliasis patients. Circulating antigen in serum disappears within a short time and most of the circulating antigens are in immune complex forms which are not freely available to be detected. Therefore, antigenemia might not be an appropriate method for the diagnosis of HF. Detection of antigen in stool (coproantigens) seems to be a suitable alternative method for the diagnosis of HF. Recent data provided convincing evidence that detection of coproantigen improved and simplified the diagnosis of HF. The present review highlights the new achievements in designing and improvement of diagnostic approaches for the immunodiagnosis of HF. Moreover, current status of the available immunodiagnostic techniques for the diagnosis of HF, their strengths and weaknesses has been discussed.

Immunodiagnosis of paramphistomosis using monoclonal antibody-based sandwich ELISA for detection ofParamphistomum gracilecirculating 16 kDa antigen

In this study, we have produced a monoclonal antibody (MoAb) against 16 kDa antigen ofParamphistomum gracile(16 kDaAgPg), and developed an accurate sandwich enzyme-linked immunosorbent assay (sandwich ELISA) for the detection of circulating 16 kDaAg in the serum and fecal samples from cattle naturally infected withP. gracile. MoAb 1D10 was immobilized on a microtitre plate, and the antigen in the samples was captured and detected with biotinylated rabbit anti-16 kDaAgPg antibody. The lower detection limit of sandwich ELISA was 3·5 pg mL−1, and no cross-reaction with other parasite antigens was evaluated. The reliability of the assay was examined using the serum and fecal samples from cattle naturally infected withP. gracile, Fasciola gigantica, Moniezia benedeni, Trichurissp.,Strongyloidessp., strongylids and non-infected animals. The sandwich ELISA showed the sensitivity, specificity and accuracy at 98·33, 100 and 99·55% (serum samples), and 96·67, 100 and 99·09% (fecal samples). Therefore, this detection method is a rapid and excellent potential assay for the accurate diagnosis of paramphistomosis.

Production of Monoclonal Antibody Against Excretory-Secretory Antigen of Fasciola hepatica and Evaluation of Its Efficacy in the Diagnosis of Fascioliasis

Parasitological methods are not helpful for the diagnosis of fascioliasis in acute and invasive periods of the disease. Detection of coproantigens seems to be a suitable alternative approach in the diagnosis of fascioliasis. The present study aimed to develop a reliable antigen detection system, using monoclonal antibodies raised against excretory-secretory (ES) antigen of Fasciola hepatica, for the diagnosis of fascioliasis. Fasciola adult worms were collected from the bile ducts of infected animals. Species of the fluke was determined by polymerase chain reaction-restriction fragment length polymorphism (RFLP-PCR). ES antigen of F. hepatica was prepared. For production of monoclonal antibodies, mice were immunized with ES antigens of F. hepatica. Spleen cells from the immunized mice were fused with NS-1 myeloma cells, using polyethylene glycol. Hybridoma cells secreting specific antibody were expanded and cloned by limiting dilution. Moreover, polyclonal antibody was produced against F. hepatica ES antigen in rabbits. A capture enzyme-linked immunosorbent assay (ELISA) system, using produced monoclonal antibody, was designed and stool samples of infected animals along with control samples were tested by the system. The capture ELISA detected the coproantigen in 27 of 30 (90%) parasitologically confirmed fascioliasis cases, while 4 of 39 (10.25%) samples infected with other parasitic infections showed a positive reaction in this system. No positive reactivity was found with healthy control samples. Accordingly, sensitivity of 90% and specificity of 94.2% were obtained for the capture ELISA system. The results were compared with those obtained with commercial BIO-X ELISA, and a very good (kappa = 0.9) agreement was found between the commercial kit and the developed capture ELISA. Findings of this study showed that the produced monoclonal antibody has appropriate performance for the detection of Fasciola coproantigen in stool samples and can be appropriately used for the diagnosis of fascioliasis.

Immunodiagnostic monoclonal antibody-based sandwich ELISA of fasciolosis by detection ofFasciola giganticacirculating fatty acid binding protein

Up to now, parasitological diagnosis of fasciolosis is often unreliable and possesses low sensitivity. Hence, the detection of circulating parasite antigens is thought to be a better alternative for diagnosis of fasciolosis, as it reflects the real parasite burden. In the present study, a monoclonal antibody (MoAb) against recombinantFasciola giganticafatty acid binding protein (rFgFABP) has been produced. As well, a reliable sandwich enzyme-linked immunosorbent assay (sandwich ELISA) has been developed for the detection of circulating FABP in the sera of mice experimentally and cattle naturally infected withF. gigantica. MoAb 3A3 and biotinylated rabbit anti-recombinant FABP antibody were selected due to their high reactivities and specificities. The lower detection limit of sandwich ELISA was 5 pg mL−1, and no cross-reaction with other parasite antigens was observed. This assay could detectF. giganticainfection from day 1 post infection. In experimental mice, the sensitivity, specificity and accuracy of this assay were 93·3, 100 and 98·2%, while in natural cattle they were 96·7, 100 and 99·1%. Hence, this sandwich ELISA method showed high efficiencies and precisions for diagnosis of fasciolosis byF. gigantica.

Immunodiagnosis of Fasciola gigantica Infection Using Monoclonal Antibody-Based Sandwich ELISA and Immunochromatographic Assay for Detection of Circulating Cathepsin L1 Protease

BACKGROUND

Tropical fasciolosis caused by Fasciola gigantica infection is one of the major diseases infecting ruminants in the tropical regions of Africa and Asia including Thailand. Parasitological diagnosis of fasciolosis is often unreliable and possesses low sensitivity. Therefore, the detection of circulating parasite antigens is thought to be a better alternative for diagnosis of fasciolosis, as it reflects the real parasite burden.

METHODS

In this study, we have produced a monoclonal antibody (MoAb) against recombinant F. gigantica cathepsin L1 (rFgCatL1), and developed both sandwich enzyme-linked immunosorbent assay (sandwich ELISA) and immunochromatographic (IC) test for rapid detection of circulating cathepsin L1 protease (CatL1) in the sera from mice experimentally and cattle naturally infected with Fasciola gigantica. MoAb 4E3 and biotinylated rabbit anti-recombinant CatL1 antibody were selected due to their high reactivities and specificities.

RESULTS

The lower detection limits of sandwich ELISA and IC test were 3 pg/ml and 0.256 ng/ml, respectively. Sandwich ELISA and IC test could detect F. gigantica infection from day 1 to 35 post infection. In experimental mice, the sensitivity, specificity and accuracy were 95%, 100% and 98.6% (for sandwich ELISA), and 93%, 100% and 98.2% (for IC test), while in natural cattle they were 98.3%, 100% and 99.5% (for sandwich ELISA), and 96.7%, 100% and 99.1% (for IC test).

CONCLUSIONS

These two assay methods showed high efficiencies and precisions for diagnosis of fasciolosis by F. gigantica.

Serological and coprological analyses for the diagnosis of Fasciolagigantica infections in bovine hosts from Sargodha, Pakistan

A serological and coprological survey of fasciolosis was conducted in bovine hosts from the Sargodha district, Pakistan using excretory–secretory (ES) antigens of Fasciola gigantica from cattle and buffaloes. Livers, faecal and blood samples of 146 cattle and 184 buffaloes were collected from slaughterhouses and examined for the presence of any Fasciola in bile ducts and ova in faeces. Serum was separated. ES antigens were prepared by incubating adult Fasciola in phosphate-buffered saline for 6–8 h and then filtering using a 0.22-μm syringe filter. Checkerboard titration was performed and optimum concentrations of antigen and serum were determined. Sero-prevalence was found to be 50.00 and 38.35% in buffalo and cattle, respectively. Using liver examination as the gold standard, enzyme-linked immunosorbent assay (ELISA) sensitivity was found to be 100% in both buffalo and cattle as compared with that of coprological examination in buffalo (61.79%) and cattle (54.54%). This indigenous ELISA was also highly specific, with values of 96.84 and 98.90% in buffalo and cattle, respectively. Positive predictive values were calculated as 96.74 and 98.21% in buffalo and cattle, respectively, while negative predictive values were 100%. For the validation of indigenous ELISA in field surveys, faecal and blood samples were collected from six sub-districts (tehsils) in the district of Sargodha. Sera were screened for the presence of anti-fasciola antibodies using both the indigenous and commercial ELISA kits. While both kits were equally sensitive, the indigenous ELISA was found to be more specific. The highest prevalence of fasciolosis was found in December, as ascertained using both serological and coprological examination. Significant differences were found in prevalences of fasciolosis in different sub-districts and age groups, together with feeding and watering systems.

Performance of a 27 kDa Fasciola hepatica Antigen in the Diagnosis of Human Fascioliasis

Background:

Serological diagnosis, based on antigenic fractions of the parasite can be used for the early diagnosis of human fascioliasis. The current study aimed to evaluate the efficacy of a 27 kDa immunodominant antigen of Fasciola hepatica adult worms, in an indirect enzyme-linked immunosorbent assay (ELISA) system for serological diagnosis of human fascioliasis.

Materials and Methods:

The immunodiagnosis of human fascioliasis, using a 27 kDa immunodominant antigen, purified from F. hepatica somatic antigens (SAs), was evaluated by Western blotting and ELISA with sera samples of human fascioliasis patients, healthy controls and patients with other parasitic infections.

Results:

Using western blotting, from 12 sera of fascioliasis patients, 11 sera (91.6%) detected the 27 kDa subunit. None of 30 samples from healthy controls or 32 sera from nonfascioliasis patients reacted with the 27 kDa antigen. Accordingly, sensitivity and specificity of the system was found to be 91.6% and 100%, respectively. The 27 kDa antigen was purified from the SAs and was used in an indirect ELISA system. Of 15 sera of fascioliasis patients, all (100%) were found to be positive by ELISA whereas only 4 cases (6.25%) of nonfascioliasis patients or healthy controls were false-positive by this system. Accordingly, the sensitivity and specificity of the test were 100% and 93.6%, respectively.

Conclusion:

Findings of this study demonstrated that both Western blotting and the indirect ELISA, based on the 27 kDa subunit of F. hepatica SA, are reliable methods for serodiagnosis of human fascioliasis.

Saposin-like protein 2 has an immunodiagnostic potential for detecting Fasciolosis gigantica

Saposin-like protein 2 (SAP-2) plays an important role in the digestive process of Fasciola gigantica (Fg). It is one of the major proteins synthesized by the caecal epithelial cells and released into fluke's excretion-secretion. Therefore, FgSAP-2 is a plausible target for detecting fasciolosis. A polyclonal antibody (PoAb) against recombinant FgSAP-2 was produced by immunizing rabbits with the recombinant protein (rFgSAP-2), and used in sandwich ELISA assay to detect the circulating FgSAP-2 in sera of mice experimentally infected with F. gigantica metacercariae. The assay could detect rFgSAP-2 and the native FgSAP-2 in the excretory-secretory (ES) and whole body (WB) fractions of adult F. gigantica at the concentrations as low as 38 pg/ml, 24 ng/ml, and 102 ng/ml, respectively. As well, the sera from mice experimentally infected with F. gigantica were tested positive by this sandwich ELISA, which exhibited sensitivity, specificity, false positive rate, false negative rate and accuracy at 99.99, 98.67, 1.33, 0.01 and 99.32%, respectively. Therefore, this assay could be used for diagnosis of fasciolosis by F. gigantica.

Diagnosis of human fascioliasis by stool and blood techniques: update for the present global scenario

Before the 1990s, human fascioliasis diagnosis focused on individual patients in hospitals or health centres. Case reports were mainly from developed countries and usually concerned isolated human infection in animal endemic areas. From the mid-1990s onwards, due to the progressive description of human endemic areas and human infection reports in developing countries, but also new knowledge on clinical manifestations and pathology, new situations, hitherto neglected, entered in the global scenario. Human fascioliasis has proved to be pronouncedly more heterogeneous than previously thought, including different transmission patterns and epidemiological situations. Stool and blood techniques, the main tools for diagnosis in humans, have been improved for both patient and survey diagnosis. Present availabilities for human diagnosis are reviewed focusing on advantages and weaknesses, sample management, egg differentiation, qualitative and quantitative diagnosis, antibody and antigen detection, post-treatment monitoring and post-control surveillance. Main conclusions refer to the pronounced difficulties of diagnosing fascioliasis in humans given the different infection phases and parasite migration capacities, clinical heterogeneity, immunological complexity, different epidemiological situations and transmission patterns, the lack of a diagnostic technique covering all needs and situations, and the advisability for a combined use of different techniques, at least including a stool technique and a blood technique.

Evaluation of antibody response to various developmental stage specific somatic antigens of Paramphistomum epiclitum in goats

Electrophoretic analysis of various developmental stage specific somatic antigens of Paramphistomum epiclitum (Digenea: Paramphistomidae), namely, metacercariae (McAg), immature intestinal flukes (ImIAg), immature ruminal flukes (ImRAg), and adult flukes (AAg), was done by native polyacrylamide gel electrophoresis. Result revealed presence of 3 (range 15.2-40.3 kDa), 13 (9.3-121.2 kDa), 14 (9.3-169.3 kDa), and 15 (8.0-169.3 kDa) polypeptides in McAg, ImIAg, ImRAg, and AAg, respectively. With an aim to identify a suitable immunodiagnostic antigen for early diagnosis of amphistomosis, the IgG antibody response to various developmental stage antigens in goats experimentally infected with metacercariae of P. epiclitum was evaluated by ELISA. The highest OD values were recorded with ImIAg which ranged between 0.23 and 0.55 with a significant increase from the 2nd week till 8th week of infection with a peak at 6th week. The analysis of statistical significance using a one-way analysis of variance with multiple pair wise comparisons revealed that IgG response was significantly higher with all antigens (P < 0.01) except McAg (P > 0.05) with a maximum mean difference of 0.1838 in comparison to control with ImIAg, thus, indicating that ImIAg which could be further exploited for its potential is a candidate for immunodiagnostic antigen for early diagnosis of amphistomosis.

Immunodetection of Fasciola gigantica circulating antigen in sera of infected individuals for laboratory diagnosis of human fascioliasis

Currently, the laboratory diagnosis of human fascioliasis is based on the parasitological examination of parasite eggs in stool specimens and serological detection of specific antibodies in serum samples, which are often unreliable diagnostic approaches. Ideally, a sensitive and specific diagnostic test for Fasciola infection should be based on the detection of circulating Fasciola antigen, which implies active infection. Here, a 27-kDa-molecular-mass antigen was identified in a Fasciola gigantica adult worm antigen preparation, excretory-secretory products, and sera from F. gigantica-infected individuals, and it was not detected in antigenic extracts of other parasites and sera from noninfected individuals. The target antigen was isolated and partially characterized as a protein. Immunoperoxidase staining located the target epitope within teguments and guts of F. gigantica adult worms. The performance characteristics of a newly developed enzyme-linked immunosorbent assay (ELISA) based on F. gigantica circulating antigen detection in serum (FgCA-27 ELISA) were investigated using sera of 120 parasitologically diagnosed F. gigantica-infected individuals and 80 noninfected individuals. The area under the receiving operating characteristic (ROC) curve (AUC) for ELISA was significantly high (AUC = 0.961, P < 0.0001) for discriminating Fasciola-infected and noninfected individuals. The developed assay showed high degrees of sensitivity, specificity, and efficiency (>93%), and a significant correlation (r = 0.715, P < 0.0001) between antigen level and parasite egg count was shown. In conclusion, a 27-kDa Fasciola antigen was identified in sera of F. gigantica-infected individuals. A highly sensitive and specific Fasciola antigen detection assay, FgCA-27 ELISA, was developed for laboratory diagnosis of human fascioliasis.

Diagnosis of Fasciola gigantica infection using a monoclonal antibody-based sandwich ELISA for detection of circulating cathepsin B3 protease

A reliable monoclonal antibody (MoAb)-based sandwich enzyme-linked immunosorbent assay (sandwich ELISA) was developed for the detection of circulating cathepsin B3 protease (CatB3) in the sera from mice experimentally infected with Fasciola gigantica and cattle naturally infected with the same parasite. The MoAb 2F9 and biotinylated rabbit polyclonal anti-recombinant CatB3 antibody were selected due to their high reactivities and specificities to F. gigantica CatB3 antigen based on indirect ELISA and immunoblotting. The lower detection limit of the sandwich ELISA assay was 10, 100 and 400pg/ml, when applied for the detection of rCatB3 antigen and CatB3 in whole body (WB) of newly excysted juveniles (NEJ) and metacercariae (Met) of F. gigantica, respectively. This sandwich ELISA assay could detect F. gigantica infection from day 1 to 35 post infection and revealed that circulating level of CatB3 peaked at day 1 post infection. In contrast, the antibody detection by indirect ELISA could only demonstrate the antibody level from 35 days post infection. The reliability of the assay method was evaluated using serum samples from mice infected with F. gigantica or Schistosoma mansoni, and hamsters infected with Opisthorchis viverrini, as well as normal mice and hamsters. In addition, sera from cattle infected with Paramphistomum cervi, Strongylid, Trichuris sp. and Strongyloides sp., as well as sera from normal cattle were also assessed. In experimental mice, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value, false positive rate, false negative rate and accuracy of ELISA were 95%, 100%, 100%, 97.9%, 0%, 5.3% and 98.5%, while in natural cattle they were 96.7%, 100%, 100%, 98.5%, 0%, 3.4% and 98.9%, respectively. Hence, this assay method showed high efficient and precision for early diagnosis of fasciolosis by F. gigantica.

The global burden of fasciolosis in domestic animals with an outlook on the contribution of new approaches for diagnosis and control

Fasciolosis is an economically important disease for livestock, as well as being zoonotic. Recent figures on the prevalence of this disease have caused alarm concerning its potential for an increased prevalence in the future. The prevalence of fascioliosis has been documented from different regions of the world, helping us identify areas where future research needs to be focused. This manuscript is a review of the current status of the disease, the pathogenic species involved, diagnostic techniques (with new modifications and comparative specificity, sensitivity, and rapidity of these tests), chemotherapy, and vaccination. This also encompasses inaccurate reports on vaccination and drug development as well as the latest technologies to find promising candidates for drugs and vaccines. Drugs with lower efficacy have been used on some farms which lead to exacerbation of the clinical disease, presumably due to the development of drug resistance. Future studies should be focused on (1) the use of the most reliable diagnostic tests for periodic monitoring of the disease, (2) insights of the ecobiology and transmission dynamics of the snail intermediate host and the best possible methods of their control, (3) in vitro and in vivo testing of chemotherapeutic compounds using sensitive methods, and (4) the identification of novel drug and vaccine candidates using modern molecular markers. This approach may help increase the reliability of chemotherapeutic agents and control nuisance, ultimately reducing the economic losses attributable to the livestock industry around the world.

Detection of microorganisms in granulomas that have been formalin-fixed: review of the literature regarding use of molecular methods

Granuloma is an organized aggregate of immune cells that under the microscope appear as epithelioid macrophages. A granuloma can only be diagnosed when a pathologist observes this type of inflammation under the microscope. If a foreign body or a parasite is not observed inside the granuloma, stains for acid-fast bacilli and fungi are ordered since mycobacteria and fungi are frequently the cause of this type of inflammation. It is calculated that 12 to 36% of granulomas do not have a specific etiology and many have wondered if with new molecular methods we could reduce this number. This paper will summarize the frequently known causes of granulomas and will present the recent literature regarding the use of molecular techniques on tissue specimens and how these have helped in defining causative agents. We will also briefly describe new research regarding formation and function of granulomas and how this impacts our ability to find an etiologic agent.

New developments in epidemiology, diagnosis, and treatment of fascioliasis

PURPOSE OF REVIEW

This review focuses on the recent developments in the epidemiology, burden of disease, diagnostic tests, and treatment of fascioliasis.

RECENT FINDINGS

Recent epidemiologic data suggest that either the endemic areas are expanding or disease is being recognized in areas where it was not previously observed. In addition, recent data highlight the effects of fascioliasis on childhood anemia and nutrition. Diagnosis remains problematic, but newer diagnostic tests including antibody, antigen, and DNA detection tests may facilitate earlier diagnosis. Recent studies suggest that point-of-care testing may soon be possible. Treatment with triclabendazole is effective, but resistance is emerging in livestock and may pose a threat for patients.

SUMMARY

Fascioliasis continues to emerge as an important neglected disease, with new studies highlighting the under-recognized burden of disease. Further studies are needed on burden of disease, improved diagnosis, and alternative to triclabendazole treatment.

Development and evaluation of a single-step duplex PCR for simultaneous detection of Fasciola hepatica and Fasciola gigantica (family Fasciolidae, class Trematoda, phylum Platyhelminthes)

A single-step multiplex PCR (here referred to as a duplex PCR) has been developed for simultaneous detection and diagnosis of Fasciola hepatica and F. gigantica. These species overlap in distribution in many countries of North and East Africa and Central and Southeast Asia and are similar in egg morphology, making identification from fecal samples difficult. Based on a comparative alignment of mitochondrial DNA (mtDNA) spanning the region of cox1-trnT-rrnL, two species-specific forward primers were designed, FHF (for F. hepatica) and FGF (for F. gigantica), and a single reverse primer, FHGR (common for both species). Conventional PCR followed by sequencing was applied using species-specific primer pairs to verify the specificity of primers and the identity of Fasciola DNA templates. Duplex PCR (using three primers) was used for testing with the DNA extracted from adult worms, miracidia, and eggs, producing amplicons of 1,031 bp for F. hepatica and 615 bp for F. gigantica. The duplex PCR failed to amplify from DNA of other common liver and intestinal trematodes, including two opisthorchiids, three heterophyids, an echinostomid, another fasciolid, and a taeniid cestode. The sensitivity assay showed that the duplex PCR limit of detection for each Fasciola species was between 0.012 ng and 0.006 ng DNA. Evaluation using DNA templates from 32 Fasciola samples (28 adults and 4 eggs) and from 25 field-collected stools of ruminants and humans revealed specific bands of the correct size and the presence of Fasciola species. This novel mtDNA duplex PCR is a sensitive and fast tool for accurate identification of Fasciola species in areas of distributional and zonal overlap.

Molecular, biochemical, and morphometric characterization of Fasciola species potentially causing zoonotic disease in Egypt

Fascioliasis is an important disease caused by Fasciola hepatica and Fasciola gigantica. The distributions of both species overlap in many areas of Asia and Africa including Egypt. Fifty adult Fasciola worms were collected from livers of cattle and sheep slaughtered in abattoirs, Cairo, Egypt. They were subjected to morphological and metric assessment of external features of fresh adults, morphological and metric assessment of internal anatomy of stained mounted worms, determination of electrophorezed bands of crude adult homogenates using SDS-PAGE, and molecular characterization of species-specific DNA segments using RFLP-PCR. It was found that the correlation between conventional morphology and its morphotype was statistically significant (P value = 0.00). Using SDS-PAGE, 13 bands were detected among both genotypes of Fasciola (35.7, 33.6, 32.4, 29.3, 27.5, 26, 24.4, 23, 21.45, 19, 16.75, 12.5, and 9.1 kDa).The most prevalent bands were that with a molecular weight of 29.3, 26, and 19 kDa. Bands detected were common for both species, but protein bands could not distinguish between F. hepatica and F. gigantica. The result of PCR for the amplification of the selected 28S rDNA fragment with the designed primer set yielded 618 bp long PCR products for F. hepatica and F. gigantica. Different band patterns generated after digestion of the 618 bp segment by the enzyme AvaII obtained with F. hepatica showed segments of the length 529, 62, 27 bp, while with F. gigantica 322, 269, 27 bp bands were obtained. Genotyping revealed no equivocal results. The conventional morphological parameters for species determination of Fasciola spp. endemic in Egypt were evaluated versus protein bands characterization and genotyping. It was concluded that conventional morphological and metric assessments were not useful for differentiation between F. gigantica and F. hepatica due to extensive overlap in the relative ranges. Similar conclusion was reached concerning protein band characterization where the patterns of protein banding were mostly similar. In contrast, genotyping using RFLP-PCR gave consistent results and clear differentiation between the two species. Considering the implications of proper speciation of endemic parasites on clinical evaluation, therapy, epidemiology, and control measures, speciation of parasites is currently revised on molecular basis. The presently used molecular tool is therefore recommended for further study to help draw a proper map for geographical distribution of Fasciola species.