Coproantigen detection in dogs experimentally and naturally infected with Echinococcus granulosus by a monoclonal antibody-based enzyme-linked immunosorbent assay

Development and Validation of a Copro-Enzyme-Linked Immunosorbent Assay Sandwich for Detection of Echinococcus granulosus-Soluble Membrane Antigens in Dogs

Cystic echinococcosis (CE) is a parasitic zoonosis caused by the larval stage of the tapeworm Echinococcus granulosus. Detection of the adult stage in the canine definitive host is essential for estimating infection rates, surveillance and monitoring of CE control programs. This study sought to develop and validate a coproantigen sandwich enzyme-linked immunosorbent assay (copro-ELISA), based on antibodies against E. granulosus-soluble membrane antigens (EGMA), that is capable of distinguishing infected and noninfected dogs. Anti-E. granulosus polyclonal immunoglobulin G antibodies were obtained from rabbit antiserum against EGMA. Optimization of the test was performed with 51 positive and 56 negative stool samples of canine echinococcosis. Specificity, sensitivity, cross-reactivity, intra- and inter-assay precision, and over time detection were evaluated. According to the receiver operating characteristic analysis, the diagnostic sensitivity and specificity were 96.1% (CI: 85.9-99.6) and 98.2% (CI: 89.5-100), respectively. Negative and positive predictive values were 96.5% (CI: 91.7-100) and 98% (CI: 94.1-100), respectively. No cross-reactivity with Taenia hydatigena, Dipylidium caninum, or Toxocara canis was observed. Intra- and inter-assay repeatability showed values of less than 15% of the variation coefficient. The over time detection was from 20 to 27 days postinfection with E. granulosus. The copro-ELISA based on EGMA detection offers a simplified in-house development of diagnostic testing. This assay showed high specificity and sensitivity and had no cross-reactivity with other parasites. Further studies and development of this test in a kit format may be useful for the detection of active infection in dogs living in CE endemic regions.

Laboratory Diagnosis of Echinococcus spp. in Human Patients and Infected Animals

Among the species composing the genus Echinococcus, four species are of human clinical interest. The most prevalent species are Echinococcus granulosus and Echinococcus multilocularis, followed by Echinococcus vogeli and Echinococcus oligarthrus. The first two species cause cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively. Both diseases have a complex clinical management, in which laboratory diagnosis could be an adjunctive to the imaging techniques. To date, several approaches have been described for the laboratory diagnosis and followup of CE and AE, including antibody, antigen and cytokine detection. All of these approaches are far from being optimal as adjunctive diagnosis particularly for CE, since they do not reach enough sensitivity and/or specificity. A combination of several methods (e.g., antibody and antigen detection) or of several (recombinant) antigens could improve the performance of the adjunctive laboratory methods, although the complexity of echinococcosis and heterogeneity of clinical cases make necessary a deep understanding of the host-parasite relationships and the parasite phenotype at different developmental stages to reach the best diagnostic tool and to make it accepted in clinical practice. Standardization approaches and a deep understanding of the performance of each of the available antigens in the diagnosis of echinococcosis for the different clinical pictures are also needed. The detection of the parasite in definitive hosts is also reviewed in this chapter. Finally, the different methods for the detection of parasite DNA in different analytes and matrices are also reviewed.

Echinococcosis: Control and Prevention

Human cystic echinococcosis (CE) has been eliminated or significantly reduced as a public health problem in several previously highly endemic regions. This has been achieved by the long-term application of prevention and control measures primarily targeted to deworming dogs, health education, meat inspection, and effective surveillance in livestock and human populations. Human CE, however, remains a serious neglected zoonotic disease in many resource-poor pastoral regions. The incidence of human alveolar echinococcosis (AE) has increased in continental Europe and is a major public health problem in parts of Eurasia. Better understanding of wildlife ecology for fox and small mammal hosts has enabled targeted anthelmintic baiting of fox populations and development of spatially explicit models to predict population dynamics for key intermediate host species and human AE risk in endemic landscapes. Challenges that remain for echinococcosis control include effective intervention in resource-poor communities, better availability of surveillance tools, optimal application of livestock vaccination, and management and ecology of dog and wildlife host populations.

Echinococcus granulosus: Epidemiology and state-of-the-art of diagnostics in animals

Diagnosis and detection of Echinococcus granulosus (sensu lato) infection in animals is a prerequisite for epidemiological studies and surveillance of echinococcosis in endemic, re-emergent or emergent transmission zones. Advances in diagnostic approaches for definitive hosts and livestock, however, have not progressed equally over the last 20 years. Development of laboratory based diagnostics for canids using coproantigen ELISA and also coproPCR, have had a huge impact on epidemiological studies and more recently on surveillance during hydatid control programmes. In contrast, diagnosis of cystic echinococcosis (CE) in livestock still relies largely on conventional post-mortem inspection, despite a relatively low diagnostic sensitivity especially in early infections, as current serodiagnostics do not provide a sufficiently specific and sensitive practical pre-mortem alternative. As a result, testing of dog faecal samples by coproantigen ELISA, often combined with mass ultrasound screening programmes for human CE, has been the preferred approach for monitoring and surveillance in resource-poor endemic areas and during control schemes. In this article we review the current options and approaches for diagnosis of E. granulosus infection in definitive and animal intermediate hosts (including applications in non-domesticated species) and make conclusions and recommendations for further improvements in diagnosis for use in epidemiological studies and surveillance schemes.

Epidemiological updates and economic losses due to Taenia hydatigena in sheep from Sardinia, Italy

The aim of this study was to investigate the epidemiology and transmission of Taenia hydatigena in sheep and dogs from Sardinia and the economic estimation of losses due to this metacestodosis in lambs. A total of 7781 Sarda breed lambs were examined at abattoirs for the detection of Cysticercus tenuicollis or necrotic-haemorrhagic tracks of their migration. Morphological and molecular identification of parasites was carried out. Individual faecal samples from 300 dogs were examined for copromicroscopic investigations and coproELISA assay. An overall prevalence of 14.6% for T. hydatigena cysticercosis was found in the examined lambs. In total, 10,807 parasitary tracks were found, with an abundance of 1.39 and an average intensity of 9.52. The molecular analysis of the isolates showed an overall pairwise nucleotide divergence for the CO1 and ND1 was of 0-3.1 and 0-3.3%, respectively. Low intra- and interspecific variation was recorded for C. tenuicollis isolates used in this study which suggested the absence of differentiation. Microscopic examination of dog faeces showed a total prevalence of 31.3% for endoparasites in the examined samples (94/300). Taeniid eggs were found in 8.3% of the dogs. The results of the monoclonal antibody ATH4 ELISA test showed a prevalence of 11% (33/300) for T. hydatigena coproantigens. The total economic costs related to cysticercosis amounted to almost € 330,000. The prevalence of C. tenuicollis in 14.6% of 30-40-day-old lambs highlights the high parasitic pressure by T. hydatigena in the territory of Sardinia, Italy.

Update on immunologic and molecular diagnosis of human strongyloidiasis

Human strongyloidiasis is an intestinal parasitosis that may affect 100 million individuals. However, the prevalence rates of this infection may represent smaller values than the actual data, mainly due to difficulties in its diagnosis. The aim of this study was to update the immunological and molecular methods applied to the diagnosis of human strongyloidiasis. There is a great diversity of techniques used in the diagnosis of this parasitosis, such as immunofluorescence antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA), immunoblotting, luciferase immunoprecipitation system (LIPS), dispstick and polymerase chain reaction (PCR), all with advantages and disadvantages, and with unique features for specific purposes. Considering the magnitude of strongyloidiasis and the importance of early diagnosis, due to the possibility of chronicity and hyperinfection, this study analyzes the different methods currently employed, and demonstrates the necessity of developing innovative methodologies, which also maintain diagnostic accuracy, particularly for regions with limited technological resources.

Epidemiological study and control trial of taeniid cestode infection in farm dogs in Qinghai Province, China

An epidemiological study and control trial were conducted to assess taeniid infection in farm dogs in Qinghai Province, China. To improve egg detection by fecal examination, a deworming step with praziquantel was incorporated into the sampling methodology. As a result, a marked increase in the number of egg-positive samples was observed in samples collected at 24 hr after deworming. Then, the fecal examination and barcoding of egg DNA were performed to assess the prevalence of taeniid species in dogs from Xinghai, Haiyan, Gangcha and Chengduo counties. Analysis of 277 dog feces revealed that taeniid cestodes, including Taenia spp. and Echinococcus granulosus, were highly prevalent in Xinghai (34.4%), but eggs were not found in Haiyan where a control trial on canine echinococcosis had been conducted 20 years previously. A control trial involving the administration of 5–10 mg/kg praziquantel to 90 farm dogs at 45-day intervals was conducted in Xinghai. The prevalence of taeniid cestodes in the dogs was reduced to 9.6% and 4.9% after one and two years, respectively, indicating that some dogs were not administered praziquantel properly. A questionnaire survey of farmers in Xinghai and Haiyan revealed that most farmers in Xinghai were not familiar with echinococcosis or the transmission route of the disease, while most farmers in Haiyan had a more thorough understanding of the disease. The findings implied that a program for educating local farmers would be important for efficiently controlling canine taeniid infection in the region.

Echinococcusinfections in Chinese dogs: a comparison of coproantigen kits

Coproantigen test kits forEchinococcusspp. worms in dogs, designed for commercial use, were obtained from three different Chinese producers, and were compared with a laboratory kit using reagents from New Zealand. None of the three producers would provide details of their test validation. From a known set of dog faeces obtained at necropsy from infected and uninfected dogs, and from faeces collected from dogs necropsied in the field, results differed between the kits. For field material, the Tiankang kit showed the best specificity but lacked sensitivity. The Combined kit showed best sensitivity but lacked specificity. Results for the Haitai kit were intermediate. With samples from experimentally infected dogs, both the Haitai and Combined kits lacked sensitivity. Kits will need to be validated by the user before they can be relied on to predict progress inEchinococcusspp. control in China or in other countries.

A monoclonal antibody-based copro-ELISA kit for canine echinococcosis to support the PAHO effort for hydatid disease control in South America

Cystic echinococcosis is still a major concern in South America. While some regions show advances in the control of the disease, others have among the highest incidence in the world. To reverse this situation the Pan American Health Organization (PAHO) has launched a regional project on cystic echinococcosis control and surveillance. An early concern of the program was the lack of a standardized diagnostic tool to monitor infection in dogs, a key target of control programs. Under this premise, we have developed a new copro-ELISA test after extensive screening of a large panel of monoclonal antibodies (MAbs) and polyclonal sera, which performs with high standards of sensitivity (92.6%) and specificity (86.4%) as established by necropsy diagnosis of dogs. The key component of the test, MAbEg9 has a convenient IgG isotype and reacts with a periodate-resistant epitope found in high molecular weight components of the worm. Time-course analysis of experimentally infected dogs showed that even animals with a very low number of parasites could be detected as early as day 20 post infection. The test was formulated in a ready-to-use kit format with proven stability of each component for a minimum of 3 months at room temperature. This characteristic facilitates its standardized use and shipping to other laboratories, which was demonstrated by the identical results obtained by two different laboratories in Peru and our own laboratory when a large number of field samples were analyzed independently in a blind fashion.

Cystic echinococcosis, caused by infection with the larval stage of the Echinococcus granulosus tapeworm, is a life-threatening zoonosis of worldwide distribution. The adult worm parasitizes the small intestine of dogs, which become infected after eating offal of an animal contaminated with the parasite, and releases eggs into the environment that can be accidentally ingested by domestic animals or humans, maintaining the life cycle of the parasite. Deworming of dogs is a major component of control programs, and simple and reliable methods are needed to monitor the base-line infection in the canine population. The lack of these tests was recognized as a major obstacle to the PAHO effort to control the disease in South America. This paper describes the development of a diagnostic assay that detects parasite antigens in dog feces. The key component is a monoclonal antibody carefully selected to attain high levels of sensitivity and specificity, which were established with a large panel of field fecal samples obtained from animals diagnosed by necropsy. Several aspects of the long-term stability of the test were optimized to facilitate its shelf-life and transference to other laboratories.

The development of a loop-mediated isothermal amplification method (LAMP) for Echinococcus granulosus [corrected] coprodetection

We have previously developed a polymerase chain reaction (PCR) assay for detection of Echinococcus granulosus infection, which proved very sensitive and specific for identification of infected dogs. We have now developed a loop-mediated isothermal amplification (LAMP) assay, which amplifies the same genomic repeated sequences of E. granulosus for coprodetection. This assay enabled detection of a single egg in fecal samples and showed high species specificity for E. granulosus with no cross-amplification of DNA from closely related helminths, including Echinococcus multilocularis. Because the method does not require thermocycling for DNA amplification, or electrophoresis for amplicon detection, it can potentially be used for premortem identification of E. granulosus-infected dogs to enable large-scale surveys in endemic countries where highly specialized equipment to undertake PCR analysis is rare.

Coprological survey of alimentary tract parasites in dogs from Zambia and evaluation of a coproantigen assay for canine echinococcosis

Faecal samples were collected from the rectum of 540 domestic dogs from four districts (Lusaka, Katete, Petauke and Luangwa) in Zambia between 2005 and 2006 and prevalences of canine alimentary tract parasites were determined by coprological examination. Thirteen different ova and parasites including strongyle (43.3%), Spirocerca lupi (18.7%), taeniid (13.1%), Toxocara canis (7.6%), Sarcocystis sp.* (7.5%), Isospora sp.* (5.7%), Physaloptera sp.* (4.6%), Capillaria sp.* (2.8%), Dipylidium caninum (2.2%), Mesocestoides sp.* (2.0%), Ascaris sp.* (1.7%), Trichuris vulpis* (0.4%) and Schistosoma mansoni* (0.4%) were detected, Ascaris and Schistosoma probably originating from coprophagy. The species with asterisks and later-described Taenia multiceps are for the first time reported from dogs in Zambia. A coproantigen enzyme-linked immunosorbent assay (CoproAg-ELISA) developed for Echinococcus spp. revealed 43 positive dogs and 37 of these harboured taeniid eggs. From 63 of the 71 taeniid egg-positive samples, eggs and DNA thereof were isolated and subjected to a multiplex polymerase chain reaction for differentiating E. granulosus sensu lato, E. multilocularis and Taenia spp. Amplicons indicative for Taenia spp. were obtained from 60 samples. Sequencing of amplicons spanning part of the mitochondrial cytochrome c oxidase subunit 1 gene, which was possible with 38 samples, revealed 35 infections with T. hydatigena and 3 with T. multiceps. Therefore, the CoproAg-ELISA showed some positives, but concrete evidence for the existence of canine E. granulosus infection could not be established. Comparison of the results of the CoproAg-ELISA and Taenia species identification indicated that the CoproAg-ELISA cross-reacts with patent infections of T. hydatigena (57%) and T. multiceps (33%).

Cysticercosis and echinococcosis

Cysticercosis and cystic echinococcosis are zoonotic parasitic diseases commonly transmitted by livestock animals. Past and future efforts to reduce transmission of these diseases adopt a One Health approach where control measures are implemented largely in the parasites' animal hosts in order to bring about, indirectly, a reduction in human disease. New and highly effective vaccines have been produced which are capable of preventing infections with Echinococcus granulosus (cystic echinococcosis) and Taenia solium (cysticercosis) in their animal intermediate hosts. Application of vaccines, together with taeniacides in the parasites' definitive hosts, provides new opportunities for control of these diseases and a reduction in the global burden of human cysticercosis and cystic echinococcosis.

A coproantigen diagnostic test for Strongyloides infection

Accurate diagnosis of infection with the parasite Strongyloides stercoralis is hampered by the low concentration of larvae in stool, rendering parasitological diagnosis insensitive. Even if the more sensitive agar plate culture method is used repeated stool sampling is necessary to achieve satisfactory sensitivity. In this manuscript we describe the development of a coproantigen ELISA for diagnosis of infection. Polyclonal rabbit antiserum was raised against Strongyloides ratti excretory/secretory (E/S) antigen and utilized to develop an antigen capture ELISA. The assay enabled detection of subpatent rodent S. ratti and human S. stercoralis infection. No cross-reactivity was observed with purified E/S from Schistosoma japonicum, the hookworms Ancylostoma caninum, A. ceylanicum, nor with fecal samples collected from rodents harboring Trichuris muris or S. mansoni infection. Strongyloides coproantigens that appear stable when frozen as formalin-extracted fecal supernatants stored at -20 °C remained positive up to 270 days of storage, whereas supernatants stored at 4 °C tested negative. These results indicate that diagnosis of human strongyloidiasis by detection of coproantigen is an approach worthy of further development.

Multiplex PCR system for identifying the carnivore origins of faeces for an epidemiological study on Echinococcus multilocularis in Hokkaido, Japan

A multiplex PCR system was developed to identify the carnivore origins of faeces collected in Hokkaido, Japan, for epidemiological studies on Echinococcus multilocularis. Primers were designed against the D-loop region of mitochondrial DNA. Two separate primer mixtures (mix 1, specific forward primers to fox, raccoon dog and dog, and a universal reverse primer [prH]; and mix 2, specific forward primers to cat, raccoon and weasels and prH) were used so that the PCR products (160 bp, fox and cat; 240 bp, raccoon dog and raccoon; and 330 bp, dog and weasel) were distinguished by size. The multiplex PCR exhibited no cross-reactivity between carnivore species and did not amplify DNA from rodent prey. When 270 field-collected faeces were examined, 250 showed single PCR products belonging to specific target sizes, suggesting successful carnivore identification for 92.6% of samples. Taeniid eggs were detected in 11.1% of samples and coproantigen in 30.4%; whereas the prevalences of taeniid eggs and coproantigen were 12.9% and 34.0% in fox faeces, and 0% and 26.3% in cat faeces, respectively. These results suggest that the prevalence in different target animals can be evaluated individually and precisely using multiplex PCR system.

Echinococcus multilocularis infection in pet dogs in Japan

A survey of Echinococcus multilocularis infections in pet dogs in Japan from 1997 to 2007 was conducted by testing for coproantigen reactivity, fecal taeniid eggs, and egg DNA. In Hokkaido, the only island where E. multilocularis is endemic in Japan, 18 of 4768 dogs (0.4%) excreted taeniid eggs that were positive for E. multilocularis DNA by polymerase chain reaction (PCR). Most of the dogs testing positive for egg DNA were kept free-range, but three dogs had been kept inside their owners' houses. In addition, 15 dogs were suspected to be infected based on the results of a coproantigen test. One dog, which was transported from Hokkaido to Honshu, the main island of Japan, was excreting taeniid eggs that were positive for E. multilocularis DNA by PCR. These results suggest the importance of proper pet management in disease prevention, even for dogs kept indoors, and they point out a possible means by which the parasite may be introduced into non-endemic areas through transport of infected dogs.

A modified coproantigen test used for surveillance of Echinococcus spp. in Tibetan dogs

Recently an immunological test for Echinococcus spp. antigens in dog faeces has been developed. The antigens appear to be carbohydrates, which survive proteolytic digestion and environmental degradation. For ELISA a capture antibody is used to capture the antigens, followed by a detection antibody. This paper describes a modification of the test whereby capture and detection antibodies are generated exclusively to the carbohydrate portion of the parasite tegument. Faecal extracts were heated to 70 degrees C overnight and the addition of foetal calf serum to the extracts was not necessary. The use of this modification as a surveillance tool in an extensive field trial of hydatid control in Western Sichuan is described. From 2003 onwards all dogs received a treatment with praziquantel pills in the spring and the autumn of each year. On each of six occasions 580 faecal samples were collected from 29 villages and analysed. Prevalence of Echinococcus spp. coproantigen-positive samples was 50% in year 2000, and decreased from 35% to 17% through 2003-2005. This coproantigen technique is now being used as part of the Chinese National Hydatid Disease Control Program, initially in 10 counties in Sichuan Province.

The immunodiagnosis of Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a severe zoonotic disease caused by the metacestode stage of Echinococcus multilocularis. The infection can have fatal consequences in humans if treatment is not provided, so early diagnosis is fundamental for initiating treatment and reducing morbidity and mortality. In addition, detection of the parasite in the definitive host plays a central role in epidemiological studies and surveillance programmes for control of AE. This review presents an overview of the present situation regarding the immunodiagnosis of E. multilocularis infection. Special attention is given to the description of the native, partially purified and recombinant antigens available currently for immunodiagnostic purposes. Recent advances in the primary serodiagnosis and follow-up of AE patients are highlighted, including the detection of specific cytokine profiles. Progress in the immunodiagnosis of intestinal E. multilocularis infection in definitive hosts, particularly the detection of excretory-secretory and integument products of the worm in faeces (copro-antigens) by ELISA, is also discussed.

Screening for Echinococcus granulosus in dogs: Comparison between arecoline purgation, coproELISA and coproPCR with necropsy in pre-patent infections

Echinococcus granulosus is an important zoonotic infection of dogs. The purpose of the present study assessed the performance of two laboratory diagnostic methods with arecoline purgation and necropsy in infected dogs. In total 65 dogs were successfully experimentally infected with protoscoleces of E. granulosus from ovine infection. At 14-34 days post-infection groups of dogs were purged with arecoline hydrobromide and then necropsied. Faecal samples were tested at weekly intervals by coproantigen ELISA and coproPCR. The necropsy infection rate with E. granulosus was 89.2 per cent. Only 43 per cent of dogs were successfully purged after one arecoline dose; this percentage increased to 76.9% for two doses of arecoline purgation. E. granulosus coproantigen was detected by coproELISA in 82.8% of faeces. The positive and negative predictive values for coproantigen ELISA were 96 and 44.4% respectively. E. granulosus DNA was detected in pre-patent faecal samples by coproPCR in 25.9% of dogs. These results indicate that coproELISA is more sensitive than arecoline purgation for the detection of pre-patent E. granulosus infection in dogs. CoproPCR detected E. granulosus DNA in dog faeces by 21 days post-infection before egg production.

Dog echinococcosis in northern Spain: comparison of coproantigen and serum antibody assays with coprological exam

A large sheep-dog population from the province of Alava (northern Spain) has been investigated in order to determine the prevalence of the cestode parasite Echinococcus granulosus. Worms were detected in 14.0% of 721 dog faecal supernatants by coproantigen ELISA, and in 9.1% of 754 dog serum samples by serum antibody ELISA. A weak but statistically significant correlation (Spearman's rho=0.103, 95% CI: 0.023-0.178) between the two immunoassay results was found. In addition, eggs of the family Taeniidae were detected in 10.3% of 726 faecal samples examined by coproparasitological (flotation and sedimentation) tests. The overall E. granulosus infection rate, based on a Bayesian latent class model that accounts for the imperfect sensitivities and specificities of all diagnostic tests used, was estimated to be 8.0% (95% credible interval: 5.4-11.4%), corroborating that sheep-dog is the dog class most vulnerable to acquiring the infection. Dog sex did not influence the prevalence of E. granulosus, independently of the diagnostic test used or the dog region of origin. No significant linear correlation was found between the coproantigen ELISA OD values and the dog age (Spearman's rho=-0.049, 95% CI: -0.234 to 0.135), suggesting that there were no differences in prevalence of E. granulosus between old and young dogs. The obtained results highlight the importance of initiating a control program based on regular treatment of the sheep-dogs with praziquantel in the province of Alava.

Antigens for the immunodiagnosis of Echinococcus granulosus infection: An update

The taeniid tapeworm Echinococcus granulosus is the causative agent of the echinococcal disease, an important zoonosis with worldwide distribution. Accurate immunodiagnosis of the infection requires highly specific and sensitive antigens to be used in immunodiagnostic assays. The choice of an appropriate source of antigenic material is a crucial point in the improvement of the diagnostic features of tests, and must be based on the developmental stage of the parasite and the host. The most common antigenic sources used for the immunodiagnosis of echinococcal disease are hydatid cyst fluid, somatic extracts and excretory-secretory products from protoscoleces or adults of E. granulosus. Hydatid cyst fluid is the antigenic source of reference for immunodiagnosis of human hydatidosis, which is mainly based on the detection of antigens B and 5. Somatic extracts have been widely used in the serodiagnosis for E. granulosus infection in dogs and ruminant intermediate hosts, although in the last few years the detection of excretory-secretory products of the worm in faeces (coproantigens) have become the most reliable method for the detection of the parasite in the definitive host. This review emphasizes recent advances in the identification and characterization of novel antigens with potential for the immunodiagnosis of echinococcal disease. Progress in recombinant technologies and synthetic peptides are also discussed. The paper highlights the need to search for new antigenic components with high diagnostic sensitivity and specificity, a fact that remains a crucial task in the improvement of the immunodiagnosis of the disease.

Coproantigens in taeniasis and echinococcosis

The application of modern immunodiagnostic or molecular diagnostic techniques has improved the diagnosis of the taeniid cestode infections, echinococcosis and taeniasis. One particularly promising approach is the detection of parasite-specific antigens in faeces (coproantigens). This approach has been applied to both Echinoccocus and Taenia species and it has gained increasingly widespread use. Taeniid coproantigen tests are based on either monoclonal or polyclonal antibodies raised against adult tapeworm antigens. These tests have the following common characteristics; they are largely genus-specific, specificity is high (>95%), parasite antigen can be detected in faeces weeks prior to patency, levels of coproantigen are independent of egg output, coproantigen is stable for days at a range of temperatures (-80 degrees C to 35 degrees C), for several months in formalin-fixed faecal samples, and coproantigen levels drop rapidly (1-5 days) following successful treatment. In the genus Taenia, most work has been done on Taenia solium and coproantigen tests have reliably detected many more tapeworm carriers than microscopy. For Echinococcus species, there is a broad positive correlation between test sensitivity and worm burden with a reliable threshold level for the test of >50 worms. Characterisation of taeniid coproantigens in order to further improve the tests is ongoing. Studies indicate taeniid coproantigens to include high molecular weight (>150 kDa), heavily glycosylated molecules with carbohydrate moieties contributing substantially to the levels of antigen detected in faeces. Application of the existing coproantigen tests in epidemiological and control programmes for Echinococcus and Taenia species infection has begun to contribute to an improved understanding of transmission and of surveillance of these important zoonotic cestodes.

Double-antibody sandwich ELISA using biotinylated antibodies for the detection of Echinococcus granulosus coproantigens in dogs

Here we present the diagnostic evaluation of an improved double-antibody sandwich ELISA for detecting Echinococcus granulosus antigens in dog faecal samples (coproantigens). A purified rabbit IgG fraction against protoscolex excretory-secretory products was used as primary antibody, and the same fraction conjugated with biotin as secondary antibody. In order to validate the sandwich ELISA, intra- and inter-assay precision, linearity, and recovery percentages were calculated. The diagnostic evaluation of the method was carried out by investigating faecal samples from 37 dogs naturally infected with E. granulosus, 15 Echinococcus-free dogs infected with Taenia spp., 82 dogs with non-taeniid helminths and 66 dogs free of helminth infections. An overall sensitivity of 78.4% and specificity of 93.3% were determined. Positive and negative predictive values were 72 and 95%, respectively, and the diagnostic efficiency was 90.5%. In addition, the sandwich ELISA detection limit was estimated in 5.12 ng ml(-1). These results are highly satisfactory, allowing the use of this methodology in surveillance and control programs for intestinal echinococcosis in dogs.

Production and characterization of monoclonal antibodies against excretory/secretory products of adult Echinococcus granulosus, and their application to coproantigen detection

Two IgM murine monoclonal antibodies (MAbs), EgC1 and EgC3, were produced against the excretory/secretory (E/S) products of Echinococcus granulosus adult worms. Immunoblotting revealed that both predominantly recognized a 50 kDa antigen in the somatic extract and an 85 kDa component in the E/S products. Immunolocalization showed that both MAbs reacted with the tegument of the parasite, and additionally EgC3 reacted with parenchyma and the tegument lining the external surface of the reproductive organs. A coproantigen capture ELISA was developed using a rabbit polyclonal antibody against E/S products from adult tapeworms as catching antibodies, and each one of MAbs as detecting antibody. The assays detected seven out of eight (EgC1), and eight out of eight (EgC3) experimentally infected dogs (worm burdens ranging from 61 to 57,500), using heat-treated samples obtained at prepatent period, and none (n=8) of helminth-free samples. Time course analysis showed that, after a 12-25 days lag, coproantigen levels rose above cut off O.D. values and typically peaked around 30 days post-infection (DPI) at the end of the experiment. One dog experimentally infected with Taenia hydatigena metacestodes was slightly detected as positive at different time points after 30 DPI. Both MAbs showed a similar pattern of recognition, but T. hydatigena antigens were undetectable for a longer period, and reached lower O.D. values with EgC1. Interestingly, fecal samples from two experimentally infected dogs with Echinococcus multilocularis were not recognized by the EgC1 assay, suggesting a potential value as species-specific diagnostic tool.

Anoplocephala perfoliata coproantigen detection: a preliminary study

Anoplocephala perfoliata has a prevalence as high as 60% in some geographical areas and has been associated with increased risk for serious conditions in the horse including bowel irritation, ileal impaction, and spasmodic colic. Identification of infected animals based upon detection of eggs in feces is labor intensive and unreliable. This study involved the development of a test for A.perfoliata coproantigen using an antigen capture enzyme linked immunosorbent assay (ELISA) and correctly distinguished between infected and uninfected animals in a trial with a small sample size.

Echinococcosis in southern Brazil: efforts toward implementation of a control program in Santana do Livramento, Rio Grande do Sul

This investigation aimed to design a strategy for echinococcosis control in Santana do Livramento county, an endemic area in state of Rio Grande do Sul (Brazil). Fecal samples from 65 dogs were obtained from urban, suburban and rural areas. Purging with Arecoline Bromhidrate (AB) was done to visualize Echinococcus granulosus, and Enzyme Linked Immunosorbent Assay (ELISA) was performed to detect parasite coproantigen. Samples were obtained at the beginning and at the end of treatment with Praziquantel. A third fecal sampling was also done in rural areas four months after the end of treatment. Each dog was treated immediately after the first purging and every 30 days for eight months. In urban and suburban areas no infected dogs were found. In rural areas, first evaluation showed 11.36% and 27.69% of infected dogs by AB and ELISA, respectively. No infected dogs were diagnosed in the second evaluation and in the third evaluation 36.84% and 47.37% infected dogs were identified by AB and ELISA, respectively. Medication program to combat dog infection resulted in successful interruption of parasite transmission, but the project failed to create awareness of the need for dog prophylaxis among rural populations as well as to establish a permanent control program in this municipality.

Polymerase chain reaction for detection of patent infections of Echinococcus granulosus (“sheep strain”) in naturally infected dogs

Polymerase chain reaction (PCR) for the identification of eggs of the tapeworm Echinococcus granulosus ("sheep strain") was evaluated with primers derived from mitochondrial sequences. Specificity of these primers was confirmed by investigating DNA of other strains of E. granulosus and of 14 helminth species which inhabit the intestines of dogs. This PCR assay was used to investigate 131 purged dogs from Kazakhstan. Eighteen dogs harboured Echinococcus worms, ten of them in mixed infections with Taenia spp. Coproantigen detection was positive in 15 and taeniid eggs could be recovered from 13 of these specimens. Eight of the egg-containing samples were positive in the PCR for E. granulosus and four in a Echinococcus multilocularis -specific PCR revealing one mixed infection. Egg-containing faeces from two dogs harbouring both Taenia spp. and Echinococcus spp. were negative in both PCRs. The combination of egg isolation and PCR will also be of value in epidemiological studies when investigating environmental samples.

Mucin-type O-glycosylation in helminth parasites from major taxonomic groups: evidence for widespread distribution of the Tn antigen (GalNAc-Ser/Thr) and identification of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase activity

This article focuses on the initiation pathway of mucin-type O-glycosylation in helminth parasites. The presence of the GalNAc-O-Ser/Thr structure, also known as Tn antigen, a truncated determinant related to aberrant glycosylation in mammal cells, and the activity of the UDP-GalNAc:polypeptide N-acetyl-galactosaminyltransferase (ppGaNTase), the enzyme responsible for its synthesis, were studied in species from major taxonomic groups. Tn reactivity was determined in extracts from Taenia hydatigena, Mesocestoides corti, Fasciola hepatica, Nippostrongylus brasiliensis, and Toxocara canis using the monoclonal antibody 83D4. The Tn determinant was revealed in all preparations, and multiple patterns of Tn-bearing glycoproteins were observed by immunoblotting. Additionally, the first evidence that helminth parasites express ppGaNTase activity was obtained. This enzyme was studied in extracts from Echinococcus granulosus, F. hepatica, and T. canis by measuring the incorporation of UDP-(3H)GalNAc to both deglycosylated ovine syalomucin (dOSM) and synthetic peptide sequences derived from tandem repeats of human mucins. Whereas significant levels of ppGaNTase activity were detected in all the extracts when dOSM was used as a multisite acceptor, it was only observed in F. hepatica and E. granulosus extracts when mucin-derived peptides were used, suggesting that T. canis ppGaNTase enzyme(s) may represent a member of the gene family with a more restricted specificity for worm O-glycosylation motifs. The widespread expression of Tn antigen, capable of evoking both humoral and cellular immunity, strongly suggests that simple mucin-type O-glycosylation does not constitute an aberrant phenomenon in helminth parasites.

Echinococcosis--an international public health challenge

This review aims to summarise some of the recent studies that have been undertaken on parasites of the genus Echinococcus and the diseases which they cause. Although the adult parasite, which inhabits the intestine of various carnivore species is not pathogenic, the larval or metacestode stages can be highly pathogenic, causing economic losses to livestock and various forms of echinococcosis in humans, some of which have a high fatality rate. There is growing evidence that there are at least 5 species of Echinococcus rather than the generally accepted 4 species. Within these species there are a number of genotypes or strains. This can have implications for surveillance and control. In some wealthy countries, cystic echinococcosis caused by Echinococcus granulosus has been successfully controlled or indeed eradicated. However, in most parts of the world it remains a serious threat to human health. In the former Soviet Union, the disease has rapidly increased in incidence after the end of communist administration. Human alveolar echinococcosis, caused by Echinococcus multilocularis, is more sporadic. However, in some Chinese communities there is a disturbingly high human prevalence and in Europe there has been an increase in the detection rate of E. multilocularis in animals in the last 10 years. Echinococcosis can present diagnostic challenges, particularly in the definitive host in areas of low endemicity. Much of the recent work relating to the use of coproantigen and PCR to overcome these difficulties is summarized. New ideas for controlling the parasite are becoming available and these include both the use of vaccination and the application of mathematical models to determine the most cost effective means of control. Effective measures that are affordable are vital if the parasite is to be controlled in poor countries.

Characterization of carbohydrates of adult Echinococcus granulosus by lectin-binding analysis

The identification of lectin-binding structures in adult worms of Echinococcus granulosus was carried out by lectin fluorescence; the distribution of carbohydrates in parasite glycoconjugates was also studied by lectin blotting. The lectins with the most ample recognition pattern were ConA, WGA, and PNA. ConA showed widespread reactivity in tegument and parenchyma components, including the reproductive system, suggesting that mannose is a highly expressed component of the adult glycans. Although reproductive structures appeared to be rich in N-acetyl-D-glucosamine (GlcNAc)-N-acetyl neuraminic acid (NeuAc) and galactose (Gal) as demonstrated by their strong reactivity with WGA and PNA, respectively, some differences were observed in their labeling patterns. This was very clear in the case of the vagina, which only reacted with WGA. Furthermore, WGA and ConA both had reactivity with the excretory canals. RCA, the other Gal binding lectin used, only reacted with the tegument, suggesting that widespread PNA reactivity with the reproductive system is related to the presence of the D-Gal-beta-(1,3)D-GalNAc terminal structure. UEA I failed to bind to any parasite tissues as determined by lectin fluorescence, whereas DBA and SBA showed a very faint staining of the tegument. However, in transferred glycans, N-acetyl-D-galactosamine (GalNAc) and fucose (Fuc) containing glycoproteins were distinctly detected.

Screening of dogs for Echinococcus granulosus coproantigen in a low endemic situation in Cyprus

In the framework of an echinococcosis surveillance and control programme in Cyprus, a commercial enzyme-linked immunosorbent assay (ELISA) (CHEKIT ECHINOTEST) designed for the detection of Echinococcus granulosus and E. multilocularis coproantigens was used in 1997-2000 for the investigation of large numbers of dogs. Most of the animals originated from areas where approximately 0.2% of the dogs had been found to be infected with E. granulosus in previous (1993-1996) arecoline surveys. The sensitivity of the coproantigen test was 83%, as determined in 35 dogs naturally infected with this cestode species. The specificity was 98% in 97 randomly selected dogs from Cyprus, but it was reduced to 80% in a group of 50 dogs, infected with Taenia spp. A total of 6551 dogs (mainly of rural origin) was examined, including three large groups (N: 2928, 1761 and 1800) from the Government Control Area (GCA) in southern Cyprus and a small group (N: 62) from the Non-Government Control Area (NonGCA) in the northern part of the island. Among the dogs from the GCA, 184 (2.8%) tested positive for coproantigen; coproantigen prevalences were 2.6, 4.9 and 1.1% in these three groups, and of 62 dogs from the NonGCA 8.1% were positive. The calculated true prevalences of E. granulosus in the dog population of the GCA ranged between 0.0 and 3.58%. The predictive values of the test, based on a 0.2% prevalence, was >99.9% for negative results, but very low (7%) for coproantigen-positive results. However, the relatively small number of coproantigen-positive dogs can be treated with praziquantel or the results can further be confirmed by arecoline purging.

Assessment of the epidemiological status of Echinococcus multilocularis in foxes in France using ELISA coprotests on fox faeces collected in the field

The aim of this study was to estimate the relevance of Echinococcus multilocularis coproantigen detection in fox faeces collected in the field to identify different levels of endemicity for Echinococcus multilocularis on a large scale (n x 10 km(2)). Six study sites were selected in a high endemicity area and two study sites in a low endemicity area in eastern France on the basis of landscape composition. Sampling was undertaken in the winters of 1996-97, 1997-98 and 1998-99. At each site, (i) necropsy and intestine examination was undertaken on a sample of shot foxes (total number of foxes, 222), and (ii) fox faeces were collected in the field along road verges, and scored for degradation status (total number of faeces, 625). Fox faeces were also sampled in a control area (n=30) in western France in the summer of 1998. Intestines were examined according to the sedimentation method. Echinococcus multilocularis coproantigens were detected by using two ELISA tests: EM-ELISA and EmA9-ELISA. The necropsy prevalence in high and low endemicity areas was 63.3% and 19.4%, respectively, and the distribution of adult worms in the fox population was highly overdispersed (75.5% of the total biomass was harboured by 11.6% of foxes). Using the two ELISA tests, there was no difference in the detection of E. multilocularis coproantigens in field faeces, regardless of the degradation status. The medians of EM- and EmA9-ELISA OD values of field faeces in high endemicity area were significantly higher than in low endemicity area (P<0.001 for both ELISA). The distribution of EM-ELISA OD values in low endemicity area was significantly higher (P=0.002) than in the control area. Moreover, for the two ELISA, the observed ELISA OD value distributions in high endemicity area, low endemicity area and control area seemed representative of the distribution of adult worms in fox populations. These results indicate that E. multilocularis coproantigen detection in field faeces could serve for large-scale surveillance, as an alternative to necropsy.

Development of a copro-antigen capture ELISA for detecting Ostertagia ostertagi infections in cattle

The present study reports on the development of a copro-antigen capture ELISA for detecting Ostertagia ostertagi infections in cattle. The ELISA was based on polyclonal rabbit antibodies, which recognize O. ostertagi excretory/secretory antigens (ES). ES antigens are released by the metabolic active stages of the parasite in the abomasum, and passed in the faeces of the host. The detection limit of pure ES material was 30 ng ml(-1) in sample buffer and 125 ng ml(-1) in faecal extract. The test was evaluated using a follow up from six artificially infected calves. Elevated levels of Ostertagia coproantigens could be measured from 21 days after infection, indicating that only the presence of adult parasites can be detected. To evaluate the capacity of the assay to measure levels of infection, three groups of cattle were tested: 38 artificially infected calves, 17 naturally infected first grazing season calves and 16 naturally infected adult dairy cows. Optical densities were significantly correlated to the worm burdens of the animals and the ELISA had an overall sensitivity of 91% and a specificity of 45%. The test gave negative readings for faeces of animals carrying patent mono-infections with Cooperia oncophora.

O-glycosylation in Echinococcus granulosus: identification and characterization of the carcinoma-associated Tn antigen

In the present work we demonstrate that the cancer-associated O-glycosylated Tn antigen (GalNAc-O-Ser/Thr) is expressed by the cestode Echinococcus granulosus. This antigen was detected in both larval and adult worm extracts, with the highest specific activity observed in the adult excretion/secretion preparation. Histochemical analysis showed that Tn is preferentially expressed in the parenchyma in both parasite stages and the external part of tegument in adult worms. A similar pattern was observed for sialyl-Tn, a related O-linked antigen. Tn glycoproteins from protoscoleces were resolved by SDS-PAGE in two main components of 43 and 49 kDa. After purification, this material was reactive with lectins which bind GlcNAc/sialic acid, GalNAc, and T antigen. In a preliminary evaluation, high levels of Tn antigen were detected in serum samples from patients with hydatid cyst, suggesting that the measure of Tn in serum could be a biomarker of this disease, although extensive work is necessary in order to determine the clinical usefulness of this assay. The results reported here, the first evidence of O-glycosylation pathways in E. granulosus and the presence of Tn antigen in cestodes, suggest that the evaluation of O-glycosylated antigens might give new insights in the host-parasite relationship.

The 14-3-3 protein is secreted by the adult worm of Echinococcus granulosus

The 14-3-3 protein, already described in the metacestode of Echinococcus multilocularis, has been characterized in the Echinococcus granulosus adult worm. Immunolocalization studies show the presence of the 14-3-3 protein in the periphery of testes and externally associated with the apical rostellum and adjacent worm tegument. The alcian blue staining in consecutive parasite sections gave similar reactivity patterns, suggesting that the 14-3-3 protein is produced and secreted by rostellar glands. Immunoblot analysis showed the presence of the 14-3-3 protein in somatic and excretory-secretory worm products with higher and smaller apparent molecular masses, respectively, than those detected in E. multilocularis or E. granulosus metacestode tissues. Conversely, the 14-3-3 protein was not detected in metacestode secretory products. Detection of anti-E. granulosus 14-3-3 reactivity in sera of experimentally infected dogs was achieved at early stages of infection. Specific antibody titres decreased during the course of infection. The possible origin and functions of the 14-3-3 protein produced by the adult worm are discussed.

Development and sexual maturation of Echinococcus vogeli in an alternative definitive host, Mongolian gerbil (Meriones unguiculatus)

An alternative definitive host model for Echinococcus vogeli was developed using Mongolian gerbils. The animals treated with prednisolone tert-butylacetate were orally inoculated with protoscoleces of E. vogeli and the development of worms in the small intestine was observed until 50 days post infection (DPI). The parasites were recovered most frequently from the anterior part of the small intestine. The band formation (the sign of proglottisation) of the worm was observed at 7 DPI, the second proglottid and tests formation at 14 DPI, spermatozoa in seminal receptacle and cleavage of ova in uterus at 21 DPI, the hook formation of oncospheres at 28 DPI and the embryophore formation at 34 DPI. Eggs in the feces were first detected at 35 DPI. The coproantigen detection method developed for E. multilocularis could detect the E. vogeli coproantigen early in the infection, at 7 DPI during the prepatent period. Therefore, this technique could be used for the diagnosis of E. vogeli, replacing ordinary fecal egg examination.

Detection of Echinococcus granulosus coproantigens in Australian canids with natural or experimental infection

Coproparasitological and purging methods for diagnosing canids infected with the intestinal helminth Echinococcus granulosus, an important zoonotic parasite, are unreliable. Detection of coproantigens in feces of infected dogs by enzyme-linked immunosorbent assay (ELISA) is suitable for detecting patent and prepatent infections with a high degree of sensitivity and specificity. In the present study, natural and experimental infections in domestic and wild Australian canids were investigated using a coproantigen capture ELISA. Experimental infection of dogs with E. granulosus was detected at between 14 and 22 days postinfection (PI), and optical density (OD) values remained high until termination of experiments 35 days PI. After chemotherapy, coproantigen levels in infected dogs dropped rapidly, becoming negative 2-4 days after treatment. In experimentally infected red foxes (Vulpes vulpes), the coproantigen excretion profile was different, with ELISA OD levels peaking 15-17 days PI, then falling to low or undetectable levels by 30 days PI. Coproantigens were detected in the feces of naturally infected Australian wild dogs (dingoes, dingo/domestic dog hybrids) with infection levels ranging between 2 worms and 42,600. Preliminary data on the stability of coproantigen in dog feces exposed to environmental conditions indicated that there was no change in antigenicity over 6 days. The results suggest the coproantigen ELISA could be successfully used to monitor E. granulosus prevalence rates in Australian domestic dogs, foxes, and wild dogs.