Coproantigens in taeniasis and echinococcosis
Section snippets
Parasitological diagnosis of taeniid cestodes
Broadly speaking the definitive host range for the zoonotic taeniid species is more restricted than the intermediate host range of the same parasite. For example, humans represent the sole natural definitive host for both Taenia solium and Taenia saginata. This therefore leaves these two species theoretically susceptible to interventions designed at reducing the rate of humans carrying the intestinal stage. Thus, from a control perspective, the diagnosis of the adult stages of these parasites
Alternatives to parasitological diagnosis
The application of alternative means to the diagnosis of these cestodes is not new. Immunodiagnosis of intestinal Taenia was first attempted in the early years of the 20th century and a number of immunological and latterly molecular approaches have been applied to the diagnosis of intestinal stages of both Echinococcus and Taenia in the intervening years [4], [5]. One of these approaches will be reviewed here.
Coproantigen-based diagnosis
The diagnosis of intestinal infections by detection of pathogen-/parasite-specific antigens in faeces (coproantigens) is an approach now widely applied to a broad range of infectious organisms. If these organisms release products of metabolism into the intestine, these should be amenable to immunological detection. Theoretically, if these antigens are not directly associated with parasite reproduction, they should be present when reproductive material (like taeniid eggs) is absent from the
Time course infection
Babos and Nemeth [6] first showed antigen to be present in the faeces of E. granulosus-infected dogs prior to the onset of egg production. Follow-up on work with taeniid cestodes in time course infections demonstrated that antigen is present in the faeces of Taenia hydatigena-, Taenia pisiformis- and E. granulosus-infected dogs before patency, apparently reaching a plateau several weeks before onset of egg production and is independent of egg output thereafter [10], [13], [19], [28]. Where
Sensitivity/Worm burden determination
Of the Taenia species infecting humans, most coproantigen application has been carried out on T. solium. These studies have utilised either a microplate format ELISA test [9] or a dipstick format test [11]. Several studies involving follow-up on coproantigen positive results to determine firstly whether the diagnostic result could be parasitologically confirmed, and secondly the species of tapeworm involved have indicated that coproantigen testing by microplate ELISA detects over twice as many
Specificity
Despite most of the described tests being based on polyclonal antibodies raised to relatively crude adult worm derived antigens, coproantigen tests for taeniid species have proved remarkably specific. Tests raised using antibodies to Taenia species provide genus-specific results: polyclonal rabbit sera raised against T. saginata, T. solium, or T. hydatigena have, for example, proved capable of detecting antigens in faeces of hosts harbouring Taenia genus infections but are negative when tested
Coproantigen stability
Taenia or Echinococcus coproantigens have been shown to be very stable, being capable of detection in faecal samples stored at room temperature (20 °C) over several days [13]. Samples can be also be reliably stored in 5% or 10% formalin solution for several months [10], [15]. This considerably simplifies sample collection and storage, particularly under field conditions. It should be noted however that coproantigens are not detectable in faeces treated with organic solvents, and are not
Field applicability/epidemiological studies
Since first being described, taeniid coproantigen tests have generated useful data through their application in epidemiological studies on the important zoonotic species. Some of the aspects discussed above should be taken into account when applying such tests. Nonetheless, our understanding of the epidemiology of the intestinal stages of T. solium, E. granulosus and E. multilocularis has benefited from the application of coproantigen tests. Some specific examples are provided here:
Antigen characterisation
The existing coproantigens tests, whilst useful, are still not optimized in all respects. Issues remain with both sensitivity and specificity, and a reasonable level of laboratory infrastructure is needed to use most of the test formats developed to date. Ideally, improved tests could be capable for example of differentiating the human Taenia species, providing reliable estimate of intestinal Echinococcus burden and/or being easier to apply with minimal laboratory infrastructure.
In this regard,
Acknowledgements
The Cestode Zoonoses Research Group is grateful for funding support from the Wellcome Trust, European Commission, NIH/NSF and British Council.
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The potential role of roaming dogs in establishing a geographically novel life cycle of taeniids (Echinococcus spp. and Taenia spp.) in a non-endemic area
2023, Veterinary Parasitology: Regional Studies and ReportsA copro-antigen ELISA for the detection of ascarid infections in chickens
2022, Veterinary ParasitologyCitation Excerpt :Hence, a non-invasive alternative to FEC that can capture all groups of birds and different developmental stages of worms is still missing. An ELISA that quantifies the concentration of parasite antigens in hosts’ faeces (copro-antigens) is a non-invasive method that could also be used for evaluating the infection status of the living host given the presence of excretory/secretory products of parasites in the host intestine (Allan & Craig, 2006). Copro-antigens have been used in the evaluation of parasitic infections with considerably higher accuracy than FEC in cattle, sheep, pigs, red deer, horses, and dogs (Palmer et al., 2014; Kajugu et al., 2015; French et al., 2016; Martínez-Sernández et al., 2016; Lagatie et al., 2020), but its’ performance in diagnosing chickens infected with either A. galli or H. gallinarum has not been reported.
Tapeworms
2022, Greene's Infectious Diseases of the Dog and Cat, Fifth EditionEchinococcosis in humans and animals in Southern Africa Development Community countries: A systematic review
2020, Food and Waterborne ParasitologyDiagnosis of Taeniosis in rural Venezuelan communities: Preliminary characterization of a Taenia solium specific monoclonal (VP-1) Coproantigen ELISA
2020, Acta TropicaCitation Excerpt :Interestingly, the two samples from patients that had Taenia spp eggs in their faeces and delivered T. solium adults on purging, had low optical densities in the polyclonal CoproAg ELISA. Diagnosis of intestinal parasites through detection of coproantigens has been intensively pursued with assays developed for Giardia (Vinayak et al., 1991), Entamoeba (Randall et al., 1984), Strongyloides (Nageswaran et al., 1994), Hymenolepis (Allan and Craig, 1989) and the taenidae Taenia and Echinococcus (Allan and Craig, 2006). Thus, the introduction of the coproAg test to detect human T. solium infections (Allan et al., 1990; Deplazes et al., 1991; Allan et al., 1992, ; Allan et al., 1996a; Allan et al., 1996b; Allan et al., 2003; Guezala et al., 2009) provided a similar rational strategy for the control of human taeniosis.