The detection and quantification of a digenean infection in the snail host with special emphasis on Fasciola sp.

Abstract

In this review, ten methods used to study digenean infections in their intermediate hosts were compared to determine which one should be used either in the field or in the lab to establish the prevalence and intensity of infections in snails. Snail crushing and snail dissection allow quick establishing of prevalence in natural or experimental infections, whereas histology is considered as the most accurate approach to assess the intensity of infection. The follow-up of cercarial shedding only gave an idea on cercarial production. Among recently developed techniques, polymerase chain reaction (PCR) brings the most accurate information and shows high sensitivity and specificity levels when compared to blotting techniques. The easiness and relatively low cost of the basic PCR protocol make it interesting to investigate the epidemiology of the liver fluke in a lab with limited financial resources. Nevertheless, if this technique allows a relatively good estimation of the prevalence, information concerning the intensity of infection is best obtained through real time PCR. However, at the time being this technique is too expensive to be used routinely in the field. The choice between classical or new techniques is usually based on a compromise, as each technique has its advantages and drawbacks.

Molecular confirmation of trematodes in the snail intermediate hosts from Ratchaburi Province, Thailand

“…Freshwater snails were crushed by crushing method [27] and identified by cercarial type under a high magnification stereomicroscope. The prevalence value was then calculated.…”

Seasonal Transmission of Opisthorchis viverrini sensu lato and a Lecithodendriid Trematode Species in Bithynia siamensis goniomphalos Snails in Northeast Thailand

“…The snails infected with other trematodes or mixed infections with other types of cercariae (0.08%) were not included. Group 1 were trematode-free snails (uninfected controls) as confirmed by the crushing method 22 and microscopy. Group 2 snails were infected with O. viverrini s.l.…”

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 number of diagnostic tools have been developed for single or simultaneous detection/discrimination of F. hepatica and F. gigantica, including morphological (using shape and size and morphometric features), immunodiagnostic (using monoclonal antibodies or copro-antigen (extracted from eggs in feces) and metacercarial/Fasciola-specific antigens for ELISA) and DNA-related loop-mediated isothermal amplification (LAMP), PCR (single or multiplex), restriction enzymatic, and sequencing methods (2,3,5,11,12,13,35). All the diagnostic methods developed so far have contributed to fast, accurate, and specific detection of Fasciola spp.…”

“…Antibody detection tests are useful for determining seroprevalence in epidemiological studies but are not necessarily good indicators of active infection (44). A review (11) suggested that the most accurate, sensitive, and specific information could be determined easily and with low costs, making DNA-based tools available to investigate the epidemiology of the liver fluke in a laboratory with limited financial resources (11).…”

“…It is capable of distinguishing eggs of Fasciola species from those of other trematodes, and it also distinguishes between Fasciola species. The eggs shed in feces, normally persisting for a long period, can provide an easily accessed source of a DNA template for specific amplification, presenting a DNA multidisciplinary use for detection of contaminated trematodes and other intestinal parasites (11,39). The presence of eggs in feces also can be evidence for the existence of live flukes in the host.…”