A fluorescence-based polymerase chain reaction-linked single-strand conformation polymorphism (F-PCR-SSCP) assay for the identification of Fasciola spp

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In the present chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Fasciola hepatica and Fasciola gigantica coexistence in domestic ruminants in Nigeria: application of a PCR-based tool

The distinction between Fasciola hepatica and Fasciola gigantica has been traditionally based on morphological criteria, although accurate recognition of the two flukes is usually difficult because of substantial variations in morphological features. The main aim of this study was to develop a PCR-based assay for discrimination between both species collected in sheep and cattle from Nigeria. A total of 47 animals, 33 cattle and 14 sheep, were sampled, and a single adult fluke was collected from each animal. DNA was extracted from flukes, and primers were designed based on mitochondrial DNA sequences to amplify a 304 bp fragment for the identification of F. hepatica and 752 bp for F. gigantica. PCR products from 12 flukes were sequenced for phylogenetic analysis. A total of 29 out of 47 flukes were identified as F. hepatica and 18 as F. gigantica. Within each host, the percentage of each fluke species was as follows: In cattle, 18/33 (54.5%) and 15/33 (45.5%) were F. hepatica and F. gigantica, respectively. In sheep, 11/14 (78.6%) were F. hepatica and 3/14 F. gigantica (21.4%). The phylogenetic analysis confirmed these results. Although the number of flukes collected in sheep was limited, it seems that F. hepatica is more prevalent in sheep than F. gigantica, whereas the percentage of each species was similar in cattle. This study confirms the presence of F. hepatica in Nigeria.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Techniques for the diagnosis of Fasciola infections in animals: room for improvement

The common liver fluke, Fasciola hepatica, causes fascioliasis, a significant disease in mammals, including livestock, wildlife and humans, with a major socioeconomic impact worldwide. In spite of its impact, and some advances towards the development of vaccines and new therapeutic agents, limited attention has been paid to the need for practical and reliable methods for the diagnosis of infection or disease. Accurate diagnosis is central to effective control, particularly given an emerging problem with drug resistance in F. hepatica. Traditional coprological techniques have been widely used, but are often unreliable. Although there have been some advances in establishing immunologic techniques, these tools can suffer from a lack of diagnostic specificity and/or sensitivity. Nonetheless, antigen detection tests seem to have considerable potential, but have not yet been adequately evaluated in the field. Moreover, advanced nucleic acid-based methods appear to offer the most promise for the diagnosis of current infection. This chapter (i) provides a brief account of the biology and significance of F. hepatica/fascioliasis, (ii) describes key techniques currently in use, (iii) compares their advantages/disadvantages and (iv) reviews polymerase chain reaction-based methods for specific diagnosis and/or the genetic characterization of Fasciola species.

Authentication of official Da-huang by sequencing and multiplex allele-specific PCR of a short maturase K gene

Rhubarb (official Da-huang) is an important medicinal herb in Asia. Many adulterants of official Da-huang have been discovered in Chinese markets in recent years, which has resulted in adverse effects in medicinal treatment. Here, novel molecular markers based on a short maturase K (matK) gene were developed for authenticating official Da-huang. This study showed that all the species from official Da-huang were clustered together in one clade in the polygenetic trees based on short matK. Two highly conserved single nucleotide polymorphisms of short matK were mined in the species from official Da-huang. Based on these polymophisms, four improved specific primers of official Da-huang were successfully developed that generated reproducible specific bands. These results suggest that the short matK sequence can be considered as a favorable candidate for distinguishing official Da-huang from its adulterants. The established multiplex allele-specific PCR was determined to be simple and accurate and may serve as a preferable tool for authentication of official Da-huang. In addition, we suggest that short-sized specific bands be developed to authenticate materials used in traditional Chinese medicine.

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.

Genetic characterization, species differentiation and detection of Fasciola spp. by molecular approaches

Liver flukes belonging to the genus Fasciola are among the causes of foodborne diseases of parasitic etiology. These parasites cause significant public health problems and substantial economic losses to the livestock industry. Therefore, it is important to definitively characterize the Fasciola species. Current phenotypic techniques fail to reflect the full extent of the diversity of Fasciola spp. In this respect, the use of molecular techniques to identify and differentiate Fasciola spp. offer considerable advantages. The advent of a variety of molecular genetic techniques also provides a powerful method to elucidate many aspects of Fasciola biology, epidemiology, and genetics. However, the discriminatory power of these molecular methods varies, as does the speed and ease of performance and cost. There is a need for the development of new methods to identify the mechanisms underpinning the origin and maintenance of genetic variation within and among Fasciola populations. The increasing application of the current and new methods will yield a much improved understanding of Fasciola epidemiology and evolution as well as more effective means of parasite control. Herein, we provide an overview of the molecular techniques that are being used for the genetic characterization, detection and genotyping of Fasciola spp..