Isolation of fraction no. 10 from Taenia saginata and evaluation of its specificity for the diagnosis of bovine cysticercosis

In an attempt to prove the specificity of the crude Taenia saginata antigen for the immunodiagnosis of bovine cysticercosis, a major and highly immunogenic fraction (F10), responsible for the formation of the typical "long band" reaction in immunoelectrophoresis, has been isolated from T. saginata proglottides by immunoaffinity chromatography. The immunoabsorbent was prepared by coupling a specifically raised hyperimmune serum (HIS) anti-F10 to Sepharose 4B. The purity of the isolated F10 was demonstrated by immunoprecipitation reactions. The HIS anti-F10, however, cross-reacted with several larval and adult Taenia spp. Consequently, F10 showed cross-reactions with the sera of animals infected with hydatid cysts or larval T. hydatigena. F10 also reacted with HIS anti-F5 (Echinococcus granulosus) but was shown to be non-identical with the well known F5 of E. granulosus. These data prove that F10 of T. saginata was not species-specific but showed a group specificity for the taeniid family - a situation analogous to F5 of E. granulosus.     

The Asian Taenia and the possibility of cysticercosis

In certain Asian countries, a third form of human Taenia, also known as the Asian Taenia, has been discovered. This Asian Taenia seems to be an intermediate between Taenia solium and T. saginata since in morphological terms it is similar to T. saginata, yet biologically, as it uses the same intermediate host (pigs), it is more akin to T. solium. Taenia solium causes human cysticercosis, while T. saginata does not. It is not known whether the Asian taeniid is able to develop to the larval stage in humans or not. The arguments proposed by those authors who consider it unlikely that the Asian Taenia causes human cysticercosis are: (a) its molecular similarities with T. saginata; (b) the absence of cases of human cysticercosis in populations where the Asian adult is highly prevalent; and (c) the unsupporting results derived from an experimental infestation study. These three arguments are debated, although bearing in mind that at present there is still no clear scientific data to support that human cysticercosis can be caused by the Asian Taenia.     

Experimental human infection with Asian Taenia saginata metacestodes obtained from naturally infected Korean domestic pigs.

The infectivity of metacestodes of Asian Taenia saginata, now tentatively called Taenia saginata taiwanensis, in human host was confirmed. The metacestodes used in experimental infection were collected from the livers of naturally infected domestic pigs at an abattoir in Cheongju City, Korea. The first gravid proglottid was spontaneously discharged 76 days after infection. Two worms were recovered two years later by chemotherapy. The scolex was unarmed. The number of main uterine branches, varying from 16 to 21, was similar to that of classical Taenia saginata. The liver of pigs was confirmed to be an infection source of Asian T. saginata in Korea.     

Taenia spp.: 18S rDNA microsatellites for molecular systematic diagnosis

The 18S rDNA gene of adult worms of Taenia parva found in Genetta genetta in the Iberian Peninsula and larval stages of T. pisiformis from the wild rabbit (Oryctolagus cuniculus) in Tenerife (Canary Islands) were amplified and sequenced. The sequences of the 18S rDNA gene of T. parva (1768 bp) and T. pisiformis (1760 bp) are reported for the first time (GenBank accession nos. AJ555167-AJ555168 and AJ555169-AJ555170, respectively). In 168 alignment positions microsatellites in the 18S rDNA of both taxa were detected for the first time (TGC in T. parva and TGCT in T. pisiformis) and differences in their sequences with different repetition numbers were observed. The use of nucleotide sequences of this gene in the resolution of systematic problems in cestodes is discussed with reference to the systematic status of Taenia spp. and mainly in human taeniids such as T. solium, T. saginata, and Asian human isolates of Taenia.     

Comparison of the peptidase activity in the oncosphere excretory/secretory products of Taenia solium and Taenia saginata

We compared the peptidase activities of the excretory/secretory (E/S) antigens of oncospheres of Taenia solium and related, but nonpathogenic, Taenia saginata. Taenia solium and T. saginata oncospheres were cultured, and the spent media of 24-, 48-, 72-, and 96-hr fractions were analyzed. Activities for serine peptidases (chymotrypsin-, trypsin-, and elastase-like), cysteine peptidases (cathepsin B-, cathepsin L-, and calpaine-like), and aminopeptidase (B-like peptidases) were tested fluorometrically with peptides coupled to 7-amino-4-methylcoumarin. In both species, the E/S antigens showed cysteine, serine, and aminopeptidase activities. Although no particular peptidase had high activity in T. solium, and was absent in T. saginata, or vice versa, different patterns of activity were found. A chymotrypsin-like peptidase showed the highest activity in both parasites, and it had 10 times higher activity in T. solium than in T. saginata. Trypsin-like and cathepsin B-like activities were significantly higher in T. solium. Minimal levels of cathepsin B were present in both species, and higher levels of elastase-like and cathepsin L-like activity were observed in T. saginata. Taenia solium and T. saginata have different levels and temporal activities of proteolytic enzymes that could play a modulator role in the host specificity for larval invasion through penetration of the intestinal mucosa.     

In vitro oncosphere-killing assays to determine immunity to the larvae of Taenia pisiformis, Taenia ovis, Taenia saginata, and Taenia solium

Taeniid cestodes infect humans and livestock, causing considerable morbidity and mortality, as well as economic loss. Substantial progress has been made toward the production of recombinant vaccines against cysticercosis in livestock animals. Further development of these vaccines would be aided if a reliable in vitro test were available to measure host-protective immune responses in vaccinated animals. Here, we describe in vitro oncosphere-killing assays for the quantification of host-protective serum antibodies against Taenia pisiformis, Taenia ovis, Taenia saginata, and Taenia solium in rabbits, sheep, cattle, and pigs, respectively. Activated oncospheres of T. pisiformis, T. ovis, T. saginata, and T. solium were incubated in vitro in culture medium, test serum, and a source of complement, and oncosphere killing was assessed after 10 days of culture. In vitro oncosphere killing reflected the presence of specific antibody, and the oncosphere-killing assay typically indicated immunity to the homologous parasite that had been determined in vivo. This study describes the first reliable oncosphere-killing assays for T. pisiformis, T. ovis, T. saginata, and T. solium. These assays will be used for further research into the optimization of recombinant vaccines against cysticercosis.     

Portrait of human tapeworms

The tapeworms of the genus Taenia that infect human beings are T. solium, T. saginata and T. saginata asiatica. Taenia solium and T. saginata exhibit unequivocal features that characterize them; in contrast, only recent DNA studies, morphological characteristics, and epidemiological and sanitary aspects indicate that T. saginata asiatica is a subspecies of T. saginata. These 3 tapeworms occur in humans in their adult stage, and the intermediate hosts are pigs for T. solium and T. saginata asiatica and cows for T. saginata. Their identification is crucial considering the migratory increase from Asia to the Western Hemisphere and the fact that these tapeworms coexist in the same environment in Asia; furthermore, it is estimated that movement in both directions across the United States-Mexico border exceeds 200 million persons per yr, and thus, opportunities for acquiring and transporting T. solium infections are multiplied. It is not easy to distinguish among these tapeworms; therefore, a comparative diagram of the 3 parasites is shown in this article, which will facilitate their identification. All morphological features, some of which allow for identification, are clear and can be easily distinguished among the 3 tapeworms.     

Taiwan taenia and taeniasis

Toeniids are large tapeworms, common throughout the world. Two species, Taenia saginata and T. solium are common parasites of man. The adult worms parasitize the small intestine, while immature stages (metacestodes or cysticerci) develop mainly in cattle in the case of T. saginata or pigs in the case of T. solium. Cysticerci of T. saginata rarely develop in man, although humans are easily infected with those of T. solium after eating raw or undercooked infected pork-producing the disease known as cysticercosis. In Taiwan, both the pork and beef tapeworms have been documented among aboriginal peoples - with T. saginata considered the most prevalent species. But, as P.C. Fan discusses here, the 'Taiwan Taenia' has several unusual features - not least the fact that beef is not part of the traditional diet of Taiwan oboriginols.     

Experimental infection of pigs and cattle with eggs of Asian Taenia saginata with special reference to its extrahepatic viscerotropism.

Asian Taenia saginata, tentatively called Taenia saginata taiwanensis, has been described to be infected in its metacestode stage only in the liver of intermediate host animals. Experimentally, however, we found that the metacestodes of the Asian Taenia saginata are also infected in other viscera than the liver of pigs (Landrace-Duroc-Hampshire) 4 days to 4 months postinoculation (PI). Viscerotropism of cysticercosis was apparent because a majority (70.7%) of the non-calcified cysticerci were found in the livers while a minority were found in extrahepatic organs such as the omentum (19.2%), lungs (8.1%) and serosa of colon (2.0%). When experimentally infected to cattle, Asian T. saginata cysticerci were also observed calcified in the livers. On the other hand, classical Taenia saginata metacestodes infected the muscles and viscera of the Holstein-Friesian cattle whereas no infection was observed in experimental pigs. Extrahepatic metacestodes of Asian T. saginata, which were obtained from an experimental pig were confirmed to be infective to a male volunteer. This extrahepatic viscerotropism of Asian T. saginata metacestodes in experimental pigs explains well the transmission modes of Asian T. saginata among people considering the eating habits.     

Antigenic components of Taenia saginata and their relevance to the diagnosis of bovine cysticercosis by immunoelectrophoresis.

22 antigenic components of Taenia saginata proglottides were detected by immunoelectrophoretic (IEP) study. Cross-absorption of the hyperimmune serum, raised in rabbits against T. saginata, with heterologous and host antigens showed that two thirds of these components were not specific for the cestode. Among the calves experimentally infected with T. saginata eggs, 3 precipitation patterns in IEP were identified depending on the evolutionary stage of the infection. The hydrosoluble extract of T. saginata was used as antigen. A short precipitating arc present near the antigen well and appearing 3 to 4 weeks post-infection of the calves and a long precipitating arc extending towards the anodic end of the slide and appearing in later stages of infection were found of high diagnostic value. No false-positive reaction or cross-reaction were found. Among the calves harbouring less than 50 cysticerci, false-negative reactions were seen.     

Taenia saginata: differential diagnosis of human taeniasis by polymerase chain reaction-restriction fragment length polymorphism assay

Speciation of Taenia in human stool is important because of their different clinical and epidemiological features. DNA analysis has recently become possible which overcomes the problems of differentiating human taeniid cestodes morphologically. In the present study, we evaluated PCR coupled to restriction fragment length polymorphism to differentiate Taenia solium from Taenia saginata eggs present in fecal samples from naturally infected patients. A different DraI-RFLP pattern: a two-band pattern (421 and 100 bp) for T. saginata and a three-band pattern (234, 188, and 99 bp) for T. solium was observed allowing the two species to be separated. The lower detection limit of the PCR-RFLP using a non-infected fecal sample prepared with a given number of T. saginata eggs was 34 eggs in 2 g stool sediment. The 521 bp mtDNA fragment was detected in 8 out of 12 Taenia sp. carriers (66.6%). Of these, three showed a T. solium pattern and five a T. saginata pattern.     

Asian (Taiwan) Taenia: species or strain?

Recent studies on the epidemoiological pattern of taenisis in Southeast Asia have indicated the existence of a third form of human Taenia which is distinguishable from Taenia saginata and T. solium. Don McManus and Josephine Bowles here review how new genetic evidence supports earlier conclusions that the Asian Taenia is a distinct entity but is closely related T. saginata, and suggests its taxonomic classification as a subspecies or strain of T. saginata is more appropriate than formal designation as a new species.     

A monoclonal antibody-based ELISA for the detection of circulating excretory-secretory antigens in Taenia saginata cysticercosis.

A series of monoclonal antibodies (MoAb) produced against excretory and secretory products from 10- and 20-week-old Taenia saginata cysticerci were tested for their ability to detect circulating antigen in a double antibody sandwich enzyme-linked immunosorbent assay (ELISA). Two MoAb, 12G5 and 2H8, proved to be highly reactive with the tegument of viable T. saginata cysticerci and recognized antigenic components of 65, 87 and 100 kDa in immunoblotting. The detection limit of the assay using 12G5 as trapping antibody and 2H8 as a biotinylated indicator antibody was 0.1 ng protein per ml. Although the sensitivity of the test varied from one animal to another, the minimum number of living cysticerci, which could be detected by the ELISA, was 88. Animals harbouring only dead cysticerci gave similar reactions as non-infected control animals. Cross-reactions were only observed with taeniid parasites. The test was able to detect circulating antigen also in sheep and pigs, respectively infected with T. ovis and T. solium and in the serum samples of confirmed cases of human T. solium cysticercosis.     

Taenia solium: identification of specific antibody binding regions of metacestode 10-kDa protein

Taenia solium neurocysticercosis (NCC) represents one of the major public health problems associated with several neurological manifestations worldwide. We previously identified a recombinant 10-kDa protein of T. solium metacestode (CyDA) specific to active NCC. Immunoblottings with sera from active NCC patients and from animals experimentally infected with larval T. solium (pig), T. saginata (pig), T. asiatica (pig), and T. crassiceps (mouse) strongly recognized CyDA, while sera from patients infected only with adult worms did not. Mapping of antigenic sites using deletion mutants revealed that amino acids (aa) residues 30-34, Asn-Met-Thr-Val-Met (NMTVM), reacted only with sera from active stage T. solium cysticercosis cases. Recognition of CyDA aa 30-34 resided almost exclusively in the IgG4 isotype. Competitive immunoprecipitation with synthetic peptides confirmed the specificity of anti-sera for this penta-peptide. These results demonstrated that aa residues NMTVM in CyDA comprise the core sequence for an active stage NCC-related antigenic determinant. ligand binding protein, HLBP; Cyst fluid, CF; Pooled serum of 10 active NCC patients, serum-pool.     

Complete sequence of the mitochondrial genome of Taenia saginata: comparison with T. solium and T. asiatica

The complete sequence of the Taenia saginata mitochondrial genome was determined, and its organization and structure were compared to other human-tropic Taenia tapeworms for which complete mitochondrial sequence data were available. The mitochondrial genome was 13,670 bp long, contained 12 protein-coding genes, two ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). It did not encode the atp8 gene. Overlapping regions were found between nad4L and nad4, nad1 and trnN, and cox1 and trnT. The ATG initiation codon was used for 10 protein-coding genes, and the GTG initiation codon was used for the remaining 2 genes (nad4 and atp6). The size of the protein-coding genes of the three human Taenia tapeworms did not vary, except for Taenia solium nad1 (891 aa) and nad4 (1212 aa) and Taenia asiatica cox2 (576 aa). The tRNA genes were 57-75 bp long, and the predicted secondary structures of 18 of these genes had typical clover-leaf shapes with paired dihydrouridine (DHU) arms. The genes in all human Taenia tapeworms for the two mitochondrial rRNA subunits rrnL and rrnS are separated by trnC. The putative T. saginata rrnL and rrnS are 972 and 732 bp long, respectively. The non-coding regions of the mt genome of T. saginata consisted of 2 regions: a short non-coding region (SNR, 66 nucleotides) and a long non-coding region (LNR, 159 nucleotides). The overall sequence difference in the full mitochondrial genome between T. saginata and T. asiatica was 4.6%, while T. solium differed by 11%. In conclusion, the complete sequence of the T. saginata mitochondrial genome will serve as a resource for comparative mitochondrial genomics and systematic studies of the parasitic cestodes.     

Taenia saginata: polymerase chain reaction for taeniasis diagnosis in human fecal samples

The taeniasis-cysticercosis complex is a zoonosis of great medical and economic importance where humans play an important role as the carrier of adult stage of Taenia solium and Taenia saginata. This paper describes PCR standardization that can be applied in human fecal samples for taeniasis diagnosis. DNA extraction was achieved with DNAzol reagent, after egg disruption with glass beads. DNA prepared from fecal specimens was first purified and PCR amplified generating fragments of 170 and 600 bp. The assay described herein provides an important tool for T. saginata identification in human fecal samples.     

Organization of atrial natriuretic factor-like immunoreactive system in the brain of the frog Rana esculenta during development

Immunocytochemical distribution of the atrial natriuretic factor (ANF) has been studied in the brain and pituitary of the anuran Rana esculenta during development and in juvenile animals. Using human ANF and rat α-ANF antisera, immunoreactive cell bodies and nerve fibers were revealed in stage II–III tadpoles and in successive larval stages. Soon after hatching, stages II–III, the ANF-like-immunoreactive elements were confined to the preoptic area-median eminence complex. During successive stages of development, new groups of ANF-immunoreactive cell bodies appeared. In larval stage VI, immunoreactive perikarya were found in the rostral part of the anteroventral area of the thalamus and numerous ANF-like-immunoreactive cells appeared in the pars distalis of the pituitary. In larval stages XIV and XVIII, the distribution of ANF immunoreactivity was virtually similar. The ANF-immunoreactive cells in the preoptic nucleus and in the pituitary pars distalis were comparatively more abundant than in stage VI. During the metamorphic climax (stages XXI–XXII), a new group of ANF-immunoreactive cell bodies appeared in the rostral part of the ventrolateral area of the thalamus. During this stage, ANF-immunoreactive fiber projections were found in the pars intermedia for the first time. However, the pars distalis cells were very weakly immunofluorescent. The pattern of ANF immunoreactivity in the brain of juvenile animals was very similar to that described for stages XXI and XXII, whereas the pars distalis cells showed no immunoreactivity. It is conceivable that, early during development, ANF-related peptides may be involved in the regulation of pituitary secretion by means of autocrine mechanisms or may act as a classic pituitary hormone. Received: 28 July 1997 / Accepted: 8 December 1997     

Characterisation of IgG(T) serum antibody responses to two larval antigen complexes in horses naturally- or experimentally-infected with cyathostomins

Cyathostomins are the most common parasitic nematodes of horses. Larval stages, which inhabit the intestinal wall, are particularly pathogenic and can cause severe colitis and colic. Despite their clinical importance, diagnostic techniques for the prepatent stages do not exist. A method that could estimate mucosal infection intensity would have a major impact on the control and diagnosis of cyathostominosis. Here, serum IgG(T) responses to two larval antigen complexes of 25 and 20 kDa were quantified in horses with experimental infections, natural infections and in horses that presented with clinical larval cyathostominosis. In experimentally-infected animals, anti-25 kDa complex IgG(T) levels correlated positively with field exposure and with early third stage larval (r(s)=0.74, P=0.015) and total mucosal parasite (r(s)=0.78, P=0.010) burdens. In naturally exposed horses whose parasite burdens were quantified upon post-mortem examination, antigen-specific IgG(T) responses were significantly higher in infected than in uninfected horses (P=0.0001 and 0.002, for anti-25 and anti-20 kDa responses, respectively). In these animals, anti-25 kDa IgG(T) levels correlated positively with mucosal and lumenal burdens (P<0.05). IgG(T) responses to the 20 kDa antigen complex correlated positively with lumenal burdens (P=0.0043). In cases of larval cyathostominosis, antigen-specific IgG(T) levels were significantly higher than in uninfected ponies (P=0.002 and 0.0035, for anti-25 and anti-20 kDa responses, respectively). These results provide evidence that these two complexes contain antigens with potential as markers for prepatent cyathostomin infection.     

Epidemiology and control prospects of foodborne parasitic zoonoses in the European Union

In the 27 Member States of the European Union, zoonotic parasites transmitted by food are circulating with different prevalence according to the country, the environmental conditions, the human behaviour, and the socio-economic level. Foodborne parasites can be divided in two main groups according to the way of transmission to humans. These foodborne parasites reach the human beings through the consumption of raw infected food such as muscle tissues of different animal species (Toxoplasma gondii, Sarcocystis hominis, Sarcocystis suishominis, Diphyllobotrium latum, Taenia solium, Taenia saginata, Opisthorchis felineus, Anisakis spp., Pseudoterranova spp., Trichinella spp.), or vegetables (Fasciola hepatica), and contaminated food and water resources (Giardia duodenalis, Cryptosporidium spp., T. gondii, Echinococcus granulosus sensu latu, Echinococcus multilocularis, T. solium, Taenia multiceps). As a general role, the control strategies should be based on the education of the consumers, farmers and shepherds, the improvement of farming conditions, the improvement or the development of more sensitive methods to detect these parasites in slaughtered animals and in foodstuff, a control of sewage sludge on pastures and of drinking water resources, and the reduction of contacts between livestock and wild animals which frequently represent the most important reservoir of these pathogens.