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The involvement of cellular immunity in alveolar echinococcosis (AE) due to E. multilocularis is strongly suggested by the intense granulomatous infiltration observed around the hepatic parasitic lesions, and a progressive decrease of specific cellular immunity has been described in murine AE. However, specific cellular immunity against E. multilocularis has never been documented in human AE. The reactivity to phytohaemagglutinin (PHA) and E. multilocularis antigens of peripheral blood mononuclear cells (PBMC) from 48 patients with AE and 35 control subjects was evaluated by incorporation of 3H-methylthymidine into DNA. A sequential measurement of the proliferative response of PBMC was performed in 20 patients 2 years later, and again in five of them 4 years after the first determination. After stimulation by PHA, the mean proliferation index (PI) of the patients with AE was somewhat higher than that observed in the uninfected controls, but the difference was not significant. The PI obtained with E. multilocularis antigens was higher than the threshold value in all the patients but one, and in five control subjects. The difference between the PI values in the patients with AE and those obtained in the control subjects was highly significant. There was no correlation between the lymphocyte proliferation indices and the specific antibodies assessed using the Em 2-ELISA, or the volume of the parasitic lesions. All the five 'positive' control subjects were living in areas endemic for AE. A previous contract of these subjects with E. multilocularis in the past, followed by a spontaneous elimination of the parasite is possible. The long-term persistence of lymphocyte reactivity to parasite antigens was emphasized by the results of the follow-up of 20 patients with AE: reactivity of PBMC decreased progressively but persisted more than 4 years after complete resection of the parasitic lesions in the patients who underwent a radical surgical procedure. Conversely, an increase in the PI was shown to be usually associated with a progression of the liver lesions.
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Cloned DNA fragments pHD5, pSM889 and pEG18 have been used as DNA probes in the restriction endonuclease analysis and southern blot hybridization to characterize E. granulosus and E. multilocularis protoscolices from China. Southern blot hybridization method is sensitive, specific and has the advantage in identification over microscopic examination. The authors deem that it can be used in the base-line epidemiological survey and surveillance of hydatid disease to provide data for hydatid disease control.
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A population-based comparative study was performed on public awareness and knowledge about the risk of Echinococcosis and the life habits of the people living in 2 towns in eastern Hokkaido, Bekkai and akan. Bekkai has had an anti-echinococcosis policy and Akan has only limited experiences with such countermeasures. The results of the survey were as follows: 1) Compared with the inhabitants in the town of Akan, the residents in Bekkai had significantly higher correct response rates for many questions concerning parasitological knowledge and the risks of echinococcosis, and knew about subjects such as the pathogen, latency period, susceptible organs, the prognosis, the possibility of transmission of echinococcosis from human to human and methods for the sterilization of eggs from infected animals. 2) The rate of correct answers to such questions were approximately 70 to 90% in both towns. However the percentage of correct answers to questions about carrier animals and the question of human susceptibility were relatively low, ie., 45% and 20%, respectively, even in Bekkai. 3) The residents of Akan knew more about carrier animals of echinococcosis than the inhabitants of Bekkai. In Akan woman and persons in their 20's and 30's had lower rates of correct answers. Further health education should be aimed toward such people. 4) Foxes appeared near private homes more frequently in Akan than in Bekkai. More inhabitants of Akan used spring water as drinking water than in Bekkai, while more inhabitants used tap water as drinking water in Bekkai. Only a few inhabitants paid attention to how to prepare vegetables for cooking. This information suggests that echinococcosis may spread in Akan in the near future. 5) Our results suggest that better organized health education programs, the extension of tap water services in Akan, and the establishment of proper methods for disposal of garbage and the afterbirth of cattle are necessary to reduce the presence of foxes in inhabited areas.
Adults of alveolar Echinococcus species with different uterine structures were collected from Vulpes corsac in the Hulunbeier Pasture of Northeastern China in 2001. They were Echinococcus multilocularis Leuckart, 1863 (type No. 3, similar to E. m. multilocularis), with vaselike uterus; Echinococcus cf. sibiricensis Rausch et Schiller, 1954 (type No. 1), with pyriform uterus; and Echinococcus sp. (type No. 2) with spherical uterus at segment top. The metacestode development in rodents also differed among those 3 parasites. In the case of E. multilocularis (type No. 3), many germinal cells grew on the inner surface of early cysts, most of which metastasized into host tissue to form brood vesicles or from the germinal cell layer on the inner surface of the vesicle wall. Cells also had an appearance of proliferating by means of alveolar buds from alveolar tissue that developed outward to form new alveolar foci. In Echinococcus cf. sibiricensis (type No. 1), the formation of alveolar vesicles was due to the metastasizing of germinal tissue into host tissue; protoscoleces grew in the center of alveolar vesicles. In type No. 2 (Echinococcus sp.), the formation of the alveolar vesicle was by multiplication of germinal cell layers on the inner surface of alveolar cysts; protoscoleces grew from the germinal cell layer and mesh in the vesicles. On the basis of uterine structure and on differences in development of metacestodes in experimental rodents, we propose that the 3 types of Echinococcus represent 3 independent species: E. multilocularis, Echinococcus sibiricensis, and Echinococcus sp. (type No. 2-as yet under study).
A species-specific indirect immunofluorescence test using an anti-Echinococcus oncosphere monoclonal antibody (EgOH6-4E5) was applied to identify Echinococcus oncospheres released from taeniid eggs collected in environmental soil and water samples, and from perianal or faecal samples of naturally infected dogs, in northern Turkana, Kenya. The specificity of immunodetection of Echinococcus eggs by specific fluorescence of Echinococcus oncospheres from naturally infected dogs was 100% when compared to Taenia hydatigena infections, and a sensitivity of 73% was obtained in the detection of dogs infected with Echinococcus using perianal Scotch tape swabs. Taeniid eggs were recovered from various soil samples inside Turkana manyattas (settlements) and from waterhole samples. Some oncospheres obtained from taeniid eggs recovered from all sampled areas, but particularly from inside Turkana huts (akai) and from water samples from open waterholes used by the people and their livestock, reacted positively with the Echinococcus 4E5 monoclonal antibody. The potential importance of contamination of such sites with Echinococcus eggs is discussed in relation to the transmission of echinococcosis in this hyperendemic region of northern Kenya.
This review provides an update of the biological aspects of the genus Echinococcus and focuses on newly recognized endemic areas. Infection with the intermediate cystic stage of all species of Echinococcus causes disease and incapacity in animals and humans, and in the most serious cases, death of the host. Transmission of Echinococcus to new continents has occurred during European colonisation and the parasite has often taken advantage of Echinococcus-naive wildlife populations in these new environments, incorporating them into its transmission pattern. Echinococcus granulosus consists of a complex of 10 strains. Host specificities of these strains have important implications for transmission and control. As a result of human behaviour and/or political instability in a number of countries Echinococcus is re-emerging as an important public health issue. The importance of wildlife reservoirs in perpetuating transmission and as a source of infection for domestic animals and humans is addressed. The review also refers to the transmission pattern of a recently described new species, Echinococcus shiquicus, from China.
Many issues concerning the taxonomy of Echinococcus have been resolved in recent years with the application of molecular tools. However, the status of Echinococcus maintained in transmission cycles involving cervid intermediate hosts remains to be determined. The recent characterization of the parasite from cervids in Finland has highlighted the paucity of data available, particularly that from North America. In this study, we have characterized a large number of Echinococcus isolates from cervids from Western Canada on the basis of morphology and molecular genetic techniques. Our results support earlier studies suggesting that Echinococcus of cervid origin is phenotypically and genetically distinct to Echinococcus maintained in domestic host assemblages, and also confirms that Echinococcus of cervid origin does not constitute a genetically homogeneous group. However, our data do not support the existence of 2 distinct genotypes (strains/subspecies) with separate geographical distributions. Our data appear to support the existence of only 1 species in cervids, but additional isolates from cervids and wolves in other endemic regions should be characterized before a final decision is made on the taxonomic status of Echinococcus in cervids.
Members of the 14-3-3 protein family have been identified as regulatory molecules in intracellular signaling pathways and cell cycle control. Previously, the first Echinococcus 14-3-3 isoform (E14-3-3.1) was isolated from E. granulosus and E. multilocularis metacestode stages. Hyperexpression of this isoform was claimed to be associated with non-restricted tumor-like growth of the E. multilocularis metacestode. In this report, we describe the characterization of a 14-3-3 cDNA from E. granulosus and E. multilocularis corresponding to a second isoform of this family, E14-3-3.2. The characterized 14-3-3 gene was interrupted by two introns whose sequence and positions were conserved in both Echinococcus species. The deduced amino acid sequence of E14-3-3.2 showed 88% identity to the E14-3-3.1 isoform and 52% identity to a third Echinococcus isoform (E14-3-3.3) described by other authors. These findings, coupled to Southern blot analysis, suggest the presence of more than one 14-3-3 gene in Echinococcus. Phylogenenetically, the Echinococcus 14-3-3.1 and 14-3-3.2 isoforms appeared to cluster with zeta-type ("pro-tumorigenic") 14-3-3 isoforms from closely related organisms, whereas the E14-3-3.3 isoform grouped with 14-3-3 epsilon isoforms. The presence of more than one 14-3-3 isoform might indicate isoform-specific roles in the different parasite stages of Echinococcus.