Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and E. multilocularis, which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Both CE and AE are both serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review discusses new concepts and approaches in the immunology and diagnosis of CE, but comparative reference has also been made to AE infection and to earlier pivotal studies of both diseases. The review considers immunity to infection in the intermediate and definitive hosts, innate resistance, evasion of the immune system, and vaccination of intermediate and definitive hosts, and it particularly emphasizes procedures for diagnosis of CE and AE, including the value of immunodiagnostic approaches. There is also discussion of the new advances in recombinant and related DNA technologies, especially application of PCR, that are providing powerful tools in the fields of vaccinology and molecular diagnosis of echinococcosis.

Concepts in Immunology and Diagnosis of Hydatid Disease

The biology of Echinococcus, the causative agent of echinococcosis (hydatid disease) is reviewed with emphasis on the developmental biology of the adult and metacestode stages of the parasite. Major advances include determining the origin, structure and functional activities of the laminated layer and its relationship with the germinal layer; and the isolation, in vitro establishment and characterization of the multipotential germinal cells. Future challenges are to identify the mechanisms that provide Echinococcus with its unique developmental plasticity and the nature of activities at the parasite-host interface, particularly in the definitive host. The revised taxonomy of Echinococcus is presented and the solid nomenclature it provides will be essential in understanding the epidemiology of echinococcosis.

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Biology and Systematics of Echinococcus.

Publisher Summary This chapter focuses on the public health importance of taeniid cestode zoonoses especially cystic echinococcosis, alveolar echinococcosis and T. solium cysticercosis. The chapter addresses the problem of neurocysticercosis and epilepsy in developing countries particularly Latin America and its public health consequences in the USA and elsewhere. E. multilocularis , which is the cause of one of the most pathogenic of all human parasitic infections, appears to be spreading in parts of western Europe, USA, and Japan. The remarkable development in the past 20 years or so of high resolution imaging technologies, such as computerized tomography (CT) scan and ultrasound have enabled precision detection of taeniid larval cystic infection in humans. Coupled with improvements in immunodiagnostic test sensitivity and antigen specificity, diagnosis of cestode zoonoses is now more accurate than ever before. Although further developments in immunodiagnosis are required, laboratory tests have provided improved capability for screening populations in both epidemiological and community studies. Parallel and recent development of genus specific coproantigen tests for human taeniasis and canine echinococcosis have also provided major new tools for epidemiological and surveillance programs.

Detection, screening and community epidemiology of taeniid cestode zoonoses: cystic echinococcosis, alveolar echinococcosis and neurocysticercosis.

Hydatid disease, hydatidosis and echinococcosis are all terms describing infection with the metacestode of the tapeworm, Echinococcus (Figure 1). The organism requires two mammalian hosts for completion of its lifecycle, a definitive (final) host in which the adult, strobilar stage develops in the small intestine, and an intermediate host in which the cystic metacestode usually develops in the viscera. The definitive host is always a carnivore. It becomes infected by ingesting protoscoleces which are produced by asexual multiplication of the metacestode. There may be several thousand protoscoleces within a single cyst, and each one is capable of developing into a sexually mature adult worm (4-7 mm length). Adult worms produce eggs (30-40 ,um diameter), each containing a single embryo (oncosphere), which are voided in the faeces of the definitive host. The eggs (40 ,um), which are capable of surviving in the environment for varying periods,

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2125.1993.tb04182.x

Diagnosis and treatment of human hydatidosis.

The Echinococcus Western Blot IgG (LDBIO Diagnostics, Lyon, France), using a whole larval antigen from Echinococcus multilocularis, was evaluated for serodiagnosis and differentiation between two human parasitic infections of worldwide importance: cystic echinococcosis, due to Echinococcus granulosus, and alveolar echinococcosis, due to E. multilocularis. Fifty and 61 serum samples from patients with cystic and alveolar echinococcosis, respectively, were used for assessing diagnostic sensitivity. The sensitivity of the assay was compared with those of screening tests used for these applications. Sera used for assessing cross-reactivities were from 154 patients with other diseases, either parasitic or not. The assay allowed the detection of serum immunoglobulin G antibodies in 97% of Echinococcus-infected patients. It had a higher sensitivity than screening assays for the detection for each echinococcosis. The assay allowed us to correctly distinguish between E. granulosus- and E. multilocularis-infected patients in 76% of cases. It did not allow us to distinguish active from inactive forms of both echinococcoses. The occurrence of cross-reactivities with neurocysticercosis indicates the necessity for retesting sera with species-specific antigens, for rare patients with neurologic disorders. This study shows the usefulness of the commercially available Echinococcus Western Blot IgG for the serological confirmation of human echinococcosis.

Immunodiagnosis of Echinococcus infections: confirmatory testing and species differentiation by a new commercial Western Blot.

The purpose of this study was to identify species-specific protein components of Echinococcus multilocularis by Western blotting and establish a simple and highly sensitive method for differential serodiagnosis of alveolar hydatid disease (AHD) from cystic hydatid disease Using Western blotting analyses we demonstrated 2 previously undescribed, species-specific, antigenic components of protoscoleces of E multilocularis easily detectable with sera from active AHD patients exclusively The 18 kDa component was recognized by sera from all active AHD patients, whereas the 16 kDa antigen was characteristically detected by patients with advanced lesions The potential utility of these components for differential serodiagnosis of AHD is discussed

Serodiagnosis of alveolar hydatid disease by western blotting.

Antibody responses against crude antigens and the two (Em18 and Em16) epitopes of Echinococcus multilocularis were analysed by Western blotting using sera from the wild vole, Clethrionomys rufocanus bedfordiae (Crb), which were captured in Hokkaido, Japan and found to have been naturally infected with eggs, and compared with those in patients of AHD and mice experimentally infected with protoscoleces of this parasite. Antibody responses in the wild were demonstrated most clearly with anti-Crb-IgG antiserum but more faintly with anti-rat-IgG antiserum and poorly with anti-mouse-IgG or anti-human-IgG antisera or Protein G. Although only two serum samples of the wild vole found naturally infected were analysed, antibody responses against Em18 and Em16 in these voles appeared to be similar to those in AHD patients but differed from those in mice.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022149X00014462

Antibody responses in the wild vole, Clethrionomys rufocanus bedfordiae, naturally infected with Echinococcus multilocularis by western blotting.

Using DBA/2J mice, tissue homogenates of larval Echinococcus multilocularis were injected into the mesenteric veins to generate the liver infection. Mice were treated with either albendazole or mebendazole for prolonged periods to examine the morphological changes of the metacestode. Albendazole induced disorganization of both laminated and germinal layers and suppressed the maturation of vesicles. Amorphous but loosely laminated PAS-positive material was observed inside the damaged vesicles, although new vesicles slightly developed inside or outside of the damaged ones. Active proliferation of vesicles occurred after treatment with albendazole was terminated. Hydatid cysts were more severely damaged in mice treated with mebendazole and new vesicles did not develop around the damaged ones. Also, hydatid cysts reappeared after treatment with mebendazole was terminated. These results indicate that these drugs do not eliminate larval E. multilocularis in the long-term, but mebendazole has a higher suppressive effect on multivesiculation than albendazole.

Morphological changes of larval Echinococcus multilocularis in mice treated with albendazole or mebendazole.

In secondary hepatic metacestodes of Echinococcus multilocularis at 156 days post-infection, a few small structures exhibiting a central body and a small number of concentric layers were found on the outer surface of the brood capsule, and many such structures were detected on the germinal layer. As these structures are believed to represent immature calcareous corpuscles, we think that not only germinal layer cells but also brood capsule cells of E. multilocularis metacestodes can form calcareous corpuscles.

Possible formation of calcareous corpuscles by the brood capsule in secondary hepatic metacestodes of Echinococcus multilocularis.

Obtention d'une lesion chirurgicalement otee du foie d'un patient et injectee chez un hote intermediaire experimental qui developpe une masse kystique dans sa cavite abdominale

Haruhiko Kutsumi

Papers

Serodiagnosis of alveolar hydatid disease by western blotting.

Antibody responses in the wild vole, Clethrionomys rufocanus bedfordiae, naturally infected with Echinococcus multilocularis by western blotting.

Morphological changes of larval Echinococcus multilocularis in mice treated with albendazole or mebendazole.

Possible formation of calcareous corpuscles by the brood capsule in secondary hepatic metacestodes of Echinococcus multilocularis.

Isolation of larvalEchinococcus multilocularis by injection of infected human hepatic tissue homogenate into the Chinese hamster