Immunological and Molecular Tools for Identification of Echinococcosis and for Epidemiological Studies and the Present Problems in Japan

Recent advances in immunological and molecular approaches for the better resolution of immunodiagnosis of echinococcosis, either in humans or in animals, are briefly overviewed since April 1999. National echinococcosis surveillance in Japan has been performed. However, the lack of an evaluation system to confirm echinococcosis, either alveolar or cystic forms, the echinococcosis cases reported by clinicians, especially those with no or little experience of echinococcosis have limited reliability, except for cases pathologically confirmed after surgery. This systemic problem in Japan is also discussed. The importance of establishing a scientific evaluation system to identifly humans and pets infected with Echinococcus multilocularis in Japan is stressed. identification of the patients of echinococcosis: image diagnosis and serodiagnosis. It has been a matter of some debate whether image diagnosis by CT scan or ultrasonography, or serology for detection of specific antibodies, is a more useful, reliable or practical approach for detecting of hepatic AE. If image figures are typical for either CE or AE, serodiagnosis is not always needed. However, if such figures are atypical, it is important to add serological confirmation using highly specific antigens. WHO is now recommending image diagnosis as the first choice to detect hepatic abnormality, not only in highly endemic areas, but also in developed countries where AE is rare, and the use of serology with specific antigens for confirmation (Pawlowski et al, 2001; Ito and Craig, 2003). Alveolar echinococcosis (AE) Specific antigens for detection of AE, EM10 (Frosch et al, 1991), EM4 (Hemming and McManus, 1991), EmII/3 (Vogel et al, 1988), EmII/3-10 (Muller et al, 1989), and Em18 (Ito et al, 1993) are expected to be reasonably useful. Sako et al (2002) revealed the biochemical and molecular correlations of all these candidate antigens: EM10 is the ezrin-radixin-moesin (ERM)-like protein of E. multilocularis and EM4, EmII/3 and EmII/3-10 are fragments of EM10. Em18 is a degradation product of EM10 by cysteine protease(s). It has been found that Em18 has the lowest homology with human ERM among the EM10 family, and therefore, is expected to be more sensitive in detection of AE cases (Sako et al, 2002). Recent work using recombinant Em18 for differentiation of AE and CE from other parasitic diseases in blind tests has revealed that Em18 is highly sensitive and specific to AE, although minor CE with Correspondence: A Ito, Department of Parasitology, Asahikawa Medical College, Midorigaoka-Higashi 21-1-1, Asahikawa 078-8510, Japan. Tel: +81-166-68-2420; Fax: +81-166-68-2429 E-mail: [email protected] INTRODUCTION Although echinococcosis, in alveolar (AE) and cystic (CE) forms, and neurocysticercosis (NCC), are not among the leading causes of parasite-induced mortality worldwide, these diseases do cause considerable morbidity in humans and economic loss in terms of health and livestock costs (Ito et al, 2003a). AE, CE and NCC are caused by infection with metacestode stage Echinococcus multilocularis, Echinococcus granulosus, and Taenia solium, respectively. Recent advances in technology for detecting these cestode infections in humans and animals are briefly overviewed (Siles-Lucas and Gottstein, 2001; Ito, 2002a; Ito and Craig, 2003; McManus et al, 2003; Zhang et al, 2003). These parasitic infections are zoonotic, techniques to detect or identify (i) patients of AE, CE, and NCC, and (ii) patients or animals infected with taeniid adult worms, are essential for control of these zoonoses. Strategies for detection of infection and control are discussed. Special attention is focused on the pre-mature stage in establishing a system for scientific evaluation of AE after sustained efforts in Japan. RECENT ADVANCES IN TECHNOLOGY FOR HUMAN ECHINOCOCCOSIS There are two strategies for detection and