FOLIA PARASITOLOGICA 45: 332-333, 1998
ECHINOCOCCUS MULTILOCULARIS (CESTODA: TAENIIDAE) IN THE CZECH REPUBLIC: THE FIRST DETECTION OF METACESTODES IN A NATURALLY INFECTED RODENT Karel Martínek1, Libuše Kolářová1, Jaroslav Červený2 and Michal Andreas3 1
Department of Tropical Medicine, III Clinic of Infectious and Tropical Medicine, First Faculty of Medicine, Charles University, Bulovka Hospital, Studničkova 7, 128 00 Prague 2, Czech Republic;
2
Institute of Landscape Ecology, Academy of Sciences of the Czech Republic, Květná 8, 603 65 Brno, Czech Republic;
3
Institute of Applied Ecology, Faculty of Forestry, Czech Agriculture University Prague, Nám. Smiřických 1, 281 63 Kostelec nad Černými lesy, Czech Republic
Larval stage (metacestode) of Echinococcus multilocularis (Leuckart, 1863) is the etiologic agent of alveolar echinococcosis in humans. It is known that an infection risk for humans exists in countries or regions with autochthonous occurrence of E. multilocularis in the fox population. Recent studies have shown the presence of E. multilocularis adults in many areas of the Czech Republic (Čada F., Huml O. 1996: Veterinářství 4: 160-162; Kolářová L., Pavlásek I., Chalupský J. 1996: Helminthologia 33: 59-65; Pavlásek I., Chalupský J., Kolářová L., Horyna B., Ritter J. 1997: Epidemiol. Microbiol. Immunol. 46: 158-162). However, reports on the occurrence of larval stages of E. multilocularis in this country do not exist with the exceptions of the only confirmed fatal case of a 74-year-old woman (Šlais J., Mádle A., Vanka K., Jelínek F., Černík V., Průchová M., Jindra J. 1979: Čas. lék. českých 118: 472-475). Therefore, the aim of our study was to examine the occurrence of cestode larval stages in areas where positive foxes were found. The study was performed in the area of Hartmanice (district Klatovy). A total of 10 red foxes Vulpes vulpes (L.) were examined in the period of June to September 1997 for presence of E. multilocularis adults; five of them were positive (intensity of infection from 1 to about 1,200 cestodes). In September 1997, a total of 229 small mammals were captured using the snap traps which were exposed mostly in the forest-meadow ekotons. The following species were examined: 47 specimens of Microtus arvalis (Pallas, 1779), 40 M. agrestis (L.), 36 Clethrionomys glareolus (Schreber, 1780), 22 Pitymys subterraneus (de SélysLongchamps, 1836), 1 Micromys minutus (Pallas, 1771), 16 Apodemus flavicollis (Melchior, 1834), 6 A. sylvaticus (L.), 23 Apodemus sp. - juveniles, 36 Sorex araneus L., 1 S. minutus L. and 1 Talpa europaea L. Organs of small mammals were examined under dissecting microscope. Cysts found were resected, fixed in 70% ethanol and histologically examined using the PAS staining (McManus J.F.A. 1946: Nature 158: 202) E. multilocularis larval cysts were found in one C. glareolus caught in the forest edge, about 100 m from the fox den from which positive foxes originated. Macroscopically, in
the liver two white cyst formations were found (3 and 4 mm in diameter, respectively); the smaller cyst prominated above the surface. Colour and size of the liver were normal while the spleen was considerably enlarged. No cysts in another organ were found. The histological picture of cyst transverse sections corresponded to the morphology of larval stages of E. multilocularis described by many authors (Ohbayashi M., Rausch R.L. and Francis F.H. 1971: Jpn. J. Vet. Res. 19: 1-53; Gottstein B., Hemphill A. 1997: Chem. Immunol. 66: 177208). The examination of the material showed the presence of sterile (no protoscoleces were found), but living metacestodes. The cysts were multivesicular, surrounded by a host inflammatory reaction. The peripheral wall and the intercystous septae of metacestodes consisted of a laminated layer; an inner layer of germinative cells was visible only in some cysts (Fig. 1A). In some of them, mostly on the margin of the cystic formation, cyst wall was absent (Fig. 1B). This can be explained either by that these cysts were very young and, therefore, cyst wall was not yet developed, or the absence of the cyst wall was due to the regression of the metacestode. Although C. glareolus is a susceptible intermediate host, the most important species in the natural life cycle of E. multilocularis in Europe seem to be Microtus arvalis and Arvicola terrestris (Genov T.P., Svilenov D.K., PolyakovaKrusteva O.T., Hlebarov Z.G. 1981: C. R. Bulg. Acad. Sci. 34: 1153-1155; Zyehle E. 1982: In R. Bähr (Ed.): Probleme der Echinokokkose unter Berücksichtigung parasitologischer und klinischer Aspekte. Hans Huber, Bern, pp. 26-33; Petavy A., Deblock S., Gilot B. 1984: C.R. Acad. Sci. III, 299 (18): 735-737; Bonnin J.L., Dellatre P., Artois M., Pascal M., Aubert M.F.A., Petavy A.F. 1986: Ann. Parasitol. Hum. Comp. 61: 235-243. The occurrence of E. multilocularis in both definitive and intermediate hosts provides clear evidence for the existence of an autochthonous cycle of the parasite in the Czech Republic. This is further substantiated by our finding of the metacestode stage in a rodent species. Therefore, a potential infection risk for humans has to be anticipated, and further studies should be undertaken in order to assess the infection risk for humans.
Address for correspondence: K. Martínek, Department of Tropical Medicine, Studničkova 7, 128 00, Prague 2, Czech Republic. Phone: ++420 2 9002 6670; Fax: ++420 2 299 713; E-mail:
[email protected]
332
Fig. 1. The infection of Clethrionomys glareolus liver with larval stages of Echinococcus multilocularis - transverse section through the metacestode (PAS staining): A - multilocular vesiculation of larval stages with collapsed, folded and thin laminated membranes; a narrow band of host tissue surrounds this cystic larva (magnification 37 ×). B - peripheral cysts in which the cyst wall is absent (magnification 176 ×).
Acknowledgements. The investigation was supported by the Grant Agency of Charles University (No. 6-158/97) and the Grant of the Ministry of Health of the Czech Republic (No. 4962-3). Authors are indebted to Prof. Dr. Bruno Gottstein of University of Bern, Switzerland, for his valuable discussion
about the histological material. We thank Mrs. Eva Benonyová of the Department of Pathology, Bulovka Hospital, for her excellent technical assistance and Dr. Petr Horák, Charles University, Prague, for critical comments on the manuscript.
Received 2 February 1998
Accepted 16 April 1998
333
