Study on the ecological distribution of alveolar Echinococcus in Hulunbeier Pasture of Inner Mongolia, China.

A study on the ecological distribution of alveolar Echinococcus was carried out in the Hulunbeier Pasture of Inner Mongolia, China during 1998 and 1999. Animals examined included wolves (Canis lupus), red foxes (Vulpes vulpes), sand foxes (Vulpes corsac), domestic dogs (Canis familiaris), Microtus brandti, Meriones unguiculatus, Citellus dauricus, Allactaga sibirica, Phodopus sungorus and Ochotona daurica. Three wolves were found to be infected with E. granulosus. Two sand foxes were infected with E. multilocularis. The majority of infections of alveolar echinococcus was found in M. brandti. Based on the structure of metacestodes found in the livers of naturally infected M. brandti, 3 main variants were observed. Type I had small alveolar cysts with thin cyst walls. Type II had a larger cyst with a thick cyst wall. Infection of laboratory mice with the gravid segments isolated from the naturally infected sand foxes led to the formation of mature Type I alveolar metacestodes in the lungs and Type II metacestodes in the livers of infected animals, respectively.

[Comparison observation on the mature alveolar of Echinococcus sibiricensis and Echinococcus multilocularis in the experimentally infected white mice].

The alveolar echinococcus is one of the most dangerous worm parasites in man. Rausch and Schiller reported a new species, Echinococcus sibiricensis n. sp. from arctic fox, Alpex logopus, on St. Lawrence Island of Alaska, USA. According to the view of Vogel, the sibiricensis form is only a geographical race or subspecies of Europe Echinococcus multilocularis. So far, the two names, Echinococcus multiocularis multilocularis and Echinococcus multilocularis sibiricensis, existed in many references and text books. We have found the adults of Echinococcus sibiricensis and Echinococcus multilocularis from sand foxes, Vulpes corsac and their larval stages (alveolar echinococcus) from field voles, Microtus brandti in the Hulunbeier Pasture of Inner Mongolia, northeastern China in 1985 and 1998-1999. Two types of metacestodes with quite different styles of early development of E. sibiricensis and E. multilocularis were found from field voles and laboratory experimental white mice. As one characteristic of alveolar E. multilocularis, the capsules are produced by the exogenous budding of germinal cell layer together with cyst wall. The protoscoleces grow from germinal cells on germinal cell layer. The peduncles of early protoscoleces attached to the germinal cell layer on the inner surface of capsule wall(Plate I, Figs. 1-2). Some protoscoleces in reticular structure were linked with the inner surface of capsule wall (Plate I, Fig. 3) in livers of mice in 9.5th month postinfection. In 14th month old alveolar multilocularis, large number of mature protoscoleces in reticular structure were still linked to the inner surface of capsule wall (Plate I, Figs. 4-8). The cavities of some capsules were filled with protoscoleces in meshes of reticular structure which were also linked around with the inner surface of capsule wall (Plate I, Fig. 9). The superficial surface of livers of positive field voles and experimental mice never showed any hyperemic phenomenon. The superficial surfaces of livers and lungs of positive field voles and experimental mice infected with alveolar E. sibiricensis were highly hyperemic. The metacestodes of E. sibiricensis composed of mother cyst, undifferentiated embryonic cysts and small brood capsules. Cavities of all cysts were fully filled with germinal cell masses. Host reaction appeared to be very strong, all cysts were surrounded by thick connective tissue and dense leukocytes (Plate II, Fig. 10). All alveolar vesicles were found located in lungs tissue of experimental mice. Large germinal cell masses metastasized out from undifferentiated embryonic cysts into host lung tissue, where germinal cell masses developed into accumulation of early protoscoleces (Plate II, Figs. 11-12). Early protoscoleces of alveolar E. sibiricensis were seen earliest in mice lung tissues on 101-104th days after infection. Many small capsules in different sizes and different shapes containing mature protoscoleces and reticular structure (Plate II, Figs. 13-15) were found in lungs of mice in 9th month after infection. Only in one experimental mouse infected with alveolar E. sibiricensis in 8.5th month postinfection, both its lung and liver existed alveolar cysts; the capsules in liver were surrounded by very thick connective tissue of the host, and there were some protoscoleces in their cavities (Plate II, Figs. 16-18).