Biology and Systematics of Echinococcus

Abstract

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;Advances in Parasitology, Volume 95

Historical Aspects of Echinococcosis

“…In the past, at least 16 Echinococcus species were described (Verster, 1965;Ohbayashi, 1993), but subsequently only four of them were recognized as valid (E. granulosus, E. multilocularis, Echinococcus oligarthrus, Echinococcus vogeli) (Verster, 1965;Rausch, 1967a, Thompson, 1986a. The fact that 10 subspecies were morphologically recognized in E. granulosus and only three in E. multilocularis was an indication of a considerable intraspecific variation in E. granulosus.…”

Phylogenetic Pattern, Evolutionary Processes and Species Delimitation in the Genus Echinococcus

“…Echinococcus granulosus typically forms single chambered, unilocular cysts, surrounded by a host-produced fibrous adventitial layer (Thompson, 1995). Growth occurs by concentric enlargement and proliferation of the germinal layer is entirely endogenous (within the laminated layer).…”

“…Growth occurs by concentric enlargement and proliferation of the germinal layer is entirely endogenous (within the laminated layer). The metacestode of E. multilocularis, on the other hand, consists of numerous small vesicles, with no limiting adventitial layer; exogenous proliferation of the germinal layer leads to infiltrating growth through host tissue (Thompson, 1995). Although some variation exists in each of these metacestode structures, the extent and consistency of the differences between the two species clearly indicates a substantial genetic component.…”

“…The term "strain" was used to refer to intraspecific variants of uncertain taxonomic status, including many of the invalidated taxa (Thompson, 1986;Thompson and Lymbery, 1988). Strains were initially described from differences in host occurrence, geographic distribution, morphology and developmental biology, with most strains ascribed to the species E. granulosus.…”

Physiological, Immunological and Histopathological Comparison of Echinococcus Granulosus (G6) Camel Strain by Different Viability Status Using Secondary Cyst Development in Rat

“…It can also result in many acute complications such as anaphylactic responses depending on the number and location of the cysts (Ruedaiet al, 1995).Ten strains of E. granulosus (G1-10) have been described with molecular biology techniques using mitochondrial DNA sequences (McManus and Thompson, 2003). The sheep strain (G1) and camel strain (G6) have a worldwide geographical distribution, specifically in North Africa, the Middle East and in some European countries (Dakkak, 2010;Khalifaet al, 2014;Varcasiaet al, 2011).Comparative studies on the development of various isolates of the parasite have proved particularly useful, not only for speciation and taxonomy but also in the epidemiology and control of hydatidosis (Smyth & Davies, 1974;Thompson, 1977;Thompson, 1982).…”