Comparison of Montana and Alaska Isolates of Echinococcus multilocularis in Gerbils with Observations on the Cyst Growth, Hook Characteristics, and Host Response

Abstract

To assess its biological distinctness, an isolate of Echinococcus multilocularis from Montana was compared with an isolate from Alaska in gerbils (Meriones unguiculatus) by means of intraperitoneal inoculations with protoscoleces. The cysts formed by the Montana isolate were entire, hyaline, and translucent, whereas those produced by the Alaska isolate were granular, yellowish, and opaque. Vesicles of the Montana isolate were larger, produced protoscoleces more slowly but in greater numbers, and required a longer period to develop surfacial germ cell protrusions, which were of smaller size. Also delayed was invasion of the laminate layer by granulocytes and macrophages, and a longer time was required for the appearance of pulmonary metastases. The 2 isolates differed also in characteristics of rostellar hooks, those from the Montana isolate being fewer and larger, often with accessory hooks.

Echinococcus multilocularisin North America: the great unknown

“…A recent study on the genetic characterization of E. multilocularis mitochondrial DNA [ 62 ] identified three strains corresponding to the geographical regions of Asia, Europe, and North America [ 18 ]. In North America, two sub-strains have been reported (N1 in the tundra zone and N2 in the central region) [ 62 ], supporting previous reports that parasites from Alaska and the north-central states of Montana and North Dakota differed in the development of their larval stages [ 5 , 72 ].…”

“…However, differences in temperature and humidity also likely affect parasite egg survival in the environment [ 91 ], and therefore, parasite transmission in the different regions [ 29 ]. Moreover, differences in host susceptibility to infection and the pathogenicity of different E. multilocularis strains [ 5 ] may also impact parasite transmission across eco-regions.…”

Global Distribution of Alveolar and Cystic Echinococcosis

“…Although morphologically similar, early experimental infections demonstrated distinct developmental differences between NTZ and NCR isolates of E. multilocularis (Bartel et al, 1992;Rausch and Richards, 1971). This was supported later by recognition of genetic differences between the NTZ (North American N1 and Asian) and NCR (North American N2)…”

Genetic Analysis of Echinococcus multilocularis Originating from a Patient with Alveolar Echinococcosis Occurring in Minnesota in 1977

“…6,7 The reasons are not fully understood; however, human behavioral factors 21 and life cycles of the parasite involving synanthropic or sylvatic transmission 4,18 may be hypothesized. Genetic variations 9,10,13,14 and biological attributes 22 among E. multilocularis isolates and immunogenetic factors in humans [23][24][25][26][27][28] might play some roles in infectivity of E. multilocularis to humans. Because there are limited data on genotypes/haplotypes of E. multilocularis from North America except for Alaska, the data reported here may also provide useful information in considering the phylogeography of E. multilocularis.…”