Genetic Uniformity of Echinococcus multilocularis Collected from Different Intermediate Host Species in Hokkaido, Japan

The genetic variation of mitochondrial sequences and pathological differences of Echinococcus multilocularis strains from different continents

Alveolar echinococcosis is a lethal zoonotic disease caused by the fox tapeworm Echinococcus multilocularis. The parasite is widely distributed in the Northern Hemisphere and exhibits low genetic diversity among populations. To compare the differences among four E. multilocularis strains from different geographical locations, namely, Alaska (EM-AK), Japan (EM-JP), Xinjiang (EM-XJ), and Ningxia (EM-NX), their complete mitochondrial (mt) sequences were compared, and their induced pathological lesions were analyzed in mouse models. The complete mt sequence of EM-AK resulted in 0.84%-0.86% variation as compared with the other strains, which had a lower variation. Phylogenetic analysis and parsimony network indicated that EM-AK resulted in 30,000 years of evolutionary distance from the other three strains. EM-AK induced more pathological damage than the other three strains, which was likely to induce more host cell infiltration and acute granuloma in the liver. More importantly, EM-AK produced more protoscoleces than the other three strains, which may impact the transmission dynamics of the parasite. Given the geographical location of four strains, which is far from each other, and also the pathological differences, the strains of E. multilocularis are likely models for addressing the relationship and interfacial immune response between the host and the helminth.IMPORTANCEEchinococcus multilocularis is the causative agent of alveolar echinococcosis, which is considered the most serious parasitic disease in the Northern Hemisphere. There are many genotypes, but the pathogenic and mitochondria sequence and differences are still unclear. Therefore, this study showed both pathological and genetic differences between the four strains of E. multilocularis. EM-AK induced more severe immune responses and especially induced more host cell infiltration, which resulted in more severe granuloma in the liver. EM-JP has metacestode lesions morphologically closer to those of E. granulosus with clear cyst fluid. However, this strain produced much fewer protoscoleces (PSCs). Genetically, EM-AK is more distant from other strains.

Gross, histopathological and immunohistochemical study on strobilocercus of Taenia taeniaeformis infection in the liver of laboratory rats (Rattus norvegicus) in India

We report the detailed gross, histopathological and immunohistochemical study of Strobilocercus fasciolaris infection, the metacestodal stage of Taenia taeniaeformis, in the liver of laboratory Wistar rats. Necropsy examination of seventeen rats revealed transparent or white or cream to clear, thick walled cysts, 1 to 97 in number, measuring about 2mm to 12mm on one or many of the liver lobes and containing strobilocercus of Taenia taeniaeformis. Histopathological examination revealed the presence of the cross-section of larva surrounded by a thick fibrous capsule and moderate infiltration of lymphocytes, plasma cells and a few eosinophils. Fatty degeneration of hepatocytes, gastric mucosal hyperplasia, distended gastric glands and marked increase in the mucosal epithelial cells and goblet cells in the duodenum were also observed. Contamination of feed and bedding materials seems to be the probable source in these naturally infected rats.

The echinococcoses in Asia: The present situation

Human alveolar and cystic echinococcosis, caused by the accidental ingestion of eggs of the tapeworms Echinococcus multilocularis and Echinococcus granulosus sensu lato, respectively, are endemic in Asia. Various Echinococcus species are maintained in domesticated and/or wild mammals through predator-prey interactions. Molecular analysis is used to help differentiate infecting parasite species and genotypes, with the goal of better understanding parasite life cycles in order to aid in the planning and implementation of control programs. This paper discusses the various echinococcoses in Asia, with limited reference to neighboring areas, including parts of Central Asia, Russia, Europe and North America.

The genomic Echinococcus microsatellite EmsB sequences: from a molecular marker to the epidemiological tool

In the field of molecular and epidemiological parasitology, characterization of fast evolving genetic markers appears as an important challenge to consider the diversity and genetic structure of parasites. The study of respective populations can help us to understand their adaptive strategies to survive and perpetuate the species within different host populations, all trying to resist infection. In the past, the relative monomorphic features of Echinococcus multilocularis, the causative agent of alveolar echinococcosis and a severe human parasitic disease, did not stimulate studies dealing with the genetic variability of Echinococcus species or respective populations. A recently developed, characterized and validated original multilocus microsatellite, named EmsB, tandemly repeated in the genome, offered an additional opportunity for this line of investigation. We have compiled in this review new insights brought by this molecular tracker on the transmission activity of Echinococcus among different hosts and at different geographical scales.

Taeniid history, natural selection and antigenic diversity: evolutionary theory meets helminthology

Large sets of nucleotide sequence data of parasitic helminths have been accumulated in the past two decades. Our ability to improve the health of people and animals using this knowledge has not increased proportionally, however. Evolutionary biology provides the background to understand how parasites adapt to their hosts, and computational molecular biology offers the tools to infer the mechanisms involved. The study of antigenic diversity, a way for parasites to overcome host defenses against parasites, has been neglected in helminths, yet such a study could contribute to the development of more efficient drugs, diagnostic tests and vaccines. This review focuses on the study of adaptive evolution as the cause of antigenic diversity in tapeworms and its potential applications.