SUMMARY: The taxonomic status of Echinococcus, an important zoonotic cestode genus, has remained controversial, despite numerous attempts to revise it. Although mitochondrial DNA (mtDNA) has been the source of markers of choice for reconstructing the phylogeny of the genus, results derived from mtDNA have led to significant inconsistencies with earlier species classifications based on phenotypic analysis. Here, we used nuclear DNA markers to test the phylogenic relationships of members of the genus Echinococcus. The analysis of sequence data for 5 nuclear genes revealed a significantly different phylogeny for Echinococcus from that proposed on the basis of mitochondrial DNA sequence data, but was in agreement with earlier species classifications. The most notable results from the nuclear phylogeny were (1) E. multilocularis was placed as basal taxon, (2) all genotypes of Echinococcus granulosus grouped as a monophyletic entity, and (3) genotypes G8 and G10 clustered together. We conclude that the analysis of nuclear DNA data provides a more reliable means of inferring phylogenetic relationships within Echinococcus than mtDNA and suggest that mtDNA should not be used as the sole source of markers in future studies where the goal is to reconstruct a phylogeny that does not only reflect a maternal lineage, but aims to describe the evolutionary history at species level or higher.

Two recombinant Taenia solium oncosphere antigens, designated TSOL18 and TSOL45-1A, were investigated as vaccines to prevent transmission of the zoonotic disease cysticercosis through pigs. Both antigens were effective in inducing very high levels of protection (up to 100%) in three independent vaccine trials in pigs against experimental challenge infection with T. solium eggs, which were undertaken in Mexico and Cameroon. This is the highest level of protection that has been achieved against T. solium infection in pigs by vaccination with a defined antigen. TSOL18 and TSOL45-1A provide the basis for development of a highly effective practical vaccine that could assist in the control and, potentially, the eradication of human neurocysticercosis.

Three recent studies of Blastocystis epidemiology in mammalian hosts identified four novel sequences that appeared to share B. lapemi as the most similar sequence. However, full-length ssu rRNA gene sequences were not available to confirm the validity of these new subtypes. In the present study, Nanopore MinION sequencing was used to obtain full-length reference sequences for each of the new subtypes. Additionally, phylogenetic analyses and pairwise distance comparisons were performed to confirm the validity of each of these new subtypes. We propose that the novel sequences described in this study should be assigned the subtype designations ST35-ST38. The full-length reference sequences of ST35-ST38 will assist in accurate sequence descriptions in future studies of Blastocystis epidemiology and subtype diversity.

Various mammals were evaluated as experimental models of adult Taenia solium. Suppressed and nonsuppressed hosts were used as experimental models. Infections were performed per os with cysticerci obtained from pigs; immunosuppression was induced with methyl prednisolone acetate at intervals of 10-14 days after infection. Tapeworms developed in hamsters, gerbils, and chinchillas but failed to develop in rabbits, cats, pigs, and rhesus monkeys. In infectable animals, treatment with the steroid facilitated maintenance and development of the parasite, and more tapeworms were obtained. Mature and some pregravid proglottids were recovered from hamsters and gerbils, whereas a gravid T. solium was obtained from a chinchilla at 12 wk postinfection. Eggs recovered from the chinchilla transformed into cysticerci in a pig 12 wk after oral infection. The T. solium-chinchilla experimental system seems to be an alternative definitive host for this parasite and thus the basis for a great diversity of studies.