Veterinary World (Aug 2021)
A parasitological survey of zoonotic cestodes carried by house rats in Aswan, Egypt, reveals cryptic diversity at the molecular level
Abstract
Background and Aim: Some rat cestodes are zoonotic and are capable of parasitizing humans and animals, raising serious concerns regarding human and veterinary health. The study aimed to determine the prevalence and risk factors for cestodes in Egyptian house rats and to characterize the cestodes molecularly. Materials and Methods: The current survey examined 115 house rats (Rattus rattus) in two cities (Edfu and Aswan) in Egypt's Aswan Governorate for cestode infection using integrated molecular approaches (polymerase chain reaction, sequencing, and phylogenetic analysis) and morphological/morphometrical approaches. Results: The cestodes identified in this study exhibited the typical morphological characteristics of Hymenolepis diminuta (Rudolphi, 1819), Hymenolepis nana (Siebold, 1852) (from rat intestine), and Hydatigera taeniaeformis (from rat liver). The species prevalence rates from these three studies were reported to be 8.7%, 10.4%, and 20.9%, respectively. The ribosomal DNA (ITS1, 18S, and complete ITS) sequences revealed that the hymenolepid sequences were highly distinct but were related to other sequences in the GenBank database, with some sequences showing high similarities to those of H. nana and H. diminuta. In addition, the H. taeniaeformis sequences (ITS2 and mitochondrial cytochrome c oxidase subunit 1 [mtCOX1]) obtained in this study were highly similar to some Taenia taeniaeformis GenBank sequences. The constructed phylogram revealed that the hymenolepidid tapeworms examined in this study were classified into four major branches (the majority of which were hybrids of the two species) and belonged to the genus Hymenolepis. In addition, the phylogram of H. taeniaeformis assigned this species to T. taeniaeformis. Conclusion: When typical hymenolepid morphology is combined with molecular and phylogenetic divergence, it may indicate the existence of possible cryptic species. In addition, on the basis of the phylogenetic analysis, genetic diversity within T. taeniaeformis may exist as determined by comparing the metacestode mtCOX1 sequences. The current study presents the prevalence values of zoonotic cestodes and contributes to the body of knowledge, including identification keys and the use of molecular tools for species confirmation.
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