Morphological and molecular characterization of Trichuris muris (Nematoda: Trichuridae): studies from two commensal rodent species

In this paper we re-describe Trichuris muris based on morphological data following isolation from two commensal rodent species, Mus musculus from Mexico and Rattus rattus from Argentina. Furthermore, we provide a molecular characterization based on mitochondrial (cytochrome c oxidase subunit 1 mitochondrial gene) and nuclear (internal transcribed spacer 2 region) markers in order to support the taxonomic identification of the studied specimens of T. muris from M. musculus. We distinguished T. muris from 29 species of Trichuris found in American rodents based on morphological and biometrical features, such as the presence of a spicular tube, length of spicule, size of proximal and distal cloacal tube and non-protrusive vulva. We suggest that spicular tube patterns can be used to classify Trichuris species in three groups. Considering that the diagnosis among the species of this genus is mainly based on morphometry, this proposal represents a relevant contribution. We provide molecular studies on two markers, making this the first contribution for T. muris in the Americas. This study makes an important contribution to the integrative taxonomy of cosmopolitan nematode species, and its correct determination from the parasitological study of commensal rodents.

Research Note. Occurrence of gastrointestinal helminths in commensal rodents from Tabasco, Mexico

The aim of this study was to determine the prevalence and species composition of helminths in commensal rodents captured inside private residences in the city of Villahermosa in Tabasco, Mexico. Trapping was performed at each house for three consecutive nights from October to December 2015. Fifty commensal rodents were captured: 23 Rattus norvegicus, 16 Mus musculus and 11 Rattus rattus. Rodents were transported alive to the laboratory and held in cages until they defecated. Feces were analyzed for helminth eggs using the Sheather’s flotation technique. The overall prevalence of helminths in rodents was 60 %: R. norvegicus was more likely to be parasitized (87.0 %) than R. rattus (63.6 %) and M. musculus (18.8 %). Eggs from at least 13 species of helminths were identified: Hymenolepis diminuta, Rodentolepis nana, Moniliformis moniliformis, Heligmosomoides polygyrus, Heterakis spumosa, Mastophorus muris, Nippostrongylus brasiliensis, Strongyloides ratti, Syphacia obvelata, Syphacia muris, Toxocara sp., Trichosomoides crassicauda, and Trichuris muris. This is the first study to report the presence of H. polygyrus, S. ratti and T. crassicauda in commensal rodents in Mexico. In conclusion, our results suggest that helminths commonly infect commensal rodents in Villahermosa and therefore rodents present a health risk to inhabitants in this region.