Clear Genetic Distinctiveness between Human- and Pig-Derived Trichuris Based on Analyses of Mitochondrial Datasets.

The whipworm, Trichuris trichiura, causes trichuriasis in ∼600 million people worldwide, mainly in developing countries. Whipworms also infect other animal hosts, including pigs (T. suis), dogs (T. vulpis) and non-human primates, and cause disease in these hosts, which is similar to trichuriasis of humans. Although Trichuris species are considered to be host specific, there has been considerable controversy, over the years, as to whether T. trichiura and T. suis are the same or distinct species. Here, we characterised the entire mitochondrial genomes of human-derived Trichuris and pig-derived Trichuris, compared them and then tested the hypothesis that the parasites from these two host species are genetically distinct in a phylogenetic analysis of the sequence data. Taken together, the findings support the proposal that T. trichiura and T. suis are separate species, consistent with previous data for nuclear ribosomal DNA. Using molecular analytical tools, employing genetic markers defined herein, future work should conduct large-scale studies to establish whether T. trichiura is found in pigs and T. suis in humans in endemic regions. Author Summary: Trichuriasis is a neglected tropical disease (NTD) caused by parasitic nematodes of the genus Trichuris (Nematoda), causing significant human and animal health problems as well as considerable socio-economic consequences world-wide. Although Trichuris species are considered to be relatively host specific, there has been significant controversy as to whether Trichuris infecting humans (recognized as T. trichiura) is a distinct species from that found in pigs (recognized as T. suis), or not. In the present study, we sequenced, annotated and compared the complete mitochondrial genomes of Trichuris from these two hosts and undertook a phylogenetic analysis of the mitochondrial datasets. This analysis showed clear genetic distinctiveness and strong statistical support for the hypothesis that T. trichiura and T. suis are separate species, consistent with previous studies using nuclear ribosomal DNA sequence data. Future studies could explore, using mitochondrial genetic markers defined in the present study, cross-transmission of Trichuris between pigs and humans in endemic regions, and the population genetics of T. trichiura and T. suis. [ABSTRACT FROM AUTHOR]