Research Article: Mitochondrial Genome Analyses Suggest Multiple Trichuris Species in Humans, Baboons, and Pigs from Different Geographical Regions

Date Published: September 14, 2015

Publisher: Public Library of Science

Author(s): Mohamed B. F. Hawash, Lee O. Andersen, Robin B. Gasser, Christen Rune Stensvold, Peter Nejsum, James B. Lok. http://doi.org/10.1371/journal.pntd.0004059

Abstract: BackgroundThe whipworms Trichuris trichiura and Trichuris suis are two parasitic nematodes of humans and pigs, respectively. Although whipworms in human and non-human primates historically have been referred to as T. trichiura, recent reports suggest that several Trichuris spp. are found in primates.Methods and FindingsWe sequenced and annotated complete mitochondrial genomes of Trichuris recovered from a human in Uganda, an olive baboon in the US, a hamadryas baboon in Denmark, and two pigs from Denmark and Uganda. Comparative analyses using other published mitochondrial genomes of Trichuris recovered from a human and a porcine host in China and from a françois’ leaf-monkey (China) were performed, including phylogenetic analyses and pairwise genetic and amino acid distances. Genetic and protein distances between human Trichuris in Uganda and China were high (~19% and 15%, respectively) suggesting that they represented different species. Trichuris from the olive baboon in US was genetically related to human Trichuris in China, while the other from the hamadryas baboon in Denmark was nearly identical to human Trichuris from Uganda. Baboon-derived Trichuris was genetically distinct from Trichuris from françois’ leaf monkey, suggesting multiple whipworm species circulating among non-human primates. The genetic and protein distances between pig Trichuris from Denmark and other regions were roughly 9% and 6%, respectively, while Chinese and Ugandan whipworms were more closely related.Conclusion and SignificanceOur results indicate that Trichuris species infecting humans and pigs are phylogenetically distinct across geographical regions, which might have important implications for the implementation of suitable and effective control strategies in different regions. Moreover, we provide support for the hypothesis that Trichuris infecting primates represents a complex of cryptic species with some species being able to infect both humans and non-human primates.

Partial Text: Neglected tropical diseases, including helminthiases, have a devastating effect on human health. It is estimated that about one billion people are infected with soil-transmitted helminths (STHs), including the common roundworm (Ascaris), hookworms (Necator and Ancylostoma spp.), and whipworm (Trichuris), mostly in underprivileged regions of the world [1]. Approximately 0.5 billion people are infected with T. trichiura, resulting in the loss of 0.64 million disability-adjusted life years [2]. Compared with adults, children are more prone to developing clinical symptoms such as dysentery, bloody diarrhea, rectal prolapse, and cognitive impairment in cases of chronic infection [3, 4].

We sequenced the complete mt genomes of Trichuris spp. recovered from a human, baboons, and pigs and evaluated their genetic and evolutionary relationships. Several major haplotypes with clear genetic distinctiveness were observed, suggesting that multiple Trichuris species infect these host species and supporting the hypothesis that whipworms in primates comprise a species complex, which may also be the case for whipworms in pigs (S3 Fig).

Source:

http://doi.org/10.1371/journal.pntd.0004059

 

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