Researchers from the Wellcome Sanger Institute, the University of Copenhagen, and others report that they have completed the largest genomic analysis to date of the whipworm Trichuris trichiura. The scientists say their study “Population genomics of ancient and modern Trichuris trichiura,” published in Nature Communications, provides a global set of genetic data upon which to base new disease-fighting methods.
Using the genomic data to create a transmission map and ongoing analysis of the worm’s genetic makeup can help track factors such as drug resistance and predict how the parasite might continue to spread in the future, helping to inform public health decisions, add the scientists.
Trichuriasis is a neglected tropical disease that is estimated to affect as many as 500 million people worldwide. It is caused by T. trichiura and is found most commonly in tropical and subtropical regions. However, parasite eggs found in fossilized remains have shown that the whipworm once was globally distributed, with evidence of this seen in Europe and other sites in North America where infections are rare.
Chronic parasite infections can cause a range of debilitating gastrointestinal issues, nutritional deficiencies, and delays in physical and cognitive development, especially in children. The majority of these cases are treated with one group of drugs, which have varying levels of effectiveness, and there are few alternative treatments available.
The research generated whole-genome DNA sequencing data of modern worms collected from both human and primate hosts. Such recent samples were obtained from multiple different regions including countries in Africa, Central America, Asia, and Europe.
These were compared to ancient samples obtained from archaeological dig sites, the oldest of these dating up to a thousand years old, primarily from Viking settlements in Denmark, as well as sites in the Netherlands and Lithuania. These samples are the oldest helminth samples from which whole-genome sequencing data has been generated, and are suggested to be the oldest eukaryotic pathogens, providing a unique insight into the parasites of humans’ past.
Compared recent data from past and recent parasite
Comparison of genetic data from past and recent parasite from around the world showed how populations of geographically distributed parasites are related and the likely influence of human migration in the global spread of modern day parasites.
The researchers’ data can be used to inform strategies for managing parasites, with the broader aim to reduce the spread of disease. These data could also be used to help track parasite reaction to new and existing treatments, as resistance to current therapies is an obstacle of current drugs which may be increasing.
Through their analysis, the team provides further support that this worm is specific to humans, baboons, and possibly other primates. Therefore, measures to try to stop the spread of T. trichiura will have to take this into consideration as only treating humans could be missing the worms found in other primates in certain regions.
“We describe the continent-scale genetic structure between whipworms infecting humans and baboons relative to those infecting other primates,” write the investigators. “Admixture and population demographic analyses support a stepwise distribution of genetic variation that is highest in Uganda, consistent with an African origin and subsequent translocation with human migration.
“Finally, genome-wide analyses between human samples and between human and non-human primate samples reveal local regions of genetic differentiation between geographically distinct populations. These data provide insight into zoonotic reservoirs of human-infective T. trichiura and will support future efforts toward the implementation of genomic epidemiology of this globally important helminth.”
“Trichuriasis can cause debilitating symptoms and have a huge impact on the development of children in the regions that it is prevalent in, which is why it’s crucial that we find new ways to prevent infections and treat this disease,” said Martin Jensen Søe, PhD, previously at the University of Copenhagen and co-first author of the study. “One of the key takeaways from our research is that certain primates can also carry the disease-causing parasite, so it’s important to take this into consideration when planning measures to stop the spread of Trichuris trichiura.”
