Genomic analysis of Strongyloides stercoralis and Strongyloides fuelleborni in Bangladesh

Abstract

AbstractBackgroundAbout 600 million people are estimated to be infected withStrongyloides stercoralis, the species that causes the vast majority of human strongyloidiasis cases.S. stercoraliscan also infect non-human primates (NHPs), dogs and cats, rendering these animals putative sources for zoonotic humanS. stercoralisinfection.S. fuelleborniis normally found in old world NHPs but occasionally also infects humans, mainly in Africa. Dogs in southeast Asia carry at least two types ofStrongyloides, only one of which appears to be shared with humans (“dog only” and “human and dog” types). ForS. stercoraliswith molecular taxonomic information, there is a strong sampling bias towards southeast and east Asia and Australia.Methodology/Principle findingsWe collected human and dog derivedStrongyloidesspp. and hookworms from two locations in Bangladesh and subjected them to molecular taxonomic and genomic analysis based on nuclear and mitochondrial sequences. All hookworms found wereNecator americanus. Contrary to earlier studies in Asia, we noticed a rather high incidence ofS. fuelleborniin human samples. Also in this study, we found the two types ofS. stercoralisand no indication for genetic isolation from the southeast Asian populations. However, we found oneS. stercoralisworm in a human sample that genomically was of the “dog only” type and we found two worms in a dog sample that had the nuclear genomes of the “dog only” type but the mitochondrial genome of the “human and dog” type.Conclusions/SignificanceS. fuellebornimay play a more prominent role as a human parasite in certain places in Asia than previously thought. The introgression of a mitochondria haplotype into the “dog only” population suggests that rare interbreeding between the twoS. stercoralistypes does occur and that exchange of genetic properties, for example a drug resistance, between the two types is conceivable.Author SummaryMore than 600 million people are infected with the nematode intestinal parasiteStrongyloides stercoralis. Dogs can also carryS. stercoralis. In southeast Asia different genetic types that either infect only dogs or humans and dogs were described.Strongyloides fuelleborni, (normally found in old-world monkeys) can also infect humans, mainly in Africa. We collectedStrongyloidesspp. and hook worms, from humans and a dog in Bangladesh and analyzed their nuclear and mitochondrial genomes. All hookworms wereNecator americanus, one of the two major human hookworm species. Contrary to the general believe that human infections withS. fuelleborniare extremely rare in Asia, we found multiple such cases, suggesting thatS. fuelleborniplays a more important role as a human parasite than previously thought also in Asia.We found the two expected genetic types ofS. stercoralis. For the first time we found a genomically “dog only” type worm in a person and we found two worms with nuclear genomes of the “dog only” type but mitochondrial genomes of the “human and dog” type. This suggest that rare interbreeding between the two types occurs, such that exchange of genetic properties, such as a drug resistance, between the two types is conceivable.