Whole-genome sequence of the bovine blood fluke Schistosoma bovis supports interspecific hybridization with S. haematobium

Abstract

Mesenteric infection by the parasitic blood fluke Schistosoma bovis is a common veterinary problem in Africa and the Middle East and occasionally in the Mediterranean Region. The species also has the ability to form interspecific hybrids with the human parasite S. haematobium with natural hybridisation observed in West Africa, presenting possible zoonotic transmission. Additionally, this exchange of alleles between species may dramatically influence disease dynamics and parasite evolution. We have generated a 374 Mb assembly of the S. bovis genome using Illumina and PacBio-based technologies. Despite infecting different hosts and organs, the genome sequences of S. bovis and S. haematobium appeared strikingly similar with 97% sequence identity. The two species share 98% of protein-coding genes, with an average sequence identity of 97.3% at the amino acid level. Genome comparison identified large continuous parts of the genome (up to several 100 kb) showing almost 100% sequence identity between S. bovis and S. haematobium. It is unlikely that this is a result of genome conservation and provides further evidence of natural interspecific hybridization between S. bovis and S. haematobium. Our results suggest that foreign DNA obtained by interspecific hybridization was maintained in the population through multiple meiosis cycles and that hybrids were sexually reproductive, producing viable offspring. The S. bovis genome assembly forms a highly valuable resource for studying schistosome evolution and exploring genetic regions that are associated with species-specific phenotypic traits.

Prevalence and distribution of schistosomiasis in human, livestock, and snail populations in northern Senegal: a One Health epidemiological study of a multi-host system

“…Incorporating genomic analysis into future work could provide further insights into the origin, mechanisms, and frequency of novel hybridisations—for example, by improving the crucial distinction between S haematobium – S bovis and S haematobium – S curassoni in highly introgressed parasite specimens and optimising identification of F1 hybrids. 19 , 23 , 26 , 27 …”

“… 10 Naturally occurring viable hybridisation and introgression (genetic flow from one species to another via repeated backcrossing) between and within human and animal schistosomes—particularly within the Haematobium group—are emerging as topics of major importance for global health and disease control. 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 Anthropogenic changes, such as dam construction, migration of people and their animals, and altered agricultural practices, are predicted to increase opportunities for interspecific exposure and co-infection, and therefore hybridisation. 20 , 22 A recent outbreak of human schistosomiasis in Corsica, France, was found to be caused by both S haematobium and S haematobium– S bovis hybrids (closely related to those found in Senegal); however, a local animal reservoir was not identified despite extensive sampling.…”

First record of a tandem-repeat region within the mitochondrial genome of Clonorchis sinensis using a long-read sequencing approach

“…All 12 protein-encoding genes, 22 tRNAs and two rRNAs had high sequence similarities (> 99.2%) to those in published mitochondrial genomes and occurred in the same order. However, there is clear evidence [17,18,38] that conventional sequencing methods are not suited to the sequencing of long non-coding regions in mitochondrial genomes. This obstacle has been overcome through the use of nanopore-sequencing, which bodes well for future mitochondrial genome investigations.…”

Interactions between Schistosoma haematobium group species and their Bulinus spp. intermediate hosts along the Niger River Valley

“…Additionally, epidemiological and ecological characteristics, such as geographical region and intermediate snail and definitive mammalian host associations, are used as proxies for species identification at a given focus [5]. Supported by new field collection and sample preservation methods [6,7], molecular data from schistosome collections have revealed new species distributions [8], interspecies hybridisation [9][10][11][12], and unexpected host associations [13], all of which highlight the need to incorporate molecular analyses into disease surveillance. Molecular data are particularly pertinent for free-living schistosome cercarial larvae, which have limited species-specific morphologies [14] and also for schistosomes that overlap in their snail intermediate host use.…”