Complete mitochondrial and rDNA complex sequences of important vector species of Biomphalaria, obligatory hosts of the human-infecting blood fluke, Schistosoma mansoni

Abstract

Using high throughput Illumina sequencing technology, we determined complete sequences for the mitochondrial genome (mitogenome) and nuclear ribosomal DNA (rDNA) complex for three African freshwater snail taxa within the genus Biomphalaria, B. pfeifferi, B. sudanica and B. choanomphala, and for two laboratory strains of B. glabrata originating from the Neotropics. Biomphalaria snails are obligate vectors of the blood fluke Schistosoma mansoni, a major etiologic agent of human intestinal schistosomiasis. Our data show that mitogenomes from African and Neotropical Biomphalaria are highly conserved. With respect to rDNA, the two internal transcribed spacers (ITS1 and 2) were found to be highly variable whereas the three ribosomal RNA genes (28S, 5.8S and 18S rRNA) exhibited no or very limited variation. Our analyses reveal that the two taxa inhabiting Lake Victoria, B. sudanica and B. choanomphala, are very similar to one another relative to the similarity either shows to B. pfeifferi or B. glabrata. This new sequence information may prove useful for developing new markers for snail identification, environmental detection/monitoring purposes or for tracking epidemiology and snail dependencies of S. mansoni in endemic areas. It also provides new information pertinent to still unresolved questions in Biomphalaria systematics and nomenclature.

A Search for Snail-Related Answers to Explain Differences in Response of Schistosoma mansoni to Praziquantel Treatment among Responding and Persistent Hotspot Villages along the Kenyan Shore of Lake Victoria

“…Studies of mitochondrial and nuclear markers indicate the two taxa are not highly divergent genetically and should probably be considered as a single species with the species name with precedence yet to be decided. 12,13 It is clear, however, that pockets of snails with the characteristic B. choanomphala phenotype can be recovered from the shoreline over a period of several months. The extent to which snails of the two phenotypes interbreed, the appearance of the progeny, and the nature of genes and alleles dictating compatibility to schistosomes and other trematodes all remain to be investigated.…”

“…9,10 The latter two taxa are likely members of the same species and are frequently referred to as ecophenotypes or ecomorphs. [11][12][13] Prevalence of intestinal schistosomiasis in Kenya is highest (> 50%) in the Mwea Irrigation Scheme in central Kenya and in the Lake Victoria basin in western Kenya. 14 Recent studies assessing the prevalence of S. mansoni infection in school children in the lake basin reported overall prevalences of 60.5% and 69%, with villages on lake islands having 2-fold higher prevalence rates than mainland villages.…”

A search for snail-related answers to explain differences in response ofSchistosoma mansonito praziquantel treatment among responding and persistent hotspot villages along the Kenyan shore of Lake Victoria

“…Studies of mitochondrial and nuclear markers indicate the two taxa are not highly divergent genetically and should probably be considered as a single species with the species name with precedence yet to be decided. 12,13 It is clear though that pockets of snails with the characteristic B. choanomphala phenotype can be recovered from the shoreline over a period of several months. The extent to which snails of the two phenotypes interbreed, the appearance of the progeny, and the nature of genes and alleles dictating compatibility to schistosomes and other trematodes all remain to be investigated.…”

“…9,10 The latter two taxa are likely members of the same species, and are frequently referred to as ecophenotypes or ecomorphs. 11–13…”

The mitochondrial genome of the planorbid snail Planorbella duryi

“…This report presents the mitochondrial genome for the snail Planorbella duryi adding to the limited availability of mitogenome data available for the family Planorbidae that includes several medically important snails that transmit schistosome parasites of humans. (DeJong et al 2004;Jannotti-Passos et al 2010;Zhang et al 2018).…”