Differentiating snail intermediate hosts of Schistosoma spp. using molecular approaches: fundamental to successful integrated control mechanism in Africa.
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ABSTRACT:
SUBMITTER: Abe EM
PROVIDER: S-EPMC5883423 | biostudies-literature | 2018 Mar
REPOSITORIES: biostudies-literature
Publications
Differentiating snail intermediate hosts of Schistosoma spp. using molecular approaches: fundamental to successful integrated control mechanism in Africa.
Abe Eniola Michael EM Guan Wei W Guo Yun-Hai YH Kassegne Kokouvi K Qin Zhi-Qiang ZQ Xu Jing J Chen Jun-Hu JH Ekpo Uwem Friday UF Li Shi-Zhu SZ Zhou Xiao-Nong XN
Infectious diseases of poverty 20180326 1
<h4>Background</h4>Snail intermediate hosts play active roles in the transmission of snail-borne trematode infections in Africa. A good knowledge of snail-borne diseases epidemiology particularly snail intermediate host populations would provide the necessary impetus to complementing existing control strategy.<h4>Main body</h4>This review highlights the importance of molecular approaches in differentiating snail hosts population structure and the need to provide adequate information on snail hos ...[more]
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Project description:BackgroundSnails of the genus Biomphalaria are intermediate hosts of Schistosoma mansoni, the causative agent of the human intestinal schistosomiasis. Two Biomphalaria species (Biomphalaria pfeifferi and Biomphalaria camerunensis) are involved in the transmission in Cameroon, where the disease is present nationwide. However, difficulty in the identification of both vectors impedes proper assessment of the epidemiological burden caused by each species. To overcome this issue, we designed a PCR-based molecular diagnostic tool to improve the identification of these species.MethodsWe analyzed the internal transcribed spacer 2 (ITS2) region of Biomphalaria ribosomal DNA (rDNA) using polymerase chain reaction amplification (PCR) and restriction fragment length polymorphism (RFLP).ResultsThe amplification of the ITS2 region of Biomphalaria snails resulted in a 490 bp fragment and produced two profiles for each species after digestion with the restriction enzyme Hpa II. The profile 1 (Bc-HpaII-1: 212-bp and 139-bp bands) for B. camerunensis, was common in all the sampling points; the profile 2 (Bc-HpaII-2: 212-bp and 189-bp bands), was only observed in the Lake Monoun Njindoun sampling site. Biomphalaria pfeifferi profile 1 (Bpf-HpaII-1: 211-bp and 128-bp bands) was common in most of B. pfeifferi sampling points; the profile 2 (Bpf-HpaII-2: 289-bp and 128-bp bands) was only observed in Mokolo (Far North Cameroon).The second restriction enzyme TaqαI, revealed three band profiles, Bc-TaqαI-1 (243-bp, 136-bp and 118-bp bands) and Bc-TaqαI-2 (244-bp, 136-bp and 99-bp) for B. camerunensis and Bpf-TaqαI-1 (242-bp, 135-bp and 107-bp bands) for B. pfeifferi. Sequencing analysis revealed the occurrence of six haplotypes for B. camerunensis and three haplotypes for B. pfeifferi. The level of gene flow was low and the Biomphalaria populations were not in demographic expansion according to neutrality tests (Tajima's D and Fu's Fs).ConclusionsThe PCR-RFLP technique revealed genetic diversity in Biomphalaria snails, and the combination with the morphological method could improve the identification of B. pfeifferi and B. camerunensis in Cameroon. This could help focus on the infection to evaluate the transmission risk with respect of the different species and to develop efficient and cost-effective control measures.
| S-EPMC7106826 | biostudies-literature
Project description:BackgroundSchistosomiasis is caused by Schistosoma mansoni and S. haematobium in Africa. These schistosome parasites use freshwater snail intermediate hosts to complete their lifecycle. Varied prevalence rates of these parasites in the snail intermediate hosts were reported from several African countries, but there were no summarized data for policymakers. Therefore, this study was aimed to systematically summarize the prevalence and geographical distribution of S. mansoni and S. haematobium among freshwater snails in Africa.MethodsLiterature search was carried out from PubMed, Science Direct, and Scopus which reported the prevalence of S. mansoni and S. haematobium among freshwater snails in Africa. The pooled prevalence was determined using a random-effect model, while heterogeneities between studies were evaluated by I 2 test. The meta-analyses were conducted using Stata software, metan command.ResultsA total of 273,643 snails were examined for the presence of S. mansoni and S. haematobium cercaria in the eligible studies. The pooled prevalence of schistosome cercaria among freshwater snails was 5.5% (95% CI: 4.9-6.1%). The pooled prevalence of S. mansoni and S. haematobium cercaria was 5.6% (95% CI: 4.9-6.3%) and 5.2% (95% CI: 4.6-5.7%), respectively. The highest pooled prevalence was observed from Nigeria (19.0%; 95% CI: 12.7-25.3%), while the lowest prevalence was reported from Chad (0.05%; 95% CI: 0.03-0.13). Higher prevalence of schistosome cercaria was observed from Bulinus globosus (12.3%; 95% CI: 6.2-18.3%) followed by Biomphalaria sudanica (6.7%; 95% CI: 4.5-9.0%) and Biomphalaria pfeifferi (5.1%; 95% CI: 4.1-6.2%). The pooled prevalence of schistosome cercaria obtained using PCR was 26.7% in contrast to 4.5% obtained by shedding cercariae.ConclusionThis study revealed that nearly 6% of freshwater snails in Africa were infected by either S. haematobium or S. mansoni. The high prevalence of schistosomes among freshwater snails highlights the importance of appropriate snail control strategies in Africa.
| S-EPMC7492904 | biostudies-literature
Project description:BACKGROUND:Urogenital schistosomiasis, caused by infection with Schistosoma haematobium, is endemic in Niger but complicated by the presence of Schistosoma bovis, Schistosoma curassoni and S. haematobium group hybrids along with various Bulinus snail intermediate host species. Establishing the schistosomes and snails involved in transmission aids disease surveillance whilst providing insights into snail-schistosome interactions/compatibilities and biology. METHODS:Infected Bulinus spp. were collected from 16 villages north and south of the Niamey region, Niger, between 2011 and 2015. From each Bulinus spp., 20-52 cercariae shed were analysed using microsatellite markers and a subset identified using the mitochondrial (mt) cox1 and nuclear ITS1?+?2 and 18S DNA regions. Infected Bulinus spp. were identified using both morphological and molecular analysis (partial mt cox1 region). RESULTS:A total of 87 infected Bulinus from 24 sites were found, 29 were molecularly confirmed as B. truncatus, three as B. forskalii and four as B. globosus. The remaining samples were morphologically identified as B. truncatus (n?=?49) and B. forskalii (n?=?2). The microsatellite analysis of 1124 cercariae revealed 186 cercarial multilocus genotypes (MLGs). Identical cercarial genotypes were frequently (60%) identified from the same snail (clonal populations from a single miracidia); however, several (40%) of the snails had cercariae of different genotypes (2-10 MLG's) indicating multiple miracidial infections. Fifty-seven of the B. truncatus and all of the B. forskalii and B. globosus were shedding the Bovid schistosome S. bovis. The other B. truncatus were shedding the human schistosomes, S. haematobium (n?=?6) and the S. haematobium group hybrids (n?=?13). Two B. truncatus had co-infections with S. haematobium and S. haematobium group hybrids whilst no co-infections with S. bovis were observed. CONCLUSIONS:This study has advanced our understanding of human and bovid schistosomiasis transmission in the Niger River Valley region. Human Schistosoma species/forms (S. haematobium and S. haematobium hybrids) were found transmitted only in five villages whereas those causing veterinary schistosomiasis (S. bovis), were found in most villages. Bulinus truncatus was most abundant, transmitting all Schistosoma species, while the less abundant B. forskalii and B. globosus, only transmitted S. bovis. Our data suggest that species-specific biological traits may exist in relation to co-infections, snail-schistosome compatibility and intramolluscan schistosome development.
| S-EPMC7247258 | biostudies-literature
Project description:Schistosomiasis, a neglected tropical disease (NTD), is one of the most prevalent parasitoses in the World. Certain freshwater snail species are the intermediate host in the life cycle of schistosome species. Controlling snails employing molluscicides is an effective, quick, and convenient intervention strategy to prevent the spread of Schistosoma species in endemic regions. Advances have been made in developing both synthetic molluscicides and molluscicides derived from plants. However, at present, the development of molluscicides is not adapted to the actual demand for snails and schistosoma controlling. We undertake a systematic review of exploitation and application of synthetic molluscicides and molluscicides derived from plants to combat intermediate host snails. The detailed molluscicidal activity, structure-activity relationship, structural feature, and possible mechanism of some molluscicides are also highlighted, which may afford an important reference for the design of new, more effective molluscicides with low environmental impact and realize the aim of controlling schistosome at transmission stages.
| S-EPMC8418967 | biostudies-literature
Project description:There is a need for recent information on intermediate snail hosts of schistosomes in The Gambia; the previous studies were conducted over three decades ago. This study assessed the incidence, species diversity, distribution and infection status of schistosome intermediate snail hosts in the country. Malacological surveys were conducted in all 5 regions of The Gambia: Central River Region (CRR), Upper River Region (URR), Western Region (WR), Lower River Region (LRR) and North Bank Region (NBR). Sampling of snails was undertaken at 114 sites that included permanent water bodies such as streams (bolongs), rice fields, irrigation canals and swamps; and temporal (seasonal) laterite pools. Ecological and physicochemical factors of sites were recorded. Snails were identified morphologically and screened for schistosome infections using molecular techniques. Freshwater snails were found at more than 50% (60/114) of sites sampled. While three species of Bulinus were collected, no Biomphalaria snails were found in any of the sites sampled. Of the total 2877 Bulinus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. Seasonal pools produced the largest number of snails, and CRR was the region with the largest number of snails. Bulinus senegalensis was found more in seasonal pools as opposed to permanent sites, where B. forskalii and B. truncatus were observed to thrive. Bulinus snails were more common in seasonal sites where aquatic vegetation was present. In permanent sites, the abundance of snails increased with increase in water temperature and decrease in water pH. Bulinus senegalensis was found infected with both S. haematobium and S. bovis, while B. forskalii and B. truncatus had only S. bovis infection. While the human parasite S. haematobium was restricted to just four sites, the livestock parasite S. bovis had a much more widespread geographical distribution across both CRR and URR. This new information on the distribution of intermediate snail hosts of schistosomes in The Gambia will be vital for the national schistosomiasis control initiative.
| S-EPMC8516291 | biostudies-literature
Project description:Schistosomiasis, a neglected tropical disease of medical and veterinary importance, transmitted through specific freshwater snail intermediate hosts, is targeted for elimination in several endemic regions in sub-Saharan Africa. Multi-disciplinary methods are required for both human and environmental diagnostics to certify schistosomiasis elimination when eventually reached. Molecular xenomonitoring protocols, a DNA-based detection method for screening disease vectors, have been developed and trialed for parasites transmitted by hematophagous insects, such as filarial worms and trypanosomes, yet few have been extensively trialed or proven reliable for the intermediate host snails transmitting schistosomes. Here, previously published universal and Schistosoma-specific internal transcribed spacer (ITS) rDNA primers were adapted into a triplex PCR primer assay that allowed for simple, robust, and rapid detection of Schistosoma haematobium and Schistosoma bovis in Bulinus snails. We showed this two-step protocol could sensitively detect DNA of a single larval schistosome from experimentally infected snails and demonstrate its functionality for detecting S. haematobium infections in wild-caught snails from Zanzibar. Such surveillance tools are a necessity for succeeding in and certifying the 2030 control and elimination goals set by the World Health Organization.
| S-EPMC7116084 | biostudies-literature
Project description:BackgroundSchistosoma japonicum is a parasitic flatworm that causes human schistosomiasis, which is a significant cause of morbidity in China, the Philippines and Indonesia. Oncomelania hupensis (Gastropoda: Pomatiopsidae) is the unique intermediate host of S. japonicum. A complete genome sequence of O. hupensis will enable the fundamental understanding of snail biology as well as its co-evolution with the S. japonicum parasite. Assembling a high-quality reference genome of O. hupehensis will provide data for further research on the snail biology and controlling the spread of S. japonicum.MethodsThe draft genome was de novo assembly using the long-read sequencing technology (PacBio Sequel II) and corrected with Illumina sequencing data. Then, using Hi-C sequencing data, the genome was assembled at the chromosomal level. CAFE was used to do analysis of contraction and expansion of the gene family and CodeML module in PAML was used for positive selection analysis in protein coding sequences.ResultsA total length of 1.46 Gb high-quality O. hupensis genome with 17 unique full-length chromosomes (2n = 34) of the individual including a contig N50 of 1.35 Mb and a scaffold N50 of 75.08 Mb. Additionally, 95.03% of these contig sequences were anchored in 17 chromosomes. After scanning the assembled genome, a total of 30,604 protein-coding genes were predicted. Among them, 86.67% were functionally annotated. Further phylogenetic analysis revealed that O. hupensis was separated from a common ancestor of Pomacea canaliculata and Bellamya purificata approximately 170 million years ago. Comparing the genome of O. hupensis with its most recent common ancestor, it showed 266 significantly expanded and 58 significantly contracted gene families (P < 0.05). Functional enrichment of the expanded gene families indicated that they were mainly involved with intracellular, DNA-mediated transposition, DNA integration and transposase activity.ConclusionsIntegrated use of multiple sequencing technologies, we have successfully constructed the genome at the chromosomal-level of O. hupensis. These data will not only provide the compressive genomic information, but also benefit future work on population genetics of this snail as well as evolutional studies between S. japonicum and the snail host.
| S-EPMC10898136 | biostudies-literature
Project description:Sound knowledge of the local distribution and diversity of freshwater snail intermediate hosts and the factors driving the occurrence and abundance of them is crucial to understanding snail-borne parasitic disease transmission and to setting up effective interventions in endemic areas. In this study, we investigated the freshwater snails, water quality parameters, physical characteristics of habitats, predators and competitors, and human activity variables at 102 sites during December 2018 and August 2019 in Shenzhen and adjacent areas in China. We used decision tree models and canonical correspondence analysis to identify the main environmental and biotic factors affecting the occurrence and abundance of snail species. A total of nine species of snail were collected throughout the study area, with Biomphalaria straminea, Sinotaia quadrata, and Physella&nbsp;acuta being the most predominant species. Our study showed that the most important variables affecting the abundance and occurrence of snail species were the presence of predators and competitors, macrophyte cover, chlorophyll-a, substrate type, river depth, and water velocity. In terms of human activities, snail species occurred more frequently and in larger numbers in water bodies affected by human disturbances, especially for sewage discharge, which may reduce the occurrence and abundance of snail predators and competitors. These findings suggest that proper management of water bodies to reduce water pollution may increase the abundance of snail predators and competitors, and should be considered in integrated snail control strategies in the study area.
| S-EPMC9782201 | biostudies-literature
Project description:BACKGROUND:Snails such as Galba truncatula are hosts for trematode flukes causing fascioliasis, a zoonosis that is a major public health problem. Galba truncatula has recently been shown to be a cryptic species complex. African populations of Galba spp. are not yet studied using molecular assessments and is imperative to do so and reconstruct the centre of origin of Galba and to understand when and by what means it may have colonized the highlands of Africa and to what extent humans might have been involved in that process. METHODS:Samples from all known sub-ranges throughout Africa and new samples from Europe and Asia were obtained. We used a combination of two mitochondrial (cox1 and 16S) and one nuclear (ITS2) markers and phylogenetic, divergence time estimates and phylogeographical methods to determine the identity and biogeographical affinities. We also reconstructed the colonization history including the likely mode of dispersal and tested for the presence of cryptic Galba species in Africa. RESULTS:Galba truncatula is restricted to the Palaearctic region of the continent, namely Morocco. All sub-Saharan populations proved to be a distinct species according to the phylogenetic analyses and genetic distance. We propose to use the existing name Galba mweruensis (Connolly, 1929) for this species which is morphologically indistinguishable from the other two species hitherto known to occur in northern Africa, i.e. G. truncatula and G. schirazensis. Sub-tropical Africa has been colonized only once in either the Pliocene and possibly Miocene. Diversification within G. mweruensis is dated to the Plio-Pleistocene and thus human-mediated dispersal can be ruled out for the initial colonization of the isolated mountain ranges. There are potentially even more cryptic species in high altitude areas of Africa as outlined by the distinctness of the population found at the top of Mt. Elgon, Uganda. CONCLUSIONS:From a novel genetic inspection of available African material, a hitherto neglected distinct species, G. mweruensis, now appears a major host of F. hepatica throughout sub-Saharan Africa. A closer examination of trematode parasites hosted by this species is needed in order to understand transmission patterns in highlands throughout eastern and southern Africa. We encourage future studies to inspect other high altitudes areas in Africa in light of parasites of either veterinary or medical importance.
| S-EPMC6894237 | biostudies-literature
Project description:BackgroundKnowledge of the distribution and habitat preference of freshwater snail intermediate hosts can provide information to initiate and set-up effective snail control programmes. However, there is limited research conducted on the factors driving the occurrence and abundance of freshwater snail intermediate hosts in the Ethiopian Rift Valley. Hence, in this study, we investigated how environmental and biotic factors influence the occurrence and abundance of the snail intermediate hosts in Ethiopian Rift Valley region.MethodsData on freshwater snails, physico-chemical water quality parameters, physical characteristics of habitat, predators and competitors, and anthropogenic activity variables were collected from 174 sampling sites during the wet season of 2017 and 2018. Generalized linear models were used to identify the main environmental and biotic factors affecting the occurrence and abundance of the snail species.ResultsIt was found that Bulinus globosus (31.7%) was the most abundant snail species followed by Lymnaea natalensis (21.6%), Lymnaea truncatula (15.1%) and Biomphalaria pfeifferi (14.6%). Generalized linear models indicated that physico-chemical parameters (water temperature, turbidity, chlorophyll-a, dissolved oxygen, chemical oxygen demand, alkalinity, calcium, magnesium, nitrate and ammonia), physical habitat characteristics (water depth, canopy cover, macrophyte cover and substrate type) and biotic factors (abundance of predators and competitors) were found to be the main variables determining the occurrence and abundance of snail species in the Ethiopian Rift Valley region. In terms of anthropogenic activities, human settlement, farming, bathing and swimming, clothes washing, grazing, drainage of land, car washing, boating, fishing and silviculture were also important variables determining the occurrence and abundance of snail species in the region.ConclusionsThe findings reported herein suggest that integrated snail control strategies should be considered to control snails via protection of water bodies from disturbance by anthropogenic activities. In this way, it is possible to reduce the concentration of organic matter and dissolved ions in aquatic ecosystems which are conducive for the presence of snails.
| S-EPMC7282061 | biostudies-literature