Virus-derived sequences from the transcriptomes of two snail vectors of schistosomiasis, Biomphalaria pfeifferi and Bulinus globosus from Kenya

Schistosomiasis, which infects more than 230 million people, is vectored by freshwater snails. We identified viral sequences in the transcriptomes of Biomphalaria pfeifferi (BP) and Bulinus globosus (BuG), two of the world’s most important schistosomiasis vectors in Africa. Sequences from 26 snails generated using Illumina Hi-Seq or 454 sequencing were assembled using Trinity and CAP3 and putative virus sequences were identified using a bioinformatics pipeline. Phylogenetic analyses were performed using viral RNA-dependent RNA polymerase and coat protein sequences to establish relatedness between virus sequences identified and those of known viruses. Viral sequences were identified from the entire snail holobiont, including symbionts, ingested material and organisms passively associated with the snails. Sequences derived from more than 17 different viruses were found including five near full-length genomes, most of which were small RNA viruses with positive sense RNA genomes (i.e., picorna-like viruses) and some of which are likely derived from adherent or ingested diatoms. Based on phylogenetic analysis, five of these viruses (including BPV2 and BuGV2) along with four Biomphalaria glabrata viruses reported previously, cluster with known invertebrate viruses and are putative viruses of snails. The presence of RNA sequences derived from four of these novel viruses in samples was confirmed. Identification of the genome sequences of candidate snail viruses provides a first step toward characterization of additional gastropod viruses, including from species of biomedical significance.

PREVALLENCE OF SCHISTOSOMIASIS (URINARY BILHARZIA) INSINAZONGWE DISTRICT

Purpose of study: This study investigated the prevalence of Urinary Schistosomiasis in Zambia’s Sinazongwe district. Methodology: Three primary schools in Sinazongwe district were sampled by convenient sampling and these were: Mwezya primary, Sinakasikili primary and Maamba private. 542 urine samples were collected from pupils examined in the laboratory at Maamba Hospital. Snail survey was carried out along 3 streams that are near the selected schools; Siamaambo stream which is near Mwezya primary school, Kanzinze stream which is near Sinakasikili primary school and another stream also called Kanzinze which is near Maamba private school. Findings: Study revealed that schistosomiasis is still highly existent in the district despite the ongoing administration of praziquantel; nonetheless, most of the infections are of low intensity and more males were infected than females. From the snail survey, Bulinus globosus the intermediate host for Schistosoma haematobium was found to be among the several snail species in Siamaambo stream and released cercaria when exposed to a light source, therefore they were infected and were/are the source of the bilharzia infection in Mwezya (Mwezya primary school). Unique contribution to theory, practice and policy: From results obtained, it can be seen that despite the administration of praziquantel to school going children, schistosomiasis will still be a problem in Sinazongwe district because the source of infection is not dealt with; as a result, there is continuous re-infection of the treated and untreated children. Therefore, comprehensive control by chemotherapy and snail control to eradicate the disease or at least lower the prevalence is recommended; and health officials that are involved in the administration of praziquantel should make follow-ups time-to-time after drug administration to evaluate the effectiveness of prophylactic program. Health education and provision of tap water is also recommended in this area to reduce frequent contact with contaminated water in streams.

Spatial and seasonal distribution of Bulinus globosus and Biomphalaria pfeifferi in Ingwavuma, uMkhanyakude district, KwaZulu-Natal, South Africa: Implications for schistosomiasis transmission at micro-geographical scale

Background Schsistosomiasis is endemic in sub-Saharan Africa. It is transmitted by intermediate host snails such as Bulinus and Biomphalaria. An understanding of the abundance and distribution of snail vectors is important in designing control strategies. This study describes the spatial and seasonal variation of B. globosus and Bio. pfeifferi and their schistosome infection rates between May 2014 and May 2015 in Ingwavuma, uMkhanyakude district, KwaZulu-Natal province, South Africa. Methods Snail sampling was done on 16 sites once every month by two people for 30 min at each site using the scooping and handpicking methods. Snails collected from each site were screened for schistosome mammalian cercariae by the shedding method. The negative binomial generalised linear mixed model (glmm) was used to determine the relationship between abundances of the intermediate host snails and climatic factors [rainfall, land surface temperatures (LST), seasons, habitats, sampling sites and water physico-chemical parameters including pH and dissolved oxygen (DO)]. Results In total, 1846 schistosomiasis intermediate host snails were collected during the study period. Biompharia pfeifferi was more abundant (53.36%, n = 985) compared to B. globosus (46.64%, n = 861). Bulinus globosus was recorded at 12 sites (75%) and Bio. pfeifferi was present at 7 sites (43.8%). Biompharia pfeifferi cohabited with B. globosus at all the sites it was present. High numbers of Bio. pfeifferi (n = 872, 88.5%) and B. globosus (n = 705, 81.9%) were found between winter and mid-spring. Monthly rainfall showed a statistically significant negative relationship with the abundance of B. globosus (p < 0.05). Dissolved oxygen (DO) had a statistically significant positive relationship with the abundance of Bio. pfeifferi (p < 0.05) while (LST) had a statistically significant negative relationship (p < 0.05). More B. globosus (8.9%, n = 861) were shedding schistosome mammalian cercariae compared to Bio. pfeifferi (0.1%, n = 985) confirming the already documented high prevalence of S. haematobium in Ingwavuma compared to S. mansoni. Conclusion Results of this study provide updated information on the distribution of schistosomiasis intermediate host snails in the study area and contributes towards the understanding of the transmission dynamics of schistosomiasis at the micro-geographical scale in this area. Graphic Abstract

Mastomys natalensis (Smith, 1834) as a natural host for Schistosoma haematobium (Bilharz, 1852) Weinland, 1858 x Schistosoma bovis Sonsino, 1876 introgressive hybrids

Cercarial emission of schistosomes is a determinant in the transmission to the definitive host and constitutes a good marker to identify which definitive host is responsible for transmission, mainly in introgressive hybridization situations. Our goal was to test the hypothesis that micro-mammals play a role in Schistosoma haematobium, S. bovis, and/or S. haematobium x S. bovis transmission. Small mammal sampling was conducted in seven semi-lacustrine villages of southern Benin. Among the 62 animals trapped, 50 individuals were investigated for Schistosoma adults and eggs: 37 Rattus rattus, 3 Rattus norvegicus, 9 Mastomys natalensis, and 1 Crocidura olivieri. Schistosoma adults were found in four R. rattus and two M. natalensis, with a local prevalence reaching 80% and 50%, respectively. Two cercarial chronotypes were found from Bulinus globosus experimentally infected with miracidia extracted from naturally infected M. natalensis: a late diurnal and nocturnal chronotype, and an early diurnal, late diurnal, and nocturnal chronotype. The cytochrome C oxidase subunit I mtDNA gene of the collected schistosomes (adults, miracidia, and cercariae) belonged to the S. bovis clade. Eleven internal transcribed spacer rDNA profiles were found; four belonged to S. bovis and seven to S. haematobium x S. bovis. These molecular results together with the observed multi-peak chronotypes add M. natalensis as a new host implicated in S. haematobium x S. bovis transmission. We discuss the origin of the new chronotypes which have become more complex with the appearance of several peaks in a 24-h day. We also discuss how the new populations of offspring may optimize intra-host ecological niche, host spectrum, and transmission time period.

Comparison for the Efficacy of Column Purified Fractions of Sinna occidentalis and Moringa oleifera against Bulinus globosus (Intermediate Host of Schistosoma haematobium) from Goronyo and Shagari Dams, Sokoto State, Nigeria

Introduction: Although, used of molluscicides to control the intermediate host of schistosomes is the best method of choice to control the spread of the snail fever among the people, synthetic molluscicides widely used are cost effective, not available and toxic to the aquatic lives and people that are completely or partially dependents on rivers or lakes water for their everyday supplement. Aim: this research was aimed at investigation and comparison for the molluscicidal efficacy for S. occidentalis and M. oleifera leaves extracts against B. globosus (intermediate host of Schistosoma haematobium). Methodology: Each of the plant was grinded into powder and purified through column using different solvents, B. globosus snails were collected from Shagari and Goronyo dams; we identified the animal using chart initially, later on the animals were confirmed as B. globosus by malacologist from Ahmadu Bello University Zaria, Nigeria; the Molluscicidal efficacy of the plants was tested against B. globosus and compared according to world health organization guidelines; mortality was calculated using Abbort’s formula and analysis of variance (ANOVA) was used to determine if there is significant different between the mean mortality at P<0.05; qualitative Phytochemical analysis was conducted to determine the chemicals presence in each plant and their combination. Results: Present study reviled that fractions of the leaves combination showed significantly higher mortality of B. globosus in the present study followed by Fractions of S. occidentalis then that of M. oleifera. For the plants combination, extracts purified using methanol are highly toxic followed by fractions purified using hexane, then ethyl acetate fractions and least Molluscicidal potential was recorded in the fractions obtained using ethanol. S. occidentalis fractions of hexane were highly toxic followed by fractions of methanol, then fractions of ethyl acetate and least mortality was recorded from the fractions of ethanol. Similarly, for the M. oleifera, it was observed that, fractions of Methanol were highly toxic followed by hexane fractions then ethanol fractions and least mortality was observed in the fractions of ethyl acetate. Conclusion: Column purified fractions for the combination for two plants leaves were highly potent for the control of B. globosus followed by S. occidentalis then M. oleifera.

Evaluating the Ecology and Distribution of Snail Hosts of Schistosoma at the Water Bodies in Ihitte-Uboma Area of Imo State

Intermediate snail host of Schistosoma species are known to exist and constitute public health problems in Imo state. Effects on this study were devoted to evaluate the ecology and distribution of the snail hosts of Schistosoma species at the water bodies of Ihitte Uboma local Government area and this was researched during the months of June and September, 2015. A total of 600 pulmonate or lunged snails were collected using scoop net technique from different water bodies in five villages, out of these, 345 (57.5%) were dissected and screened for cercariae of human Schistosomes 67 (19.4%) tested positive. The snail infected were Bulinus species 55 (82.1%) and Biomphalaria Pfeifferi (17.9%), out of the Bulinus species, Bulinus globosus recorded the widest ecological range, highest distribution and infection rate of 44.8% followed by Bulinus truncatus (22.4%). The other two genera Lymnaea spp and Melanoides spp encountered in the study did not test positive for cercariae. Environmental modifications such as water resources development schemes in the area are some of the ecological and epidemiological risk factor promoting the spread of the snails. Statistically, presence of urinary and intestinal Schistosomiasis becomes indicated in Ihitte Uboma L.G.A. Regular and timing mollusciciding, malacological and public health education are therefore recommended and imperative.

Molecular diversity of Bulinus species in Madziwa area, Shamva district in Zimbabwe: implications for urogenital schistosomiasis transmission

Background Bulinus species are freshwater snails that transmit the parasitic trematode Schistosoma haematobium. Despite their importance, the diversity of these intermediate host snails and their evolutionary history is still unclear in Zimbabwe. Bulinus globosus and B. truncatus collected from a urogenital schistosomiasis endemic region in the Madziwa area of Zimbabwe were characterized using molecular methods. Methods Malacological survey sites were mapped and snails were collected from water contact sites in four communities in the Madziwa area, Shamva district for a period of one year, at three-month intervals. Schistosoma haematobium infections in snails were determined by cercarial shedding and the partial mitochondrial cytochrome c oxidase subunit 1 gene (cox1) was used to investigate the phylogeny and genetic variability of the Bulinus spp. collected. Results Among the 1570 Bulinus spp. snails collected, 30 (1.9%) B. globosus were shedding morphologically identified schistosomes. None of the B. truncatus snails were shedding. The mitochondrial cox1 data from 166 and 16 samples for B. globosus and B. truncatus, respectively, showed genetically diverse populations within the two species. Twelve cox1 haplotypes were found from the 166 B. globosus samples and three from the 16 B. truncatus samples with phylogenetic analysis showing that the haplotypes fall into well-supported clusters within their species groups. Both B. truncatus and B. globosus clustered into two distinct lineages. Overall, significant negative values for both Tajima’s D statistic and the Fu’s Fs statistic were observed for B. globosus and B. truncatus. Conclusions The study provided new insights into the levels of genetic diversity within B. globosus and additional information on B. truncatus collected from a small geographical area in Zimbabwe. Low prevalence levels of infection observed in the snails may reflect the low transmission level of urogenital schistosomiasis in the area. Our results contribute towards the understanding of the distribution and population genetic structure of Bulinus spp. supporting the mapping of the transmission or risk of transmission of urogenital schistosomiasis, particularly in Zimbabwe.

Survey of Fresh Water Snails in Vandeikya Local Government Area, Benue State Nigeria

A survey was carried out in Vandeikya Local Government Area of Benue State, Nigeria from April-July 2017 to determine availability of freshwater snails of and their preferred habitats. A total of 289 fresh water snails of four different genera were collected across 27 streams in the 7 districts in Vandeikya LGA. Water pH, water temperature and water velocity were also measured. Lenistislibycuswas found to be the most abundant freshwater snail species accounting for 40.83% of the total freshwater snails. Melanoidestuberculata was the second most abundant accounting for 29.411% of the total snails population sampled, Biomphalaria pfeifferi accounted for 17.99% while Bulinus globosus was significantly lower in abundance than the other snails, accounting for only 11.77%. By location, Mbaduku district had highest abundance of snails 84 (29.1%). The effect of the nature of the substratum on the availability of freshwater snails revealed that habitats with rocky substratum favoured the presence of snails accounting for 181(62.7%) freshwater snail collected.Our understanding of factors affecting the availability and abundance of freshwater snails in nature can prove useful in snail control which is integral for the control of the diseases for which they serve as intermediate host.