Transmission Of Human Schistosomiasis Research Articles

Insights from the shotgun-based proteomics analysis of Biomphalaria glabrata.

Biomphalaria glabrata is an important host in the transmission of human schistosomiasis in the Caribbean and South America. Therefore, it is of interest to analyse the proteome data of Biomphalaria glabrata hemolymph to identify immunity related proteins in host-pathogen relationship. We used shotgun proteomic and bioinformatic analyses of the non-depleted and depleted [0.5 and 0.75% Trifluoroacetic acid (TFA) depletion] hemolymph of B. glabrata (LE strain). Analysis showed 148 proteins from the hemolymph. 148 were obtained from the 0.5% TFA-depleted sample. 62 proteins follow this from the 0.75% TFA-depleted sample. However, only 59 were found from non-depleted hemolymph. A number of proteins were identified from the hemolymph of this schistosomiasis snail vector linked to immunity related functions. This provides insights to the understanding of schistosome-snail interaction.

Schistosomiasis in the Senegal River basin

Schistosomiasis in the Senegal River basin

Role of environmental parameters on the density of intermediate host snails of human schistosoma during the year in the commune of Richard-Toll, Senegal

The implementation and expansion of development projects (dams and irrigation schemes) in the Senegal River valley have led to a significant proliferation of snails. We conducted a one-year (2014) study project, monitoring their density in the commune of Richard Toll, to assess the role of environmental parameters on mollusc population dynamics. Four species involved in the transmission of human schistosomiasis were found: Bulinus globosus, B. truncatus, B. senegalensis, and Biomphalaria pfeifferi. Among the intermediate hosts, B. truncatus is the most abundant species, followed by B. globosus. Snail density depends on the nature of the water point but also on environmental parameters such as vegetation. This study showed that vegetation, water level (flood), and flow velocity influence the dynamics of the snail populations that are intermediate hosts of human schistosomes.

Prevalence and seasonal transmission of Schistosoma haematobium infection among school-aged children in Kaedi town, southern Mauritania

BackgroundMauritania is at the fringe of transmission of human schistosomiasis, which mainly occurs in the southern and southeastern parts of the country. This study aimed to assess the influence of rainfall seasonality on the prevalence of Schistosoma haematobium infection among school-aged children in Kaedi, southern Mauritania.MethodsCross-sectional surveys (i.e. parasitological, malacological and observations on water-related human activities) were carried out in Kaedi between September 2014 and May 2015, during both the wet and dry seasons. A total of 2162 children aged 5–15 years provided a single urine sample that was subjected to S. haematobium diagnosis. Snails were sampled and checked for cercarial shedding. Water contact patterns of the local population were recorded by direct observation.ResultsThe prevalence of S. haematobium was 4.0% (86/2162, 95% confidence interval (CI): 3.2–4.9%) with a geometric mean egg count per 10 ml of urine of 3.7 (95% CI: 2.8–4.3). Being male (adjusted odds ratio (aOR) 1.78, 95% CI: 1.13–2.80), being at primary school (aOR 1.73, 95% CI: 1.04–2.87) and dry season (aOR 0.56, 95% CI: 0.35–0.89) were significantly associated with S. haematobium. Among 284 potential intermediate host snail specimens collected over the rainy and dry seasons, three species were identified: Bulinus senegalensis (n = 13) and B. forskalii (n = 161) in the rainy season, and B. truncatus (n = 157) in the wet season. No snail was shedding cercariae. On average, seven human water contacts were recorded per hour per observer over a 28-day observation period. Twelve types of water contact activities were identified among which, swimming/bathing was predominant (n = 3788, 36.9%), followed by washing clothes (n = 2016, 19.7%) and washing dishes (n = 1322, 12.9%). Females (n = 5270, 51.4%) were slightly more in contact with water than males (n = 4983, 48.6%). The average time spent in the water per person per day was 14.2 min (95% CI: 13.8–14.6 min). The frequency and duration of water contact followed a seasonal pattern.ConclusionOur findings demonstrate a low prevalence and intensity of S. haematobium among school-aged children in Kaedi. Appropriate integrated control measures, including health education among at-risk communities and snail control may help to interrupt transmission of S. haematobium in Kaedi.

Spatio-temporal correlation between human and bovine schistosomiasis in China: insight from three national sampling surveys

Insight into the spatial and temporal contamination of the environment by bovine faeces in China can provide important information on the significance of bovines in the transmission of human schistosomiasis. This insight will be useful for the new evidence-based strategy of the Chinese national schistosomiasis control programme. To enhance our understanding of the spatio-temporal relationship between the prevalence of human and bovine schistosomiasis, we performed correlation and regression analyses using data from three national sampling surveys on schistosomiasis, carried out in 1989, 1995 and 2004. In addition, we established a geographical information system and performed spatial analyses to identify the high-risk areas of the disease. We found that schistosomiasis is mainly concentrated in the marshlands along the Yangtze River. It was also noted that, although the human prevalence and force of transmission in highly endemic areas has been reduced since 1989, the relative importance of bovine schistosomiasis has increased. This is seen in a declining Spearman correlation coefficient between the infection prevalence in humans and in bovines over time (0.812 in 1989, 0.754 in 1995 and 0.376 in 2004). In parallel, the slope of the linear regression decreased from 0.395 in 1989 to 0.215 in 2004. Our data therefore suggest that future schistosomiasis control efforts in China should more vigorously address the important role of bovines in the transmission of human schistosomiasis, and to reduce the environmental contamination of Schistosoma japonicum eggs by bovines.

Nimbus (BgI): An active non-LTR retrotransposon of the Schistosoma mansoni snail host Biomphalaria glabrata

The freshwater snail Biomphalaria glabrata is closely associated with the transmission of human schistosomiasis. An ecologically sound method has been proposed to control schistosomiasis using genetically modified snails to displace endemic, susceptible ones. To assess the viability of this form of biological control, studies towards understanding the molecular makeup of the snail relative to the presence of endogenous mobile genetic elements are being undertaken since they can be exploited for genetic transformation studies. We previously cloned a 1.95kb BamHI fragment in B. glabrata (BGR2) with sequence similarity to the human long interspersed nuclear element (LINE or L1). A contiguous, full-length sequence corresponding to BGR2, hereafter-named nimbus (BgI), has been identified from a B. glabrata bacterial artificial chromosome (BAC) library. Sequence analysis of the 65,764bp BAC insert contained one full-length, complete nimbus (BgI) element (element I), two full-length elements (elements II and III) containing deletions and flanked by target site duplications and 10 truncated copies. The intact nimbus (BgI) contained two open-reading frames (ORFs 1 and 2) encoding the characteristic hallmark domains found in non-long terminal repeat retrotransposons belonging to the I-clade; a nucleic acid binding protein in ORF1 and an apurinic/apyrimidinic endonuclease, reverse transcriptase and RNase H in ORF2. Phylogenetic analysis revealed that nimbus (BgI) is closely related to Drosophila (I factor), mosquito Aedes aegypti (MosquI) and chordate ascidian Ciona intestinalis (CiI) retrotransposons. Nimbus (BgI) represents the first complete mobile element characterised from a mollusk that appears to be transcriptionally active and is widely distributed in snails of the neotropics and the Old World.

A baseline study of importance of bovines for human Schistosoma japonicum infections around Poyang Lake, China: villages studied and snail sampling strategy.

An epidemiologic survey among four administrative villages around Poyang Lake, in Jiangxi Province, China (two experimental and two controls) is being conducted to determine if bovine infections are responsible for the persistence of human schistosomiasis transmission on Yangtze River marshlands. A previously published paper presented the experimental design and baseline data for humans and bovines. This paper presents basic data for the four villages using remote sensing, and baseline data for snails that includes geographic information systems and remote sensing technology to classify the areas of bovine grazing ranges and habitats suitable for snails. A new method for sampling Oncomelania snails in China is used to determine the distribution, density, and infection rates of snails throughout the grazing ranges from season to season over a four-year period. Hypothetically, treating bovines should reduce infection rates in snails to below the critical number necessary to maintain infections in man and bovines.

Endemicity, focality and seasonality of transmission of human schistosomiasis in Amagunze Village, eastern Nigeria

The pattern of transmission of human schistosomiasis was studied in Amagunze Village, eastern Nigeria, during 1986-1987. The prevalence of Schistosoma haematobium in 119 schoolboys aged 5-12 years was 79%. The geometric mean of intensity of infection was 49 eggs/10 ml urine and the frequency of visible haematuria was 25.2%. No S. mansoni infections were demonstrated. A marked seasonality in population density of Bulinus truncatus, B. forskalii and Biomphalaria pfeifferi was demonstrated with reduced densities during the late rainy and early dry seasons. Schistosoma sp. infected B. truncatus were found in the late dry and early rainy seasons in 2 out of 7 major human water contact sites studied. Seasonality and focality of transmission of S. haematobium and its high endemicity in the area were thus demonstrated.

A new species ofBulinus(Mollusca: Gastropoda) from temporary freshwater pools in Kenya

Summary A description is given of Bulinus hightoni, a new species of freshwater snail belonging to the B. africanus (Krauss) group (Mollusca: Gastropoda: Planorbidae). The new species is known from seasonal pools in the lower Tana river region of northeast Kenya. Information is given about morphological characters, and biological features studied in a laboratory-bred colony, including egg proteins, enzymes and susceptibility to Schistosoma haematobium. B. hightoni is remarkably small for the B. africanus group and lacks the characteristic renal ridge, but the immunological responses of its egg proteins support its classification in this group. It is concluded that B. hightoni is not related particularly closely to other species which display unusual characters for the B. africanus group. B. hightoni is susceptible to infection with a variety of terminal-spined schistosomes including S. haematobium. Its possible role in transmission of human schistosomiasis (Bilharziasis) is discussed.