Bulinus Globosus Research Articles

Molluscicidal Potential of Column Purified Fractions of Allium cepa against Intermediate Host of Urinary Schistosomiasis (Bulinus globosus) in Sokoto, Nigeria

Potential of column purified fractions of Allium cepa bulb against intermediate hosts of urinary schistosomiasis (Bulinus globosus) was conducted in laboratory condition. The fresh bulbs of A. cepa were purchased from Ramin Kura market of Sokoto, identified and authenticated by a taxonomist. The bulbs were sliced into pieces, air dried and powdered. Extracts were obtained using methanol as polar then purified with silica gel as a stationary phase while N-hexane and ethyl acetate (1:1) as the mobile phase. Thirteen fractions each fraction containing 10 ml of the effluent was collected, the collected extracts were left open for evaporation for 48 hours. Ten adult B. globosus were immersed in 3liters of water containing different concentrations of the fraction and each treatment was replicated three times with control in the same condition without treatment, observations were recorded after 24 hours up to 96 hours. The toxicity experiment showed that fractions (F7, F8, F6 and F9) were most toxic fractions, LC50 after 96 hours was 19.371 mg/l. based on findings from this research it can be concluded that, A. Cepa was very potent and can be used for control of B. globosus in order to prevent urinary schistosomiasis infection in endemic areas and drugs industries may use the extracts of these plants for production of molluscicides.

Distribution of fresh water snail intermediate host of trematode parasites in some fresh water bodies in Makurdi, Nigeria

The distribution of fresh water snail intermediate host of trematode parasites in an area is a bio-indicator of trematodiasis transmission in the locality. The distribution of some fresh water snail species in some fresh water bodies in Makurdi, Benue State, was carried out in four selected sites between June and September, 2016. It was aimed at determining the abundance of freshwater intermediate host of trematode parasites in the study-area. The scoop net method was employed with hand picking technique to collect snails, while morphological identification of snail was done using key in the Handbook of Danish Bilhaziasis Laboratory. Some physico-chemical parameters of water were also investigated at each site, 1,743 snails were collected. The distribution was: Melanoides tuberculate, 65.7%; Bulinus forskalii, 17.0%; Bulinus globosus,12.2%; Bulinus truncates, 4.5%; and Indoplanorbis exustus, 0.6 % respectively (x2 = 2422, df = 4, p<0.001). Snails distribution at various locations was: Ishwa Dam 71.4%; North Bank of River Benue 14.5%; Ityomu 7.9%; and Fete 6.1% (x2 = 1854, df = 12, p<0.001). The monthly distribution of the snail vectors also revealed a significant difference (x2 = 182, df = 9, p<0.001) in the snail species occurrence at the various sites. The population of the snails increased from June through September. This was accompanied by a decrease in the pH, biological oxygen demand (BOD) and dissolved oxygen (DO) in the water bodies, while temperature, turbidity and phosphate levels increased. This study has shown that there were significant intermediate hosts of Schistosoma haematobium, the causative agent of urinary schistosomiasis in the study area. Therefore, there is a need to undertake adequate snail control program and environmental sanitation awareness in the study area to curb the potential transmission of trematode parasitic diseases.Keywords: Fresh water; snail; intermediate host; trematode; physico-chemical parameters.

Prevalence of Schistosoma haematobium and Its Intermediate Hosts in Makurdi Metropolis

Introduction: Urinary Schistosomiasis (US) is a chronic water-borne infection caused by digenetic trematode belonging to the genus schistosoma, it is generally caused by Schistosoma haematobium. Bulinus globosus is a species of a tropical freshwater snail that acts as an intermediate host of Schistosoma haematobium. Aim: The study was aimed at ascertaining the prevalence of Schistosoma haematobium infection and to describe its intermediate hosts among school children in Makurdi.&#x0D; Methodology: Snails were collected by hand picking and scooping net methods. An epidemiological survey research on urinary Schistosomiasis was undertaken from September to November 2017 among students that volunteered in the selected schools within Makurdi metropolis. A total of 97 freshwater snails were collected and 200 urine samples involving pupils aged between 5 to 18 years were collected and analyzed for the eggs of Schistosoma haematobium by microscopy using Urine Syringe Filtration Technique (USFT). Statistical analysis was performed using SPSS 20. Chi-square test was used to determine the significant difference between variables.&#x0D; Results: Out of the 97 species of freshwater snails that were caught 41(42.3%) was Bulinus spp. Of the 200 urine samples analyzed, 49(24.5%) were found to be infected with ova of S. haematobium. The infection was higher among males 30(25.6%) than females 19(22.9%) although the difference was not statistically significant (χ2CAL=0.19, χ2TAB=3.84). The prevalence of Schistosoma haematobium infection among school children in relation to age showed that ages 15-19 years had the highest prevalence 13(38.2%) and ages 5-9 had the lowest prevalence 3(8.5%). The statistical analysis also revealed that there is no significant difference (8.302) in Schistosoma haematobium infection among the four schools in the study area. The presence of many snail species especially the Bulinus spp and increased contact time with the Schistosoma haematobium infested freshwater habitat was thought to be responsible for the prevalence of the disease in the area. Finding of this study shows that urinary Schistosomiasis was found to have a low prevalence in the area studied and there is the need to intensified integrated control measures to reduce or completely eradicate the disease.

Habitat suitability modelling for predicting potential habitats of freshwater snail intermediate hosts in Omo-Gibe river basin, Southwest Ethiopia

In spite of considerable progress made in the prevention and control of schistosomiasis and other snail-borne diseases, transmission has intensified in some endemic areas as a result of land-use and climate changes. We used decision tree models and multivariate analysis to identify factors affecting the occurrence and abundance of medically important freshwater snail intermediate hosts in the Omo-Gibe river basin, Ethiopia. The models were based on a dataset of 140 samples collected from lakes, wetlands, rivers, dam reservoir shores and irrigation canals. A total of 1866 freshwater snails belonging to four genera and seven species were collected. Biomphalaria pfeifferi, Lymnaea natalensis and Bulinus globosus had fair to moderate predictive performance based on Kappa statistics (ĸ > 0.2), indicating that these species have clear environmental requirements within the habitat gradient studied. The most important variables influencing the abundance and occurrence of snail species were the presence of predator and competitor, canopy cover, type of water body, waste dumping and water pH. In conclusion, snail species occurred less frequently and in smaller numbers in water bodies with minimal human disturbances. Therefore, preventing human disturbance in water bodies may enhance aquatic biodiversity, thereby increasing the abundance of snail predators and competitors. Preventing the pollution of these ecosystems is essential to maintain their ecological integrity and sustain the ecosystem services they provide to local communities.

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.

English

Bulinid snails act as intermediate host of schistosomes and the presence of the snail gives schistosomiasis an expansive characteristics. Schistosomiasis is of medical and veterinary importance in the tropical and subtropical regions. The shell shape and structure of radula teeth of bulinids are often specific to a species or genus, and are widely used for gastropod species identification. Bulinid species collected from schistosome endemic areas of Ogun State, South-western Nigeria were used for this study. Shell morphometrics were recorded using vernier caliper while the buccal mass of each snail was removed and permanent slides of the radulae were made according to standard procedure. There was a significant difference in the shell height, width, aperture height and aperture width between Bulinus globosus and Bulinus jousseaumei (p&lt;0.05). The average shell height measurement for B. globosus was 7.6&plusmn;1.9 mm, while B. jousseaumei measured 5.1&plusmn;1.6 mm. Each transverse row of B. globosus radula had a ratio of 26:8:1:8:26 while B. jousseaumei had a ratio of 25:8:1:8:25. The marginal teeth of B. globosus possessed five cusps while B. jousseaumei possessed six cusps. The differences observed in shell, radula ratio and cusps in both species could be used to differentiate both species.&nbsp; &nbsp; Key words: Radula, shell, Bulinus species, identification, Nigeria.

A survey of macroinvertebrate assemblage of Ikwu River, Umuahia, southeast Nigeria

Macroinvertebrate fauna of Ikwu River, Umuahia, Nigeria was studied in the 3 stations to evaluate the composition, abundance and distribution vis-a-vis environmental conditions and anthropogenic impacts. Macroinvertebrate fauna was sampled between January and June 2016 using the modified kick sampling technique as well as sweeping of aquatic macrophytes with hand net. A total of 168 macroinvertebrate individuals comprising of four benthic fauna group and seven (7) taxa was recorded. Percentage composition of the taxa showed that aquatic snail (Bulinus globosus) was the highest (55.36%) while water spider (Argyroneta aquatica) was the least (0.60%). Spatially, Station 3 recorded the highest number of individuals (116), followed by Station 1 (28 individuals) and Station 2 (24 individuals). Diversity assessment recorded higher Shannon-Weiner diversity index (H) in Station 1(0.8058) than in Stations 2 (0.4563) and 3 (0.6978). Magalef Species Richness was highest in Station 3 (0.8415), followed by Station 2 (0.6293) and Station 1 (0.6002). Evenness Index was highest in Station 1 (0.7462) and least in Station 3 (0.4019). The diversity indices, which were a reflection of the species composition, abundance and distribution, were equally poor.Keywords: Macroinvertebrates, environmental conditions, anthropogenic activities, water quality

Mapping freshwater snails in north-western Angola: distribution, identity and molecular diversity of medically important taxa

BackgroundThis study was designed to determine the distribution and identity of potential intermediate snail hosts of Schistosoma spp. in Bengo, Luanda, Kwanza Norte and Malanje Provinces in north-western Angola. This is an area where infection with Schistosoma haematobium, causing urogenital schistosomiasis, is common but little is yet known about transmission of the disease. Angola has had a varied past with regard to disease control and is revitalising efforts to combat neglected tropical diseases.MethodsSnails were sampled from 60 water-contact points. Specimens of the genera Bulinus, Biomphalaria or Lymnaea were screened for trematode infections by inducing cercarial shedding. Snails were initially identified using shell morphology; subsequently a cytochrome c oxidase subunit 1 (cox1) gene fragment was amplified from a subset of snails from each site, for molecular identification. Cercariae were captured onto FTA cards for molecular analysis. Specimens of Bulinus angolensis collected from the original locality of the type specimen have been characterised and comparisons made with snails collected in 1957 held at the Natural History Museum, London, UK.ResultsIn total snails of nine genera were identified using morphological characteristics: Biomphalaria, Bulinus, Gyraulus, Lanistes, Lentorbis, Lymnaea, Melanoides, Physa and Succinea. Significant for schistosomiasis transmission, was the discovery of Bulinus globosus, B. canescens, B. angolensis, B. crystallinus and Biomphalaria salinarum in their type-localities and elsewhere. Bulinus globosus and B. angolensis occurred in two distinct geographical areas. The cox1 sequence for B. globosus differed markedly from those from specimens of this species collected from other countries. Bulinus angolensis is more closely related to B. globosus than originally documented and should be included in the B. africanus group. Schistosoma haematobium cercariae were recovered from B. globosus from two locations: Cabungo, Bengo (20 snails) and Calandula, Malanje (5 snails). Schistosoma haematobium cercariae were identified as group 1 cox1 corresponding to the type common throughout the African mainland.ConclusionsVarious freshwater bodies in north-western Angola harbour potential intermediate snail hosts for urogenital schistosomiasis, highlighting the need to map the rest of the country to identify areas where transmission can occur and where control efforts should be targeted. The molecular phylogeny generated from the samples confirmed that considerable variation exists in B. globosus, which is the primary snail host for S. haematobium in many regions of Africa.

Effect of temperature on the Bulinus globosus \u2014 Schistosoma haematobium system

BackgroundGiven that increase in temperature may alter host-parasite relationships, the anticipated rise in temperature due to global warming might change transmission patterns of certain diseases. However, the extent to which this will happen is not well understood.MethodsUsing a host-parasite system involving Bulinus globosus and Schistosoma haematobium, we assessed the effect of temperature on snail fecundity, growth, survival and parasite development under laboratory conditions.ResultsOur results show that temperature may have a non-linear effect on snail fecundity and snail growth. Snails maintained at 15.5 °C and 36.0 °C did not produce egg masses while those maintained at 25.8 °C laid 344 and 105 more egg masses than snails at 31.0 °C and 21.2 °C, respectively. Attainment of patency led to a reduction in egg mass production among the snails. However, the reduction in fecundity for snails maintained at 21.2 °C occurred before snails started shedding cercariae. Parasite development was accelerated at high temperatures with snails maintained at 31.0 °C reaching patency after three weeks. Furthermore, snail growth rate was highest at 25.8 °C while it was inhibited at 15.5 °C and reduced at 31.0 °C. Increase in temperature increased snail mortality rates. Snails maintained at 36.0 °C had the shortest survival time while those maintained at 15.5 °C had the longest survival time.ConclusionsWe concluded that temperature influences fecunxdity, growth, survival and parasite development in the snail and thus dictates the time it takes the parasite to complete the life cycle. This has implications on transmission of schistosomiasis in the context of global warming.

Ecology and distribution of gastropod snails of medical and veterinary importance in Municipal Area Council, FCT, Abuja

A study on the ecology and distribution of snails of medical importance was conducted in water bodies from four different communities (Old Karmo, Gwagwa, Deidei I and Deidei II) in Abuja Municipal Area Council, FCT, Abuja, Nigeria. Three species of snails; Bulinus globosus, Lymnaea natalensis and Melanoides tuberculata were identified. The total number and percentage of snails collected from the four sites were 309. Comprising of 56 (18.12%) from Old Karmo, 115 (37.22%) from Gwagwa, 78 (25.24%) from Deidei (I) and 60 (19.42%) from Deidei (II) respectively. Gwagwa and Deidei (I) recorded the predominant number of species encountered in the study. The following floras were identified from the study-sites; Megathyrsus maximus, Guinea grass and Commelina nigritana (African dayflower) were identified from the sampled water bodies. Findings indicate that favourable conditions exist in Abuja Municipal Area Council that supports the breeding of the snails which are intermediate hosts of medical/ veterinary importance under suitable physicochemical parameters which determines the extent of their population and distribution in the area.Keywords: Ecology; snails; schistosomiasis; physico-chemical parameters; freshwater

Divergent Effects of Schistosoma haematobium Exposure on Intermediate-Host Snail Species Bulinus nasutus and Bulinus globosus from Coastal Kenya.

AbstractSchistosoma haematobium infection causes urogenital schistosomiasis, a chronic inflammatory disease that is highly prevalent in many parts of sub-Saharan Africa. Bulinid snails are the obligate intermediate hosts in the transmission of this parasite. In the present study, Bulinus globosus and Bulinus nasutus snails from coastal Kenya were raised in the laboratory and exposed to miracidia derived from sympatric S. haematobium specimens to assess the species-specific impact of parasite contact and infection. The snails' subsequent patterns of survival, cercarial shedding, and reproduction were monitored for up to 3 months postexposure. Schistosoma haematobium exposure significantly decreased the survival of B. globosus, but not of B. nasutus. Although both species were capable of transmitting S. haematobium, the B. globosus study population had a greater cumulative incidence of cercarial shedders and a higher average number of cercariae shed per snail than did the B. nasutus population. The effects of prior parasite exposure on snail reproduction were different between the two species. These included more numerous production of egg masses by exposed B. nasutus (as compared with unexposed snails), contrasted to decreased overall egg mass production by parasite-exposed B. globosus. The interspecies differences in the response to and transmission of S. haematobium reflect clear differences in life histories for the two bulinid species when they interact with the parasite, which should be taken into account when planning control interventions aimed at reducing each host snails' contribution to local transmission of Schistosoma infection.

Influence of physico-chemical parameters on the intermediate host of Schistosoma haematobium and Schistosoma mansoni in Makwaye and Kubanni Reservoirs, Zaria, Nigeria

Objective: This research was conducted to determine the influence of physico-chemical characteristics on diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria. Materials and methods: Physico-chemical characteristics and diversity of the intermediate host of schistosomes in Makwaye and Kubanni reservoirs, Zaria, Nigeria, were investigated for a 12-month period (January to December, 2014). Physico-chemical properties were analyzed according to the standard procedures for examination of water and waste waters. The molluscs were collected using an Ekman grab model number 923, measuring 19 cm by 14 cm with an area of 0.0266 m2. PAST software was used to run Principal Component Analysis, Shanon-Weiner diversity index and Cluster analysis. Results: A total of 978 Bulinus globosus and 3612 Biomphalaria pfefferi were recorded in Makwaye reservoir with high abundance in dry season while a total of 163 B. globosus and 602 B. pfefferi was recorded in Kubanni reservoir with higher abundance in wet season. Shanon-Weiner diversity index of Makwaye reservoir also ranged from 2.01-2.22 and 1.16-1.31 in Kubanni reservoir. Significant variations (P≤0.05) were observed in physicochemical parameters, schistosomes intermediate host abundance with seasons. Principal Component Analysis (PCA) revealed significant influence (P≤0.05) of physicochemical properties on schistosome intermediate host composition, with BOD, DO, pH and Calcium significantly influencing the presence of B. globosus and B. pfefferi in both reservoirs. Conclusion: It is concluded that the presence of these molluscs in the study areas may constitute a predisposing factor to schistosomiasis and therefore, various management strategies and recommend preventive measures to people coming in contact with these two reservoirs.

Urogenital schistosomiasis transmission on Unguja Island, Zanzibar: characterisation of persistent hot-spots.

BackgroundElimination of urogenital schistosomiasis transmission is a priority for the Zanzibar Ministry of Health. Preventative chemotherapy together with additional control interventions have successfully alleviated much of the disease burden. However, a persistently high Schistosoma haematobium prevalence is found in certain areas. Our aim was to characterise and evaluate these persistent “hot-spots” of transmission and reinfection in comparison with low-prevalence areas, to support the intervention planning for schistosomiasis elimination in Zanzibar.MethodsPrevalences of S. haematobium were annually determined by a single urine filtration in schoolchildren from 45 administrative areas (shehias) in Unguja in 2012, 2013 and 2014. Coverage data for biannual treatment with praziquantel were available from ministerial databases and internal surveys. Among the 45 shehias, five hot-spot (≥ 15 % prevalence) and two low-prevalence (≤ 5 %) shehias were identified and surveyed in mid-2014. Human-water contact sites (HWCSs) and the presence of S. haematobium-infected and uninfected Bulinus globosus, as well as safe water sources (SWSs) and their reliability in terms of water availability were determined and mapped.ResultsWe found no major difference in the treatment coverage between persistent hot-spot and low-prevalence shehias. On average, there were considerably more HWCSs containing B. globosus in hot-spot than in low-prevalence shehias (n = 8 vs n = 2) and also more HWCSs containing infected B. globosus (n = 2 vs n = 0). There was no striking difference in the average abundance of SWSs in hot-spot and low-prevalence shehias (n = 45 vs n = 38) and also no difference when considering SWSs with a constant water supply (average: 62 % vs 62 %). The average number of taps with a constant water supply, however, was lower in hot-spot shehias (n = 7 vs n = 14). Average distances from schools to the nearest HWCS were considerably shorter in hot-spot shehias (n = 229 m vs n = 722 m).ConclusionThe number of HWCSs, their infestation with B. globosus and their distance to schools seem to play a major role for a persistently high S. haematobium prevalence in children. In addition to treatment, increasing access to reliably working taps, targeted snail control at HWCSs near schools and enhanced behaviour change measures are needed to reduce prevalences in hot-spot areas and to finally reach elimination.Trial registration ISRCTN48837681.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1847-0) contains supplementary material, which is available to authorized users.

Modelling the spatial and seasonal distribution of suitable habitats of schistosomiasis intermediate host snails using Maxent in Ndumo area, KwaZulu-Natal Province, South Africa.

BackgroundSchistosomiasis is a snail-borne disease endemic in sub-Saharan Africa transmitted by freshwater snails. The distribution of schistosomiasis coincides with that of the intermediate hosts as determined by climatic and environmental factors. The aim of this paper was to model the spatial and seasonal distribution of suitable habitats for Bulinus globosus and Biomphalaria pfeifferi snail species (intermediate hosts for Schistosoma haematobium and Schistosoma mansoni, respectively) in the Ndumo area of uMkhanyakude district, South Africa.MethodsMaximum Entropy (Maxent) modelling technique was used to predict the distribution of suitable habitats for B. globosus and B. pfeifferi using presence-only datasets with ≥ 5 and ≤ 12 sampling points in different seasons. Precipitation, maximum and minimum temperatures, Normalised Difference Vegetation Index (NDVI), Normalised Difference Water Index (NDWI), pH, slope and Enhanced Vegetation Index (EVI) were the background variables in the Maxent models. The models were validated using the area under the curve (AUC) and omission rate.ResultsThe predicted suitable habitats for intermediate snail hosts varied with seasons. The AUC for models in all seasons ranged from 0.71 to 1 and the prediction rates were between 0.8 and 0.9. Although B. globosus was found at more localities in the Ndumo area, there was also evidence of cohabiting with B. pfiefferi at some of the locations. NDWI had significant contribution to the models in all seasons.ConclusionThe Maxent model is robust in snail habitat suitability modelling even with small dataset of presence-only sampling sites. Application of the methods and design used in this study may be useful in developing a control and management programme for schistosomiasis in the Ndumo area.

Diversity, distribution and abundance of freshwater snails in Eleyele dam, Ibadan, south-west Nigeria

AbstractFreshwater molluscs help in the assessment of the ecological status of water bodies and also play significant roles in the public and veterinary health. Hence, scientific studies pertaining to their diversity, distribution and abundance become essential. In Eleyele dam, freshwater snails were sampled and physicochemical parameters of the water body were analysed fortnightly using standard methods from May to October 2013. Plant species distribution and abundance, bottom sediment types were also identified. A total of 2230 freshwater snails were collected. The snail species, total number and relative abundance were: Melanoides tuberculata 450 (20.18%), Potadoma liberiensis 301 (13.49%), Biomphalaria pfeifferi 37 (1.66%), Indoplanorbis exutus 456 (20.45%), Bulinus globosus 18 (0.81%), Gabbiella africana 53 (2.38%), Lymnaea natalensis 386 (17.31%), and Physa marmorata 529 (23.72%). 4 out of these 8 species are of medical importance. The study revealed that the density of freshwater snails varied mont...

Schistosoma haematobium co-infection with soil-transmitted helminthes: prevalence and risk factors from two communities in the central region of Ghana

Background : Schistosoma haematobium co-infection with S. mansoni and soil-transmitted helminthes afflict most-at-risk populations in endemic communities in the developing world. Aim : This study investigated S. haematobium co-infection with soil-transmitted helminthes, and host risk factors in two communities in the central region of Ghana. Methods: Schools and children were selected by stratified cluster and random sampling methods respectively. A total of 250 school children (aged 5 - > 20 years) were recruited. Teachers issued questionnaires to obtain information on host risk factors, water-contact activities and knowledge of S. haematobium infection. Urine and stool samples were examined for S. haematobium infection and S. mansoni and soil-transmitted helminthes using sedimentation quantitative and direct smear/formol-ether sedimentation concentration techniques respectively. Results : S. haematobium infection (1 - 50 eggs/10 ml urine) prevalence at Apewosika and Putubiw were 27.5 % and 17 % respectively. Males were more at risk of S. haematobium infection than females. S. haematobium co-infection with soil-transmitted helminthes ( A. lumbricoides, E. histolytica, and T. trichuria ) was recorded in Putubiw, with females more at risk than males. Children aged 16-19 and 10-15 were more at risk of S. haematobium infection and helminthic co-infection respectively. Haematuria and proteinuria were predictive of S. haematobium infection. School children had poor knowledge of S. haematobium infection. Water-contact activity was common. Conclusion : S. haematobium prevalence and its co-infection with soil-transmitted helminthes were common in Putubiw. Watercontact activity and poor knowledge about S. haematobium infection were major risk factors. Increased education on preventive and control measures especially in schools is recommended. Key words : Haematuria, proteinuria, Schistosoma haematobium, S. mansoni, helminthes, Bulinus globosus

Population genetic structure of the freshwater snail, Bulinus globosus, (Gastropoda: Planorbidae) from selected habitats of KwaZulu-Natal, South Africa

The freshwater snail Bulinus globosus is an important intermediate host of Schistosoma haematobium, the causative agent of urinary schistosomiasis. This disease is of major health concern, especially in Africa where the majority of cases have been reported. In this study the inter- and intra-genetic diversity and population genetic structure of B. globosus from nine locations in the KwaZulu-Natal province of South Africa was studied using four polymorphic microsatellite loci (BgZ1–BgZ4). Moderate genetic diversity was detected within populations with a mean diversity (HE) of 0.49±0.09. The majority of populations significantly deviated from Hardy-Weinberg equilibrium (p<0.05), due to a deficit of heterozygotes. Such deviations may be due to founder events that were caused by bottlenecks that occurred as a result of frequent droughts and flooding that these snails’ habitats are exposed to. Overall, the populations studied seem to be partially inbreeders/selfers with mean estimates of 0.24/0.38. A discernable genetic structure was elucidated among populations as evident by the mean pairwise FST of 0.58±0.13. There was no significant association between genetic and geographical distance among populations, an indication of limited gene flow. This increases the chances of populations losing alleles due to genetic drift. Populations in close proximity demonstrated high genetic differentiation (58.77% total variation) due to allelic differences between them. The sample populations fell into 12 clusters, however, the populations from uMkhanyakude and uThungulu exhibited no discernable genetic structure. Genetically, the Bhobhoyi site found within the uGu district was equidistant to the two main sampling regions.

Urinary schistosomiasis among preschool children in Malengachanzi, Nkhotakota District, Malawi: Prevalence and risk factors.

This study was designed to determine the prevalence of and risk factors for schistosomiasis among a group of preschool children in Malawi. Schistosomiasis burden among preschoolers in Malawi is not well documented in the literature. This study used field research (in the form of a snail survey), laboratory work (urinalysis and microscopy for parasite identification), and questionnaire-guided interviews to determine the prevalence of and risk factors for urinary schistosomiasis among children, aged between 6 and 60 months, in Malengachanzi, Nkhotakota District, Malawi. Urinary schistosomiasis prevalence among preschool children was 13%. Of the factors evaluated, only age (P = 0.027) was statistically significantly associated with urinary schistosomiasis risk. Four-year-old preschool children were five times more likely to contract urinary schistosomiasis than twoyear-old children (odds ratio [OR] = 5.255; 95% confidence interval [CI] = 1.014-27.237; P = 0.048). Increased contact with infested water among older children likely explains much of their increased risk. Infestation was evidenced by the presence of infected Bulinus globosus snails in the water contact points surveyed. Multiple regression analysis showed that visiting water contact sites daily (OR = 0.898, 95% CI = 0.185-4.350, P = 0.894), bathing in these sites (OR = 9.462, 95% CI = 0.036-0.00, P = 0.430) and lack of knowledge, among caregivers, regarding the causes of urinary schistosomiasis (OR = 0.235, 95% CI = 0.005-1.102, P = 0.066) posed statistically insignificant risk increases for preschoolers contracting urinary schistosomiasis. Urinary schistosomiasis was prevalent among preschool children in Malengachanzi, Nkhotakota District. Contact with infested water puts these children and the general population at risk of infection and reinfection. Inclusion of preschool children in treatment programmes should be considered imperative, along with safe treatment guidelines. To prevent infection, the population in the area should be provided with health education and safe alternative water sources.

Effects of Endosulfan on Predator-Prey Interactions Between Catfish and Schistosoma Host Snails.

The effect of the pesticide endosulfan on predator–prey interactions between catfish and Schistosoma host snails was assessed in static tank experiments. Hybrid catfish (Clarias gariepinus × C. ngamensis) and Bulinus globosus were subjected to various endosulfan concentrations including an untreated control. The 48- and 96-h LC50 values for catfish were 1.0 and <0.5 µg/L, respectively, whereas the 48- and 96-h LC50 values for snails were 1137 and 810 µg/L. To assess sublethal effects on the feeding of the catfish on B. globosus, endosulfan concentrations between 0.03 and 1.0 µg/L were used. Predation was significantly greater (p < 0.001) in control tanks than in all other treatments. There was progressively decreasing predation with increasing toxicant concentration. Biological control of Schistosoma host snails using fish may be affected in endosulfan-polluted aquatic systems of Southern Africa because it has been found present at concentrations that are indicated to cause lethal effects on the evaluated hybrid catfish and to inhibit the predation of snails by this hybrid catfish.Electronic supplementary materialThe online version of this article (doi:10.1007/s00244-016-0275-7) contains supplementary material, which is available to authorized users.

Cercarial shedding of trematodes and their associated snail intermediate hosts in Borno State, Nigeria

ObjectiveTo determine the distribution of cercariae of trematodes and their associated snail intermediate hosts in Borno State, Nigeria. MethodsHandpicking and scooping by the aid of scoop nets were used to collect a total of 1 700 snails. They were examined for cercarial release using emergent method of cercarial release. Results16 (0.94%) of the 1 700 snails were positive for cercariae of trematodes based on morphology and standard measurement. Three species (Bulinus forskalli, Bulinus globosus and Lymnae natalensis) of snails were identified based on shell morphology and standard criteria. Distribution of the infection among the sampled snails showed that, 10 (1.75%) of Bulinus globosus and 6 (0.55%) of Lymnae natalensis released cercariae of Schistosoma haematobium and a distome cercaria of Fasciola spp. respectively. The intensity of infection among the examined snails varied significantly (P<0.05) based on senatorial zones of sampling. ConclusionsThe present study has demonstrated the presence of some important trematodes and snail species that are possible intermediate hosts in Borno State. This study will further provide insight into better understanding of the epidemiology of schistosomiasis caused by Schistosoma haematobium and other trematodes and the role of snails (Bulinus globosus and Lymnae natalensis) as intermediate hosts.