Schistosomiasis is a public health concern in Benin. Freshwater snails of the genus Bulinus serve as intermediate hosts for schistosomes, trematode parasites responsible for bilharzia. The urinary form, caused by Schi...Schistosomiasis is a public health concern in Benin. Freshwater snails of the genus Bulinus serve as intermediate hosts for schistosomes, trematode parasites responsible for bilharzia. The urinary form, caused by Schistosoma haematobium, is the most widespread and is transmitted to humans by these mollusks, with Bulinus truncatus and Bulinus globosus being the most important species. Effective strategies to combat the transmission of these parasites require a prior understanding of the molecular characterization of Bulinus snails. For this purpose, 293 Bulinus snails were collected and morphologically identified from two localities in southern Benin, Sô-Ava and Azowlissè. The snails were preserved in absolute alcohol. To achieve the set objectives, DNA was extracted from the collected biological material, and SSU gene fragments were amplified. Using PCR-RFLP, the amplified fragments were digested with the restriction endonucleases HaeIII, HinfI, and DdeI to perform molecular characterization. In this study, 80 individuals of B. globosus and 10 of B. truncatus were subjected to molecular analysis. The PCR-RFLP profiles showed bands of different sizes for the Bulinus species when analyzed with the three endonucleases using the SSU molecular marker. PCR-RFLP analysis revealed that the snails belonged to the freshwater genus Bulinus, including Bulinus globosus and B. truncatus, based on reference profiles from studies conducted in Nigeria, which enabled precise identification of these gastropods. This study provided initial insights, although still incomplete, into the molecular diversity of these species.展开更多
The effects of sublethal concentrations of methanol extract of sesbania sesban plant on survival rate, egg laying of Bulinus truncatus snails, hatchability of their eggs, infection rate with Schistosoma haemato- bium ...The effects of sublethal concentrations of methanol extract of sesbania sesban plant on survival rate, egg laying of Bulinus truncatus snails, hatchability of their eggs, infection rate with Schistosoma haemato- bium miracidia, cercarial production and certain physiological parameters of treated snails were stu- died. The sublethal concentrations of the tested plant extract (LC0, LC10 and LC25) caused considerable reduction in survival rates;egg production of B. runcates snails;hatchability of eggs as well as in the infectivity of Schistosoma haematobium miracidia to the snail. Also, the tested concentrations reduced the cercarial production per snail and the period of cer-carial shedding. The glucose level in haemolymph of exposed snails was elevated while the glycogen, pro-tein content and the activities of hexokinase (HK), pyruvatekinase (PK) and lactate dehydrogenase (LDH) showed a decrease in soft tissues when compared with the control group. It was concluded that the app lication of sublethal concentration of methanol ex- tracts of Sesania sesban may be helpful in snail con- trol as it interferes with the snails’ biology and phy- siology.展开更多
Background Freshwater snails of the genera Bulinus spp.,Biomphalaria spp.,and Oncomelania spp.are the main intermediate hosts of human and animal schistosomiasis.Identification of these snails has long been based on m...Background Freshwater snails of the genera Bulinus spp.,Biomphalaria spp.,and Oncomelania spp.are the main intermediate hosts of human and animal schistosomiasis.Identification of these snails has long been based on mor-phological and/or genomic criteria,which have their limitations.These limitations include a lack of precision for the morphological tool and cost and time for the DNA-based approach.Recently,Matrix-Assisted Laser Desorp-tion/lonization Time-Of-Flight(MALDI-TOF)mass spectrometry,a new tool used which is routinely in clinical microbi-ology,has emerged in the field of malacology for the identification of freshwater snails.This study aimed to evaluate the ability of MALDI-TOF MS to identify Biomphalaria pfeifferi and Bulinus forskali snail populations according to their geographicalorigin.Methods This study was conducted on 101 Bi.pfeifferi and 81 Bu.forskali snails collected in three distinct geo-graphical areas of Senegal(the North-East,South-East and central part of the country),and supplemented with wild and laboratory strains.Specimens which had previously been morphologically described were identified by MALDl-TOF MS[identification log score values(LSV)≥1.7],after an initial blind test using the pre-existing database.After DNA-based identification,new reference spectra of Bi.pfeiferi(n=10)and Bu.forskali(n=5)from the geographical areas were added to the MALDI-TOF spectral database.The final blind test against this updated database was per-formed to assess identification at the geographic source level.Results MALDI-TOF MS correctly identified 92.1%of 101 Bi.pfeifferi snails and 98.8%of 81 Bu.forskali snails.At the final blind test,88%of 166 specimens were correctly identified according to both their species and sampling site,with LSVs ranging from 1.74 to 2.70.The geographical source was adequately identified in 90.1%of 91 Bi.pfeifferi and 85.3%of 75 Bu.forskalii samples.Conclusions Our findings demonstrate that MALDI-TOF MS can identify and differentiate snail populations according to geographical origin.It outperforms the current DNA-based approaches in discriminating laboratory from wild strains.This inexpensive high-throughput approach is likely to further revolutionise epidemiological studies in areas which are endemic for schistosomiasis.展开更多
Background:Given 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 t...Background:Given 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.Methods:Using 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.Results:Our results show that temperature may have a non-linear effect on snail fecundity and snail growth.Snails maintained at 15.5℃ and 36.0℃ did not produce egg masses while those maintained at 25.8℃ laid 344 and 105 more egg masses than snails at 31.0℃ and 21.2℃,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℃ occurred before snails started shedding cercariae.Parasite development was accelerated at high temperatures with snails maintained at 31.0℃ reaching patency after three weeks.Furthermore,snail growth rate was highest at 25.8℃ while it was inhibited at 15.5℃ and reduced at 31.0℃.Increase in temperature increased snail mortality rates.Snails maintained at 36.0℃ had the shortest survival time while those maintained at 15.5℃ had the longest survival time.Conclusions:We 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.展开更多
Background: Bulinus globosus,the main intermediate snail host of Schistosoma haematobium.The increased contacts between Africa and China could even lead to large-scale dissemination of B.globosus in China.Temperature ...Background: Bulinus globosus,the main intermediate snail host of Schistosoma haematobium.The increased contacts between Africa and China could even lead to large-scale dissemination of B.globosus in China.Temperature is the key factor affecting fresh-water snail transmission.This study predicted potential risk of colonization of B.globosus in the mainland of China under climate change.Methods: We investigated minimum and maximum temperatures for B.globosus eggs,juveniles and adult snails kept under laboratory conditions to find the most suitable range by pinpointing the median effective temperatures(ET50).We also assessed the influence of temperature on spawning and estimated the accumulated temperature(AT).The average air temperatures between 1955 and 2019 in January and July,the coldest and hottest months in China,respectively,were collected from national meteorological monitoring stations and investigated in a geographic information system(GIS)using empirical Bayesian Kriging to evaluate the theoretical possibility for distribution of B.globosus in southern China based on temperature.Results: The effective minimum temperature(ET50min)for eggs,juveniles,adult snails and spawning were 8.5,7.0,7.0,14.9℃,respectively,with the corresponding maximum values(ET50max)of 36.6,40.5,40.2 and 38.1℃.The AT was calculated at 712.1±64.9℃·d.In 1955,the potential B.globosus distribution would have had a northern boundary stretching from the coastal areas of Guangdong Province and Guangxi Autonomous Region to southern Yunnan Province.Since then,this line has gradually moved northward.Conclusions: Annual regeneration of B.globosus can be supported by the current climate conditions in the mainland of China,and a gradual expansion trend from south to north is shown in the study from 2015 to 2019.Thus,there is a potential risk of colonization of B.globosus in the mainland of China under climate change.展开更多
Background:Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis.Some plant extracts have shown obvious molluscicidal activity,and...Background:Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis.Some plant extracts have shown obvious molluscicidal activity,and a new compound Luo-Wei,also named tea-seed distilled saponin(TDS),was developed based on the saponins extracted from Camellia oleifera seeds.We aimed to test the molluscicidal activity of 4%TDS against the intermediate host snails in China and Egypt,and evaluate its environmental safety to non-target organisms.Methods:In the laboratory,Oncomelania hupensis,Biomphalaria alexandrina and Bulinus truncatus were exposed to 4%TDS,and the median lethal concentration(LC5o)was estimated at 24,48 and 72 h.In the field,snail mortalities were assessed 1,2,3 and 7 d post-immersion with 2.5 g/m34%TDS and 1,3,7 and 15 d post-spraying with 5 g/m24%TDS.in addition,the acute toxicity of 4%TDS to Japanese quail(Coturnixjaponica),zebrafish(Brachydanio rerio)and freshwater shrimp(Macrobrachium nipponense)was assessed by estimations of LC5o or median lethal dose(LD5o).Results:In the laboratory,the LC5o values of 4%TDS for O.hupensis were 0.701,0.371 and 0.33 mg/L at 24,48 and 72 h,respectively,and 4%TDS showed a 0.33 mg/L 24 h LC5o against B.alexandrina,and a 1.396 mg/L 24 h LCs0 against B.truncatus.Across all study regions,the pooled mortalities of O.hupensis were 72,86,94 and 98%at 1,2,3 and 7 d,following field immersion of 4%TDS at a dose of 2.5 g/m3,and were 69,77,85 and 88%at 1,3,7 and 15 d,following field spraying at 5 g/m2,respectively.4%TDS had moderate toxicity to Japanese quail(7 d LD5o>60 mg/kg)and to shrimp(96 h LCs0=6.28 mg/L;95%CI:3.53-11.2 mg/L),whereas its toxicity to zebrafish was high(96 h LCso--0.15 mg/L;95%CI:0.14-0.17 mg/L).Conclusions:4%TDS is active against O.hupensis,B.alexandrina and B.truncatus under laboratory and field conditions,and it may be a candidate molluscicide of plant origin.展开更多
Objective:To investigate the predation efficacy of the freshwater leech,Limnatis nilotica(L.nilotica)as a potential biological control agent against different stages of the Bulinus truncatus(B.truncatus),the intermedi...Objective:To investigate the predation efficacy of the freshwater leech,Limnatis nilotica(L.nilotica)as a potential biological control agent against different stages of the Bulinus truncatus(B.truncatus),the intermediate host of human Schistosoma haematobium,under laboratory conditions.Methods:The leech L.nilotica and the snail B.truncatus were collected from El Kiryab Agriculture Scheme,Sudan.Thereafter,the predatory activity of the leech was evaluated against eggs,neonates and adults of the snail in a series of different experiments under laboratory conditions.Results:The findings showed that the L.nilotica leech was a voracious predator towards the eggs and neonates of B.truncatus snails with a shell length of up to 3 mm,as well as of adult snails with an shell length greater than 3 mm.Conclusions:The results showed that L.nilotica had a significant impact on B.truncatus populations.However,long term studies under natural field conditions are needed to support these results.展开更多
Objective:To evaluate the efficacy of Alstonia congensis green-synthesized nanoparticles as a molluscicide against snail hosts of trematodes.Methods:The ethanolic leaf extract of Alstonia congensis was used to synthes...Objective:To evaluate the efficacy of Alstonia congensis green-synthesized nanoparticles as a molluscicide against snail hosts of trematodes.Methods:The ethanolic leaf extract of Alstonia congensis was used to synthesize silver nanoparticles.The formulation was characterized by Fourier transform infrared spectroscopy,X-ray powder diffraction,and scanning electron microscope/energy-dispersed X-ray.The ovicidal and molluscicidal activities of the Alstonia congensis extract and its nanoparticles were tested against Physa acuta and Bulinus forskalii at different concentrations.Results:The green-synthesized nanoparticles inhibited embryonic development within the egg masses of the two snails in all the tested concentrations.Alstonia congensis extract did not show molluscicidal properties against adult Physa acuta but showed a very weak activity against Bulinus forskalii.Moreover,the synthesized nanoparticles showed significantly high molluscicidal activity against adult snails within 5-40 min of exposure in a concentration-dependent manner(P<0.05).Conclusions:The Alstonia congensis-based nanoparticles show molluscicidal activities against adults and embryos of Physa acuta and Bulinus forskalii,and can be further explored as a potent molluscicide for the control of intermediate host of trematode parasites.展开更多
Background:The crater lakes of Barombi Mbo and Barombi Kotto are well-known transmission foci of schistosomiasis and soil-transmitted helminthiasis having had several important control initiatives previously.To collec...Background:The crater lakes of Barombi Mbo and Barombi Kotto are well-known transmission foci of schistosomiasis and soil-transmitted helminthiasis having had several important control initiatives previously.To collect contemporary epidemiological information,a cross-sectional survey was undertaken inclusive of:signs and symptoms of disease,individual treatment histories,local water,sanitation and hygiene(WASH)-related factors and malacological surveillance,with molecular characterisation of specimens.Methods:At each lake,a community cross-sectional survey was undertaken using a combination of stool and urine parasitological sampling,and interview with pro-forma questionnaires.A total of 338 children and adults participated.Material from snail and parasite species were characterised by DNA methods.Results:Egg-patent prevalence of urogenital schistosomiasis was 8.7%at Barombi Mbo(all light-intensity infections)and 40.1%at Barombi Kotto(21.2%heavy-intensity infections).Intestinal schistosomiasis was absent.At Barombi Kotto,significantly more women reported signs and symptoms associated with female genital schistosomiasis.While there had been extensive recent improvement in WASH-related infrastructure at Barombi Mbo,water contact risk scores were higher among schistosomiasis-infected participants(P<0.001)and at Barombi Kotto in general(P<0.001).Across both lakes,mean prevalence of STH was very low(6.3%)evidencing an impressive decrease of 79.0%over the last decade;neither Strongyloides stercoralis nor Ascaris lumbricoides were found.A total of 29 freshwater sampling sites were inspected for snails,13 in Barombi Mbo and 16 in Barombi Kotto;water chemistry differed significantly(P<0.0001)between lakes for both mean pH(7.9 v.9.6)and mean conductivity(64.3μS v.202.1μS)respectively.Only two Bulinus camerunensis found on the central island of Barombi Kotto were observed to shed schistosome cercariae,but schistosome DNA was later detected in Bulinus sampled from both lakes as well as in Indoplanorbis exustus,an invasive species from Asia.Conclusions:STH is currently at very low levels while urogenital schistosomiasis is of greatest concern at Barombi Kotto.This assessment highlights a unique opportunity for further study of the epidemiological dynamics at these crater lakes,to evaluate future intensified interventions both in terms of gaining and sustaining control at Barombi Kotto or in moving towards local interruption of transmission of both diseases at Barombi Mbo.展开更多
Background:The speedy rate of change in the environmental and socio-economics factors may increase the incidence,prevalence and risk of schistosomiasis infections in Zambia.However,available information does not provi...Background:The speedy rate of change in the environmental and socio-economics factors may increase the incidence,prevalence and risk of schistosomiasis infections in Zambia.However,available information does not provide a comprehensive understanding of the biogeography and distribution of the disease,ecology and population dynamics of intermediate host snails.The current study used an information-theoretical approach to understand the biogeography and prevalence schistosomiasis and identified knowledge gaps that would be useful to improve policy towards surveillance and eradication of intermediate hosts snails in Zambia.Methods:To summarise the existing knowledge and build on past and present experiences of schistosomiasis epidemiology for effective disease control in Zambia,a systematic search of literature for the period 2000-2017 was done on PubMed,Google Scholar and EBSCOhost.Using the key words:‘Schistosomiasis’,‘Biomphalaria’,‘Bulinus’,‘Schistosoma mansoni’,‘Schistosoma haematobium’,and‘Zambia’,in combination with Booleans terms‘AND’and‘OR’,published reports/papers were obtained and reviewed independently for inclusion.Results:Thirteen papers published in English that fulfilled the inclusion criteria were selected for the final review.The papers suggest that the risk of infection has increased over the years and this has been attributed to environmental,socio-economic and demographic factors.Furthermore,schistosomiasis is endemic in many parts of the country with infection due to Schistosoma haematobium being more prevalent than that due to S.mansoni.This review also found that S.haematobium was linked to genital lesions,thus increasing risks of contracting other diseases such as HIV and cervical cancer.Conclusions:For both S.haematobium and S.mansoni,environmental,socio-economic,and demographic factors were influential in the transmission and prevalence of the disease and highlight the need for detailed knowledge on ecological modelling and mapping the distribution of the disease and intermediate host snails for effective implementation of control strategies.展开更多
Background:The planorbid freshwater snails of the two genera,Biomphalaria and Bulinus-have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis.In Sudan specifically,most studies ...Background:The planorbid freshwater snails of the two genera,Biomphalaria and Bulinus-have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis.In Sudan specifically,most studies have focused on the chemical and ecological control of the two genera,but few studies have looked at their biological control.This study explored the coexistence of other species of freshwater snails and the two genera along with their trematode infections in relation to a number of environmental factors in the East Nile locality,Khartoum state,Sudan.Methods:Freshwater snails from irrigation canals(abueshreens)were sampled monthly from January 2004 to December 2005.The snails were examined for trematode infections by cercarial emergence immediately after collection and then weekly for an additional four weeks to allow for the maturation of prepatent infections.Vegetation cover in the study sites as well as the physicochemical characteristics of the water,including temperature,were also recorded.Results:A total of 10,493 snails,representing seven species,were collected.The most abundant species was Biomphalaria pfeifferi,representing 48.6%of the sample.Overall,14.1%of the snails were found to be shedding some type of cercariae.Five species were found to have infections;among these the Bulinus truncatus species was found to be the most heavily infected,with an overall prevalence of 46.2%.Double infections were recorded in only two B.truncatus snails and one Cleopatra bulimoides snail.Twenty different morphotypes of cercariae were recorded,seven of which appeared not to conform to previously described cercariae from Africa.Xiphidiocercariae type 1 was the most common type of cercariae recovered,accounting for 44.3% of all infections.The density of snails tended to be lower during the summer months than the winter months,except for M.tuberculata snails,which were not affected by seasonal changes.Conclusion:The findings of this study indicate that besides schistosomes,other larval trematodes are found,and some use the same intermediate hosts as the schistosomes.Further studies should be conducted to determine whether some of these trematodes could be manipulated for the biological control of schistosomiasis.展开更多
Background Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern.However,nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal re...Background Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern.However,nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp.and Schistosoma spp.in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad.The aim was to test whether trematode parasites such as Schistosoma spp.occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Serir in northern Chad.Methods The study was carried out in January 2019 and comprised of three components.First,a cross sectional survey based on a random sample drawn from the population to detect infections with S.haematobium and S.mansoni;second,focus group discussions exploring disease priorities,access to health and health seeking behaviour;and third,surveying water contact sites for intermediate host snails.Samples of trematode parasites and snails were confirmed on species level by molecular genetic methods.For parasitological and malacological surveys descriptive statistics were performed.Qualitative data analysis included the full review of all transcripts,followed by a descriptive and explorative thematic analysis.Results Among 258 participants,the overall S.haematobium prevalence using urine filtration was 39.2%[95%confidence interval(CI):33.5–45.1%],with 51.5%of the infected suffering from heavy infection.The intermediate host snail of S.haematobium(Bulinus truncatus)occurred at water contact sites near both study villages,revealing the potential for local transmission.Although a positive S.mansoni point-of-care circulating cathodic antigen(POC-CCA)test result was obtained from 8.6%(95%CI 5.7–12.8%)of the samples,no intermediate host snails of S.mansoni were found,and the relevance of S.mansoni remains uncertain.Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis,and the lack of access to diagnostics and treatment as a major health concern.Conclusions This research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara,a United Nations Educational,Scientific and Cultural Organization(UNESCO)world heritage site in Chad.Despite the high public health importance of the associated morbidity expressed by the population,there is no access to diagnostics and treatment.Further work is needed to develop and test a context-adapted intervention.展开更多
Background The control of schistosomiasis is particularly difficult in sub-Saharan Africa,which currently harbours 95%of this disease.The target population for preventive chemotherapy(PC)is expanded to all age group a...Background The control of schistosomiasis is particularly difficult in sub-Saharan Africa,which currently harbours 95%of this disease.The target population for preventive chemotherapy(PC)is expanded to all age group at risk of infection,thus increasing the demands of praziquantel(PZQ)tablets according to the new released guideline by World Health Organization.Due to the gap between available PZQ for PC and requirements,alternative approaches to assess endemicity of schistosomiasis in a community,are urgently needed for more quick and precise methods.We aimed to find out to which degree the infection status of snails can be used to guide chemotherapy against schistosomiasis.Methods We searched literature published from January 1991 to December 2022,that reported on the prevalence rates ofSchistosoma mansoni,S.haematobium in the intermediate snailsBiomphalaria spp.andBulinus spp.,respectively,and in humans.A random effect model for meta-analyses was used to calculate the pooled prevalence estimate(PPE),with heterogeneity assessed using I-squared statistic(I2),with correlation and regression analysis for the exploration of the relationship between humanS.mansoni andS.haematobium infections and that in their specific intermediate hosts.Results Forty-seven publications comprising 59 field investigations were included.The pooled PPE of schistosomiasis,schistosomiasis mansoni and schistosomiasis haematobium in humans were 27.5%[95%confidence interval(CI):24.0-31.1%],25.6%(95%CI:19.9-31.3%),and 28.8%(95%CI:23.4-34.3%),respectively.The snails showed an overall infection rate of 8.6%(95%CI:7.7-9.4%),with 12.1%(95%CI:9.9-14.2%)in theBiomphalaria spp.snails and 6.9%(95%CI:5.7-8.1%)in theBulinus spp.snails.The correlation coefficient was 0.3(95%CI:0.01-0.5%,P<0.05)indicating that the two variables,i.e.all intermediate host snails on the one hand and the human host on the other,were positively correlated.Conclusions The prevalence rate ofS.mansoni andS.haematobium is still high in endemic areas.Given the significant,positive correlation between the prevalence of schistosomes in humans and the intermediate snail hosts,more attention should be paid to programme integration of snail surveillance in future.展开更多
文摘Schistosomiasis is a public health concern in Benin. Freshwater snails of the genus Bulinus serve as intermediate hosts for schistosomes, trematode parasites responsible for bilharzia. The urinary form, caused by Schistosoma haematobium, is the most widespread and is transmitted to humans by these mollusks, with Bulinus truncatus and Bulinus globosus being the most important species. Effective strategies to combat the transmission of these parasites require a prior understanding of the molecular characterization of Bulinus snails. For this purpose, 293 Bulinus snails were collected and morphologically identified from two localities in southern Benin, Sô-Ava and Azowlissè. The snails were preserved in absolute alcohol. To achieve the set objectives, DNA was extracted from the collected biological material, and SSU gene fragments were amplified. Using PCR-RFLP, the amplified fragments were digested with the restriction endonucleases HaeIII, HinfI, and DdeI to perform molecular characterization. In this study, 80 individuals of B. globosus and 10 of B. truncatus were subjected to molecular analysis. The PCR-RFLP profiles showed bands of different sizes for the Bulinus species when analyzed with the three endonucleases using the SSU molecular marker. PCR-RFLP analysis revealed that the snails belonged to the freshwater genus Bulinus, including Bulinus globosus and B. truncatus, based on reference profiles from studies conducted in Nigeria, which enabled precise identification of these gastropods. This study provided initial insights, although still incomplete, into the molecular diversity of these species.
文摘The effects of sublethal concentrations of methanol extract of sesbania sesban plant on survival rate, egg laying of Bulinus truncatus snails, hatchability of their eggs, infection rate with Schistosoma haemato- bium miracidia, cercarial production and certain physiological parameters of treated snails were stu- died. The sublethal concentrations of the tested plant extract (LC0, LC10 and LC25) caused considerable reduction in survival rates;egg production of B. runcates snails;hatchability of eggs as well as in the infectivity of Schistosoma haematobium miracidia to the snail. Also, the tested concentrations reduced the cercarial production per snail and the period of cer-carial shedding. The glucose level in haemolymph of exposed snails was elevated while the glycogen, pro-tein content and the activities of hexokinase (HK), pyruvatekinase (PK) and lactate dehydrogenase (LDH) showed a decrease in soft tissues when compared with the control group. It was concluded that the app lication of sublethal concentration of methanol ex- tracts of Sesania sesban may be helpful in snail con- trol as it interferes with the snails’ biology and phy- siology.
文摘Background Freshwater snails of the genera Bulinus spp.,Biomphalaria spp.,and Oncomelania spp.are the main intermediate hosts of human and animal schistosomiasis.Identification of these snails has long been based on mor-phological and/or genomic criteria,which have their limitations.These limitations include a lack of precision for the morphological tool and cost and time for the DNA-based approach.Recently,Matrix-Assisted Laser Desorp-tion/lonization Time-Of-Flight(MALDI-TOF)mass spectrometry,a new tool used which is routinely in clinical microbi-ology,has emerged in the field of malacology for the identification of freshwater snails.This study aimed to evaluate the ability of MALDI-TOF MS to identify Biomphalaria pfeifferi and Bulinus forskali snail populations according to their geographicalorigin.Methods This study was conducted on 101 Bi.pfeifferi and 81 Bu.forskali snails collected in three distinct geo-graphical areas of Senegal(the North-East,South-East and central part of the country),and supplemented with wild and laboratory strains.Specimens which had previously been morphologically described were identified by MALDl-TOF MS[identification log score values(LSV)≥1.7],after an initial blind test using the pre-existing database.After DNA-based identification,new reference spectra of Bi.pfeiferi(n=10)and Bu.forskali(n=5)from the geographical areas were added to the MALDI-TOF spectral database.The final blind test against this updated database was per-formed to assess identification at the geographic source level.Results MALDI-TOF MS correctly identified 92.1%of 101 Bi.pfeifferi snails and 98.8%of 81 Bu.forskali snails.At the final blind test,88%of 166 specimens were correctly identified according to both their species and sampling site,with LSVs ranging from 1.74 to 2.70.The geographical source was adequately identified in 90.1%of 91 Bi.pfeifferi and 85.3%of 75 Bu.forskalii samples.Conclusions Our findings demonstrate that MALDI-TOF MS can identify and differentiate snail populations according to geographical origin.It outperforms the current DNA-based approaches in discriminating laboratory from wild strains.This inexpensive high-throughput approach is likely to further revolutionise epidemiological studies in areas which are endemic for schistosomiasis.
基金The study received financial support from University of KwaZulu-Natal College of Health Sciences through the student scholarship programme,and from United Nations International Children's Fund/United Nations Development Programme/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseasesfrom the Canadian International Development Research Centre through their support towards a Malaria and Bilharzia in Southern Africa project.
文摘Background:Given 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.Methods:Using 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.Results:Our results show that temperature may have a non-linear effect on snail fecundity and snail growth.Snails maintained at 15.5℃ and 36.0℃ did not produce egg masses while those maintained at 25.8℃ laid 344 and 105 more egg masses than snails at 31.0℃ and 21.2℃,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℃ occurred before snails started shedding cercariae.Parasite development was accelerated at high temperatures with snails maintained at 31.0℃ reaching patency after three weeks.Furthermore,snail growth rate was highest at 25.8℃ while it was inhibited at 15.5℃ and reduced at 31.0℃.Increase in temperature increased snail mortality rates.Snails maintained at 36.0℃ had the shortest survival time while those maintained at 15.5℃ had the longest survival time.Conclusions:We 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.
文摘Background: Bulinus globosus,the main intermediate snail host of Schistosoma haematobium.The increased contacts between Africa and China could even lead to large-scale dissemination of B.globosus in China.Temperature is the key factor affecting fresh-water snail transmission.This study predicted potential risk of colonization of B.globosus in the mainland of China under climate change.Methods: We investigated minimum and maximum temperatures for B.globosus eggs,juveniles and adult snails kept under laboratory conditions to find the most suitable range by pinpointing the median effective temperatures(ET50).We also assessed the influence of temperature on spawning and estimated the accumulated temperature(AT).The average air temperatures between 1955 and 2019 in January and July,the coldest and hottest months in China,respectively,were collected from national meteorological monitoring stations and investigated in a geographic information system(GIS)using empirical Bayesian Kriging to evaluate the theoretical possibility for distribution of B.globosus in southern China based on temperature.Results: The effective minimum temperature(ET50min)for eggs,juveniles,adult snails and spawning were 8.5,7.0,7.0,14.9℃,respectively,with the corresponding maximum values(ET50max)of 36.6,40.5,40.2 and 38.1℃.The AT was calculated at 712.1±64.9℃·d.In 1955,the potential B.globosus distribution would have had a northern boundary stretching from the coastal areas of Guangdong Province and Guangxi Autonomous Region to southern Yunnan Province.Since then,this line has gradually moved northward.Conclusions: Annual regeneration of B.globosus can be supported by the current climate conditions in the mainland of China,and a gradual expansion trend from south to north is shown in the study from 2015 to 2019.Thus,there is a potential risk of colonization of B.globosus in the mainland of China under climate change.
基金the National Science and Technology Pillar Program(grant No.2009BAI78B07 and 2009BAI78B04)National S&T Major Program(grant No.2012ZX10004-220)+3 种基金Shanghai Science and Technology Committee(grant No.11XD1405400)Jjiangsu Provincial Health and Family Planning Commission(grant No.QNRC2016621 and H2018097)Wuxi Municipal Bureau of Science and Technology(grant No.CSE31N1730)Bill&Melinda Gates Foundation.
文摘Background:Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis.Some plant extracts have shown obvious molluscicidal activity,and a new compound Luo-Wei,also named tea-seed distilled saponin(TDS),was developed based on the saponins extracted from Camellia oleifera seeds.We aimed to test the molluscicidal activity of 4%TDS against the intermediate host snails in China and Egypt,and evaluate its environmental safety to non-target organisms.Methods:In the laboratory,Oncomelania hupensis,Biomphalaria alexandrina and Bulinus truncatus were exposed to 4%TDS,and the median lethal concentration(LC5o)was estimated at 24,48 and 72 h.In the field,snail mortalities were assessed 1,2,3 and 7 d post-immersion with 2.5 g/m34%TDS and 1,3,7 and 15 d post-spraying with 5 g/m24%TDS.in addition,the acute toxicity of 4%TDS to Japanese quail(Coturnixjaponica),zebrafish(Brachydanio rerio)and freshwater shrimp(Macrobrachium nipponense)was assessed by estimations of LC5o or median lethal dose(LD5o).Results:In the laboratory,the LC5o values of 4%TDS for O.hupensis were 0.701,0.371 and 0.33 mg/L at 24,48 and 72 h,respectively,and 4%TDS showed a 0.33 mg/L 24 h LC5o against B.alexandrina,and a 1.396 mg/L 24 h LCs0 against B.truncatus.Across all study regions,the pooled mortalities of O.hupensis were 72,86,94 and 98%at 1,2,3 and 7 d,following field immersion of 4%TDS at a dose of 2.5 g/m3,and were 69,77,85 and 88%at 1,3,7 and 15 d,following field spraying at 5 g/m2,respectively.4%TDS had moderate toxicity to Japanese quail(7 d LD5o>60 mg/kg)and to shrimp(96 h LCs0=6.28 mg/L;95%CI:3.53-11.2 mg/L),whereas its toxicity to zebrafish was high(96 h LCso--0.15 mg/L;95%CI:0.14-0.17 mg/L).Conclusions:4%TDS is active against O.hupensis,B.alexandrina and B.truncatus under laboratory and field conditions,and it may be a candidate molluscicide of plant origin.
文摘Objective:To investigate the predation efficacy of the freshwater leech,Limnatis nilotica(L.nilotica)as a potential biological control agent against different stages of the Bulinus truncatus(B.truncatus),the intermediate host of human Schistosoma haematobium,under laboratory conditions.Methods:The leech L.nilotica and the snail B.truncatus were collected from El Kiryab Agriculture Scheme,Sudan.Thereafter,the predatory activity of the leech was evaluated against eggs,neonates and adults of the snail in a series of different experiments under laboratory conditions.Results:The findings showed that the L.nilotica leech was a voracious predator towards the eggs and neonates of B.truncatus snails with a shell length of up to 3 mm,as well as of adult snails with an shell length greater than 3 mm.Conclusions:The results showed that L.nilotica had a significant impact on B.truncatus populations.However,long term studies under natural field conditions are needed to support these results.
文摘Objective:To evaluate the efficacy of Alstonia congensis green-synthesized nanoparticles as a molluscicide against snail hosts of trematodes.Methods:The ethanolic leaf extract of Alstonia congensis was used to synthesize silver nanoparticles.The formulation was characterized by Fourier transform infrared spectroscopy,X-ray powder diffraction,and scanning electron microscope/energy-dispersed X-ray.The ovicidal and molluscicidal activities of the Alstonia congensis extract and its nanoparticles were tested against Physa acuta and Bulinus forskalii at different concentrations.Results:The green-synthesized nanoparticles inhibited embryonic development within the egg masses of the two snails in all the tested concentrations.Alstonia congensis extract did not show molluscicidal properties against adult Physa acuta but showed a very weak activity against Bulinus forskalii.Moreover,the synthesized nanoparticles showed significantly high molluscicidal activity against adult snails within 5-40 min of exposure in a concentration-dependent manner(P<0.05).Conclusions:The Alstonia congensis-based nanoparticles show molluscicidal activities against adults and embryos of Physa acuta and Bulinus forskalii,and can be further explored as a potent molluscicide for the control of intermediate host of trematode parasites.
基金funded as part of the COUNTDOWN research programme consortium,by the Research and Evidence Division of the Department for International Development,UK
文摘Background:The crater lakes of Barombi Mbo and Barombi Kotto are well-known transmission foci of schistosomiasis and soil-transmitted helminthiasis having had several important control initiatives previously.To collect contemporary epidemiological information,a cross-sectional survey was undertaken inclusive of:signs and symptoms of disease,individual treatment histories,local water,sanitation and hygiene(WASH)-related factors and malacological surveillance,with molecular characterisation of specimens.Methods:At each lake,a community cross-sectional survey was undertaken using a combination of stool and urine parasitological sampling,and interview with pro-forma questionnaires.A total of 338 children and adults participated.Material from snail and parasite species were characterised by DNA methods.Results:Egg-patent prevalence of urogenital schistosomiasis was 8.7%at Barombi Mbo(all light-intensity infections)and 40.1%at Barombi Kotto(21.2%heavy-intensity infections).Intestinal schistosomiasis was absent.At Barombi Kotto,significantly more women reported signs and symptoms associated with female genital schistosomiasis.While there had been extensive recent improvement in WASH-related infrastructure at Barombi Mbo,water contact risk scores were higher among schistosomiasis-infected participants(P<0.001)and at Barombi Kotto in general(P<0.001).Across both lakes,mean prevalence of STH was very low(6.3%)evidencing an impressive decrease of 79.0%over the last decade;neither Strongyloides stercoralis nor Ascaris lumbricoides were found.A total of 29 freshwater sampling sites were inspected for snails,13 in Barombi Mbo and 16 in Barombi Kotto;water chemistry differed significantly(P<0.0001)between lakes for both mean pH(7.9 v.9.6)and mean conductivity(64.3μS v.202.1μS)respectively.Only two Bulinus camerunensis found on the central island of Barombi Kotto were observed to shed schistosome cercariae,but schistosome DNA was later detected in Bulinus sampled from both lakes as well as in Indoplanorbis exustus,an invasive species from Asia.Conclusions:STH is currently at very low levels while urogenital schistosomiasis is of greatest concern at Barombi Kotto.This assessment highlights a unique opportunity for further study of the epidemiological dynamics at these crater lakes,to evaluate future intensified interventions both in terms of gaining and sustaining control at Barombi Kotto or in moving towards local interruption of transmission of both diseases at Barombi Mbo.
基金The writing of this review was made possible through the post-doctoral fellowship from the University of KwaZulu-Natal,College of Health Sciences that was awarded to Dr.Chester Kalinda。
文摘Background:The speedy rate of change in the environmental and socio-economics factors may increase the incidence,prevalence and risk of schistosomiasis infections in Zambia.However,available information does not provide a comprehensive understanding of the biogeography and distribution of the disease,ecology and population dynamics of intermediate host snails.The current study used an information-theoretical approach to understand the biogeography and prevalence schistosomiasis and identified knowledge gaps that would be useful to improve policy towards surveillance and eradication of intermediate hosts snails in Zambia.Methods:To summarise the existing knowledge and build on past and present experiences of schistosomiasis epidemiology for effective disease control in Zambia,a systematic search of literature for the period 2000-2017 was done on PubMed,Google Scholar and EBSCOhost.Using the key words:‘Schistosomiasis’,‘Biomphalaria’,‘Bulinus’,‘Schistosoma mansoni’,‘Schistosoma haematobium’,and‘Zambia’,in combination with Booleans terms‘AND’and‘OR’,published reports/papers were obtained and reviewed independently for inclusion.Results:Thirteen papers published in English that fulfilled the inclusion criteria were selected for the final review.The papers suggest that the risk of infection has increased over the years and this has been attributed to environmental,socio-economic and demographic factors.Furthermore,schistosomiasis is endemic in many parts of the country with infection due to Schistosoma haematobium being more prevalent than that due to S.mansoni.This review also found that S.haematobium was linked to genital lesions,thus increasing risks of contracting other diseases such as HIV and cervical cancer.Conclusions:For both S.haematobium and S.mansoni,environmental,socio-economic,and demographic factors were influential in the transmission and prevalence of the disease and highlight the need for detailed knowledge on ecological modelling and mapping the distribution of the disease and intermediate host snails for effective implementation of control strategies.
文摘Background:The planorbid freshwater snails of the two genera,Biomphalaria and Bulinus-have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis.In Sudan specifically,most studies have focused on the chemical and ecological control of the two genera,but few studies have looked at their biological control.This study explored the coexistence of other species of freshwater snails and the two genera along with their trematode infections in relation to a number of environmental factors in the East Nile locality,Khartoum state,Sudan.Methods:Freshwater snails from irrigation canals(abueshreens)were sampled monthly from January 2004 to December 2005.The snails were examined for trematode infections by cercarial emergence immediately after collection and then weekly for an additional four weeks to allow for the maturation of prepatent infections.Vegetation cover in the study sites as well as the physicochemical characteristics of the water,including temperature,were also recorded.Results:A total of 10,493 snails,representing seven species,were collected.The most abundant species was Biomphalaria pfeifferi,representing 48.6%of the sample.Overall,14.1%of the snails were found to be shedding some type of cercariae.Five species were found to have infections;among these the Bulinus truncatus species was found to be the most heavily infected,with an overall prevalence of 46.2%.Double infections were recorded in only two B.truncatus snails and one Cleopatra bulimoides snail.Twenty different morphotypes of cercariae were recorded,seven of which appeared not to conform to previously described cercariae from Africa.Xiphidiocercariae type 1 was the most common type of cercariae recovered,accounting for 44.3% of all infections.The density of snails tended to be lower during the summer months than the winter months,except for M.tuberculata snails,which were not affected by seasonal changes.Conclusion:The findings of this study indicate that besides schistosomes,other larval trematodes are found,and some use the same intermediate hosts as the schistosomes.Further studies should be conducted to determine whether some of these trematodes could be manipulated for the biological control of schistosomiasis.
文摘Background Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern.However,nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp.and Schistosoma spp.in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad.The aim was to test whether trematode parasites such as Schistosoma spp.occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Serir in northern Chad.Methods The study was carried out in January 2019 and comprised of three components.First,a cross sectional survey based on a random sample drawn from the population to detect infections with S.haematobium and S.mansoni;second,focus group discussions exploring disease priorities,access to health and health seeking behaviour;and third,surveying water contact sites for intermediate host snails.Samples of trematode parasites and snails were confirmed on species level by molecular genetic methods.For parasitological and malacological surveys descriptive statistics were performed.Qualitative data analysis included the full review of all transcripts,followed by a descriptive and explorative thematic analysis.Results Among 258 participants,the overall S.haematobium prevalence using urine filtration was 39.2%[95%confidence interval(CI):33.5–45.1%],with 51.5%of the infected suffering from heavy infection.The intermediate host snail of S.haematobium(Bulinus truncatus)occurred at water contact sites near both study villages,revealing the potential for local transmission.Although a positive S.mansoni point-of-care circulating cathodic antigen(POC-CCA)test result was obtained from 8.6%(95%CI 5.7–12.8%)of the samples,no intermediate host snails of S.mansoni were found,and the relevance of S.mansoni remains uncertain.Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis,and the lack of access to diagnostics and treatment as a major health concern.Conclusions This research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara,a United Nations Educational,Scientific and Cultural Organization(UNESCO)world heritage site in Chad.Despite the high public health importance of the associated morbidity expressed by the population,there is no access to diagnostics and treatment.Further work is needed to develop and test a context-adapted intervention.
基金National Science Foundation of China(82073619)National Key Research and Development Program of China(2021YFC2300800,2021YFC2300804)+1 种基金General Programs of Jiangsu Commission of Health(H202309)Schistosomiasis and Parasitic Diseases Project of Jiangsu Province(×202103)。
文摘Background The control of schistosomiasis is particularly difficult in sub-Saharan Africa,which currently harbours 95%of this disease.The target population for preventive chemotherapy(PC)is expanded to all age group at risk of infection,thus increasing the demands of praziquantel(PZQ)tablets according to the new released guideline by World Health Organization.Due to the gap between available PZQ for PC and requirements,alternative approaches to assess endemicity of schistosomiasis in a community,are urgently needed for more quick and precise methods.We aimed to find out to which degree the infection status of snails can be used to guide chemotherapy against schistosomiasis.Methods We searched literature published from January 1991 to December 2022,that reported on the prevalence rates ofSchistosoma mansoni,S.haematobium in the intermediate snailsBiomphalaria spp.andBulinus spp.,respectively,and in humans.A random effect model for meta-analyses was used to calculate the pooled prevalence estimate(PPE),with heterogeneity assessed using I-squared statistic(I2),with correlation and regression analysis for the exploration of the relationship between humanS.mansoni andS.haematobium infections and that in their specific intermediate hosts.Results Forty-seven publications comprising 59 field investigations were included.The pooled PPE of schistosomiasis,schistosomiasis mansoni and schistosomiasis haematobium in humans were 27.5%[95%confidence interval(CI):24.0-31.1%],25.6%(95%CI:19.9-31.3%),and 28.8%(95%CI:23.4-34.3%),respectively.The snails showed an overall infection rate of 8.6%(95%CI:7.7-9.4%),with 12.1%(95%CI:9.9-14.2%)in theBiomphalaria spp.snails and 6.9%(95%CI:5.7-8.1%)in theBulinus spp.snails.The correlation coefficient was 0.3(95%CI:0.01-0.5%,P<0.05)indicating that the two variables,i.e.all intermediate host snails on the one hand and the human host on the other,were positively correlated.Conclusions The prevalence rate ofS.mansoni andS.haematobium is still high in endemic areas.Given the significant,positive correlation between the prevalence of schistosomes in humans and the intermediate snail hosts,more attention should be paid to programme integration of snail surveillance in future.
