Transmission Of Urinary Schistosomiasis Research Articles

Human-water interactions associated to cercarial emergence pattern and their influences on urinary schistosomiasis transmission in two endemic areas in Mali

BackgroundMali is known to be a schistosomiasis-endemic country with a limited supply of clean water. This has forced many communities to rely on open freshwater bodies for many human-water contact (HWC) activities. However, the relationship between contact with these water systems and the level of schistosome infection is currently receiving limited attention. This study assessed human-water interactions including cercarial emergence pattern and their influences on urinary schistosomiasis transmission in two communities in the Kayes district of Mali.MethodsWe carried out a parasitological study first in children in September 2021, then a cross-sectional study of quantitative observations of human-water contact activities in the population, and finally a study of snail infectivity at contact points in September 2022. The study took place in two communities, Fangouné Bamanan and Diakalèl in the Kayes region of western Mali. The chronobiological study focused on cercarial release from naturally infected snails. Released cercariae were molecularly genotyped by targeting the cox1 region, and the ITS and 18S ribosmal DNA gene (18S rDNA) regions of the DNA. Links between sociodemographic parameters, human water-contact points and hematuria were established using multivariate statistical analysis or the logistic regression model.ResultsThe main factor predisposing the 97 participants to water contact was domestic activity (62.9%). Of the 378 snails collected at 14 sampling sites, 27 (7.1%) excreted schistosome cercariae, with 15.0% (19/126) at Fangouné Bamanan and 3.3% (8/252) at Diakalel. The release of Schistosoma cercariae shows three different patterns in Fangouné Bamanan: (i) an early release peak (6:00–8:00 AM), (ii) a mid-day release peak (10:00 AM–12:00 PM) and (iii) a double peak: (6:00–8:00 AM) and (6:00–8:00 PM) cercariae release; and two release patterns in Diakalel: early release (6:00–8:00 AM) and (ii) mid-day release (12:00–2:00 PM). All cercariae released during early diurnal (6:00–8:00 AM) or nocturnal emission patterns (6:00–8:00 PM) were hybrids parasite having an cox1 S. bovis or S. curassoni associated with an ITS and 18S rDNA of S. haematobium while the cercariae released during diurnal, or mid-day patterns (8:00 AM–6:00 PM) were pure S. haematobium.ConclusionsOur study showed that domestic activity is the main source of exposure in the Kayes region. Two and three cercariae emission patterns were observed at Diakalel and Fangouné Bamanan respectively. These results suggest that the parasite adapts to the human-water contact period in order to increase its infectivity.Graphical

URINARY SCHISTOSOMIASIS AMONG SCHOOL-AGE CHILDREN IN SELECTED RURAL COMMUNITIES IN HADHRAMOUT GOVERNORATE, YEMEN

Background: Urinary schistosomiasis is a potentially life-threatening public health issue in some areas of Yemen, particularly in Hadhramout rural communities. It is considered as one of the most common neglected tropical parasitic diseases. This study aimed to investigate the prevalence of urinary schistosomiasis and associated risk factors among school-age males and females in selected rural communities of Hadhramout, Yemen. Methods: A total of 450 students participated in this cross-sectional study. Urine samples were collected, then examined for haematuria and Schistosoma haematobium (S. haematobium) eggs using urine dipsticks and filtration technique respectively. To assess knowledge and practices regarding the transmission of urinary schistosomiasis, a pre-tested questionnaire was employed. Results: An overall (66)14.7% of participants tested positive for S. haematobium, and of those, 54 (12.0%) developed haematuria with a statistically significant difference (p=0.001). A total of 35(53.0% eggs/10 ml urine) had heavy intensity of infection, with a significant difference (p=0.001) between the different communities visited: high in Al-Dhulaya'a (18.2 eggs/10 ml urine) and low in Yabaith (6.1 eggs/10 ml urine). S. haematobium infection showed significantly higher (p=0.002) in males (13.8%) than females (0.9%), and increased with age of participants. Multivariate logistic analysis of risk factors were significantly associated with the prevalence of urinary schistosomiasis such as swimming activities (p=0.016), washing clothes (p=0.14), time spent in infested areas more than 15 minutes (p=0.012), habits of defecation/urination in open water sources (p=0.44), self-reported symptoms suggestive of the disease (p=0.03), participants with a history of illness (p=0.014), lack of awareness of schistosomiasis (p=0.050), and no prior treatment with praziquantel (p=0.001). Conclusions: Urinary schistosomiasis remains highly prevalent among schoolchildren in rural communities in Hadhramaut. The study highlights the urgent need to implement preventive measures, safe drinking water supply, proper sanitation, and vector control programs in order to reduce transmission and morbidity caused by schistosomiasis. Peer Review History: Received 3 December 2023; Revised 28 January 2024; Accepted 27 February; Available online 15 March 2024 Academic Editor: Dr. Marwa A. A. Fayed, University of Sadat City, Egypt, maafayed@gmail.com Average Peer review marks at initial stage: 6.0/10 Average Peer review marks at publication stage: 7.5/10 Reviewers: Dr. Owanaro Peter, Nigeria, Department of Clinical Pharmacy and Pharmacy Practice, Faculty of Pharmacy, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria. owonaropeter@gmail.com Dr. George Zhu, Tehran University of Medical Sciences, Tehran, Iran, sansan4240732@163.com

Spatial variation of life-history traits in Bulinus truncatus, the intermediate host of schistosomes, in the context of field application of niclosamide in C\xf4te d\u2019Ivoire

BackgroundControl of intermediate host snails using molluscicides for the control and/or elimination of schistosomiasis is a strategy in line with WHO recommendations. Niclosamide is the main chemical molluscicide recommended by WHO. However, except the immediate killing of the snail, the extent of the impact of the molluscicide application on the evolution of snail life-history traits, in relation to recolonization of treated sites is not well known. This study aimed to characterize the spatial variation of life-history traits of populations of the freshwater snail Bulinus truncatus, in relation to niclosamide spraying in the field.From 2016 to 2018, we conducted a trial, using niclosamide to control the intermediate host snails for interrupting the seasonal transmission of urinary schistosomiasis in northern and central Côte d’Ivoire. Five villages (sites) were considered, including three test and two control villages. In the test villages, the molluscicide was sprayed in habitats harboring B. truncatus snails three times a year (November, February–March and June). We sampled six B. truncatus populations: two populations from the control villages without any treatment; one collected before treatment and three sampled 2–3 months after treatment of the site with niclosamide. The snail populations were monitored for several life-history traits, including survival, growth, fecundity and hatchability, under laboratory conditions, over one generation (G1). We tested the population, region (North/Centre) and treatment status (treated/untreated) effects on the variation of the measured life-history traits and correlations between pairs of traits were estimated.ResultsOn the whole, the traits varied among populations. The risk of death was lower in northern populations compared to central ones. The age at first reproduction was reached earlier with a smaller size of snails in northern populations. Values of first reproduction features (size and fecundity) were lower in treated snail populations. The overall growth of untreated populations was higher than that of treated ones. The late fecundity and egg hatching were higher in northern than in central snails. At first reproduction, age was negatively correlated with some fecundity parameters. However, growth was positively associated with fecundity.ConclusionsOur study showed a spatial variation of life-history traits in B. truncatus snails. The mollusciciding seems to have led to the depression of some life-history traits in the snail populations. However, investigations should be carried out over several generations of snails to better clarify the impact of niclosamide on the evolution of the life-history traits.

Review of Risk Factors Associated with Transmission of Urinary Schistosomiasis amongst Vulnerable Groups: School Pupils and Almajiris and Effect of Treatment with Praziquantel in Maiduguri Metropolis, North-Eastern Nigeria.

Human schistosomiasis is the most prevalent tropical disease in the world after malaria. Most of the countries in Sub Saharan Africa including Nigeria have not achieved the Millennium Development Goals for accessing safe drinking water and halting or reversing major disease incidences. School aged children and young Almajiri were selected for the cross-sectional study. Awareness lectures were given at every study site before collection of samples. Urine filtration technique was used for the diagnosis of urinary schistosomiasis. Infected subjects were given 60mg Praziquantel and followed up after 28 days and the effect was assessed by calculating the cure rate. A total of 308 subjects were enrolled comprising of 200 school children and 108 Almajiri respectively with a mean age of 13 years old. Female-to-male ratio is 9.6. Out of the 308 participants, 149 had urinary schistosomiasis (48.4%) with 5 among the females (17.2%) and 144 among the males (51.6%) respectively (p>0.005). A significant 26.3% of the respondents had haematuria and 77.8% were infected. Only one respondent admitted having knowledge of the disease. A total 136 of those infected received the treatment of 60mg Praziquantel and 43 (31.6%) showed eggs in their urine 28 days after taking PZQ. Highest (84.6%) cure rate was observed among the youngest age group of 5-9 years and lowest (60.3%) was observed among the oldest age group 15-19 years (p=0.005). An overall prevalence of 48.4% among these vulnerable group of the society calls for a great concern because these group of the population serve as means of maintaining the infection cycle. Dearth of knowledge about schistosomiasis, extreme weather condition, lack of potable water supply and poverty remains the reason behind the continued endemicity of schistosomiasis in the study area.

Influence of human–surface water interactions on the transmission of urinary schistosomiasis in the Lower Densu River basin, Ghana

Influence of human–surface water interactions on the transmission of urinary schistosomiasis in the Lower Densu River basin, Ghana

Prevalence of urinary schistosomiasis amongst primary school children in Ikwo and Ohaukwu Communities of Ebonyi State, Nigeria.

BackgroundUrinary schistosomiasis is a serious public health challenge in some communities of Ebonyi State, south-east Nigeria, partly resulting from a lack of adequate epidemiological data for the institution of effective control strategies.ObjectiveThis study evaluated the prevalence and risk factors of urinary schistosomiasis in rural communities of Ebonyi State, south-east Nigeria.MethodsA total of 300 students, comprising 185 boys and 115 girls, were randomly selected for the study between July and December 2016. A questionnaire was administered to all participants to determine the risk factors for the disease in the area. Urine specimens collected from the participants were processed by sedimentation and examined microscopically for the eggs of Schistosoma haematobium.ResultsThe overall prevalence rate for urinary schistosomiasis was 8.0%. Students aged 6–10 years had the highest prevalence of infection (10.3%). The prevalence was significantly higher amongst male students (10.3%; p = 0.038) compared with female students (4.4%). Logistic regression analysis showed a significant association between schistosomiasis infection and freshwater contact activities (p = 0.007; odds ratio = 1.89; 95% confidence interval: 4.33–16.17). Contact with stream, pond, river and well water were associated with infection rates of 25%, 14%, 5.3%, and 4.4%, respectively.ConclusionA relatively low prevalence of urinary schistosomiasis was found in the area. Participants’ socio-economic status and dependence on contaminated water sources were core modifiable risk factors. Health education and development of potable water infrastructure, amongst other interventions, would likely reduce the burden and transmission of urinary schistosomiasis in this locality.

Community knowledge, perceptions and water contact practices associated with transmission of urinary schistosomiasis in an endemic region: a qualitative cross-sectional study

BackgroundIn an effort to complement the current chemotherapy based schistosomiasis control interventions in Shinyanga district, community knowledge, perceptions and water contact practices were qualitatively assessed using focus group discussions and semi structured interviews involving 271 participants in one S. haematobium prevalent community of Ikingwamanoti village, Shinyanga district, Northwestern, Tanzania.MethodsIn October, 2016 we conducted 29 parent semi structured interviews and 16 focus group discussions with a total of 168 parent informants. Adult participants were conveniently selected from three sub-villages of Butini, Miyu, and Bomani of Ikingwamanoti village, Shinyanga district. In March, 2017, a total of 103 children informants participated in 10 focus group discussions and 20 semi structured interviews, administered to children from standard four, five, six and seven attending Ikingwamanoti Primary School. Note taking and digital recorders were used to collect narrative data for thematic analysis of emergent themes.ResultsAmong participants, 75% parents and 50% children considered urinary schistosomiasis as a low priority health problem. Of the informants, 70% children and 48.3% parents had misconceptions about the cause, modes of transmission and control of schistosomiasis demonstrating gaps in their biomedical knowledge of the disease. Assessment of treatment seeking behavior for urinary schistosomiasis revealed a combination of traditional and modern health care sectors. However, modern medicines were considered effective in the treatment of urinary schistosomiasis. Lack of alternative sources of water for domestic and recreational activities and unhygienic water use habits exposed community members to high risk of acquiring urinary schistosomiasis.ConclusionUse of Schistosoma haematobium contaminated water sources for daily domestic and recreational use facilitated contraction of urinary schistosomiasis among community members in Shinyanga district. People’s perceptions of urinary schistosomiasis as a less priority health problem promoted persistence of the disease. Future efforts to control urinary schistosomiasis should take into account integrated approaches combining water, sanitation and hygiene, health education, alternative sources of clean and safe water to facilitate behavior change.

Transmission of Urinary Schistosomiasis among School Aged Children in Owena, Kajola and Baiken Communities Bordering Owena Reservoir/Dam, Ondo East Local Area, Ondo State, Southwest, Nigeria

Background: Schistosomiasis is a snail-borne, water-based parasitic infection caused by blood-dwelling (hence called blood-fluke) trematode worms of the genus Schistosoma. It is a disease of the poor and marginalized. Schistosomiasis remains an important public health problem globally with approximately 779 million estimated to be at risk. This study was carried out to ascertain the prevalence of the disease among school children in the three communities: Owena, Kajola and Baiken with a view to providing important parasitological information and boosting can sustainable control strategies of the disease.Methods: A school based cross-sectional technique was used to collect data on risk factors from 624 school children in March 2014 and 591 in April 2015. Urine samples were collected between the hours of 10:00 am 12:00 pm GMT in dry labeled wide mouthed. Plastic urine container (300-500 ml) each 10 ml was centrifuged and examined for the presence or absence of more nutobiuk eggs. Using X40 objectives of a light microscope. Infection intensity was recorded as number of eggs per 10 ml of urine sample. The intensity of infection was graded as heavy 500 eggs/10 ml urine, moderate (51-499 eggs/10 ml urine) or light (50 eggs/10 ml urine). Data obtained were analyzed using version 20.0 of the Statistical Package for The Social Sciences (SPSS) for windows Software Packages (SPSS on Chicag oil, 2013).Results: Our of the 624 pupils examined in 2014, 256 (41.0%) were positive for S. haematobium eggs in urine, while in 2015, 381 (64.5%) out of 591 were positive. Thus, there was a 23% increase in prevalence between the two genera. Individual intensity of infection varied from 1-6, 468 eggs/10 ml urine. Meaning the most heavily infected pupil in 2015 exceeded more than 68% infection in 2014. The arithmetic memory 2016 in moles was 0.65 in 2015 it was 0.09, while that of females in 2014 was 0.05 and 0.08 in 2015.Conclusion: This study area in Owena, Kajola and Baiken communities bordering Owena Reservoir/Dam, Ondo East Local Government Area, Ondo State, Nigeria show risk communities for urinary schistosomiasis. The overall pattern of S. haematobium eggs per 10 ml urine in the three communities in the two years (March 2014 and April 2015) study shows that it was sex and age dependent. The age-group with highest prevalence is 11-15 years in 2014 and 55.4% in 2015 with range infection for males was 43.6% in 2014 and 71.86 in 2015, while that of females was 37.0% in 2014 and 57.0% in 2015. Therefore, it is recommended that all school-age children especially those in 11-15 age-group should be treated using chemotherapy method. Pipe-borne water to prevent people having contact with the infected fresh water, sewage disposal facilities provided, mass educational therapy (societal sensitization/ health education) is required to reduce infection and transmission of urinary schistosomiasis.

Urinary schistosomiasis among primary school children at Al‐Takamul area, eastern Khartoum state‐Sudan: An example for urban schistosomiasis

Background : Urinary Schistosomiasis, caused by Schistosoma haematobium, is classically associated with rural areas that provide the hospitable condition for transmission. With the recent massive internal displacement, new communities were settled and created urban extensions to the big cities. These extensions bridged the space between the urban areas and the agricultural schemes around them. The area selected for this study is a good example for these settings. Given that the new population was displaced from known endemic areas, the transmission cycle seems to be completed. Objective: The aim of this study is to identify the frequency of urinary schistosomiasis among school children form Al-Takamul, which is a suburban district located in the Eastern Khartoum State. Materials and Methods : 150 school children were enrolled in this study, all were boys. Half of them were 11 year old or less. 20 ml of fresh voided urine (including terminal urine) were collected from each participant after a short period of exercise. Following physical and chemical examination, 10 ml sample of each specimen was centrifuged and the sediment was then thoroughly examined under the microscope. Results: 22% of study populations were found infected with S. haematobium (sensitivity 96.97%, specificity 100%), 87.9% of them were more than 11 year old (RR 2.23). 27.27% of the infected individuals had a history of past infection. 84.8% of infected population knew about schistosomiasis and its transmission. The results suggested that urban schistosomiasis is prevalent in the study area and it is presented with a distinguished pattern, that is, it is prevalent among children over 11 years old, and it is associated with knowledge but no awareness. Conclusion : The study area may be a potential focal point of urinary schistosomiasis transmission for neighboring areas. Massive survey and preventive chemotherapy is urgent.

Water Contact Patterns and Urinary Schistosomiasis Transmission among School Children in Endemic Area of Wudil, Kano, Nigeria

Water Contact Patterns and Urinary Schistosomiasis Transmission among School Children in Endemic Area of Wudil, Kano, Nigeria

Studies on the Prevalence of Urinary Schistosomiasis in Ogun State, South-Western Nigeria

The assessment of the extent and distribution of Schistosoma infection in every region in Nigeria is important and required for formulating intervention strategies suitable for each endemic area. To assess the prevalence of urinary schistosomiasis in Ogun State, South-West Nigeria. Urine samples of pupils were examined for schistosoma eggs by sedimentation technique among selected primary school children. Pretested and structured questionnaires were also administered for KAP studies. The overall prevalence of 32.2% was observed for schistosomiasis in 276 pupils. Peak prevalence of urinary schistosomiasis infection (36.2%) was found in 8-10 years age group. Thirty-seven percent reported passing blood in urine, about 50% of these informed their parents but 53.1% of the parents did nothing. Contact with stream water played a significant role in the transmission of urinary schistosomiasis as 80.9% of those infected used the stream water for domestic and recreational purposes. There was no significant difference (Χ² =0.0489, P>0.05 = 0.0489, P>0.05) between infection status among males and females. There is need for control measures in this area in order to curb the high prevalence of schistosomiasis.

Urinary schistosomiasis transmission in Epe, an urban community of Southwest Nigeria

Background:A survey of Schistosoma haematobium infection in Epe, an urban community in Lagos State, Southwest Nigeria, was carried out to ascertain the possibility that schistosomiasis, otherwise considered a rural disease, could reach urban populations.Materials and Methods:About 100 ml of voided urine samples from 200 pupils aged 6–13 years [109 (54.5%) males and 91 (45.5%) females], attending an Anglican primary school, Ebute Afuye, and a community primary school, Erepoto, were examined parasitologically for hematuria and S. haematobium ova following informed consent obtained from their parents/guardians. All samples were screened using polymerase chain reaction (PCR) amplification of the schistosome Dra1 gene. Fourteen Bulinus snails collected from the two sites, Ebute Afuye (6) and Erepoto (8), were screened for schistosome infection by the PCR amplification of the schistosome Dra1 gene. PCR-RFLP of the snails’ its region was analyzed for species identification and a subregion of the cox1 gene from four infected snails (two from each site) was amplified and sequenced.Results:In the Anglican primary school, Ebute Afuye, and community primary school, Erepoto, 16% and 29% were positive for hematuria, and 16% and 17% had schistosome ova, respectively. PCR analysis showed that 57% and 40% were positive for the infection in Anglican primary school, Ebute Afuye, and community primary school, Erepoto, respectively. PCR screening of the snails confirmed that four from Ebute Afuye and three from Erepoto were infected with schistosomes. PCR-RFLP showed that all the 14 snails were Bulinus truncatus while phylogenetic analysis of the sequenced partial cox1 gene corroborated the PCR-RFLP results.Conclusions:There was a high prevalence of S. haematobium infection among the participants detected by PCR, which was able to detect infection in cases otherwise shown to be negative by hematuria. We also observed that B. truncatus is one of the snail species responsible for the transmission of urinary schistosomiasis in the Epe community. For national control programs, it is very important that trends in the prevalence and intensity of schistosomiasis in urban cities be monitored.

The relationship between urinary schistosomiasis and the prevailing socio-economic factors of a rural community in Cameroon

The relationship between the transmission of urinary schistosomiasis and the prevailing socio-economic factors was investigated in some villages in Lagdo District of the Republic of Cameroon in 2005. Urine samples obtained from participants in the study were examined microscopically for the presence of eggs of Schistosoma haematobium. Questionnaires were administered to school children to study their perception of the disease, and local socio-economic factors that may stabilize the infection in the community. Schistosoma haematobium was confirmed amongst 39.2% of the study-population. Mixed infecfions of S. mansoni and S. haematobium occurred in only 4.5% of the pupils. Subjects aged 5-9 years were most infected (45.7%). Male subjects (23.5%) were significantly (p < 0.05) more infected than females (15.7%). There was a statistically significant difference in the distribution of urinary schistosomasis from villages studied (p < 0.05). Infection occurred most in Boule Village (70%). The type of water and the location of the village from the lake significantly influenced the rate of acquisition of schistosomiasis (p < 0.05). Children of farmers and fishermen were more infected (82.3%) and (95.2%) respectively than children of civil servants (50%). Children out-of-school were significantly more infected than those in school (p < 0.05). The study support the immediate treatment of subjects in these villages and the investigation of the endemicity of S. mansoni infection in the area. Keywords: urinary schistosomiasis, socio-economic factors, rural community, Cameroon.Nigerian Journal of Parasitology Vol. 29 (1) 2008 pp. 5-10

Studies on the biology and population parameters of &lt;i&gt;Bulinus globosus&lt;/i&gt; and &lt;i&gt;Bulinus truncatus&lt;/i&gt; in the laboratory

Investigation was made into some aspects of biology and population parameters of Bulinus globosus and Bulinus truncatus which are snails implicated in the transmission of urinary schistosomiasis in Agulu Lake Area of Anambra state, Nigeria. These snails were collected from the lake and reared in the laboratory. From observations, life tables were constructed and some population parameters calculated. The incubation period for the two species was 7-14 days while 21% of the egg was unviable for both species. The highest rate of oviposition by B. globosus was 261.64 ± 59.01 eggs/snail (week 20) while B. truncatus had 241.04 ± 52.87 at week 18. The net reproductive rate (ro), generation time (Tc) and capacity rate of increase (rc) for the two species were similar. Since both species are well adapted and thrive well at different arms of the lake, control of both species will remarkably reduce the infection rate of Schistosoma haematobium in the area. Keywords: Bulinus trucatus, Bulinus globosus, population parameters, control, S. haematobium.Nigerian Journal of Parasitology Vol. 29 (1) 2008 pp. 11-14

Geographical information systems (GIS) and risk maps of urinary schistosomiasis in Ogun State, Nigeria

Remotely-sensed environmental images and geographical information system (GIS) are used to develop risk maps of the probability occurrence of urinary schistosomiasis and population at risk in Ogun State, Nigeria. The model was developed using Arc View GIS 3.2a Software and incorporating infection, population, rainfall, vegetation, temperature, soil-types, altitude, and school locations data. The resulting risk maps created suggested that urinary schistosomiasis is widely distributed, occurring in all the local government areas in the state. The high-risk areas (&#8805 50% prevalence) were confined to foci in the north-western part of the state. The models correctly predicted both the presence and absence of infection, the probability risk at any locality in Ogun State, as well as estimating the population at risk. The model estimated that 98.99% of school-aged children in the state are living in urinary schistosomiasis-suitable areas and are at risk of infection. As such, necessary preventive measures should be incorporated into water resources, projects, which are known to promote urinary schistosomiasis transmission. This investigation provides for the first time, detailed and comprehensive maps of the distribution of urinary schistosomiasis in Ogun State, which would help guide control efforts. Keywords : GIS, risk maps, urinary schistosomiasis, school children, Ogun State. Nigerian Journal of Parasitology Vol. 29 (1) 2008 pp. 42-49

Studies on the morphology and compatibility between Schistosoma hæmatobium and the Bulinus sp. complex (gastropoda: planorbidae) in Cameroon

A description is given of the morphological variation of the shell, the radula features and the copulatory organ of Bulinus sp. (2n=36) from four populations in the western Cameroon crater lakes. To assess the role of diploid snails belonging to the Bulinus natalensis/tropicus complex in the transmission of urinary schistosomiasis in Cameroon, the relation between Bulinus sp. (from four Cameroon crater lakes) and Schistosoma haematobium (from three transmission foci) were studied. Bulinus sp. in the present study refers to the diploid snail (2n=36) tentatively identified as Bulinus natalensis or as Bulinus tropicus in the Cameroon crater lakes. The percentage infection of snails challenged ranged from 03.33 to 06.00% for Nchout Monoun population and from 01.85 to 04.76% for Monoun Ngouondam population. No progeny from Petponoun-East and Petponoun-West were experimentally successfully infected with S. haematobium. All the 351 snails dissected were euphallic. Previous malacological surveys revealed the absence of Bulinus sp. naturally infected with human schistosomes. These results suggested that Bulinus sp. was not susceptible to infection with S. haematobium in the Cameroon Western highland crater lakes. These observations justify the absence of transmission foci (for urinary schistosomiasis) in this area.

The effects of irrigated agriculture on the transmission of urinary schistosomiasis in the Middle and Upper Valleys of the Senegal River basin.

The importance of the increase in irrigated land on the perimeters of the Middle and Upper Valleys of the Senegal River basin, on the prevalence and intensity of urinary schistosomiasis, was investigated. Surveys were conducted, in May-June 1997, to determine the prevalence and intensity of Schistosoma haematobium infection among 1445 children aged 7-14 years: 1011 in 10 villages near Matam, and 434 in four villages near Bakel. Macrohaematuria was present in seven of the study villages (four near Matan and three near Bakel), whereas microhaematuria was present in all the villages, with prevalences of 10%-73%. A second survey, conducted, in June 1999, on 755 children from nine of the study villages near Matam, demonstrated significant increases in the prevalences of both micro- and macro-haematuria in three of the villages, all of which were adjacent to the Senegal River and practising irrigated agriculture. None of the other study villages re-surveyed was irrigating any of its agricultural land. A longitudinal survey was also carried out, between May 1997 and November 1998, on about 10% of the population (2272 subjects) of Nguidjilone, north of Matam; selective treatment with praziquantel (40 mg/kg) was given in May 1997, and mass treatment in May 1998. The data analysed were those relating to the 125 individuals who provided samples at each survey. Very severe infections (> 1000 eggs/10 ml urine) were seen in five subjects in May 1997. One year later (i.e. 1 year after the selective treatment), the prevalence of urinary schistosomiasis had increased in every age-group. Although prevalence had decreased slightly by November 1998 (6 months after the mass treatment), the intensity of the infections seen had increased in every age-group. At the end of the dry season (May-June 1997), Bulinus truncalus infected with schistosome cercariae were recovered from the Senegal River. However, immediately after the next rainy season (November 1997), no snails were found at any collection site on the river.

Transmission of urinary schistosomiasis in Sukumaland, Tanzania. 1. Snail infection rates and incidence of infection in school children.

Seasonal density fluctuations of Bulinus nasutus populations with accompanying Schistosoma haematobium infection rates in relation to rainfall and habitat water volumes were studied at Ukiriguru, Mwanza, Tanzania. Alongside the snail investigations, 50 school children initially negative for urinary schistosomiasis were examined regularly to determine seasonal incidence rates for the infection. Of the 17,646 B. nasutus collected in 2 years, 156 (0.88%) were found shedding cercariae. Snail populations fluctuated seasonally as influenced by rainfall through its effects on habitat water volume. Monthly snail infection rates ranged from 0.09% to 3.19% and were highest in February and March, at the time of the short dry period. Monthly incidence of S. haematobium in school children ranged between 2.6% and 12.5%, being highest in April and May. There was a significant linear association between monthly snail infection rates and S. haematobium incidence rates in school children (r2s = 0.65 in 1982/83; r2s = 0.87 in 1983/84) suggesting that the maximum transmission period for urinary schistosomiasis in the area occurs during the short dry period, sometime in February/March so that most of the infections in the community would be detected in April/May.

Transmission of urinary schistosomiasis after the introduction of snail control: a study of children at the Egypt-49 project by means of an egg-counting technique

Transmission of urinary schistosomiasis after the introduction of snail control: a study of children at the Egypt-49 project by means of an egg-counting technique

Schistosomiasis in the Western Aden protectorate: A preliminary study

1. 1) The literature on schistosomiasis in South-west Arabia is briefly reviewed. 2. 2) Transmission of urinary schistosomiasis by Bulinus beccari in the coastal plain of Aden and by Bulinus reticulatus in the middle heights in Upper Aulaqi State is demonstrated and supported by laboratory experiments. 3. 3) Experimental infections of Bulinus truncatus with both of the Aden strains of Schistosoma haematobium have failed to develop.