Rice irrigation and schistosomiasis in savannah and forest areas of Côte d'Ivoire

Prevalence and distribution of livestock schistosomiasis and fascioliasis in Côte d'Ivoire: results from a cross-sectional survey

BACKGROUND

Schistosoma and Fasciola are zoonotic parasites of public health and veterinary importance. However, while the epidemiology of schistosomiasis in humans is well studied, little is known about fascioliasis and schistosomiasis in livestock in Côte d'Ivoire. This study aimed to determine the prevalence and the distribution of livestock schistosomiasis and fascioliasis across Côte d'Ivoire. In 2018, we conducted a cross-sectional survey in abattoirs and farms in 13 departments of Côte d'Ivoire. In abattoirs, the mesenteric veins and livers of slaughtered cattle, sheep and goats were examined for adult Schistosoma and Fasciola flukes. Faeces from live cattle, goats and sheep were collected and examined for Schistosoma and Fasciola eggs using a sedimentation technique.

RESULTS

A total of 386 cattle, 174 goats and 151 sheep from abattoirs and 435 cattle, 22 goats and 176 sheep from farms were sampled. The observed prevalence of schistosomiasis was higher in slaughtered animals. Fascioliasis was more prevalent in farm animals. The prevalence of schistosomiasis in slaughtered cattle varied between 5.9% (95% confidence interval (CI): 0.7-19.7%) and 53.3% (95% CI: 37.9-68.3%) with the highest prevalence observed in Ouangolodougou in the North. Cattle from farms had a relatively low prevalence of schistosomiasis, with the highest prevalence found in Ouangolodougou (2.4%, 95% CI: 0.7-6.1%). The prevalence of fascioliasis varied considerably from one department to another, ranging from nil (95% CI: 0.0-18.5%) to 50.8% (95% CI: 43.4-58.2%), with the highest prevalence found in farm cattle in Dikodougou in the North. Sheep and goats had a lower prevalence of schistosomiasis and fascioliasis than cattle. In slaughtered animals, cattle aged 4 years and older were at highest risk for schistosomiasis (odds ratio (OR): 2.4; 95% CI: 1.0-5.6) and fascioliasis (OR: 2.1; 95% CI: 1.1-3.9). In farm animals, male cattle had higher odds of being infected with Schistosoma (OR: 4.3; 95% CI: 0.7-26.9) than females.

CONCLUSIONS

Our study confirms that schistosomiasis and fascioliasis are endemic in livestock across Côte d'Ivoire. A strategic control programme should be considered, especially for cattle, including providing drinking water in troughs to reduce faecal contamination of water sources by cattle.

Modeling schistosomiasis spatial risk dynamics over time in Rwanda using zero-inflated Poisson regression

The recorded clinical cases of S. mansoni at primary health facility level contain an excessive number of zero records. This could mean that no S. mansoni infection occurred (a true zero) in the health facility service area but it could also that at least one infection occurred but none were reported or diagnosed (a false zero). Standard statistical analysis, using exploratory or confirmatory spatial regression, fail to account for this type of data insufficiency. This study developed a zero-inflated Poisson model to explore the spatiotemporal variation in schistosomiasis risk at a fine spatial scale. We used environmental data generated at primary health facility service area level as explanatory variables affecting transmission risk. Identified risk factors were subsequently used to project the spatial variability of S. mansoni infection risk for 2050. The zero-inflated Poisson model shows a considerable increase of relative risk of the schistosomiasis over one decade. Furthermore, the changes between the risk in 2009 and forecasted risk by 2050 indicated both persistent and emerging areas with high relative risk of schistosomiasis infection. The risk of schistosomiasis transmission is 69%, 29%, and 50% higher in areas with rice cultivation, proximity to rice farms, and proximity to a water body respectively. The prediction and forecasting maps provide a valuable tool for monitoring schistosomiasis risk in Rwanda and planning future disease control initiatives in wetland ecosystem development context.

A quantitative assessment of the level of knowledge, attitude and practices of farmworkers regarding schistosomiasis in a rural community in South Africa

Background

Schistosomiasis is associated with agriculture and water development schemes, and farmworkers are particularly vulnerable to this disease because of their regular contact with water.

Aim

To determine the level of knowledge, attitude and practices (KAP) of farmworkers regarding schistosomiasis.

Setting

This study was conducted in Vuvha, a rural community under Makhado municipality, Vhembe district, Limpopo Province, South Africa.

Methods

A quantitative, cross-sectional design was used. A self-administered questionnaire was used for data collection, and data were analysed using descriptive and inferential statistical techniques.

Results

The majority were knowledgeable about the cause of schistosomiasis (84.3%), knew the mode of transmission of the disease (90.2%). However, about half of the participants knew the symptoms of schistosomiasis. Sixty-eight (33.4%) believed that schistosomiasis was not a problem in their community. The majority (77.9%) agreed that it was abnormal to pass blood in urine, while 85.8% agreed that medical consultation was the right thing to do when symptoms are observed. Fifty-five participants (27.0%) reported ever passing bloody urine. Among those who passed bloody urine, 43 (78.2%) consulted a doctor. Fifty-two (26.0%) participants reported ever being treated for schistosomiasis.

Conclusion

The level of knowledge about the cause of schistosomiasis is high among the participants; similarly, there are positive attitudes and good practices shown in this study, but there are some gaps that need to be addressed. Efforts should be made to continue to educate farmworkers because they are at an increased risk for contracting schistosomiasis.

Prevalence and Risk Factors for Schistosomiasis among Schoolchildren in two Settings of Côte d'Ivoire

Schistosomiasis is a parasitic disease affecting more than 250 million people, primarily in sub-Saharan Africa. In Côte d’Ivoire both Schistosoma haematobium (causing urogenital schistosomiasis) and Schistosoma mansoni (causing intestinal schistosomiasis) co-exist. This study aimed to determine the prevalence of S. haematobium and S. mansoni and to identify risk factors among schoolchildren in the western and southern parts of Côte d’Ivoire. From January to April 2018, a cross-sectional study was carried out including 1187 schoolchildren aged 5–14 years. Urine samples were examined by a filtration method to identify and count S. haematobium eggs, while stool samples were subjected to duplicate Kato-Katz thick smears to quantify eggs of S.mansoni and soil-transmitted helminths. Data on sociodemographic, socioeconomic, and environmental factors were obtained using a pretested questionnaire. Multivariate logistic regression was employed to test for associations between variables. We found a prevalence of S. haematobium of 14.0% (166 of 1187 schoolchildren infected) and a prevalence of S. mansoni of 6.1% (66 of 1089 schoolchildren infected). In the southern part of Côte d’Ivoire, the prevalence of S. haematobium was 16.1% with a particularly high prevalence observed in Sikensi (35.6%), while S. mansoni was most prevalent in Agboville (11.2%). Swimming in open freshwater bodies was the main risk factor for S. haematobium infection (adjusted odds ratio (AOR) = 127.0, 95% confidence interval (CI): 25.0–634.0, p < 0.001). Fishing and washing clothes in open freshwater bodies were positively associated with S. haematobium and S. mansoni infection, respectively. Preventive chemotherapy using praziquantel should be combined with setting-specific information, education, and communication strategies in order to change children’s behavior, thus avoiding contact with unprotected open freshwater.

Prevalence of Schistosomiasis in a neglected community, South western Nigeria at two points in time, spaced three years apart

Background

In recent years, the prevalence of schistosomiasis, a neglected tropical infection, has increased in underprivileged rural communities characterized by poverty.

Objective

This cross-sectional community-based study was carried out to determine the prevalence of urinary schistosomiasis in a neglected community of Apojola community, South-Western Nigeria at two points in time, spaced three years apart

Method and results

A total of 145 participants were screened and 44.1% were diagnosed to have urinary Schistosoma haematobium infection after sedimentation and microscopy. The prevalence of schistosomiasis among females was higher (45.3%) than that among males (42.4%) but not significantly different (0.723). The prevalence of participants with light infection (26%) was significantly higher than those with heavy infection (11.0%). The predisposing factors with statistically significant association with Schistosoma haematobium infection were age (0.000), level of education (0.002), eating/selling of snails (0.037), occupation (0.000), drinking water (0.001), swimming (0.008), and washing in a river (0.019).

Conclusion

These findings indicate that the study area is still endemic to urinary schistosomiasis after three years of research and school-age children and teenagers are the populations at risk of urinary schistosomiasis. Community health education on the cause, mode of transmission, prevention, and prompt treatment of schistosomiasis is recommended.

Risk factors for schistosomiasis in an urban area in northern Côte d'Ivoire

Background

Schistosomiasis is a water-based disease transmitted by trematodes belonging to the genus Schistosoma. The aim of this study was to assess the relationship between the prevalence of schistosomiasis and access to water, sanitation and hygiene (WASH) and environmental and socioeconomic factors in the city of Korhogo, northern Côte d'Ivoire.

Methods

A cross-sectional study including 728 randomly selected households was conducted in Korhogo in March 2015. The heads of the households were interviewed about access to WASH and environmental and socioeconomic factors. All children abed between 5 and 15 years living in the households were selected to provide stool and urine samples for parasitological diagnosis of Schistosoma mansoni and Schistosoma haematobium infection. The relationship between infection with S. mansoni and potential risk factors was analysed by a mixed logistic regression model with ‘household’ as a random factor. Likelihood ratio tests were used to identify factors that were significantly associated with a Schistosoma spp. infection.

Results

The overall prevalence of schistosomiasis among school-aged children in Korhogo was 1.9% (45/2341) composed of 0.3% (3/1248) S. haematobium and 3.5% (42/1202) S. mansoni. Due to the low prevalence of S. haematobium infection, risk factor analysis was limited to S. mansoni. Boys were 7.8 times more likely to be infected with S. mansoni than girls. Children between 10 and 15 years of age were 3.8 times more likely to be infected than their younger counterparts aged 5-10 years. Moreover, living in a house further away from a water access point (odds ratio [OR] = 0.29, 95% confidence interval [CI]: 0.13–0.70) and abstaining from swimming in open freshwater bodies (OR = 0.16, 95% CI: 0.04–0.56) were significantly associated with decreased odds of S. mansoni infection. The socioeconomic status did not appear to influence the prevalence of S. mansoni.

Conclusions

A strategy to reduce the incidence of schistosomiasis should focus on health education to change the behaviour of populations at risk and encourage communities to improve sanitation and infrastructure in order to reduce contact with surface water.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0431-6) contains supplementary material, which is available to authorized users.

Towards elimination of schistosomiasis after 5000 years of endemicity in Egypt

Schistosomiasis is a snail-transmitted infectious disease caused by a long lasting infection with a blood fluke of the genus Schistosoma. S. haematobium and S. mansoni are the species endemic in Egypt. The country has been plagued and seriously suffered from schistosomiasis over the past 5000 years. Great strides had been done in controlling the disease since 1922. The history, epidemiology and the different control approaches were reviewed. Currently, Egypt is preparing towards schistosomiasis elimination by 2020. The new strategy depends on four main axes; large scale treatment in all areas of residual transmission by targeting entire populations with PZQ, intensified snail control, heath education and behavioral changes and expansion of the complementary public health interventions. While on the road towards elimination, we addressed here the important challenges, lessons and the key issues from the different control strategies to help the achievement of our goal. Notably, frangibility of the drug based control, emergence of resistance against PZQ, persistence of some hot spots areas, the need of further control efforts to the high risk individuals and community involvement in the control programs, reconsideration of diagnostic tests used in surveillance, and continous monitoring of the field to detect changes in the snail intermediate host. Importantly, the adaptation between the parasite and its intermediate snail host throughout water bodies in Egypt merits attention as Schistosoma infection can be introduced to the new reclaimed areas. This review may help supplying information for the policy makers to tailor control measures suitable to the local context that could help in the transfer from control to elimination.

Urogenital schistosomiasis in Cabo Delgado, northern Mozambique: baseline findings from the SCORE study

BACKGROUND

The results presented here are part of a five-year cluster-randomised intervention trial that was implemented to understand how best to gain and sustain control of schistosomiasis through different preventive chemotherapy strategies. This paper presents baseline data that were collected in ten districts of Cabo Delgado province, northern Mozambique, before treatment.

METHODS

A cross-sectional study of 19,039 individuals was sampled from 144 villages from May to September 2011. In each village prevalence and intensity of S. haematobium were investigated in 100 children first-year students (aged 5-8 years), 100 school children aged 9-12 years (from classes 2 to 7) and 50 adults (20-55 years). Prevalence and intensity of S. haematobium infection were evaluated microscopically by two filtrations, each of 10 ml, from a single urine specimen. Given that individual and community perceptions of schistosomiasis influence control efforts, community knowledge and environmental risk factors were collected using a face-to-face interview. Data were entered onto mobile phones using EpiCollect. Data summary was made using descriptive statistics. Chi-square and logistic regression were used to determine the association between dependent and independent variables.

RESULTS

The overall prevalence of urogenital schistosomiasis was 60.4% with an arithmetic mean intensity of infection of 55.8 eggs/10 ml of urine. Heavy infections were detected in 17.7%, of which 235 individuals (6.97%) had an egg count of 1000 eggs/10 ml or more. There was a significantly higher likelihood of males being infected than females across all ages (62% vs 58%; P < 0.0005). Adolescents aged 9-12 years had a higher prevalence (66.6%) and mean infection intensity (71.9 eggs/10 ml) than first-year students (63.1%; 58.2 eggs/10 ml). This is the first study in Mozambique looking at infection rates among adults. Although children had higher levels of infection, it was found here that adults had a high average prevalence and intensity of infection (44.5%; 23.9 eggs/10 ml). Awareness of schistosomiasis was relatively high (68.6%); however, correct knowledge of how schistosomiasis is acquired was low (23.2%) among those who had heard of the disease. Schistosomiasis risk behaviour such as washing (91.3%) and bathing (86.7%) in open water sources likely to be infested with host snails was high.

CONCLUSIONS

Urogenital schistosomiasis is widespread in Cabo Delgado. In addition, poor community knowledge about the causes of schistosomiasis and how to prevent it increases the significant public health challenge for the national control program. This was the first study in Mozambique that examined infection levels among adults, where results showed that S. haematobium infection was also extremely high. Given that this controlled trial aims to understand the impact of different combinations of schistosomiasis control through treatment of communities, schools, and treatment holidays over a five-year period, these findings highlight the importance of examining the impact of different treatment approaches also in adults.

TRIAL REGISTRATION

The trials have been registered with the International Standard Randomised Controlled Trial registry under ISRCT 14117624 Mozambique (14 December 2015).

Diversity of inland valleys and opportunities for agricultural development in Sierra Leone

Inland valleys are becoming increasingly important agricultural production areas for rural households in sub-Saharan Africa due to their relative high and secure water availability and soil fertility. In addition, inland valleys are important as water buffer and biodiversity hot spots and they provide local communities with forest, forage, and fishing resources. As different inland-valley ecosystem functions may conflict with agricultural objectives, indiscriminate development should be avoided. This study aims to analyze the diversity of inland valleys in Sierra Leone and to develop guidelines for more precise interventions. Land use, biophysical and socio-economic data were analyzed on 257 inland valleys using spatial and multivariate techniques. Five cluster groups of inland valleys were identified: (i) semi-permanently flooded with high soil organic carbon (4.2%) and moderate available phosphorus (10.2 ppm), mostly under natural vegetation; (ii) semi-permanently flooded with low soil organic carbon (1.5%) and very low available phosphorus (3.1 ppm), abandoned by farmers; (iii) seasonally flooded with moderate soil organic carbon (3.1%) and low available phosphorus (8.3 ppm), used for rainfed rice and off-season vegetables produced without fertilizer application for household consumption and market; (iv) well drained with moderate soil organic carbon (3.8%) and moderate available phosphorus (10.0 ppm), used for rainfed rice and off-season vegetables produced with fertilizer application for household consumption and market; and (v) well drained with moderate soil organic carbon (3.6%) and moderate available phosphorus (11 ppm), used for household consumption without fertilizer application. Soil organic carbon, available phosphorus, hydrological regime, physical accessibility and market opportunity were the major factors affecting agricultural intensification of inland valleys. Opening up the areas in which inland valleys occur through improved roads and markets, and better water control through drainage infrastructures along with an integrated nutrient management would promote the sustainable agricultural use of inland valleys.

Dynamics of freshwater snails and Schistosoma infection prevalence in schoolchildren during the construction and operation of a multipurpose dam in central Côte d'Ivoire

Background

The construction and operation of small multipurpose dams in Africa have a history of altering the transmission of water-based diseases, including schistosomiasis. The current study was designed to investigate the abundance and dynamics of schistosomiasis intermediate host snails and Schistosoma infections in humans during the construction and the first years of operation of a small multipurpose dam in Côte d’Ivoire.

Methods

The study was carried out in Raffierkro and four neighbouring villages in central Côte d’Ivoire between 2007 and 2012. Snails were collected by two experienced investigators using scoops and forceps for 15 min at each site. Snails were identified at genera and, whenever possible, species level, and subjected to testing for cercarial shedding. Schoolchildren aged 6–15 years were examined once every year for Schistosoma haematobium and S. mansoni infection, using urine filtration and duplication Kato-Katz thick smears, respectively. Additionally, 551 adults were examined for Schistosoma infection before (June 2007) and 359 individuals 2 years after dam construction (June 2009).

Results

Overall, 1 700 snails belonging to nine different genera were collected from 19 sampling sites. Bulinus (potential intermediate host snails of S. haematobium) and Pila were the most common genera, whereas Biomphalaria (potential intermediate host snail of S. mansoni), Lymnaea, Physa and Melanoides were found in two villages. During the first-year sampling period, 65 snails were collected, of which 13 (20%) were schistosomiasis intermediate hosts. In subsequent years, out of 1 635 snails collected, 1 079 (66%) were identified as potential intermediate host for schistosomiasis, but none were shedding cercariae. The prevalence of S. mansoni among adults in the study area was low (0.4% in 2007 and 0.3% in 2009), whereas the prevalence of S. haematobium declined from 13.9% to 2.9% in this two-year period.

Conclusions

The low prevalence of schistosomiasis in humans and the absence of infected intermediate host snails during the construction and early phase of operation of a small multipurpose dam suggest that there was no or only very little local transmission. However, the considerable increase in the number of intermediate host snails and their dispersion in irrigation canals call for rigorous surveillance, so that adequate public health measures can be taken in case of early signs of an outbreak.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0305-3) contains supplementary material, which is available to authorized users.

Sustaining the Control of Schistosoma mansoni in Western Côte d'Ivoire: Baseline Findings Before the Implementation of a Randomized Trial

We report baseline findings before the implementation of a 4-year intervention trial designed to assess the impact of three different school-based treatment schedules with praziquantel to sustain the control of intestinal schistosomiasis. The baseline survey was conducted in 75 schools of western Côte d'Ivoire previously identified with moderate Schistosoma mansoni endemicity (prevalence: 10-24% in children aged 13-14 years). Three stool samples collected over consecutive days were subjected to duplicate Kato-Katz thick smears each. A questionnaire was administered to collect village-specific information that is relevant for schistosomiasis transmission. Overall, 4,953 first graders (aged 5-8 years) and 7,011 school children (aged 9-12 years) had complete parasitologic data. The overall prevalence of S. mansoni was 5.4% among first graders and 22.1% in 9- to 12-year-old children. Open defecation was practiced in all villages. The current baseline findings will be important to better understand the dynamics of S. mansoni prevalence and intensity over the course of this trial that might be governed by village characteristics and specific treatment interventions.

Toward an open-access global database for mapping, control, and surveillance of neglected tropical diseases

Background

After many years of general neglect, interest has grown and efforts came under way for the mapping, control, surveillance, and eventual elimination of neglected tropical diseases (NTDs). Disease risk estimates are a key feature to target control interventions, and serve as a benchmark for monitoring and evaluation. What is currently missing is a georeferenced global database for NTDs providing open-access to the available survey data that is constantly updated and can be utilized by researchers and disease control managers to support other relevant stakeholders. We describe the steps taken toward the development of such a database that can be employed for spatial disease risk modeling and control of NTDs.

Methodology

With an emphasis on schistosomiasis in Africa, we systematically searched the literature (peer-reviewed journals and ‘grey literature’), contacted Ministries of Health and research institutions in schistosomiasis-endemic countries for location-specific prevalence data and survey details (e.g., study population, year of survey and diagnostic techniques). The data were extracted, georeferenced, and stored in a MySQL database with a web interface allowing free database access and data management.

Principal Findings

At the beginning of 2011, our database contained more than 12,000 georeferenced schistosomiasis survey locations from 35 African countries available under http://www.gntd.org. Currently, the database is expanded to a global repository, including a host of other NTDs, e.g. soil-transmitted helminthiasis and leishmaniasis.

Conclusions

An open-access, spatially explicit NTD database offers unique opportunities for disease risk modeling, targeting control interventions, disease monitoring, and surveillance. Moreover, it allows for detailed geostatistical analyses of disease distribution in space and time. With an initial focus on schistosomiasis in Africa, we demonstrate the proof-of-concept that the establishment and running of a global NTD database is feasible and should be expanded without delay.

There is growing interest in the scientific community, health ministries, and other organizations to control and eventually eliminate neglected tropical diseases (NTDs). Control efforts require reliable maps of NTD distribution estimated from appropriate models and survey data on the number of infected people among those examined at a given location. This kind of data is often available in the literature as part of epidemiological studies. However, an open-access database compiling location-specific survey data does not yet exist. We address this problem through a systematic literature review, along with contacting ministries of health, and research institutions to obtain disease data, including details on diagnostic techniques, demographic characteristics of the surveyed individuals, and geographical coordinates. All data were entered into a database which is freely accessible via the Internet (http://www.gntd.org). In contrast to similar efforts of the Global Atlas of Helminth Infections (GAHI) project, the survey data are not only displayed in form of maps but all information can be browsed, based on different search criteria, and downloaded as Excel files for further analyses. At the beginning of 2011, the database included over 12,000 survey locations for schistosomiasis across Africa, and it is continuously updated to cover other NTDs globally.

Impact of temperature and precipitation on propagation of intestinal schistosomiasis in an irrigated region in Ethiopia: suitability of satellite datasets

OBJECTIVE

To assess the suitability of satellite temperature and precipitation datasets for investigating the dependence of Schistosoma mansoni disease transmission on meteorological conditions in an irrigated agricultural region in Ethiopia.

METHODS

Data used were monthly number of patients infected with S. mansoni and seeking treatment at the local hospital, monthly maximum air temperature from a local weather station, monthly average land surface temperature from MODIS satellite data, monthly total precipitation from a local rain gauge and precipitation estimates from four widely used satellite products, namely, TMPA 3B42RT, TMPA 3B42, CMORPH and PERSIANN. The number of patients was used as proxy for vector abundance.

RESULTS

Temperature and precipitation play a role in the transmission of S. mansoni disease. There is a weak but significant positive correlation between monthly maximum air temperature derived from a meteorological station (or average land surface temperature derived from MODIS satellite product) and the number of patients in the same month. There is a significant negative correlation between monthly precipitation volume (derived from rain gauge or satellite data) and number of patients at lags of 1 and 2 months.

CONCLUSION

Satellite temperature and precipitation products provide useful information to understand and infer the relationship between meteorological conditions and S. mansoni prevalence.

Selection and quantification of infection endpoints for trials of vaccines against intestinal helminths

Vaccines against human helminths are being developed but the choice of optimal parasitological endpoints and effect measures to assess their efficacy has received little attention. Assuming negative binomial distributions for the parasite counts, we rank the statistical power of three measures of efficacy: ratio of mean parasite intensity at the end of the trial, the odds ratio of infection at the end of the trial, and the rate ratio of incidence of infection during the trial. We also use a modelling approach to estimate the likely impact of trial interventions on the force of infection, and hence statistical power. We conclude that (1) final mean parasite intensity is a suitable endpoint for later phase vaccine trials, and (2) mass effects of trial interventions are unlikely to appreciably reduce the force of infection in the community - and hence statistical power - unless there is a combination of high vaccine efficacy and a large proportion of the population enrolled.

Factors associated with urinary schistosomiasis in two peri-urban communities in south-western Nigeria

In Nigeria, there is only very limited epidemiological information on which the control of human urinary schistosomiasis could be based. In a cross-sectional study, therefore, the prevalences and intensities of, and risk factors for, human infection with Schistosoma haematobium infection were explored in two endemic peri-urban villages in the south-western state of Osun. The villagers' knowledge about the infection and demographic, socio-economic and environmental variables were recorded using a structured questionnaire. Of the 1023 individuals who were investigated, 634 (62.0%) were found infected, with a mean (S.D.) overall intensity of 114.2 (327.7) eggs/10 ml urine. The subjects aged 10-14 years had both the highest prevalence (83.6%) and the highest mean (S.D.) intensity of infection [196.67 (411.7) eggs/10 ml urine]. Most (70.0%) of the subjects appeared to have no knowledge of the transmission of S. haematobium. The results of multivariate regression analysis indicated that infection and moderate-heavy infection (i.e. >50 eggs/10 ml urine) were both associated with: a low family income, of <U.S.$500/month [with adjusted odds ratios (aOR) of 3.72 and 3.35, respectively], the number of children aged 10-15 years living in the household (with aOR of 1.60 and 1.99, respectively), not living with biological parents (with aOR of 1.93 and 5.21, respectively), and living close to (i.e. within a 30-min walk of) the local river (with aOR of 1.38 and 1.61, respectively). Literacy of the family head was, however, a protective factor (with corresponding aOR of 0.28 and 0.30, respectively). Human urinary schistosomiasis appears to be highly endemic in peri-urban/rural Nigeria and closely associated with poverty. To reduce the transmission of S. haematobium in endemic communities, health education that is not only of high quality but also culturally sensitive is needed.

Bayesian geostatistical modelling for mapping schistosomiasis transmission

Progress has been made in mapping and predicting the risk of schistosomiasis using Bayesian geostatistical inference. Applications primarily focused on risk profiling of prevalence rather than infection intensity, although the latter is particularly important for morbidity control. In this review, the underlying assumptions used in a study mapping Schistosoma mansoni infection intensity in East Africa are examined. We argue that the assumption of stationarity needs to be relaxed, and that the negative binomial assumption might result in misleading inference because of a high number of excess zeros (individuals without an infection). We developed a Bayesian geostatistical zero-inflated (ZI) regression model that assumes a non-stationary spatial process. Our model is validated with a high-quality georeferenced database from western Côte d'Ivoire, consisting of demographic, environmental, parasitological and socio-economic data. Nearly 40% of the 3818 participating schoolchildren were infected with S. mansoni, and the mean egg count among infected children was 162 eggs per gram of stool (EPG), ranging between 24 and 6768 EPG. Compared to a negative binomial and ZI Poisson and negative binomial models, the Bayesian non-stationary ZI negative binomial model showed a better fit to the data. We conclude that geostatistical ZI models produce more accurate maps of helminth infection intensity than the spatial negative binomial ones.

Risk factors for Schistosoma mansoni and hookworm in urban farming communities in western Côte d'Ivoire

OBJECTIVES

To identify risk factors for Schistosoma mansoni and hookworm infections in urban farming communities, and to investigate small-scale spatial patterns of infection prevalence.

METHODS

A cross-sectional survey was carried out in 113 farming households (586 individuals) and 21 non-farming households (130 individuals) from six agricultural zones in the town of Man, western Côte d'Ivoire. Heads of households were interviewed on common agricultural activities, land and water use, education attainment, socioeconomic status and sanitation facilities. Household members provided stool specimens that were processed by the Kato-Katz technique and a formol-ether concentration method and diagnosed for S. mansoni, hookworms and other soil-transmitted helminths and intestinal protozoa. Bayesian statistics were employed for spatial analyses.

RESULTS

The prevalences of S. mansoni and hookworm in farming households were 51.4% and 24.7%, respectively. Risk factors for a S. mansoni infection comprised living in close proximity to the Kô River, water contact with irrigation wells and ponds and low education attainment. Living in zones of smallholder irrigated rice plots or large rice perimeters, using water from domestic wells, and low socioeconomic status were risk factors for a hookworm infection. We found significant spatial heterogeneity between agricultural zones, with the highest infection prevalences of S. mansoni and hookworm in the zone where there was a large rice perimeter.

CONCLUSIONS

In this urban setting, both S. mansoni and hookworm infections were related to specific agricultural activities. Health education and active participation of urban farmers for the control of schistosomiasis and soil-transmitted helminthiasis is recommended.

Bayesian geostatistical prediction of the intensity of infection with Schistosoma mansoni in East Africa

A Bayesian geostatistical model was developed to predict the intensity of infection with Schistosoma mansoni in East Africa. Epidemiological data from purpose-designed and standardized surveys were available for 31,458 schoolchildren (90% aged between 6 and 16 years) from 459 locations across the region and used in combination with remote sensing environmental data to identify factors associated with spatial variation in infection patterns. The geostatistical model explicitly takes into account the highly aggregated distribution of parasite distributions by fitting a negative binomial distribution to the data and accounts for spatial correlation. Results identify the role of environmental risk factors in explaining geographical heterogeneity in infection intensity and show how these factors can be used to develop a predictive map. Such a map has important implications for schisosomiasis control programmes in the region.

Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at risk

An estimated 779 million people are at risk of schistosomiasis, of whom 106 million (13.6%) live in irrigation schemes or in close proximity to large dam reservoirs. We identified 58 studies that examined the relation between water resources development projects and schistosomiasis, primarily in African settings. We present a systematic literature review and meta-analysis with the following objectives: (1) to update at-risk populations of schistosomiasis and number of people infected in endemic countries, and (2) to quantify the risk of water resources development and management on schistosomiasis. Using 35 datasets from 24 African studies, our meta-analysis showed pooled random risk ratios of 2.4 and 2.6 for urinary and intestinal schistosomiasis, respectively, among people living adjacent to dam reservoirs. The risk ratio estimate for studies evaluating the effect of irrigation on urinary schistosomiasis was in the range 0.02-7.3 (summary estimate 1.1) and that on intestinal schistosomiasis in the range 0.49-23.0 (summary estimate 4.7). Geographic stratification showed important spatial differences, idiosyncratic to the type of water resources development. We conclude that the development and management of water resources is an important risk factor for schistosomiasis, and hence strategies to mitigate negative effects should become integral parts in the planning, implementation, and operation of future water projects.

Ethnopharmacological survey of plants used for the treatment of schistosomiasis in Niono District, Mali

In Mali the use of traditional medicine is a wide spread phenomenon, not only because of its cultural importance, but also as the majority of people cannot afford the western drugs or medicines. In Mali, the Office du Niger area constitutes the main zone of schistosomiasis transmission where both Schistosoma mansoni and Schistosoma haematobium are encountered. An ethnopharmacological survey, using questionnaire, was conducted in the Office du Niger area of the Niono District to determine the plants used against schistosomiasis amongst traditional healers. Forty healers from 21 villages of six different health areas were interviewed. All interviewed healers knew about urinary schistosomiasis, while only six knew about the intestinal form. The presence of blood in urine was reported as the main symptom of urinary schistosomiasis. Fifty-five plants belonging to 30 families were reported to be used alone for treating urinary and intestinal schistosomiasis, while nine combinations of plants were used against the urinary form of the disease. Cissus quadrangularis and Stylosanthes erecta were the plants most frequently used and were reported for the first time, to be used against schistosomiasis in Mali.

The Role of Ecotones in Emerging Infectious Diseases

Recognition of the significance of the boundary between ecological systems, often referred to as the ecotone, has a long history in the ecological sciences and in zoonotic disease research. More recent research in landscape ecology has produced an expanded view of ecotones and elaboration of their characteristics and functions in ecosystems. Parallel research on emerging infectious diseases (EIDs) and the causes of increased rates of pathogen transmission, spread, and adaptation suggests a correspondence between ecotonal processes and the ecological and evolutionary processes responsible for zoonotic and vector-borne emerging infections. A review of the literature suggests that ecotones play a role in a number of the most important EIDs. Yet these are the only diseases for which specific landscape ecological information exists in the literature or disease reports. However, the similar disease ecologies of these with about half of the approximately 130 zoonotic EIDs suggests ecotones, particularly their anthropogenic origination or modification, may be generally associated with ecotones and the global trend of increasing EIDs.