Data on the pre-MDA and post MDA interventions for Schistosoma mansoni and Schistosoma haematobium in a co-endemic focus in Uganda: 1951-2011.

The dataset for this article contains Urinary and Intestinal Schistosomiasis from Lango region, northern Uganda which is the only known co-endemic region for S.mansoni and S.haematobium. Reported in the data, is the retrospective data review for historical information before interventions were implemented before 2003 and after interventions were implemented in 2003 by the national control program. In 2007 and 2011, parasitological surveys were conducted in the region to validate Schistosomiasis trends following World Health Organization (WHO) guidelines for surveys. In addition, malacological surveys were undertaken in 2007 to assess local transmission potential. The dataset can provide an insight into the health implications of Schistosomiasis control in co-endemic focus in Uganda, "The epidemiology of schistosomiasis in Lango region Uganda 60 years after Schwetz 1951: Can schistosomiasis be eliminated through mass drug administration without other supportive control measures?" (Adriko et al., 2018) [10].

The epidemiology of schistosomiasis in Lango region Uganda 60 years after Schwetz 1951: Can schistosomiasis be eliminated through mass drug administration without other supportive control measures?

INTRODUCTION: Lango region is the only known endemic region for urinary and intestinal schistosomiasis in Uganda. Although there has been no significant improvement in sanitation and safe water supply in the region over years, the endemicity and prevalence of Schistosoma haematobium, in particular, have declined, perhaps due to yearly mass treatment campaigns implemented since 2003. METHODS: We report the epidemiology of Urinary and Intestinal schistosomiasis in Lango since 1951-2011 determined through Microscopic examinations for S. mansoni and S. haematobium respectively. A retrospective data review from 195 to 2011 was done to establish the prevalence over the years in the region. We performed Poisson regression analysis to observe trends in epidemiology before and after control was initiated in 2002. In addition, malacological surveys were undertaken in 2007 to assess local transmission potential. FINDINGS: Contrary to earlier records, S. haematobium was low and confined to a few putative foci, with declined in infections from 28.2% in 1951 to 2.48% by 2011. Although this decline can be attributed to control, this was already much lower in 1967 than 1951, long before control interventions began suggesting that environmental changes may have made the habitat less suitable for the transmission of S. haematobium. Compared to the historical records S. mansoni prevalence first increased up immediately before control interventions in 2003, significantly declined (p=<0.001) until 2007. However, in 2007 and 2011 declined insignificant, (p = 0.656). No snail has ever been isolated shedding S. haematobium cercariae but many Bulinus snail spp. were found shedding S. bovis cercariae. CONCLUSION: This suggests that a combination of environmental and mass treatment has had a significant impact on transmission in Lango region.

Evaluation of circulating cathodic antigen (CCA) urine-cassette assay as a survey tool for Schistosoma mansoni in different transmission settings within Bugiri District, Uganda.

Diagnosis of schistosomiasis at the point-of-care (POC) is a growing topic in neglected tropical disease research. There is a need for diagnostic tests which are affordable, sensitive, specific, user-friendly, rapid, equipment-free and delivered to those who need it, and POC is an important tool for disease mapping and guiding mass deworming. The aim of present study was to evaluate the relative diagnostic performance of two urine-circulating cathodic antigen (CCA) cassette assays, one commercially available and the other in experimental production, against results obtained using the standard Kato-Katz faecal smear method (six thick smears from three consecutive days), as a 'gold-standard', for Schistosoma mansoni infection in different transmission settings in Uganda. Our study was conducted among 500 school children randomly selected across 5 schools within Bugiri district, adjacent to Lake Victoria in Uganda. Considering results from the 469 pupils who provided three stool samples for the six Kato-Katz smears, 293 (76%) children had no infection, 109 (23%) were in the light intensity category, while 42 (9%) and 25 (5%) were in the moderate and heavy intensity categories respectively. Following performance analysis of CCA tests in terms of sensitivity, specificity, negative and positive predictive values, overall performance of the commercially available CCA test was more informative than single Kato-Katz faecal smear microscopy, the current operational field standard for disease mapping. The current CCA assay is therefore a satisfactory method for surveillance of S. mansoni in an area where disease endemicity is declining due to control interventions. With the recent resolution on schistosomiasis elimination by the 65th World Health Assembly, the urine POC CCA test is an attractive tool to augment and perhaps replace the Kato-Katz sampling within ongoing control programmes.

Intestinal schistosomiasis in chimpanzees on Ngamba Island, Uganda: observations on liver fibrosis, schistosome genetic diversity and praziquantel treatment.

Despite treatment with praziquantel (PZQ) at 40 mg/kg in food, several chimpanzees on Ngamba Island Chimpanzee Sanctuary (NICS) continue to excrete eggs of Schistosoma mansoni. To monitor disease, 8 animals were closely examined under anaesthesia in March 2011 with portable ultrasonography and by rectal snip biopsy. Schistosome genetic diversity had been previously assayed within 4 of these chimpanzees, finding extensive diversity with 27 DNA barcodes encountered, although none was common to all animals. Calcified schistosome eggs were found in the rectal snips from 5 chimpanzees and liver fibrosis was clearly documented, indicative of progressive disease in 6 animals, the latter being surprisingly advanced in a younger chimpanzee. All 8 animals were treated under anaesthesia by oral gavage with PZQ at 60 mg/kg dosing that was well tolerated. These animals were again re-examined in June 2012 using stool and urine sampling. Only 1 chimpanzee appeared to be free from infection and active egg excretion was confirmed in 6 animals. If intestinal schistosomiasis is to be controlled within this setting, a long-term disease management plan is required which should combine active case-detection with an insistent treatment regime with praziquantel for these chimpanzees, exploring perhaps the performance of even higher dosing.

Notes on the use of urine-CCA dipsticks for detection of intestinal schistosomiasis in preschool children.

Urine-dipstick diagnostic tests that detect schistosome circulating cathodic antigen (CCA) have the potential to provide more sensitive and rapid testing for intestinal schistosomiasis in field-based surveys; this is especially so when examining preschool children, from whom it may be difficult to obtain consecutive stool samples. To assess the performance of urine dipsticks, 569 preschool children from four villages along the shore of Lake Albert, Uganda, were screened for Schistosoma mansoni by Kato-Katz (K-K) examination of a single stool sample and CCA urine dipsticks. The prevalence of infection was 32.2% by K-K and 40.0% by CCA tests. Sensitivity and specificity were influenced by whether 'trace' results from the CCA test were characterised as positive or negative for infection with S. mansoni; ambiguities around this issue need to be resolved. Nevertheless, the CCA test showed particular promise for routine epidemiological screening in this setting.

Efficacy of praziquantel syrup versus crushed praziquantel tablets in the treatment of intestinal schistosomiasis in Ugandan preschool children, with observation on compliance and safety.

Preschool children (aged ≤5 years) have so far been overlooked by mass treatment campaigns targeting schistosomiasis, even though praziquantel (PZQ) has been shown to be well tolerated and effective within this age group. The WHO provided the Ugandan Ministry of Health with a syrup formulation of PZQ with the aim of assessing its safety and efficacy in comparison with crushed PZQ tablets for the treatment of intestinal schistosomiasis in preschool children. This study included 1144 preschool children randomly assigned to two treatment arms (PZQ syrup or crushed PZQ tablet) regardless of infection status for direct comparison. Diagnosis of intestinal schistosomiasis was assessed using single stool sample, double Kato-Katz smear examinations. Parasitological cure was assessed 3 weeks after treatment. The observed cure rate was 80.9% for the PZQ syrup arm and 81.7% for the crushed PZQ tablet arm, with egg reduction rates of 86.1% and 89.0%, respectively. Pre-treatment infection intensity was observed to influence cure rates significantly, with cure rates of 88.6% for light infections, 74.5% for moderate infections and 67.4% for heavy infections. No significant difference was found in non-compliance between the PZQ syrup (11.1%) and crushed PZQ tablet (14.7%) arms. PZQ syrup and crushed PZQ tablets have very similar efficacies in the treatment of intestinal schistosomiasis in preschool children.

Field survey for strongyloidiasis in eastern Uganda with observations on efficacy of preventive chemotherapy and co-occurrence of soil-transmitted helminthiasis/intestinal schistosomiasis.

Following our previous field surveys for strongyloidiasis in western Uganda, 120 mothers and 232 children from four villages in eastern Uganda were examined, with two subsequent investigative follow-ups. As before, a variety of diagnostic methods were used: Baermann concentration, Koga agar plate and strongyloidid enzyme-linked immunosorbent assay (ELISA), as well as Kato-Katz faecal smears for detection of eggs of other helminths. At baseline, the general prevalence of Strongyloides stercoralis was moderate: 5.4% as estimated by Baermann and Koga agar methods combined. A much higher estimate was found by ELISA (42.3%) which, in this eastern setting, appeared to be confounded by putative cross-reaction(s) with other nematode infections. Preventive chemotherapy using praziquantel and albendazole was offered to all participants at baseline. After 21 days the first follow-up was conducted and 'cure rates' were calculated for all parasites encountered. Eleven months later, the second follow-up assessed longer-term trends. Initial treatments had little, if any, effect on S. stercoralis, and did not alter local prevalence, unlike hookworm infections and intestinal schistosomiasis. We propose that geographical patterns of strongyloidiasis are likely not perturbed by ongoing praziquantel/albendazole campaigns. Antibody titres increased after the first follow-up then regressed towards baseline levels upon second inspection. To better define endemic areas for S. stercoralis, careful interpretation of the ELISA is warranted, especially where diagnosis is likely being confounded by polyparasitism and/or other treatment regimens; new molecular screening tools are clearly needed.

Molecular epidemiology and phylogeography of Schistosoma mansoni around Lake Victoria.

Intestinal schistosomiasis continues to be a major public health problem in sub-Saharan Africa, and is endemic in communities around Lake Victoria. Interest is growing in the molecular evolution and population genetic structure of Schistosoma mansoni and we describe a detailed analysis of the molecular epidemiology and phylogeography of S. mansoni from Lake Victoria. In total, 388 cytochrome oxidase 1 (COI) sequences were obtained from 25 sites along the Ugandan, Tanzanian and Kenyan shorelines of Lake Victoria, and 122 unique barcodes were identified; 9 corresponded to previously discovered barcodes from Lakes Victoria and Albert. A subset of the data, composed of COI sequences from miracidia from 10 individual children, was used for population genetics analyses; these results were corroborated by microsatellite analysis of 4 isolates of lab-passaged adult worms. Overall, 12 barcodes were found to be shared across all 3 countries, whereas the majority occurred singly and were locally restricted. The population genetics analyses were in agreement in revealing high diversity at the level of the human host and negligible population structuring by location. The lack of correlation between genetic distance and geographical distance in these data may be attributed to the confounding influence of high intra-individual diversity as well as human migration between communities.

Transmission studies of intestinal schistosomiasis in Lake Albert, Uganda and experimental compatibility of local Biomphalaria spp.

Despite ongoing preventive chemotherapy campaigns, intestinal schistosomiasis is hyper-endemic in shoreline communities living along Lake Albert, Uganda. To provide a deeper insight into the local epidemiology of Schistosoma mansoni, a variety of field-based studies were undertaken focusing upon schistosome-snail interactions and confirmation of transmission foci. Cercarial shedding patterns of field-caught Biomphalaria spp., as identified by morphology, were hourly observed over a ten day period and showed that Biomphalaria stanleyi produced significantly more cercariae than Biomphalaria sudanica. Peak production times in both species were between 12.00 and 14.00h indicating greatest infection risk from lake water exposure is during the early afternoon. Laboratory-bred snails were exposed to locally hatched miracidia and susceptibility of Biomphalaria spp. was confirmed experimentally. Biomphalaria stanleyi was a more permissive host. After ascertaining appropriate conditions for infection of laboratory mice, 28 groups of between 5 and 6 naïve mice were placed in floatation cages at four suspected shoreline transmission sites for a 30 minute period of exposure. Eight weeks later, mice (n=142) were culled and S. mansoni adult worms were retrieved from 10 animals. Taken as a whole, these observations highlight the local importance of B. stanleyi in transmission of intestinal schistosomiasis and clearly demonstrate the risk of infection on the Lake Albert shoreline. To mitigate this risk local environmental modification(s), i.e. improvement in sanitation and hygiene and control of snail populations, is needed to bolster the impact of chemotherapy-based interventions.

Process evaluation of schistosomiasis control in Uganda, 2003 to 2006: perceptions, attitudes and constraints of a national programme.

Schistosomiasis is widespread in Uganda along large lakes and rivers with approximately 4 million people infected. Hookworm infections also prevalent throughout the country, while infections with Ascaris lumbricoides and Trichuris trichiura are mainly found in south-western Uganda. A national programme aimed at controlling morbidity due to these infections was launched in 2003. This article describes the perceptions, attitudes, constraints and experiences of those implementing the programme and those receiving the treatment. The study used qualitative data collected largely in two districts but also from 18 other districts implementing the programme. Results showed that mass treatment was perceived to be beneficial because the drugs make people feel better. However, side-effects of praziquantel (PZQ), the smell and size of the tablets and the use of height, not weight, to determine dose were raised as major factors discouraging people from taking the drug. Generally, most of the end-users were appreciative of the programme and were beginning to demand regular treatment. Nevertheless, intensive and sustained health education is still vital for improvement of treatment coverage, especially among the non-compliers. It was repeatedly highlighted that there is a need to stock PZQ in all health facilities in endemic areas. Provision of incentives to drug distributors and to involve as many stakeholders as possible in the planning phase were also raised by respondents. Lessons learned for the development and success of a helminth control programme at a national scale are discussed.

The Schistosomiasis Control Initiative (SCI): rationale, development and implementation from 2002-2008.

Schistosomiasis remains one of the most prevalent parasitic diseases in developing countries. After malaria, schistosomiasis is the most important tropical disease in terms of human morbidity with significant economic and public health consequences. Although schistosomiasis has recently attracted increased focus and funding for control, it has been estimated that less than 20% of the funding needed to control the disease in Africa is currently available. In this article the following issues are discussed: the rationale, development and objectives of the Schistosomiasis Control Initiative (SCI)-supported programmes; the management approaches followed to achieve implementation by each country; mapping, monitoring and evaluation activities with quantifiable impact of control programmes; monitoring for any potential drug resistance; and finally exit strategies within each country. The results have demonstrated that morbidity due to schistosomiasis has been reduced by the control programmes. While challenges remain, the case for the control of schistosomiasis has been strengthened by research by SCI teams and the principle that a national programme using 'preventive chemotherapy' can be successfully implemented in sub-Saharan Africa, whenever the resources are available. SCI and partners are now actively striving to raise further funds to expand the coverage of integrated control of neglected tropical diseases (NTDs) in sub-Saharan Africa.

Molecular epidemiology of Schistosoma mansoni in Uganda: DNA barcoding reveals substantial genetic diversity within Lake Albert and Lake Victoria populations.

Representative samples of Ugandan Schistosoma mansoni from Lake Albert and Lake Victoria were examined using DNA barcoding, sequence analysis of two partially overlapping regions - ASMIT (396 bp) & MORGAN (617 bp) - of the mitochondrial cytochrome oxidase subunit I (cox1). The Victorian sample exhibited greater nucleotide diversity, 1.4% vs. 1.0%, and a significant population partition appeared as barcodes did not cross-over between lakes. With one exception, Lake Albert populations were more mixed by sampled location, while those from Lake Victoria appeared more secluded. Using statistical parsimony, barcode ASMIT 1 was putatively ancestral to all others and analysis of MORGAN cox1 confirmed population diversity. All samples fell into two of five well-resolved lineages; sub-lineages therein broadly partitioning by lake. It seems that barcode ASMIT 1 (and close variants) was likely widely dispersed throughout the Nilotic environment but later diversified in situ, and in parallel, within Lake Albert and Lake Victoria. The genetic uniformity of Ugandan S. mansoni can no longer be assumed, which might better explain known epidemiological heterogeneities. While it appears plausible that locally evolved heritable traits could spread through most of the Lake Albert populations, it seems unlikely they could quickly homogenise into Lake Victoria or amongst populations therein.

Rapid mapping of schistosomiasis and other neglected tropical diseases in the context of integrated control programmes in Africa.

There is growing interest and commitment to the control of schistosomiasis and other so-called neglected tropical diseases (NTDs). Resources for control are inevitably limited, necessitating assessment methods that can rapidly and accurately identify and map high-risk communities so that interventions can be targeted in a spatially-explicit and cost-effective manner. Here, we review progress made with (1) mapping schistosomiasis across Africa using available epidemiological data and, more recently, climate-based risk prediction; (2) the development and use of morbidity questionnaires for rapid identification of high-risk communities of urinary schistosomiasis; and (3) innovative sampling-based approaches for intestinal schistosomiasis, using the lot quality assurance sampling technique. Experiences are also presented for the rapid mapping of other NTDs, including onchocerciasis, loiasis and lymphatic filariasis. Future directions for an integrated rapid mapping approach targeting multiple NTDs simultaneously are outlined, including potential challenges in developing an integrated survey tool. The lessons from the mapping of human helminth infections may also be relevant for the rapid mapping of malaria as its control efforts are intensified.

Strongyloides stercoralis: a field-based survey of mothers and their preschool children using ELISA, Baermann and Koga plate methods reveals low endemicity in western Uganda.

To ascertain the current status of strongyloidiasis in mothers and their preschool children, a field-based survey was conducted in western Uganda using a combination of diagnostic methods: ELISA, Baermann concentration and Koga agar plate. The prevalence of other soil-transmitted helminthiasis and intestinal schistosomiasis were also determined. In total, 158 mothers and 143 children were examined from five villages within Kabale, Hoima and Masindi districts. In mothers and children, the general prevalence of strongyloidiasis inferred by ELISA was approximately 4% and approximately 2%, respectively. Using the Baermann concentration method, two parasitologically proven cases were encountered in an unrelated mother and child, both of whom were sero-negative for strongyloidiasis. No infections were detected by Koga agar plate method. The general level of awareness of strongyloidiasis was very poor ( < 5%) in comparison to schistosomiasis (51%) and ascariasis (36%). Strongyloidiasis is presently at insufficient levels to justify inclusion within a community treatment programme targeting maternal and child health. Better epidemiological screening is needed, however, especially identifying infections in HIV-positive women of childbearing age. In the rural clinic setting, further use of the Baermann concentration method would appear to be the most immediate and pragmatic option for disease diagnosis.

Effect of seasonal rainfall and other environmental changes, on snail density and infection rates with Schistosoma mansoni fifteen years after the last snails' study in Kigungu, Entebbe, Uganda.

BACKGROUND: The last study on snail population density in relation to rainfall pattern in Kigungu canoe landing and recreational sites on Lake Victoria shore was earlier carried out about fifteen years ago. This study also reviewed the influence of other environmental factors on the snails' infection rate. OBJECTIVE: To reassess the density dynamic of Biomphalaria (B) choanomphala and Biomphalaria (B) pfeifferi, which act as the intermediate host for S. mansoni and Bulinus (B) globosus, and Bulinus (B) tropicus, which act as intermediate host for S. haematobium. DESIGN: Retrospective study. SETTING: Busy canoe landing sites along Lake Victoria in Kigungu fishing village were selected for the snail sampling. RESULTS: Nine thousand one hundred and ninety four B. choanomphala were collected over the study period. The numbers of B. choanomphala collected in each yearwas 4742 (51.6%) and 4452 (48.4%) in 2004 and 2005 respectively. Of the 4742 B. Choanomphala collected in 2004, 82 (1.7%) shed human cercariae and 329 (6.7%) shed non-human cercariae. Whereas in 2005, out of 4452 B. choanomphala collected 302 (6.85%) shed non-human cercariae and 82 (1.8%) shed human cercariae. Similarly, 4173 B. pfeifferi were also collected in the same period. Out of which 2224 (53.3%) were collected in 2004 and 1949 (46.7%) in 2005. For B. pfeifferi, 42 (1.9%) out of 2224 snails collected in 2004 shed human cercariae and 246 (11.1%) shed non-human cercariae. While in 2005, 33 out of 1949 snails (1.7%) shed human cercariae and 159 (8.2%) shed non-human cercariae. Other snails of medical importance collected included 292 B. globosus and 3094 B. tropicus. None of the Bulinus spp. collected shed any human cercariae but 37 (2.1%) and 30 (2.3%) B. tropicus shed non-human cercariae in 2004 and 2005 respectively. In 2004 and 2005, the area received, 1729mm and 1959mm of rainfall respectively, The mean rainfall during the year was 144.05 mm and 163.3 mm in 2004 and 2005 respectively. There was a negative correlation between rainfalls and snail density dynamic. CONCLUSION: We have found in this study that in spite of the bush clearing of the papyrus swamps which originally was the major habitats for B. choanomphala, B. pfeifferi and the Bulinus spp the intermediate host for schistosome at all canoe landing sites at Kigungu, these snails are still present. Moreover, that their population density dynamic and infection rate are inversely proportional to the rainfall pattern.

Development and application of an ethically and epidemiologically advantageous assay for the multi-locus microsatellite analysis of Schistosoma mansoni.

Non-availability of adult worms from living hosts remains a key problem in population genetic studies of schistosomes. Indirect sampling involving passage through laboratory animals presents significant ethical and practical drawbacks, and may result in sampling biases such as bottlenecking processes and/or host-induced selection pressures. The novel techniques reported here for sampling, storage and multi-locus microsatellite analysis of larval Schistosoma mansoni, allowing genotyping of up to 7 microsatellite loci from a single larva, circumvent these problems. The utility of these assays and the potential problems of laboratory passage, were evaluated using 7 S. mansoni population isolates collected from school-children in the Hoima district of Uganda, by comparing the associated field-collected miracidia with adult worms and miracidia obtained from a single generation in laboratory mice. Analyses of laboratory-passaged material erroneously indicated the presence of geographical structuring in the population, emphasizing the dangers of indirect sampling for population genetic studies. Bottlenecking and/or other sampling effects were demonstrated by reduced variability of adult worms compared to their parent field-collected larval samples. Patterns of heterozygote deficiency were apparent in the field-collected samples, which were not evident in laboratory-derived samples, potentially indicative of heterozygote advantage in establishment within laboratory hosts. Genetic distance between life-cycle stages in the majority of isolates revealed that adult worms and laboratory-passaged miracidia clustered together whilst segregating from field miracidia, thereby further highlighting the utility of this assay.

Schistosoma mansoni in infants (aged < 3 years) along the Ugandan shoreline of Lake Victoria.

In two complementary epidemiological surveys of villages on the Ugandan shoreline of Lake Victoria, the putative occurrence of intestinal schistosomiasis in the local infants (children aged < 3 years) was investigated. When, during the first survey, 136 mother-and-infant pairs from a total of 12 villages were studied, only 7% of the infants but 45% of the mothers were found to be egg-patent for Schistosoma mansoni infection. The use of dipstick tests for urine-circulating cathodic antigen indicated, however, a much higher prevalence, of approximately 40%, among the infants. In the second survey, urine samples and multiple, not single, stool samples were collected from another 19 mother-and-infant pairs in two of the 12 study villages (Bugoto and Bwondha), and a standardized questionnaire was implemented. The prevalence of egg-patent infection was then found to be markedly higher in the study infants from Bugoto (86%) than in those from Bwondha (25%). A greater level of mother-and-infant water contact, a higher abundance of (infected) Biomphalaria choanomphala, and an unusual lakeshore topology may explain why S. mansoni infection was so much more common in the Bugoto subjects than in the Bwondha. All but one of the infants studied in the second survey were found to be anaemic (with <110 g haemoglobin/litre). Taken together, these children were less likely to be found infected with hookworm (16%), Hymenolepis nana (11%) or Trichuris trichiura (5%) than with S. mansoni (47%). Infection with the parasites causing intestinal schistosomiasis can be common among the infants living in these lakeshore villages. Although the immediate and later-life clinical impacts of such infection have yet to be elucidated, such infants would probably benefit from regular de-worming. Mothers should be strongly encouraged to visit the nearest health-services clinic, with their infants, for any necessary anthelmintic treatment.

Modeling freshwater snail habitat suitability and areas of potential snail-borne disease transmission in Uganda.

Geographic information system (GIS-based modeling of an intermediate host snail species environmental requirements using known occurrence records can provide estimates of its spatial distribution. When other data are lacking, this can be used as a rough spatial prediction of potential snail-borne disease transmission areas. Furthermore, knowledge of abiotic factors affecting intra-molluscan parasitic development can be used to make "masks" based on remotely sensed climatic data, and these can in turn be used to refine these predictions. We used data from a recent freshwater snail survey from Uganda, environmental data and the genetic algorithm for rule-set prediction (GARP) to map the potential distribution of snail species known to act as intermediate hosts of several human and animal parasites. The results suggest that large areas of Uganda are suitable habitats for many of these snail species, indicating a large potential for disease transmission. The lack of parasitological data still makes it difficult to determine the magnitude of actual disease transmission, but the predicted snail distributions might be used as indicators of potential present and future risk areas. Some of the predicted snail distribution maps were furthermore combined with temperature masks delineating suitable temperature regimes of the parasites they host. This revealed the coinciding suitable areas for snail and parasite, but also areas suitable for host snails, but apparently not for the parasites. Assuming that the developed models correctly reflect areas suitable for transmission, the applied approach could prove useful for targeting control interventions.

Soil-transmitted helminthiasis in Uganda: epidemiology and cost of control.

A country-wide description of the distribution of soil-transmitted helminths in Uganda is reported, based on data for 20-185 school-children from 271 schools. The overall prevalence of Ascaris lumbricoides, Trichuris trichiura and hookworm was 6.3%, 5.0% and 43.5%, respectively. The prevalence of A. lumbricoides and T. trichiura was unevenly distributed in the country with prevalence greatest in south-western Uganda whereas hookworm was generally more homogeneously distributed. Based on preliminary cost analysis of an ongoing school-based control programme, the financial delivery cost per school-child treated with albendazole is estimated to be between US dollar 0.04 and 0.08 in different districts.