Dataset Information

Effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable areas of a state in northeastern Brazil, 2011-2014.

ABSTRACT:

Background

To assess the effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable endemic areas in northeastern Brazil.

Method

An ecological study was conducted, in which 118 localities in 30 municipalities in the state of Pernambuco were screened before 2011 and in 2014 (after mass treatment). Information on the endemic baseline index, mass treatment coverage, socio-environmental conditions and social vulnerability index were used in the multiple correspondence analysis. One hundred fourteen thousand nine hundred eighty-seven people in 118 locations were examined.

Results

The first two dimensions of the multiple correspondence analysis represented 55.3% of the variability between locations. The human capital component of the social vulnerability index showed an association with the baseline endemicity index. There was a significant reduction in positivity for schistosomes. For two rounds, for every extra 1% of initial endemicity index, the fixed effect of 13.62% increased by 0.0003%, achieving at most 15.94%.

Conclusions

The mass treatment intervention helped to reduce transmission of schistosomiasis in areas of high endemicity. Thus, it can be recommended that application of mass treatment should be accompanied by other control actions, such as basic sanitation, monitoring of intermediate vectors and case surveillance.

SUBMITTER: Wanderley FSO

PROVIDER: S-EPMC7941929 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Publications

Effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable areas of a state in northeastern Brazil, 2011-2014.

Wanderley Flávia Silvestre Outtes FSO Montarroyos Ulisses U Bonfim Cristine C Cunha-Correia Carolina C

Archives of public health = Archives belges de sante publique 20210309 1

<h4>Background</h4>To assess the effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable endemic areas in northeastern Brazil.<h4>Method</h4>An ecological study was conducted, in which 118 localities in 30 municipalities in the state of Pernambuco were screened before 2011 and in 2014 (after mass treatment). Information on the endemic baseline index, mass treatment coverage, socio-environmental conditions and social vulnerability index were used in the multiple co ...[more]

PMID: 33750474

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Project description:Schistosomiasis, which is caused by trematodes of the genus Schistosoma and by the species Schistosoma mansoni in Brazil, is transmitted primarily by Biomphalaria glabrata mollusks. Infections occur in humans and mollusks in freshwater environments contaminated with feces from infected humans. This study aimed to evaluate potential foci of schistosomiasis based on the identification of infection sites for the snails, factors that increased the human infection probability of S. mansoni infection, and the relationship of the disease with abiotic, biotic, and sociocultural factors. The study was conducted in an urban area on the northeast coast of Brazil; this location was chosen based on the following factors: the presence of B. glabrata, nearby freshwater, and the absence of sewer treatment. A parasitological analysis was performed to evaluate infections of the mollusks and residents inside the perimeter defined by the collection points. Questionnaires were applied to obtain demographic data and to identify behaviors that led to human infection. To verify the contamination of freshwater by human feces, a microbiological analysis of the water was performed at the mollusk collection points to determine the rate of contamination with fecal coliforms. A total of 10,270 B. glabrata mollusks were collected between August 2013 and August 2014, of which 8.8% were positive for S. mansoni; the prevalence ranged from 0 to 34.5% over the study period. A total of 232 coprological samples from the residents were analyzed. The S. mansoni infection prevalence rate was 16.4%, and the S. mansoni parasitic load in the infected residents was 54.9 eggs per gram of feces on average. Males were more affected by the parasite, especially in the 8-17-year-old age range. Thermotolerant coliforms were observed at the mollusk collection sites, which indicated that freshwater and sewage were in continuous contact. This contamination indicated poor sanitary conditions, as was previously observed, which could be combined with detrimental behavior due to the residents' habits. These conditions cause a predisposition for both intermediate and definitive infections of the hosts by creating a socioenvironmental scenario that is conducive to the formation and maintenance of potential schistosomiasis foci. This and similar areas deserve special attention from the government with an aim of improving sanitation services and local resident knowledge to prevent future contamination.

Project description:BackgroundThe Kato-Katz (KK) stool smear is the standard test for the diagnosis of Schistosoma mansoni infection, but suffers from low sensitivity when infections intensities are moderate to low. Thus, misdiagnosed individuals remain untreated and contribute to the disease transmission, thereby forestalling public health efforts to move from a modality of disease control to one of elimination. As an alternative, the urine-based diagnosis of schistosomiasis mansoni via the circulating cathodic antigen immuno-chromatographic test (CCA-ICT) has been extensively evaluated in Africa with the conclusion that it may replace the KK test in areas where prevalences are moderate or high.Methods and findingsThe objective was to measure the performance of the CCA-ICT in a sample study population composed of residents from non-endemic and endemic areas for schistosomiasis mansoni in two municipalities of Minas Gerais state, Brazil. Volunteers (130) were classified into three infection status groups based on duplicate Kato-Katz thick smears from one stool sample (2KK test): 41 negative individuals from non-endemic areas, 41 negative individuals from endemic areas and 48 infected individuals from endemic areas. Infection status was also determined by the CCA-ICT and infection exposure by antibody ELISA (enzyme-linked immunosorbent assay) to S. mansoni soluble egg antigen (SEA) and soluble (adult) worm antigen preparation (SWAP). Sensitivity and specificity were influenced by whether the trace score visually adjudicated in the CCA-ICT was characterized as positive or negative for S. mansoni infection. An analysis of a two-graph receiver operating characteristic was performed to change the cutoff point. When the trace score was interpreted as a positive rather than as a negative result, the specificity decreased from 97.6% to 78.0% whereas sensitivity increased from 68.7% to 85.4%. A significantly positive correlation between the CCA-ICT scores and egg counts was identified (r = 0.6252, p = 0.0001). However, the CCA-ICT misdiagnosed as negative 14.6% of 2KK positive individuals, predominantly those with light infections (fewer than 100 eggs/g feces). Considering 2KK as reference test, the discriminating power of the CCA-ICT (the area under the curve [AUC] = 0.817) was greater than the SEA-ELISA (AUC = 0.744) and SWAP-ELISA (AUC = 0.704).ConclusionOur data for the performance of the CCA-ICT in the Brazilian communities endemic for schistosomiasis mansoni support those from Africa, i.e., in areas with greater infection prevalence and intensities, the CCA-ICT may be useful as a tool to indicate community-based preventative chemotherapy without individual diagnosis. However, because of the Brazilian Ministry of Health's recommendation for individual diagnosis in areas where prevalence is less than 15%, i.e., those areas in which infection intensities are likely to be lowest, the CCA-ICT lacks the sensitivity to be used as standalone diagnostic tool.

Project description:BackgroundSchistosoma mansoni, causing intestinal schistosomiasis, is widely distributed in Ethiopia and new transmission foci are continually reported. Here we report new transmission sites and prevalence of S.mansoni infection among school children in Yachi areas, southwestern Ethiopia.MethodsA cross-sectional survey was conducted among school children of Yachi Yisa and Yachi Efo elementary schools, southwestern Ethiopia, from April 2017 to June 2017. Three hundred seventeen school children aged six to 15 years were randomly selected to provide stool specimens for helminth infection examination by Kato-Katz and formol-ether concentration techniques. Snail survey was carried out to assess schistosome infection in Biomphalaria pfeifferi. Laboratory bred mice were also exposed to schistosome cercariae shed by B. pfeifferi en masse for definite identification of Schistosoma species.ResultsFrom the 317 stool specimens examined using double Kato-Katz thick smear and single formol-ether concentration techniques, 224 (70.7%) were found positive for at least one intestinal helminth species. The most prevalent parasite was S. mansoni (42.9%) followed by Trichuris trichiura (34.1%) and Ascaris lumbricoides (14.2%). The prevalence of S. mansoni infection was significantly higher among the children attending Yachi Yisa School (49.4%) than those in Yachi Efo School (35.6%) (P = 0.002). The study also revealed that there was a significantly higher prevalence of S.mansoni infection among males (51.2%) than females (33.1%) (P < 0.001). However, the prevalence of S.mansoni infection was not significantly associated with age categories (P = 0.839). B. pfeifferi snails infected with schistosomes were collected from the water bodies found in the study area. After six weeks post exposure, adult S. mansoni worms were harvested from the mesenteric veins of laboratory bred mice.ConclusionsThe study revealed establishment of new S. mansoni transmission foci and moderate prevalence of schistosomiasis in Yachi areas. Hence, treatment of all school-age children once every two years is recommended. Snail control and non-specific control approaches including provision of clean water supply and health education should also complement mass drug administration of praziquantel.

Project description:BackgroundSchistosomiasis a neglected tropical disease endemic in Brazil. It is caused by the trematode Schistosoma mansoni, which is transmitted by snails of the genus Biomphalaria. Among measures used to control and eliminate schistosomiasis, accurate mapping and monitoring of snail breeding sites are recommended. Despite the limitations of parasitological methods, they are still used to identify infected snails. Loop-mediated isothermal amplification (LAMP) is a sensitive, rapid, and cost-effective diagnostic method for the identification of infected snails. In the work reported here, we aimed to validate the use of LAMP for the detection of S. mansoni in snails of the genus Biomphalaria.MethodsSnails were collected in five municipalities of the Mucuri Valley and Jequitinhonha Valley regions in the state of Minas Gerais, Brazil. Snails were pooled according to collection site and then squeezed for the detection of S. mansoni and other trematode larvae. Pooled snails were subjected to pepsin digestion and DNA extraction. Molecular assays were performed for species-specific identification and characterization of the samples. A previously described LAMP assay was adapted, evaluated, and validated using laboratory and field samples.ResultsUsing the parasitological method described here, S. mansoni cercariae were detected in snails from two collection sites, and cercariae of the family Spirorchiidae were found in snails from one site. The snails were identified by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Biomphalaria glabrata, the main snail host of S. mansoni in Brazil, was detected in 72.2% of the collection sites. Biomphalaria kuhniana, which is resistant to S. mansoni infection, was found in the remaining sites. Multiplex, low stringency (LS), and conventional PCR allowed the detection of positive snails in four additional sites. Trematodes belonging to the families Strigeidae and Echinostomatidae were detected by multiplex PCR in two sites. The LAMP assay was effective in detecting the presence of S. mansoni infection in laboratory (7 days post-infection) and field samples with no cross-reactivity for other trematodes. When compared to LS and conventional PCR, LAMP showed 100% specificity, 85.7% sensitivity, and a κ index of 0.88.ConclusionsOur findings suggest that LAMP is a good alternative method for the detection and monitoring of transmission foci of S. mansoni, as it was three times as effective as the parasitological examination used here for the detection of infection, and is more directly applicable in the field than other molecular techniques.

Dataset Information

Effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable areas of a state in northeastern Brazil, 2011-2014.

Background

Method

Results

Conclusions

Publications

Effectiveness of mass treatment of Schistosoma mansoni infection in socially vulnerable areas of a state in northeastern Brazil, 2011-2014.

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