Deep learning for AI-based diagnosis of skin-related neglected tropical diseases: A pilot study

BACKGROUND

Deep learning, which is a part of a broader concept of artificial intelligence (AI) and/or machine learning has achieved remarkable success in vision tasks. While there is growing interest in the use of this technology in diagnostic support for skin-related neglected tropical diseases (skin NTDs), there have been limited studies in this area and fewer focused on dark skin. In this study, we aimed to develop deep learning based AI models with clinical images we collected for five skin NTDs, namely, Buruli ulcer, leprosy, mycetoma, scabies, and yaws, to understand how diagnostic accuracy can or cannot be improved using different models and training patterns.

METHODOLOGY

This study used photographs collected prospectively in Côte d'Ivoire and Ghana through our ongoing studies with use of digital health tools for clinical data documentation and for teledermatology. Our dataset included a total of 1,709 images from 506 patients. Two convolutional neural networks, ResNet-50 and VGG-16 models were adopted to examine the performance of different deep learning architectures and validate their feasibility in diagnosis of the targeted skin NTDs.

PRINCIPAL FINDINGS

The two models were able to correctly predict over 70% of the diagnoses, and there was a consistent performance improvement with more training samples. The ResNet-50 model performed better than the VGG-16 model. A model trained with PCR confirmed cases of Buruli ulcer yielded 1-3% increase in prediction accuracy across all diseases, except, for mycetoma, over a model which training sets included unconfirmed cases.

CONCLUSIONS

Our approach was to have the deep learning model distinguish between multiple pathologies simultaneously-which is close to real-world practice. The more images used for training, the more accurate the diagnosis became. The percentages of correct diagnosis increased with PCR-positive cases of Buruli ulcer. This demonstrated that it may be better to input images from the more accurately diagnosed cases in the training models also for achieving better accuracy in the generated AI models. However, the increase was marginal which may be an indication that the accuracy of clinical diagnosis alone is reliable to an extent for Buruli ulcer. Diagnostic tests also have their flaws, and they are not always reliable. One hope for AI is that it will objectively resolve this gap between diagnostic tests and clinical diagnoses with the addition of another tool. While there are still challenges to be overcome, there is a potential for AI to address the unmet needs where access to medical care is limited, like for those affected by skin NTDs.

Buruli ulcer: application of thermography for remote diagnosis of a neglected tropical disease

We here report a proof of concept of using thermography for teledermatology practice for skin of colour using an example of an early case of Buruli ulcer – a neglected tropical disease that mainly affects people living in remote communities of Africa. In the presented case, the full extent of the lesion and lymphangitis were further and more precisely detected by thermography than even with the naked eye. Redness, an important sign of inflammation, can be masked in individuals with skin of colour. If thermal images can be transmitted to remote dermatologists in addition to regular photographs in the practice of teledermatology, this may improve diagnostic and prognostic accuracy, especially for this neglected population.

An mHealth App (eSkinHealth) for Detecting and Managing Skin Diseases in Resource-Limited Settings: Mixed Methods Pilot Study

BACKGROUND

In sub-Saharan Africa, the disease burden from skin diseases, including skin-related neglected tropical diseases (skin NTDs), is extremely high. These diseases often are overlooked due to limited access to health care stemming from, for example, remote geographical locations and a lack of experts. To address these gaps, we developed a mobile health app, eSkinHealth, which is a field-adapted platform to serve as a portable electronic patient chart and for teledermatology.

OBJECTIVE

The purpose of the study is to evaluate the usability and effectiveness of the app in rural Côte d'Ivoire for diagnosing and managing skin NTDs and other skin diseases.

METHODS

A 2-arm trial with local health care providers and patients with skin diseases was implemented over a 3-month period. The providers were assigned to an intervention receiving the eSkinHealth app or control with usual care. Four nurses and 8 community health care workers participated in each arm. The training was provided on the use of the app to the intervention arm only, while both arms were trained on skin diseases. For the usability study, we evaluated our approach with the System Usability Scale (SUS) and in-depth interviews. For the effectiveness study, our primary outcome was to evaluate the detection and management of 5 skin NTDs as our targeted diseases, namely, Buruli ulcer, leprosy, lymphatic filariasis, scabies, and yaws, using the eSkinHealth app. Procedures of our methods were reviewed and approved by the institutional review board of the Ministry of Health and by Tulane University.

RESULTS

The mean age of our participants (providers) was 40.5 and 42.5 years for the intervention and control arms, respectively, and all were male (n=24). The average SUS scores taken from the intervention arm at baseline, the midpoint (6 weeks), and the end of study (12 weeks) were 72.3 (SD 11.5), 72.3 (SD 12.4), and 86.3 (SD 10.8), respectively. All participants interviewed, including 4 dermatologists and program managers, were satisfied with the app. Especially community health care workers felt empowered by being equipped with the tool. A total of 79 cases of skin NTDs were reported in the intervention arm as compared to 17 cases in the control arm (P=.002). Besides the skin NTDs, more skin diseases and conditions were reported from the control than from the intervention arm (P<.001). However, 100 cases (66%) were not given any particular diagnosis in the control arm and were documented only as a "dermatosis." In the intervention arm, 151 cases (72.9%) were diagnosed within the eSkinHealth platform, and the remaining were diagnosed on-site by dermatologists.

CONCLUSIONS

The study provided evidence for the usability and effectiveness of the eSkinHealth app embedded into our surveillance approach to improve the detection and management of skin NTDs and other skin diseases in Côte d'Ivoire and, furthermore, is expected to contribute to knowledge on mobile health approaches in the control of skin diseases in resource-limited settings.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05300399; https://clinicaltrials.gov/ct2/show/NCT05300399.

Evidence for local transmission and maintenance of schistosomiasis in an urban neighbourhood in Northeast Brazil

Schistosomiasis is a tropical neglected disease commonly associated with rural areas; however, urban schistosomiasis has been reported worldwide, and increasing urbanization is one of the most important demographic shifts of the 20th and now 21st centuries. The pattern of urbanization is not uniform so that within the same city the rates and sources of population increase vary. Here, we report on the parasite composition in one neighbourhood in the metropolitan area of Salvador, Bahia, Brazil. Using epidemiological data and population genetics, we find evidence for local transmission and maintenance of Schistosoma mansoni infection within an urban population and little contribution from rural-urban migration. Our findings provide direction for local mitigation strategies and to assist the public living in this neighbourhood to interrupt the local transmission cycle.

Early Detection and Case Management of Skin Diseases with a Mobile Health Application 'eSkinHealth': Protocol for a Mixed-Methods Pilot Study in Côte d'Ivoire

BACKGROUND

The prevalence of skin diseases is extremely high in sub-Saharan Africa, among which are skin neglected tropical diseases (skin NTDs) that could lead to life-long disabilities and deformities if not diagnosed and treated early. To achieve early detection and early treatment of these skin diseases, we developed a mobile health application (mHealth app): 'eSkinHealth.'

OBJECTIVE

This paper outlines a protocol for evaluating the effect of our eSkinHealth app in the early detection and effective management of skin diseases in Côte d'Ivoire.

METHODS

A mixed-methods pilot trial will be conducted in Côte d'Ivoire and will consist of 3 phases: phase 1, the development and improvement of the eSkinHealth app; phase 2, a pilot trial to evaluate the usability of the eSkinHealth app for local medical staff in Côte d'Ivoire; and phase 3, a pilot trial to evaluate the effectiveness of early detection and case management of targeted skin NTDs (Buruli ulcer, leprosy, yaws, and lymphatic filariasis) with the eSkinHealth app in Côte d'Ivoire. The pilot study will be implemented as a 2-arm trial with local healthcare providers and patients with skin NTDs over a 3-month follow-up period. The local healthcare providers will be assigned to an intervention group receiving the eSkinHealth app to be used in their daily practices or a control group. Training will be provided on the usage and implementation of the app and diagnostic pipeline to the intervention group only, while both groups will receive training on skin diseases. Our primary outcome is to evaluate the early detection and effective management of skin diseases using the eSkinHealth app in Côte d'Ivoire by number of cases diagnosed and managed. Additionally, we will evaluate the eSkinHealth app with validated questionnaires and in-depth interviews. Procedures of our methods have been reviewed and approved by the IRB of the Ministry of Health, Côte d'Ivoire and by Tulane University in 2021.

RESULTS

This study was funded in 2021. We started enrolment of patients in February 2022, and data collection is currently underway. We expect the first results to be submitted for publication in 2023.

CONCLUSIONS

Our 'eSkinHealth' is a field-adapted platform that could both provide direct diagnostic and management assistance to health workers in remote settings. The study will provide evidence for the usability and the effectiveness of the eSkinHealth app to improve the early detection and case management of skin NTDs in Côte d'Ivoire; and further, are expected to contribute to knowledge on mobile health approaches in the control of skin NTDs.

CLINICALTRIAL

2020-2054 (Clinicaltrials.gov).

Cryptic population structure and transmission dynamics uncovered for Schistosoma mansoni populations by genetic analyses

Patterns of diversity in pathogen genomes provide a window into the spatiotemporal spread of disease. In this study, we tested the hypothesis that Schistosoma mansoni parasites form genetic clusters that coincide with the communities of their human hosts. We also looked for genetic clustering of parasites at the sub-community level. Our data consists of 14 microsatellite DNA markers, typed from pooled DNA samples from [Formula: see text] infected individuals living in three Brazilian communities. We found a one-to-one correspondence between genetic clusters found by K-means cluster analysis and communities when [Formula: see text]. These clusters are also easily identified in a neighbor-joining tree and principal coordinates plots. K-means analysis with [Formula: see text] also reveals genetic clusters of parasites at the sub-community level. These sub-clusters also appear on the neighbor-joining tree and principal coordinates plots. A surprising finding is a genetic relationship between subgroups in widely separated human communities. This connection suggests the existence of common transmission sites that have wide influence. In summary, the genetic structure of S. mansoni in Brazil juxtaposes local isolation that is occasionally broken by long-range migration. Permanent eradication of schistosomes will require both local efforts and the identification of regional infection reservoirs.

A Schistosoma mansoni tri- and tetramer microsatellite catalog for genetic population diversity and differentiation

All Schistosoma mansoni tri- and tetranucleotide repeat microsatellites published as of December 2018 were identified. All 52 were evaluated for autosomal location, strength of amplification, scorability and behavior as single-copy loci by polyacrylamide and capillary gel electrophoresis. Of these, 27 were unique, autosomal, polymorphic, easily scored and single copy as assessed on pooled adult worm DNA from two different continental origins and adult worm clones. These microsatellites were distributed across all seven autosomal chromosomes. On laboratory strains their heterozygosity ranged from 0.22 to 0.77. Individual markers had 5-13 alleles, allelic richness of 2-10 and an effective allele number of 1.3-8.14. Those infected by Schistosoma mansoni carry many genetically distinct, sexually reproducing parasites, therefore, for an individual infection the complete allele frequency profile of their progeny consists of a pool of DNA from multiple diploid eggs. Using a set of 25 microsatellites, we calculated allele frequency profiles of eggs in fecal samples from people in two Brazilian communities separated by 6 km: Jenipapo (n = 80) and Volta do Rio (n = 38). There were no a priori characteristics that could predict the performance of markers in natural infections based on their performance with laboratory strains. Increasing marker number did not change accuracy for differentiation and diversity but did improve precision. Our data suggest that using a random set of 10-20 microsatellites appears to result in values that exhibit low standard deviations for diversity and differentiation indices. All identified microsatellites as well as PCR conditions, allele size, primer sequences and references for all tri- and tetramer microsatellites markers presented in this work are available at: https://sites.google.com/case.edu/cwru-and-fiocruz-wdrc/home.

Microbial source tracking and antimicrobial resistance in one river system of a rural community in Bahia, Brazil

Use of antibiotics inevitably leads to antimicrobial resistance. Selection for resistance occurs primarily within the gut of humans and animals as well as in the environment through natural resistance and residual antibiotics in streams and soil. We evaluated antimicrobial resistance in Gram negative bacteria from a river system in a rural community in Bahia, Brazil. Water was collected from the Jiquiriçá and Brejões rivers and the piped water supply. Additionally, stools were collected from a random sample of residents, cows, pigs and horses near the river. The samples were screened for bacteria resistant to ciprofloxacin, cefotaxime, and meropenem and identified biochemically at the genus and species levels. Microbial source tracking demonstrated that ruminant and human fecal contamination increased as the rivers neared the village center and decreased after the last residence. Antibiotic bacteria were identified from all samples (n = 32). No bacteria were resistant to carbapenems, but the majority of the enterobacteria were resistant to ciprofloxacin, even though this class of antibiotics is not commonly used in food animals in this region. Considering these facts, together with the pattern of human fecal contamination, a human source was considered most likely for these resistant isolates.

The changing profile of schistosomiasis in a changing urban landscape

Since 2007, most of humanity resides in urban areas, a trend which continues worldwide. Diseases usually associated with rural contexts are now emerging or newly recognised in cities. In the neighbourhood of São Bartolomeu in Salvador, Brazil, the prevalence of Schistosoma mansoni infection in 2011 was >20%. Following enrollment and treatment of a portion of the community, ~25% of the area underwent urban renewal. In 2015, we returned to enrol individuals who had previously participated and a cohort that had not taken part in 2011. Thus, infected individuals in one group experienced specific drug treatment plus improved living conditions and the second group only improved living conditions. Between 2011 and 2015 there were no organised treatment programs, but adequate sanitation increased from 69% to 92% coverage, household flooding decreased, and the presence of indoor toilets increased to 99% of households. Ownership of household appliances also increased significantly. The overall prevalence of schistosome infections was 6.2%. In 2015, the cohort first seen in 2011 had a higher prevalence (8.7%) than those first seen in 2015 (4.8%) and showed a few demographic differences. The 2011 cohort was older, more likely born in Salvador, less likely to have lived outside of Salvador, spent a greater percentage of their lifetime in Salvador, but more likely to have travelled. The population structure of the parasites from both cohorts underwent a marked change with similar increased component and infrapopulation differentiation and >10 fold decrease in effective population size. There was a 4-5 year shift in age-specific prevalence in 2015 for all compared with 2011. While praziquantel may have helped reduce prevalence, our evidence suggests that the structural changes and improvements in living conditions had the biggest impact on schistosomiasis in this community.

Antibiotic Resistance in Enterobacteriaceae from Surface Waters in Urban Brazil Highlights the Risks of Poor Sanitation

Surface waters are an unappreciated reservoir of antimicrobial resistance (AMR). Poor sanitation brings different species of environmental bacteria into contact, facilitating horizontal gene transfer. To investigate the role of surface waters as potential reservoirs of AMR, we studied the point prevalence of fecal contamination, AMR genes, and Enterobacteriaceae in an urban lake and rural river system in Northeast Brazil in comparison with a lake and sewer system in Northeast Ohio in the United States. Surface water samples were examined for evidence of human fecal contamination using microbial source tracking and screened for plasmid-mediated fluoroquinolone resistance and carbapenemase genes. Enterobacteriaceae were detected using selective agar followed by antimicrobial susceptibility testing and detection of AMR genes by microarray, and classified by repetitive sequence-based polymerase chain reaction and multilocus sequence typing. Concentrations of human fecal bacteria in the Brazilian urban lake and sewage in Northeast Ohio were similarly high. Filtered water samples from the Brazilian urban lake, however, showed the presence of bla OXA-48, bla KPC, bla VIM-2, qnrS, and aac(6')-lb-cr, whereas only bla VIM-2 was identified in raw sewage from Northeast Ohio. From the Brazilian urban lake, 85% of the Enterobacteriaceae (n = 40) cultured were resistant to at least one clinically important antibiotic, including ST131 Escherichia coli harboring the extended-spectrum beta-lactamase CTX-M. Although two isolates demonstrated polymyxin resistance, mcr-1/2 was not detected. Our findings indicate that surface waters in an urban Brazilian site can serve as an environmental reservoir of AMR and that improving wastewater treatment and sanitation generally may ameliorate AMR dissemination.

The effect of sample size on estimates of genetic differentiation and effective population size for Schistosoma mansoni populations

Eradication or local extinction of the human parasite Schistosoma mansoni is a goal for many control programs. Population genetic analyses are helping to evaluate and guide these efforts, yet what to sample, how to sample and how densely to sample is not well established. We determined the S. mansoni allele frequency profile of nearly all infected inhabitants in two small Brazilian communities and created sub-samples representing 5-50% of all detected human infections (infrapopulations). Samples were selected at random with replacement, and each size class was replicated 100 times. Mean pairwise differentiation for all infrapopulations (Di) and the variance effective population size (Ne) were calculated for each sample. Prior to community-wide treatment, the true mean Di was moderate (0.095-0.123) and Ne large (>30,000). Most samples of <50% of those infected produced estimates outside of 5% of the true value. For estimates within 10%, sample sizes of >15% of all infrapopulations were required. At the 3 year follow-up after treatment, the Di increased and Ne was reduced by >15 fold. At this time sampling of >30-45% was needed to achieve the same accuracy. Following a second treatment and 4 years from baseline, the Di further increased and Ne decreased with little change in the sampling effort required. Extensive sampling is required for accurate estimates of these important population parameters. Characteristics such as population census size, infection prevalence, the community's treatment history and the degree of infrapopulation differentiation should be taken into account. The intensity of infection was weakly correlated with the ability of a single infrapopulation to represent the component population (Dic), indicating a tendency toward random acquisition of parasite genotypes. This also suggests that targeted sampling from those most heavily infected will better represent the genetic diversity of the whole community than a random sample of infrapopulations.

Population Genetics and Molecular Epidemiology of Eukaryotes

Molecular epidemiology uses the distribution and organization of a pathogen's DNA to understand the distribution and determinants of disease. Since the biology of DNA for eukaryotic pathogens differs substantially from that of bacteria, the analytic approach to their molecular epidemiology can also differ. While many of the genotyping techniques presented earlier in this series, "Advances in Molecular Epidemiology of Infectious Diseases," can be applied to eukaryotes, the output must be interpreted in the light of how DNA is distributed from one generation to the next. In some cases, parasite populations can be evaluated in ways reminiscent of bacteria. They differ, however, when analyzed as sexually reproducing organisms, where all individuals are unique but the genetic composition of the population does not change unless a limited set of events occurs. It is these events (migration, mutation, nonrandom mating, selection, and genetic drift) that are of interest. At a given time, not all of them are likely to be equally important, so the list can easily be narrowed down to understand the driving forces behind the population as it is now and even what it will look like in the future. The main population characteristics measured to assess these events are differentiation and diversity, interpreted in the light of what is known about the population from observation. The population genetics of eukaryotes is important for planning and evaluation of control measures, surveillance, outbreak investigation, and monitoring of the development and spread of drug resistance. *This article is part of a curated collection.

Food Consumption as a Modifier of the Association between LEPR Gene Variants and Excess Body Weight in Children and Adolescents: A Study of the SCAALA Cohort

No studies showing that food consumption is a modifier of the association of variants of the leptin receptor gene (LEPR) with body weight have involved a Brazilian population. The aim of this study was to evaluate the modifying effect of dietary intake on the association between the LEPR gene and excess weight. In this study, 1211 children and adolescents aged 4⁻11 years were assessed. Participants were genotyped for 112 single-nucleotide variants of the LEPR gene. Anthropometric measurements were performed, and dietary data were obtained. Logistic regressions were used to study the associations of interest. Of the participants, 13.4% were overweight/obese. The risk allele (G) of the rs1137100 variant was associated with excess weight in individuals with fat consumption below the median (odds ratio OR = 1.92; 95% confidence interval CI = 1.18⁻3.14), with daily frequency of consumption of drink/artificial juice (OR = 2.15; 95% CI = 1.26⁻3.68) and refined cereals (OR = 2.17; 95% CI = 1.31⁻3.62) above the median. The risk allele (G) of variant rs1177681 was also associated with excess weight (OR = 2.74; 95% CI = 1.65⁻4.57) in subjects with a daily frequency of refined cereal consumption above the median. The association between LEPR and excess weight can be modulated by the type and distribution of dietary fatty acids, sugary drinks, and refined cereals.

Evaluating public housing residents for knowledge, attitudes, and practices following dengue prevention outreach in Key West, Florida

BACKGROUND

In 2009-2010, 93 cases of dengue were identified in Key West, Florida. This was the first outbreak of autochthonous transmission of dengue in Florida since 1934. In response to this outbreak, a multifaceted public education outreach campaign was launched. The aim of this study is to compare dengue prevention knowledge, attitudes, perceptions, and prevention practices among residents of subsidized public housing to the general population in Key West and to assess whether there were barriers preventing effective outreach from reaching specific vulnerable populations.

METHODS

A randomized population-based evaluation of knowledge, attitudes, and behaviors toward dengue prevention consisting of 521 separate household interviews was undertaken in July of 2011. A subset analysis was performed on interviews collected from 28 public housing units within four subsidized public housing complexes. Analysis was performed to determine whether knowledge, attitudes, and behaviors exhibited by public housing residents differed from the non-public housing study population.

RESULTS

Public housing residents recalled fewer outreach materials (p=0.01) and were 3.4 times (95% confidence interval [CI] 1.4-8.3) more likely not to recall any outreach materials. Public housing residents were less likely to correctly identify how dengue transmission occurs (61% vs. 89%), where mosquitoes lay their eggs (54% vs. 85%), or to identify any signs or symptoms related to dengue (36% vs. 64%). Public housing residents were less likely to perform dengue prevention practices such as removing standing water or always using air conditioning.

CONCLUSIONS

Examination of public housing residents identified an at-risk population that recalled less exposure to outreach materials and had less knowledge about dengue infection and prevention than the randomized study population. This provides public health systems the opportunity to target or modify future health messages and interventions to this group. Differences identified in the demographics of this population suggest that alternative methods or non-English materials may be required to reach desired outcomes.

Repeated praziquantel treatments remodel the genetic and spatial landscape of schistosomiasis risk and transmission

Repeated treatments with praziquantel reduce schistosomiasis prevalence and morbidity, but transmission persists and populations often recover within a few years. To identify factors associated with persistence, we surveyed and treated all identified Schistosoma mansoni infections in two rural Brazilian communities (Jenipapo and Volta do Rio) in 2009, 2012 and 2013. Eggs were collected from all infected individuals and genotyped with 11 microsatellite markers to evaluate parasite differentiation and diversity. After successive rounds of community-wide treatment, prevalence decreased from 45% to 24% then 16%. Intensity of infection decreased by 57% over this period, and the number of eggs transmitted to the environment decreased by 92%. During all time periods the majority of eggs were excreted by those >15years of age. The incidence was 23% in 2012 and 15% in 2013, consistent with a decrease in transmission. There was little immigration or gene flow over a distance of 6km. On reinfection, infrapopulations were moderately differentiated indicating that pretreatment multilocus genotypes were not fully reacquired. The effective population size responded to census population decline more rapidly than differentiation. Reinfection was concentrated in the downstream portion of Jenipapo, consistent with the observed increased human fecal contamination. At this scale and in this area S. mansoni infections exist on a fragmented landscape with a highly focal pattern of transmission that may facilitate future elimination.

The relative contribution of immigration or local increase for persistence of urban schistosomiasis in Salvador, Bahia, Brazil

Urbanization is increasing across the globe, and diseases once considered rural can now be found in urban areas due to the migration of populations from rural endemic areas, local transmission within the city, or a combination of factors. We investigated the epidemiologic characteristics of urban immigrants and natives living in a neighborhood of Salvador, Brazil where there is a focus of transmission of Schistosoma mansoni. In a cross-sectional study, all inhabitants from 3 sections of the community were interviewed and examined. In order to determine the degree of parasite differentiation between immigrants and the native born, S. mansoni eggs from stools were genotyped for 15 microsatellite markers. The area received migrants from all over the state, but most infected children had never been outside of the city, and infected snails were present at water contact sites. Other epidemiologic features suggested immigration contributed little to the presence of infection. The intensity and prevalence of infection were the same for immigrants and natives when adjusted for age, and length of immigrant residence in the community was positively associated with prevalence of infection. The population structure of the parasites also supported that the contribution from immigration was small, since the host-to-host differentiation was no greater in the urban parasite population than a rural population with little distant immigration, and there had been little differentiation in the urban population over the past 7 years. Public health efforts should focus on eliminating local transmission, and once eliminated, reintroduction from distant migration is unlikely.

Urban transmission of schistosomiasis is becoming more recognized as rural disease is becoming less common and urbanization increases. Characteristics of infection of the immigrant population to cities and genetic characteristics of the parasite population itself indicate local transmission is the most important factor for the presence of the parasite rather than arrival of infected immigrants. While there is 70% coverage of adequate sanitation, this was insufficient to interrupt transmission. If eliminated, this focus is unlikely to readily reappear due to immigration.

Blautia and Prevotella sequences distinguish human and animal fecal pollution in Brazil surface waters

Untreated sewage discharges and limited agricultural manure management practices contribute to fecal pollution in rural Brazilian waterways. Most microbial source tracking studies have focused on Bacteroidales, and few have tested host-specific indicators in underdeveloped regions. Sequencing of sewage and human and animal feces with Illumina HiSeq revealed Prevotellaceae as the most abundant family in humans, with Lachnospiraceae and Ruminococcaceae also comprising a large proportion of the microbiome. These same families were also dominant in animals. Bacteroides, the genus containing the most commonly utilized human-specific marker in the United States was present in very low abundance. We used oligotyping to identify Prevotella and Blautia sequences that can distinguish human fecal contamination. Thirty-five of 61 Blautia oligotypes and 13 of 108 Prevotella oligotypes in humans were host-specific or highly abundant (i.e. host-preferred) compared to pig, dog, horse and cow sources. Certain human Prevotella and Blautia oligotypes increased more than an order of magnitude along a polluted river transect in rural Brazil, but traditional fecal indicator levels followed a steady or even decreasing trend. While both Prevotella and Blautia oligotypes distinguished human and animal fecal pollution in Brazil surface waters, Blautia appears to contain more discriminatory and globally applicable markers for tracking sources of fecal pollution.

Sources and distribution of surface water fecal contamination and prevalence of schistosomiasis in a Brazilian village

BACKGROUND

The relationship between poor sanitation and the parasitic infection schistosomiasis is well-known, but still rarely investigated directly and quantitatively. In a Brazilian village we correlated the spatial concentration of human fecal contamination of its main river and the prevalence of schistosomiasis.

METHODS

We validated three bacterial markers of contamination in this population by high throughput sequencing of the 16S rRNA gene and qPCR of feces from local residents. The qPCR of genetic markers from the 16S rRNA gene of Bacteroides-Prevotella group, Bacteroides HF8 cluster, and Lachnospiraceae Lachno2 cluster as well as sequencing was performed on georeferenced samples of river water. Ninety-six percent of residents were examined for schistosomiasis.

FINDINGS

Sequence of 16S rRNA DNA from stool samples validated the relative human specificity of the HF8 and Lachno 2 fecal indicators compared to animals. The concentration of fecal contamination increased markedly along the river as it passed an increasing proportion of the population on its way downstream as did the sequence reads from bacterial families associated with human feces. Lachnospiraceae provided the most robust signal of human fecal contamination. The prevalence of schistosomiasis likewise increased downstream. Using a linear regression model, a significant correlation was demonstrated between the prevalence of S. mansoni infection and local concentration of human fecal contamination based on the Lachnospiraceae Lachno2 cluster (r2 0.53) as compared to the correlation with the general fecal marker E. coli (r2 0.28).

INTERPRETATION

Fecal contamination in rivers has a downstream cumulative effect. The transmission of schistosomiasis correlates with very local factors probably resulting from the distribution of human fecal contamination, the limited movement of snails, and the frequency of water contact near the home. In endemic regions, the combined use of human associated bacterial markers and GIS analysis can quantitatively identify areas with risk for schistosomiasis as well as assess the efficacy of sanitation and environmental interventions for prevention.

Natural cytotoxicity receptor-dependent natural killer cytolytic activity directed at hepatitis C Virus (HCV) is associated with liver inflammation, African American race, IL28B genotype, and response to pegylated interferon/ribavirin therapy in chronic HCV infection

BACKGROUND

Natural killer (NK) cells are implicated in the pathogenesis of hepatitis C virus (HCV) infection and outcome of interferon (IFN)-α based therapy, although mechanisms remain unclear.

METHODS

To evaluate NK ability to control HCV infection, we analyzed healthy donor and HCV-infected donor NK-cell cytolytic activity directed at HCV-infected target cells.

RESULTS

HCV-infected subjects' natural cytotoxicity receptor (NCR)-dependent NK-cell cytolytic activity directed at HCV-infected and uninfected Huh7.5 target cells was greater than that of cells from healthy donors, and this localized to the African American subset. However, IFN-α-enhanced NK cytolytic function was lower in HCV-infected subjects, again localized mainly to the African American subset. Additionally, whereas HCV-infected Huh7.5 cells were more readily targeted than uninfected cells, the selectivity of cytolytic activity for infected targets was lower during HCV infection and after IFN-α stimulation, and lower selectivity was in part attributable to greater NKp46 expression. Furthermore, cytolytic activity was associated with higher serum aspartate aminotransferase, rs12979860 IL28B genotype, and in vivo response to pegylated IFN/ribavirin therapy.

CONCLUSIONS

These data indicate that during chronic HCV infection, race-associated increase in NCR expression and IL28B-associated cytolytic activity may participate in host response to IFN-α-containing HCV therapy.

Characteristics of the human host have little influence on which local Schistosoma mansoni populations are acquired

Background

Brazil remains the country in the Americas with the highest prevalence of schistosomiasis. A combination of control efforts and development, however, has sharply reduced its intensity and distribution. The acquisition of specific schistosome populations may be dependent on host characteristics such as sex, age, geography, work, habits and culture. How these and other host characteristics align with parasite subpopulations may guide approaches to improve control.

Methodology

A cohort of more than 90% of the residents in two rural communities in Brazil participated in an epidemiologic survey of demographic, socio-economic and behavioral characteristics. The variables sex, age, intensity of infection, socio-economic index, % lifetime spent on site, previous infection, and trips outside the district were used to group parasites infecting individuals. Schistosoma mansoni infection status was determined by examination of stools submitted on 3 different days. The aggregate of eggs collected from the whole stool was used to determine degree of population differentiation from allele frequencies for 15 microsatellites.

Conclusions/Significance

Infection prevalence was 41% for these communities, and the epidemiologic characteristics were similar to many of the endemic areas of Brazil and the world. Parasite population structuring was observed between the two communities (Jost's D 0.046, CI95% 0.042–0.051), although separated by only 8 km and connected by a highway. No structuring was observed when infected individuals were stratified by host's biologic, demographic or epidemiologic characteristics. Those most heavily infected best reflected the communities' overall parasite diversity. The lack of differentiation within villages suggests that individuals are likely to get infected at the same sites or that the same parasite multilocus genotypes can be found at most sites. The geographic structuring between villages and the lack of structuring by age of the host further supports the impression of a population little affected by migration or drift.

Schistosomiasis is one of the world's most important parasitic infections. Its elimination has proved difficult even in countries such as Brazil where access to treatment is readily available. Infection is the result of human contact with surface water where there are infected snails, so that human biology and habits may bring different individuals in contact with different groups of parasites. Identification of schistosome subpopulations may assist understanding transmission patterns and guide control efforts. We compared microsatellite allele frequencies from all of the infections in 2 small villages and determined that the movement of parasites between them was limited. Individual infections were distinct composites of parasites, but if infected humans were grouped by demographic and epidemiologic characteristics, there was no evidence that specific parasite subpopulations were being selected in these types of hosts. Infections were also not differentiated when stratified by host's age indicating that the populations were stable over time. Since the infection cycle requires human fecal contamination of water, local human behavior can to some degree be inferred from the patterns of schistosome subpopulation distribution.

Vector control measures failed to affect genetic structure of Aedes aegypti in a sentinel metropolitan area of Brazil

In order to evaluate subpopulation differentiation, effective population size (Ne) and evidence for population bottlenecks at various geographic levels, Aedes aegypti larvae were collected longitudinally from 2007 to 2009 from four areas in the city of Salvador, Brazil. The DNA from each larva was isolated and genotyped with five independent microsatellite markers. FST and Jost's D revealed significant population structuring (P<0.05) at the municipal and regional levels, while only RST was able to detect genetic differentiation at the level of strata within these areas. Ne analysis from longitudinal data did not show any evidence of significant change in population structure. The census population measured by the house index, however, showed a significant trend toward decrease in these areas. Active vector control measures did contribute to vector reduction, but this was not enough to decrease A. aegypti population genetic diversity in Salvador. The understanding of A. aegypti population dynamics may be helpful for planning and evaluation of control measures to make them more effective.

Genetic population structure of cercariae from an urban foci of Schistosoma mansoni, Brazil

Rapid urbanization in Brazil has meant that many persons from rural areas where Schistosoma mansoni is endemic have migrated to cities. Discovery of a focus of active transmission in the city of Salvador prompted a citywide survey for active and potential transmission sites. Cercariae shed from infected snails collected from four locations were used to determine how these samples were related and if they were representative of the parasite population infecting humans. Each cercarial collection was greatly differentiated from the others, and diversity was significantly lower when compared with eggs from natural human infections in one site. Egg samples collected 7 years apart in one neighborhood showed little differentiation (Jost's D = 0.01-0.03). Given the clonal nature of parasite reproduction in the snail host and the short-term acquisition of parasites, cercariae from collections at one time point are unlikely to be representative of the diversity in the human population.

Baseline levels of soluble CD14 and CD16+56- natural killer cells are negatively associated with response to interferon/ribavirin therapy during HCV-HIV-1 coinfection

Disease progression of human immunodeficiency virus type 1 (HIV-1) is associated with immune activation. Activation indices are higher during coinfection of hepatitis C virus (HCV) and HIV. The effect of immune activation on interferon α (IFN-α) therapy response is unknown. We evaluated soluble CD14 (sCD14) and natural killer (NK)-cell subsets at baseline, and during pegIFN-α2a/ribavirin therapy in HCV-HIV coinfection. The sCD14 level increased during therapy. Baseline sCD14 positively correlated with baseline HCV level and CD16(+)56(-) NK-cell frequency, and both sCD14 and CD16(+)56(-) NK cells correlated negatively with magnitude of HCV decline. IL28B genotype was associated with therapy response but not sCD14 or CD16(+)56(-) NK frequency. Markers of innate immune activation predict poor host response to IFN-α-based HCV therapy during HCV-HIV coinfection.

Three-dimensional structure of a schistosome serpin revealing an unusual configuration of the helical subdomain

Parasitic organisms are constantly challenged by the defence mechanisms of their respective hosts, which often depend on serine protease activities. Consequently, protease inhibitors such as those belonging to the serpin superfamily have emerged as protective elements that support the survival of the parasites. This report describes the crystal structure of ShSPI, a serpin from the trematode Schistosoma haematobium. The protein is exposed on the surface of invading cercaria as well as of adult worms, suggesting its involvement in the parasite-host interaction. While generally conforming to the well established serpin fold, the structure reveals several distinctive features, mostly concerning the helical subdomain of the protein. It is proposed that these peculiarities are related to the unique biological properties of a small serpin subfamily which is conserved among pathogenic schistosomes.

Pubertal stage and brain anatomy in girls

Studies of puberty have focused primarily on changes in hormones and on observable physical bodily characteristics. Little is known, however, about the nature of the relation between pubertal status and brain physiology. This is particularly important given findings that have linked the onset of puberty with both changes in cognitive functioning and increases in the incidence of depression and anxiety. The present study examined relations between pubertal stage, as assessed by Tanner staging, and brain anatomy in a sample of 54 girls aged 9-15 years. Brain morphometric analysis was conducted using high-resolution magnetic resonance imaging (MRI). The hippocampus and amygdala were manually traced on MRI scans in all participants. Stepwise regression analyses were conducted with total intracranial volume (ICV), age, and pubertal status as the predictor variables and hippocampus and amygdala volumes as outcome variables. Pubertal status was significantly associated with left amygdala volume, after controlling for both age and ICV. In addition, puberty was related to right hippocampus and amygdala volumes, after controlling for ICV. In contrast, no significant associations were found between age and hippocampal and amygdala volumes after controlling for pubertal status and ICV. These findings highlight the importance of the relation between pubertal status and morphometry of the hippocampus and amygdala, and of limbic and subcortical structures that have been implicated in emotional and social behaviors.

Genetically associated CD16(+)56(-) natural killer cell interferon (IFN)-αR expression regulates signaling and is implicated in IFN-α-induced hepatitis C virus decline

BACKGROUND

Natural killer (NK) cells likely contribute to outcome of acute hepatitis C virus (HCV) infection and interferon (IFN)-induced control of chronic HCV infection. We previously observed IFN-αR and NKp30 expression associated with IFN-α-dependent NK cell activity.

METHODS

Here, we examined CD16(+)56(-), CD16(+)56(+), and CD16(-)56(+) NK cell subset IFN-αR and NKp30 expression in relation to magnitude of HCV genotype 1 decrease during pegylated IFN-α plus ribavirin therapy.

RESULTS

We observed greater baseline IFN-αR and NKp30 expression on CD16(+)56(+) and CD16(-)56(+) NK subsets in HCV-infected patients than in healthy control subjects. Baseline CD16(+)56(-) NK IFN-αR expression was associated with IFN-α-induced pSTAT1, and both were associated with magnitude of HCV decrease during pegylated IFN-α plus ribavirin therapy. Baseline CD16(+)56(-) NK IFN-αR expression was associated with race and interleukin 28B genotype, negatively associated with aspartate aminotransferase-to platelet ratio index, and positively associated with increase in NKp30 expression after in vivo IFN-α exposure. Finally, in vitro IFN-α2a-activated NK cytolysis of HCV-infected target cells was in part dependent on NKp30, and CD16(+)56(-) NK cell IFN-αR expression correlated with cytolytic activity.

CONCLUSIONS

IFN-αR expression on CD16(+)56(-) NK cells during chronic HCV infection may in part be genetically determined, and level of expression regulates IFN-α signaling, which in turn may contribute to control of HCV infection.

Schistosoma mansoni population structure and persistence after praziquantel treatment in two villages of Bahia, Brazil

Praziquantel has been used to treat schistosome infections since 1979 and currently is the only chemotherapeutic agent in production for this purpose, raising concerns about the potential for the emergence of drug resistance. In practice, 10-20% of infected patients will continue to excrete eggs after treatment. It is not understood to what degree this represents selection of a resistant population or incomplete elimination due to the presence of immature worms at the time of treatment. We used a population genetics approach to test whether or not persistent Schistosomamansoni parasites were drawn from the same population as susceptible parasites. In this study, stool samples were collected from 96% of individuals in two small Brazilian communities (populations 482 and 367) and examined for S.mansoni eggs. The combined prevalence of S.mansoni infections in the villages was 41%. Total egg DNA was extracted from each sample and was genotyped at 15 microsatellite markers. Day-to-day variation of the infrapopulation from an individual human host was low (median differentiation using Jost's D=0.010), so that a single stool was representative of the genotypes present in stool eggs, at least in the short term. Average pairwise analysis of D among all pre-treatment infrapopulations suggested moderate differentiation (mean D=0.082 and 0.122 for the two villages), whereas the pre-treatment component population differentiation between the two communities was 0.047. The differentiation of the component population remaining after treatment from the fully susceptible component population was low (mean D=0.007 and 0.020 for the two villages), suggesting that the persistent parasites were not selected by praziquantel treatment. We will continue to follow these communities for evidence of selection or changes in population structure.

Host mouse strain is not selective for a laboratory adapted strain of Schistosoma mansoni

We genotyped pooled adult worms of Schistosoma mansoni from infected CF1, C57BL/6, BALB/c, and BALB/c interferon gamma knockout mice in order to establish if mouse strain differences selected for parasite genotypes. We also compared differentiation in eggs collected from liver and intestines to determine if there was differential distribution of parasite strains in the vertebrate host that might account for any genotype selection. We found that mouse strains with differing immune responses did not differ in resistance to infection and did not select for parasite genotypes. Schistosoma mansoni egg allele frequencies were also equally distributed in tissues and the difference between adult and egg allele frequencies was negligible.

Dengue hemorrhagic fever is associated with polymorphisms in JAK1

To identify genes associated with the clinical presentation of dengue, 50 cases of probable or possible dengue hemorrhagic fever (DHF), 236 dengue fever (DF), and 236 asymptomatic infections were genotyped for 593 single-nucleotide polymorphisms (SNPs) in 56 genes across the type 1 interferon (IFN) response pathway as well as other important candidate genes. By single locus analysis comparing DHF with DF, 11 of the 51 markers with P<0.05 were in the JAK1 gene. Five markers were significantly associated by false discovery rate criteria (q<0.20 when P<6 × 10(-4)). The JAK1 SNPs showed differential distribution by ethnicity and ancestry consistent with epidemiologic observations in the Americas. The association remained significant after controlling for ancestry and income. No association was observed with markers in the gene encoding CD209 (DC-SIGN). An association between DHF and JAK1 polymorphisms is in agreement with expression profiles showing generalized decreased type 1 IFN-stimulated gene expression in these patients.

Long-term genetic stability and population dynamics of laboratory strains of Schistosoma mansoni

Measures of genetic differentiation between populations are useful tools for understanding the long-term dynamics of parasite communities. We followed the allele frequencies of microsatellite markers in samples taken over a period of 16 yr from the Case Western Reserve University-Naval Medical Research Institute (CWRU-NMRI) laboratory strain of Schistosoma mansoni. DNA was isolated from pooled samples of adults, eggs, or cercariae collected at 46 time points and genotyped for 14 tri- or tetranucleotide microsatellite markers. For comparison, 2 S. mansoni reference strains (Biomedical Research Institute-NMRI, which has a common origin with the CWRU line, and PR-1) were analyzed over shorter periods of time. We observed that the long-term allele frequencies are generally stable in large laboratory populations of this parasite, and a high degree of similarity was observed between the allele frequencies of consecutive samples from different developmental stages. The CWRU strain, however, showed 2 periods of marked deviation from stability as demonstrated using genetic differentiation measures. The first period corresponds to an admixture event with the BRI strain in which a new equilibrium was established as the "migrants" became blended into the existing CWRU population, consistent with 23% admixture from BRI. The second corresponds to a period of genetic drift when the CWRU population size was greatly reduced with an accompanying loss in genetic diversity. Having demonstrated the utility of pooled samples for the genetic analysis of population dynamics in laboratory strains of schistosomes, this approach will be useful for analyzing field samples to determine the impact of schistosomiasis control programs on parasite population structure. Accounting only for the intensity or prevalence of parasite populations may fail to register significant changes in population structure that could have implications for resistance, morbidity, and the design of control measures.

Analysis of Schistosoma mansoni population structure using total fecal egg sampling

Many parasite populations are difficult to sample because they are not uniformly distributed between several host species and are often not easily collected from the living host, thereby limiting sample size and possibly distorting the representation of the population. For the parasite Schistosoma mansoni, we investigated the use of eggs, in aggregate, from the stools of infected individuals as a simple and representative sample. Previously, we demonstrated that microsatellite allele frequencies can be accurately estimated from pooled DNA of cloned S. mansoni adults. Here, we show that genotyping of parasite populations from reproductively isolated laboratory strains can be used to identify these specific populations based on characteristic patterns of allele frequencies, as observed by polyacrylamide gel electrophoresis and automated sequencer analysis of fluorescently labeled PCR products. Microsatellites used to genotype aggregates of eggs collected from stools of infected individuals produced results consistent with the geographic distribution of the samples. Preferential amplification of smaller alleles, and stutter PCR products, had negligible effect on measurement of genetic differentiation. Direct analysis of total stool eggs can be an important approach to questions of population genetics for this parasite by increasing the sample size to thousands per infected individual and by reducing bias.

The relative influence of polyparasitism, environment, and host factors on schistosome infection

Where prevalence of geohelminths and schistosomes is high, co-infections with multiple parasite species are common. Previous studies have shown that the presence of geohelminths either promotes or is a marker for greater prevalence and intensity of Schistosoma mansoni infections. Some of this apparent synergy may simply represent shared conditions for exposure, such as poor sanitation, and may not suggest a direct biologic interaction. We explored this question in a study of 13,279 school children in Jequié, Bahia, Brazil, with a survey of demographic characteristics and stool examinations. Cross-sectional analysis revealed a statistically significant increase in the prevalence and intensity of S. mansoni infection with increasing numbers of geohelminth species (OR 2.5, 95% CI 1.38-3.64). Less than 20% of the strength of this association was contributed by socioeconomic status or environmental conditions. Thus, polyparasitism itself, as well as intrinsic host factors, appears to produce greater susceptibility to additional helminth infections.

Moderate- and low-intensity co-infections by intestinal helminths and Schistosoma mansoni, dietary iron intake, and anemia in Brazilian children

To determine the role of moderate- and low-intensity infections with Schistosoma mansoni and intestinal helminths (hookworm, Trichuris trichiura, Ascaris lumbricoides) on the prevalence of anemia and their relationship to iron consumption, a cross-section of 1,709 children in rural Brazil was studied. All participants were selected for infection with one or multiple helminthic parasites, and demographic, anthropometric, and dietary intake were surveyed. The prevalence and intensity were as follows: hookworm infection, 15.7% and 8.6 eggs/g; T. trichiura, 74.8% and 190.5 eggs/g; A. lumbricoides, 63% and 1,905.5 eggs/g; S. mansoni, 44.5% and 60.3 eggs/g. There was no increase in odds ratio for anemia with any combination of intestinal helminths without S. mansoni infection. By logistic regression, the odds ratio for having anemia when infected with S. mansoni and two intestinal helminths was 1.7 (95% CI, 1.1-2.5) and for S. mansoni and three intestinal helminths was 2.4 (95% CI, 1.2-4.6) compared with children with a single parasite species. Children with an adequate intake of iron had no increased odds of anemia independent of the combination of parasite infections.

Biochemical and immunologic predictors of efficacy of treatment or reinfection risk for Schistosoma mansoni

Most Schistosoma mansoni infections are egg-negative after a single dose of oxamniquine. A cohort of 661 infected children was treated at 6-month intervals and assessed for nutritional and parasitological status. Initial biochemical and immunologic markers were measured in a subset of 84 children. All were treated at the start of therapy and at 6 months. Immunoglobulins only served as markers for active infection. No markers were predictive of cure or reinfection, except initial infection intensity and serum low-density lipoprotein. Ten percent were persistently infected and had no change in infection intensity at any time-point. Several factors suggest that this group was biologically different. In addition to failing to reduce their worm burden, they had significantly higher initial intensity of infection (100 versus 65 eggs/g, P = 0.001) and significantly lower initial serum low-density lipoprotein (72 versus 104 mg/dL, P = 0.045). The biologic plausibility of this observation is discussed.

Microsatellite analysis of pooled Schistosoma mansoni DNA: an approach for studies of parasite populations

Human parasites are often distributed in metapopulations, which makes random sampling for genetic epidemiology difficult. The typical approach to sampling Schistosoma mansoni involves laboratory passage to obtain individual worms with small sample size and selection bias as a consequence. By contrast, the naturally pooled samples from egg output in stool or urine directly represent the genetic composition of current populations. To test whether pooled samples could be used to estimate population allele frequencies, DNA from individual cloned parasites was pooled and amplified by PCR for 7 microsatellites. By polyacrylamide gel analysis, the relative band intensities of the products from the major alleles in the pooled samples differed by 0-6% from the summed intensities of the individual clones (mean = 2.1%+/-2.1% S.D.). The number of PCR cycles (25-40) did not influence the accuracy of the estimate. Varying the frequency of 1 allele in pooled samples from 32 to 69% likewise did not affect accuracy. Allele frequency estimates from aggregate samples such as eggs will be a better foundation for studies of parasite population dynamics as well as the basis for large-scale association studies of host and parasite characteristics.

Schistosomal hepatic fibrosis and the interferon gamma receptor: a linkage analysis using single-nucleotide polymorphic markers

A minority of individuals infected with the parasite Schistosoma mansoni develops hepatic fibrosis. HLA studies in Egypt and a candidate gene search in a Sudanese population indicate that the host's genetics contribute to disease susceptibility. In an Egyptian community, 32.7% of individuals 11 years and older had significant fibrosis by WHO ultrasound criteria. Linkage to 10 candidate genes was tested using 89 affected sibling pairs from 40 pedigrees in this community. The candidates included genes that initiate fibrosis, participate in collagen synthesis, or control collagen degradation. Two to four single-nucleotide polymorphisms (SNPs) were genotyped per locus, and 188 individuals were genotyped at 48 markers. Model-free modified Haseman-Elston analysis identified linkage to a SNP in the interferon gamma receptor locus (P=0.000001). There was also weak evidence for linkage to the interleukin 13-4 region and tissue growth factor beta 1.

Childhood stunting in Northeast Brazil: the role of Schistosoma mansoni infection and inadequate dietary intake

OBJECTIVE

To evaluate the relationship between stunting, Schistosoma mansoni infection and dietary intake in schoolchildren.

DESIGN

This is a cross-sectional study. Two stool samples were obtained from each child and examined quantitatively for the presence of S. mansoni, Ascaris lumbricoides and Trichuris trichiuria eggs. Information on dietary intake, and demographic, biologic and socioeconomic variables was elicited during the in-home survey. Logistic regression was used to evaluate the association between stunting (height for age < -2s.d.), parasitic infection and food consumption.

SETTING

The study was carried out in the city of Nazaré, located in the Recôncavo region of the State of Bahia, Northeastern Brazil.

SUBJECTS

The sample consisted of 461 children 7-14 y old, 228 boys and 233 girls, recruited from public schools.

RESULTS

Of the children studied, 55.1% presented with S. mansoni infection and 22.1% were stunted. The median protein, lipid and carbohydrates intake were 47.8, 36.0 and 248.2 g/day, respectively. The median caloric consumption was 1527.0 kcal (6388.97 kJ/day). The analysis indicated that children heavily infected (> or = 400 eggs/g of stool) with S. mansoni had a 2.74-fold (95% CI: 1.32-5.67) higher risk of stunting than uninfected children, and those with inadequate intake of lipid (< 36 g/day) had a 1.83-fold (95% CI: 1.05-3.20) increased risk of stunting compared to those with adequate diets.

CONCLUSION

Heavy S. mansoni infection and inadequate dietary intake of fat in schoolchildren play a significant and independent role in the development of stunting. This meaning that nutritional interventions in this age group in S. mansoni endemic areas must include the diagnosis and treatment of the infection associated with dietary measures.

SPONSORSHIP

This study was supported by the Thrasher Foundation. Sandra Maria Conceição Pinheiro is a National Council on Technological Development Scholarship Awardee (CNPq), #302228/81-0.

Low heritable component of risk for infection intensity and infection-associated disease in urinary schistosomiasis among Wadigo village populations in Coast Province, Kenya

To estimate their heritable component of risk for Schistosoma haematobium infection intensity and disease, we performed a community-based family study among an endemic population in coastal Kenya. Demography and family linkages were defined by house-to-house interviews, and infection prevalence and disease severity were assessed by standard parasitologic testing and by ultrasound. The total population was 4,408 among 912 households, with 241 identified pedigree-household groups. Although age- and sex-adjusted risk for greater infection intensity was clustered within households (odds ratio = 2.7), analysis of extended pedigree-household groups indicated a relatively low heritability score for this trait (h2 = 0.199), particularly after adjustment for common household exposure effects (adjusted h2 = 0.086). Statistical evidence was slightly stronger (h2 = 0.353) for familial clustering of bladder morbidity, with an adjusted h2 = 0.142 after accounting for household exposure factors. We conclude that among long-established populations of coastal Kenya, heritable variation in host susceptibility is low, and likely plays a minimal role in determining individual risk for infection or disease.

Fatores de risco para anemia por deficiência de ferro em crianças e adolescentes parasitados por helmintos intestinais

OBJECTIVE

To investigate risk factors for iron-deficiency anemia in children and adolescents (7 to 17 years of age) with intestinal helminthic infections.

METHODS

A cross-sectional study was carried out with 1 709 children and adolescents living in Jequié, a town in the state of Bahia, Brazil, who had mild to moderate infection by Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura, or hookworms. We obtained data concerning hemoglobin levels (using a portable hemoglobinometer), dietary habits (24-hour dietary recall), parasitic infections (Kato-Katz method), sanitary conditions (water supply, sewage connection, garbage collection), housing conditions (type of construction, number of persons per room), income, and amount of schooling of the parents or guardians. The risk factors for anemia were studied based on a hierarchical model of causality.

RESULTS

The prevalence of parasitic infection was 74.8% for T. trichiura, 63.0% for A. lumbricoides, 55.5% for S. mansoni, and 15.7% for hookworms. Among the children and adolescents studied 32.2% were anemic. After adjustment for confounding variables, the results of the multivariate analysis showed that the following variables were significantly associated with anemia: per capita family income below US$ 27 (equal to one fourth of the Brazilian minimum wage), male sex, age of 7 to 9 years, and inadequate intake of bioavailable iron.

CONCLUSIONS

The initiatives to control anemia in the group at greatest risk, as identified in this study, should seek to increase the consumption of iron-rich foods, boost the bioavailability of the iron ingested, and improve socioenvironmental conditions.

Measuring morbidity in schistosomiasis mansoni: relationship between image pattern, portal vein diameter and portal branch thickness in large-scale surveys using new WHO coding guidelines for ultrasound in schistosomiasis

OBJECTIVE

World Health Organization consensus meetings on 'Ultrasound in Schistosomiasis' in 1996 and 1997 anticipated further challenges in the global implementation of a standardized protocol for morbidity assessment in schistosomiasis mansoni. We evaluated the performance of the qualitative and quantitative components of the new Niamey criteria.

METHOD

Use of the Niamey protocol among 3954 subjects in two linked, cross-sectional ultrasound surveys of Schistosoma mansoni-endemic populations in Egypt and Kenya.

RESULTS

There were significant differences between Egyptian and Kenyan sites in prevalence and age distribution of S. mansoni-related hepatic fibrosis (36%vs. 3%, P < 0.001). Protocol image pattern scoring could be performed quickly and was stable to interobserver variation. However, there were unintended but systematic differences between study sites in the measurement of portal vein diameter (PVD) and wall thickness. By Niamey criteria, a high prevalence of portal dilation was scored for normal Egyptian subjects, which reduced the predictive value of image pattern for portal hypertension. Using alternative height-indexing of PVD, image pattern plus PVD findings predicted 15% of Egyptians and 2.5% of Kenyans were at risk for variceal bleeding, whereas locally derived PVD norms estimated 25% of Egyptians and 12% of Kenyans to be at possible risk.

CONCLUSION

Niamey scoring criteria performed acceptably as a relative grading system for disease in schistosomiasis mansoni, but failed to account fully for site-to-site variation in test performance and morbidity prevalence. Consequently, standardized image pattern scoring appears to provide the most useful tool for detection and comparison of S. mansoni-associated morbidity in large-scale surveys.

Epidemiologia do desenvolvimento cognitivo de escolares em Jequié, Bahia, Brasil: procedimentos de avaliação e resultados gerais

Este artigo descreve metodologia, aplicação e utilidade do teste das Matrizes Progressivas de Raven e do Teste de Sondagem Intelectual (TSI), comparando-os ainda com o rendimento escolar do aluno, em Jequié, Bahia. O Raven, que avalia o raciocínio não-verbal, foi aplicado a 374 escolares (7 a 17 anos). Somente 231 TSI foram respondidos porque requeriam habilidades de leitura e escrita. Foram coletadas notas escolares para todos os participantes. Um questionário avaliando recursos da escola e perfil do professor foi respondido por duzentos professores. Os escores dos testes Raven e TSI apresentaram uma boa correlação entre si (r = 0,53, p < 0,001) porém menor com as médias escolares (r = 0,22, p < 0,001 e r = 0,12, p < 0,07 respectivamente). Os escores do Raven e do TSI apresentaram baixas correlações com os conceitos escolares. A média de escores, tanto no teste Raven como no TSI, foi maior entre os meninos, sendo superior o desempenho das meninas nas notas escolares. De maneira geral o nível de desempenho cognitivo encontrado está aquém do esperado em crianças do grupo de idade analisada.

Population-based differences in Schistosoma mansoni- and hepatitis C-induced disease

Two populations with differing histories of Schistosoma mansoni and hepatitis C infection were compared directly for severity of disease and extent of comorbidity. Demographic, parasitologic, and ultrasound surveys were conducted on 2038 Egyptians and on 2120 Kenyans. Hepatitis B and C serologies and transaminase levels were obtained from a subset at each site. Despite significantly lower prevalence and intensity of infection, Egyptians had a higher prevalence of severe schistosomal fibrosis than Kenyans (36.8% vs. 4.6%). Hepatitis C infection was 3 times more prevalent among Egyptians, and evidence of hepatocellular damage was significantly greater among Egyptians. There was no interaction between S. mansoni infection or disease and the prevalence or severity of hepatitis C. For both infections, the intensity or prevalence of infection was a poor predictor of morbidity. The prevalence of disease in the Egyptian population from different pathogens suggests a generalized susceptibility to inflammatory liver disease.

[Epidemiology of schoolchildren's cognitive development in Jequié, Bahia State, Brazil: assessment procedures and general results]

This paper describes the methodology, applicability and utility of the Raven Progressive Matrix (Raven Test) and the Brazilian Intellectual Probe (TSI), comparing them with school achievement in a typical medium-size urban community of Northeastern Brazil. 388 schoolchildren (7-17 years old) were examined, with 371 Raven tests applied. Only 231 TSIs were completed, since 106 students were illiterate. School grades were obtained for all participants. A questionnaire evaluating school resources, and teacher profiles was answered by 200 teachers. Raven and TSI test scores were highly correlated (r = 0.53, p < 0.001), but both correlated weakly with overall school grade (r = 0.22, p < 0.001 and r = 0.12, p < 0.07 respectively). For individual school grades, the Raven scores showed statistically significant correlation with all subjects, while the Brazilian TSI presented statistically significant correlation only with geography, history and sciences. Boys' mean scores were higher than girls' for both the Raven and the TSI Tests, but for the school grades girls performed better. In general, level of cognitive development was below that expected for children in the age-group analyzed.

Medial temporal lobe in childhood-onset schizophrenia

The majority of anatomic and neuroimaging studies in adult-onset schizophrenia demonstrate decreased volumes of the medial temporal lobe when compared with findings in normal individuals. The goal of this study was to investigate the hypothesis that subjects with childhood-onset schizophrenia would show decreased volumes of the medial temporal lobe when compared to normal children. Thirteen children meeting DSM-III-R criteria for schizophrenia (mean age 14.2+/-3.8 years) and 20 normal children (mean age 12.0+/-2.8 years) were investigated. MRI scans were performed on a 1.5-T GE Signa MR scanner using a coronal plane SPGR at 1.4-mm slice thickness. Volumes were assessed by manually tracing bilateral hippocampus, amygdala and temporal lobes. After adjustment for age and total brain volume, the amygdala was significantly larger in the schizophrenics than in the control subjects, and this volume increase was more pronounced on the left side. Hippocampus volumes did not differ significantly across groups. There was a nearly significant left-greater-than-right asymmetry of the amygdala in the schizophrenic group but not in the normal group. A nearly significant right-greater-than-left asymmetry was found in the anterior hippocampus for both schizophrenic and control groups. These findings are consistent with previous reports of at least initial sparing of temporal lobe regions in childhood-onset schizophrenia.

Probabilistic approaches for atlasing normal and disease-specific brain variability

The extreme variability in the structural conformation of the human brain poses significant challenges for the creation of population-based atlases. The ability to statistically and visually compare and contrast brain image data from multiple individuals is essential to understanding normal variability within a particular population as well as differentiating normal from diseased populations. This paper introduces the application of probabilistic atlases that describe specific subpopulations, measures their variability and characterizes the structural differences between them. Utilizing data from structural MRI, we have built atlases with defined coordinate systems creating a framework for mapping data from functional, histological and other studies of the same population. This paper describes the basic approach and a brief description of the underlying mathematical constructs that enable the calculation of probabilistic atlases and examples of their results from several different normal and diseased populations.