Risk factors for infection with Giardia duodenalis in pre-school children in the city of Salvador, Brazil

Improved household flooring is associated with lower odds of enteric and parasitic infections in low- and middle-income countries: A systematic review and meta-analysis

Enteric and parasitic infections such as soil-transmitted helminths cause considerable mortality and morbidity in low- and middle-income settings. Earthen household floors are common in many of these settings and could serve as a reservoir for enteric and parasitic pathogens, which can easily be transmitted to new hosts through direct or indirect contact. We conducted a systematic review and meta-analysis to establish whether and to what extent improved household floors decrease the odds of enteric and parasitic infections among occupants compared with occupants living in households with unimproved floors. Following the PRISMA guidelines, we comprehensively searched four electronic databases for studies in low- and middle-income settings measuring household flooring as an exposure and self-reported diarrhoea or any type of enteric or intestinal-parasitic infection as an outcome. Metadata from eligible studies were extracted and transposed on to a study database before being imported into the R software platform for analysis. Study quality was assessed using an adapted version of the Newcastle-Ottawa Quality Assessment Scale. In total 110 studies were eligible for inclusion in the systematic review, of which 65 were eligible for inclusion in the meta-analysis after applying study quality cut-offs. Random-effects meta-analysis suggested that households with improved floors had 0.75 times (95CI: 0.67-0.83) the odds of infection with any type of enteric or parasitic infection compared with household with unimproved floors. Improved floors gave a pooled protective OR of 0.68 (95CI: 0.58-0.8) for helminthic infections and 0.82 OR (95CI: 0.75-0.9) for bacterial or protozoan infections. Overall study quality was poor and there is an urgent need for high-quality experimental studies investigating this relationship. Nevertheless, this study indicates that household flooring may meaningfully contribute towards a substantial portion of the burden of disease for enteric and parasitic infections in low- and middle-income settings.

The risk factors for intestinal Giardia spp infection: Global systematic review and meta-analysis and meta-regression

Parasitic infections are a public health concern as they can cause aggression, growth retardation, weight loss, anemia, and other health problems. In this study, a systematic review and meta-analysis were performed to find an association between the probable social-environmental risk factors including lack of safe drinking water, no hand washing, sex, age, no access to education, no access to toilet, and Giardia spp infection. We conducted literature research among international databases including Scopus, PubMed, Web of Science and Cochrane from1 January 1995 to March 15, 2020, including 23 articles with 102 studies while the odds ratio (OR) was calculated using 2 × 2 tables or extracted. The pooled effect size with 95% confidence intervals (CIs) was estimated using a random or fixed-effects model. The results show a significant association between intestinal Giardia spp infection risk and lack of safe drinking water (OR: 1.14; 95%CI: 1.02-1.25); no access to toilet (OR: 1.22; 95%CI: 1.07-1.37); and age (2-10 vs 10-30 year) (OR: 1.42; 95%CI: 1.09-1.78). An insignificant association was observed between intestinal Giardia spp infection risk and age (<2 vs 2-10 year) (OR: 0.89; 95%CI: 0.75-1.02); no access to education (OR: 1.10; 95%CI: 0.80-1.40); Sex (male vs female) (OR: 1.04; 95%CI: 0.74-1.34); and no handwashing (OR: 1.18; 95%CI: 0.87-1.49). The results of meta-regression also indicate that intestinal Giardia spp infection has decreased over time (C= -0.024, p-value = 0.03) significantly, and also by growth of human development index (HDI) (C= - 0.42, p-value = 0.29) insignificantly. Improvement of personal hygiene, sanitation and raising public awareness can be effective in reducing Giardia spp infections.

The Intersection of Immune Responses, Microbiota, and Pathogenesis in Giardiasis

Giardia lamblia is one of the most common infectious protozoans in the world. Giardia rarely causes severe life-threatening diarrhea, and may even have a slight protective effect in this regard, but it is a major contributor to malnutrition and growth faltering in children in the developing world. Giardia infection also appears to be a significant risk factor for postinfectious irritable bowel and chronic fatigue syndromes. In this review we highlight recent work focused on the impact of giardiasis and the mechanisms that contribute to the various outcomes of this infection, including changes in the composition of the microbiota, activation of immune responses, and immunopathology.

Evolution of Socioeconomic Conditions and Its Relation to Spatial-Temporal Changes of Giardiasis and Helminthiasis in Amazonian Children

This study analyzed the evolution of socioeconomic, sanitary, and personal factors as well as spatiotemporal changes in the prevalence of helminthiasis and giardiasis in urban Amazonian children between 2003 and 2011. Child age, lack of sanitation, and lack of access to bottled water were identified as significant associated factors for helminthiasis and giardiasis. There was an overall improvement in socioeconomic and sanitary conditions in the city resulting in decreased helminth prevalences from 12.42 to 9.63% between 2003 and 2010, but the prevalence increased to 15.03% in 2011 due to migratory movement and unstable sanitary conditions. As for Giardiasis, socioeconomic and environmental changes were not enough to reduce prevalence (16% in 2003 and 23% in 2011). Spatial analysis identified a significant cluster for helminthiasis in an area of poor housing conditions. Control programs in the Amazon need to target high-risk areas focusing changes in sanitation, water usage, and health education.

POTENTIAL CROSS-CONTAMINATION OF SIMILAR Giardia duodenalis ASSEMBLAGE IN CHILDREN AND PET DOGS IN SOUTHERN BRAZIL, AS DETERMINED BY PCR-RFLP

Giardia duodenalis is an enteric parasite that has distinct genetic groups. Human infections are mainly caused by assemblages A and B, although sporadic infections by assemblages C and D have also been reported. Animals can be infected by a wide range of assemblages (A to H). The aim of this study is to identify the assemblages and sub-assemblages of G. duodenalis with zoonotic features in fecal samples of school-aged children, and in dogs that coexist in the same households in Lages, Santa Catarina, Brazil. Fecal samples of 91 children and 108 dogs were obtained and G. duodenalis cysts were detected in samples from 11 (12.08%) children and 10 (9.25%) dogs. DNA extracted from the 21 positive samples was analyzed by PCR-RFLP, using the gdh gene. Results showed the presence of sub-assemblages AI (2/11), AII (4/11), BIII (2/11), and BIV(3/11) among children and AI (5/10) and BIV(3/10) in dogs, with zoonotic characteristics, and the carnivore specific assemblage C (2/10). G. duodenalis was found to infect both children and dogs living in the same household, with the same sub-assemblage (BIV) indicating that pet dogs are a potential risk of transmission of G. duodenalis to humans.

Genotyping of Giardia duodenalis isolates in asymptomatic children attending daycare centre: evidence of high risk for anthroponotic transmission

Giardia duodenalis is a common intestinal parasite infecting children attending daycare centres. This study aimed to verify Giardia occurrence and the genotypes of isolates infecting children aged 0–6 years and workers at a daycare centre in the state of São Paulo, Brazil. The families of children who tested positive for Giardia, were asked to provide stool samples from household members and their dogs. Samples (123 children, 14 centre employees, 44 household members, 19 children after treatment, and 20 dogs) were examined for intestinal parasites using concentration methods. DNA extracted from all samples was submitted for polymerase chain reaction (PCR) testing and the amplicons generated were used for multilocus sequence typing of beta-giardin (bg), triose phosphate isomerase (tpi) and glutamate dehydrogenase (gdh) genes. Giardia was detected in 15·9% and 28·6% of the 220 samples by microscopy and PCR, respectively. Analysis of sequences retrieved from 29 isolates revealed both assemblages A (31%) and B (69%). Sub-assemblages AII, BIII and BIV were identified and the alignment of the bg, gdh and tpi sequences revealed the presence of some single nucleotide polymorphisms, especially in assemblage B sequences. The higher predominance of assemblage B and the identification of the AII type support the view that anthroponotic transmission appears to be an important route of transmission in environments that concentrate children at an age when poor hygiene practices make them more vulnerable to such infection.

Effect of sanitation and water treatment on intestinal protozoa infection: a systematic review and meta-analysis

BACKGROUND

Pathogenic intestinal protozoa infections are responsible for substantial mortality and morbidity, particularly in settings where people lack improved sanitation and safe drinking water. We assessed the relation between access to, and use of, sanitation facilities and water treatment and infection with intestinal protozoa.

METHODS

We did a systematic review and searched PubMed, ISI Web of Science, and Embase from inception to June 30, 2014, without restrictions on language. All publications were examined by two independent reviewers and were included if they presented data at the individual level about access or use of sanitation facilities or water treatment, in combination with individual-level data on human intestinal protozoa infections. Meta-analyses using random effects models were used to calculate overall estimates.

FINDINGS

54 studies were included and odds ratios (ORs) extracted or calculated from 2 × 2 contingency tables. The availability or use of sanitation facilities was associated with significantly lower odds of infection with Entamoeba histolytica or Entamoeba dispar (OR 0·56, 95% CI 0·42-0·74) and Giardia intestinalis (0·64, 0·51-0·81), but not for Blastocystis hominis (1·03, 0·87-1·23), and Cryptosporidium spp (0·68, 0·17-2·68). Water treatment was associated with significantly lower odds of B hominis (0·52, 0·34-0·78), E histolytica or E dispar (0·61, 0·38-0·99), G intestinalis (0·63, 0·50-0·80), and Cryptosporidium spp infections (0·83, 0·70-0·98).

INTERPRETATION

Availability and use of sanitation facilities and water treatment is associated with lower odds of intestinal protozoa infections. Interventions that focus on water and sanitation, coupled with hygiene behaviour, should be emphasised to sustain the control of intestinal protozoa infections.

FUNDING

Swiss National Science Foundation (project numbers PBBSP3-146869 and P300P3-154634), Medicor Foundation, European Research Council (614739-A_HERO).

Long-Term Predictors of Recurrent Laboratory-Confirmed Giardiasis: A 10-Year National Surveillance Study

During 2002 to 2011, 275 of 6828 children with giardiasis in Israel were reported with recurrent, over 6 months apart, episodes. The only significant multivariable-adjusted risk predictor of a recurrent episode was non-Jewish ethnicity (hazard ratio, 4.61 [95% confidence interval, 3.32-6.40]; P < .001), also accompanied by significant interaction with lower maternal education.

Disadvantaged pre-schoolers attending day care in Salvador, Northeast Brazil have a low prevalence of anaemia and micronutrient deficiencies

OBJECTIVE

To examine the micronutrient status of disadvantaged pre-schoolers from Northeast Brazil, following the introduction of pro-poor policies, by assessing the prevalence of anaemia and micronutrient deficiencies and the role of sociodemographic factors, genetic Hb disorders and parasitic infections.

DESIGN

In a cross-sectional study, data on sociodemographic status, health, growth, genetic Hb disorders, parasites and nutrient supply from day-care meals were obtained. Fasting blood samples were collected and analysed for Hb, serum ferritin, transferrin receptor, folate, vitamin B₁₂, retinol, Zn and Se.

SETTING

Seven philanthropic day-care centres serving urban slums in Salvador, Northeast Brazil.

SUBJECTS

Pre-schoolers aged 3-6 years from disadvantaged households.

RESULTS

Of the 376 sampled children, 94 % were of black or mixed race; 33 % and 29 % had at least one genetic Hb disorder and intestinal parasite, respectively. Stunting and underweight were ≤5 %; 14 % were overweight. Day-care centres supplied micronutrient-dense meals and snacks each weekday. Less than 10 % of pre-schoolers had anaemia and micronutrient deficiencies. Predictors (P < 0·05) of Hb were α(3·7) thalassaemia, Se and retinol (but not ferritin). Micronutrient predictors (P < 0·05) were: elevated α₁-glycoprotein for ferritin, Hb AS and BMI Z-score >1 for transferrin receptor, Zn and elevated α₁-glycoprotein for retinol, sex and helminths for Se, helminths for vitamin B₁₂, and Giardia intestinalis infection for serum folate.

CONCLUSIONS

Impaired growth, anaemia and micronutrient deficiencies were uncommon among these disadvantaged pre-schoolers attending day care. A range of interventions including provision of micronutrient-dense, fortified day-care meals, deworming and vitamin A supplementation likely contributed to improved micronutrient status, suggesting expanded coverage of these programmes.

Reducing occurrence of Giardia duodenalis in children living in semiarid regions: impact of a large scale rainwater harvesting initiative

Background

In Brazil, about two million people living in rural semiarid regions were benefited with the construction of rainwater cement cisterns, as an initiative from the program “One Million Cisterns” (P1MC). Nevertheless, few epidemiological studies have been conducted to assess health risks or protection effects associated with consumption of this water source. The aim of this study was to evaluate whether access to rainwater harvesting cisterns is associated with the decrease in the occurrence of Giardia duodenalis infections in children, compared to other children living in households supplied by other water sources.

Methodology/Principal Findings

A quasi-experimental study with two concurrent cohorts was developed in two rural municipalities of the semiarid region of Brazil. A sample of 664 children, aged between 4 months and 5 years old, was followed up, of which 332 had access to rainwater cisterns (cistern group) and 332 did not, having water supplied from alternative sources (comparison group). In a period of approximately one year (2010) intestinal parasites were investigated in feces three times. The prevalence of G. duodenalis in children from the cistern group ranged from 4.8 to 10.5%, while the prevalence in the comparison group ranged from 7.6 to 16.7%. Multivariate analysis (GEE) showed a higher risk of G. duodenalis infection in children who did not have access to rainwater cisterns, when compared to children who did (OR 1.72; 95% CI 1.14–2.59). The other variables associated with G. duodenalis infection were: number of rooms per house (OR 0.89; 95% CI 0.80–0.99); family income (OR0.48; 95% CI 0.26–0.88); birth order (OR 1.72; 95% CI 1.17–2.51); preterm children (OR 1.70; 95% CI 1.19–2.43); and improper hand hygiene prior to food preparation (OR 4.78; 95% CI 1.95–11.76).

Conclusions/Significance

Ownership of a rainwater cistern is associated with a lower prevalence of G. duodenalis infection in children after adjustment for environmental and family-related factors. Nevertheless, the study suggests the necessity to complement physical interventions with actions related to personal and domestic hygiene to enable further reductions in parasite infections affecting mainly the underprivileged populations.

Currently, rainwater harvesting cisterns built up through the “One Million Cisterns” Program, coordinated by the Brazilian Government, represents the most important public policy for water supply in the rural semiarid region of Brazil. Despite the extensive use of this water provision, few studies have been performed to assess the associated health impact. To assess such impact, this study investigated factors associated with the occurrence of Giardia duodenalis (protozoan closely related to the ingestion of contaminated water) in children aged between 4 months and five years old. Two distinct groups of children, one with access to rainwater cisterns (cistern group) and the other without cisterns, with water supplied from alternative sources, including rivers, springs or dams (comparison group) were followed up for approximately one year. It was observed that the risk occurrence of G. duodenalis prevalence was greater in children from the comparison group, when compared with those from the cistern group, indicating that the odds of infection by this parasite were 1.72 times greater for comparison group children. In conclusion, the study showed health benefits related to rainwater cisterns, but also identified that other complementary sanitation interventions are needed to minimize the risk of disease in populations with limited access to drinking water.

Epidemiology and control of child toxocariasis in the western Brazilian Amazon - a population-based study

Toxocara spp. infection and the seroconversion rate in the Amazon have been poorly investigated. This study analyzed individual and household-level risk factors for the presence of IgG antibodies to Toxocara spp. in urban Amazonian children over a period of 7 years and evaluated the seroconversion rates over a 1-year follow-up. In children < 59 months of age, the overall prevalence rate was 28.08% in 2003 and 23.35% in 2010. The 2010-2011 seroconversion rates were 13.90% for children 6-59 months of age and 12.30% for children 84-143 months of age. Multilevel logistic regression analysis identified child age, previous wheezing, and current infection with hookworm as significant associated factors for Toxocara spp. seropositivity in 2003. In 2010, age, previous helminthiasis, and having a dog were associated with seropositivity, whereas having piped water inside the household was a protective factor. Control programs mainly need to target at-risk children, water quality control, and animal deworming strategies.

Factors influencing growth and intestinal parasitic infections in preschoolers attending philanthropic daycare centers in Salvador, Northeast Region of Brazil

Poor growth and intestinal parasitic infections are widespread in disadvantaged urban children. This cross-sectional study assessed factors influencing poor growth and intestinal parasites in 376 children aged three to six years in daycare centers in Salvador, in the Northeast Region of Brazil. Data was obtained from seven daycare centers on child weight, height, socio-economic status, health and intestinal parasites in stool samples. Prevalence of moderate underweight (< -1SD > -2SD), wasting and stunting was 12%, 16% and 6% respectively. Socioeconomic status, birth order, and maternal weight were predictors of poor anthropometric status. Almost 30% of children were infected with more than one intestinal parasite. Helminths (17.8%), notably Trichuris trichiura (12%) and Ascaris lumbricoides (10.5%), and protozoan Giardia duodenalis (13%) were the most common types of parasites detected. One percent of children had hookworm and Cryptosporidium sp. and 25% had non-pathogenic protozoan cysts. Boys from families with very low socio-economic status had lower linear growth and presented a greater risk of helminth infection. Deworming is considered an alternative for reducing the prevalence of intestinal parasitic infections in this age group.

Do environments in infancy moderate the association between stress and inflammation in adulthood? Initial evidence from a birth cohort in the Philippines

Chronic inflammation is a potentially important pathway through which psychosocial stressors increase risk for cardiovascular disease. However, prior research on stress and inflammation has been conducted almost exclusively in high income, industrialized populations with low levels of infectious disease. In this study we test the hypothesis that psychosocial stressors are associated with elevated concentrations of C-reactive protein (CRP) among young adults in the Philippines (n=1622), who have grown up in an ecological and epidemiological setting that differs substantially from that of the US. In addition, we apply a developmental, ecological perspective to consider whether microbial and nutritional environments in infancy alter patterns of association between stressors and CRP. Data come from the Cebu Longitudinal Health and Nutrition Survey, a prospective cohort study that began collecting data in 1983-1984 when participants were in utero. A series of regression models indicate trends toward significant interactions between perceived stress and environmental factors in infancy, including exposure to animal feces, season of birth, and birth weight. Parental absence in childhood was a significant predictor of CRP in adulthood in interaction with exposure to animal feces in infancy. Positive associations between stressors and CRP were only evident for individuals with lower levels of microbial exposure in infancy, or lower birth weight. These results suggest that early environments influence the development of inflammatory phenotypes in ways that moderate sensitivity to psychosocial stressors in adulthood, and they underscore the value of a comparative, developmental approach to research on social environments, inflammation, and disease.

Prevalence of intestinal protozoa infection among school-aged children on Pemba Island, Tanzania, and effect of single-dose albendazole, nitazoxanide and albendazole-nitazoxanide

Background

Pathogenic intestinal protozoa infections are common in school-aged children in the developing world and they are frequently associated with malabsorption syndromes and gastrointestinal morbidity. Since diagnosis of these parasites is difficult, prevalence data on intestinal protozoa is scarce.

Methods

We collected two stool samples from school-aged children on Pemba Island, Tanzania, as part of a randomized controlled trial before and 3 weeks after treatment with (i) single-dose albendazole (400 mg); (ii) single-dose nitazoxanide (1,000 mg); (iii) nitazoxanide-albendazole combination (1,000 mg–400 mg), with each drug given separately on two consecutive days; and (iv) placebo. Formalin-fixed stool samples were examined for the presence of intestinal protozoa using an ether-concentration method to determine the prevalence and estimate cure rates (CRs).

Results

Almost half (48.7%) of the children were diagnosed with at least one of the (potentially) pathogenic protozoa Giardia intestinalis, Entamoeba histolytica/E. dispar and Blastocystis hominis. Observed CRs were high for all treatment arms, including placebo. Nitazoxanide showed a significant effect compared to placebo against the non-pathogenic protozoon Entamoeba coli.

Conclusions

Intestinal protozoa infections might be of substantial health relevance even in settings where they are not considered as a health problem. Examination of a single stool sample with the ether-concentration method lacks sensitivity for the diagnosis of intestinal protozoa, and hence, care is indicated when interpreting prevalence estimates and treatment effects.

Assessing the infection risk of Giardia and Cryptosporidium in public drinking water delivered by surface water systems in Sao Paulo State, Brazil

A survey of Giardia and Cryptosporidium was conducted in surface water used as drinking water sources by public water systems in four densely urbanized regions of Sao Paulo State, Brazil. A Quantitative Microbial Risk Assessment, based on protozoa concentrations, was performed to estimate the probability of protozoa infection associated with drinking water ingestion. A total of 206 source water samples were analyzed over a 24 month period using the USEPA Method 1623. The risk of infection was estimated using an exponential dose response model, children and adults exposure and a gamma distribution for (oo)cyst concentrations with three scenarios for treating censored data. Giardia was detected in 102 of the samples, and 19 of them were also positive for Cryptosporidium, with maximum concentrations of 97.0 cysts/L and 6.0 oocysts/L, respectively. Risk distributions were similar for the three scenarios. In the four regions, the estimated risk of Giardia infection per year, for adults and children, ranged from 0.29% to 2.47% and from 0.08% to 0.70%, respectively. Cryptosporidium risk infection varied from 0.15% to 0.29% for adults and from 0.04% to 0.08% for children. In both cases, the calculated risk surpassed the risk of infection of 10(-4) (1:10,000) defined as tolerable by USEPA for a yearly exposure. The probability of Giardia infection was very close to the rates of acute diarrheic disease for adults (1% to 3%) but lower for children (2% to 7%). The daily consumption of drinking water was an important contributing factor for these differences. The Microbiological Risk Assessment carried out in this study provides an indication of infection risks by Giardia and Cryptosporidium in the population served by these source waters. Strategies for source water protection and performance targets for the water treatment should be established to achieve the required level of public health risk.

Giardiasis among different tribes of Orang Asli in Malaysia: highlighting the presence of other family members infected with Giardia intestinalis as a main risk factor

The flagellate protozoan parasite, Giardia intestinalis, is widely distributed throughout the world with a high prevalence in developing countries in the tropics and subtropics, including Malaysia. Approximately 200 million people are infected with the parasite globally, with 500,000 new cases reported annually. This cross-sectional study was conducted among three tribes of Orang Asli communities in Selangor, Perak and Pahang states of Malaysia. The main objective was to determine the prevalence of and risk factors for giardiasis. Stool samples were collected from 500 individuals aged between 2 and 74 years (males=219, females=281). The samples were examined with formalin-ether sedimentation and trichrome staining techniques. Socioeconomic data were collected through a pre-tested questionnaire. The overall prevalence of giardiasis was 20.0% with the highest prevalence in the Proto-Malays (33.3%) followed by Negritos (20.1%) and Senois (10.4%). The positive cases showed a decrease with increasing age and most of the positive cases were observed in individuals less than 24 years old. Males had significantly higher prevalence than females (χ(2)=5.283, P=0.022). Logistic regression analysis of the overall population studied and the Senoi tribe confirmed that being a child aged less than 15 years, being male, the consumption of raw vegetables and the presence of other family members infected with G. intestinalis were the main risk factors for giardiasis. The presence of other family members infected with G. intestinalis was the only risk factor highlighted in the Proto-Malay and Negrito tribes. Diarrhoea was significantly associated with giardiasis. However, the cause and effect relationship has yet to be determined. Thus, screening family members and treating the infected individuals are the main strategies that should be adopted by the public health authority in combating this infection in Orang Asli communities as well as health education regarding good personal and food hygiene practises.

Fatores associados à ocorrência de parasitoses intestinais em uma população de crianças e adolescentes

OBJETIVOS: Analisar a prevalência de infecções por parasitos intestinais em crianças e adolescentes matriculados em escolas de ensino fundamental no município de São João del-Rei, Minas Gerais, e os fatores associados à infecção. MÉTODOS: Estudo epidemiológico seccional, realizado entre março/2008 e julho/2009. Foram realizados exames coproscópicos por sedimentação espontânea e Kato-Katz em 1.172 escolares. Foram ajustados modelos de regressão logística múltipla para o estudo dos fatores associados às infecções em geral e, separadamente, por helmintos e por protozoários. RESULTADOS: A prevalência de infecções foi de 29%, havendo uma variação de 7 a 83%, respectivamente, entre as escolas de menor e maior ocorrência. A presença de instalação sanitária no domicílio foi associada a uma ocorrência menor de helmintos; o aumento na idade dos escolares associou-se a uma maior ocorrência de protozoários e de parasitos em geral; enquanto a presença de filtro de água e a localização do domicílio em área urbana mostraram-se associadas a uma ocorrência menor dos três desfechos analisados. Em todas as regiões, foi registrado o consumo de medicação preventiva contra helmintos. CONCLUSÕES: Desigualdades nas condições de vida tornaram as prevalências diferenciadas entre as regiões do estudo. O estudo ressalta a necessidade de promover o uso de filtros de água nas residências de áreas endêmicas e de avaliar o consumo preventivo de medicamentos anti-helmínticos na dinâmica e na saúde dos indivíduos. Medidas de controle que levem em conta os fatores descritos devem ser prioritárias em nível de Saúde Pública.

Risk factors for Giardia infection among hospitalized children in Cuba

The risk factors associated with Giardia infection, in children hospitalized in Havana, Cuba, were recently explored. Children aged ≥5 years were more likely to be positive for Giardia infection than the younger children, with an odds ratio (OR) of 3·41 [95% confidence interval (CI) = 1·36-9·69]. The risk factors found to be associated with Giardia infection in univariate analyses were rural residence (OR = 3·01; CI = 1·23-7·35), belonging to a household that did not receive water from an aqueduct (OR = 3·27; CI = 1·21-8·91), drinking unboiled water (OR = 3·64; CI = 2·14-6·26), nail biting (OR = 3·47; CI = 1·97-6·08), eating unwashed vegetables raw (OR = 4·84; CI = 2·33-10·14), and a personal (OR = 3·23; CI = 1·58-6·59) or family history (OR = 3·96; CI = 1·53-10·47) of previous parasitic infection. In multivariate analyses, however, only two (modifiable) risk factors were found to be independently and significantly associated with Giardia infection: nail biting and eating unwashed vegetables raw. It therefore seems that, at least at the individual level, giardiasis-prevention activities in Havana should be focussed on health education to improve personal hygiene and food-related practices. If appropriately managed, the surveillance of drinking water and foodstuffs, for Giardia and other parasites, might also help to reduce the hospitalization of Cuban children.

Comparative insights into the regulation of inflammation: levels and predictors of interleukin 6 and interleukin 10 in young adults in the Philippines

Inflammation is a central part of innate immunity, but its role in anti-pathogen defenses has been overshadowed by recent interest in the contribution of inflammation to a wide range of chronic degenerative diseases. Current research on chronic inflammation is conducted primarily in affluent populations with low levels of infectious disease; comparative research in different ecological settings is needed to advance understandings of the causes and consequences of variation in the regulation of inflammation. This article investigates the levels and predictors of interleukin-6 (IL-6) and interleukin-10 (IL-10)-two cytokines important to the regulation of inflammation-in a large, population-based study in the Philippines. Concentrations of IL-6 and IL-10 were determined in N = 1,569 healthy young adults (20-22 years) in Metro Cebu, Philippines. IL-6 and IL-10 concentrations were positively correlated, and body mass index and symptoms of infectious disease were both associated with higher concentrations of IL-6 and IL-10. Median concentrations of IL-6 (1.0 pg/mL) and IL-10 (7.56 pg/mL) were substantially lower and higher, respectively, than levels reported for other populations based on a systematic review of prior research. This study contributes to a growing body of research in human ecological immunology, and suggests that there may be substantial population differences in the regulation of inflammation that has implications for the association between inflammation and disease.

Risk of Giardia infection for drinking water and bathing in a peri-urban area in Sao Paulo, Brazil

A high incidence of waterborne diseases is observed worldwide and in order to address contamination problems prior to an outbreak, quantitative microbial risk assessment is a useful tool for estimating the risk of infection. The objective of this paper was to assess the probability of Giardia infection from consuming water from shallow wells in a peri-urban area. Giardia has been described as an important waterborne pathogen and reported in several water sources, including ground waters. Sixteen water samples were collected and examined according to the US EPA (1623, 2005). A Monte Carlo method was used to address the potential risk as described by the exponential dose response model. Giardia cysts occurred in 62.5% of the samples (<0.1-36.1 cysts/l). A median risk of 10⁻¹ for the population was estimated and the adult ingestion was the highest risk driver. This study illustrates the vulnerability of shallow well water supply systems in peri-urban areas.

Impact of a citywide sanitation program in Northeast Brazil on intestinal parasites infection in young children

BACKGROUND

Sanitation affects health, especially that of young children. Residents of Salvador, in Northeast Brazil, have had a high prevalence of intestinal parasites. A citywide sanitation intervention started in 1996 aimed to raise the level of sewer coverage from 26% to 80% of households.

OBJECTIVES

We evaluated the impact of this intervention on the prevalence of Ascaris lumbricoides, Trichuris trichuria, and Giardia duodenalis infections in preschool children.

METHODS

The evaluation was composed of two cross-sectional studies (1998 and 2003-2004), each of a sample of 681 and 976 children 1-4 years of age, respectively. Children were sampled from 24 sentinel areas chosen to represent the range of environmental conditions in the study site. Data were collected using an individual/household questionnaire, and an environmental survey was conducted in each area before and after the intervention to assess basic household and neighborhood sanitation conditions. Stool samples were examined for the presence of intestinal parasites. The effect of the intervention was estimated by hierarchical modeling, fitting a sequence of multivariate regression models.

FINDINGS

The prevalence ofA. lumbricoides infection was reduced from 24.4% to 12.0%, T. trichuria from 18.0% to 5.0%, and G. duodenalis from 14.1% to 5.3%. Most of this reduction appeared to be explained by the increased coverage in each neighborhood by the sewage system constructed during the intervention. The key explanatory variable was thus an ecological measure of exposure and not household-based, suggesting that the parasite transmission prevented by the program was mainly in the public (vs. the domestic) domain.

CONCLUSION

This study, using advanced statistical modeling to control for individual and ecological potential confounders, demonstrates the impact on intestinal parasites of sanitation improvements implemented at the scale of a large population.

Could giardiasis be a risk factor for low zinc status in schoolchildren from northwestern Mexico? A cross-sectional study with longitudinal follow-up

Background

Both giardiasis and zinc deficiency are serious health problems worldwide. In Mexico, the prevalence of G. intestinalis was estimated at 32% in 1994. It remains a health problem in northwestern Mexico. Recent surveys (1987, 1995, and 1999) reported zinc deficiency in the Mexican population. The association of giardiasis and malabsorption of micronutrients has been well documented, although the association with zinc remains controversial. This study investigated the association between giardiasis and zinc deficiency in schoolchildren from northwestern Mexico.

Methods

We combined a cross-sectional design with a longitudinal follow-up six months after parasite treatment. The baseline sample consisted of 114 schoolchildren (mean age 8.8 yr) from seven suburban public schools, grouped as Giardia-free (n = 65, 57%) and Giardia-infected (n = 49, 43%). Three stool analyses per child were done using Faust's method. Children with giardiasis received secnidazole. Serum zinc was determined by atomic absorption spectrophotometry. Height and weight were measured. Socioeconomic information was obtained in an oral questionnaire, and daily zinc intake was assessed using 24 hour-recalls. Pearson's correlation and ANCOVA and paired t-test analyses were used to determine the association between giardiasis and zinc status.

Results

Longitudinal analysis demonstrated a significant increase of the mean serum zinc levels in the Giardia-infected group six months after treatment (13.78 vs. 19.24 μmol/L μmol/L; p = 0.001), although no difference was found between the Giardia-free and the Giardia-infected groups (p = 0.86) in the baseline analysis. Z scores for W/A and H/A were lower in the Giardia-infected than in the Giardia-free group (p < 0.05). No difference was observed in the socioeconomic characteristics and mean daily intakes of zinc between the groups (p > 0.05).

Conclusions

Giardiasis may be a risk factor for zinc deficiency in schoolchildren from northwestern Mexico.

Early origins of inflammation: microbial exposures in infancy predict lower levels of C-reactive protein in adulthood

Ecological factors are important determinants of the development and function of anti-pathogen defences. Inflammation is a central part of innate immunity, but the developmental factors that shape the regulation of inflammation are not known. We test the hypothesis that microbial exposures in infancy are associated with high sensitivity C-reactive protein (CRP) in adulthood using prospective data from a birth cohort in the Philippines (n = 1461). Lower birth weight was associated with increased CRP, consistent with a role for inflammation in the widely documented inverse relationship between birth weight and adult cardiovascular diseases. In addition, higher levels of microbial exposure in infancy were associated with lower CRP. These associations were independent of socioeconomic status, measures of current body fat and other health behaviours. We conclude that measures of microbial exposure and nutrition during the pre-natal and early post-natal periods are important predictors of CRP concentration in young adulthood. We speculate that the development of anti-inflammatory regulatory networks in response to early microbial exposure represents plasticity in the development of anti-pathogen defences, and that this process may help explain the low CRP concentrations in this population.

Population differences in associations between C-reactive protein concentration and adiposity: comparison of young adults in the Philippines and the United States

BACKGROUND

Inflammation may be an important mediator of the association between nutrition and cardiovascular diseases, but most studies have been conducted in Western populations with high rates of overweight and obesity and low levels of infectious disease.

OBJECTIVES

This study sought to investigate the predictors of C-reactive protein (CRP) in young adults living in the Philippines and to examine patterns of association with adiposity compared with young adults in the United States.

DESIGN

Maximum likelihood logistic regression models were used to predict elevated high-sensitivity CRP (>3 mg/L) in relation to anthropometric measures of adiposity, symptoms of infectious disease, and proxy measures of pathogen exposure in men and women from the Philippines (n = 1648; age: 20-22 y). Comparative data were drawn from a nationally representative sample in the United States (National Health and Nutrition Examination Survey; n = 616; age: 19-24 y).

RESULTS

Median concentrations of CRP were substantially lower in the Philippines (0.2 mg/L) than in the United States (0.9 mg/L), and the likelihood of elevated CRP was lower in the Philippines than in the United States at the same level of waist circumference or skinfold thickness. In the Philippines, infectious symptoms and pathogen exposure predicted elevated CRP, independent of adiposity.

CONCLUSIONS

Adiposity and infectious exposures are associated with elevated CRP in the Philippines; other populations undergoing comparable lifestyle and dietary changes associated with increasing rates of overweight and obesity are likely experiencing similar double burdens of inflammatory stimuli. Low concentrations of CRP in this Philippine sample raise the question of whether CRP cutoffs based on European or European-American reference populations are appropriate for predicting disease risk in populations undergoing the nutrition transition.

Adiposity and pathogen exposure predict C-reactive protein in Filipino women

Obesity and infectious agents are both sources of inflammatory stimuli that result in increased production of C-reactive protein (CRP). Rates of overweight and obesity are increasing globally, but for many populations, gains in body fat are set against a backdrop of high levels of pathogen exposure. Our primary objective was to evaluate the extent to which adiposity and pathogenicity contribute to a double burden of inflammation in a population currently undergoing the nutrition transition. Measures of adiposity, pathogen exposure, and infectious disease symptoms were evaluated as predictors of high-sensitivity CRP concentration in plasma samples from 1875 women participating in the Cebu Longitudinal Health and Nutrition Survey in the Philippines. Proxy measures of pathogen exposure included household crowding and cleanliness, quality of water source, mode of waste disposal, and fecal exposure. A series of maximum likelihood logistic regression models were used to predict a plasma CRP concentration > 3 mg/L. Waist circumference was the strongest anthropometric predictor of elevated CRP [odds ratio (OR) = 2.29; 95% CI = 2.00, 2.62; P < 0.001]. Presence of infectious disease symptoms (OR = 2.51; 95% CI = 1.84, 3.44; P < 0.001) and level of pathogen exposure (OR = 1.56; 95% CI = 1.15, 2.12; P < 0.01) were also associated with elevated CRP. These associations were independent of socioeconomic status and other health behaviors. Overweight/obesity and infectious exposures are associated with elevated CRP in the Philippines; it is likely that other populations undergoing the nutrition transition are experiencing comparable double burdens of inflammatory stimuli. These results underscore the need for additional research on the contributions of pathogenicity, adiposity, and inflammation to global epidemics of cardiovascular and metabolic diseases.

The SEEDs of two gastrointestinal diseases: socioeconomic, environmental, and demographic factors related to cryptosporidiosis and giardiasis in Massachusetts

OBJECTIVES

We assessed associations between community-level socioeconomic, demographic, and environmental characteristics, and the presence of two potentially waterborne infectious diseases, cryptosporidiosis and giardiasis, as reported to the Massachusetts Department of Public Health.

METHODS

We created a series of maps showing the spatial distribution of cryptosporidiosis and giardiasis in Massachusetts (1993-2002) overall and by age, using logistic regression to analyze associations between community-level characteristics and the presence of at least one reported case of each disease. This analysis was repeated for communities with predominantly private water supplies.

RESULT

After adjusting for population size, higher population density and larger than average household sizes were associated with increased odds of reported cases of cryptosporidiosis. Giardiasis was also associated with high population density, but was not associated with household size. In the elderly, income was positively associated with the presence of giardiasis.

DISCUSSION

These findings suggest that greater population density and larger household sizes may increase the likelihood of protozoan gastrointestinal infection. The results emphasize the necessity to account for distal factors, such as demographic characteristics, that may ultimately play a role in the transmission or reporting of disease.

A hierarchical model for studying risk factors for childhood diarrhoea: a case-control study in a middle-income country

OBJECTIVE

To identify factors associated with diarrhoea occurrence in children in a city in a middle-income country, with high access to water and sanitation.

METHODS

A case-control study in the city of Salvador, north-eastern Brazil was conducted from November 2002 to August 2004. The study population consisted of children presenting at a health facility. A total of 1688 cases of diarrhoea and 1676 controls were selected. Data collection was by a questionnaire and structured observation during home visits. The explanatory variables were grouped according to a conceptual model defined previously. Analysis was done using a hierarchical approach, to provide a more dynamic view of the transmission characteristics of childhood diarrhoea. Non-conditional logistic regression was used, and odds ratio and population-attributable fractions were estimated.

RESULTS

Socioeconomic factors contributed most to determining diarrhoea occurrence, followed by interpersonal contact, while factors related to food preparation, the environment and water and sanitation made a smaller contribution.

CONCLUSION

The findings indicate that the transmission of diarrhoea is influenced by factors from all hierarchical levels, with interpersonal transmission playing a relatively higher role than previously thought. This is compatible with a predominance of viruses and other agents spread by interpersonal routes including Shigella, Giardia and Cryptosporidium. Diarrhoea control strategies in similar settings (middle-income countries in which a large proportion of the population has access to water and sanitation) must give greater emphasis to policies geared towards reducing person-to-person transmission for the prevention of diarrhoea.

Prevalence and associated risk factors for Giardia lamblia infection among children hospitalized for diarrhea in Goiânia, Goiás State, Brazil

The objective of this study was to determine the prevalence and to identify risk factors associated with Giardia lamblia infection in diarrheic children hospitalized for diarrhea in Goiânia, State of Goiás, Brazil. A cross-sectional study was conducted and a comprehensive questionnaire was administered to the child's primary custodian. Fixed effects logistic regression was used to determine the association between infection status for G. lamblia and host, sociodemographic, environmental and zoonotic risk factors. A total of 445 fecal samples were collected and processed by the DFA methodology, and G. lamblia cysts were present in the feces of 44 diarrheic children (9.9%). A variety of factors were found to be associated with giardiasis in these population: age of children (OR, 1.18; 90% CI, 1.0 - 1.36; p = 0.052), number of children in the household (OR 1.45; 90% CI, 1.13 - 1.86; p = 0.015), number of cats in the household (OR, 1.26; 90% CI, 1.03 -1.53; p = 0.059), food hygiene (OR, 2.9; 90% CI, 1.34 - 6.43; p = 0.024), day-care centers attendance (OR, 2.3; 90% CI, 1.20 - 4.36; p = 0.034), living on a rural farm within the past six months prior hospitalization (OR, 5.4; CI 90%, 1.5 - 20.1; p = 0.03) and the number of household adults (OR, 0.59; 90% CI, 0.42 - 0.83; p = 0.012). Such factors appropriately managed may help to reduce the annual incidence of this protozoal infection in the studied population.

Giardia duodenalis infection: risk factors for children living in sub-standard settlements in Brazil

The objective of the present study was to characterize Giardia duodenalis infection among children living in sub-standard settlement areas in the municipality of Juiz de Fora, Minas Gerais State, Brazil. The cross-sectional epidemiological study included 590 children from 1 to 5 years of age. Data were collected from one child per selected family through home interviews with the parent or guardian and parasitological examination of stool samples. Thirty-one putative risk factors concerning family structure, socioeconomic status, and environmental factors were analyzed by multivariate logistic regression. Prevalence of G. duodenalis infection was 18% (106 children). Four potential risk factors were heavily associated with G. duodenalis infection: number of under-five children in the same household, index child's birth order, existence of a bathroom in the home, and drinking water source.

Polymerase chain reaction in the detection of an 'outbreak' of asymptomatic viral infections in a community birth cohort in south India

Asymptomatic enteric infections are important where sequelae or protection from subsequent illness is an outcome measure. The use of reverse transcription-polymerase chain reaction (RT-PCR) to identify asymptomatic enteric infections in a birth cohort followed for rotaviral infections in a south Indian urban slum is reported. Of 1191 non-diarrhoeal samples from 371 children collected in May-June 2003, 22 (1.9%) were positive by ELISA. A total of 147 (40.6%) of 362 samples tested by VP6 RT-PCR were positive. In those samples that could be typed, a high diversity of G types including G1, G2, G4, G8, G9 and G10, and a high proportion (34.4%) of mixed infections were detected. Noroviruses were identified in 6/28 (21.4%) samples tested. The identification of infections undetectable by conventional techniques indicates the importance of the use of sensitive diagnostic techniques in research studies. Asymptomatically infected children may also act as a source of infection for other susceptible hosts.

Role of the employment status and education of mothers in the prevalence of intestinal parasitic infections in Mexican rural schoolchildren

Background

Intestinal parasitic infections are a public health problem in developing countries such as Mexico. As a result, two governmental programmes have been implemented: a) "National Deworming Campaign" and b) "Opportunities" aimed at maternal care. However, both programmes are developed separately and their impact is still unknown. We independently investigated whether a variety of socio-economic factors, including maternal education and employment levels, were associated with intestinal parasite infection in rural school children.

Methods

This cross-sectional study was conducted in 12 rural communities in two Mexican states. The study sites and populations were selected on the basis of the following traits: a) presence of activities by the national administration of albendazole, b) high rates of intestinal parasitism, c) little access to medical examination, and d) a population having less than 2,500 inhabitants. A total of 507 schoolchildren (mean age 8.2 years) were recruited and 1,521 stool samples collected (3 per child). Socio-economic information was obtained by an oral questionnaire. Regression modelling was used to determine the association of socio-economic indicators and intestinal parasitism.

Results

More than half of the schoolchildren showed poliparasitism (52%) and protozoan infections (65%). The prevalence of helminth infections was higher in children from Oaxaca (53%) than in those from Sinaloa (33%) (p < 0.0001). Giardia duodenalis and Hymenolepis nana showed a high prevalence in both states. Ascaris lumbricoides, Trichuris trichiura and Entamoeba hystolitica/dispar showed low prevalence. Children from lower-income families and with unemployed and less educated mothers showed higher risk of intestinal parasitism (odds ratio (OR) 6.0, 95% confidence interval (CI) 1.6–22.6; OR 4.5, 95% CI 2.5–8.2; OR 3.3, 95% CI 1.5–7.4 respectively). Defecation in open areas was also a high risk factor for infection (OR 2.4, 95% CI 2.0–3.0).

Conclusion

Intestinal parasitism remains an important public health problem in Sinaloa (north-western Mexico) and Oaxaca (south-eastern Mexico). Lower income, defecation in open areas, employment status and a lower education level of mothers were the significant factors related to these infections. We conclude that mothers should be involved in health initiatives to control intestinal parasitism in Mexico.

Risk factors and immunological pathways for asthma and other allergic diseases in children: background and methodology of a longitudinal study in a large urban center in Northeastern Brazil (Salvador-SCAALA study)

BACKGROUND

The prevalence of asthma and allergic diseases has increased in industrialised countries, and it is known that rates vary according whether the area is urban or rural and to socio-economic status. Surveys conducted in some urban settings in Latin America found high prevalence rates, only exceeded by the rates observed in industrialised English-speaking countries. It is likely that the marked changes in the environment, life style and living conditions in Latin America are responsible for these observations. The understanding of the epidemiological and immunological changes that underlie the increase in asthma and allergic diseases in Latin America aimed by SCAALA studies in Brazil and Ecuador will be crucial for the identification of novel preventive interventions.

METHODS/DESIGN

The Salvador-SCAALA project described here is a longitudinal study involving children aged 4-11 years living in the city of Salvador, Northeastern Brazil. Data on asthma and allergic diseases (rhinitis and eczema) and potential risk factors will be collected in successive surveys using standardised questionnaire. This will be completed with data on dust collection (to dust mite and endotoxin), skin test to most common allergens, stool examinations to helminth and parasites, blood samples (to infection, total and specific IgE, and immunological makers), formaldehyde, physical inspection to diagnoses of eczema, and anthropometric measures. Data on earlier exposures when these children were 0-3 years old are available from a different project.

DISCUSSION

It is expected that knowledge generated may help identify public health interventions that may enable countries in LA to enjoy the benefits of a "modern" lifestyle while avoiding--or minimising--increases in morbidity caused by asthma and allergies.

The zoonotic transmission of Giardia and Cryptosporidium

The molecular characterisation of Giardia and Cryptosporidium has given rise to a more epidemiological meaningful and robust taxonomy. Importantly, molecular tools are now available for 'typing' isolates of the parasites directly from clinical and environmental samples. As a consequence, information on zoonotic potential has been obtained although the frequency of zoonotic transmission is still poorly understood. Analysis of outbreaks and case-control studies, especially when coupled with genotyping data, is slowly providing information on the public health significance of zoonotic transmission. Such studies support the hypothesis that Cryptosporidium hominis is spread only between humans but that the major reservoir for Cryptosporidium parvum is domestic livestock, predominantly cattle, and that direct contact with infected cattle is a major transmission pathway along with indirect transmission through drinking water. The situation is less clearcut for Giardia duodenalis but the evidence does not, in general, support zoonotic transmission as a major risk for human infections. However, for both parasites there is a need for molecular epidemiological studies to be undertaken in well-defined foci of transmission in order to fully determine the frequency and importance of zoonotic transmission.

Giardia duodenalis infection and wastewater irrigation in Pakistan

The risk of Giardia duodenalis (Giardia) infection in farmers using untreated wastewater in agriculture was investigated in the city of Faisalabad, Pakistan, through a cross-sectional study. The study found a significantly increased risk of (asymptomatic) Giardia infection in wastewater farming households when compared with farming households using regular (non-wastewater) irrigation water (OR 3.3, 95% CI 2.5-4.4). Textile labourers who were employed in the city of Faisalabad but who lived in the same village as the wastewater farmers showed a risk of Giardia infection in between that of wastewater and non-wastewater farming households (OR 2.4, 95% CI 1.9-3.1). This study suggests that exposure to wastewater with high Giardia concentrations carries an increased risk for (asymptomatic) Giardia infection.

Asymptomatic giardiasis and growth in young children; a longitudinal study in Salvador, Brazil

This study sought to assess the effect of giardiasis on growth of young children. In Salvador, northeast Brazil, 597 children initially aged 6 to 45 months were followed for a year in 1998/9, measured anthropometrically thrice, every 6 months, and monitored for diarrhoea prevalence twice weekly. Stool samples were collected and examined during the second round of anthropometry, and infected children were treated 39 days later, on average (S.D. 20 days). For each 6-month interval, the gains in z-scores of infected and uninfected children were compared, after adjustment for potential confounding factors, including longitudinal prevalence of diarrhoea. No significant difference was found for the first interval but in the second, the gain in adjusted height-for-age z-score was 0.09 less in infected than uninfected children, equivalent to a difference in height gain of 0.5 cm. The shortfall in growth was greater in children who remained free of diarrhoea, and was significantly correlated with the proportion of the second interval during which the child had remained untreated. We conclude that Giardia can impede child growth even when asymptomatic, presumably through malabsorption. This finding challenges the view that young children found to have asymptomatic giardiasis in developing countries should not be treated.