Natural history of Giardia lamblia and Cryptosporidium infections in a cohort of Israeli Bedouin infants: a study of a population in transition

A prevalence survey of enteral parasites in preschool children in the Mangochi District of Malawi

Background

Helminthic and protozoan infections are common, particularly in low- or middle-income countries. Although an association between parasite carriage and markers of poor growth have been shown in some studies, systematic reviews have suggested only a modest impact of clearing carriage. The prevalence of these pathogens and the effect that they have on growth in preschool children has never been investigated in Malawi.

Methods

One hundred ninety-three children aged 0–72 months were randomly recruited from rural villages in the Mangochi district of Malawi. Formol-ether concentration was performed on stool and the samples examined with a light microscope. Anthropometric data was taken for each child and the haemoglobin measured with a point of care test.

Results

The mean age of the children was 2 years 4 months. Overall prevalence of intestinal parasite infection was 37.3%. Protozoa were found in 28.5% of children, while helminths were found in 8.8%. The most commonly found organisms were Giardia lambia (12.4%), Entamoeba coli (10.4%) and Hookworm species (3.6%). Stunting was seen in 47.8% of children, 12.9% were underweight and 5.0% were wasted. No significant association was found between markers of poor growth and infection with any intestinal parasite.

Conclusions

We found that prevalence of helminth infection was low in preschool children living in the Mangochi district compared to international standards. However a significant proportion of the preschool population are infected with protozoa, particularly Giardia lambia. In this cohort, despite a significant prevalence of stunting, helminth infection was not significantly associated with any markers of poor growth. The significance of protozoal carriage and contribution to growth restriction in this context creates further avenues for future research.

Molecular typing of Cryptosporidium in Israel

Cryptosporidium is a protozoan parasite associated with gastrointestinal illness. In immune-compromised individuals, the infection may become life-threatening. Cryptosporidiosis is a mandatory-reported disease but little was known about its prevalence and associated morbidity in Israel. Currently, laboratory diagnosis is based on microscopy or copro-antigen tests and the disease is underreported. Molecular assays, which are more sensitive and specific, are now increasingly used for identification and screening. Here, the molecular epidemiology of cryptosporidiosis is explored for the first time. Samples from 33 patients infected during an outbreak of 146 laboratory confirmed cases that occurred in Haifa and Western Galilee in 2015 were genotyped, as well as samples from 36 patients sporadically infected during 2014–2018 in different regions. The results suggest that Cryptosporidium subtypes found in Israel are more similar to those reported in the neighboring countries Jordan and Egypt than in European countries. C. hominis was the predominant species in the center and the north of Israel, implicating human-to-human transmission. C. hominis IeA11G3T3 was the most prevalent subtype contributing to morbidity.

What is Known About Health and Morbidity in the Pediatric Population of Muslim Bedouins in Southern Israel: A Descriptive Review of the Literature from the Past Two Decades

The Bedouins comprise one of the ethnic groups in Israeli society. They are Muslims, most of who live in the Negev desert region of southern Israel and live by their unique traditions and customs. At the present they are going through a period of "society in transition", a unique condition that has ramifications for health and morbidity. In recent years the number of publications on the health of Bedouins in the Negev has increased. Recognition of unique socio-economic features, characteristics of health and diseases can help the medical team treat various health problems in this population as well as other populations with similar characteristics. In the present paper we survey and discuss publications on the health of Bedouin children over the past 20 years.

Natural History of Cryptosporidiosis in a Birth Cohort in Southern India

In an Indian birth cohort, we demonstrate a high and early burden of cryptosporidiosis by polymerase chain reaction and serology. Reinfection was common and infections clustered in a subset of children. Prior infection provided some protection against subsequent infection, but not disease.

Background.

Cryptosporidium is a leading cause of moderate to severe childhood diarrhea in resource-poor settings. Understanding the natural history of cryptosporidiosis and the correlates of protection are essential to develop effective and sustainable approaches to disease control and prevention.

Methods.

Children (N = 497) were recruited at birth in semiurban slums in Vellore, India, and followed for 3 years with twice-weekly home visits. Stool samples were collected every 2 weeks and during diarrheal episodes were tested for Cryptosporidium species by polymerase chain reaction (PCR). Serum samples obtained every 6 months were evaluated for seroconversion, defined as a 4-fold increase in immunoglobulin G directed against Cryptosporidium gp15 and/or Cp23 antigens between consecutive sera.

Results.

Of 410 children completing follow-up, 397 (97%) acquired cryptosporidiosis by 3 years of age. PCR identified 1053 episodes of cryptosporidiosis, with an overall incidence of 0.86 infections per child-year by stool and serology. The median age for the first infection was 9 (interquartile range, 4–17) months, indicating early exposure. Although infections were mainly asymptomatic (693 [66%]), Cryptosporidium was identified in 9.4% of diarrheal episodes. The proportion of reinfected children was high (81%) and there was clustering of asymptomatic and symptomatic infections (P < .0001 for both). Protection against infection increased with the order of infection but was only 69% after 4 infections. Cryptosporidium hominis (73.3%) was the predominant Cryptosporidium species, and there was no species-specific protection.

Conclusions.

There is a high burden of endemic cryptosporidiosis in southern India. Clustering of infection is suggestive of host susceptibility. Multiple reinfections conferred some protection against subsequent infection.

Advances in understanding Giardia: determinants and mechanisms of chronic sequelae

Giardia lamblia is a flagellated protozoan that is the most common cause of intestinal parasitic infection in children living in resource-limited settings. The pathogenicity of Giardia has been debated since the parasite was first identified, and clinical outcomes vary across studies. Among recent perplexing findings are diametrically opposed associations between Giardia and acute versus persistent diarrhea and a poorly understood potential for long-term sequelae, including impaired child growth and cognitive development. The mechanisms driving these protean clinical outcomes remain elusive, but recent advances suggest that variability in Giardia strains, host nutritional status, the composition of microbiota, co-infecting enteropathogens, host genetically determined mucosal immune responses, and immune modulation by Giardia are all relevant factors influencing disease manifestations after Giardia infection.

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.

Burden of diarrhea, hospitalization and mortality due to cryptosporidial infections in Indian children

BACKGROUND

Cryptosporidium spp. is a common, but under-reported cause of childhood diarrhea throughout the world, especially in developing countries. A comprehensive estimate of the burden of cryptosporidiosis in resource-poor settings is not available.

METHODOLOGY/PRINCIPAL FINDINGS

We used published and unpublished studies to estimate the burden of diarrhea, hospitalization and mortality due to cryptosporidial infections in Indian children. Our estimates suggest that annually, one in every 6-11 children <2 years of age will have an episode of cryptosporidial diarrhea, 1 in every 169-633 children will be hospitalized and 1 in every 2890-7247 children will die due to cryptosporidiosis. Since there are approximately 42 million children <2 years of age in India, it is estimated that Cryptosporidium results in 3.9-7.1 million diarrheal episodes, 66.4-249.0 thousand hospitalizations, and 5.8-14.6 thousand deaths each year.

CONCLUSIONS/SIGNIFICANCE

The findings of this study suggest a high burden of cryptosporidiosis among children <2 years of age in India and makes a compelling case for further research on transmission and prevention modalities of Cryptosporidium spp. in India and other developing countries.

Can Giardia lamblia infection lower the risk of acute diarrhea among preschool children?

There are inconsistent findings concerning the role of Giardia lamblia in pediatric diarrhea. A prospective cohort study of the incidence of acute diarrhea among Israeli Arab preschool children offered the opportunity to examine the association between G. lamblia infection (at baseline) and subsequent diarrhea. Following baseline screening by light microscopy for the presence of Giardia in their stools, a cohort was assembled of 142 children who were followed between October 2003 and August 2004 for the incidence of diarrhea. Surveillance was performed through maternal interviews. At baseline, 21 children tested Giardia-positive. During the prospective surveillance, acute diarrhea occurred less often among Giardia-positive children (9.5%) than among children who were not infected with Giardia (26.5%). G. lamblia infection was associated with lower risk of acute diarrhea; adjusted odds ratio of 0.18 (95% confidence interval 0.04-0.93) (p = 0.041). This prospective study provides additional evidence that Giardia may lower the risk of subsequent acute diarrhea among preschool children.

Rotavirus seasonality and age effects in a birth cohort study of southern India

INTRODUCTION

Understanding the temporal patterns in disease occurrence is valuable for formulating effective disease preventive programs. Cohort studies present a unique opportunity to explore complex interactions associated with emergence of seasonal patterns of infectious diseases.

METHODS

We used data from 452 children participating in a birth cohort study to assess the seasonal patterns of rotavirus diarrhea by creating a weekly time series of rotavirus incidence and fitting a Poisson harmonic regression with biannual peaks. Age and cohort effects were adjusted for by including the weekly counts of number of children in the study and the median age of cohort in a given week. Weekly average temperature, humidity and an interaction term to reflect the joint effect of temperature and humidity were included to consider the effects of meteorological variables.

RESULTS

In the overall rotavirus time series, two significant peaks within a single year were observed--one in winter and the other in summer. The effect of age was found to be the most significant contributor for rotavirus incidence, showing a strong negative association. Seasonality remained a significant factor, even after adjusting for meteorological parameters, and the age and cohort effects.

CONCLUSIONS

The methodology for assessing seasonality in cohort studies is not yet developed. This is the first attempt to explore seasonal patterns in a cohort study with a dynamic denominator and rapidly changing immune response on individual and group levels, and provides a highly promising approach for a better understanding of the seasonal patterns of infectious diseases, tracking emergence of pathogenic strains and evaluating the efficacy of intervention programs.

Cryptosporidiosis among children in an endemic semiurban community in southern India: does a protected drinking water source decrease infection?

BACKGROUND

A quasi-experimental study was conducted to determine whether or not a protected water supply (bottled drinking water) could prevent or delay cryptosporidial infections among children residing in an endemic community.

METHODS

A total of 176 children residing in a semiurban slum area in southern India were enrolled preweaning and received either bottled (n = 90) or municipal (n = 86) drinking water based on residence in specific streets. Weekly surveillance visits were conducted until children reached their second birthday. Stool samples were collected every month and during diarrheal episodes, and were tested for the presence of Cryptosporidium species by polymerase chain reaction. Differences in the incidence of cryptosporidiosis between bottled and municipal water groups were compared using Poisson survival models, and a propensity score model was developed to adjust for the effect of potential confounders.

RESULTS

A total of 186 episodes of cryptosporidiosis, mostly asymptomatic, were observed in 118 (67%) children during the follow-up period at a rate of 0.59 episodes per child-year. Diarrhea associated with Cryptosporidium species tended to be longer in duration and more severe. Stunting at 6 months was associated with a higher risk of cryptosporidiosis (rate ratio [RR] = 1.40; 95% confidence interval [CI], 1.03-1.91). A higher gastrointestinal disease burden was also seen in children with cryptosporidiosis. Drinking bottled water was not associated with a reduced risk of cryptosporidiosis (adjusted RR = 0.86; 95% CI, .60-1.23).

CONCLUSIONS

This study documented a high burden of cryptosporidiosis among children in an endemic Indian slum community. The lack of association between drinking bottled water and cryptosporidiosis suggests possible spread from asymptomatically infected individuals involving multiple transmission pathways.

A systematic review and meta-analysis of the association between Giardia lamblia and endemic pediatric diarrhea in developing countries

We performed a systematic literature review and meta-analysis examining the association between diarrhea in young children in nonindustrialized settings and Giardia lamblia infection. Eligible were case/control and longitudinal studies that defined the outcome as acute or persistent (>14 days) diarrhea, adjusted for confounders and lasting for at least 1 year. Data on G. lamblia detection (mainly in stools) from diarrhea patients and controls without diarrhea were abstracted. Random effects model meta-analysis obtained pooled odds ratios (ORs) and 95% confidence intervals (CIs). Twelve nonindustrialized-setting acute pediatric diarrhea studies met the meta-analysis inclusion criteria. Random-effects model meta-analysis of combined results (9774 acute diarrhea cases and 8766 controls) yielded a pooled OR of 0.60 (95% CI, .38-.94; P = .03), indicating that G. lamblia was not associated with acute diarrhea. However, limited data suggest that initial Giardia infections in early infancy may be positively associated with diarrhea. Meta-analysis of 5 persistent diarrhea studies showed a pooled OR of 3.18 (95% CI, 1.50-6.76; P < .001), positively linking Giardia with that syndrome. The well-powered Global Enteric Multicenter Study (GEMS) is prospectively addressing the association between G. lamblia infection and diarrhea in children in developing countries.

Effect of cryptosporidial and giardial diarrhoea on social maturity, intelligence and physical growth in children in a semi-urban slum in south India

BACKGROUND

Early childhood diarrhoea is a major cause of infant morbidity and mortality in developing countries. Recurrent and persistent diarrhoea affect growth and cognition in children as young as 6 years.

OBJECTIVES

To evaluate the effect of early childhood cryptosporidial and giardial diarrhoea on growth and development in children in a semi-urban slum in India. This is the first report of such assessment at 3 years of age.

METHODS

This study was undertaken on 116 children who were part of an ongoing birth cohort study (n=452) of rotaviral and cryptosporidial diarrhoea between June and December 2005. Social quotients (SQ) assessed by the Vineland Social Maturity Scale, intelligence quotients (IQ) assessed by the Seguin Form Board Test, physical growth parameters and sociodemographic data in 84 children with a history of cryptosporidial or giardial diarrhoea were compared with those of 32 without diarrhoea.

RESULTS

Children with a past history of giardial diarrhoea showed a trend towards lower SQ (p=0.09) and had significantly lower IQ (p=0.04) and increased wasting (p=0.04). Cryptosporidial diarrhoea was not associated with poor IQ, SQ or physical growth.

CONCLUSION

This study demonstrates the long-term effect of protozoan diarrhoea, especially that caused by giardia, on both intelligence and physical growth in Indian children as early as 3 years of age and re-inforces the need for early detection and prevention of early childhood protozoan diarrhoea.

Protection against diarrhea associated with Giardia intestinalis Is lost with multi-nutrient supplementation: a study in Tanzanian children

BACKGROUND

Asymptomatic carriage of Giardia intestinalis is highly prevalent among children in developing countries, and evidence regarding its role as a diarrhea-causing agent in these settings is controversial. Impaired linear growth and cognition have been associated with giardiasis, presumably mediated by malabsorption of nutrients. In a prospective cohort study, we aim to compare diarrhea rates in pre-school children with and without Giardia infection. Because the study was conducted in the context of an intervention trial assessing the effects of multi-nutrients on morbidity, we also assessed how supplementation influenced the relationship between Giardia and diarrhoea rates, and to what extent Giardia modifies the intervention effect on nutritional status.

METHODS AND FINDINGS

Data were collected in the context of a randomized placebo-controlled efficacy trial with 2×2 factorial design assessing the effects of zinc and/or multi-micronutrients on morbidity (n=612; height-for-age z-score <-1.5 SD). Outcomes measures were episodes of diarrhea (any reported, or with ≥3 stools in the last 24 h) and fever without localizing signs, as detected with health-facility based surveillance. Giardia was detected in stool by enzyme-linked immunosorbent assay. Among children who did not receive multi-nutrients, asymptomatic Giardia infection at baseline was associated with a substantial reduction in the rate of diarrhea (HR 0.32; 0.15-0.66) and fever without localizing signs (HR 0.56; 0.36-0.87), whereas no such effect was observed among children who received multi-nutrients (p-values for interaction 0.03 for both outcomes). This interaction was independent of age, HAZ-scores and distance to the research dispensary. There was no evidence that Giardia modified the intervention effect on nutritional status.

CONCLUSION

Although causality of the Giardia-associated reduction in morbidity cannot be established, multi-nutrient supplementation results in a loss of this protection and thus seems to influence the proliferation or virulence of Giardia or associated intestinal pathogens.

Protection against diarrhea associated with Giardia intestinalis Is lost with multi-nutrient supplementation: a study in Tanzanian children

Background

Asymptomatic carriage of Giardia intestinalis is highly prevalent among children in developing countries, and evidence regarding its role as a diarrhea-causing agent in these settings is controversial. Impaired linear growth and cognition have been associated with giardiasis, presumably mediated by malabsorption of nutrients. In a prospective cohort study, we aim to compare diarrhea rates in pre-school children with and without Giardia infection. Because the study was conducted in the context of an intervention trial assessing the effects of multi-nutrients on morbidity, we also assessed how supplementation influenced the relationship between Giardia and diarrhoea rates, and to what extent Giardia modifies the intervention effect on nutritional status.

Methods and Findings

Data were collected in the context of a randomized placebo-controlled efficacy trial with 2×2 factorial design assessing the effects of zinc and/or multi-micronutrients on morbidity (n = 612; height-for-age z-score <−1.5 SD). Outcomes measures were episodes of diarrhea (any reported, or with ≥3 stools in the last 24 h) and fever without localizing signs, as detected with health-facility based surveillance. Giardia was detected in stool by enzyme-linked immunosorbent assay. Among children who did not receive multi-nutrients, asymptomatic Giardia infection at baseline was associated with a substantial reduction in the rate of diarrhea (HR 0.32; 0.15–0.66) and fever without localizing signs (HR 0.56; 0.36–0.87), whereas no such effect was observed among children who received multi-nutrients (p-values for interaction 0.03 for both outcomes). This interaction was independent of age, HAZ-scores and distance to the research dispensary. There was no evidence that Giardia modified the intervention effect on nutritional status.

Conclusion

Although causality of the Giardia-associated reduction in morbidity cannot be established, multi-nutrient supplementation results in a loss of this protection and thus seems to influence the proliferation or virulence of Giardia or associated intestinal pathogens.

Giardia intestinalis is a well-known cause of diarrhea in industrialized countries. In children in developing countries, asymptomatic infections are common and their role as cause of diarrhea has been questioned. In a cohort of rural Tanzanian pre-school children, we assessed the association between the presence of Giardia at baseline and subsequent diarrhea risk. The study was conducted in the context of a randomised trial assessing the effect of supplementation with zinc and other micro-nutrients on malaria, and half of the children daily received a multi-nutrient supplement. Surprisingly, we found that the presence of Giardia at baseline was associated with a substantial reduction in diarrhea risk. Multivariate statistical analysis showed that this protection could not be explained by differences in age or walking distance to the dispensary between children with and without Giardia. Because we cannot exclude that children differed in other (unmeasured) characteristics, we cannot draw firm conclusions about the causality of the observed association, but our findings support the view that the parasite is not an important cause of diarrhea in highly endemic settings. Striking was that the Giardia-associated protection was lost when children received multi-nutrients. Our data do not provide information about the mechanisms involved, but suggest that multi-nutrients may influence the compositionor pathogenicity of intestinal biota.

Hospitalization of Cuban children for giardiasis: a retrospective study in a paediatric hospital in Havana

The medical records of the 185 children who, in 2007, were admitted to the Academic Paediatric Hospital 'Centro Habana', in the Cuban capital of Havana, because of giardiasis were analysed retrospectively. A standardized form was used to collect data on the socio-demographic characteristics, clinical features, laboratory diagnosis, treatment and length of stay of each child. Information on the 15 children who had incomplete medical records was excluded from the data analysis. Of the remaining 170 children, 85 (50·0%) were aged 1-4 years, 97 (57·1%) were male, and 106 (62·4%), 92 (54·1%) and 69 (40·6%) had presented with diarrhoea, vomiting, and/or abdominal pain, respectively. Most (91·2%) of the cases had been diagnosed by the microscopical examination of a duodenal aspirate, and the drugs that had been most used frequently were quinacrine and tinidazole, which had been given to 72 (42·4%) and 62 (36·5%) of the cases, respectively. The mean length of hospital stay was 4·9 days. Such information on the clinical characteristics of giardiasis among children living in an endemic area may be valuable to paediatricians and public-health officials who wish to screen for the disease.

Symptomatic and asymptomatic Cryptosporidium infections in children in a semi-urban slum community in southern India

Cryptosporidium is a leading cause of childhood diarrhea in developing countries. We investigated symptomatic and asymptomatic cryptosporidiosis in 20 children less than two years of age in a semi-urban slum in southern India. All surveillance (conducted every two weeks) and diarrheal samples from 20 children (n = 1,036) with cryptosporidial diarrhea previously identified by stool microscopy were tested by polymerase chain reaction-restriction fragment length polymorphism for species and subgenotype determination. Thirty-five episodes of cryptosporidiosis were identified in 20 children, of which 25 were diarrheal. Fifteen episodes were associated with prolonged oocyst shedding. Multiple episodes of cryptosporidiosis occurred in 40% of the children. Most infections were with C. hominis, subtype Ia. Children with multiple infections had significantly lower weight-for-age and height-for-age Z scores at 24 months but had scores comparable with children with a single episode by 36 months. Multiple symptomatic Cryptosporidium infections associated with prolonged oocyst shedding occur frequently in this disease-endemic area and may contribute to the long-term effects of cryptosporidiosis on physical growth in these children.

Multisite study of cryptosporidiosis in children with diarrhea in India

Cryptosporidium spp., a common cause of diarrhea in children, were investigated in the first multisite study in India. Diarrheal stools from hospitalized children aged <5 years from Delhi, Trichy, and Vellore were analyzed by microscopy, PCR-restriction fragment length polymorphism (RFLP), and/or sequencing at the small-subunit (SSU) rRNA and Cpgp40/15 loci for species determination and subgenotyping, respectively. Seventy of 2,579 (2.7%) children, 75% of whom were <2 years old, had cryptosporidial diarrhea as determined by microscopy. Genotyping and subgenotyping showed that Cryptosporidium hominis was the most commonly identified species (59/67 children), and subgenotypes Ie, Ia, Ib, and Id were common in all centers. A novel C. parvum subgenotype, IIn, was identified in Vellore. Meteorological analysis revealed a higher rate of cryptosporidial positivity during hotter and drier weather in Delhi.

Risk factors for the initial symptomatic giardia infection in a cohort of young Arab-Bedouin children

BACKGROUND

Giardiasis is a common protozoan infection with clinical manifestations in children ranging from asymptomatic carriage to persistent diarrhoea with malabsorption. It can lead to growth and developmental retardation.

AIM

The study evaluated risk factors for the initial symptomatic giardiasis (SG) episode among Arab-Bedouin children in Israel.

METHODS

A community-based, prospective cohort study was conducted in Rahat, a Bedouin township in southern Israel. Infants (n=238) were followed by weekly visits from birth to age 18 months. Giardia infection was identified by antigen detection in faecal specimens.

RESULTS

Approximately 26% of children experienced one or more SG episode. Mean (SD) age for first SG episode was 12.3 (3.3) months, with 95% of episodes occurring in children >6 months of age. Risk for the first SG in children >6 months of age was associated with it being spring or summer [odds ratio (OR) 6.16, p<0.001], exposure to livestock (OR 4.89, p=0.002) and prior infection with entero-aggregative Escherichia coli (EAEC) (OR 1.12 for each additional percentage in stool prevalence, p=0.02). Weight-for-age Z-scores at age 6 months were inversely related to SG risk (OR 0.62 for each unit increase in Z-score, p=0.029).

CONCLUSIONS

Giardiasis is an important cause of diarrhoea in Bedouin children. Increased risk of SG in spring/summer might be linked to environmental conditions or seasonal dietary practices which increase virulence or transmission. SG in those exposed to livestock suggests that there are zoonotic risk factors or that hygiene is a causal factor. The association between EAEC infection and SG warrants further investigation.

Lack of an adverse effect of Giardia intestinalis infection on the health of Peruvian children

Giardia intestinalis is a common gastrointestinal protozoan worldwide, but its effects on childhood growth in developing countries are not clearly understood. The authors aimed to describe its effects on child growth. They followed 220 Peruvian children daily for diarrhea, weekly for stool samples, and monthly for anthropometry. The authors modeled the effect of nutritional status on the risk of Giardia infection and the risk of diarrhea attributable to Giardia using negative binomial regression. They modeled the effects of Giardia infection on growth using linear regression, with 85% of children becoming infected with Giardia and 87% of these becoming reinfected. In multivariable analysis, the risk of Giardia infection did not vary with weight for age (relative risk = 1.00, 95% confidence interval: 0.89, 1.12) or height for age (relative risk = 0.92, 95% confidence interval: 0.82, 1.04). Giardiasis did not affect growth at 1 or 2 months following the first infection at any age interval. The longitudinal prevalence of Giardia between 6 and 24 months of age was not associated with height gain in that interval (p = 0.981). Giardia was not associated with an increased risk of diarrhea at any age interval. Study results question the importance of Giardia as a childhood pathogen in developing countries where giardiasis is hyperendemic.

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.

Socioeconomic correlates of antibody levels to enteric pathogens among Israeli adolescents

We examined the association between socioeconomic status and the level of serum antibodies to selected faeco-orally transmitted pathogens among Israeli adolescents. Random samples of eighty volunteers aged 12-15 years from high (HSL), medium (MSL) and low (LSL) standard of living towns were included in the study. Serum samples were examined by radioimmunoassay for HAV and by in-house-developed ELISA systems for IgA and IgG antibody levels against Shigella sonnei, S. flexneri, E. coli O157:H7 lipopolysacchride and Cryptosporidium parvum antigens. Seropositivity to HAV was highest (98.8%) in the LSL towns and lowest (25%) in the HSL towns, showing a statistically significant linear trend. Antibody levels to the other enteropathogens had gender variation, with higher titres in females. Significantly lower titres in the HSL towns were found for: IgA anti-S. sonnei in females (P<0.001); IgG anti-S. sonnei in females (P=0.024) and males (P=0.033); IgG anti-S. flexneri in females (P=0.016). Inverse linear association with socioeconomic status was found for IgA anti-C. parvum in females (P<0.001); IgA anti-E. coli O157:H7 in females (P<0.001) and males (P=0.024). A statistically significant association between HAV seropositivity and higher titres of IgA anti-S. sonnei and E. coli O157:H7 was shown. In conclusion, exposure to enteropathogens transmitted via the faecal-oral route in communities of lower socioeconomic status is reflected in a higher prevalence of lifelong lasting antibodies to HAV, and higher levels of antibodies to bacterial and protozoan enteropathogens. Among females, the levels of specific serum antibodies are higher and more strongly associated with low socioeconomic status.

An updated review on Cryptosporidium and Giardia

Cryptosporidium and Giardia are two of the most commonly occurring enteric protozoans. They are responsible for diarrheal diseases that may lead to nutritional deficiencies and significant morbidity and mortality, especially among children in developing countries and patients who have immune defects. Both are difficult to diagnose with microscopic techniques. This article provides an updated review of the epidemiology, pathogenesis, clinical manifestations, and treatment of Cryptosporidium and Giardia.

[General malaise and diarrhea as the main manifestations of Giardia lamblia infection]

Giardia lamblia is a ubiquitous intestinal protozoan. Transmission, which is fecal-oral, occurs after cyst ingestion, excystation and enterocyte adhesion. Symptoms include diarrhea, abdominal pain and other less frequent manifestations such as nausea, anorexia and weight loss. Enzyme immunoassay and direct fluorescent-antibody assay for antigen detection in stool samples, and small intestine biopsy provide the best diagnostic sensitivity. When an infection is suspected, duodenal biopsy should be carried out, even though endoscopic appearance may be normal. The most effective drugs in the treatment of this infection are metronidazole and tinidazole. We report a case of G. lamblia infection. The patient reported a clinical history of 4 months' duration with general malaise and diarrhea for the previous month. This form of presentation is rarely found in adults with this parasitosis. The diagnosis was based on the results of duodenal biopsy. The patient showed satisfactory response to treatment with metronidazole.

Effects of giardiasis on school success, weight and height indices of primary school children in Turkey

BACKGROUND

Giardia intestinalis, the most common parasite in the world, causes several adverse effects on school children, with the prevalence rate ranging between 7.3% and 28% (mean 13.8%) in Turkey. The aim of the present study was to investigate possible adverse effects of G. intestinalis on success at school, and the mean weight and height of primary school children in Sivas, Turkey.

METHODS

Five primary schools from central Sivas, Turkey, had a number of students from different socioeconomic conditions and regions. The stool specimens were examined by light microscopy for giardiasis using saline-Lugol and/or zinc sulfate flotation method. Three groups in the present study include the symptomatic giardiasis group (SG), which included children with giardiasis along with abdominal pain and/or diarrhea, the asymptomatic giardiasis group (ASG) without any symptom and the non-parasitic (NPG) group without any parasites.

RESULTS

While 599 (34.6%) out of 1730 children were parasitic, 192 (11.1%) had only G. intestinalis. Ninety-eight (5.7%) of 192 were SG (with diarrhea and/or abdominal pain and 94 (5.4%) were ASG. The weights and heights were lower in the children with giardiasis than the children without any parasite. There was a significant difference between the giardiasis group and NPG when the numbers of persons living in the house were compared. While there were no significant difference between the giardiasis group and NPG when the sexes were compared, success at school and economical levels were found to be significantly different between these groups.

CONCLUSION

There was a higher prevalence of giardiasis in primary school children and their physical and mental conditions were affected adversely. Giardia infections in particular have adverse effects on success at school.

Subclinical vitamin A deficiency in Israeli-Bedouin toddlers

OBJECTIVE

This study was designed to estimate the prevalence of and evaluate risk factors for subclinical vitamin A deficiency in Arab-Bedouin children at age 18 months, followed from birth.

DESIGN

Community-based, prospective, cohort study conducted in Rahat, a large Arab-Bedouin township, located near the city of Beer Sheva in the Negev region of southern Israel.

SUBJECTS

Healthy Bedouin infants (n=117) from the township, born at Soroka University Medical Center (SUMC) in Beer Sheva, were randomly recruited at birth. Enrollment was restricted to well infants born weighing >2500 g at birth.

RESULTS

More than 15% of the children had serum retinol concentrations below 0.7 micromol/l. Male sex (odds ratio (OR) 4.17 [1.14-15.32], P=0.031), stunting at age 12 months (OR 10.09 [2.00-50.97], P=0.05) and warm season at age 18 months (OR 6.20 [1.36-28.28], P=0.018) were associated with vitamin A deficiency. Maternal education decreased the risk of vitamin A deficiency (OR 0.81 [0.68-0.95], P=0.011).

CONCLUSIONS

Study results indicate a significant vitamin A deficiency problem among Bedouin children. Deficiency may be prevented by increasing dietary intake of vitamin A, especially during the warm season. Other interventions include preventing and controlling diarrheal diseases in order to avert nutritional stunting, and providing nutritional education to women of childbearing age.

SPONSORSHIP

This study received financial support from the National Institute of Allergy and Infectious Diseases (AI-26497), the US-Israel Bi-national Science Foundation (BSF 90-00257), and the National Academy of Sciences/Institute of Medicine (AID/ANE 0158-G-SS-9035-00).

Randomized clinical study of nitazoxanide compared to metronidazole in the treatment of symptomatic giardiasis in children from Northern Peru

BACKGROUND

Enteric infection by Giardia intestinalis is a common cause of diarrhoea world-wide and a significant cause of morbidity in children.

AIM

To compare the efficacy and safety of nitazoxanide and metronidazole in the treatment of diarrhoea caused by G. intestinalis in children.

METHODS

A total of 110 children presenting with diarrhoea caused by G. intestinalis were randomized to treatment with either a 3-day course of nitazoxanide (100 mg b.d., age range 2-3 years; 200 mg b.d., age range 4-11 years) or a 5-day course of metronidazole (125 mg b.d., age range 2-5 years; 250 mg b.d., age range 6-11 years). The patients were followed-up for a determination of clinical response 7 days after the initiation of treatment, and two subsequent stool samples were collected for parasitological examination.

RESULTS

Diarrhoea had resolved in 47 children out of 55 (85%) in the nitazoxanide treatment group before the day 7 follow-up visit, compared to 44 out of 55 (80%) for metronidazole. Diarrhoea resolved within 4 days in most cases. Only mild, transient adverse events were reported.

CONCLUSIONS

A 3-day course of nitazoxanide suspension is as efficacious as a standard 5-day course of metronidazole suspension in treating giardiasis in children.

A longitudinal study of Giardia lamblia infection in north-east Brazilian children

OBJECTIVE

To evaluate the epidemiology of Giardia lamblia infection, investigate factors which might be associated with clinical manifestations and recurrence, and examine the role of copathogens in disease course.

METHODS

Prospective 4-year cohort study of children born in an urban slum in north-eastern Brazil.

RESULTS

Of 157 children followed for > or = 3 months, 43 (27.4%) were infected with Giardia. The organism was identified in 8.8% of all stool specimens, and although found with similar frequency in non-diarrhoeal (7.4%) and diarrhoeal stools (9.7%), was more common in children with persistent (20.6%) than acute diarrhoea (7.6%, P=0.002). Recurrent or relapsing infections were common (46%). Children with symptomatic infections had significantly lower weight-for-age and height-for-age than asymptomatic children. Copathogens were not associated with disease course. CONCLUSION With its protean clinical manifestations, Giardia may be associated with substantial morbidity amongst children in Brazil.

Descriptive analysis of endemic cryptosporidiosis cases reported in Ontario, 1996-1997

Endemic cryptosporidiosis in Ontario was studied using notifiable disease data from the Ontario Ministry of Health for the years 1996-1997 inclusive. For this study period, 451 endemic cases were identified, corresponding to a provincial mean annual age- and sex-adjusted incidence rate of 2.13 cases per 100,000. Children under five years of age had the highest incidence of disease. Males had a higher incidence than females, except for those 15-19 years of age. Five percent of cases were reported as HIV-positive or having AIDS. The proportion of cases occurring between July and November inclusive (63%) was significantly higher than expected (42%) assuming no seasonal variation (p < 0.01). The proportion of rural cases observed (29%) was significantly higher than expected (17%) based on the Ontario population (p < 0.01). Travel to or prior residence in an endemic area was identified in 22% of the cases where a risk setting was reported (n = 265).

Cryptosporidium infection in Bedouin infants assessed by prospective evaluation of anticryptosporidial antibodies and stool examination

An enzyme-linked immunosorbent assay system using oocyst lysate as antigen was used to detect serum- specific antibody responses to Cryptosporidium parvum between 1989 and 1994 in consecutive sera obtained at birth, and at the age of 6, 12, and 23 months, from 52 infants living in a Bedouin town located in the south of Israel. The serologic tests revealed high levels of immunoglobulin G anti-Cryptosporidium at birth that dropped significantly by the age of 6 months and then rose continuously to a geometric mean titer of 481 at age 23 months. The serum immunoglobulin M Cryptosporidium antibodies rose continuously from nearly undetectable levels at birth to a geometric mean titer of 471 (157-fold increase) at age 23 months. All the subjects already showed at 6 months a significant rise in immunoglobulin M. A significant rise in immunoglobulin A titers was detected in 48% and 91% of subjects at 6 and 23 months, respectively. By monthly surveillance, microscopy using the modified Ziehl-Neelsen method and confirmed by indirect immunofluorescence assay detected Cryptosporidium antigens in only 11% at age 6 months and 48% at age 23 months. The extent of exposure to Cryptosporidium immediately after birth as detected by serology is much higher than that predicted by frequent prospective assessment of stool samples.

Drug targets and mechanisms of resistance in the anaerobic protozoa

The anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent, and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined. Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently been investigated using laboratory-induced resistant isolates. Instead of downregulation of the pyruvate:ferredoxin oxidoreductase and ferredoxin pathway as seen in G. duodenalis and T. vaginalis, E. histolytica induces oxidative stress mechanisms, including superoxide dismutase and peroxiredoxin. The review examines the value of investigating both clinical and laboratory-induced syngeneic drug-resistant isolates and dissection of the complementary data obtained. Comparison of resistance mechanisms in anaerobic bacteria and the parasitic protozoa is discussed as well as the value of studies of the epidemiology of resistance.

Giardia lamblia carriage in Israeli Bedouin infants: risk factors and consequences

Giardiasis is a common protozoan infection, with varying clinical manifestations. We investigated the associations between Giardia lamblia carriage and environmental, family, illness, and growth characteristics. Bedouin infants (n=234) were followed from birth to age 18-23 months. At monthly home visits, stool samples were obtained, history of illness was determined, and an environmental assessment was done. The comparisons presented are between 4 groups defined by length of carriage of G. lamblia. Study children had a mean+/-SD of 4.1+/-2.9 diarrhea episodes. No illness, environmental, or family characteristics were associated with length of carriage. Significant differences were found in weight-for-age and weight-for-height z scores between the never-positive-for-G. lamblia group and all other carriage groups combined. Faltering growth was shown to be subsequent to G. lamblia infection rather than preceding it. Our findings confirm that G. lamblia carriage is not associated with diarrhea. However, the effect on growth deserves further investigation.