Giardia lamblia infections in a cohort of Bangladeshi mothers and infants followed for one year

The Breast Milk Immunoglobulinome

Breast milk components contribute to the infant’s immune development and protection, and among other immune factors, immunoglobulins (Igs) are the most studied. The presence of IgA in milk has been known for a long time; however, less information is available about the presence of other Igs such as IgM, IgG, and their subtypes (IgG1, IgG2, IgG3, and IgG4) or even IgE or IgD. The total Ig concentration and profile will change during the course of lactation; however, there is a great variability among studies due to several variables that limit establishing a clear pattern. In this context, the aim of this review was firstly to shed light on the Ig concentration in breast milk based on scientific evidence and secondly to study the main factors contributing to such variability. A search strategy provided only 75 studies with the prespecified eligibility criteria. The concentrations and proportions found have been established based on the intrinsic factors of the study—such as the sampling time and quantification technique—as well as participant-dependent factors, such as lifestyle and environment. All these factors contribute to the variability of the immunoglobulinome described in the literature and should be carefully addressed for further well-designed studies and data interpretation.

Giardia lamblia infections in children in Ghana

INTRODUCTION

Though giardiasis is an important public health problem in Ghana, several aspects of its epidemiology, particularly the molecular epidemiology has not been investigated adequately. This could be a major hindrance to effective surveillance and control of giardiasis in the country. The study was carried out to determine the prevalence, risk factors and genotypes of Giardia lamblia infecting children at a paediatric hospital in Ghana.

METHODS

A total of 485 patients including 365 diarrhoea and 120 non-diarrhoea children were enrolled into the study. Stool samples were collected and analysed for parasite presence using microscopy, ELISA and PCR. Positive samples were subsequently characterized into assemblages by PCR-RFLP, and further confirmed with sequencing of the glutamate dehydrogenase (gdh) gene. Epidemiological data on demographic, clinical and behavioral features of the study subjects were also collected.

RESULTS

Prevalence of G. lamblia infections in diarrhoea and non-diarrhoea children were 5.8% and 5% respectively (P>0.5). Sequence data confirmed Giardia lamblia assemblage B as the predominant genotype in both diarrhoea and non-diarrhoea cases. There was no significant association of G. lamblia infection with any of the epidemiological variables investigated.

CONCLUSION

Our findings suggest that assemblage B could be the predominant genotype causing giardiasis in children. Increased public health education focusing on good sanitary practices, particularly among mothers and children, could decrease the risk of G. lamblia infection.

Human cellular immune response against Giardia lamblia 5 years after acute giardiasis

BACKGROUND

Clinical and epidemiological studies have suggested the development of acquired immunity in individuals previously infected with Giardia lamblia. However, there are no data on the long-term cellular immunity and genotype cross-reactivity. An outbreak of assemblage B giardiasis in a nonendemic area made it possible to evaluate the long-term cellular mediated immunity and its specificity toward the 2 Giardia assemblages known to infect humans.

METHODS

Peripheral blood mononuclear cells from 19 individuals infected with Giardia assemblage B 5 years previously and from 10 uninfected controls were cultured with antigens from assemblage A and B Giardia trophozoites for 6 days. Cell-mediated immunity was measured by a (3)H-thymidine proliferation assay and flow cytometric analysis of activation markers HLA-DR, CD45RO, CD25, and CD26 in T-cell subsets.

RESULTS

Proliferation responses were significantly elevated in the group previously exposed to Giardia for nearly all Giardia antigens tested. Individual responses toward Giardia trophozoite whole cell, cytosolic, and excretory-secretory antigens from both assemblages correlated well. Activation marker responses were mainly seen in CD4 T cells.

CONCLUSIONS

G. lamblia infection induces long-term, albeit variable, cellular immune responses that are not assemblage specific and that are largely driven by CD4 T-cell activation.

Immune markers in breast milk and fetal and maternal body fluids: a systematic review of perinatal concentrations

Breastfeeding represents the continued exposure of the infant to the maternal immune environment.Uterine, perinatal, and postnatal exposure to immune factors may contribute to an infant’s risk of developing immune-mediated disorders, including allergies. A PubMed search was conducted to review studies in humans and analyze concentrations of immune markers (TGF-beta, IFN-gamma, eotaxin, CCL5, CXCL10, TNF-alpha, MCP-1, IL-1beta, IL-4, IL-5, IL-6,IL-8, IL-10, IL-12, IL-13, sCD14, sIgA, IgG4, IgM) found in maternal serum, amniotic fluid, cord serum, colostrum, transition and mature milk. Concentrations of immune markers showed large variations across samples and studies. Reports documented conflicting results. Small sample sizes, differences in population characteristics, inconsistent sample collection times, and various sample collection and measurement methods may have led to wide variations in the concentrations of immune markers. Studies analyzing the associations between immune markers in maternal fluids and infant allergies remain inconclusive because of gaps in knowledge and a lack of standardized methods.

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.

Parasitic diarrhea in normal and malnourished children

Diarrhea is only one of the many manifestations of intestinal parasites. Environmental influences are inescapable, regardless of an individual's state of health: in a highly endemic region, intestinal parasitic colonization is almost the rule. The clinical expression of the parasitoses, however, is largely determined by host defenses; and when they are weakened, parasitic diarrhea is frequent and severe. Protein-energy malnutrition is by far the most important cause of immune deficiency in developing countries. Diarrhea caused by Strongyloides or Giardia is common and severe in malnourished children, while well-nourished children remain healthy carriers. These parasites require specific treatment in the malnourished; and the well-nourished should have preventive treatment when they are to receive corticosteroids or immunosuppressive agents. Diarrhea caused by Cryptosporidium spp. may be severe in malnourished or immunodeficient children, and recovery is achieved only after renutrition or treatment of the immunodeficiency.

Detection of anti-Giardia lamblia serum antibody among children of day care centers

OBJECTIVES

To detect anti-Giardia lamblia serum antibodies in healthy children attending public day care centers and to assess serological tests as tools for estimating the prevalence of G. lamblia in endemic areas.

METHODS

Three separate stool specimens and filter paper blood samples were collected from 147 children ranging from 0 to 6 years old. Each stool sample was processed using spontaneous sedimentation and zinc sulfate flotation methods. Blood samples were tested by indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA) for Giardia IgG.

RESULTS AND CONCLUSIONS

Of 147 individuals tested, 93 (63.3%) showed Giardia cysts in their feces. Using IIF and ELISA, serum antibodies were detected in 93 (63.3%) and 100 (68%) samples, respectively. Sensitivity of IIF and ELISA was 82% and 72%, respectively. However, ELISA revealed to be less specific (39%) than IIF (70%). IIF also showed a higher concordance with microscopic examination than ELISA.

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.

Giardia duodenalis: inter-strain variability of proteins, antigens, proteases, isoenzymes and nucleic acids

Giardia duodenalis isolates from asymptomatic or symptomatic patients and from animals present similarities and differences in the protein composition, antigenic profile, pattern of proteases and isoenzymes, as well as in nucleic acids analysis. In the present overview, these differences and similarities are reviewed with emphasis in the host-parasite interplay and possible mechanisms of virulence of the protozoon.

Secretory immune response to membrane antigens during Giardia lamblia infection in humans

The secretory immune response in humans infected with Giardia lamblia was studied by using saliva samples and a membrane-rich protein fraction. The membrane fraction, studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, showed 24 antigen bands, ranging from 170 to 14 kDa. Saliva samples from giardiasis patients showed a heterogeneous response against the membrane fraction when they were assayed by immunoblotting. Among the antigens recognized by patient saliva samples, those of 170, 105, 92, 66, 32, 29, and 14 kDa stood out. These antigens were not recognized by saliva samples from healthy individuals. They may be of importance in future studies of protection from or diagnosis of G. lamblia infections.

Growth inhibition of the intestinal parasite Giardia lamblia by a dietary lectin is associated with arrest of the cell cycle

Giardia lamblia, a cause of diarrheal disease throughout the world, is a protozoan parasite that thrives in the small intestine. It is shown here that wheat germ agglutinin (WGA), a naturally occurring lectin widely consumed in normal human diets, reversibly inhibits the growth of G. lamblia trophozoites in vitro, and reduces infection by G. muris in the adult mouse model of giardiasis. The inhibitory effect was dose related, not associated with cytotoxicity and reversed by N-acetyl-D-glucosamine in accordance with the known specificity of the lectin and in agreement with the presence of GlcNAc residues on the surface membrane of G. lamblia trophozoites. Cell cycle analysis revealed that parasites grown in the presence of WGA are arrested in the G2/M phase, providing an explanation for the lectin-induced inhibition of cell proliferation. Comparison of electrophoretic profiles by lectin blot analysis revealed both glycoprotein induction and suppression in growth-arrested organisms. Our findings raise the possibility that blocking trophozoite growth with naturally occurring dietary lectins may influence the course of giardiasis. In addition, the study of cell cycle arrest by WGA may provide a model to study the regulation of cell division in lower eukaryotes.

Prevalence of giardiasis among primary school children

This cross-sectional study was conducted to investigate the prevalence of intestinal parasites among primary school children in Northern Jordan. Stool specimens were collected from 1100 children of both sexes from urban and rural schools. A questionnaire covering relevant informations was completed for each child. Wet mount preparation, formaline-ether concentration technique, and trichrome stain were prepared for the recovery and identification of parasites. Giardia lamblia was observed in 396 (36%) of the stool specimens examined. The infection rates were higher in the younger age group where several of them had diarrhoea and reported variable symptoms. The infection rates declined with age and children were asymptomatic. Rates were higher in children from the rural areas, from low income families, and it was higher in boys than girls. Contaminated drinking water is suspected to be the major potential source of infection. The importance of the asymptomatic cases and the epidemiological factors contributing to the transmission in these areas are discussed.

Immunologic benefits of breast milk in relation to human milk banking

A review of the immunologic benefits of human milk is presented, with emphasis on the antiviral properties of human milk. These properties are so important to infant health that the World Health Organization has restated its recommendation. "In all populations, irrespective of HIV infection rates, breast-feeding should continue to be protected, promoted, and supported." Infection control procedures are described for human milk banking, which should be supported as an immunologically beneficial feeding alternative for infants.

Diagnosis of Giardia duodenalis infection in Bangladeshi infants: faecal antigen capture ELISA

An enzyme-linked immunosorbent assay (ELISA) to detect antigens of Giardia duodenalis in faeces was evaluated as a diagnostic tool by testing faecal samples collected during a cohort study of 229 infants living in an urban slum in Dhaka, Bangladesh. Faecal samples had been collected at enrollment, on a routine monthly basis, and repeatedly during episodes of diarrhoea and infection with Giardia, and a portion of all samples was frozen in saline. A direct smear of all had been examined by microscopy and again after concentrating cysts by ether sedimentation. A total of 2121 of the 4936 samples stored during the 22 months study were tested by the ELISA. After excluding non-specific binding, the sensitivity of the assay was 94.2% and the specificity was 98%. The presence of other parasites, including flagellated protozoa, was not linked to false positive ELISA results. There was a correlation between the number of Giardia cysts present and the ELISA optical density. Assuming that the ELISA is 100% sensitive, microscopy detected 92.4% of the infections detected by the ELISA.

Protection against infection with Giardia lamblia by breast-feeding in a cohort of Mexican infants

To determine whether breast-feeding protects infants against symptomatic and asymptomatic infection by Giardia lamblia, we followed 197 infants in a poor area of Mexico City from birth to 18 months of age; symptoms and feeding status were recorded weekly. Stool specimens were collected every 1 to 2 weeks and tested for Giardia by enzyme-linked immunosorbent assay. A mean of 1.0 Giardia infection per child-year was detected; 94 infants had a total of 139 infections; 17% of infections were symptomatic. Ninety-one percent of infants were breast fed from birth and 38% were breast fed at 1 year of age. Lack of breast-feeding was a significant risk factor for first Giardia infection at all ages. The adjusted incidence rate ratio for first Giardia infection for none versus complete breast-feeding was 5.0 (confidence interval (CI) 1.5 to 16.9; p = 0.009), and for none versus any breast-feeding, 1.8 (CI 1.1 to 2.8; p = 0.013). Symptomatic Giardia infection was also associated with lack of breast-feeding (none vs any: incidence rate ratio = 2.5; CI 0.9 to 6.8; p = 0.077), but breast-feeding did not protect against chronic carriage of Giardia. Other significant risk factors for Giardia infection were presence of animals in the household (p = 0.005) and the use of water or nonmilk liquid for infant feedings (p = 0.035). We conclude that breast-feeding protects infants against Giardia by mechanisms that include preventing the establishment of infection.

Effect of human milk and infant milk formulae on adherence of Giardia intestinalis

Human milk was shown to inhibit adherence of Giardia at concentrations as low as 0.5%. Unsaturated fatty acids were also found to cause significant inhibitory effects on adherence, with ED50 values less than 1 microM for arachidonic, linoleic and palmitic acids. A variety of infant feeding formulae derived from cow's milk and soy bean had suppressive effects on adherence. These observations may explain in part the low prevalence of giardiasis in young infants.

Detection of Giardia lamblia antigen in children living in a Peruvian periurban shantytown (Pueblo Joven)

Stool microscopy and an enzyme-linked immunosorbent assay (ELISA) for Giardia lamblia antigen detection were compared for detecting G. lamblia in 30 Peruvian infants. Of 1,131 fecal specimens, G. lamblia was detected by ELISA alone in 44, by microscopy alone in 17, and by both methods in 91. In another group of 17 children negative for G. lamblia by stool microscopy, 6 had G. lamblia detected by ELISA or duodenal aspiration: 2 only by ELISA, 1 only by duodenal aspirate examination, and 3 by both examinations. The ELISA is useful for the detection of G. lamblia in fecal specimens but compared to stool microscopy does not significantly increase the detection of cases.

Parasitism and diarrhoea in children from two rural communities and marginal barrio in Honduras

In Honduras, one of the leading causes of morbidity and mortality among children is diarrhoea, but little is known about its aetiology and risk factors. A prospective longitudinal study of 266 children over a 12 month period in 2 rural villages and a marginal barrio revealed attack rates of 7 episodes per child per year among those less than 36 months of age. The most common parasite was Giardia lamblia, found in 61% of the children and in 29% of 848 episodes of diarrhoea. Chronic diarrhoea was noted in 46.6% of the children and 81% of them were infected with G. lamblia. Multiple infections with 5-10 different species of parasites or commensals were common (47%); no parasites or commensals were found in 17 children (6.4%). No case of acute amoebic dysentery was diagnosed either clinically or parasitologically, although 20% of the children had cysts of E. histolytica in the stools. Other potential parasitic pathogens identified were Cryptosporidium sp. (6.7%), Hymenolepis nana (8%), and Strongyloides stercoralis (2.6%). Dientamoeba fragilis was found in iron haematoxylin smears for the first time in Honduras. Important risk factors recognized included high faecal contamination of the environment, lack of potable water, education and housing in the midst of poverty. The marginal barrio was more affected than the rural villages. Should these factors not be changed or modified, diarrhoea caused by infectious agents will remain an endemic life-threatening problem.

Zoonotic aspects of giardiasis: a review

Several studies suggested that some water-borne epidemics of giardiasis in the U.S.A. were of zoonotic origin. Also, cats and dogs were suspected of being sources of giardiasis for man. These observations have been partly supported by experimental cross-transmissions. However, there are also some indications that zoonotic giardiasis may not be common. The host-specificity of Giardia spp. is still controversial. To date, morphological characteristics can only differentiate three very basic types of Giardia: G. intestinalis, G. muris and G. agilis. Host-specific and morphometric criteria resulted in the description of more than 40 species of Giardia; many of them probably invalid. Only a few subtle antigenic differences among G. intestinalis (lamblia) strains have been observed. The comparison of isoenzymes and DNA banding patterns revealed 3 basic groups, not necessarily related to host origin. Further biochemical, immunological, genetic and cross-transmission studies in host and parasite populations are needed to better understand host-specificity of various Giardia isolates. At the present time one may only conclude that although mammals and man do not seem to possess their own unique species of Giardia, in reality the major methods of transmission of giardiasis probably remain basically host-specific.

Recurrent outbreaks of giardiasis in a child day care center, Wisconsin

In the 19-month period September 1983-March 1985, three outbreaks of giardiasis occurred in one large child day care center. Control measures instituted during each outbreak included case finding; pharmacologic treatment and follow-up testing of stool specimens for cases of giardia infection in day care children and staff, and their household contacts; facilitating and stressing personal and environmental hygiene, including altering diapering practices and teaching appropriate hand washing techniques. In the first, second, and third outbreaks, overall attack rates (stool analysis positive for Giardia lamblia) were determined for those persons with greater than or equal to 2 stool specimens submitted; attack rates in children were 47, 17, and 37 per cent, respectively; for tested staff, the rates were 35, 13, and 9 per cent; and for tested household contacts were 18, 9, and 5 per cent. Attack rates were highest for ambulatory diapered children, children attending the day care center greater than or equal to 40 hours per week, and children who were infected with G. lamblia in the most recent previous outbreak. Despite extensive efforts to identify cases, a cure rate of greater than 90 per cent in treated cases, and improvements in personal and environmental hygiene practices, G. lamblia infections recurred in outbreak proportions.

Rapid reinfection by Giardia lamblia after treatment in a hyperendemic Third World community

In a peri-urban shanty town in Lima, Peru, that was hyperendemic for Giardia lamblia, 44 children aged between 0.9 months and 10 years were effectively treated for Giardia lamblia with tinidazole. Stools were examined weekly in the 6 months after treatment to determine the rate of reinfection, and after reinfection stools continued to be examined. 98% of the children became reinfected with Giardia lamblia within 6 months, and after reinfection stool excretion of the parasite lasted a mean (SD) of 3.2 (3.3) months. The children's mean stool pH and their mean stool fat index was unaffected by Giardia lamblia reinfection. Treatment of all symptomless Giardia lamblia infections in a developing country hyperendemic for the disease is of questionable value because of rapid reinfection.

Antibodies to cysts of Giardia lamblia in primary giardiasis and in the absence of giardiasis

The significance of serum antibodies binding to cysts of Giardia lamblia was evaluated by indirect immunofluorescence. Titers of 10 or higher were found in 85.6% of adults, who had probably never had giardiasis. Titers in 118 adults (geometric mean, 29.9) were higher than in 35 children (16.4), and titers in women (42.3) were higher than in men (20.0). Titers in 150 patients with primary giardiasis (80.4) were higher than in control adults, but overlapping precluded serological diagnosis. Titers increased with the duration of infection. Female patients had higher titers (100.5) than did males (66.1), but men who had been infected longer than 45 days had high titers (132). Titers in second serum samples taken from 26 patients 2 weeks to 3 months after successful nitroimidazole treatment (58.1) were lower than before treatment (151.7) but higher than in 118 controls. We conclude that most people have antibodies which cross-react with G. lamblia but which are induced by other immunogens and that primary giardiasis induces protracted systemic antibody responses.

The prevalence of Entamoeba histolytica in lactating women and in their infants in Bangladesh

Entamoeba histolytica was studied in 33 lactating women and their infants in a periurban village in Bangladesh. Infant-mother pairs were followed for a period of 10-15 months: 67% of mothers excreted E. histolytica during the observation period, the majority for 3 months or more. Only one mother was symptomatic, with a mild, non-dysenteric diarrhoea. 58% of mothers were seropositive, several of them continuously and with a high titre, indicating past invasive infection. 67% had detectable antibodies in breast milk and 36% in saliva. Despite the high prevalence of E. histolytica in these mothers, infants were mostly uninfected: E. histolytica cysts in small numbers were found in only 2 of 1200 samples from infants aged 6 and 10 months. Several of the children were infected with Giardia lamblia. Although lower exposure to E. histolytica than to Giardia may account for the difference in infant infection rates with these parasites, defence mechanisms possibly exist which protect against E. histolytica but are ineffective against Giardia.

Epidemiology of Giardia lamblia infection in children: cross-sectional and longitudinal studies in urban and rural communities in Zimbabwe

Stool specimens from 3,038 children in rural and urban areas near Harare were examined for Giardia lamblia cysts. Preliminary studies, using specimens collected on three consecutive days from 157 known cyst passers, showed that over 89% of infections could be diagnosed on single stool specimens by examination of Gomori-stained smears. The overall prevalence of giardial infection was 19.4% with significantly more urban children (21.1%) passing cysts than rural children (16.7%). In urban areas the highest prevalence was in young (5-6 year) children, while in rural areas, the highest prevalence was in older (9-10 year) children. Of 132 children treated with Entamizole a metronidazole-diloxanide combination, 127 (96.2%) had ceased excreting cysts by the fifth treatment day. Follow-up examination of these children showed a high rate of reinfection, with 29.6% excreting cysts during the year following treatment. During the same period 13.3% of previously uninfected children had started passing cysts, while over half of infected, but untreated, children had undergone apparent "self-cure." Younger children were more likely to be reinfected than older children, and continued excreting cysts for a longer period of time.

Parasitic diseases of the small intestinal tract

The epidemiology, clinical aspects, and treatment of human intestinal infections with Giardia, Cryptosporidium, coccidia and Strongyloides in industrialized countries are reviewed. In well-nourished and immunocompetent persons, inapparent infections or mild, transitory gastrointestinal upsets caused by these parasites are quite common. Some patients develop severe symptoms, such as profuse diarrhoea, dehydration, stool irregularities for weeks or months followed by weight loss and malabsorption of fat, vitamins and iron. In patients receiving immunosuppressive treatment or with lymphotropic viral infections, Cryptosporidium and Strongyloides can cause life-threatening or debilitating disease. By autoinfection or external reinfection these parasites can persist in the intestine for years. Clinicians should consider such infections in immigrants, travellers and former servicemen, even long after their stay in endemic areas, and also in the handicapped and children in day-care centres.

Age-related rate of seropositivity of antibody to Giardia lamblia in four diverse populations

We used a solid-phase enzyme immunoassay to determine the age-specific rates of acquisition of antibody to Giardia lamblia in populations living in an inner city area of Baltimore, Md., on an Apache Indian reservation in Arizona, in a rural area of Panama, and in an urban area of Peru (Lima). Antibody to G. lamblia was found in a portion of the adults living in all of the study areas. Similar prevalence rates and quantitative levels of antibody were found in the adults living in Arizona (44%), Panama (48%), and Peru (46%). However, a significantly lower (P less than 0.05) percentage of the adults living in Baltimore (18%) displayed serological evidence of infection. Different patterns of age-associated acquisition of antibody were noted in the study populations. In the United States, children living in Baltimore had low levels of seropositivity throughout childhood, whereas children living on the Arizona Indian reservation showed a progressive acquisition of antibody early in childhood, with adult levels achieved by 8 years of age. In Latin America, children living in Panama attained adult levels of seropositivity between 9 and 20 years of age, whereas children in Peru displayed adult levels of seropositivity in the first 6 months of life. Our findings documented the widespread occurrence of G. lamblia infections in diverse populations. Children living in different areas and under different environmental conditions displayed widely differing rates of acquisition of antibody to G. lamblia, possibly resulting from different levels of sanitation, water contamination, and person-to-person contact. Our studies indicate that quantitative solid-phase immunoassays can be used to study the epidemiology of parasitic infections such as those caused by G. lamblia.

Single-dose tinidazole for the treatment of giardiasis

Sixty-three expatriate residents and travellers in Bangladesh, infected with Giardia lamblia, participated in two studies to compare the therapeutic efficacy of tinidazole and metronidazole. In the first trial 33 randomly selected patients were treated with tinidazole (50 mg/kg of body weight to a maximum of 2 g) or metronidazole (60 mg/kg of body weight to a maximum of 2.4 g) in a single oral dose. Patients were followed for 4 weeks after the end of therapy for the presence of G. lamblia in their stools. Sixteen (94%) of 17 patients receiving tinidazole were free of G. lamblia during that period, compared to only 9 (56%) of 16 patients who had received metronidazole (P less than 0.02). In the second trial patients were randomly allocated to a treatment schedule of either metronidazole as a single dose on 3 successive days (50 mg/kg of body weight to a maximum of 2 g daily) or tinidazole as a single oral dose (50 mg/kg of body weight to a maximum of 2 g). All 15 patients treated with tinidazole and 14 (93%) of 15 patients treated with metronidazole were free of G. lamblia during the 4-week follow-up period. A single oral dose of tinidazole is a highly effective treatment for giardiasis and is equal in efficacy to a 3-day therapy with metronidazole.