Relationship between intestinal parasitic infection in children and soil contamination in an urban slum

Enterobius vermicularis in Brazil: An integrative review

Enterobius vermicularis, an intestinal helminth, is transmitted through the ingestion of eggs found in food, water, dust, or other fomites, including infected individuals. This review aimed to examine the frequency and distribution of E. vermicularis infections in Brazil between 1991 and 2022. The conducted bibliographic survey revealed that the frequency of E. vermicularis infections in Brazil ranged from 0.1 to 26.1%, depending on factors such as population ethnicity, individual age group, geographic area, time frame, and diagnostic method. However, these findings were based on a limited number of publications, suggesting that the actual prevalence rates of E. vermicularis infection may still be unknown and potentially underestimated.

Effect of sanitation improvements on soil-transmitted helminth eggs in courtyard soil from rural Bangladesh: Evidence from a cluster-randomized controlled trial

Improved sanitation has been hypothesized to reduce soil-transmitted helminth (STH) infections by reducing the prevalence and concentration of STH eggs/larvae in soil. We evaluated the effect of a randomized sanitation program (providing households with an improved dual-pit latrine, tools for child/animal feces management, and behavioral messaging) on reducing the prevalence and concentration of STH eggs in soil from household courtyards. We collected soil samples from 1405 households enrolled in the sanitation intervention (n = 419) and control (n = 914) groups of a cluster-randomized controlled trial (WASH Benefits) in rural Bangladesh approximately 2 years after the initiation of the interventions. We analyzed samples for Ascaris lumbricoides, Trichuris trichiura, and hookworm eggs by microscopy. We estimated prevalence ratios (PR) and egg count ratio (ECR) to compare the prevalence of STH eggs and arithmetic and geometric mean egg counts for STH eggs per gram of soil in the sanitation and control arms. Among intervention households, latrines achieved high and sustained user uptake by adults while child open defecation remained common and most households did not dispose of child feces hygienically. In courtyard soil from control households, the prevalence of any STH eggs was 75.7% and the prevalence of any larvated STH eggs was 67.3%. A. lumbricoides was detected in 63.0% of control samples and T. trichiura in 55.7% of control samples; hookworm was not detected in any sample. In the control arm, the arithmetic mean egg count for any STH was 3.96 eggs/dry gram, while the geometric mean was 1.58 eggs/dry gram. There was no difference between the intervention and control groups in the prevalence of any STH eggs (PR = 0.98 (95% CI: 0.91, 1.05)) or mean egg counts (ECR = 0.08 (95% CI: -0.10, 0.26) for geometric mean and 0.07 (95% CI: -0.22, 0.37) for arithmetic mean). Adjusted models gave similar results. A compound-level sanitation intervention that provided improved latrines and tools for disposal of child and animal feces did not have an impact on STH eggs in soil. In order to effectively reduce the prevalence and concentration of STH eggs in the environment, sustained, widespread use of sanitation strategies to isolate and hygienically dispose of child and animal feces may need to complement traditional strategies for containment of adult human feces. Trial Registration: NCT01590095.

Diversity, geographical distribution, and prevalence of Entamoeba spp. in Brazil: a systematic review and meta-analysis

The genus Entamoeba includes a variety of widely distributed species adapted to live in the digestive tracts of humans and a large variety of animals of different classes. The objective of this study was to investigate the prevalence, distribution, and molecular epidemiology of Entamoeba spp. in different classes of hosts in Brazil. Studies that analyzed hosts from several classes, including humans and domestic, wild, or captive animals, were considered. The pooled prevalence of Entamoeba spp. was calculated using the random-effects model. A total of 166 studies on humans and 16 on animals were included. The prevalence of Entamoeba spp. in the Brazilian population was 22% (95% CI: 21–24). The state with the highest prevalence was Paraiba with 72%, followed by Federal District with 53%, and Rondonia with 50%. In immunocompromized patients, the prevalence was 18%, and cancer (36%) was the most prevalent cause of immunosuppression. The prevalence of Entamoeba spp. in animal hosts was 12% (95% CI: 7–17). Captive wild animals and domestic farm animals showed the highest prevalence, with 16% and 15%, respectively. The species found more often were E. coli (86.5%), E. dispar (7.9%), and E. histolytica (3.1%). In conclusion, a high prevalence (22%) of Entamoeba spp. was found in the Brazilian population, with a prevalence of up to 50% mainly in the northern, northeastern, and central-western regions. The pathogenic species E. histolytica is distributed in most Brazilian regions, with significant prevalence percentages. Among animals, unidentified Entamoeba species were most prevalent in mammals.

The presence of Toxoplasma gondii in soil, their transmission, and their influence on the small ruminants and human population: A review

The ecosystem approach has been developed since the 1940s. An ecosystem is a community of living organism and their interaction and conjugation with abiotic factors of the environment. The ecosystem is not endemic to the aquatic environment only but, the terrestrial environment is also considered to be a part of an ecosystem. Soil act as mother role for the survival of different microorganism. The Toxoplasma gondii oocysts stay survive for a long time in the soil. This presence of these oocysts might critically enhance the success of this parasite in two ways. First, this parasite can widespread; second, it can create a lot of consequences regarding animals and their economic value. Soil contamination caused by Toxoplasma gondii Y is a significant and profound issue for animals and public health. Therefore, the current study was aimed to summarize and correlate the soil and parasite, their transmission, infection, and some aspects related to T. gondii. The small animals are pose at a high risk therefore, it was concluded that some preventive measures should be taken to keep secure itself from zoonotic diseases.

Gender-based differences in water, sanitation and hygiene-related diarrheal disease and helminthic infections: a systematic review and meta-analysis

BACKGROUND

Qualitative evidence suggests that inadequate water, sanitation and hygiene (WASH) may affect diarrheal and helminthic infection in women disproportionately. We systematically searched PubMed in June 2014 (updated 2016) and the WHO website, for relevant articles.

METHODS

Articles dealing with the public health relevance of helminthic and diarrheal diseases, and highlighting the role of gender in WASH were included. Where possible, we carried out a meta-analysis.

RESULTS

In studies of individuals 5 years or older, cholera showed lower prevalence in males (OR 0.56; 95% CI 0.34-0.94), while Schistosoma mansoni (1.38; 95% CI 1.14-1.67), Schistosoma japonicum (1.52; 95% CI 1.13-2.05), hookworm (1.43; 95% CI 1.07-1.89) and all forms of infectious diarrhea (1.21; 95% CI 1.06-1.38) showed a higher prevalence in males. When studies included all participants, S. mansoni and S. japonicum showed higher prevalence with males (OR 1.40; 95% CI 1.27-1.55 and 1.84; 95% CI 1.27-2.67, respectively). Prevalence of Trichiuris and hookworm infection showed effect modification with continent.

CONCLUSIONS

Evidence of gender differences in infection may reflect differences in gender norms, suggesting that policy changes at the regional level may help ameliorate gender related disparities in helminthic and diarrheal disease prevalence.

Intestinal parasitic infections and determinant factors among school-age children in Ethiopia: a cross-sectional study

OBJECTIVE

This study aimed to determine the prevalence of intestinal parasitic infections and associated factors among school-age children in Sebeya primary school, northern Ethiopia, 2017.

RESULTS

The prevalence of intestinal parasites in school-age children was (29.9%). A total of six parasites were detected in this study. E. histolytica/dispar 19.43% (82/422) and G. lamblia 8.29% (35/422) were the predominant ones. Unclean fingernail (AOR = 1.72), defecating in the open field (AOR = 2.82), and being barefooted (AOR = 1.72) were the determinant factors for intestinal parasitic infections. Frequently washing hands reduced the chance of infections by 68%. Furthermore, children in grade 1-4 and 5-6 had higher odds developing the infections than those in grade 7-8 (AOR = 8.21 and AOR = 2.50, respectively).

The extent, nature, and pathogenic consequences of helminth polyparasitism in humans: A meta-analysis

Background

Individual helminth infections are ubiquitous in the tropics; geographical overlaps in endemicity and epidemiological reports suggest areas endemic for multiple helminthiases are also burdened with high prevalences of intestinal protozoan infections, malaria, tuberculosis (TB), and human immunodeficiency virus (HIV). Despite this, pathogens tend to be studied in isolation, and there remains a need for a better understanding of the community ecology and health consequences of helminth polyparasitism to inform the design of effective parasite control programs.

Methodology

We performed meta-analyses to (i) evaluate the commonality of polyparasitism for helminth-helminth, helminth-intestinal protozoa, helminth-malaria, helminth-TB, and helminth-HIV co-infections, (ii) assess the potential for interspecies interactions among helminth-helminth and helminth-intestinal protozoan infections, and (iii) determine the presence and magnitude of association between specific parasite pairs. Additionally, we conducted a review of reported health consequences of multiply-infected individuals compared to singly- or not multiply-infected individuals.

Principal findings

We found that helminth-helminth and helminth-intestinal protozoan multiple infections were significantly more common than single infections, while individuals with malaria, TB, and HIV were more likely to be singly-infected with these infections than co-infected with at least one helminth. Most observed species density distributions significantly differed from the expected distributions, suggesting the potential presence of interspecies interactions. All significant associations between parasite pairs were positive in direction, irrespective of the combination of pathogens. Polyparasitized individuals largely exhibited lower hemoglobin levels and higher anemia prevalence, while the differences in growth-related variables were mostly statistically insignificant.

Conclusions

Our findings confirm that helminth polyparasitism and co-infection with major diseases is common in the tropics. A multitude of factors acting at various hierarchical levels, such as interspecies interactions at the within-host infra-parasite community level and environmental variables at the higher host community level, could explain the observed positive associations between pathogens; there remains a need to develop new frameworks which can consider these multilevel factors to better understand the processes structuring parasite communities to accomplish their control.

Helminth infections are a highly prevalent global health problem. These parasitic worm infections occur in areas also burdened with intestinal protozoan infections, malaria, tuberculosis, and human immunodeficiency virus. While these pathogens tend to be studied in isolation, there remains a need to better understand the nature, extent, and health consequences of helminth polyparasitism and co-infection with major diseases. Here, we reviewed the literature and performed meta-analyses to evaluate the commonality of helminth polyparasitism and co-infection, the potential for interspecies interactions between parasites, the association between parasite pairs, and the health consequences among multiply-infected individuals. We confirmed that polyparasitism and co-infection with major diseases are common in the global South and found that multiply-infected individuals experienced worse health consequences when compared to singly or not-multiply infected individuals. Our analysis suggested the potential presence of interspecies interactions and we identified the existence of positive associations between parasite pairs. These findings support the call for integrating deworming into malaria, TB, and HIV treatment protocols and suggest there remains a need to improve our understanding of the factors influencing co-transmission to achieve sustainable parasite control.

Effect of a sanitation intervention on soil-transmitted helminth prevalence and concentration in household soil: A cluster-randomized controlled trial and risk factor analysis

Improved sanitation has been associated with a reduced prevalence of soil-transmitted helminth (STH) infection and has been hypothesized to prevent fecal contamination from spreading throughout the household environment. We evaluated the effect of providing households with a pit latrine with a plastic slab and drophole cover, child feces management tools, and associated behavioral messaging on reducing STH eggs in household soil. We collected soil samples from 2107 households (898 control and 1209 improved sanitation intervention households) that were enrolled in the WASH Benefits cluster randomized controlled trial in rural Kenya and performed a post-intervention analysis after two years of intervention exposure. Following a pre-specified analysis plan, we combined all households that received the sanitation intervention into one group for comparison to control households. The prevalence of STH eggs in soil was 18.9% in control households and 17.0% in intervention households. The unadjusted prevalence ratio of total STH eggs in the intervention groups compared to the control group was 0.94 (95% CI: 0.78-1.13). The geometric mean concentration was 0.05 eggs/g dry soil in control households and intervention households. Unadjusted and adjusted models gave similar results. We found use of a shared latrine, presence of a roof over the sampling area, and the number of dogs owned at baseline was associated with an increased prevalence of STH eggs in soil; the presence of a latrine that was at least 2 years old and a latrine with a covered drophole was associated with a reduction in the prevalence of STH eggs in soil. Soil moisture content was also associated with an increased prevalence of STH eggs in soil. Our results indicate that an intervention designed to increase access to improved latrines and child feces management tools may not be enough to impact environmental occurrence of STH in endemic areas where latrine coverage is already high.

Intestinal parasitic infections among expatriate workers in various occupations in Sharjah, United Arab Emirates

Intestinal parasitic infections are prevalent throughout many countries. This study aimed to determine the prevalence of intestinal parasite carriers among 21,347 expatriate workers, including food handlers and housemaids attending the public health center laboratory in Sharjah, UAE. Stool sample collection was performed throughout the period between January and December 2013. All samples were examined microscopically. Demographic data were also obtained and analyzed. Intestinal parasites were found in 3.3% (708/21,347) of the studied samples (single and multiple infections). Among positive samples, six hundred and eighty-three samples (96.5%) were positive for a single parasite: Giardia lamblia (257; 36.3%) and Entamoeba histolytica/Entamoeba dispar (220; 31.1%), respectively, whereas mono-infections with helminths accounted for 206 (29.1%) of the samples. Infection rates with single worms were: Ascaris lumbricoides (84; 11.9%), Hookworm (34; 4.8%), Trichuris trichiura (33; 4.7%), Taenia spp. (27; 3.81%), Strongyloides stercoralis (13; 1.8%), Hymenolepis nana (13; 1.8%), and Enterobius vermicularis (2; 0.28%), respectively. Infections were significantly associated with gender (x² = 14.18; p = 0.002) with males as the most commonly infected with both groups of intestinal parasites (protozoa and helminths). A strong statistical association was noted correlating the parasite occurrence with certain nationalities (x²= 49.5, p <0.001). Furthermore, the study has also found a strong statistical correlation between parasite occurrence and occupation (x²= 15.60; p = 0.029). Multiple infections were not common (3.5% of the positive samples), although one individual (0.14%) had four helminth species, concurrently. These findings emphasized that food handlers with different pathogenic parasitic organisms may pose a significant health risk to the public.

Household sanitation is associated with lower risk of bacterial and protozoal enteric infections, but not viral infections and diarrhoea, in a cohort study in a low-income urban neighbourhood in Vellore, India

Objective

This study examined associations between household sanitation and enteric infection – including diarrhoeal‐specific outcomes – in children 0–2 years of age in a low‐income, dense urban neighbourhood.

Methods

As part of the MAL‐ED study, 230 children in a low‐income, urban, Indian neighbourhood provided stool specimens at 14–17 scheduled time points and during diarrhoeal episodes in the first 2 years of life that were analysed for bacterial, parasitic (protozoa and helminths) and viral pathogens. From interviews with caregivers in 100 households, the relationship between the presence (and discharge) of household sanitation facilities and any, pathogen‐specific, and diarrhoea‐specific enteric infection was tested through mixed‐effects Poisson regression models.

Results

Few study households (33%) reported having toilets, most of which (82%) discharged into open drains. Controlling for season and household socio‐economic status, the presence of a household toilet was associated with lower risks of enteric infection (RR: 0.91, 95% CI: 0.79–1.06), bacterial infection (RR: 0.87, 95% CI: 0.75–1.02) and protozoal infection (RR: 0.64, 95% CI: 0.39–1.04), although not statistically significant, but had no association with diarrhoea (RR: 1.00, 95% CI: 0.68–1.45) or viral infections (RR: 1.12, 95% CI: 0.79–1.60). Models also suggested that the relationship between household toilets discharging to drains and enteric infection risk may vary by season.

Conclusions

The presence of a household toilet was associated with lower risk of bacterial and protozoal enteric infections, but not diarrhoea or viral infections, suggesting the health effects of sanitation may be more accurately estimated using outcome measures that account for aetiologic agents.

Comparison between Two Decades of Prevalence of Intestinal Parasitic Diseases and Risk Factors in a Brazilian Urban Centre

Objectives. This study's objective was to compare the prevalence of intestinal parasites and associated risk factors in children in urban communities, in the Brazilian Northeast, between two decades. Methods. This quantitative transversal study consisted of a comparative analysis of two different samples: the first viewing the years 1992-1996 and the other through a coproepidemiological data survey undertaken in 2010-2011. Results. It was evidenced that there was a reduction of intestinal parasites and that there were improvements in the socioenvironmental conditions between the two decades evaluated. It was observed that, in the period 1992-1996, playing out in the streets was associated with a higher risk for acquiring intestinal parasites. Over the 2010-2011 period, the characteristics of more than five residents per household, houses with dirt floors, children who live in homes without piped water, and children who play out in the streets were associated with a higher risk of intestinal parasitic infection. Conclusion. The study showed a reduction of intestinal parasitic diseases to 23.8% in 2010-2011 from 81.3% in 1992-1996 and improvement of the social-sanitary conditions of the population between the decades analyzed.

[Child health environment in the context of relocating of camp site families to social housing]

INTRODUCTION

Housing interventions aimed at overcoming poverty can lead to changes in the health status of children by modifying risk factors in their physical and social environment

OBJECTIVE

the aim was to identify children's environmental health factors to change with the relocation of families from slums to public housing.

SUBJECTS AND METHOD

A cross-sectional study was conducted in children ages 2-8 years old of families relocated to public housing (n=115) who were compared to children residing in slums (n=88) in Santiago, Chile. Family socioeconomic characteristics, indoor environment and neighborhoods were collected. It was included respiratory symptoms, accidents and maternal-child care of children. χ2, Fisher and Mann-Whitney test were used to compare groups.

RESULTS

There were differences in households related to pets keeping, presence of humidity/molds in homes, types of fuels, and perceived safety problems in neighborhoods (p<0.05). The families from slums reported higher tenancy of pets (73.8% v/s 32.2%%), humidity/molds in homes (43.,2% v/s 18.3%), use of wood for heating (39.8% v/s 0.0%), compared with families of public housing. Residents of public housing perceived more safety problems in neighborhood, and children have more asthma related symptoms and have lower diversity of accidents in home.

CONCLUSION

Among the factors studied, indoor air quality and safety in neighborhoods could be linked to changes from the relocation of families. This reinforces the need to deepen the positive and negative influences of residential mobility of these groups focused on child welfare perspective.

Soil-transmitted helminths in pre-school-aged and school-aged children in an urban slum: a cross-sectional study of prevalence, distribution, and associated exposures

Soil-transmitted helminths (STHs) are controlled by regular mass drug administration. Current practice targets school-age children (SAC) preferentially over pre-school age children (PSAC) and treats large areas as having uniform prevalence. We assessed infection prevalence in SAC and PSAC and spatial infection heterogeneity, using a cross-sectional study in two slum villages in Kibera, Nairobi. Nairobi has low reported STH prevalence. The SAC and PSAC were randomly selected from the International Emerging Infections Program's surveillance platform. Data included residence location and three stools tested by Kato-Katz for STHs. Prevalences among 692 analyzable children were any STH: PSAC 40.5%, SAC 40.7%; Ascaris: PSAC 24.1%, SAC 22.7%; Trichuris: PSAC 24.0%, SAC 28.8%; hookworm < 0.1%. The STH infection prevalence ranged from 22% to 71% between sub-village sectors. The PSAC have similar STH prevalences to SAC and should receive deworming. Small areas can contain heterogeneous prevalences; determinants of STH infection should be characterized and slums should be assessed separately in STH mapping.

Update on the mapping of prevalence and intensity of infection for soil-transmitted helminth infections in Latin America and the Caribbean: a call for action

It is estimated that in Latin America and the Caribbean (LAC) at least 13.9 million preschool age and 35.4 million school age children are at risk of infections by soil-transmitted helminths (STH): Ascaris lumbricoides, Trichuris trichiura and hookworms (Necator americanus and Ancylostoma duodenale). Although infections caused by this group of parasites are associated with chronic deleterious effects on nutrition and growth, iron and vitamin A status and cognitive development in children, few countries in the LAC Region have implemented nationwide surveys on prevalence and intensity of infection. The aim of this study was to identify gaps on the mapping of prevalence and intensity of STH infections based on data published between 2000 and 2010 in LAC, and to call for including mapping as part of action plans against these infections. A total of 335 published data points for STH prevalence were found for 18 countries (11.9% data points for preschool age children, 56.7% for school age children and 31.3% for children from 1 to 14 years of age). We found that 62.7% of data points showed prevalence levels above 20%. Data on the intensity of infection were found for seven countries. The analysis also highlights that there is still an important lack of data on prevalence and intensity of infection to determine the burden of disease based on epidemiological surveys, particularly among preschool age children. This situation is a challenge for LAC given that adequate planning of interventions such as deworming requires information on prevalence to determine the frequency of needed anthelmintic drug administration and to conduct monitoring and evaluation of progress in drug coverage.

Soil-transmitted helminths (STH) are part of the group of neglected infectious diseases (NID) in Latin America and the Caribbean (LAC), and are associated with several adverse chronic effects on child health. Although control interventions such as periodic administration of anthelmintic drugs, health education, improved access to safe water and sanitation, among others, are acknowledged to be an important means to reduce morbidity and to achieve control, epidemiological information on prevalence status is lacking at the lowest sub-national administrative levels (municipalities, districts or provinces) in many countries thus hindering decision making regarding not only the treatment, but also the monitoring of progress in deworming coverage, the assessment of epidemiological impact on parasite prevalence and load and, therefore, the achievement of the overall public health goals. Epidemiological surveys can be expensive and require time and effort for their implementation, which could explain the low number of studies published with data on prevalence and intensity of infection in the Americas. The use of alternative methodologies, for instance those based on geographical information systems and remote sensing technologies, or of sentinel surveillance in schools may help countries in the task of collecting information and support the implementation of integrated control programs against STH.

Intestinal parasitic infections in children presenting with diarrhoea in outpatient and inpatient settings in an informal settlement of Nairobi, Kenya

BACKGROUND

The distribution of and factors associated with intestinal parasitic infections are poorly defined in high risk vulnerable populations such as urban slums in tropical sub-Saharan Africa.

METHODS

In a cross sectional study, children aged 5 years and below who presented with diarrhoea were recruited from selected outpatient clinics in Mukuru informal settlement, and from Mbagathi District hospital, Nairobi, over a period of two years (2010-2011). Stool samples were examined for the presence of parasites using direct, formal-ether concentration method and the Modified Ziehl Neelsen staining technique.

RESULTS

Overall, 541/2112 (25.6%) were positive for at least one intestinal parasite, with the common parasites being; Entamoeba histolytica, 225 (36.7%),Cryptosporidium spp. 187, (30.5%), Giardia lamblia, 98 (16%).The prevalence of intestinal parasites infection was higher among children from outpatient clinics 432/1577(27.4%) than among those admitted in hospital 109/535 (20.1%) p < 0.001. Infections with E. histolytica, and G. lamblia were higher among outpatients than inpatients (13.8% vs 1.3% p < 0.001 and 5.8% vs 1.3% p < 0.049) respectively, while infection with Cryptosporidium spp. was higher among inpatients than outpatients (15.3% vs 6.7%) respectively p < 0.001. Other parasites isolated among outpatients included Isospora belli, 19 (1.2%), Ascaris lumbricoides, 26 (1.6%), and Hymenolepis nana 12 (0.8%), with the remainder detected in less than ten samples each. HIV-infected participants were more likely to be infected with any parasite than uninfected participants, Adjusted Odds Ratio (AOR), 2.04, 95% CI, 1.55-2.67, p < 0.001), and with Cryptosporidium spp. (AOR, 2.96, 95% CI 2.07-4.21, p < 0.001).The inpatients were less likely to be infected with E. histolytica than outpatients (AOR, 0.11, 95% CI, 0.51-0.24, p < 0.001), but more likely for inpatients to be infected with Cryptosporidium spp. than outpatients (AOR, 1.91, 95% CI, 1.33-2.73, p < 0.001). Mixed parasitic infections were seen in 65 (12.0%) of the 541 infected stool samples.

CONCLUSION

Intestinal parasitic infections are common in urban informal settlements' environment. Routine examinations of stool samples and treatment could benefit both the HIV infected and uninfected children in outpatient and inpatient settings.

Zoonotic potential and molecular epidemiology of Giardia species and giardiasis

Molecular diagnostic tools have been used recently in assessing the taxonomy, zoonotic potential, and transmission of Giardia species and giardiasis in humans and animals. The results of these studies have firmly established giardiasis as a zoonotic disease, although host adaptation at the genotype and subtype levels has reduced the likelihood of zoonotic transmission. These studies have also identified variations in the distribution of Giardia duodenalis genotypes among geographic areas and between domestic and wild ruminants and differences in clinical manifestations and outbreak potentials of assemblages A and B. Nevertheless, our efforts in characterizing the molecular epidemiology of giardiasis and the roles of various animals in the transmission of human giardiasis are compromised by the lack of case-control and longitudinal cohort studies and the sampling and testing of humans and animals living in the same community, the frequent occurrence of infections with mixed genotypes and subtypes, and the apparent heterozygosity at some genetic loci for some G. duodenalis genotypes. With the increased usage of multilocus genotyping tools, the development of next-generation subtyping tools, the integration of molecular analysis in epidemiological studies, and an improved understanding of the population genetics of G. duodenalis in humans and animals, we should soon have a better appreciation of the molecular epidemiology of giardiasis, the disease burden of zoonotic transmission, the taxonomy status and virulences of various G. duodenalis genotypes, and the ecology of environmental contamination.

Epidemiology and control of human gastrointestinal parasites in children

Parasites found in the human gastrointestinal tract can be largely categorized into two groups, protozoa and helminths. The soil-transmitted helminths (Ascaris lumbricoides, hookworm and Trichuris trichiura) are the most prevalent, infecting an estimated one-sixth of the global population. Infection rates are highest in children living in sub-Saharan Africa, followed by Asia and then Latin America and the Caribbean. The current momentum towards global drug delivery for their control is at a historical high through the efforts of numerous initiatives increasingly acting in coordination with donors, governments and local communities. Together, they have delivered enormous quantities of drugs, especially anthelmintics to children through nationwide annual or biannual mass drug administration largely coordinated through schools. However, a much larger and rapidly growing childhood population in these regions remains untreated and suffering from more than one parasite. Mass drug administration has profound potential for control but is not without considerable challenges and concerns. A principal barrier is funding. Stimulating a research and development pipeline, supporting the necessary clinical trials to refine treatment, in addition to procuring and deploying drugs (and sustaining these supply chains), requires substantial funding and resources that do not presently exist. Limited options for chemotherapy raise concerns about drug resistance developing through overuse, however, satisfactory pharmaco-epidemiology and monitoring for drug resistance requires more developed health infrastructures than are generally available. Further, the limited pharmacopeia does not include any effective second-line options if resistance emerges, and the research and development pipeline is severely depressed. Herein, we discuss the major gastrointestinal protozoa and helminths reviewing their impact on child health, changing epidemiology and how this relates to their control.