Summary: 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.

Zoonotic Potential and Molecular Epidemiology of Giardia Species and Giardiasis

Summary Background Sanitation is inadequate in most cities in developing countries, with major effects on infectious disease burden: in this situation, is piped sewerage an appropriate solution, or should efforts focus on systems based on onsite solutions, such as latrines? We reviewed the effects of the presence of sewerage systems on diarrhoeal disease and related outcomes. We included only observational studies because so far there have been no randomised controlled trials. Methods We identified relevant studies by use of a comprehensive strategy including searches of Medline and other databases from 1966 to February, 2010. In studies that compared sewerage with one other sanitation category, we used relative risk (RR) estimates for sewerage versus the other category. When a single study made two or more comparisons, we calculated a weighted average RR value, and used this value in our meta-analysis. We used the most adjusted RR estimate provided by the authors; if no adjusted estimate was available, we used the crude estimate. To obtain pooled-effect estimates, meta-analyses were done by use of an inverse variance method—ie, the study-specific adjusted log ORs for case-control and cross-sectional studies, and log RRs for cohort studies, were weighted by the inverse of their variance to compute a pooled RR with 95% CI. Findings 25 studies investigated the association between sewerage and diarrhoea or related outcomes, including presence of intestinal nematodes. Pooled estimates show that sewerage systems typically reduce diarrhoea incidence by about 30% (RR 0·70, 95% CI 0·61–0·79), or perhaps as much as 60% when starting sanitation conditions are very poor. Studies with objective outcome measures showed even stronger pooled effect than studies that assessed diarrhoea incidence with interviews, while sensitivity analysis indicated that the effect remains even if we assume strong residual confounding. Interpretation Sewerage interventions seem to reduce the incidence of diarrhoea and related outcomes. However, we urge cautious interpretation of these findings, because, in many contexts, sewerage might be less cost effective and sustainable than onsite alternatives. Funding None.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(10)70123-7.pdf

Effects of sewerage on diarrhoea and enteric infections: a systematic review and meta-analysis

Intestinal parasitic infections are common infectious diseases causing many health problems and impaired growth and physical development.. Children under five years old are the most vulnerable to infections, due to their immature immunity and feeding and exploratory behaviours. This systematic review aimed to assess the relationship between intestinal parasitic infections and undernutrition among children under 5 years old. Fifteen studies met the inclusion and exclusion criteria and were classified as high-quality studies. Twelve parasites were reported, including Ascaris lumbricoides, Cryptosporodium spp., Entamoeba histolytica, Enterobius vermicularis, Giardia lamblia, hookworm, Hymenolepis nana, Strongyloides sterocalis, Taenia spp. and Trichuris trichuria. Ascariasis is the most reported infection, with a prevalence ranging from 10.77% in Ethiopia to 57.14% in Malaysia, and is correlated with stunting (OR 2.17 (95% CI 1.14, 4.13), p = 0.02). Giardiasis is the second most reported infection, with a prevalence ranging from 4.43% in Ethiopia to 66.33% in the Central African Republic, and is related to an increased risk of stunting (OR 2.34 (95% CI 1.07, 5.10), p = 0.03)), wasting (OR 2.90 (95% CI 1.12, 7.49, p = 0.03)), and being underweight (OR 1.53 (95% CI 1.02, 2.29, p = 0.04)). The third and fourth most prevalent infections are T. trichiura and hookworm infections. Intestinal parasitic infections can occur very early in life and cause significant growth retardation. It is important to understand the prevalence and effects of infection based on the parasite species in order to implement therapeutic interventions and prevention controls.

/pdf/intestinal-parasitic-infection-and-nutritional-status-in-3gfokd12.pdf

Intestinal Parasitic Infection and Nutritional Status in Children under Five Years Old: A Systematic Review

Background 
Intestinal parasitoses are a major concern for public health, especially in children from middle and low-income populations of tropical and subtropical areas. We examined the presence and co-infection of parasites in humans as well as parasitic environmental contamination in Puerto Iguazu, Argentina. We explored the environmental and socio-demographic characteristics of the persistence of parasites in children and their environment.


Methodology/Principal findings 
This cross-section survey was conducted among children population comprised into the area of the public health care centers of Iguazu during June 2013 to May 2016. Copro-parasitological status of 483 asymptomatic children was assessed. Simultaneously, a design-based sampling of 744 soil samples and 530 dog feces was used for characterize the environmental contamination. The 71.5% of these sites were contaminated. Sixteen genera were detected in the environment being hookworms (62.0%) the main pathogens group detected followed by Toxocara spp (16.3%), Trichuris spp (15.2%) and Giardia (6.5%). Total children prevalence raised 58.8%, detecting twelve genera of parasite with Giardia intestinalis as the most prevalent pathogen (29.0%) followed by Enterobius vermicularis (23.0%), Hymenolepis nana (12.4%) and hookworms (4.4%). Through questionnaires and census data, we characterized the socio-demographics conditions at an individual, family and neighborhood levels. A multi-level analysis including environmental contamination data showed that the ´presence of parasites´ was mostly determined by individual (e.g. age, playing habits, previous treatment) and household level (e.g. UBN, WASH, mother's literacy) determinants. Remarkably, to define the level of ‘parasite co-infection’, besides individual and household characteristics, environmental factors at a neighborhood level were important.


Conclusion/Significance 
Our work represents the major survey of intestinal parasites in human and environmental samples developed in the region. High prevalence was detected in the children population as well as in their environment. This work shows the importance of considering and promoting multi-level actions over the identified determinants to face this public health problem from integrative approaches.

/pdf/environmental-and-socio-demographic-individual-family-and-31p4z3z770.pdf

Environmental and socio-demographic individual, family and neighborhood factors associated with children intestinal parasitoses at Iguazú, in the subtropical northern border of Argentina.

Transcriptional profiling of Giardia intestinalis in response to oxidative stress.

Summary A cross-sectional study was conducted on a randomised sample of 405 children aged 6–71 months in Brazil to investigate the association between nutritional status, environmental and socio-economic factors and Giardia lamblia infection. Data collection entailed an interview, anthropometric measurements and the collection of faeces and venous blood samples. The analysis was performed using multivariate logistic regression. The prevalence rate for G. lamblia was 26.3%. Nutritional status evaluation showed that 7.9% of the children had chronic malnutrition and 11.1% had acute malnutrition. The risk factors associated with infection by G. lamblia were an age of 2 years or older [odds ratio (OR) = 2.4], living in a two-bedroom house or smaller (OR = 2.3), living among a family of five or more people (OR = 2.4) and living in a house without access to a sewerage system (OR = 2.1). Non-participation in the social service programme was associated with a lower risk of infection (OR = 0.2). The model adjusted for age, including only biochemical and nutritional variables, showed weak associations with G. lamblia infection for two variables: inadequate animal protein intake according to the Dietary Reference Intake recommendation and low haemoglobin concentration. The sociodemographic and environmental risk factors classically described were associated with G. lamblia infection, but nutritional variables were only weakly associated with it.

Association between nutritional status, environmental and socio-economic factors and Giardia lamblia infections among children aged 6–71 months in Brazil

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Association between nutritional status, environmental and socio-economic factors and Giardia lamblia infections among children aged 6–71 months in Brazil