The impact of gastrointestinal parasites on protein-energy malnutrition in man

Prevalence of Intestinal Parasitic Infections, Genotypes, and Drug Susceptibility of Giardia lamblia among Preschool and School-Aged Children: A Cross-Sectional Study in Thailand

This study aimed to estimate the prevalence of intestinal parasitic infections in children and assess the drug susceptibility and genotypes/assemblages of Giardia lamblia in Thailand. This cross-sectional study was conducted among children aged 3-12 years in Sangkhlaburi District, Kanchanaburi Province, Thailand, between 25 September 2017 and 12 January 2018. Parasites were identified by stool microscopic examination, cultivation of intestinal parasitic protozoa, and enzyme-linked immunosorbent assay (ELISA). Drug susceptibility and genotype of G. lamblia were performed, respectively, by a resazurin assay and Triosephosphate Isomerase A and B genes using modified primers and probes. Among the 661 participants, 445 had an intestinal parasitic infection, resulting in a prevalence of 67.32% (95% CI: 63.60-70.89%). Blastocystis hominis was the most prevalent protozoa infection (49.32%; 95% CI: 45.44-53.22%), while Ascaris lumbricoides was the most prevalent helminth infection (0.91%; 95% CI: 0.33-1.97%). The prevalence of G. lamblia was 17.40%, with genotype B being the most common. According to our study, intestinal parasitic infections were commonly found in Thai children. G. lamblia was the most common pathogenic protozoa infection identified and exhibited less susceptibility to metronidazole compared to furazolidone and mebendazole.

Host manipulation by parasites through the lens of Niche Construction Theory

The effect of parasites on host behaviour is generally considered an example of the extended phenotype, implying that parasite genes alter host behaviour to benefit the parasite. While the extended phenotype is a valid perspective supported by empirical examples, this approach was proposed from an evolutionary perspective and it does not fully explain all processes that occur at ecological time scales. For instance, the roles of the ontogenetic environment, memory and learning in forming the host phenotype are not explicitly mentioned. Furthermore, the cumulative effect of diverse populations or communities of parasites on host phenotype cannot be attributed to a particular genotype, much less to a particular gene. Building on the idea that the behaviour of a host is the result of a complex process, which certainly goes beyond a specific parasite gene, we use Niche Construction Theory to describe certain systems that are not generally the main focus in the extended phenotype (EP) model. We introduce three niche construction models with corresponding empirical examples that capture the diversity and complexity of host-parasite interactions, providing predictions that simpler models cannot generate. We hope that this novel perspective will inspire further research on the topic, given the impact of ecological factors on both short-, and long-term effects of parasitism.

Effect of anthelmintic treatment on serum free IGF-1 and IGFBP-3: a cluster-randomized-controlled trial in Indonesia

In children, soil-transmitted helminth infections have been linked to poor nutritional status and growth retardation in association with lower levels of IGF-1. In adults, IGF-1 has an anabolic and metabolic function and is related to nutritional status. Here, we assessed the impact of helminth infection on free IGF-1 and its major binding protein, IGFBP-3, in adults. The levels of IGF-1 and IGFBP3 were measured in 1669 subjects aged ≥ 16 years, before and after receiving four rounds of albendazole 400 mg/day or matching placebo for three consecutive days. Helminth infection status was assessed by microscopy (Kato-Katz) and PCR. Serum free IGF-1 level was significantly lower in helminth-infected subjects [mean difference and 95% CI − 0.068 (− 0.103; − 0.033), P < 0.001 after adjustment for age, sex, body mass index, and fasting insulin level]. There was no difference in IGFBP-3 level between helminth infected versus non-infected subjects. In the whole study population, albendazole treatment significantly increased serum free IGF-1 level [estimate and 95% CI 0.031 (0.004; − 0.057), P = 0.024] whereas no effect was found on the IGFBP-3 level. Our study showed that helminth infection in adults is associated with lower free IGF-1 levels but not with IGFBP-3 and albendazole treatment significantly increases free IGF-1 levels in the study population.

Clinical Trial Registration: https://www.isrctn.com/ISRCTN75636394.

Effects of Iron Fortification in a School Feeding Scheme and Anthelmintic Therapy on the Iron Status and Growth of Six- to Eight-Year-Old Schoolchildren

The effect of iron fortification of soup in a school feeding scheme (20 mg iron and 100 mg vitamin C per portion) and anthelmintic therapy on haematological and iron status and on growth was studied in 179 schoolchildren age six to eight years. Measurements were performed before and at the end of a six-month intervention and repeated five months later. In children with low baseline iron stores (serum ferritin <20 μg/L), iron fortification was associated with increases in haemoglobin (p <.05), mean corpuscular volume (p <.01), and serum ferritin (p<.0001), compared with children who received unfortified soup. Significant positive effects of the anthelmintic therapy on haemoglobin concentrations (p < .05) and height-for-age Z scores (p<.01) were found. Children with adequate baseline iron stores showed smaller but similar changes.

Environmental enteric dysfunction: an overview

BACKGROUND

Environmental enteric dysfunction (EED) refers to an incompletely defined syndrome of inflammation, reduced absorptive capacity, and reduced barrier function in the small intestine. It is widespread among children and adults in low- and middle-income countries. Understanding of EED and its possible consequences for health is currently limited.

OBJECTIVE

A narrative review of the current understanding of EED: epidemiology, pathogenesis, therapies, and relevance to child health.

METHODS

Searches for key papers and ongoing trials were conducted using PUBMED 1966-June 2014; ClinicalTrials.gov; the WHO Clinical Trials Registry; the Cochrane Library; hand searches of the references of retrieved literature; discussions with experts; and personal experience from the field.

RESULTS

EED is established during infancy and is associated with poor sanitation, certain gut infections, and micronutrient deficiencies. Helicobacter pylori infection, small intestinal bacterial overgrowth (SIBO), abnormal gut microbiota, undernutrition, and toxins may all play a role. EED is usually asymptomatic, but it is important due to its association with stunting. Diagnosis is frequently by the dual sugar absorption test, although other biomarkers are emerging. EED may partly explain the reduced efficacy of oral vaccines in low- and middle-income countries and the increased risk of serious infection seen in children with undernutrition.

CONCLUSIONS

Despite its potentially significant impacts, it is currently unclear exactly what causes EED and how it can be treated or prevented. Ongoing trials involve nutritional supplements, water and sanitation interventions, and immunomodulators. Further research is needed to better understand this condition, which is of likely crucial importance for child health and development in low- and middle-income settings.

Evaluation of biochemical, hematological and parasitological parameters of protein-deficient hamsters infected with Ancylostoma ceylanicum

BACKGROUND

Hookworms infect millions of people worldwide and can cause severe clinical symptoms in their hosts. Prospective cohort studies in Brazil show high rates of hookworm reinfection in malnourished children compared to well-nourished children, despite previous treatment. Additionally, soil-transmitted helminth (STH) infections can worsen the nutritional status of affected populations. Therefore, this study aims to clarify the effects of host malnutrition during Ancylostoma ceylanicum infection and how this infection affects host physiological parameters using a hamster model.

METHODOLOGY/PRINCIPAL FINDINGS

Hamsters were divided into four experimental groups: normal diet or low-protein diet (also referred to as "malnourished") and A. ceylanicum infection or no infection. More severe pathogenesis was observed in the infected malnourished group, as demonstrated by significant decreases in the hemoglobin concentration, erythrocyte number and packed-cell volume compared to the non-infected malnourished group. Greater numbers of adult parasites and eggs were observed in the malnourished group compared to the control group; however, the oviposition rate was lower in the malnourished group. In general, greater values of total lipids were observed in malnourished animals compared to control animals, including lipids excreted in the stool.

CONCLUSIONS

In this work, we have demonstrated that animals fed an isocaloric low-protein diet presented more severe pathogenesis when infected with A. ceylanicum. The increased lipid concentration in the liver and blood is related to the conversion of the excess carbohydrate into fatty acids that increase the concentration of triglycerides in general. Triglycerides were excreted in the feces, indicating that infection associated with malnutrition caused a greater loss of these molecules for this group of animals and confirming the hypothesis that both nutrition and infection are responsible for the malabsorption syndrome. Taken together, the results found in this work confirm the hypothesis that the nutritional condition of the host greatly influences the course of the infection.

Antiparasitic drugs for paediatrics: systematic review, formulations, pharmacokinetics, safety, efficacy and implications for control

Drug development for paediatric applications entails a number of challenges, such as the wide age spectrum covered - from birth to adolescence - and developmental changes in physiology during biological maturation that influence the efficacy and toxicity of drugs. Safe and efficacious antiparasitic drugs for children are of pivotal importance given the large proportion of burden attributable to parasitic diseases in this age group, and growing efforts to administer, as widely as possible, antiparasitic drugs to at-risk populations, such as infants and school-aged children, often without prior diagnosis. The purpose of this review is to investigate whether antiparasitic drugs have been adequately studied for use in paediatrics. We approached this issue through a systematic review using PubMed and the Cochrane Central Register of Trials covering a period of 10 years and 8 months until the end of August 2010 to identify trials that investigated efficacy, safety and pharmacokinetic (PK) parameters of antiparasitic drugs for paediatrics. Overall, 269 clinical drug trials and 17 PK studies met our inclusion criteria. Antimalarial drugs were the most commonly studied medicines (82·6%). Most trials were carried out in Africa and children aged 2-11 years were the age group most often investigated. Additionally, we critically examined available drug formulations for anthelminthics and identified a number of shortcomings that are discussed. Finally, we shed new light on current proposals to expand 'preventive chemotherapy' to preschool-aged children and emphasise that new research, including risk-benefit analyses, are needed before such a strategy can be adopted more widely.

Neglected diseases of neglected populations: thinking to reshape the determinants of health in Latin America and the Caribbean

BACKGROUND

People living in poverty throughout the developing world are heavily burdened with neglected communicable diseases and often marginalized by the health sector. These diseases are currently referred to as Neglected Diseases of Neglected Populations. The neglected diseases create social and financial burdens to the individual, the family, the community, and the nation.

DISCUSSION

Numerous studies of successful individual interventions to manage communicable disease determinants in various types of communities have been published, but few have applied multiple interventions in an integrated, coordinated manner. We have identified a series of successful interventions and developed three hypothetical scenarios where such interventions could be applied in an integrated, multi-disease, inter-programmatic, and/or inter-sectoral approach for prevention and control of neglected diseases in three different populations: a slum, an indigenous community, and a city with a mix of populations.

SUMMARY

The objective of this paper is to identify new opportunities to address neglected diseases, improve community health and promote sustainable development in neglected populations by highlighting examples of key risk and protective factors for neglected diseases which can be managed and implemented through multi-disease-based, integrated, inter-programmatic, and/or inter-sectoral approaches. Based on a literature review, analysis and development of scenarios we visualize how multiple interventions could manage multiple disease problems and propose these as possible strategies to be tested. We seek to stimulate intra- and inter-sectoral dialogue which will help in the construction of new strategies for neglected diseases (particularly for the parasitic diseases) which could benefit the poor and marginalized based on the principle of sustainability and understanding of key determinants of health, and lead to the establishment of pilot projects and activities which can contribute to the achievement of the Millennium Development Goals.

Malnutrition and susceptibility to enteroparasites: reinfection rates after mass chemotherapy

The evidence that relates malnutrition to enteroparasite infections arises from studies that demonstrate the improvement of nutritional indicators after antiparasitism treatment. However, the role of malnutrition as an aggravating factor to the susceptibility to enteroparasite infections is still not fully understood. We investigated the correlation between malnutrition and enteroparasite infection after mass chemotherapy, in a poor city of São Paulo State, Brazil. The sample comprised 759 children between 1 and 10 years of age of whom 585 were followed up for a period of 1 year and periodically assessed for reinfection with enteroparasites. One year of follow-up after mass chemotherapy demonstrated that 38 of the undernourished children were reinfected with enteroparasites, as compared with 25 of the eutrophic children (P = 0.033). The survival multivariate analysis demonstrated that, after controlling for the potential confounding variables, maternal literacy and per capita income rate, malnutrition was associated with susceptibility to reinfection (P = 0.13). We demonstrate that, although maternal literacy and per capita income rate are indeed confounding variables, malnutrition contributes to an increase in the risk of enteroparasite infections.

Gastrointestinal nematodes, nutrition and immunity: breaking the negative spiral

Nutritionists have long understood that intestinal nematode parasites have deleterious effects on host nutritional status, but only recently has the importance of malnutrition as a predisposing factor to intestinal nematodes been recognized. Here we review experimental and field studies on the effects of protein, energy, zinc, vitamin A, and iron deficiencies on gastrointestinal (GI) nematodes of humans, livestock, and laboratory rodents, and draw certain conclusions about the state of our current understanding. In general, malnutrition promotes the establishment, survival, and fecundity of these parasites, but the magnitude of the effect depends on factors such as host species, parasite species, particular infection protocol used, magnitude of the infection, severity of the nutritional deficiency, and presence of single or multiple infections and single or multiple nutritional deficiencies. We highlight the Th2 arm of the immune system as a component of primary importance in the association between malnutrition and GI nematode infections. We summarize what is known about underlying mechanisms that may account for the observed patterns. Finally, we suggest future research directions.

Anthelmintic treatment of rural Bangladeshi children: effect on host physiology, growth, and biochemical status

BACKGROUND

The effect of helminth infestation on the nutrition, growth, and physiology of the host is still poorly understood. Anthelmintic treatment of children in developing countries has had varying success in terms of growth improvements.

OBJECTIVE

The objective of this study was to assess the effect of regular deworming on child growth, physiology, and biochemical status.

DESIGN

The study was a 12-mo longitudinal intervention in 123 Bangladeshi children aged 2-5 y. Treatment (mebendazole) or placebo tablets were administered every 2 mo for 8 mo and again at 12 mo. Weight, height, midupper arm circumference, intestinal permeability, plasma albumin, alpha(1)-antichymotrypsin, and total protein concentration were assessed every 2 mo.

RESULTS

Treatment with mebendazole reduced the prevalence of Ascaris lumbricoides from 78% to 8%, of Trichuris trichiura from 65% to 9%, and of hookworm from 4% to 0%. There was no significant difference in the growth of treated children compared with those given placebo tablets. No changes in intestinal permeability or plasma albumin were observed after deworming. Significant decreases in total protein (P<0.001) and alpha(1)-antichymotrypsin (P<0.001) were observed in the treatment group, indicating possible reductions in inflammation and immunoglobulin concentration after deworming. A significant increase in the prevalence of Giardia intestinalis (from 4% to 49%) in the treatment group was associated with a short-term reduction in weight (P = 0.02) and higher intestinal permeability (P <0.001) in infected subjects. No long-term effects of G. intestinalis on growth were observed.

CONCLUSION

Low-intensity helminth infections, predominantly of A. lumbricoides and T. trichiura, do not contribute significantly to the poor growth and biochemical status of rural Bangladeshi children.

Ascaris-Trichuris association and malnutrition in Brazilian children

This work was designed to evaluate the role of intestinal parasites on nutritional status in three rural areas of Brazil. A total of 520 children aged 1-12 years were studied through a questionnaire concerning housing, socio-economic conditions and a 24-h food intake recall. Measurements of weight and height were also performed, and three stool samples were collected on consecutive days for parasitological analysis. Scores of the standard deviation (z-scores) for the weight-for-height and height-for-age were used to characterise the growth profile. A high prevalence of intestinal parasites was detected, with Giardia lamblia (44%), Endolimax nana (43%), Ascaris lumbricoides (41%) and Trichuris trichiura (40%) being the most prevalent. Eleven per cent of the children were classified as showing stunting. Inadequate daily caloric intake was observed in 78% of the population and the proportion of those with inadequate protein intake was 34%. Logistic regression analysis was employed for the multivariate study. Stunting was significantly associated with estimators of low economic income, inadequate protein intake and polyparasitism, especially the association between Ascaris lumbricoides and Trichuris trichiura.

Impacting maternal and child nutrition in rural Vietnam: experiences of an American nurse-consultant

This article describes a pilot project undertaken by the author, her physician husband and a Vietnamese physician partner in a rural Vietnamese community on the Mekong Delta approximately 80 kilometers from Saigon. The project was focused on reducing malnutrition in a community of approximately 11,000 people. Successful steps were taken, based on earlier research, to help the members of this rural community to get involved in developing a solution for maternal and infant malnutrition in their community.

School performance, nutritional status and trichuriasis in Jamaican schoolchildren

Severe infections by the geohelminth Trichuris trichiura detrimentally affect young children's growth and development. There is concern that mild to moderate infections may affect older children's school performance and nutritional status. We therefore examined the relationship between varying intensities of infection and school achievement, attendance and nutritional status in 616 schoolchildren. A total of 409 children with Trichuris infection of intensities greater than 1200 eggs per gram of stool (epg) were first identified, then for every 2 infected children in a class, an uninfected child was selected. After controlling for socioeconomic status, gender, age, school and the presence of Ascaris infections, the uninfected children had higher reading and arithmetic scores than children with infections of more than 4000 epg and were taller than those with intensities greater than 2000 epg. However, there were no significant differences in spelling, school attendance and body mass index. Although a treatment trial is needed to determine causation, these results indicate that moderate levels of infection are associated with poor school achievement and growth.

Perceptions and treatment of intestinal worms in rural Bangladesh: local differences in knowledge and behaviour

A survey was conducted on 131 mothers in rural Bangladesh to examine knowledge and perceptions of helminth infection in relation to use of health facilities and treatment-seeking behaviour. Almost all respondents considered worms to be a cause of bad health and a high percentage of mothers had obtained deworming treatment for their children. However, marked differences were found in mothers' descriptions of the causes and prevention of helminth infection in two adjacent areas; Pullakandi and Shekpara. The discrepancies in biomedical knowledge corresponded with differences in treatment-seeking behaviour in the two areas. All households in the area had access to free deworming treatment provided by a health clinic, but this facility was predominantly used by women living nearby in Pullakandi. Because of the cultural and social constraints on female activities, women living further from the clinic, in Shekpara, preferred to send their husbands to a pharmacy in the nearby town to buy deworming treatment. As a consequence, these households were at a relative disadvantage in respect of the low exposure of women to health education and the greater financial cost of deworming treatment. The study highlights the influences of social and cultural factors on treatment-seeking behaviour, which in turn affect women's exposure to health education and biomedical knowledge of helminths. Further questions are raised, however, on the ability of women to implement preventive measures and the impact of health education on rates of parasitic infection.