Ascariasis: nutritional implications

Neglected infections of poverty in the United States of America

In the United States, there is a largely hidden burden of diseases caused by a group of chronic and debilitating parasitic, bacterial, and congenital infections known as the neglected infections of poverty. Like their neglected tropical disease counterparts in developing countries, the neglected infections of poverty in the US disproportionately affect impoverished and under-represented minority populations. The major neglected infections include the helminth infections, toxocariasis, strongyloidiasis, ascariasis, and cysticercosis; the intestinal protozoan infection trichomoniasis; some zoonotic bacterial infections, including leptospirosis; the vector-borne infections Chagas disease, leishmaniasis, trench fever, and dengue fever; and the congenital infections cytomegalovirus (CMV), toxoplasmosis, and syphilis. These diseases occur predominantly in people of color living in the Mississippi Delta and elsewhere in the American South, in disadvantaged urban areas, and in the US-Mexico borderlands, as well as in certain immigrant populations and disadvantaged white populations living in Appalachia. Preliminary disease burden estimates of the neglected infections of poverty indicate that tens of thousands, or in some cases, hundreds of thousands of poor Americans harbor these chronic infections, which represent some of the greatest health disparities in the United States. Specific policy recommendations include active surveillance (including newborn screening) to ascertain accurate population-based estimates of disease burden; epidemiological studies to determine the extent of autochthonous transmission of Chagas disease and other infections; mass or targeted treatments; vector control; and research and development for new control tools including improved diagnostics and accelerated development of a vaccine to prevent congenital CMV infection and congenital toxoplasmosis.

Vitamin A status and hemoglobin concentrations are improved in Indonesian children with vitamin A and deworming interventions

OBJECTIVE

Anemia is a major public health problem caused by multiple factors. Vitamin A (VA) depletion can affect hemoglobin concentration (Hb). This study investigated the improvement in Hb and VA status in preschool Indonesian children following supplementation with 210 micromol VA and deworming with 400 mg albendazole.

SUBJECTS AND DESIGN

Indonesian children (n = 131) infected with Ascaris lumbricoides and/or Trichuris trichiura were enrolled. The children were grouped by length of time since receiving 210 micromol VA through the local health system. Group 1 (VA administered > or = 4 month before baseline) included 51 children with Ascaris and 29 children with Trichuris. Group 2 had received VA < or = 1 month of baseline from the local health post and included 51 children.

INTERVENTION AND METHODS

Immediately following baseline Hb and VA status assessment (modified relative dose response (MRDR) test), Group 1 children were given 210 micromol VA and 400 mg albendazole. Group 2 were randomized to be dewormed either 1 week before, at the same time or 1 week after baseline MRDR and Hb measures. Follow-up assessment was 3-4 weeks after baseline.

RESULTS

VA status in Group 1 significantly improved in children with either Ascaris (P < 0.0001) or Trichuris (P = 0.028). Although the prevalence of anemia declined, the improvement in Hb was not significant (P = 0.08). In Group 2, improvement in VA status from the VA delivered through the public health system was maintained for more than 1 month. Hb improved (P = 0.0037) and this improvement appeared to be associated with the length of time between deworming and follow-up assessments.

CONCLUSION

Public health supplementation programs to improve VA status may also increase Hb concentrations and decrease anemia prevalence, especially when linked to deworming.

SPONSORSHIP

These studies were supported by the Thrasher Research Fund, SmithKline Beecham and Hatch-Wisconsin Agricultural Experiment Station number WIS04533.

Low dose daily iron supplementation improves iron status and appetite but not anemia, whereas quarterly anthelminthic treatment improves growth, appetite and anemia in Zanzibari preschool children

Iron deficiency and helminth infections are two common conditions of children in developing countries. The consequences of helminth infection in young children are not well described, and the efficacy of low dose iron supplementation is not well documented in malaria-endemic settings. A 12-mo randomized, placebo controlled, double-blind trial of 10 mg daily iron and/or mebendazole (500 mg) every 3 mo was conducted in a community-based sample of 459 Zanzibari children age 6-71 mo with hemoglobin > 70 g/L at baseline. The trial was designed to examine treatment effects on growth, anemia and appetite in two age subgroups. Iron did not affect growth retardation, hemoglobin concentration or mild or moderate anemia (hemoglobin < 110 g/L or < 90 g/L, respectively), but iron significantly improved serum ferritin and erythrocyte protoporphyrin. Mebendazole significantly reduced wasting malnutrition. but only in children <30 mo old. The adjusted odds ratios (AORs) for mebendazole in this age group were 0.38 (95% CI: 0.16, 0.90) for weight-for-height less than -1 Z-score and 0.29 (0.09, 0.91) for small arm circumference. In children <24 mo old, mebendazole also reduced moderate anemia (AOR: 0.41, 0.18, 0.94). Both iron and mebendazole improved children's appetite, according to mothers' report. In this study, iron's effect on anemia was limited, likely constrained by infection, inflammation and perhaps other nutrient deficiencies. Mebendazole treatment caused unexpected and significant reductions in wasting malnutrition and anemia in very young children with light infections. We hypothesize that incident helminth infections may stimulate inflammatory immune responses in young children, with deleterious effects on protein metabolism and erythropoiesis.

Parasitic infection and chronic energy deficiency in adults

Interactions between infection and nutrition have been well recognized for several years now since they contribute directly to the health of individuals and communities. Malnourished individuals are specially prone to developing infections while infections themselves can lead to profound changes in the nutritional status of the individual. Health workers in developing countries in the tropics have long recognized the mutually aggravating interactions of malnutrition and infection. The importance of this synergistic relationship between infection and nu-tritional status has been studied extensively in the case of young children. The nutritional status of a young child is a critical determinant of both c morbidity and mortality resulting from a wide range of infections: bacterial, viral, or parasitic. Chandra (1983), in his review on the relationship of nutrition, immunity and infection has categorized the wide range of infectious agents (bacterial, viral, fungal and parasitic) into those that are definitely, variably or minimally influenced by the nutritional status of the child.

Ascariasis and childhood malnutrition

The present review will examine epidemiological perspectives and be confined mainly to the results of those field studies published since 1975 in order to provide concrete scientific evidence of the effect of ascariasis on childhood malnutrition, particularly on growth. The field studies were done in many developing countries from Africa, Asia and Latin America, using cross-sectional and intervention studies in which anthelmintics were employed, with different dosing frequency and follow-up periods ranging from 33 days to 2 years. In general, a better nutritional status in terms of growth, lactose tolerance, vitamins A and C, and albumin levels were observed among Ascaris-free or treated than among Ascaris-infected or untreated children even in cross-sectional or non-randomized studies. More importantly, the improvement in weight or height after chemotherapeutic treatment was found to be significant particularly in those randomized controlled studies with an initially high prevalence of ascariasis and malnutrition, a low prevalence of other intestinal parasites, repetitive and regular treatments of children with tetramisole, levamisole or pyrantel, within a period of 12 or 24 months. Reasons for failures to detect improved growth in some studies are provided. This review strongly indicates that A. lumbricoides infection definitely retards childhood growth.

Contributions of ascariasis to poor nutritional status in children from Chiriqui Province, Republic of Panama

Relationships between ascariasis and lactose digestion and between ascariasis and food transit time from mouth to caecum were investigated in young children from Chiriqui Province, Republic of Panama. The breath hydrogen method was used in both studies. Ascaris-infected children showed a significantly poorer degree of lactose digestion following a test oral load than uninfected children. Recovery of the capacity of the children to digest lactose was still not fully complete for at least 3 weeks following anthelmintic treatment. On average, the mouth-to-caecum transit time was similar in infected and uninfected children, but among the Ascaris-infected children the transit time tended to be shorter in relation to the intensity of infection. Evidence from a cross-sectional survey indicated that ascariasis was significantly associated with reduced plasma vitamin A and carotenoid concentrations. This relationship remained after controlling for a range of socio-economic variables. Ascaris-infected children were frequently found to have lower haematocrits and blood haemoglobin concentrations than uninfected children, but these relationships could not be attributed to ascariasis alone.

The impact of host nutrition on gastrointestinal helminth populations

Malnutrition and helminth infection are amongst the most prevalent chronic conditions affecting human health globally. It is estimated that parasitic helminths infect more than 1 billion people, and that more than 2 million clinical cases occur each year (Peters, 1978; Walsh, 1984). Estimates of the incidence of clinical malnutrition suggest that between 5 and 8 million cases occur annually. In many parts of the developing world malnutrition and infection conjointly are the most serious health problem in children, acting as primary or more often as secondary factors in mortality (Puffer & Serrano, 1973). The impact on health is exacerbated because both conditions are chronic, are most common in growing children and, most importantly, tend to occur together in the same individuals (Pawlowski, 1984; Chandra & Newberne, 1977).

The significance of parasitic infections in terms of clinical disease: a personal view

Throughout the world, infection with parasites is extremely common. Prevalence is highest in the warm countries of the tropics and subtropics, but infection occurs in all climatic zones. The figures usually quoted for the prevalence of specific parasites attain values akin to those used to describe astronomical distances. The World Health Organization (1985) estimated that some 2582 million of the earth's inhabitants live in areas where they risk contracting malaria and that many – in Africa south of the Sahara alone probably 200 million – remain chronically and persistently infected. Estimates for other parasites are similarly impressive; 600 million at risk of infection with schistosomiasis, with some 200 million actually infected; 900 million exposed to lymphatic filarial parasites, with some 90 million currently infected; for onchocerciasis, probably some 40 million cases spread throughout Africa, Central and South America and the Eastern mediterranean. Yet, impressive as these estimates may be, they are dwarfed by those for some intestinal helminths. Recent assessments suggest that 1 person in 4 of the world's population carriesAscaris lumbricoides(Schultz, 1982), while the same proportion is believed to be infected with one or other of the hookworms (Gilman, 1982).

Epidemiological aspects of Trichuris and trichuriasis in Caribbean communities

The review argues for a reappraisal of the health significance of the human whipworm, Trichuris trichiura. Infections with this geohelminth are at least as prevalent as Ascaris lumbricoides in many localities, and are associated with significant morbidity. Infection may result in severe trichuriasis syndrome or, more frequently, in a chronic colitis associated with growth stunting. Under-reporting of the chronic manifestations of disease has resulted in a gross under-estimation of the health impact of trichuriasis. Furthermore, estimation of the population dynamical parameters of T. trichiura transmission suggests that whipworm infections are intrinsically more resistant to control than those of other common geohelminths. A major determinant of the transmission dynamics and morbidity characteristics of this helminthiasis is the aggregation of worm burdens in certain predisposed individuals and age groups. It is suggested that improved understanding of the factors generating this distribution of infection intensity is a pre-requisite for effective control of both infection and morbidity.

Nutritional aspects of infection

Current knowledge is examined about the means whereby ascariasis, hookworm disease, strongyloidiasis and trichuriasis may contribute to the aetiology of human malnutrition. Results from experiments with related parasites in the laboratory have demonstrated the role of gastrointestinal helminthiases in animal malnutrition. Some evidence shows that in children, infection with the intestinal stages of Ascaris lumbricoides is associated with reduced growth rate, disturbed nitrogen balance, malabsorption of vitamin A, abnormal fat digestion, lactose maldigestion and an increased intestinal transit time. The main impact of hookworm infection is its relationship with iron-deficiency anaemia which may have effects at the community level as regards work and productivity in adults and learning and school performance in children. More research is needed to extend knowledge of the nutritional impact of ascariasis and hookworm disease in order to establish their public health significance. Research is needed also to identify the range of nutritional effects on man that occur as a result of trichuriasis and strongyloidiasis. The significance of less prevalent and more localized gastrointestinal helminthiases should not be ignored.