Nutritional implications of parasitic infections

Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes

BACKGROUND

Whether Plasmodium falciparum, the agent of human malaria responsible for over a million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved. Understanding the evolutionary forces responsible for the maintenance of susceptibility and refractory alleles in natural mosquito populations is critical for understanding malaria transmission dynamics.

METHODS

In natural mosquito populations, Plasmodium fitness costs may only be expressed in combination with other environmental stress factors hence this hypothesis was tested experimentally. Wild-caught blood-fed Anopheles gambiae s.s. females of the M and S molecular form from an area endemic for malaria in Mali, West Africa, were brought to the laboratory and submitted to a 7-day period of mild hydric stress or kept with water ad-libitum. At the end of this experiment all females were submitted to intense desiccation until death. The survival of all females throughout both stress episodes, as well as their body size and infection status was recorded. The importance of stress, body size and molecular form on infection prevalence and female survival was investigated using Logistic Regression and Proportional-Hazard analysis.

RESULTS

Females subjected to mild stress exhibited patterns of survival and prevalence of infection compatible with increased parasite-induced mortality compared to non-stressed females. Fitness costs seemed to be linked to ookinetes and early oocyst development but not the presence of sporozoites. In addition, when females were subjected to intense desiccation stress, those carrying oocysts exhibited drastically reduced survival but those carrying sporozoites were unaffected. No significant differences in prevalence of infection and infection-induced mortality were found between the M and S molecular forms of Anopheles gambiae.

CONCLUSIONS

Because these results suggest that infected mosquitoes may incur fitness costs under natural-like conditions, they are particularly relevant to vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations.

Could giardiasis be a risk factor for low zinc status in schoolchildren from northwestern Mexico? A cross-sectional study with longitudinal follow-up

Background

Both giardiasis and zinc deficiency are serious health problems worldwide. In Mexico, the prevalence of G. intestinalis was estimated at 32% in 1994. It remains a health problem in northwestern Mexico. Recent surveys (1987, 1995, and 1999) reported zinc deficiency in the Mexican population. The association of giardiasis and malabsorption of micronutrients has been well documented, although the association with zinc remains controversial. This study investigated the association between giardiasis and zinc deficiency in schoolchildren from northwestern Mexico.

Methods

We combined a cross-sectional design with a longitudinal follow-up six months after parasite treatment. The baseline sample consisted of 114 schoolchildren (mean age 8.8 yr) from seven suburban public schools, grouped as Giardia-free (n = 65, 57%) and Giardia-infected (n = 49, 43%). Three stool analyses per child were done using Faust's method. Children with giardiasis received secnidazole. Serum zinc was determined by atomic absorption spectrophotometry. Height and weight were measured. Socioeconomic information was obtained in an oral questionnaire, and daily zinc intake was assessed using 24 hour-recalls. Pearson's correlation and ANCOVA and paired t-test analyses were used to determine the association between giardiasis and zinc status.

Results

Longitudinal analysis demonstrated a significant increase of the mean serum zinc levels in the Giardia-infected group six months after treatment (13.78 vs. 19.24 μmol/L μmol/L; p = 0.001), although no difference was found between the Giardia-free and the Giardia-infected groups (p = 0.86) in the baseline analysis. Z scores for W/A and H/A were lower in the Giardia-infected than in the Giardia-free group (p < 0.05). No difference was observed in the socioeconomic characteristics and mean daily intakes of zinc between the groups (p > 0.05).

Conclusions

Giardiasis may be a risk factor for zinc deficiency in schoolchildren from northwestern Mexico.

Malnutrition and infection: an update

The original Scrimshaw, Taylor and Gordon conceptual framework for the interaction of nutrition and infection has well served the scientific community for almost half a century. At its core is the notion of synergistic (mutually reinforcing) and antagonistic (mutually nullifying) influences of the malnourished state on infectious conditions and vice versa. Research on a series of advancing fronts, however, has allowed the incorporation of both relevant public health issues (parasitosis, emerging infectious diseases, obesity and overweight, etc.) and advancing science (molecular immunology, oxidation biology, multiple micronutrient deficiencies, etc.). The present review is an interpretative update on close to 50 years of demographic and epidemiological evolution in the field of human nutrition and the implications for the interaction in the context of microbiological and immunological developments on the infectious side of the dialectic.

Continuity or discontinuity of the life-style in central Italy during the Roman Imperial Age-Early Middle Ages transition: diet, health, and behavior

Dento-alveolar pathologies and alterations (dental wear, caries, abscesses, ante mortem tooth loss (AMTL), calculus, hypoplastic defects, and chipping) and skeletal markers of health (cribra orbitalia and periostitis) were analyzed in two skeletal samples from the necropolises of Quadrella (I-IV c. AD) and Vicenne-Campochiaro (VII c. AD) in the Molise region of central Italy. The aim was to determine if the Roman Imperial Age-Early Middle Ages transition characterized by political, socioeconomic, and cultural transformations affected the biology of these populations, particularly their alimentation and health status. The frequencies of caries and AMTL, similar in the two samples, suggest a high consumption of carbohydrates. The higher levels of heavy wear, calculus, and interproximal chipping in the Vicenne population indicate a greater use of fibrous foods (both meat and others), in line with the dietary model of Germanic peoples. Health conditions do not appear to have been good in either period, as shown by the high frequencies of linear hypoplasia and the presence of cribra orbitalia and periostitis. The diet of the individuals buried with horses of the Vicenne population did not differ from that of the rest of the population, whereas there were evident differences in the use of the teeth for nonmasticatory activities among these individuals. Therefore, from the point of view of alimentation and health status, the profound socioeconomic and cultural transformations during the Late Antiquity-Early Middle Ages transition do not seem to have been translated into a true discontinuity of the two Molisan populations.

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.

Prevalence and intensity of intestinal parasitic infections in relation to nutritional status in Mexican schoolchildren

Undernutrition and intestinal parasitic infections affect childhood development and morbidity in many developing countries. Undernutrition may increase susceptibility to parasitic infections which in turn impair the nutritional status of the host. The relationship between intestinal parasitic infections and nutritional status in 400 Mexican schoolchildren was investigated. More than half of the children in the study showed intestinal parasites and polyparasitism. The prevalence of helminth infections was significantly higher in Oaxaca than in Sinaloa (P < 0.05). Z scores for weight-for-age (WA) and height-for-age (HA) were much lower in children of Oaxaca than in Sinaloa (P < 0.001). A significantly higher Z score for weight-for-height (WH), WA, and HA were found in non-infected versus infected children (P < 0.05). Higher prevalences of intestinal infections were found in children with lower HA and WA than in normally nourished children (P < 0.05). Higher intensities of Ascaris lumbricoides and Trichuris trichiura were found in the schoolchildren of Sinaloa than in Oaxaca (P < 0.01). Negative and significant associations were found between Hymenolepis nana and T. trichiura infection (eggs per gram) and nutritional status. Intestinal parasitic infections may be regarded as main risk factors associated with poor nutritional status in Mexican schoolchildren.

Dento-alveolar lesions and nutritional habits of a Roman Imperial age population (1st-4th c. AD): Quadrella (Molise, Italy)

The study of teeth is very important in archaeoanthropology for reconstruction of the nutritional habits and living conditions of past populations. We have analysed dental lesions of pathological (caries, abscesses and ante mortem tooth loss) and non-pathological origin (calculus), linear enamel hypoplasia and tooth wear in 67 adults from the Roman Imperial age necropolis (1st-4th c. AD) of Quadrella (Molise, Italy). The high frequency of caries (likely giving rise to the abscesses and ante mortem tooth loss), the abundant calculus and the low frequency of heavy wear are probably due to a limited use of hard fibrous foods and a high consumption of carbohydrates. The high frequency of linear enamel hypoplasia suggests metabolic problems during growth. Comparison of these data with those for two coeval Italian necropoleis near Rome (Latium), Isola Sacra and Lucus Feroniae, indicates poorer living conditions in the Quadrella population.

Gastrointestinal parasitic infection, anthropometrics, nutritional status, and physical work capacity in Colombian boys

This article tests the hypothesis that the presence of gastrointestinal parasites in Colombian boys is negatively associated with anthropometric characteristics, physical work capacity, blood hemoglobin (Hb) levels, and nutritional status. Anthropometric, Hb, &Vdot;O(2) max, and parasite load data were collected on 1,016 boys in Cali, Colombia. The boys were classified as lower socioeconomic class (SEC) from either urban or rural environments, and upper SEC from an urban environment. Sixty-three percent of the boys were infected with gastrointestinal parasites and, of the infected boys, 80-95% had light parasite loads. Parasites found included Necator americanus, Ascaris lumbricoides, Entamoeba histolytica, Trichuris trichiura, Giardia spp., and Enterobius vermicularis. Infected boys had significantly lower weight, stature, weight-for-height (among 6-9-year-old boys), Hb levels, and &Vdot;O(2) max (ANCOVA, controlling for age and SEC). In terms of nutritional status, infected boys were 1.47 times more likely to be classified as iron deficient than noninfected boys (chi-square, P < 0.001), and 1.61 times more likely to be classified as stunted (P < 0.001). Infection was not associated with wasting in any SEC group. In conclusion, light to moderate gastrointestinal parasite loads were associated with significantly lower weight, stature, weight-for-height (in 6-9-year-old boys), Hb levels, and &Vdot;O(2) max, and a significantly higher frequency of IDA and stunting. These data suggest that comprehensive analyses of the nutritional status of populations in regions endemic for parasitic infection should include testing for the presence of infection. Am. J. Hum. Biol. 11:763-771, 1999. Copyright 1999 Wiley-Liss, Inc.

Pathways to the impairment of human nutritional status by gastrointestinal pathogens

Gastrointestinal pathogens are of three varieties, those that can, and often do, take the life of the host, those that infect transiently and rarely are life-threatening, and those (parasites) that establish a relatively prolonged residence or colonization of the host's alimentary tract. In the case of the second form, if infections are recurrent, both catabolic effects during the episode and failure to digest foods and/or absorb nutrients results. Similarly, catabolic wastage through activation of the acute phase response, and interference with the host's acquisition of nutrients by maldigestion, malabsorption, intestinal losses and competition with the parasite burden can impair growth and nutrition with helminthic infections. Growth and nutrition with respect to all of the macronutrients and virtually all of the micronutrients have been documented to be adversely affected by gastrointestinal pathogens. For its burgeoning importance as a worldwide health problem, both with the HIV virus as a direct intestinal pathogen and with the opportunistic gut infections occurring in the immunocompromised host, AIDS represents the emerging context of the impairment of nutritional status by intestinal pathogens.

Modulation of calf immune responses by Ostertagia ostertagi: the effect of diet during trickle infection

The effects of Ostertagia ostertagi infection and diet on antibody responses to O. ostertagi third stage larval (L3) antigen and to an unrelated antigen, Keyhole Limpet Haemocyanin (KLH) were determined in calves experimentally infected with 3000 L3 on alternate days for 6 weeks. Calves were given one of two diets, and were either infected or not infected with O. ostertagi L3. The diets were either high (H) or low (L) in protein/energy and were within the range of normal husbandry practice in the UK. Both IgG1 and IgG2, but not IgA, responses to L3 antigen were increased in the L-diet compared with the H-diet. IgA responses to L3 antigen were not affected by dietary treatment. The effects of diet and infection on anti-KLH IgG1 were independent of each other; IgG1 anti-KLH responses were decreased by infection and by the L-diet compared with the H-diet. The data suggest that there is a strong interrelationship between diet and immunity during nematode infections.

Immune modulation by Ostertagia ostertagi and the effects of diet

IgG1 antibody responses to Ostertagia ostertagi third stage larvae (L3) and the third party antigen, keyhole limpet haemocyanin (KLH), and faecal egg counts were determined in calves infected with a single dose of O. ostertagi and in uninfected, pair-fed calves. The infected and uninfected calves were given diets either high (H) or low (L) in protein and energy. The diets were within the normal range of husbandry practice in the UK. IgG1 antibody responses to L3 antigen were significantly greater from 6 weeks post-infection in infected calves given the L diet than in infected calves given the H diet (P less than 0.05). The effects of diet and infection on anti-KLH IgG1 responses were independent of each other. IgG1 responses to KLH were decreased by infection and by the L diet compared with the H diet.

[Interrelation of parasitic diseases and hypovitaminosis A. Schistosoma mansoni infection and the serum level of retinol in the population of an endemic area of Minas Gerais (Brazil)]

The interrelation between schistosomiasis and the retinol blood levels was studied in a double blind method, by comparing the serum vitamin A of the infected and non-infected group of an endemic area of Schistosoma mansoni infection. The infected group was characterized by 106 parasitized persons in the intestinal and hepatointestinal forms, who eliminated less than 500 eggs/gram of feces (Modified Kato's method); the non-infected group was characterized by 112 inhabitants of this endemic area without eggs in the stools and presenting negative intradermal reactions, and absence of previous specific treatment. The blood levels of retinol was determinated using trifluoracetic acid method, regarding the normal levels > 20,0mg/100ml. The results of this study point out the absence of correlation between S. mansoni infection and blood levels of vitamin A.

Comparisons of Heligmosomoides polygyrus primary infection in protein-deficient and well-nourished mice

Primary infections of Heligmosomoides polygyrus were studied in adult male CD1 mice fed on isoenergetic synthetic diets containing either 2% or 20% protein (casein). A slight reduction in food intake was observed during infection, and this was unaffected by diet. Protein deficiency was also found to have no effect upon worm establishment. Evidence was found, though, to suggest that the worms have a more severe effect upon the host in protein-deficient mice. Hypoalbuminaemia was observed due to diet and also infection, and this was synergistic. There was an increase in non-albumin plasma protein during infection which was not effected by diet. The circulating urea concentration was reduced during protein deficiency, as was the level of essential amino acids, but non-essential amino acid levels were raised. An increase in the levels of urea and essential amino acids was observed at day 4 of infection in mice on the 20% diet, but not on the 2% diet. Splenic atrophy occurred during infection, but the splanomegaly that occurred early during infection was proportionally greater in protein-deficient mice. These results are discussed in terms of the pathophysiology of both protein deficiency and infection, and comparisons are made with human malnutrition syndromes.

Giardiasis and the nutritional status of Zimbabwean schoolchildren

Stool specimens, obtained from 1813 schoolchildren from communal lands, commercial farms and urban areas in Zimbabwe, were examined for helminth and protozoan parasites. The findings were collated with anthropometric data on the same children to investigate the relationship between intestinal parasitism and nutritional status. Protozoan infections were common with Giardia lamblia being identified in 17.4% of children. There was a strong association between giardial infection and undernutrition, wasting and stunting in these children. There was no evidence of an association between helminth infection and undernutrition. In view of the known impairment of absorption from the gut in giardiasis, it is suggested that giardial infection may be an important factor contributing to the low nutritional status of many primary schoolchildren in Zimbabwe.

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.

Symptomatic differences between the sexes in rural Mexico

This paper addresses the problem of the differential presentation of illness by women and men in two Spiritualist temples and a physician's office situated in rural Mexico. Women's morbidity raises the broader anthropological questions of the interplay between symptomatic expression and women's unequal status in the social structure, their cognitive evaluation of specific life experiences, cultural etiological explanations and Western models of dysphoria. Symptoms presented by patients in different health care delivery sites are compared and case vignettes of patients' illnesses and attributions are presented to demonstrate the ways in which culturally constructed illness attributions and illness expressions comprise a somatic grammar for the articulation of experimental distress. The sick population is compared with a control group of healthy women to highlight the socio-cultural and psychosocial variables that promote illness in women from the same sociocultural strata of rural Mexico. Collective understandings of the role of life events and emotional expression in illness attributions legitimize somatization as a coping style under adverse existential conditions.

Owner survey of schistosomiasis mortality in Sudanese cattle

The estimated mortality in six- to 30-month-old cattle due to presumptive schistosomiasis was 7.1% for 155 interviews conducted in the White Nile Province in 1981. This mortality was higher for those herds under sedentary management than for migratory herds (9.4% vs 3.6%). The interviews were done through an informal visit technique by a veterinarian living in the area. The approximate number (19,000) of cattle over six months old estimated to be owned by those interviewed represents about 1% of the population in that province. The mortality from all causes in the six- to 30-month age group was 9.2%; in the over 30-month age group it was 1.8%. The authors judge the schistosomiasis mortality to be somewhat upwardly biased but the mortality due to all causes (9.2%) is consistent with the few reports available.

Nippostrongylus (Nematoda) in protein-malnourished rats: host mortality, morbidity and rehabilitation

The synergistic relationship between host nutrition and the effects of Nippostrongylus was investigated experimentally in rats fed a diet containing 1% (w/w) protein. Rats were infected with 10 doses of N. brasiliensis varying from 0.35 to 99 larvae/g and their daily food intake and weekly body mass were compared with those uninfected rats fed the same diet for a period of 9 weeks. The deterioration of the uninfected rats observed as a result of protein-energy malnutrition was found to be accelerated in a dose-dependent manner in the rats infected with N. brasiliensis. Analysis of food intake and body mass measurements demonstrated that this acceleration was related to a decrease in food intake and indicated a likely alteration in nutrient utilization, both of which were established by the end of the first week of the infection. Remission from the combined effects of malnutrition and infection was achieved by offering the rats a high-protein diet (20% w/w), whereupon rehabilitation was found to be complete within a period of 9 days. The implications of the results and the possible mechanisms involved in their generation are discussed in relation to the frequent coexistence of helminthiasis and malnutrition.