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[Survey of parasitic prevalence in school-aged children in Guinea (1995)].

UNLABELLED: A national survey was carried out to assess the prevalence of helminth infections in all four geographical zones of Guinea (the four official names should be used. Guinée forestière, Haute Guinée, Moyenne Guinée and Basse Guinée) to provide information on which a school-based intervention program could be developed. The program, financed by the World Bank, would consist of vitamin supplementation, antihelmintic treatment and hygiene education. METHODS: The survey was conducted between April and June, 1995. Two prefectures (administrative areas) were selected to represent each zone, in each prefecture, one child between the age of 10 and 14 years old from each of 100 households was included in the study. Thus 800 children were enrolled. One fresh stool and one urine specimen per child were examined for the presence of parasites using the Kato-Katz method and routine microscopy. RESULTS: The following overall prevalences were obtained: bookworm (43.9%); Schistosoma mansoni (25%); S. haematobium (19.9%) Trichuris trichiura (13.5%); Ascaris lumbricoides (9.5%); Strongyloides stercoralis (6.4%) and Taenia spp (3.8%). More than 70% of the children were infected by at least one helminth. The majority (63%) of the infections were infections with only one parasite. Only 8% had three or more helminths. More boys than girls were infected (74.3% vs. 65.2%). Helminth infection was significantly associated with region, gender and school attendance as assessed by logistic regression analysis. The prevalence of Ascaris, S. mansoni and bookworm infections were higher in Guinée forestière than any other zone, although hookworm infections were common in all zones (prevalences of between 26% and 71%). The distribution of the other helminth infections differed substantially between the regions. Trichuris was most common in Conakry, Strongyloides in Boké, Taenia in Labé, and Schistosoma infections in both Haute Guinée and Guinée forestière. CONCLUSION: The prevalence of helminth infection in Guinea is high, and there is a regional distribution. Both these factors should be taken into account when planning the school-based supplementation, treatment and education intervention program.

Adolescent↗
PubMed1999

Evidence for an association between hookworm infection and cognitive function in Indonesian school children.

The association between helminth infection and cognitive and motor function was investigated in school-age children in Java, Indonesia. 432 children from 42 primary schools participated in the study. Children were stratified by age and sex into two age groups, 8-9 years and 11-13 years. Children infected with hookworm performed significantly worse than children without hookworm infection in 6 of the 14 cognitive or motor tests. After controlling for school (as a random effect) plus age, socio-economic status and parental education, sex, stunting (height-for-age < - 2sd), body mass index, haemoglobin concentration and the presence of A. lumbricoides and T. trichiura infections, infection with hookworm explained significantly lower scores on tests of Fluency (P < 0.01), Digit-Span Forwards (P < 0.01), Number Choice (P < 0.01), Picture Search (P < 0.03), Stroop Colour Word (P < 0.02) and Mazes (P < 0.001). In 4 of the 6-tests (Fluency, Number Choice, Picture Search and Mazes), there was a significant interaction between hookworm infection and age (P < 0.03), indicating that the association between hookworm and lower test scores increased with age. No associations were observed between hookworm infection and scores in tests of Digit-Span Backwards, Corsi-Block, Stroop Colour, Stroop Interference, Free Recall, Verbal Analogies, Bead Threading or the Pegboard (P > 0.05). Tests associated with helminths represented various functions of working memory. No significant associations between helminth infection and motor function were observed that could not be explained by chance. The results suggest that hookworm infection can have a significant adverse effect on children's working memory which may have consequences for a child's reasoning ability and reading comprehension. Although the results are only associational, the fact that differences in cognition were observed at baseline imply that preventing infection with helminths in school-age children could be of benefit.

Adolescent↗
PubMed1997

Relationships between soil-transmitted helminthiases and growth in urban slum schoolchildren in Ujung Pandang, Indonesia.

This study examined the relationship between intestinal helminthiases and growth in urban slum schoolchildren. Children (n = 330) who received single doses of either pyrantel, albendazole, or placebo at baseline and again at 6 months were followed and examined fully at 0, 3, 6, and 12 months for helminth infections and anthropometry. Results of treatments indicated that all groups reduced their prevalence and intensity toward the period of the study. Reductions in intensity of both infections in the treatment groups were observed large in 3 and 12 months, whereas at 6 months reached mostly the initial level of infection. There was no significant difference in growth changes between the dewormed (once and twice) and the placebo groups. However, after controlling for some potential confounding factors, there was a significant relationship between reduction of A. lumbricoides infection and height gain at 3 and 12 months (both P < 0.05). In addition, there was a significant association between reduction in T. trichiura infection and increased midarm circumference at 3 and 12 months (P < 0.002 and P < 0.08, respectively). We conclude that treatment of helminth infections in school-age children may improve growth in areas where malnutrition and helminth infections are prevalent.

Animals↗
PubMed2006

Are intestinal helminths risk factors for developing active tuberculosis?

OBJECTIVES: To determine the prevalence of intestinal helminth infections in active tuberculosis patients and their healthy household contacts and to assess its association with active TB in an area endemic for both types of infections. METHODS: Smear-positive pulmonary TB patients and healthy household contacts were tested for intestinal helminths using direct microscopy and the formol-ether concentration techniques. Three consecutive stool samples were examined before the start of TB chemotherapy. Sputum microscopy was done using the sodium hypochlorite concentration techniques. Participants were also tested for HIV by commercial sandwich enzyme linked immunosorbent assay. RESULTS: The study population consisted of 230 smear-positive TB patients and 510 healthy household contacts. The prevalence of intestinal helminths was 71% in patients and 36% in controls. HIV seroprevalence was significantly higher in patients than in controls (46.7%vs. 11.6%, P < 0.001). Conditional logistic regression analysis showed a strong association between TB and intestinal helminth infection (OR = 4.2, 95% CI 2.7-5.9, P < 0.001), and between TB and HIV infection (OR = 7.8, 95% CI 4.8-12.6, P < 0.0001). The odds of being a TB patient increased with the number of helminth species per person: in individuals with mono-infection it was 4.3 (95% CI 2.8-6.8); in people infected with two species was 4.7 (95% CI 2.5-8.7), and in patients infected with three or more helminths was 12.2 (3.9-52.6). CONCLUSION: Intestinal helminth infection may be one of the risk factors for the development of active pulmonary TB in addition to HIV infection. This finding may have important implications in the control of TB in helminth endemic areas of the world.

Adolescent↗
PubMed2005

Anemia, malaria and hookworm infections in a Vietnamese ethnic minority.

The aim of this study was to determine the prevalence of anemia and evaluate the relationship of malaria and helminth infections on anemia status in Phan Tien village, a mountainous ethnic minority community in southern Vietnam. This longitudinal study was performed from April 1997 to 2000 by measuring the hemoglobin concentration of 2,767 people who participated in six annual surveys at the end of the rainy seasons. Ferritin concentration was measured in 2000 to evaluate the proportion of iron deficiency anemia. The relation between malaria and intestinal helminth infections with anemia was investigated. Anemia was always over 43% and mainly associated with iron deficiency (80.1%). Using generalized estimating equations, a small but significant decline of the anemia prevalence was detected (OR: 0.805; p < 0.0001). Malaria was significantly associated with anemia (OR: 2.408; p = 0.0006). There was no significant effect of the control of intestinal helminth infections on the time course of anemia (95% CI: -0.1548 to 0.1651).

Adolescent↗
PubMed2006

Human schistosomiasis decreases immune responses to allergens and clinical manifestations of asthma.

Studies have demonstrated that people living in areas endemic for helminths have a decreased reactivity to skin prick tests to aeroallergens and milder forms of asthma. Hypotheses to explain the inverse correlation between helminth infections and atopy include competition between helminth-induced polyclonal IgE and aeroallergen-specific IgE for high-affinity receptors present on mast cells, increased number of regulatory T cells, and high levels of regulatory cytokines, such as IL-10, produced during helminthic infections. Indeed, cells from asthmatic individuals infected with Schistosoma mansoni produce lower levels of IL-5 than asthmatics free of infections. In contrast, IL-10 is more readily produced by allergen-stimulated cells from asthmatics who are infected and is detected only at low levels by cells from helminth-free asthmatics. It is well known that Th2 cytokines are involved in the pathogenesis of allergies and asthma, and some studies indicate that IL-10 is the key cytokine that inhibits the Th2-inflammatory response in allergy. In this chapter we will discuss the association between S. mansoni infection, atopy and severity of asthma and possible mechanisms by which individuals living in helminth endemic areas are protected against the development of allergies.

Allergens↗
PubMed1993

[The infection risk for dogs raised helminth-free in conventional conditions in an urban area].

The present investigations were carried out to clarify whether or not and to what extent helminth-free raised dogs acquire patent and impatent helminth infections when exposed to an urban area contaminated with dog faeces. Groups of each 3 bitches at an age of 3, 6 or 9 months were taken out to an urban area (with average dog density of 1.5 per ha) for 3 hours daily on 5 days per week for a period of 3 month. During the whole trial the bitches and puppies born during this period were maintained under conditions which excluded other infections than those acquired during exposure in the urban area. The examination of the animals had the following results: All 9 bitches remained coproscopically negative until the end of the trial. In these bitches neither intestinal stages nor somatic helminth larvae were found. Seven out of 45 puppies from these bitches shed Toxocara canis eggs with the faeces. Shedding of eggs began 21 to 28 days after birth. Eggs excretion in most cases was low (< 33 eggs per gram). In 12 puppies from 5 litters intestinal stages of T. canis were found with a maximum of 4 specimens per animal. In 9 puppies only male or female T. canis were found.

Animals↗
PubMed2002

Soil transmitted helminth (STH) infections in an indigenous community in Ortigueira, Paraná, Brazil and relationship with its nutritional status.

Within the frame of World Health Organisation (WHO) guidelines for the control of soil transmitted helminth (STH) infections, a baseline survey has been conducted in Queimadas Indian schoolchildren (group A) as compared with urban schoolchildren (group B), both located in Ortigueira, Paraná, Brazil, with the aim of orientating investigations. In an opportunistic study, the possible relationship between STH infection and nutritional status has been investigated. A total of 236 schoolchildren aged 5-15 years were enrolled, 100 in group A and 136 in group B. Prevalence of STH infections and heavy intensity infections were significantly higher in the group A (P < .001). A statistical significant correlation between stunting (Z-score < -2) and intensity of STH infections was noted. These results strongly suggested that mass treatment would be indicated in the indigenous community, possibly leading to improved nutritional status.

Adolescent↗
PubMed2006

[Social determinants, feeding practices and nutritional consequences of intestinal parasitism in young children].

INTRODUCTION: Studies on intestinal intestinal parasitism in children under 2 years of age have rarely been performed. The nutritional consequences and feasibility of parasite prevention justify the current study. OBJECTIVES: The study was undertaken with 3 goals: (1) to identify the prevalence of pathogenic intestinal parasites (PIP), (2) to determine the social factors, sanitary conditions and nutritional practices that predict PIP, and (3) to evaluate PIP effects on infant nutritional status. MATERIALS AND METHODS: All mothers with children under 18 months of age and living in an urban community of coastal Colombia were invited to participate in the PIP study. A fecal sample was obtained from each of 136 children; they represented 62% of the total 7-18 month-old population in the community. Presence of intestinal parasites was identified by direct microscopy and confirmed by a concentration test (Ritchie-Frick procedure). Logistic regressions were used to predict presence of PIP. The Z scores of length-for-age (< -2 SD-chronic malnutrition) and weight-for-length (< -2 SD-acute malnutrition) and covariance analysis were done to detect associations between intestinal parasitism and nutritional status. RESULTS: Of the 136 children, 30.6% were infected; 26.2% had helminth infections (A. lumbricoides, T. trichiura, S. stercoralis), 14.9% had protozoan infections (G. lamblia) and 11.8% had mixed infections. Wasting and stunting were present in 2.9% and 12.5%, respectively. Lack of sanitary toilet facilities and low maternal education were related to mixed infections and presence of helminths (p < 0.05). Weaned children were at greater risk of mixed infections (Odds Ratio (OR) 6.5; 90% CI: 1.9-21.5) and of G. lamblia infections (OR: 2.89; 90% CI: 1.0-8.34). Children infected with T. trichiura and with mixed infections were more likely to show wasting (p < 0.05). CONCLUSION: The high infections in young children indicate that they be included in periodic antiparasitic chemotherapy. Burden of disease associated to intestinal parasitism may be reduced if breastfeeding is continued beyond 6 months of age.

Animals↗
PubMed2006

Regulatory T cells induced by parasites and the modulation of allergic responses.

The inverse relationship between helminth infection and overt allergic reactivity has intrigued medical scientists for three decades. In the past 5 years, detailed epidemiological studies coupled with new experimental model approaches, have substantiated the negative effects of infection on allergic disease manifestation, and begun to provide mechanistic explanations for this fascinating interaction. Several key conclusions can now be drawn. First, the modulation of allergies, such as Th2-dependent pathologies, is not primarily through immune deviation (e.g. switching responsiveness to Th1), as helminth infections themselves drive strong Th2 responses. Second, helminth-infected hosts show similar levels of immune sensitisation to allergens as do uninfected counterparts, but the expression of overt allergic reactivity is suppressed. Third, the down-modulation of allergy in both human and experimental infections is consistent with the activity of T regulatory (Treg) cell populations, which suppress effector mechanisms of both Th1 and Th2 type.

Animals↗
PubMed2007

Intestinal helminth co-infection has a negative impact on both anti-Mycobacterium tuberculosis immunity and clinical response to tuberculosis therapy.

The impact of intestinal helminth infection on Mycobacterium tuberculosis (MTB)-specific immune responses during active tuberculosis (TB) is not known. We investigated the role of intestinal helminth infection in anti-MTB immunity by evaluating both cellular phenotype and cytokine profiles in patients with TB and patients with concomitant TB and intestinal helminth infection (TB + Helm) during TB therapy. Twenty-seven per cent of TB patients enrolled for the study were co-infected with at least one intestinal helminth. At baseline, absolute frequencies of leucocytes, monocytes and eosinophils from TB and TB + Helm patients differed from healthy subjects. Concomitant intestinal helminth infection in TB + Helm patients had a negative impact (P < 0.05) on absolute frequencies of CD3(+), CD4(+), CD8(+), natural killer (NK) T and CD4(+) CD25(high) T cell subsets when compared to either TB patients or healthy controls. Differences in CD4(+) T cell frequencies were accompanied by lower interferon (IFN)-gamma and elevated and sustained interleukin (IL)-10 levels in whole blood (WB) cultures from TB + Helm compared to TB patients. In addition to a depressed anti-MTB immunity, TB + Helm patients also presented with more severe radiological pulmonary disease, with a significant difference (P = 0.013) in the number of involved lung zones at the end of TB treatment. The above data may indicate that concomitant intestinal helminth infection in patients with newly diagnosed TB skews their cytokine profile toward a T helper 2 response, which could favour persistent MTB infection and a more protracted clinical course of the disease.

Adolescent↗
PubMed1981

Stimulation of resistance to Fasciola hepatica infection in sheep by a regime involving the use of the immunomodulatory compound L tetramisole (levamisole).

The effect of prior nematode and cestode infection in sheep on the course of experimental Fasciola hepatica was studied. The cross immunising properties of these parasites per se and the modification of any protective effect conferred by the immunomodulatory compound L tetramisole (levamisole) were investigated. It was recorded that no protection was conferred on sheep against F hepatica infection by virtue of prior infection with any helminth species per se, including Cysticercus tenuicollis. However, a degree of immunity to F hepatica was recorded, for only the second time, in sheep primed with helminth infections before treatment with levamisole. This is the first demonstration of a beneficial effect conferred by levamisole by virtue of its immunomodulatory properties in ruminants infected with any helminth species. Resistance was shown by a 47 per cent reduction in flukes recovered from sheep treated in this way (P less than 0.05).

Animals↗
PubMed2004

Helminths at mucosal barriers--interaction with the immune system.

Helminth parasites are the cause of very significant morbidity, mortality and economic losses in man and domestic animals. Most parasitic helminths infect their hosts via the oral route, and live either at the mucosal surface of the gastro-intestinal tract (GIT), or cross this mucosal barrier on their way to predilection sites. Many helminths live at mucosal surfaces, typically the gut or respiratory tract, and some cross these barriers, either temporarily, spending a period of time in the mucosa before returning to the mucosal surface, or to access other tissues and sites in the host. Typically, helminths induce strongly polarised Th2 responses, which are often effective in mediating protective immunity against those parasites living at mucosal surfaces, but less so in protecting against tissue-dwelling parasites. Induction of strongly-polarised Th2 responses may impair the ability of parasites hosts to eliminate other pathogens. Control of helminth infections relies largely on chemotherapy, together with management and environmental measures designed to keep hosts away from infective stages. Drug resistance has become a significant problem in some helminth populations, and this has promoted interest in the development of immunoprophylactic strategies. However, despite intensive research efforts, helminth vaccines have not become part of regular control strategies. In addition to the considerable technical difficulties posed in the production of vaccines against these complex organisms, further difficulties in securing acceptance for anti-helminth vaccine by regulatory authorities and by users, will be encountered. Such vaccines need not result in sterile immunity, as is required of anti-bacterial and anti-viral vaccines. Recent evidence indicates that while helminths are responsible for disease, immunopathology and impairment of immunity to other pathogens, a complete absence of helminth infection during early life may be a predisposing factor for the development of auto-immune pathology.

Animals↗
PubMed2001

A factor of inducing IgE from a filarial parasite prevents insulin-dependent diabetes mellitus in nonobese diabetic mice.

Parasitic helminth infections are characterized by eosinophilia and markedly elevated levels of circulating antigen-nonspecific immunoglobulin E (IgE), responses from which concern helminth protection. We previously purified a factor from Dirofilaria immitis that induces antigen-nonspecific IgE in mice and rats. Recombinant DiAg (rDiAg) has various biological activities. It is also known that parasitic helminth infection generates tremendous Th2 responses. The nonobese diabetic (NOD) mouse spontaneously develops Th1 cell-dependent autoimmune diabetes. Here we investigated the effects of rDiAg on the initiation and progression of this disease. rDiAg treatment of 6-week-old NOD females (the age at which insulitis typically begins) completely prevented insulitis and diabetes. Thus, rDiAg impaired the islet Ag-specific Th1 cell response in vivo, and the prevention of diabetes by rDiAg was associated with switching of the response from a Th1 to a Th2 profile. Since rDiAg clearly prevented insulitis by inhibiting the development and further accumulation of pathogenic Th1 cells to islets of Langerhans, we conclude that DiAg is a native Th2 inducer in filarial helminth and that Th1 responses are required for early events in the development of spontaneous autoimmune diabetes. In conclusion, the presence of parasitic helminth infections may play an important role as an immunomodulator in some autoimmune diseases or allergies.

Amino Acid Sequence↗
PubMed1992

Controlled tests on activity of contemporary parasiticides on natural infections of helminths in lambs, with emphasis on strains of Haemonchus contortus isolated in 1955.

Ten controlled tests were done between 1972 and 1989, in lambs on pasture, evaluating activity of fenbendazole (FBZ; 5 mg/kg of body weight), oxfendazole (OFZ; 3.5 and 10 mg/kg), oxibendazole (OBZ; 10 mg/kg), pyrantel pamoate (PRT; 25 mg of base/kg), and thiabendazole (TBZ; 44 and 50 mg/kg) against natural infections of helminths, with emphasis on 2 strains (A and B) of Haemonchus contortus. Strain A was phenothiazine-susceptible and strain B was phenothiazine-resistant when isolated in 1955. For approximately 10 years prior to these tests, sheep infected with both strains had been treated periodically each year with several compounds, including thiabendazole, which was used many more times than the other drugs. For this study, 4 (FBZ, OFZ, OBZ, and PRT) of the 5 compounds were evaluated in either 1 or 2 controlled tests. The fifth compound, TBZ, was used for 5 tests. Strain A H contortus was resistant to TBZ for all years tested, but more susceptible to FBZ, OFZ, OBZ, and PRT. Overall, strain B was susceptible to TBZ (with a few exceptions), and also to FBZ, OFZ, OBZ (activity less on immature forms), and PRT. Other abomasal parasites (2 species of Ostertagia and 3 of Trichostrongylus) were found in low numbers, but removal overall was good for the compounds tested. Trichostrongylus axei, found in higher numbers than species of Ostertagia and other species of Trichostrongylus, were effectively removed by all compounds in most cases. Activities of TBZ and PRT were also evaluated against several species of intestinal helminths, most of which were found in low numbers. Cooperia curticei were inconsistently removed by TBZ, but activity of PRT was effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

The influence of schistosomiasis on the serum concentrations of retinol and retinol binding protein of a rural population in Liberia.

121 persons from rural areas of central Liberia were examined for possible interactions between helminthic infections and the retinol (vitamin A) and retinol binding protein (= RBP) status. About 2/3 of this mainly adult population had retinol and RBP serum concentrations less than or equal to 400 micrograms/l and less than or equal to 40 micrograms/ml, respectively. Only one person had a serum retinol concentration less than 100 micrograms/l which is critical for the appearance of xerophthalmia. The retinol and RBP concentrations showed a linear, positive correlation. 19 parasitologically helminth free individuals had mean serum retinol and RBP concentrations of 414 micrograms/l and 43 micrograms/ml, respectively, while the corresponding values of 20 individuals with schistosomiasis as the only helminthic infection were 339 micrograms/l and 35 micrograms/ml. 65 other persons with mixed intestinal and/or tissue helminthiases, and 9 persons with pure Onchocerca volvulus infection exhibited intermediate mean concentrations. 32 persons without serological evidence of helminthic infections had higher serum concentrations of retinol and RBP than 32 individuals in whose sera at least one raised antibody titer was found in the enzyme-linked immunosorbent assay with 3 different helminthic test antigens. In addition to age, sex and pregnancy schistosomiasis might be a further risk factor of latent retinol and RBP deficiency among adults and teenagers living in a schistosomiasis endemic area.

Adolescent↗
PubMed1998

To E or not to E? Can an IL-4-induced B cell choose between IgE and IgG4?

Parasite immunologists had known for some time that IgE-mediated hypersensitivity reactions are rare in patients with chronic helminth infections, even though basophils and mast cells in these patients are sensitized with antiparasite IgE and exposed, often continuously, to parasite antigens. The inhibition of allergic reactivity in chronic helminth infections is mainly due to IgG4 'blocking antibodies' in the serum of the infected individual. IgG4 do not fix complement and bind weakly to Fcgamma receptors. Thus, antigen binding by IgG4, unlike IgE, is likely to have no or minimally harmful consequences. The discovery that, similar to IgE, expression of IgG4 is IL-4-dependent and is an intermediate step in sequential switching from IgM to IgE makes it imperative to understand how the two isotypes are coregulated and whether the two responses can be uncoupled, selectively boosting IgG4 over IgE. The ultimate goal is to apply to allergy the lesson we learnt from helminth infections.

Animals↗
PubMed2002

Cytokine-mediated host responses during schistosome infections; walking the fine line between immunological control and immunopathology.

Most helminth infections of humans and animals induce similar immune responses, which are characterised by the production of Th2-associated cytokines (interleukin (IL)-4, IL-5, IL-9, IL-10, IL-13) and antibodies (IgG1--mouse, IgG4--man, IgE--both). This type-2-biased immune phenotype generally persists for the duration of the infection. Although similar types of immune responses are also triggered during allergy, atopy and anaphylaxis, chronic helminth-induced type-2-associated responses are usually held in check by appropriately regulated control mechanisms that limit the destructive potential of prolonged cytokine bias. Among numerous reported activities, helminth-induced type-2-associated immune responses have been linked to the expulsion of gastrointestinal nematodes and the formation of circumoval granulomas during schistosomiasis. However, what happens when this highly regulated, and often beneficial, type-2 immune response becomes chronic, improperly controlled, or exaggerated during helminth infections? Using schistosomiasis as a model disease, we describe the lethal consequences of inappropriate immune response induction by reviewing the literature generated from experimental animal studies and human epidemiological investigations. Development of severe and non-overlapping immunopathological phenotypes will be discussed in the context of immune deviation and in the setting of chronic and/or hyper-polarised cytokine environments.

Animals↗