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PubMed1987

The evasion of the immune response and immunological unresponsiveness: parasitic helminth infections.

A selective review is given of the mechanisms associated with the evasion of the immune response by parasitic helminths and immunological unresponsiveness as it applies to helminth infections. Immunosuppression caused by parasites leading to reduced responsiveness of lymphocytes to mitogens is discussed, and mechanisms that inhibit effector mechanisms at the parasite surface and polyclonal activation of lymphocyte populations are dealt with. Physiological immunosuppression associated with parturition and lactation and the immunological unresponsiveness of young ruminants are dealt with in detail.

Animals↗
PubMed1975

Survey of helminth infections in Maine dairy cattle.

The survey was done to determine the incidence and seasonal prevalence of the gastrointestinal helminths infecting Maine dairy cattle. Approximately equal groups of calves, heifers, and cows from 13 dairy farms, managerially and geographically representative of dairying in the state, were sampled at regular 2-month intervals over the period of a year. On the basis of fecal egg counts and identification of cultured larvae, the following results were obtained: Of the 94 adult cows, 78 heifers, and 91 calves sampled continuously in the course of the survey, 95.7%, 98.7%, and 96.7%, respectively, were strongylorid positive (infected with Ostertagia, Cooperia, Trichostrongylus, Haemonchus, and Oesophagostomun), with an overall incidence of 97%. Strongyloides papillosus eggs were in 64.6% of the cattle, Bunostomum in 40.3%, Nematodirus in 27.8%, Trichuris in 27.0%, Capillaria in 9.5%, Moniezia in 25.1%, and Dictyocaulus viviparus larvae in 2.7%. Worm burdens, as reflected by mean nematode egg production per gram of feces, varied. The greatest worm burdens were in the calves, followed by the heifers and the cows. A marked variation in egg production related to season was observed, particularly with the strongylorid worms. Peak strongylorid egg production was observed in the May-June sampling period. After the peak period, worm burdens decreased in all groups of cattle to their lowest point during the winter period of January-February. This pattern of egg production was similar to that reported by workers in other parts of the world. Farm management practices were shown to be related to the degree of parasitism existing in these herds. Those herds classed as poorly managed had significantly higher levels of parasitism in young animals than those classed as having fair or good management.

Animals↗
PubMed1994

Intestinal helminth infections in rural school children in Njala, Sierra Leone.

In a survey of five primary schools and one secondary school in and around the Njala University College environment, in Southern Sierra Leone, 1820 school children were examined. Ascaris lumbricoides was the most common helminth encountered (33.3%) followed by Trichuris trichiura (14.6%) and hookworm infection (10.4%). There was striking differences in the rate of infection between the various schools with the International School being the least affected by all parasites. Multiple infections were quite common, with 53.1% having one type of helminth infection, 40% had two types of helminth infections, while 6.9% had three or more helminth infections. School screening should be an important component of Primary Health Care in Sierra Leone since it offers good opportunity for disease surveillance, health education and early detection and treatment of infections before they become chronic.

Adolescent↗
PubMed1999

A survey of helminthic infections in the residents of rural areas near Ulaanbaatar, Mongolia.

A total of 738 samples was collected to survey the helminthic infections of residents in two rural areas near Ulaanbaatar, Mongolia for 2 weeks from July 23 to August 2, 1998. Among 391 scotch-taped slides of anal swabs of children and of young teenagers. Enterobius vermicularis eggs were detected in 138 cases (35.3%). With the fecal samples of 206 Kato-Katz thick smear slides from adults, the eggs of E. vermicularis were observed in 9 cases and Taenia sp. in one case, respectively. And by ELISA on 141 blood samples absorbed to blood sampling paper, 12 cases (8.5%) were found to be positive against the hydatid cyst antigen. Enterobiasis and hydatidosis are two major endemic diseases which are related closely to the life style of Mongolian.

Adolescent↗
PubMed2002

Nitazoxanide compared with quinfamide and mebendazole in the treatment of helminthic infections and intestinal protozoa in children.

The present study was carried out to evaluate the effectiveness of nitazoxanide compared with that of quinfamide, mebendazole, or both in the treatment of intestinal protozoa and helminthic infections. A total of 677 stool specimens from children aged 2-12 years living in 3 communities of Colima, México, were analyzed in order to detect the presence of cysts, trophozoites, eggs, or larvae of intestinal protozoa or helminths. A total of 275 infected children were enlisted in a double-blind controlled study and randomly assigned to one of 2 treatment groups: Group A, nitazoxanide (200 mg for 3 days) and Group B, quinfamide (100 mg for 1 day), mebendazole (200 mg for 3 days), or both. A posttreatment fecal examination was conducted on Day 14 from treatment initiation. In Group A (n = 143), the parasitosis eradication rate was superior to that of Group B (n = 132). However, there was no significant difference between the 2 groups (P > 0.05).

Antiparasitic Agents↗
PubMed1998

Different patterns of intestinal helminth infection among young workers in urban and rural areas of Alexandria Governorate, Egypt.

The process of urbanisation taking place in most developing countries is creating favourable conditions for an increase in prevalence of infections, especially with intestinal parasites, in the marginal areas of the towns. The present study was implemented in 1996 to assess the varying prevalence and intensity of infection among young workers in urban and rural areas of the same Governorate (Alexandria, Egypt). The sample comprised 408 male subjects, 8 to 19 years of age, in various occupations: 308 from urban areas, 67 from an industrialised village close to the desert, and 33 from a rural village. A quantitative diagnosis of intestinal helminth infections was made using the Kato-Katz technique, with a double reading of each slide. The results showed a higher prevalence (> 50%) and intensity of infection (indirectly measured as number of eggs per gram of faeces) than in previous studies. Furthermore, a higher prevalence and intensity of infection with Ascaris lumbricoides and Trichuris trichiura was detected in urban districts, as compared to rural areas. This difference was statistically significant. High crowding index, latrine shared with other families and no piped water inside the household, were more common in urban areas as compared with rural settlements and also associated with a higher intensity of infection by soil-transmitted helminths. The trend toward urbanisation seems to have caused deterioration of living conditions and sanitation standards in some areas of Alexandria city, with the most vulnerable people experiencing an increase in intestinal parasitic infections.

Adolescent↗
PubMed2001

Status of soil transmitted helminthic infections in India--observations on sample surveys using Kato-Katz technique.

Results of surveys conducted in eight different ecologically homogenous zones in the country, using WHO sampling design methodologies and Kato-Katz technique are presented in this communication. Hilly and coastal areas had high STH prevalence ranging from 34%-36% with total epg ranging from 53,952-4,67,976. Apart from this, Chitradurga urban area had STH prevalence of 39.6% with epg of 81,792. However, except in few cases, in all these surveyed areas, intensity of STH infection was found to be light. A national programme for control of soil transmitted helminthic infections is advocated.

Animals↗
PubMed1985

Community control of helminth infections of man by mass and selective chemotherapy.

The design of mass and targetted community-based chemotherapy programmes for the control of the major helminth infections of man is discussed in relation to the population and transmission dynamics of the parasites. Rapid reinfection following a single mass or targetted anthelmintic application is shown to be a universal feature of helminth transmission, as a consequence of the regulatory or feed-back mechanisms controlling population abundance within both individuals and the community as a whole. Control of reinfection requires repeated community treatment where the intensity of application and the interval between treatments are dependent on the reproductive life-expectancy of the adult worm, the net force of transmission prior to control (the basic reproductive rate) and the factors which create aggregation in the distribution of parasite loads within the population. Selective or targetted treatment is shown to be most effective for the control of morbidity as opposed to the control of transmission. The impact of targetted treatment depends critically on the factors that generate heterogeneity in parasite burdens and on whether or not selectivity is based on a single or repeated identification of the 'wormy' fraction of the community. Monte Carlo simulation studies are employed to assess the likely impacts of different control strategies on average parasite abundance/person and the distributions of parasite loads within populations. Future epidemiological research needs are discussed in relation to theoretical work and recent field studies of predisposition to heavy infection.

Age Factors↗
PubMed1996

The microsimulation approach to epidemiologic modeling of helminthic infections, with special reference to schistosomiasis.

The microsimulation technique has been used since 1985 as a tool for epidemiologic modeling of helminthic infections. This technique is characterized by mimicking individual life histories, which makes it possible to include several relevant processes and mechanisms that have not so far been considered in applied modeling. Biological, epidemiologic, and social processes can be simulated in detail, which allows realistic prediction of the impact of control strategies. It is clear that careful quantification and validation of the many processes and parameters in the model requires close collaboration with experts working on control projects. In the development and application of a microsimulation model, we distinguish eight steps, ranging from the identification of questions the model will be designed to address, to the completion of a model that can be used as a routine decision-making tool in a control program.

Animals↗
PubMed2006

Poor sanitation and helminth infection protect against skin sensitization in Vietnamese children: A cross-sectional study.

BACKGROUND: Geohelminth infection and poor hygiene may be protective against allergic sensitization. OBJECTIVE: To determine whether current helminth infection is associated with a reduced prevalence of allergen skin test sensitization in a Southeast Asian population of children with a high prevalence of hookworm infection. METHODS: A total of 1742 Vietnamese schoolchildren were invited to take part in a cross-sectional survey. Allergen skin sensitization to house dust mites (Dermatophagoides pteronyssinus and Dermatophagoides farinae) and American cockroach (Periplaneta americana) were measured and stool samples for qualitative and quantitative geohelminth estimation collected. RESULTS: A total of 1601 children age 6 to 18 participated. Sensitization to dust mites was present in 14.4% and to cockroach in 27.6% of children. In a mutually adjusted model, the risk of sensitization to dust mites was reduced in those with higher hookworm burden (adjusted odds ratio [OR] for 350+ vs no eggs per gram, 0.61; 95% CI, 0.39-0.96) and with Ascaris infection (adjusted OR, 0.28; 0.10-0.78), and increased in those using flush toilets (adjusted OR for flush toilet vs none/bush/pit, 2.51; 1.00-6.28). In contrast, sensitization to cockroach was not independently related to geohelminth infection but was increased in those regularly drinking piped or well water rather than from a stream (adjusted OR, 1.33; 1.02-1.75). CONCLUSION: Geohelminth infection, sanitation, and water supply influence the risk of allergic sensitization in Vietnamese children. This is consistent with a protective effect against allergy by geohelminth or other gastrointestinal infection. CLINICAL IMPLICATIONS: If the inverse relationship between geohelminth infection, poor sanitation, and allergic sensitization proves to be causal, drugs derived from parasite products may help to alleviate clinical allergic disease.

Adolescent↗
PubMed1999

Susceptibility to Trypanosoma cruzi is modified by a previous non-related infection.

Helminth infections are frequently massive, chronic and strong inductors of Th2-type cytokines. This implies that infection by such parasites could alter the susceptibility to subsequent infections by other pathogens, particularly intracellular parasites. We therefore explored whether a persistent infection, caused by Taenia crassiceps cysticerci, in BALB/c mice could affect susceptibility to a later infection by Trypanosoma cruzi. We found that the presence of the cysticerci indeed modified the immune response and the susceptibility to T. cruzi, and that these modifications depended on the time-course evolution of the initial infection. Coinfection with the protozoan in the early stages of the helminth infection, induced a delay on the onset of parasitaemia, early specific production of IFN-gamma and high specific production of IL-4. A significant increase in susceptibility to T. cruzi was observed only when mice were coinfected in late stages when the helminth load is greater and a Th2 type response against it is predominant. The in vitro specific response to T. cruzi antigens was then characterized by low levels of both IFN-gamma and IL-4. These findings suggest that chronic helminth infections could potentially have a significant influence over the immune response and hence susceptibility to other pathogens.

Animals↗
PubMed1982

Cellular basis of the non-specific potentiation of the immunoglobulin E response after helminth parasite infection.

Helminth parasites induce a substantial increase in the production of immunoglobulin E (IgE) by the host after infection. Only a portion of the IgE antibody produced is specific for parasite-derived antigens since production of IgE antibody to non-parasite-derived antigens is also stimulated after infection. Investigators have recently observed, in the parasite-infected host, the appearance of both T and B lymphocytes that synthesize lymphokines that affect the production of IgE in vitro. The results of some of these studies will be reviewed presently, and the possible role of lymphokines in the increase of IgE production after helminth infection will be discussed.

Animals↗
PubMedDate not supplied

Intestinal helminth infections among school children in Visakhapatnam.

A study was carried out between 1993-1994 to determine the prevalence and intensity of intestinal helminth infections among 217 primary school children in Relliveedhi, a slum area in Visakhapatnam. The children were between 7 to 13 years of age and belonged to lower socio-economic status. Stool samples collected were processed by modified formalin-ethyl acetate sedimentation technique to determine ova counts (EPG). One hundred and seventy seven children were infected with one or more of the intestinal parasites viz. Ascaris lumbricoides, Trichuris trichiura and hookworm. The overall prevalence of infection was eighty two per cent. Ascaris lumbricoides was the most common infection with a prevalence of 75% followed by T. trichiura (66%) and hookworm (9%). All infected children received a single dose of albendazole (400 mg/child). Single stool samples were examined over a period of nine months to study reinfection dynamics.

Adolescent↗
PubMed2001

Impact of intestinal helminth infection on anemia and iron status during pregnancy: a community based study in Indonesia.

A cohort study was carried out in Purworejo District, Central Java, Indonesia to investigate prevalence of anemia and low iron stores during pregnancy in relation to intestinal helminth infection. 442 pregnant women were followed until 5-10 weeks postpartum, during the period of April 1996 - August 1998. Information on intestinal helminths, hemoglobin and serum ferritin was collected each trimester. Highest prevalence of anemia in pregnancy (37.1%) was found in the second trimester, while the highest prevalence of low iron stores (49.5%) was found in the third trimester. Most pregnant women (69.7%) were infected with at least one species of pathogenic intestinal helminths. The most common helminth detected was Trichuris trichiura followed by Necator americanus (hookworm) and Ascaris lumbricoides. A significant negative association was found between hookworm infection and serum ferritin at the first trimester (p = 0.010). It is concluded that hookworm infection can interfere iron stores. Other causes of anemia among pregnant women should be considered. Anthelminthic therapy could be given to infected women before conception as public health strategy to improve iron status.

Adult↗
PubMed2003

[Risk factors for iron-deficiency anemia in children and adolescents with intestinal helminthic infections].

OBJECTIVE: To investigate risk factors for iron-deficiency anemia in children and adolescents (7 to 17 years of age) with intestinal helminthic infections. METHODS: A cross-sectional study was carried out with 1 709 children and adolescents living in Jequié, a town in the state of Bahia, Brazil, who had mild to moderate infection by Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura, or hookworms. We obtained data concerning hemoglobin levels (using a portable hemoglobinometer), dietary habits (24-hour dietary recall), parasitic infections (Kato-Katz method), sanitary conditions (water supply, sewage connection, garbage collection), housing conditions (type of construction, number of persons per room), income, and amount of schooling of the parents or guardians. The risk factors for anemia were studied based on a hierarchical model of causality. RESULTS: The prevalence of parasitic infection was 74.8% for T. trichiura, 63.0% for A. lumbricoides, 55.5% for S. mansoni, and 15.7% for hookworms. Among the children and adolescents studied 32.2% were anemic. After adjustment for confounding variables, the results of the multivariate analysis showed that the following variables were significantly associated with anemia: per capita family income below US$ 27 (equal to one fourth of the Brazilian minimum wage), male sex, age of 7 to 9 years, and inadequate intake of bioavailable iron. CONCLUSIONS: The initiatives to control anemia in the group at greatest risk, as identified in this study, should seek to increase the consumption of iron-rich foods, boost the bioavailability of the iron ingested, and improve socioenvironmental conditions.

Adolescent↗
PubMed2000

[Influence of helminthic infections and nutritional status on immune response in Venezuelan children].

We investigated the influence of nutritional status, as determined from anthropometric measurement, and of helminthic infections on the immune response of children of low socioeconomic status in two rural communities in Venezuela: El Cardón in the state of Nueva Esparta and San Daniel in the state of Miranda. A total of 125 boys and girls between 2 and 15 years old participated in the study. Their socioeconomic stratum was determined by a modified Graffar method. A physical examination was performed, as was also an anthropometric evaluation that took into account three indicators--weight-for-height, weight-for-age, and height-for-age--according to parameters established by the World Health Organization. Other examinations included feces, secretory IgA in saliva, total serum IgE, and anti-Ascaris-specific immunoglobulins. The children in both of the communities were in strata IV and V of the of Graffar scale, with a significantly greater number of stratum V inhabitants in San Daniel (P < 0.001). The results suggest that exposure level and individual susceptibility to the parasites are determining factors in parasitic infection and immune system behavior. The intensity of the parasitic burden plays an important role in stimulating polyclonal IgE, which diminishes the effectiveness of the specific response to those infections. On the other hand, nutritional deficiencies could change the immune mechanisms of the mucous membranes, negatively influence the synthesis of secretory IgA, and stimulate the production of polyclonal IgE. Poor sanitary and socioeconomic conditions promote more exposure to gastrointestinal parasites and a deficient nutritional status, which modulates the immune response and affects serum IgE and secretory IgA production mechanisms.

Adolescent↗
PubMed1998

A small-scale survey of intestinal helminthic infections among the residents near Pakse, Laos.

A small-scale epidemiological survey was undertaken on the residents along the Mekong River near Pakse, Laos, to know the status of helminthic infections. A total of 137 fecal samples were collected from the staffs of the provincial government, their family, and primary schoolchildren in Pakse City, Champassak Province, and examined by Kato-Katz smear technique. The overall helminth positive rate was 75.9%, and the helminths detected were Opisthorchis viverrini (43.8%). Ascaris lumbricoides (26.3%), Trichuris trichiura (19.0%), hookworms (19.0%), Strongyloides stercoralis (2.2%), Taenia sp. (0.7%), and Schistosoma mekongi (1.5%). To obtain the adult worm of the liver fluke, three infected persons were treated with praziquantel and purged with magnesium sulfate. Five, 10, and 395 adult flukes, respectively, were collected from their diarrheic stools, all of which were morphologically identified as O. viverrini. The results represent that the liver fluke and soil-transmitted helminths are highly prevalent, and the life cycle of S. mekongi is likely to be maintained in this area.

Adult↗