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PubMed1999

A controlled evaluation of two school-based anthelminthic chemotherapy regimens on intensity of intestinal helminth infections.

BACKGROUND: School-based deworming programmes have been promoted as a cost-effective strategy for control of nematode infection in developing countries. While numerous efficacy studies have been conducted, there is little information on actual programme effectiveness in areas of intense transmission. METHODS: A randomized trial of a school-based deworming programme was conducted in 12 primary schools on Pemba Island, Zanzibar. Four schools each were randomized to control, twice a year deworming with single dose mebendazole or three times a year deworming. Baseline and 12-month follow-up data on helminth infection using the Kato-Katz technique, demographic information and nutritional status were collected on 3028 children from March 1994 to May 1995. RESULTS: Intensity of infection measured as eggs per gram of faeces (epg) declined significantly for Ascaris lumbricoides, Trichuris trichiura and hookworm infections in both treatment groups. A. lumbricoides infection intensity declined 63.1% and 96.7% in the twice and three times per year treatment groups compared to the controls. T. trichiura infection intensity declined 40.4% and 75.9% respectively and hookworm intensity declined 35.3% and 57.2% respectively compared to control schools. CONCLUSIONS: These results suggest that school-based programmes can be a cost-effective approach for controlling the intensity of intestinal helminth infection even in environments where transmission is high.

Animals↗
PubMed1988

Age-related prevalence, intensity and frequency distribution of gastrointestinal helminth infection in urban slum children from Kuala Lumpur, Malaysia.

The gastrointestinal helminth infection status of 1574 children living in a slum area of Kuala Lumpur, Malaysia was assessed by quantitative coprology. Almost two-thirds were infected with Trichuris trichiura, 49.6% with Ascaris lumbricoides, and 5.3% with hookworm. Infection prevalence rose rapidly to a stable asymptote at 7 years of age, and the age-intensity profile was convex with maximal values in the 5-10 year age classes. This pattern was the same for males and females, but differed markedly between different ethnic groups. The frequency distributions of A. lumbricoides and T. trichiura were highly overdispersed (k values were 0.21 and 0.27, respectively), and age-dependent over the 0-8 year age classes. This suggests that the force of infection with these nematodes is lower in infants than in older children.

Adolescent↗
PubMed1994

Intestinal helminthic infections in the southern Rift Valley of Ethiopia with special reference to schistosomiasis.

Nineteen communities located in the southern part of the Ethiopian Rift Valley were surveyed for S. mansoni infection and other helminth parasites of man. S. mansoni infected individuals were recorded in 11 communities and human prevalence reached more than 10% in 4 of them. The snail intermediate hosts were Biomphalaria pfeifferi in the lower Omo River basin and B. sudanica in the Rift Valley lakes. Other parasites encountered included A. lumbricoides (11.2%), T. trichiura (10.3%), hookworms (25.3%), Taenia sp. (8.1%), Strongyloides sp. (2.9%), H. nana (0.8%), Trichostrongylus sp (0.3%) F. hepatica (0.1%) and E. vermicularis (0.1%). In some communities the prevalence of hookworms, A. lumbricoides and T. trichiura reached 70%, 66.6% and 60%, respectively. A strong association (r = 0.9) was observed between altitude and parasite prevalence and burden. In nine communities located below 1200 metres, infected individuals harboured nearly two or less the number of parasite species while in 10 communities located at altitude above 1200 metres, multiple infection with three or more parasites reached as high as 53.2%. Similarly, the average parasite species per infected person ranged from 0 to 1.4 in the nine communities located at lower altitudes and from 1% to 2.6% in the 10 communities located at higher altitudes. By ages, both prevalence and multiparasitism are significantly in favour of those below 20 years of age (P < 0.005) although hookworms are prevalent in a wider age range. The widespread occurrence of intestinal schistosomiasis in the southern Rift Valley and the epidemiological pattern of other intestinal helminth parasites of man in this section of the Valley are discussed.

Adolescent↗
PubMed2006

Total IgE level in respiratory allergy: study of patients at high risk for helminthic infection.

OBJECTIVE: Eosinophilia and increased serum IgE levels are indicators of atopy; however, other factors can also play a key role, such as intestinal parasitic infections. This study assesses the relationship between total serum IgE, eosinophil count, and anti-Ascaris IgE in individuals with asthma and/or allergic rhinitis. METHODS: A cross-sectional study was carried out in adolescents with asthma and/or allergic rhinitis. The patients had their total serum IgE, anti-Ascaris IgE and eosinophil count measured. RESULTS: A total of 101 patients aged 12 to 21 years were assessed. Median IgE level was 660 IU/mL (P(25-75) 243.5-1500), and the eosinophil count corresponded to 510 cells/mm(3) (P(25-75) 284-811). Anti-Ascaris IgE was positive in 73% (74/101) of the individuals, but parasitological stool examination yielded positive results in only 33.7% (34/101). The correlation coefficients were the following: 0.34 (p = 0.001) between total IgE level and eosinophil count, 0.52 (p < 0.001) between total IgE level and anti-Ascaris IgE, and 0.26 (p = 0.01) between eosinophil count and anti-Ascaris IgE. The final multiple linear regression model pointed out that anti-Ascaris IgE contributed to a total serum IgE level with a coefficient of determination (adjusted R(2)) of 0.25 (F = 12.35; p < 0.001). This effect occurred regardless of eosinophil count and of the presence of intestinal helminthic infection. CONCLUSION: In patients with respiratory allergy and increased total serum IgE levels living in areas where there is a high risk for helminthic infections, the quantification of anti-Ascaris IgE can be more useful and more insightful than the parasitological stool examination.

Adolescent↗
PubMed2005

Very low helminth infection in sheep grazed on pastures fertilised by sewage sludge or cattle slurry.

Helminth infection acquired by lambs grazing on pastures fertilised either by urban sewage sludge or cattle slurry were studied in temperate Central Western France. The aim was to assess the risk of larval cestodoses in lambs after sewage application and of digestive tract nematode infection following the slurry application. Twenty-six sheep were allocated on two paddocks of 0.7 ha, one fertilised with sludge and the other with cattle slurry. The delay between application and actual grazing was 6 weeks; grazing on these paddocks extended from mid July to beginning of November 2002. The herbage biomass was slightly increased in the sludge paddock but it did not result in an increase of lamb live weight, compared with the slurry paddock. The lambs did not acquire cysticercosis or any other larval cestodoses in the sewage sludge group and only very limited infections with Cooperia spp. and Nematodirus spp. were observed in the slurry group. It was concluded that in our conditions the helminth risk was extremely low and was not a cause of restriction of the use of these biowastes.

Animals↗
PubMed1999

Immunology of helminth infections, with special reference to immunopathology.

Immune responses resulting in immunity to infection or disease, share the same basic humoral and cellular mechanisms. While immunity to helminth infection has evolved to mediate rapid elimination of the parasite, the strategies evolved by the parasites themselves aim to delay this rejection process and ensure the survival and distribution of their progeny. Ineffective or incomplete immunity results in persistence of parasites or their products within the host tissues, inappropriate or chronic stimulation by parasite antigens, hyper-reactivity and tissue damage or immunopathology. A long standing classification by Gell and Coombs identifies four major types of hypersensitivity responses accounting for most of the immunopathogenesis, three of which are mediated by antibody and one, delayed type hypersensitivity (DTH), by T cells. This paper aims to give a short review of these four classical hypersensitivity reactions with particular reference to infections of large animals with helminth parasites. In addition, in view of the functionally different helper T cell subsets now identified, the existing DTH response is redefined as DTH Type 1 (Th-1 mediated) and two new classes of T cell-dependent DTH responses are proposed; DTH Type II, associated with the Th-2 type cytokines IL-4 and IL-5 and eosinophilic granuloma formation, and DTH Type III, associated with IL-4 and TGF-beta and fibrosis. Finally, some implications of immunopathology on parasite control strategies are discussed.

Animals↗
PubMed1994

Effects of trypanosome and helminth infections on health and production parameters of village N'Dama cattle in The Gambia.

The effects of trypanosome and helminth infections on health and production parameters in 2000 village N'Dama cattle were assessed periodically. Blood examination showed Trypanosoma congolense and Trypanosoma vivax to be prevalent, while strongylid-type eggs were those most frequently encountered in faecal samples. A distinct seasonal fluctuation was detected for both blood levels of trypanosomes and helminth egg output. Strongylid burden and trypanosome infection had significant negative effects on packed red cell volume levels and body weights mainly in animals of 2-3 years old. Clear indications of an increased susceptibility to trypanosomosis were found in animals affected by helminths. Similarly, animals infected with trypanosomes were more frequently infested with strongyles and egg counts were higher than in cattle in which no trypanosomes were detected.

Age Factors↗
PubMed1992

A theoretical framework for the immunoepidemiology of helminth infection.

Field studies of parasitic helminths in endemically infected human communities have provided quantitative information on the relationships between parasite burdens, immune responses and age. There are considerable difficulties in the interpretation of these immunoepidemiological data due to the complexities of the biological processes generating the observed patterns. In this paper simple mathematical models are used to explore the expected patterns of variation with host age in parasite burdens, the aggregation of parasites among hosts, levels of immune response, and the correlation between parasite burdens and immune responses. These relationships reflect rates of infection, rates of parasite mortality, the strength of the immune response, and the duration of immunological memory. The models generate some complex and counterintuitive patterns. The analysis suggests that some of these patterns might serve to (i) distinguish effects due to acquired immunity from effects due to age-dependent exposure, (ii) identify potentially protective immune responses, and (iii) identify the parasite stages important in the development of acquired immunity. The results imply that previous analyses of immunoepidemiological data may have been overly simplistic and, especially, that patterns believed to be inconsistent with protective immunity may have been incorrectly interpreted.

Adolescent↗
PubMed2005

Prevalence and predictors of intestinal helminth infections among human immunodeficiency virus type 1-infected adults in an urban African setting.

Sub-Saharan Africa is disproportionately burdened by intestinal helminth and human immunodeficiency virus (HIV)-1 infection. Recent evidence suggests detrimental immunologic effects from concomitant infection with the two pathogens. Few studies, however, have assessed the prevalence of and predictors for intestinal helminth infection among HIV-1-infected adults in urban African settings where HIV infection rates are highest. We collected and analyzed sociodemographic and parasitologic data from 297 HIV-1-infected adults (mean age = 31.1 years, 69% female) living in Lusaka, Zambia to assess the prevalence and associated predictors of helminth infection. We found at least one type of intestinal helminth in 24.9% of HIV-infected adults. Thirty-nine (52.7%) were infected with Ascaris lumbricoides, and 29 (39.2%) were infected with hookworm. More than 80% were light-intensity infections. A recent visit to a rural area, food shortage, and prior history of helminth infection were significant predictors of current helminth status. The high helminth prevalence and potential for adverse interactions between helminths and HIV suggests that helminth diagnosis and treatment should be part of routine HIV care.

AIDS-Related Opportunistic Infections↗
PubMed2002

Spatial and intensity-dependent variations in associations between multiple species helminth infections.

Estimated associations between infections with different helminth species can be used to predict the proportion of a population infected with multiple species infections. This is an important measure of disease burden, as those with multiple infections are often at an increased risk of morbidity. In this paper, we investigate variation amongst the estimated associations between Ascaris lumbricoides, Trichuris trichiura and hookworm, over a number of different spatial levels among schoolchildren in Cameroon. Associations between species were largely homogeneous within districts, provinces and ecological zones, although variation between these regions was identified, implying that a single measure of association may not be appropriate in different epidemiological settings. Further data collected amongst school children in Kenya and Uganda were analysed, to assess the dependence of the associations on the intensity of infection. It was found that the strength of the association between A. lumbricoides and T. trichiura increased with intensity, such that those with more intense infections with one species are increasingly likely to harbour concurrent intense infections with the other species. The implications of these results are discussed in relation to the estimation of the disease burden due to multiple helminth species.

Adolescent↗
PubMed1992

Effect of genetic type, lactation and management on helminth infection of ewes in an intensive grazing system on irrigated pasture.

A survey of helminth infection was conducted in a flock of 290 ewes distributed into Romanov (R), Merinos d'Arles (M) and Romanov x Merinos (R x M) genetic types, grazing irrigated pasture in the south of France. Faecal egg and larval counts were done seven times per year from 1981 to 1984 on homogeneous groups of ewes and then individually once to four times every autumn from 1985 to 1988. Helminth fauna was diverse and more abundant during autumn. High levels of strongyle infection occurred in the ewes that remained on the same irrigated pastures during summer. Moving to Alpian pastures during the summer lowered autumnal infection. Significant differences between genotypes in intensity of infection were observed in the order R > R x M > M for strongyles (Teladorsagia circumcincta and/or Trichostrongylus vitrinus, Chabertia ovina and/or Oesophagostomum venulosum, Nematodirus spp.), Moniezia spp. and Dictyocaulus filaria. The hierarchy was reversed for Fasciola hepatica infection and not consistent from one year to another for protostrongylid infections. The effect of lactation intensity on the postparturient rise was studied by equilibrating number of ewes according to reproductive status (zero, one or two lambs in lactation). Merino ewes with two lambs in lactation, as well as primiparous Romanov ewes, had significantly higher strongyle infections than the others. The repeatabilities of the larval and egg counts between the four trial years were 0.24, 0.23 and 0.16, respectively, for protostrongyles, Nematodirus and strongyles, with higher intra-annual values for protostrongyles and inconsistently significant results for strongyles due to the presence of several species.

Animals↗
PubMed1994

Status of soil-transmitted helminthic infection in Nepal.

A retrospective evaluation of the status of soil-transmitted helminthic infection in Nepal during the period from 1985 to 1992 was conducted at the Parasitology Laboratory, Department of Pathology, TU Teaching Hospital in Kathmandu. An average of 6,537 faecal samples were examined each year for the presence of various types of intestinal parasites. The annual rate of positivity of these samples for soil-transmitted helminthiasis ranged from 18.0 to 36.6%. The annual incidence decreased every successive calendar year in both adults and children, irrespective of sex. Among the various types of helminths, the most common was Ascaris lumbricoides (roundworm), followed by hookworm. The incidence of A. lumbricoides remained constant throughout the study period, while that of other parasites markedly decreased each year.

Adult↗
PubMed1969

[Study On The Status Of Helminthic Infections In Koreans]

This study was undertaken to evaluate the present status of intestinal helminthic infections in Koreans, from April 1967 through May 1969. The nationwidely collected stool specimens and scotch-tape anal swabs from primary schoolchildren, middle school students, draftees to army recruitment camp, soldiers and inhabitants of various parts of Korea were examined. The methods employed were Kato's cellophane thick smear technique and formalin-ether sedimentation technique in 40,581 for the prevalence rate of various intestinal helminths, scotch-tape anal swab technique in 8,585 for the prevalence rate of Enterobius vermicularis and by Stoll's dilution egg counting technique in 1,174 for the evaluation of the worm burden of some helminths. The results are as follows. I. Result of stool examination: 1. The positive rate of intesinal helminthes of any kind was 90.5% among 40,581. In rural people, it was 92.3% in average in contrast to 85.0% in Seoul inhabitants. 2. The infection rate of A. lumbricoides in 40,581 was 58.2%. It was higher in rural people 62.9% than in Seoul inhabitants and highest in 5-9 year-old group by age. 3. The infection of Trichocephalus trichiurus showed the highest prevalence rate in Koreans and it was 74.5%. No remarkable difference was observed between Seoul inhabitants(72.2%) and rural people(75.2%). The tendency of higher prevalence rate with the older age group was observed. 4. The infection rates of hookworm and Trichostrongylus orientalis in 40,581 examinations by cellophane thick smear were 5.1% and 5.8% respectively. But in 4,949 examinations for which refined cellophane thick smear technique and formalin-ether sedimentation technique were employed, the infection rates were turned out 17.6% in hookworm and 15.9% in T. orientalis. Although rural people showed higher infection rate of hookworm(18.8%) than Seoul inhabitants(13.8%), the reverse was true in T. orientalis infection rate(14.5% : 20.3%). Both kinds of infections were tend to be higher with the increase of age. 5. The infection rates of Clonorchis sinensis and Metagonimus yokogawai were 4.7% and 0.4% respectively. In both kinds of infections male showed higher infection rates than female and the tendencies of higher infection rate in the older age group were observed. The provinces which showed the higher infection rate of C. sinensis were South and North Kyongsang Do and North Cholla Do, all of which are provinces of southern part of Korea. Some endemic foci of M. yokogawai were noticed in South Kyongsang Do and South Cholla Do. 6. The infection rate of Taenia spp. by applying only the stool examination was 0.7% throughout the survey. No sex difference in infection rate of Taenia spp. was noticed, but in older age group it was increased. Cheju Do, the island of extreme southern part of Korea seemed the most endemic area and South and North Cholla Do were next in ranking of Taenia infection rate. The ova of Hymenolepis nana were observed in 0.2% and all of them were under the age of 20 except only one caes. The infection rate seemed higher in female (0.3%: 0.1%). No geographical difference was noticed except 1.1% of schoolchilderen and students of Cheju Do. II. Result of Scotch-tape anal swab technique for E. vermicularis infection. The infection rate of E. vermicularis in 8,585 urban and rural schoolchildren and rural inhabitants was 46.6%. Female (57.9%) had definitely higher infection rate than male (41.4%). The infection rate was significantly higher in rural people than Seoul schoolchildren. The exteme example was 79.7% in schoolchildren of South Cholla Do. III. Result of worm burden examination by Stoll's dilution egg-counting technique: 1. Among 1,174 examinations, countable(E.P.G.> 100) cases of A. lumbricoides were 745(63.5%) and the mean E.P.G. was 9,723. The mean E.P.G. in Seoul inhabitants was 5,835 in contrast to 10,820 in rural people. The age group of 5-9 showed the heaviest mean E.P.G., 11,337. 70.6% of 745 cases were less than 10,000 in E.P.G. which means light infection. 2. Countable cases by Stoll's technique for T. tr trichiurus ova were 63.5% and mean E.P.G. was 649. No difference between Seoul and rural inhabitants was observed. Grade I and II in which E.P.G. is less than 5,000 involve 99.3% of positive cases. 3. 91 cases (7.9%) in 1,174 were positive for hookworm ova by Stoll's technique and mean E.P.G. was 501. All cases were in Grade I and II which were less than 5,000 in E.P.G. Trichostrongylus orientalis was positive only in 25 cases (2.1%) by Stoll's technique and mean E.P.G. was 340. No cases were found to have more than 5,000 in T. orientalis E.P.G. 4. The mean E.P.G. of Clonorchis sinensis among the referred cases of clonorchiasis to Department of Parasitology, Seoul National University, was 9,416. On the other hand mean E.P.G. of C. sinensis was 21,376 among cases in the hyperendemic area of Kimhae, South Kyongsang Do, and 3,073 in cases from other various localities. Among referred clonorchiasis cases to our Department, 21.6% were turned out to have the E.P.G. more than 10,000. The cases who have the E.P.G. more than 10,000 in hyperendemic area, Kimhae were 40.7% and in other various localities were 9.1%

Journal Article↗
PubMedDate not supplied

Herd immunity to helminth infection and implications for parasite control.

Despite much research on immunological responses to helminth parasites, knowledge of the dynamic interplay between levels of herd immunity in humans and the rates of exposure, establishment and mortality of parasites remains limited. We describe here a simple mathematical model for the population dynamics of helminth infections which mirrors the development of a degree of acquired immunity within populations which are genetically heterogeneous with respect to immunological responsiveness. We interpret observed patterns in the age-specific intensity of infection and attempt to understand the possible effects of control measures based on chemotherapy and vaccination. Mass chemotherapy can, in some circumstances, reduce the level of herd immunity such that average worm burdens in the adult age classes rise above their precontrol levels. When certain individuals or groups are predisposed to heavy infection, selective or targeted drug treatment can have significantly greater impact than mass or random application. Conversely, model predictions suggest that effective parasite control by vaccination (if and when vaccines become available) is difficult to achieve in communities that are genetically heterogeneous in their ability to mount protective responses to infection.

Age Factors↗
PubMed1977

Anthelmintic Efficacy Of Methyl-5-Benzoylbenzimidazole-2-Carbamate(Mebendazole) Against Multiple Helminthic Infections.

A clinical trial of Korean Patent mebendazole was undertaken upon some intestinal helminthic infections in 288 rural Koreans residing in Pochun and Jinyang Gun, from November to December, 1976. They were examined by the cellophane thick smear technique, Stoll's egg counting technique and/or Scotch-tape anal swab before and 3 weeks after the treatment. The administered dose of mebendazole was 600 mg, divided by 100 mg, twice daily for 3 consecutive days disregarding the body weight and the age of the cases. It was confirmed that mebendazole is very effective, broad-spectrum anthelmintic, especially against Ascaris, Ancylostoma, Trichostrongylus and Enterobius infections. Their negative conversion rate and egg reduction rate were respectively; 94.0 and 99.6 per cent in Ascaris, 71.4 and 97.3 per cent in Ancylostoma and 95.0 and 100 per cent in Trichostrongylus. The negative conversion rate in Enterobius was 92.3 per cent. The anthelmintic efficacy against T. trichiura infection was not satisfactory in spite of low worm burden (negative conversion rate, 27.3%, egg reduction rate, 65.5%).

Journal Article↗
PubMed1985

[Survey of helminthic infections and treatment of Taenia species infection among the aborigines in Chien-Shih District, Hsin-Chu County, northern Taiwan].

Six hundred and sixteen out of 770 (80%) aborigines examined were found to be infected with intestinal helminthes. A total of 7 species of parasites were detected with the formalin-ether concentration technique. The infection rate of Ascaris lumbricoides was 77.1%, Trichuris trichiura 28.8%, Taenia sp. 18.4%, Enterobius vermicularis 1.6%, and there was one case each of hookworm, Hymenolepis nana and H. diminuta infections. Infection rate was slightly higher among females (81.3%) than males (78.9%). It was also higher in Yu-Feng (86.9%) than Shiu-Luan villages (75.5%). The incidence of helminthic parasites was found in all ages. 11-20 age-group was the highest (84.4%), followed by 1-10 (81.5%), 51 and more (80.6%), 41-50 (77%), 31-40 (76%), and 21-30 (72%). In general, the rate seems to be higher among the young and old. But, the rate of Taenia sp. was increased with the increase in age. Taenia sp. was found to be of considerable high prevalence. However, only 7 out of the 252 (2.7%) junior high school students were found infected in contrast to the 18.4% found in the villages. After atabrine treatment, 108 adult worms, 83 with and 25 without scolices were obtained from 54 of 72 treated cases. The number of expelled worms varied from 1 to 8, with an average of 2 worms per infected person. 29 (53.7%) aborigines expelled only one worm, and 25 (46.3%) cases expelled more than one worms.

Adolescent↗