Intestinal parasitic infections in man: a review

Intestinal parasites of importance to man are Enterobius vermicularis, the soil-transmitted helminthes (STH)--Ascaris lumbricoides Tricburis trichiura, bookworms (Necator americans/Ancylostoma duodenale) and Strongyloides stercoralis and the protozoa Entamoeba histolytica and Giardia duodenalis. Other protozoa such as Cryptosporidium sp. and Isopora sp. are becoming important in causing prolonged diarrhea in immunocompromised patients. It is estimated that almost 1 billion, 500 million and 900 million people worldwide are infected by the major nematode species--A. lumbricoides, T. trichiura and hookworms respectively. Most of the infections are endemic and widely distributed throughout poor and socio-economically deprived communities in the tropics and subtropics. Environmental, socio-economic, demographic and health-related behavior is known to influence the transmission and distribution of these infections. In giardiasis, one study indicates that age < or = 12 years and the presence of family members infected with Giardia were risk factors for infection. Most of the infections occur in children and both genders are equally affected. Epidemiological studies of STH infections have shown that the prevalence and intensity of infection are highest among children 4-15 years of age. The frequency of distribution of STH infections is over-dispersed and highly aggregated. areas reinfection can occur as early as 2 months post-treatment, and by 4 months, almost half of the population treated become reinfected. By 6 months the intensity of infection was similar to pretreatment level.     

The prevalence,intensity and ecological determinants of helminth infection among children in an urban and rural community in Southern Malawi

Rapid urbanisation and poor town planning in Malawi has been associated with poor environmental hygiene and sanitation. The aim of the present study was to investigate the prevalence, intensity and some potential risk factors of intestinal helminth infections among children aged 3 – 14 years in an urban and rural community in Southern Malawi. A randomised cross-sectional survey was conducted in July, 1998. Data were collected through questionnaire interview regarding socio-demographic and environmental conditions from households in both areas. Stool samples were collected from 273 children in the urban community and 280 in the rural. There was a significant difference (p<0.001) in the prevalence of helminth infections between the urban and rural communities, 16.5% and 3.6% respectively. Most of the infections were light (93.2% for Ascaris lumbricodes, 85.7% for hookworm). Large variance to mean ratios of egg intensity within age groups and the total study population suggested a high degree of aggregation of the parasites in the communities. Multiple logistic regression analysis showed that certain groups of children in the urban community were much more likely to develop helminth infection. They included children who had pools of water/sewage around houses (OR = 3.0, 95% CI = 1.4 ñ 6.5), did not wear shoes (OR a 7.1, 95% CI = 2.7 – 19.2), did not attend school (OR = 2.8, 95% CI = 1.2 ñ 6.5), had mothers who had 4 to 8 years of education (OR = 5.2, 95% CI = 2.0 – 14.0), had mothers below 35 years of age (OR = 4.09, 95% CI = 1.39 – 16.28) and living in an urban community (OR = 5.3, 95% CI = 2.6 – 12.1). Efforts to reduce helminth infections should focus on reducing exposures.     

Intestinal parasites in metropolitan Toronto day-care centres.

In 1981, 900 children (aged 3 months to 10 years) and 146 staff attending 22 day-care centres in metropolitan Toronto chosen at random provided a stool specimen in a survey for intestinal parasites. Of the children, 4% to 36% were infected in 20 of 22 centres. Overall, 19% of the children and 14% of the staff had intestinal parasites: 8.6% and 4.0% respectively had Dientamoeba fragilis, and 7.8% and 2.0% respectively had Giardia lamblia. The highest prevalence of dientamebiasis was in the 7- to 10-year-olds, whereas giardiasis was detected most frequently in the 6-year-olds. Infection with intestinal parasites was not correlated with age, sex, duration in the day-care centre, dog ownership, travel history, gastrointestinal symptoms or the proportion of children in the day-care centre who were born in less developed countries. Immigrant children and children of parents born in industrialized countries (including Canada) were more likely to be infected than were children born in Canada of parents from the developing world. Dientamebiasis was associated with cat ownership. Thus, intestinal protozoa--in particular, D. fragilis and G. lamblia--are endemic in Toronto day-care centres.     

广西百色市人体重点寄生虫病调查结果

目的 了解百色市人体重点寄生虫病的流行现状和态势。方法 按照《广西人体重点寄生虫病现状调查实施细则》的要求,选取百色市2个县的3 个调查点开展土源性线虫病( 包括钩虫病、蛔虫病、鞭虫病、蛲虫病) 、带绦虫病、华支睾吸虫病和肠道原虫病的调查。每个调查点调查不少于250 人,共调查800 人。采集监测对象粪便标本,采用改良加藤厚涂片（Kato-Katz法）,对受检者进行粪检（一粪两检）,检查土源性线虫、带绦虫、华支睾吸虫等蠕虫虫卵并计数;土源性线虫调查点加做钩蚴试管滤纸培养法,检查并鉴定粪样中的十二指肠钩虫和美洲钩虫;采用碘液涂片法查肠道原虫包囊或滋养体;透明胶纸肛拭法查蛲虫卵。结果 百色市肠道寄生虫感染者130人,总感染率为16.25%,共检出肠道寄生虫7 种,包括线虫4 种,吸虫1 种,原虫2 种。其中钩虫、蛔虫、鞭虫、蛲虫、华支睾吸虫、结肠内阿米巴、蓝氏贾第鞭毛虫感染率分别为5.38%、3.13%、6.75%、0.50%、0.25%、0.38%、0.38%。土源性线虫占肠道寄生虫感染人数的93.85%。结论 相比百色市第1次、第2次全国人体寄生虫调查和广西少数民族地区寄生虫感染调查的结果,百色市人群寄生虫感染率呈下降趋势。感染人群的分布存在地区间的差异。土源性线虫病是防治的重点,特别是农村地区,少数民族居住地,经济欠发达地区,中小学生和学龄前儿童是以后宣传教育工作的主要对象。     

Comparison of iron and hematological indices in Giardia lamblia infection before and after treatment in 102 children in Ahwaz, Iran.

BACKGROUND: Up to now there have been few reports about hematological alterations induced by Giardia lamblia infection. The aim of this study was to evaluate the effects of giardiasis treatment on hematological indices in children in the Khuzestan area by comparing these indices before and after treatment with metronidazole. MATERIAL/METHODS: One hundred two children ranging in age from 5 to 11 years infected with Giardia lamblia between July 2002 and July 2003 and without histories of other diseases were selected from kindergartens and primary schools in the city of Ahwaz. Diagnosis was based on stool examination. The children were treated with metronidazole (15 mg/kg/day for 5 days); hematological values were determined immediately before treatment and repeated 40-45 days after beginning treatment and compared. RESULTS: Iron deficiency anemia was found in 26.5% of the Giardia-infected children. Mean serum hemoglobin, serum hematocrit, serum ferritin, and the ratio of serum iron to total iron-binding capacity were increased (P<0.0001) and mean red-cell distribution width and iron-binding capacity were decreased after treatment (P<0.0001). CONCLUSIONS: Treating giardiasis in children with metronidazole improves iron indices and it appears that in evaluating anemia one should rule out giardiasis and treat it in asymptomatic cases to aid in better health status in pediatrics.     

Giardiasis and other intestinal parasitic infections in a Manitoba residential school for the mentally retarded.

A case of severely symptomatic giardiasis in a school for the mentally retarded prompted an epidemiologic survey of the institution. The rate of parasitic infection in the children were just under 50%. Multiple infections were common and one child harboured five different protozoa. The yield included known pathogens (Giardia lamblia, Metorchis conjunctus and Diphyllobothrium sp.), protozoa of potential pathogenicity (Dientamoeba fragilis) and other protozoa, the significance of which has yet to be determined. The prevalence of G. lamblia in the index ward was significantly higher than in a control ward matched for age and mobility of the children. The epidemiologic data suggested person-to-person transmission of G. lamblia within the institution. Recommendations for the control of protozoal intestinal infections in custodial institutions are presented.     

Person-to-person transmission of Giardia lamblia in day-care nurseries.

In an outbreak of giardiasis at two day-care nurseries in metropolitan Toranto Giardia lamblia appeared to be transmitted person to person. No common source of infection could be found. The proportions of children infected in the two nurseries were 39% and 17%; infection was spread to 7% and 23% of their household contacts. Of the infected children and household contacts 26% and 30% respectively of those for whom detailed information could be obtained were symptomatic. Canadian children were more likely to be infected and symptomatic than were immigrant children attending the nurseries. The most susceptible ages for infection were 1 to 3 years. The results of this study suggest that all children in day-care nurseries who are infected with G. lamblia should be treated, regardless of whether they are symptomatic.     

Effect of environmental endotoxin exposure on development of pediatric asthma among Egypytian school children

Objective： The aim of this study was to assess school indoor exposure to microbial products and prevalence of asthma and allergies in rural and urban children. Methods： This study was carried on a rural and an urban school. Environmental endotoxin level was measured in multiple samples of the ambient indoor air dust collected on special aseptic filter papers from the two schools. For two hundred children history taking, clinical examination, allergen skin prick test and basic pulmonary func- tion test were preformed. Results： Environmental endotoxin levels showed significantly higher mean values （P 〈0.01 ） in rural school （3 EU/mg） as compared to the urban school （0.1 EU/mg） with （OR=5. 163; 95% CI： 0.95-28）. History of allergic symptoms was significantly more in urban than rural students （ P = 0.01 ）. Mean values of pulmonary function parameters were significantly lower values in urban students compared to rural students. Skin prick test results showed significant reactions to all tested allergens in urban children compared to rural children （ P 〈 0.05 ）. Conclusion： There is an inverse association between environmental exposure to endotoxins and susceptibility for allergic manifestations in school children.     

Associations between rural background and where South Australian general practitioners work

OBJECTIVE: To determine the association between rural background on practice location of general practitioners (GPs) (rural or urban). DESIGN: Comparison of data from two postal surveys. SUBJECTS: 268 rural and 236 urban GPs practising in South Australia. MAIN OUTCOME MEASURES: Association between practice location (rural or urban) and demographic characteristics, training, qualifications, and rural background. RESULTS: Rural GPs were younger than urban GPs (mean age 47 versus 50 years, P < 0.01) and more likely to be male (81% versus 67%, P = 0.001), to be Australian-born (72% versus 61%, P = 0.01), to have a partner (95% versus 85%, P = 0.001), and to have children (94% versus 85%, P = 0.001). Similar proportions of rural and urban GPs were trained in Australia and were Fellows of the Royal Australian College of General Practitioners, but more rural GPs were vocationally registered (94% versus 84%, P = 0.001). Rural GPs were more likely to have grown up in the country (37% versus 27%, P = 0.02), to have received primary (33% versus 19%, P = 0.001) and secondary (25% versus 13%, P = 0.001) education there, and to have a partner who grew up in the country (49% versus 24%, P = 0.001). In multivariate analysis, only primary education in the country (odds ratio [OR], 2.43; 95% CI, 1.09-5.56) and partner of rural background (OR, 3.14; 95% CI, 1.96-5.10) were independently associated with rural practice. CONCLUSION: Our findings support the policy of promoting entry to medical school of students with a rural background and provide an argument for policies that address the needs of partners and maintain quality primary and secondary education in the country.     

Giardiasis in Mount Isa, north-west Queensland

A random survey of 680 dwellings was undertaken to determine the prevalence and mode of transmission of Giardia intestinalis in Mount Isa. Of the population, 4.5% were shown to have cysts in their stools; the highest prevalence rate of 12.0% occurred in children aged one to five years. Epidemiological studies strongly suggest that the disease, which is endemic in the city, is being transmitted by hand-to-mouth contamination; schools, preschools, kindergartens and play groups are important foci of transmission. No evidence was found that the parasite was being brought into the city from outside, or that people were acquiring it from water or domestic pets. Symptoms consistent with giardiasis were more commonly present in children than in adults. Approximately two-thirds of infected persons were asymptomatic. The diagnosis of giardiasis as based on symptoms alone was inadequate, although more likely to be correct in children than in adults.     

Intestinal parasitism in Magama Gumau rural village and Jos township in north central Nigeria

OBJECTIVE: To determine the prevalence of intestinal parasitosis in one rural village and one urban centre in North Central Nigeria. METHODS: A total of 111 single stool specimens from all the volunteered rural dwellers and 93 specimens from randomly selected urban dwellers were examined using Formol-ether and modified Ziehl-Neelsen techniques; during the months of June and July 2005. A questionnaire was completed for each subject and the nutritional status of the adults was assessed using the anthropometric measurements (weight and height for age and Biomass index). RESULTS: The results suggest very high prevalence rates of intestinal parasitosis of 72.1% and 69.9% for the rural and urban populations respectively. All the age groups were infected. The males in the rural area had a prevalence of 69.2% as against 74.6% in females (P>0.05); while in the urban area, the males were more significantly infected (77.4%) compared with the females with 66.1% (P< 0.05). Those with normal BMI (18.5-24.9 kg/m2) had the highest prevalence of 79.3% and 72.4% for the rural and urban populations respectively. The prevalence of the parasites in the rural and urban populations respectively were: Entamoeba coli (16.2% and 9.7%); E. histolytica (18.9% and 18.3%); E. hartmani (1.8% ad 0.0%); Endolimax nana (16.2% and 18.3%); Iodamoeba butschlii (0.0% and 1.1%); Giardia lamblia (7.2% and 4.3%); Schistosoma mansoni (9.9% and 0.0%); Strongyloides stercoralis (0.9% and 0.0%); Hookworm (4.5% and 5.4%); Ascaris lumbricoides (1.8% and 0.0%); Enterobius vermicularis (0.0% and 1.1%); Cryptosporidium parvum (29.7% and 19.4%); and Enterocytozoon bieneusi/Encephalitozoon intestinalis (39.6% and 47.3%). Polyparasitism was recorded in 48.6% of the rural subjects and 36.6% of the urban subjects. CONCLUSION: The study has shown a very high prevalence of intestinal parasitosis in both the rural and urban populations and that C. parvum and E. bieneusi/E. intestinalis are harboured by apparently healthy individuals.     

Observations on natural and experimental infections with Giardia isolated from cats

The course of infection with Giardia was studied in (a) naturally infected cats and (b) experimentally infected Mongolian gerbils using Giardia cysts isolated from cats. Natural infection was characterized by: (a) a latent period of 11 to 13 days, (b) the pattern of cyst release which was either continuous or intermittent during the acute phase of infection and (c) elimination of the infection in four to five weeks after exposure. Mongolian gerbils were found to be susceptible to infection with Giardia isolated from cats. The course of infection in gerbils was characterized by intermittent cyst release and elimination of the infection in about three weeks. The pattern of cyst release in gerbils infected with Giardia isolated from cats was similar to the previously reported pattern of cyst release in gerbils infected with Giardia isolated from humans. The possible role of pets in the zoonotic transmission of giardiasis is discussed.     

Epidemiological assessment of intestinal parasitic infections in dogs at animal shelter in Veracruz,Mexico

Objective:To determine the prevalence of infection with intestinal parasites in 101 dogs in an animal shelter in Veracruz.Mexico,and investigate whether any general characteristics of the dogs were associated with infections.Methods:Parasitologiesl examination of fecal samples from the dogs was performed by means of centrifuge-flotation using Sheather's sucrose and zinc sulfate flotation media.In addition,hematocrit was determined in each canine blood sample.Results:Intestinal parasites were found in 99(98.0%) of the 101 dogs studied.About five different intestinal parasites were identified:Ancylostoma caninum in 89 dogs(88.1%).Giardia canis in 46(45.5%).Unciiuiria stenocephalia in 43(42.6%).Trichuris vulpis in 19(18.8%)and Strongyloides canis in 16(15.8%).Multivariate analysis showed:I) Giardia infection was associated with young age and mixed breed;2) Ancylostoma was associated with young age and no rabies vaccination:and 3) Strongyloides was associated with no rabies vaccination.Unciiuiria and Trichuris infections were not associated with the variables assessed.Conclusions:A high prevalence of intestinal parasites was found in the dogs studied.This suggests that the environment is highly contaminated with intestinal parasites.Preventive and therapeutic measures should be taken against infection with intestinal parasites in dogs in this region.     

集安县乡村儿童少年肠道寄生虫调查报告

本文作者在集安县乡村初中、小学和幼儿园调查了501人,蛔虫感染率为79.2％,其他尚有鞭虫、蛲虫、钩虫、东方毛圆线虫、猪肉绦虫和溶组织内阿米巴,其中尚有2.4％受检者同时感染两种以上肠道寄生虫。提出了乡村儿少肠道寄生虫流行因素和防治原则,并比较了饱和盐水浮聚法在粪检中提高检出率的优点。     

A contribution to the study of tinea capitis in Lusaka, Zambia

A study of tinea capitis in urban and rural schools of Lusaka revealed two dermatophytes, vis., Microsporum langeroni and Trichophyton violaceum as the causative agents of tinea capitis among school children. Tinea capitis was more common among boys (18.0%) than girls (14.7%), with prevalence of 16.8% and a peak infection at 9-11 years for both sexes. Clinically, most cases due to both M. langeroni and T. violaceum were non-inflammatory. The inflammatory cases were caused by T. violaceum. The higher number of infected children from squatter and low-cost areas was statistically highly significant compared to children from high-cost areas. A higher number of rural children were infected with tinea capitis than children in urban Lusaka. T. violaceum was the only dermatophyte species isolated in rural Lusaka, while in urban Lusaka, both T. violaceum and M. langeroni were isolated.     

Intestinal parasites in a rural community in Kenya: cross-sectional surveys with emphasis on prevalence, incidence, duration of infection, and polyparasitism

A cross-sectional survey of intestinal parasitic infection in a rural community, Nderu, in Kiambu District, Kenya, was carried out in 1985 by examining 1129 individuals from 203 households (about 25% of the total population). This was followed by 3 more cross-sectional surveys, in January, May and October 1986, of 56 families comprising 461 individuals, who had also participated in the first survey. In the first survey, 81.4% of the sample was positive for at least one intestinal parasite and 78% was positive for intestinal protozoa. 72.7% of those infected had multiple infections. The prevalence of most of the protozoa increased with age but that of Giardia lamblia peaked in the 0 to 4 year class at 35.5%. Females were infected more often with several of the protozoa, but males with Ascaris. People living in larger households were more often infected with Entamoeba histolytica and Iodamoeba butschlii, while the opposite was true of H. nana and tended to be for Giardia. Significant positive associations between parasite species were common at all surveys, especially among the amoebae. The majority of negative associations were for Giardia. Unformed stools were significantly associated with Giardia, Blastocystis, and trophozoites of Trichomonas hominis and Chilomastix mesnili. Endolimax nana and Entamoeba coli were found more often in formed stools. Estimates of daily incidence, and duration of infection in days, were calculated for 11 parasites. The longest mean estimated duration of infection for any species was 237 +/- S.D. 151.4 days for H. nana and the shortest was 41.6 +/- S.D. 0.4 days for T. hominis.     

DETECTING GIARDIA LAMBLIA ANTIGEN IN FECAL MATTER WITH COUNTERIMMUNO-ELECTROPHORESIS IN DIAGNOSIS OF GIARDIASIS

Feces specimens from 35 patients with parasitologically confirmed giardiasis, 41 with acute gastroenteritis, 23 with acute bacillary dysentery, 40 normal persons as well as 15 jirds experimentally infected with Giardia lamblia were used for detecting parasite antigen by counterimmunoelectrophoresis (CIE). It revealed that 33 (94%) of the 35 patients with giardiasis and 14 (93%) of 15 infected jirds were positive, while the other cases, either normal person or normal jird were negative. CIE was also performed in 4 with giardiasis before and after metronidazole treatment. Prior to metronidazole administration, they were all CIE positive, but from the second day on, all became CIE negative. Apparently, detecting giardia antigen in feces specimens by CIE is not only sensitive in detecting current infection but also helpful in evaluating the effects of antigiardia agents on giardiasis.     

青海省中小学生肠道寄生虫感染的调查分析

目的 明确我省中小学生肠道寄生虫病的分布流行现状,为制定防治措施提供科学依据。方法 采用卢戈氏碘液片法检查肠道原虫;改良加藤氏厚涂片法检查蠕虫卵;肛周透明胶纸肛拭法检查蛲虫卵（12岁以下儿童）;试管滤纸培养法检查线虫幼虫。结果 调查20个县（市）32个调查点中的3485名中小学生,寄生虫总感染率为58.77%。男、女感染率分别为59.24%,蛲虫25.04%,鞭虫0.92%,结肠内阿米巴7.12%。蓝氏贾第鞭毛虫5.65%,溶组织内阿米巴0.52%,哈氏内阿米巴0.34%,微小内蜒阿米巴3.53%,布氏嗜碘阿米巴0.89%,人芽囊原3.07%。海东农业区学生感染最高（69.53%）,青南牧区最低（37.40%）。感染2种以上寄生虫者占22.95%。