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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

The relationship of hookworm infection, anaemia and iron status in a Papua New Guinea highland population and the response to treatment with iron and mebendazole.

In 345 apparently healthy Papua New Guinea male subjects, predominantly highlanders, 89% of whom were infected with hookworm (Necator americanus), there was a statistically significant inverse correlation of hookworm egg count with haemoglobin and serum ferritin level, but no significant correlation with serum albumin, folate or B12 values. A sub-group of 128 was chosen for a six-month study on the effect of treatment with the anthelmintic mebendazole and/or parenteral iron on haemoglobin and serum ferritin levels. Mebendazole-treated subjects remained worm-free and the hookworm egg counts of the controls decreased during the study period. Parenteral iron treatment had the expected effect of raising haemoglobin to a normal level. There was a statistically significant improvement in haemoglobin level in all treated groups but not in the control. Serum ferritin levels decreased significantly in all groups, but more in the control than in the treated groups, although treatment groups were not significantly different. Although probable inadequate uptake of iron by the subjects and blood donation by some subjects was apparently more detrimental to iron status than hookworm infection, the results of this study support the view that hookworm infection in this country contributes to lowered haemoglobin levels and iron status.

Anemia, Hypochromic

Changes in the structural and functional properties of human eosinophils during experimental hookworm infection.

Normal volunteers were infected with hookworm larvae Necator americanus. Peripheral blood counts showed a mean of 524 +/- 29 eosinophils/mm3 of blood before infection and a mean of 3,008 +/- 456 eosinophils/mm3 of blood during infection (P less than .01). Absolute numbers of neutrophils did not change. Eosinophils and neutrophils from the infected period were compared with the noninfected state in each subject. The percentage of hypodense eosinophils increased from a mean of 34% +/- 13% to 80% +/- 7% during infection (P less than .05). Superoxide production of eosinophils increased from a mean of 56 +/- 9 to 97 +/- 12 nmol of O2-./10(6) cells per 60 min (P less than .05) during infection. Chemotaxis of eosinophils to Escherichia coli endotoxin-activated serum increased from a mean average distance migrated of 19 +/- 2 micron (P less than .05), whereas neutrophil responsiveness did not change. This is the first report of changes in eosinophil density and stimulation of eosinophil function in normal hosts experimentally infected with hookworm. The data indicate that hookworm infection preferentially increases eosinophil production and activity with little effect on neutrophils.

Chemotaxis, Leukocyte

[Differential diagnostic value of occult blood in stool in hookworm infection in the Third World. Study from Papua New Guinea].

In 633 persons of the Madang province in Papua-New Guinea hookworm-infection, blood hemoglobin and the presence of blood in stools were studied. 60% of the subjects were infected with hookworm (Necator americanus). There was a significant linear correlation between the intensity of hookworm infection and blood haemoglobin level. The Colo-Rectal test gave positive results in 17% of the cases without worm-infection. In infected persons, the Colo-Rectal test gave an increasing rate of positive results as the parasite infection increased: 24% for subjects with low levels of infection, and 57% and 67% for moderate and high levels, respectively. The mean blood-haemoglobin level was lower in persons with positive Colo-Rectal-Test and hookworm infection (11.8 g%) than among those with negative Colo-Rectal-Test and hookworm infection (15.0 g%, p < 0.01). In young populations with a known high prevalence of hookworm infection, Colo-Rectal test is therefore suitable for the detection of moderate or severe hookworm infections. It may serve as a simple and useful method to work up anaemia is such populations.

Adolescent

Hookworm infection and disease: advances for control.

Advances in epidemiology and in control strategies of hookworm infection and associated disease were reviewed. Recent estimates indicate that hookworms infect approximately 1.3 billion people worldwide, and 96 million suffer from associated morbidity, including also insidious effects on nutritional status and on physical and intellectual development. Recent research studies on iron loss and iron-deficiency anaemia associated to hookworm infection were irondeficiency anemia associated to hookworm infection were reviewed. Recommendations for planning strategies for the control of hookworm infection were addressed and epidemiology, targets, chemotherapy, health education, sanitation, monitoring and evaluation in helminth control programmes were discussed. Special relevance was given to chemotherapy with new, single dose broad spectrum, safe anthelminthic drugs as the mainstay of control strategy to reduce intensity of infection, iron-deficiency anaemia and other morbidity indicators associated with hookworm infections. For the control of transmission of hookworm infection, periodic chemotherapy should be implemented in the context of ongoing improvement of sanitation and promotion of health education. These elements should be integrated into the prevailing system of primary health care and must be based on multisectoral collaboration to ensure sustainability of control programmes.

Ancylostoma

Hookworm infection and iron stores: a survey in a rural community in Bali, Indonesia.

A study of the rural population of the village of Belumbang, Province of Bali, Indonesia, has been conducted to assess the relationship between intensity of hookworm infection (hookworm egg count) and iron stores, hemoglobin level or hematocrit. There was a significant negative correlation between serum ferritin level and hookworm egg count. However no correlation was found between hookworm egg count and hemoglobin level or hematocrit. In a separate analysis the above correlation could be shown in male hosts but not in female hosts. It is concluded that hookworm infection, even in light infection, can interfere with iron stores, but in female hosts this effect might be masked by other factors.

Anemia, Hypochromic

A comparative study on the efficacy of albendazole and mebendazole in the treatment of ascariasis, hookworm infection and trichuriasis.

A comparative study of the efficacy of albendazole and mebendazole was carried out in Pattani Province in the southern part of Thailand. One hundred and ninety-six patients with single or multiple infections with Ascaris, hookworm, and Trichuris were randomized into 4 groups for different treatments. Stool examination by Kato-Katz technique were done before and on day 14 after treatment. Results of the study showed that (1) a single dose of 300 mg mebendazole (locally produced) resulted in cure rates of 50%, 0% and 0% and egg reduction rates of 87.3%, -15.3%, and 28.3%, for ascariasis, hookworm infection and Trichuris respectively; (2) a single dose of 300 mg mebendazole (original) resulted in cure rates of 100.0%, 9.1%, and 43.3%, and egg reduction rates of 100.0%, 72.0%, and 77.9%, for Ascaris, hookworm, and Trichuris respectively; (3) a single dose 500 mg mebendazole (original) resulted in cure rates of 100.0%, 30.2%, and 70.3%, and egg reduction rates of 100.0%, 70.4% and 89.9%, for Ascaris, hookworm, and Trichuris respectively and (4) a single dose of 400 mg albendazole (original) resulted in cure rates of 100.0%, 84.3%, and 67.4%, and egg reduction rates of 100.0%, 96.0% and 87.0%, for Ascaris, hookworm, and Trichuris respectively. Both mebendazole and albendazole are safe and no side effects were observed. The results of this study suggested that albendazole is the preferred benzimidazole derivative for mass treatment of multiple infections with Ascaris, hookworm, and Trichuris.

Adolescent

A randomized controlled trial comparing mebendazole and albendazole against Ascaris, Trichuris and hookworm infections.

The efficacies and side effects of single dose treatments with 500 mg mebendazole (Janssen Pharmaceutica) and 400 mg albendazole (SmithKline Beecham) against intestinal nematodes were compared in a single-blind, randomized controlled trial among 2294 children aged 6 to 12 years on Pemba Island, Zanzibar, among whom infections with Ascaris, hookworms and Trichuris were highly prevalent. Both drugs were highly effective against Ascaris, with cure rates of over 97%. The cure rates for Trichuris were low, but mebendazole was significantly better than albendazole and produced a greater reduction in the geometric mean egg count. Mebendazole was inferior to albendazole in curing hookworm infections and in reducing the geometric mean egg count. There was no difference in the frequency of side effects reported by heavily infected children treated with either drug. In a trial on 402 children, 500 mg mebendazole (Janssen) was compared with a generic version of the drug, 500 mg mebendazole (Pharmamed). No difference was apparent in the efficacies of the 2 treatments against any of the 3 parasites studied.

Albendazole

Response of dogs to challenge with Ancylostoma ceylanicum during the tenure of a primary hookworm infection.

A model of human hookworm infection has been developed which shows that dogs currently infected with small numbers of hookworms are considerably resistant to a challenge infection with a large inoculum of infective larvae. Two groups of dogs were infected with 500 larvae and four weeks after infection one group together with a previously uninfected control group were infected with 5,000 larvae and followed for six weeks. When compared with the secondary infection control dogs, faecal egg excretion and adult worm burdens were reduced by an average of 83 and 78% respectively. Infections had no significant effect on total white cell counts, platelet levels or spontaneous, phytohaemagglutinin- and antigen-induced lymphocyte transformation among the three groups of dogs. Dogs previously uninfected with hookworm developed a marked anaemia when infected with 5,000 larvae but this was not observed in the superinfected group. An eosinophilia developed in all groups and there were no significant differences among the three groups of animals. Specific IgM antibodies developed transiently in all groups of dogs two weeks after infection. IgG antibody levels were significantly greater in the superinfected animals one, two and three weeks after challenge infection compared with the secondary infection control animals; by four weeks there was no significant difference between the two groups of animals. Both groups given the large inoculum of larvae developed specific IgA antibodies one week after the challenge infection and these continued to rise in the superinfected group until termination of the experiment. It is concluded that dogs currently infected with the hookworm, Ancylostoma ceylanicum, demonstrate the development of functional protective immunity.

Ancylostomiasis

Prevalence of hookworm infection, anaemia and faecal blood loss among the Yupno people of Papua New Guinea.

The present report describes a study of hookworm infection, anaemia and the presence of blood in stool among the inhabitants of the Yupno area in Madang Province, Papua New Guinea. The study group comprised 588 persons of all age groups. A second group of 45 patients attending the Madang General Hospital, in the provincial capital on the coast, was used for comparison. In the Yupno area, 59% of the subjects were infected with hookworm; in the coastal group the infection rate was 82%, which was significantly higher. There is therefore a moderate prevalence of hookworm infection in the Yupno area, which does not impair the health of the population to any great extent. In both places there was a clear increase in the infection rate between the group of children 1-5 years old and the older groups. The mean blood haemoglobin level was 15.1 g/dl among the Yupno, which was significantly higher than that of the second group (10.7 g/dl). There was a significant negative linear correlation between the intensity of hookworm infection and blood haemoglobin level. The Colo-Rectal-Test for blood in stool was used on samples from 145 persons in the Yupno and from 43 in the coastal group. The test gave positive results in 17% of the cases without worm infection. In infected persons, the Colo-Rectal-Test gave an increasing rate of positive results as the parasite burden increased: 24% for subjects with low levels of infection, and 57% and 67% for moderate and high levels, respectively. The Colo-Rectal-Test is therefore a simple method for the detection of faecal blood loss in populations with a high prevalence of hookworm infection. However, it is not useful as an instrument for general screening for hookworm infections.

Adolescent

Distribution of hookworm infection in Cameroon.

Prevalence of hookworm infection was measured in Cameroon during a national survey carried out for a schistosomiasis research project. The survey provided a representative sample of the 10-19 year age group for each one of the 49 administrative divisions. Prevalences were low in the Extreme North province with a sahelian climate. Prevalences were high in the provinces with an equatorial climate except for the Centre province which is more developed. Regions with tropical Cameroonian climate, which receive a very heavy rainfall, showed the highest prevalences. Urbanized areas had lower infection rates than rural areas. It should not be assumed that hookworm prevalence is uniformly high throughout a tropical country. Since hookworm distribution shows wide variations, large control programmes should start with a thorough evaluation of the situation.

Adolescent

Parasitological, hematologic, and immunologic responses in acute and chronic infections of dogs with Ancylostoma ceylanicum: a model of human hookworm infection.

A model of human hookworm infection has been defined with a strain of Ancylostoma ceylanicum that is known to be infective for humans. In the first experiment, dogs were infected with between 150 and 12,150 filariform larvae and followed up for six weeks. A direct relation was found between the size of infecting dose, fecal egg excretion, intestinal adult worm burden, and worm distribution in the bowel. Dogs with heavy infection developed bloody diarrhea and iron-deficient anemia. In the second experiment, dogs infected with 2,000 larvae excreted ova until autopsy 36 weeks after infection. Normocytic anemia and blood eosinophilia coincided with maximal egg excretion. Transitory lymphocyte stimulation was seen with adult worm antigen. The specific IgM antibody response was transient, but IgG antibodies persisted indefinitely. Marked skin immediate hypersensitivity and Arthus (but no delayed) hypersensitivity reactions were seen to injected larval and adult antigens. Thus, dogs develop both hookworm disease and chronic infections similar to those seen in humans.

Acute Disease

Prevalence of hookworm infection and its association with low haematocrit among resettlers in Gambela, Ethiopia.

A cross-sectional survey of hookworm infection and haematocrit (HCT) levels was conducted in 7 resettled villages and 3 indigenous villages on sample populations selected by two-stage random sampling. Of 614 resettled persons and 187 indigenous persons, 65.5% and 60.4% respectively were infected with hookworm. Mean haematocrits for 664 resettled and 222 indigenous persons were 33.1% and 35.2%, respectively. A significant association (odds ratio = 2.65) was found between low haematocrit level (below the median for the sample population) and hookworm infection in the resettled population. Suggestions are made on the need for further studies and intervention programmes.

Adolescent

Diagnosis of Strongyloides and hookworm infections: comparison of faecal and duodenal fluid microscopy.

Faecal microscopical diagnosis of Strongyloides and hookworm infections is insensitive. We have therefore compared duodenal fluid and faecal microscopy for detection of these parasites in a group of 292 patients being investigated for gastrointestinal symptoms who were examined by both techniques. Thirty-three of these patients (8%) were infected with Strongyloides stercoralis and 88 (30%) had hookworm infections. Microscopical examination of up to 3 faecal specimens detected only 33% and 65% of patients with Strongyloides and hookworm infections, respectively. Microscopical examination of a single specimen of duodenal fluid was more sensitive for detection of strongyloidiasis, identifying 76% of patients; the parasite was found exclusively in duodenal fluid (and not in faeces) in 67% of patients. For hookworm, the diagnostic sensitivity was similar with both techniques but duodenal fluid microscopy detected some patients (35%) who had not been identified by faecal microscopy. This study confirms previous work indicating the insensitivity of faecal microscopy in these infections and emphasizes the need to consider routine examination of duodenal fluid to exclude chronic strongyloidiasis. This may have particular relevance for south-east Asian war veterans and immunocompromised patients.

Ancylostomatoidea

Some epidemiological aspects of hookworm infection among the rural population of Bali, Indonesia.

Stool examination using direct smear method, Kato-Katz thick smear technique and modified Harada Mori test tube cultivation method were done on 2,331 people among the rural population of Bali. The serum ferritin was examined by ELISA technique and hemoglobin concentration by cyanmethemoglobin technique. Overall prevalence of hookworm infection was 24.02% with heterogeneity in local prevalences. The highest prevalence was found in wet highland area (46.3%), followed by wet lowland (27.7%), dry highland (14.2%) and dry lowland (10.9%). The majority of hookworm infection cases were associated with Ascaris and Trichuris infections. Most of the hookworm infections (73.3%) were light/very light in intensity with a mean EPG of 619. The prevalence and intensity of infection were increasing with age, and the age-prevalence and age-intensity curves were slightly convex. There was no significant difference of prevalence or intensity of infection between males and females. The condition and humidity of soil found to be an important determinant for prevalence of hook-worm infection. The frequency distribution of the intensity of hookworm infection showed an over-dispersed distribution pattern with 10% of people harboring more than 63% of parasite burden as measured by EPG. The prevalence of anemia was higher, but not statistically significant, in hookworm infected persons compared with people without infection. But this study failed to show a significant correlation between intensity of infection with hemoglobin level. There was a significant correlation between serum ferritin level with intensity of infection.

Age Factors

The prevalence of hookworm infection, iron deficiency and anaemia in an aboriginal community in north-west Australia.

OBJECTIVE: To determine the prevalence of hookworm infections, iron deficiency and anaemia in an Aboriginal community in the north of Western Australia. DESIGN AND SETTING: A cross-sectional survey conducted in 1992, examining faecal specimens and blood samples from Aboriginals and non-Aboriginals in a remote coastal community in the north of Western Australia. PARTICIPANTS: All those living in the community at the time of the survey. MAIN OUTCOME MEASURES: Parasite status and haematological values for haemoglobin, serum iron, ferritin, transferrin and mean red cell volume. RESULTS: Infections with hookworm were present throughout the Aboriginal population (77%; n = 243), with the highest prevalence in children aged 5-14 years (93%; n = 74). Hookworm was not detected in non-Aboriginals (n = 24). Iron deficiency was common throughout the Aboriginal population, especially in children aged 5-14 years (79%; n = 68) and women aged over 14 years (72%; n = 65). Anaemia was highly prevalent among Aboriginal children aged 5-14 years (84% in hookworm-positive children, 75% in hookworm-negative) and women aged over 14 years (63% in hookworm-positive women, 31% in hookworm-negative). Aboriginals over 14 years of age who had hookworm (n = 82) had significantly lower levels of haemoglobin, serum iron and serum ferritin, a lower mean red cell volume and significantly higher transferrin levels than uninfected Aboriginals (n = 38) and non-Aboriginals (n = 19) in the same age group. Hookworm infections were associated with anaemia (P < 0.01) and iron deficiency (P < 0.01) in people over 14 years of age. The species of hookworm, determined after examining 13 larval cultures and two adult worms, was found to be Ancylostoma duodenale. CONCLUSION: Infections with A. duodenale are endemic in Aboriginals in this community, and are likely to contribute to the high prevalence of iron deficiency and anaemia observed in the Aboriginal population, particularly in children and women.

Adolescent

Immunosuppression in Nigerians with hookworm infection.

T rosette cells results in patients with (Necator americanus and Ancylostoma duodenale) hookworm infection, divided into groups on the basis of the degree of anaemia (Group I had marked anaemia Hb 1-7, hypochromia ), Group II had moderate anaemia (Hb 8-11, hypochromia ++) and Group III had no signs of anaemia despite the underlying hookworm infection), were compared with results in 28 healthy controls who had no signs of other infection and excreting no ova of hookworm or other parasites. The level of sheep erythrocyte rosette-forming T-lymphocytes (SE-TL) in the patients (Group I:42 +/- 8%; Group II:45 +/- 11%; Group III:47 +/- 6%) was markedly reduced compared to controls (58 +/- 13%) (P < 0.001). The leucocyte migratory responses to purified protein derivative (P.P.D); were significantly (P < 0.05) reduced in all the subgroups as compared with the controls. The results support the hypothesis of the existence of immunosuppression in patients with hookworm infection.

Adolescent

[Field studies on different control schemes for hookworm infection].

Three different control schemes including selective chemotherapy, a combination of selective chemotherapy and management of fecal disposal and mass treatment with mebendazole-medicated salt were implemented for the control of hookworm infection in Luwo Town and Taiping Village, Wuming County, Guangxi Zhuang Autonomous Region during 1971-1990. Through ten years of selective chemotherapy, the results showed that the hookworm infection rate dropped from 42.6% to 3.9% and the infection intensity from 425.6 eggs per gram faeces to 1.6 eggs per gram faeces. After seven years of selective chemotherapy combined with management of fecal, the hookworm infection rate dropped from 58.7% to 10.9% and the infection intensity from 111.5 eggs per gram faeces to 8.5 eggs per gram faeces. However, 3 years after the termination of the combined treatment, the hookworm infection rate increased to 14.5%. As for the implementation of the third scheme, mebendazole-medicated salt was given at 100 mg daily for 30 consecutive days or at 50 mg daily for 30 consecutive days. Stool examination was made one year after the treatment, the results showed that the infection rate of the inhabitants dropped from 36% and 36% to 2% and 1.3%, respectively, and the infection intensity dropped from 110.3 and 246 eggs per gram faeces to 1.3 and 0.24 eggs per gram faeces. After three years, the infection rate of inhabitants remained under 2% and the infection intensity under 1 egg per gram faeces. It was concluded that mass treatment with mebendazole-medicated salt might be the most practical scheme for the control of hookworm infection.

Ancylostomiasis