Biomedical subjects

B J Vennervald

Publications and source records attributed to B J Vennervald.

At least 37 records · Page 2Linked to original sources

PubMed1997

The impact of zinc supplementation on Schistosoma mansoni reinfection rate and intensities: a randomized, controlled trial among rural Zimbabwean schoolchildren.

OBJECTIVES: To assess the effect of zinc supplementation on susceptibility to S. mansoni reinfections among schoolchildren. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING AND SUBJECTS: 313 rural Zimbabwean schoolchildren (144 boys and 169 girls), 11-17 y). INTERVENTIONS: Supplementation with zinc (30 or 50 mg) or placebo on schooldays for 12 months. Due to drought, a food programme was in operation during the last eight months of the study. OUTCOME MEASURES: S. mansoni and S. haematobium reinfection rates and intensities. RESULTS: There was no difference in reinfection rates between the zinc and placebo groups (25 vs 29%, P = 0.46). However, the median intensity of S. mansoni reinfection, although low in both groups, was significantly lower in the zinc than in the placebo group (7 vs 13 eggs per gram of faeces, P = 0.048). No difference in either S. haematobium reinfection rates or intensities were seen. CONCLUSIONS: Zinc supplementation reduced the intensity of S. mansoni reinfections. Although the intensities of reinfection were very low, the finding probably reflects a biological effect of zinc that could be of public health importance in settings with higher transmission.

Adolescent↗

PubMed1996

Worm establishment and egg production of Schistosoma japonicum in pigs infected by percutaneous methods or intramuscular injection.

Worm establishment and egg production were compared in Landrace/Yorkshire crossbred pigs infected with Schistosoma japonicum using 3 different infection techniques. S. japonicum worm establishment and overall egg production following intramuscular injection of cercariae suspended in Iscove's medium exceeded that in pigs infected by the leg immersion or the coverslip percutaneous technique. However, the egg production per mature female was similar for all three infection methods. The results support the use of intramuscular injection of medium-suspended cercariae as an effective, safe, rapid and convenient infection method for studies on the population biology of S. japonicum in pigs when dermal cercarial penetration is not required.

Animals↗

PubMed1996

Specific immunoglobulin measurements related to exposure and resistance to Schistosoma mansoni infection in Sudanese canal cleaners.

The present work comprises a longitudinal study of Schistosoma mansoni infection in occupationally hyper-exposed canal cleaners in the Sudan and the influence of chemotherapy on humoral immune parameters. The study groups included chronically infected canal cleaners (n = 19), newly recruited canal cleaners (n = 17), normally exposed adults (n = 31), school children (n = 46) and Sudanese negative controls (n = 48). Previous studies of the same canal cleaners have demonstrated that chronically infected canal cleaners were more resistant to reinfection than newly recruited canal cleaners. ELISA was used to detect specific IgE and IgG subclasses in response to whole worm antigen (WWH) and soluble egg antigen (SEA) before and 3 months after praziquantel treatment in the groups of canal cleaners and before and 1 year after treatment in normally exposed adults. When intensity of infection was correlated with IgE antibody response, the resistant group of canal cleaners (those who stopped passing ova after treatment) showed a significant positive correlation between intensity of infection and specific IgE to WWH (Spearman's correlation coefficient = 0.49, P < 0.05) compared with a highly significant negative correlation in the susceptible group (acquired new infection after treatment, Spearman's correlation coefficient = -0.94, P < 0.01). Normally exposed adults and school children had significantly less specific IgE to WWH than canal cleaners, while chronically infected canal cleaners had significantly higher levels of specific IgG1 to WWH than newly recruited canal cleaners and school children, and significantly higher levels of specific IgG4 to WWH than school children. There was a significant increase in specific IgG1 and IgG4 to WWH, 3 months after treatment, in newly recruited canal cleaners and a significant decrease, 1 year after treatment, in normally exposed adults. None of the groups studied after treatment showed a significant change in their specific IgE to WWH. Normally exposed adults had significantly lower levels of specific IgE to SEA than newly recruited canal cleaners, and significantly lower levels of specific IgG1 to SEA than other infected groups. Both newly recruited canal cleaners and school children had significantly higher levels of specific IgG2 to SEA than persons in other groups. Only small differences between groups were observed with regard to specific IgG3 and IgM to SEA. Specific IgG4 to WWH and SEA showed different patterns after treatment between the resistant and susceptible groups of canal cleaners. The resistant group maintained the same level of IgG4 to WWH after treatment compared with a significant increase in the susceptible group. On the other hand, levels of specific IgG4 to SEA showed a highly significant decrease after treatment in the resistant group. In contrast, the same antibody subclass increased after treatment in the susceptible group. Generally, results show an association between IgE and IgG1 responses to WWH and resistance to reinfection. In contrast, an association was observed between IgG2 and IgM responses to SEA and susceptibility to reinfection.

Adult↗

PubMed1996

Age-related antibody profiles in Schistosoma haematobium infections in a rural community in Zimbabwe.

Antibody responses to soluble Schistosoma haematobium egg (SEA) and worm (SWA) antigens in a rural Zimbabwean study population were examined by ELISA. One hundred and sixteen S. haematobium infected and 124 non-infected individuals representing individuals greater than five years old, were included. Non-endemic control sera were obtained from a schistosomiasis non-endemic part of Zimbabwe and from Norwegian blood donors. A possible association between IgE antibody responses and resistance to S. haematobium infection was indicated by a negative correlation between IgE anti-SEA levels and intensity of S. haematobium infection, and by a positive correlation between IgE responses to SEA and SWA and age. Similarly, an association between IgA and anti-SWA and resistance to S. haematobium was suggested by a negative correlation to intensity of infection and a positive correlation with age. A probably association between IgM and IgG4 with susceptibility to S. haematobium infection was described; intensity of S. haematobium infection correlated positively with IgG, IgG4 and IgM responses to SEA and with IgG4 and IgM responses to SWA, also age correlated negatively with IgG4 and IgM responses to SEA and with IgG4 responses to SWA. These findings support the concept of IgG4 and IgM as blocking antibodies. Significant positive correlations between antibody responses to SEA and SWA suggests cross-reactivity between eggs and adult worms. In addition, the recognition by IgE and IgG4 of the same schistosomulum antigens in immunoblotting suggests competitions for the same antigens.

Adolescent↗

PubMed1996

Ultrasonographic organometry: liver and spleen dimensions among children in Zimbabwe.

Attempts have been made to develop a staging system of sonographic Schistosoma mansoni morbidity for use in epidemiological studies and for evaluation of control programmes. Therefore, normal dimensions of livers and spleens in children in countries with endemic S. mansoni infections need to be established. Normal dimensions of livers and spleens are presented, based on examination of 144 Zimbabwean children between 8 and 16 years of age found to be S. mansoni egg negative 12 months after treatment with praziquantel. Based on the liver and spleen measurements, an index of liver size and the spleen volume were calculated. Height was employed as the independent variable in all multiple regression models. The organometric data are presented as prediction plots, with observed values and fitted regression line with 95% confidence and prediction intervals. The mean spleen volume was 30% larger for boys than for girls, whereas there was no consistent difference in liver size. No effect of growth Z-scores was seen. The measurements were compared with normal dimensions of livers of German children. For a given height, the mean index of liver size was lower in Zimbabwean than in German children, but inter-observer variation could be a possible explanation for this difference.

Adolescent↗

PubMed1996

Circulating anodic antigen (CAA) levels in different age groups in a Zimbabwean rural community endemic for Schistosoma haematobium determined using the magnetic beads antigen-capture enzyme-linked immunoassay.

A simplified version of the magnetic bead antigen-capture enzyme-linked immunoassay (MBAC-EIA) was used to detect circulating anodic antigen (CAA) in individuals of different age groups with Schistosoma haematobium infection only in an endemic area of Zimbabwe. An overall positive correlation between S. haematobium egg excretion and CAA levels was demonstrated. The age profile for CAA levels was generally comparable with the age profile of S. haematobium prevalence and intensity of infection. The CAA levels were higher in younger (5-14 years of age) individuals than in older (greater than 14 years of age) ones. Since the sensitivity of the MBAC-EIA in the diagnosis of S. haematobium infection was found to be 97%, CAA levels appear to be a useful indicator of worm burden in an endemic area.

Adolescent↗

PubMed1996

Ultrasonographic assessment of Schistosoma mansoni and S haematobium morbidity in Zimbabwean schoolchildren.

Ultrasound examinations for Schistosoma haematobium - and S. mansoni-related morbidity were done in 174 schoolchildren from a subsistence farming community in southern Zimbabwe. The examinations were done according to the standardized protocol elaborated by the Cairo Working Group (the Cairo classification) and the Managil classification. Forty-six percent of the children had grade I periportal thickening (PPT) on ultrasound according to the Cairo classification, but none had grade II or higher. The significance of grade I PPT in the Cairo classification is questionable, since there were no differences between those without and those with grade I PPT with respect to intensity of S. mansoni infection or liver size. The prevalence of grade I PPT according to the Managil classification was 10%, and no association between the two classifications was seen. In multiple regression analysis, S. mansoni egg output was found to be a significant predictor of liver size, when controlling for height and sex. An interaction between S. haematobium and S. mansoni infection is suggested because the positive relationship between S. mansoni and liver size was seen in the presence but not in the absence of S. haematobium infection.

Adolescent↗

PubMed1996

Age-dependent reduction of schistosome fecundity in Schistosoma haematobium but not Schistosoma mansoni infections in humans.

Understanding the dynamics of schistosome infections is problematic because direct measurements of worm burden are not possible. Hitherto, the relative intensity of infection has been estimated by the number of parasite eggs excreted. Egg excretion is assumed to have a consistent relationship with worm burden with duration of infection. We have tested this assumption in Schistosoma mansoni- and S. haematobium-infected populations by looking at the relationships between a circulating parasite antigen, egg excretion level, host age, and parasite density. The study was carried out in two populations because experimental models suggested that S. haematobium but not S. mansoni suffers immune-mediated reduction of fecundity. The results were consistent with this observation, showing that S. mansoni egg output remains stable irrespective of host age or infection intensity while S. haematobium has a substantially reduced egg production with host age. This information is fundamental to understanding the immunology and epidemiology of human schistosomiasis and thus practical approaches to disease control.

Adolescent↗

PubMed1996

Serum concentration of micronutrients in relation to schistosomiasis and indicators of infection: a cross-sectional study among rural Zimbabwean schoolchildren.

OBJECTIVE: To study the relation between indicators of infection and Schistosoma mansoni and S. haematobium infection, and serum concentrations of zinc, ferritin and retinol. DESIGN: Cross-sectional. SETTING AND SUBJECTS: 313 rural Zimbabwean schoolchildren (144 boys and 169 girls, 11-17 years). VARIABLES: S. mansoni and S. haematobium egg output, concentration of C-reactive protein, neutrophil count, questionnaire data on fever and diarrhoea, and serum concentrations of retinol, ferritin and zinc. RESULTS: Age, elevated CRP, fever and S. mansoni egg output were significant predictors of the concentration of retinol. The regression coefficient for age was positive, and negative for elevated CRP, fever and S. mansoni egg output. As S. mansoni, but not S. haematobium, was of significance, it is unlikely that low retinol level increased susceptibility to infection. The effect of S. mansoni on retinol level was 0.03 mumol/l (95% CI: 0.002-0.06, P = 0.03) for each 100 eggs/g increase in egg output. Neither indicators of infection nor age and sex were predictors of concentration of zinc and log10 concentration of ferritin. CONCLUSION: S. mansoni infection reduced retinol level, when indicators of infection and age were controlled for. High intensities of S. mansoni infection may induce vitamin A deficiency among children with marginal vitamin A status. The study emphasizes the importance of controlling for age and metabolic response to concurrent infections in studies using serum retinol as a measure of vitamin A status.

Adolescent↗

PubMed1995

Bancroftian filariasis in Kwale District of Kenya. III. Quantification of the IgE response in selected individuals from an endemic community.

One hundred and sixty-two individuals from a community in Kwale District, Kenya, endemic for bancroftian filariasis, were selected for a study on the IgE response to filarial antigen (prepared from adult Brugia pahangi). Following clinical and parasitological examination, the individuals were grouped into different categories, based on the presence/absence of microfilaraemia, the presence/absence of acute or chronic (hydrocele or elephantiasis) clinical manifestations, and age. The total and filarial-specific IgE responses were evaluated in all individuals, and the responses in the various categories were compared with each other and with the responses of control groups of individuals from filariasis-free areas. The majority of individuals from the endemic area had highly elevated serum concentrations of total IgE. Overall and within each clinical category, the concentration of total IgE was higher in those individuals from the endemic area who had microfilaraemias than in those that did not. The majority of individuals from the filariasis endemic area also had significantly elevated levels of filarial-specific IgE. In contrast, the concentration of specific IgE was lower in subjects with microfilariae than in those without, irrespective of their clinical status. Only a small proportion of total IgE was filarial-specific, the mean value varying from 0.4% to 9.8%, depending on category. Among the endemic individuals, the mean proportion of total IgE which was filarial-specific was 3.6 times higher in the microfilaria-negative than in the microfilaria-positive, indicating that much of the filarial-induced IgE in microfilaraemic individuals could be non-specific. No clear relationship was observed between the IgE response and the clinical manifestations or age of the endemic individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Bancroftian filariasis in Kwale District of Kenya. II. Humoral immune responses to filarial antigens in selected individuals from an endemic community.

Humoral immune responses to filarial infection were investigated in 162 individuals, covering the full clinical and parasitological spectrum of bancroftian filariasis as seen in an endemic community of Kwale District, Kenya. Sera were tested for specific antifilarial antibodies (total immunoglobulins, IgM, IgGl, IgG4 and IgE) using ELISA. Most individuals showed an immunological response to the filarial antigen (prepared from adult Brugia pahangi). How these responses were related to the clinical manifestations, parasitological status and age was analysed by comparing the mean antibody levels among different categories of endemic individuals, and by comparing these to the levels in control groups from filariasis-free areas. IgM and IgE anti-filarial antibodies were detected with low specificity in unabsorbed sera. A higher specificity, clearly distinguishing the mean antibody levels in the endemic categories from those of control groups, was obtained for total specific immunoglobulins, and for IgE in sera absorbed with protein A. The most specific results were obtained for IgGl and IgG4; clear inter-category differences were observed for these classes. The mean level of specific IgG4 was significantly higher in microfilaraemic groups than in amicrofilaraemic groups, whereas the mean level of specific IgGl was significantly higher in amicrofilaraemic, symptomatic cases than in microfilaraemic, symptomatic cases. In most categories of endemic individuals, and for most antibody isotypes, the mean levels of specific antibodies tended to be higher (although not significantly) in the younger individuals than in the older individuals. Overall, the differences in the filarial antibody responses were more closely related to the presence or absence of microfilariae and to the age of the individuals than to the disease manifestations in this endemic population.

Acute Disease↗

PubMed1994

Experimental infection of Danish Landrace/Yorkshire crossbred pigs with Schistosoma japonicum from the People's Republic of China.

This study was undertaken to assess the suitability of Danish Landrace/Yorkshire (L/Y) crossbred pigs as experimental hosts of a Chinese mainland strain of Schistosoma japonicum. Pigs were exposed to 200, 500 or 1000 cercariae and parasite burdens were determined by perfusion after either 8 or 11 weeks. All pigs became infected with onset of faecal egg excretion 6 to 7 weeks following exposure to cercariae. The pattern of faecal egg excretion differed markedly among the individual animals. Gross hepatic pathological lesions of varying degrees were noted in all of the pigs. Schistosome worm recoveries ranged from 1.5-23.4% of the cercarial exposure dose. Most schistosome eggs recovered from the tissues, expressed as eggs/g tissue, were found in the rectum (91%), caecum (3.1%) and liver (5.1%). The results show that Danish L/Y pigs may serve as appropriate experimental final hosts of the Chinese mainland strain of S. japonicum.

Animals↗

PubMed1994

Morbidity markers for Schistosoma haematobium infection.

A description is given of a field study design, including pretreatment and short and long-term posttreatment measurements, which is conducted as a case-control study among school children in Kaloleni District, Kenya, and Kilosa District, Tanzania, including 500 school children from each endemic setting. The aim of the study is to evaluate eosinophil cationic protein (ECP) in urine as a marker for Schistosoma haematobium morbidity by comparing levels of ECP in urine with S. haematobium egg counts in urine, level of excreted S. haematobium egg antigen in urine, microhaematuria and urinary tract pathology assessed by ultrasonography. Initial results have been promising and are now subject to an extensive evaluation. Strong training components and transfer of technology are included in the project, thus contributing to the strengthening of the research capacity of the collaborating African institutions. Simple non-invasive assays for ECP and excreted S. haematobium egg antigen could provide new tools for evaluation of chemotherapy effects and morbidity in urinary schistosomiasis, helping to understand the dynamic process of posttreatment resolution and reappearance of pathological changes.

Adolescent↗

PubMed1993

Indirect assessment of eosinophiluria in urinary schistosomiasis using eosinophil cationic protein (ECP) and eosinophil protein X (EPX).

The pre- and post-treatment level of eosinophiluria, as measured indirectly by the amount of free or cell bound eosinophil cationic protein (ECP) and eosinophil protein X (EPX) in urine from Schistosoma haematobium-infected Kenyan school children, were measured and compared with intensity of infection (eggs/10 ml of urine), albuminuria and pathological changes as detected by ultrasonography. ECP and EPX were determined by means of specific ELISA methods and levels were determined in both urine supernatants and extracted urine deposits (cells and cell debris). The level of ECP was significantly raised in urine supernatants from infected children compared to controls, whereas high amounts of EPX were found in urine supernatants from infected children as well as from controls. However, the amounts of cell bound ECP and EPX were significantly raised in infected children. In pre-treatment observations significant correlations were demonstrated between egg counts, albuminuria and eosinophiluria as measured by the amount of cell bound ECP and EPX, or ECP in urine supernatants. No such correlations were demonstrated with the amount of EPX in the urine supernatants. Comparable amounts of ECP and EPX could be extracted from the urine deposits from infected children, but due to the high amounts of EPX in urine deposit extracts from controls, extracted ECP gave the best discrimination between infected and non-infected children. While albuminuria disappeared in most children at the 6 week post-treatment follow-up, eosinophiluria persisted in a significant proportion of the treated children indicating continued eosinophil activity in the bladder wall. Detection and quantification of early acute inflammatory reactions using ECP/eosinophils in combination with detection of later stages of bladder pathology using ultrasound may allow for a dynamic evaluation of the pathological process, the morbidity development and post treatment pathological changes in S. haematobium infections.

Adolescent↗

PubMed1993

The antibody response to Dracunculus medinensis in an endemic human population of northern Ghana.

The serum antibody response (total, and isotypes IgG1, IgG4, IgM, IgA and IgE) to Guinea worm infection was examined in humans from a highly endemic area of northern Ghana by ELISA and SDS-PAGE/Western blot techniques using an adult D. medinensis antigen. Sera were obtained early and late in the peak transmission period, from persons with patent and postpatent infections, as well as from persons from the same endemic area who claimed never to have had Guinea worm infection. To observe for potential cross-reactions in the tests, sera were also obtained from areas with no transmission of Guinea worm from patients with hookworm, O. volvulus and W. bancrofti infections, and from non-infected controls. Sera from persons living in the Guinea worm endemic area reacted extensively with Guinea worm antigen in both tests, and large numbers of bands were produced in the Western blots (up to 35 identified for some sera). For most antibody isotypes, the ELISA absorbance values obtained with sera from the same individuals varied between the two transmission seasons, with the highest titres present towards the end of the peak transmission period. The mean antibody titres for persons in the patent and postpatent infection categories were not significantly different when sera were obtained at the same season of the year. Persons from the endemic area, who claimed never to experience patent infections, also had antibodies to Guinea worm, although at significantly lower mean levels than for the patent and postpatent categories. The highest specificity in the ELISA and the most homogenous Western blots were obtained when detecting for antibodies of the IgG4 isotype.

Adolescent↗

PubMed1993

The antibody response in serum, intestinal wall and intestinal lumen of NMRI mice infected with Echinostoma caproni.

Groups of mice (NMRI) were infected with 0, 6 and 25 metacercariae of the intestinal trematode Echinostoma caproni. An enzyme linked immunosorbent assay (ELISA) was developed for measuring the specific IgM, IgG and IgA antibody responses in serum, small intestinal tissue and small intestinal lumen of the mice, by using a crude adult E. caproni antigen. In infected mice, significant levels of IgM were measured in the sera from day 14 after infection and of IgG and IgA from day 28 after infection. Early in the infection, the mean level of serum IgM was higher in 6-worm infections than in 25-worm infections. Late in the infection, higher mean levels of IgA were reached in the serum of mice with high than in those with low dose infections. The onset of appearance of antibodies in the tissue of the small intestine reflected the picture seen in the serum. For IgM, and to a lesser degree for IgG, the highest mean antibody levels appeared in the posterior sections of the small intestinal wall, where also the parasites were located. The mean level of IgA, however, was uniform throughout the length of the small intestinal tissue. High levels of specific IgA were detected in the lumen of the small intestine on day 28 after infection, especially in the anterior sections, where only few parasites were located. No specific IgM or IgG could be detected in the intestinal lumen on this day. The results are related to the intestinal location and the pattern of expulsion of E. caproni in the mouse host.

Animals↗

PubMed1992

Toxoplasma pericarditis mimicking systemic lupus erythematosus. Diagnostic and treatment difficulties in one patient.

A life-threatening T. gondii pericarditis developed in a patient with symptoms corresponding to systemic lupus erythematosus (SLE) with high concentrations of antinuclear antibodies and lymphadenopathy. The diagnosis would have been SLE-associated serositis, had not pericardial fluid been inoculated into mice, because pericarditis is frequently seen in SLE and false positive toxoplasma seroreactions may occur in ANA positive patients. High IgG T. gondii antibodies without increased IgM antibodies indicated reactivation rather than primary infection. Prolonged high-dose treatment with pyrimethamine-sulphadiazine was needed. Interestingly, the patient's SLE symptoms, including high ANA antibodies, declined to an unexpected remission after treatment for toxoplasmosis. This may not be mere coincidence, but may point to a causative role of toxoplasmosis in some cases of SLE.

Animals↗

PubMed1990

[Human toxoplasmosis].

Toxoplasmosis infection is transmitted from cat faeces or insufficiently heated meat from e.g. pigs, sheep and goats. If pregnant women are infected with Toxoplasma gondii, there is a risk of infection of the foetus with the possibility of development of congenital toxoplasmosis and, in patients with AIDS, a latent infection may be activated with subsequent fatal encephalitis. Human infections with T. gondii are common but are frequently asymptomatic. The prevalence of T. gondii infection in the Danish population is not known exactly but preliminary investigations among pregnant women have revealed a prevalence of approximately 33% and the annual incidence is calculated to 0.5%. Legal abortion should be offered to pregnant women in whom toxoplasmosis is diagnosed on account of the risk of foetal damage. If legal abortion is not accepted or is not possible, treatment with spiramycin should be instituted. In immunosuppressed individuals with evidence of activation of latent T. gondii infection and children with congenital toxoplasmosis, treatment with combined pyrimethamine and sulphadiazine should be administered. Information about the routes of infection is important, particularly for sero-negative pregnant women as the routes of infection are limited so that it is reasonably easy to avoid infection.

Denmark↗