The population biology and epidemiology of schistosome and geohelminth infections among schoolchildren in Tanzania

A study of helminth infections was undertaken among 3244 schoolchildren from 28 schools in Morogoro Rural District, Tanzania. Schistosoma haematobium was the most common infection, followed by hookworms, Ascaris lumbricoides, S. mansoni, and Trichuris trichiura. Infection prevalence of each species varied among schools and age groups, but not between sexes. There was no relationship between the prevalences of different infections among schools, except for a strong negative correlation between the prevalence of hookworm and S. mansoni infections. Within each age group, there was little excess overlap in the distribution of each infection; thus the number of multiple infections was low whereas the number of individuals harbouring at least one infection was relatively high. More children than expected carried infections of A. lumbricoides and S. mansoni, and the clustering effect increased with age. Only 2 schools had high overall infection prevalences of both geohelminths and schistosomes. Logistic regression analysis of morbidity and parasitological data indicated that individuals with multiple species infections were not at increased risk of morbidity (on a multiplicative scale) compared to individuals with single species infections. This was attributed in part to the low egg counts observed for each parasite species. The results implied little interaction between schistosome and geohelminth infections in the region, both in parasitological terms and in the context of their combined effects on health. Implications for the feasibility and benefits of combined control of geohelminths and schistosomes are discussed.

The use of morbidity questionnaires to identify communities with high prevalences of schistosome or geohelminth infections in Tanzania

Parasitic infections were investigated in Morogoro Rural District, Tanzania, between October 1992 and June 1993. A total of 4589 schoolchildren (aged 7-17 years) from 30 primary schools was screened for infection with Ascaris lumbricoides, Trichuris trichiura, hookworms (3456 children only), Schistosoma mansoni and S. haematobium. The children were also asked about their recent experiences of the following: diarrhoea, abdominal pain, blood in stool, perception of suffering from schistosomiasis, and worm infection and examined for spleen and liver enlargement. Among schools, there were correlations between the prevalence of S. mansoni infection and bloody stools, spleen enlargement and liver enlargement, and between S. haematobium infection and the presence of blood in urine. To exclude ecological explanations for the correlations, logistic regression was used to estimate the adjusted odds ratio (OR) for each infection and each sign or symptom. No sign or symptom was significantly associated with any geohelminth infection. Reported blood in stool was significantly associated with S. mansoni infection (OR = 1.62, P = 0.045). Reported blood in urine was significantly associated with S. haematobium infection (OR = 7.71, P < 0.001), as was reported blood in stool (OR = 11.52, P < 0.001), indicating that presence of blood in either form of excreta was related to the local term for schistosomiasis. These results support the possibility of using reported blood in stool as a means of rapid assessment for identifying communities with a high prevalence of S. mansoni infection.

Incidence of Plasmodium falciparum infection in infants in relation to exposure to sporozoite-infected anophelines

The relationship of the incidence of Plasmodium falciparum infection to entomologic inoculation rates (EIRs) was studied in 163 children less than one year of age in a Tanzanian village to determine likely effects of transmission-reducing interventions on infection incidence. A total of 66,727 Anopheles gambiae s.l. and 17,620 An. funestus mosquitoes were caught in 1,056 light trap collections from 139 houses over a period of more than two years. Time period-specific human biting rates were estimated for 11 village neighborhoods. Sporozoites were detected by ELISA in 4.4% of the An. funestus and 2.5% of the An. gambiae s.l. Eight hundred seventeen pairs of blood slides with approximately two-week intervals between slides were used to estimate incidence of parasitemia by fitting reversible catalytic models to parasite positivity data. Estimated EIRs during the four weeks preceding each intersurvey interval averaged 1.6 (SD = 2.1) per adult per night. Parasites were present at the end of 31% of the 443 intervals that commenced with a parasite-negative slide. Attack rates were comparable with those in western Kenya, and the proportion of bites resulting in human infections was strongly dependent on mosquito density. Incidence of infection increased with the EIR up to approximately one bite from a sporozoite-carrying mosquito per adult per night. However, higher levels of transmission observed locally in the wet season did not result in a correspondingly higher incidence. These data suggest that transmission-reducing measures cannot be expected to reduce incidence of infection at the highest levels of EIR.

Two-photon near- and far-field fluorescence microscopy with continuous-wave excitation

We report on scanning far- and near-field two-photon microscopy of cell nuclei stained with DAPI and bisbenzimidazole Hoechst 33342 (BBI-342) with the 647-nm laser line of a cw ArKr mixed-gas laser. Two-photon-excited fluorescence images are obtained for 50-200 mW of average power at the sample. A nearly quadratic dependence of fluorescence intensity on laser power confirmed the two-photon effect. The nonlinearity was further supported by evidence of three-dimensional sectioning in a scanning far-field microscope. We find that the cw two-photon irradiation sufficient for imaging within typically 5 s does not significantly impair cell cycling of BBI-342-labeled live cells. Finally, high-resolution imaging in scanning near-field microscopy with good contrast is demonstrated.

Effects of body composition and fat distribution on ventilatory function in adults

Clinically, gross obesity is associated with disturbances of ventilatory function, but less severe obesity is not generally thought to have a significant effect on ventilatory function. The purpose of this report was to examine cross-sectional data to determine the effects of body composition and fat distribution on ventilatory function in 1235 adults (621 men and 614 women). Forced vital capacity (FVC) was used as a measure of ventilatory function and was adjusted for age, height, smoking, and bronchial symptoms in separate models for men and women. Body fat and fat-free mass were estimated from skinfold-thickness measurements. Adjusted FVC was not significantly associated with body mass or body mass index, but was negatively associated with percentage body fat in men (P = 0.0003) and women (P = 0.043) and positively associated with fat-free mass in men (P = 0.018) and women (P = 0.0001). Handgrip strength was positively associated with adjusted FVC in both sexes (P < 0.02), suggesting that the effect of fat-free mass may be mediated by muscular strength. Adjusted FVC was negatively associated with subscapular-skinfold thickness in both sexes (P < 0.0003) and with waist circumference (P = 0.01) and waist-to-hip ratio (P = 0.03) in men. Previous reports that considered only body mass index or body mass failed to distinguish the opposing effects of fat-free mass and fat mass on FVC.

Experiences with a multi-sectorial operation research programme for control of schistosomiasis in a Tanzanian district

A well validated questionnaire-based approach allowed identification of six villages endemic for urinary schistosomiasis (infection prevalence > 25%) in a rural Tanzanian district. An interdisciplinary team launched an operational research programme with the aim of establish noting a sustainable approach to reducing schistosomiasis morbidity. The programme comprised of three different strategies: chemotherapy, promotion of Ventilated Improved Pit (VIP) latrines and health education. After five consecutive years of intervention, the overall organisation and management, inputs, processes, outputs, outcomes and impact of each strategy were evaluated. Different key informants and groups of the community were interviewed, to record their programme evaluation. Infection prevalence among school children decreased from 48.1% to 18.7% for Schistosoma haematobium and from 28.0% to 9.0% for S. mansoni. 54 VIP latrines were constructed at popular locations of which 50 were still functioning and in use after five years. Children's awareness about schistosomiasis did not differ between schools within and outside the study area. Community-based evaluation closely followed the quantitative results, with chemotherapy rated as the most successful strategy.

Associations among multiple geohelminth species infections in schoolchildren from Pemba Island

In order to estimate the potential benefits of interventions against multiple geohelminth species in endemic areas, an improved understanding of the population biology of multiple infections is required. This paper presents a detailed analysis of the associations among Ascaris lumbricoides, Trichuris trichiura and hookworm infections in 1539 schoolchildren on Pemba Island, Tanzania, where 58% of the sampled children carried infections of all 3 parasites at the time of the study. Infection intensities of different species were positively correlated, and individuals with single-species infections had generally lower species-specific egg counts than individuals with multiple-species infections. There was no age- or sex-related clustering of infections. A weak clustering of intense infections among individuals with multiple-species infections was observed, which became more pronounced as the threshold defining an intense infection increased for each species. The results suggest that individuals with multiple species infections are likely to be at highest risk of geohelminth-related morbidity, not only because of the number of infections they harbour, but also because they generally carry heavier infections of each species.

Study of the heart rate and energy expenditure of ponies during transport

The energy expenditure and heart rate of five Shetland ponies were measured during transport and compared with the values recorded while they were at rest and walking. Secondary aims of the study were to investigate whether there was any correlation between heart rate and energy expenditure and whether different orientations affected the values to different degrees. The measurements were recorded at one-minute intervals while the ponies were at rest, walking and being transported in four different orientations, on journeys lasting 30 minutes. There were significant increases (P < 0.001) in both heart rate and energy expenditure during transport which were similar to those associated with walking, and there was a strong correlation between the two measurements. There was no conclusive evidence that orientation affected the measurements, but it appeared that rear facing transport might have had the least effect.

Photodynamic therapy of the ciliary body with tin ethyl etiopurpurin and tin octaethyl benzochlorin in pigmented rabbits

BACKGROUND AND OBJECTIVES

The authors used a pigmented rabbit model to investigate two photosensitizers, tin ethyl etiopurpurin (SnET2) and tin octaethyl benzochlorin (BNZ 203), to determine their potential for creating ciliary body injuries during photodynamic therapy (PDT).

MATERIALS AND METHODS

The biodistribution of SnET2 (n = 10) and BNZ 203 (n = 9) was studied by fluorescence microscopy using a low light detection system, based on charged-coupled device photography, with digital image processing at 1 and 24 hours after injection. PDT with SnET2 (n = 8; 664 +/- 7-nm light; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) and BNZ 203 (n = 6; 689 nm; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) was performed at 24 hours post-injection. The control subjects for SnET2 (n = 5) and BNZ 203 (n = 3) were given a maximal light dose (100 J/cm2).

RESULTS

Both photosensitizers demonstrated an intravascular distribution at 1 hour that shifted to a ciliary body distribution at 24 hours (SnET2 much greater than BNZ 203). In addition, the SnET2 demonstrated suborgan localization to the nonpigmented ciliary body epithelium. Both photosensitizing agents were able to produce selective injury to the rabbit ciliary body (SnET2 much greater than BNZ 203), with evidence of a small component of thermal damage (SnET2 greater than BNZ 203).

CONCLUSIONS

PDT with SnET2 or BNZ 203 can produce selective injury to the pigmented rabbit ciliary body. The nonpigmented ciliary body epithelium exhibits selective retention of SnET2. This finding warrants further investigation.

How the brain learns to see objects and faces in an impoverished context

A degraded image of an object or face, which appears meaningless when seen for the first time, is easily recognizable after viewing an undegraded version of the same image. The neural mechanisms by which this form of rapid perceptual learning facilitates perception are not well understood. Psychological theory suggests the involvement of systems for processing stimulus attributes, spatial attention and feature binding, as well as those involved in visual imagery. Here we investigate where and how this rapid perceptual learning is expressed in the human brain by using functional neuroimaging to measure brain activity during exposure to degraded images before and after exposure to the corresponding undegraded versions. Perceptual learning of faces or objects enhanced the activity of inferior temporal regions known to be involved in face and object recognition respectively. In addition, both face and object learning led to increased activity in medial and lateral parietal regions that have been implicated in attention and visual imagery. We observed a strong coupling between the temporal face area and the medial parietal cortex when, and only when, faces were perceived. This suggests that perceptual learning involves direct interactions between areas involved in face recognition and those involved in spatial attention, feature binding and memory recall.

Cyclosporin A/alpha interferon-induced autologous graft-versus-host disease following peripheral blood stem cell transplant for chronic myeloid leukaemia: a clinico-pathological study

Autologous GVHD was induced using CsA and alpha-IFN in a patient undergoing autologous PBSCT for accelerated phase CML. We demonstrated that the autologous mixed lymphocyte reactions were extremely sensitive and specific for the detection of the GVHD when compared to skin biopsy. The resultant autologous GVHD was associated with an in vitro GVL effect, suggesting a potential clinical benefit of this therapeutic manoeuvre. The post-PBSCT period was associated with an improvement in normal haemopoiesis and reduction in the proportion of blood cells expressing the Philadelphia chromosome.

Perceptual learning: insight in sight

The Hebbian synapse and Hebb learning rule are familiar to those working on biological and machine learning. But Hebb's insights from over fifty years ago carry many other lessons in learning and may contribute to a more parsimonious taxonomy of the mechanisms involved.

Molecular epidemiology and significance of a cluster of cases of CMV infection occurring on a special care baby unit

Sequencing of the amino-terminal region of the glycoprotein H gene was used to investigate the possibility of a common source for cytomegalovirus (CMV) infection occurring in five premature babies. All but two of the strains were different, indicating that this cluster of infection occurring on the special care baby unit was unlikely to be epidemiologically linked.

The morbidity attributable to Schistosoma japonicum infection in 3 villages in Dongting Lake region, Hunan province, PR China

In common with other helminth infections, symptoms associated with Schistosoma japonicum infection have a low specificity, and many infections are asymptomatic. The presence of the parasite in a sick individual from an endemic area does not mean that S. japonicum is the aetiological agent. However, estimates of the proportion of all symptomatic episodes in a community attributable to S. japonicum infection can be used to determine its public health impact. Using parasitological and morbidity survey data from 3 villages in China, the fractions of diarrhoea, bloody stool, and abdominal pain episodes that were attributable to S. japonicum infection were estimated. The association between hepatomegaly and S. japonicum infection was also assessed. For all morbidity indicators, it was found that individuals with higher infection intensities were at greater risk of morbidity. The highest risk indicator of morbidity associated with S. japonicum infection was bloody stools. Logistic regression revealed that factors related to village and sex were important confounders of the relation between infection and the risk of morbidity. The fraction of the population in each village estimated to be suffering morbidity attributable to S. japonicum infection was low, due to the low prevalence of infection. However, the results suggest that some sick individuals may have been diagnosed as false negatives for S. japonicum infection.

Clinical aspects of nurse anesthesia practice. Sedation and monitored anesthesia care

Safe monitoring of patients receiving sedation mandates that all care givers recognize the potential physiologic trespass of sedatives, hypnotics, and opioid-like drugs on cerebral or respiratory systems. They must be ready to recognize this affront immediately, have necessary resuscitative equipment available, possess prerequisite skills to intervene in adverse changes, and know when to seek additional help. The long history of CRNA practice has helped to define nursing roles in this important form of perioperative care.

Helminth infections, morbidity indicators and schistosomiasis treatment history in three villages, Dongting Lake region, PR China

In order to estimate the public health impact of helminth infections, and to provide baseline data for interventions, parasitological and morbidity surveys were conducted among inhabitants of three villages in Dongting Lake region, Hunan Province, China. Ascaris lumbricoides was found to be the most common helminth infection, followed by Trichuris trichiura and Schistosoma japonicum. Left liver enlargement was the most common indicator of morbidity. Observed numbers of multiple species infections closely correlated with expected figures generated from a simple probabilistic model. Heterogeneity was observed in age and sex-standardized infection and morbidity prevalences among the villages and occupations. Males had higher levels of infection, were more likely to suffer morbidity, and were more likely to have been treated for schistosomiasis than women. The prevalence of each morbidity indicator was positively correlated with the number of times of treatment for schistosomiasis, and negatively correlated with number of years since last treatment. The results imply that treatment history for S. japonicum infection may be a good indicator of current morbidity risk.

Development of public policy and physical activity initiatives internationally

Epidemiological, pathological, clinical, and experimental studies over the past 40 years convincingly show that physical inactivity and low physical fitness contribute substantially to the major chronic diseases prevalent in industrialised societies. Several industrialised countries around the world report increases in physical activity participation among adults in recent years, but the prevalence of inactivity remains high. These increases in voluntary exercise are at least partially offset by decreasing daily energy demands due to increased mechanisation at home, at work and during leisure-time. In developing countries, physical inactivity is becoming a prevalent lifestyle due to rapid social and economic changes. Clinical interventions and mass appeals to be more physically active are limited in effectiveness against the background of increasingly sedentary lifestyles. Exercise scientists and public health officials need to turn attention to public policy and legislative initiatives to restructure physical and social environments to encourage more physical activity and discourage sedentary habits.

Asthma, health behaviors, social adjustment, and psychosomatic symptoms in adolescence

The association of health behaviour, indicators of social adjustment, and psychosomatic symptoms with diagnosed asthma was assessed in a community-based sample of 4550 adolescents in South Western Sydney, Australia. The results of this survey found an asthma prevalence among 11-15-year-olds of 17.5%, being consistent with previous studies. Tobacco use and alcohol consumption were higher among asthmatic compared with nonasthmatic adolescents. Asthmatics reported feeling lonely more often, having a number of negative social perceptions and feelings, and having more frequent psychosomatic symptoms. The findings of the study suggest that adolescents with asthma represent an important vulnerable group of school children. Asthma education may need a greater life-style change focus, besides asthma self-management training.

Estimating the number of multiple-species geohelminth infections in human communities

Infections with Ascaris lumbricoides, Trichuris trichiura and the hookworm species are often found in the same communities and individuals. Hosts infected by more than one species are potentially at risk of morbidity associated with each infection. This paper describes the use of a probabilistic model to predict the prevalence of multiple-species infections in communities for which only overall prevalence data exist. The model is tested against field data, using log-linear analysis, and is found to be more effective at estimating the numbers of multiple infections involving hookworms than those involving only A. lumbicoides and T. trichiura. This latter combination of infections is found, in half the communities examined, to be more common than expected by chance. An age-stratified analysis reveals that the degree of interaction between these two infections does not alter significantly with age in the child age classes of a Malaysian population.

The development of an age structured model for schistosomiasis transmission dynamics and control and its validation for Schistosoma mansoni

Mathematical models are potentially useful tools to aid in the design of control programmes for parasitic diseases. In this paper, a fully age structured epidemiological model of human schistosomiasis is developed and parameterized, and used to predict trends in infection prevalence, intensity and prevalence of heavy infections over age and time during several rounds of mass and age targeted treatment. The model is validated against data from a Schistosoma mansoni control programme in Kenya.

BCL-2 expression by leukaemic blasts in a SCID mouse model of biphenotypic leukaemia associated with the t(4;11)(q21;q23) translocation

Acute leukaemia of infancy is associated with abnormalities at chromosome band 11q23, and has a poor prognosis. The gene involved. Mixed Lineage Leukaemia (MLL), has been identified and has the characteristics of a transcription factor. The BCL-2 gene responsible for blocking of programmed cell death is highly expressed in a number of haematological malignancies, both with and without the t(14;18) translocation. Those without the translocation include acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML) and chronic lymphocytic leukaemia (CLL). In these diseases the BCL-2 protein is implicated in drug resistance to apoptosis-inducing chemotherapeutic agents. High BCL-2 expression is also associated with autonomous growth of leukaemic blasts in culture and predicts a poor prognosis. The SEM cell line, established using blood lymphoblasts from a 5-year-old girl in first relapse with t(4;11) ALL, expresses lymphoid (CD19) and myeloid (CD13) cell surface markers. In cell culture, a subpopulation of cells (< 30%) express the BCL-2 protein. A reproducible model of true biphenotypic leukaemia in the SCID mouse has been established using the SEM-K2 cell line (a subclone of the SEM cell line). Between 5 and 50 million cells injected intravenously (i.v.) produce complete replacement of the murine bone marrow by day 30, associated with blood lymphoblastosis and infiltration of the spleen. No tumour masses were seen. Fluorescence in situ hybridization (FISH) analysis of the cell line and blood from the SCID-human (SCID-hu) chimaera has confirmed the presence of the t(4;11). Reverse transcriptional-polymerase chain reaction (RT-PCR) reveals that the breakpoint lies between exons 7 and 8 of the MLL-1 gene on chromosome 11 (the main breakpoint region). A further translocation, t(7;13), has been identified. Fluorescent antibody cell sorter (FACS) analysis of tumour material recovered from the SCID-hu model confirms expression of CD19 and CD13 identical to that of the cell line. In addition, BCL-2 expression in SCID-hu marrow is now seen in the majority of tumour cells. BCL-2 expression appears to confer a survival advantage to the blast cells in vivo. This reproducible model of biphenotypic leukaemia suggests that BCL-2 expression may play a role in leukaemogenesis. The model is suitable for the investigation of gene-targeted therapy, including antisense oligonucleotides, directed towards the MLL and BCL-2 genes.