High incidence of asymptomatic malara infections in a birth cohort of children less than one year of age in Ghana, detected by multicopy gene polymerase chain reaction

The incidence of Plasmodium falciparum infection has been followed in a birth cohort of 71 infants in southern Ghana, an area of perennial malaria transmission. Parasite DNA detection established the presence of a high rate of infection in newborns (13.6%), a low level of infection from two to 26 weeks (1.5-9.7%) and a steadily increasing parasite rate from 26 weeks of age. The median age to first infection was 42 weeks. Five cases of fever (temperature > or = 37.5 degrees C) and parasite density greater than 1,000 parasites/microl of blood, all in children more than 18 weeks of age, were considered possible cases of clinical malaria. The risk of infection was almost three times higher in the wet season than in the dry season and increased significantly from the age of 18 weeks. The level of malaria-specific IgG at birth was positively correlated with risk of infection in children 6-12 months of age, indicating that maternally derived anti-malarial IgG is correlated with exposure to malaria infection. There was no association between malaria-specific IgG at birth and risk of infection in children 0-6 months of age. However, infants do appear to possess mechanisms to limit parasite growth and a role for maternal antibody cannot be ruled out.

The potential role of peripheral health workers and community key informants in the rapid assessment of community burden of disease: the example of lymphatic filariasis

Data for planning disease control programs in most developing countries is often not available because they are usually expensive to gather. This study explored the potential use of peripheral health staff and community key informants in gathering community-level data about lymphatic filariasis. Agreement between findings of health workers and those of physicians was very high (kappa 0.66-0.87) for the clinical conditions examined. The prevalence of hydrocele was found to be a good predictor of communities at risk of filariasis. Community key informants provided very useful qualitative and quantitative data on the prevalence of clinical filariasis. The need to use nontraditional health professionals in gathering data for planing control programs is discussed.

Short-term side effects of stimulant medication are increased in preschool children with attention-deficit/hyperactivity disorder: a double-blind placebo-controlled study

Preschool children with attention-deficit/hyperactivity disorder (ADHD) (27 boys, 5 girls, mean age 4 years 10 months) participated in a double-blind placebo-controlled crossover drug study to assess the side effects of methylphenidate. Children received twice daily, for at least 1 week each, placebo, 0.3 mg/kg methylphenidate, and 0.5 mg/kg methylphenidate. Side effects were monitored by a parent rating scale designed for medication studies. In general, methylphenidate was tolerated relatively well, with no children withdrawing because of adverse effects. Of 17 childhood behaviors usually associated with side effects, 8 behaviors showed significant changes, generally at the higher dose of methylphenidate. Interestingly, 3 of the side effects were associated with improved behavior. The number of side effects appeared higher than what is usually reported in a population of school-age children, but few parents reported them as being severe. Severe side effects were reported in less than 10% of the sample, with approximately as many reports of severe effects on placebo as on low and high doses of the medication. The results indicate that methylphenidate has a relatively low toxicity in preschool children (over the first 7-10 days), that some behavioral changes that might be viewed as side effects of methylphenidate are actually normal behaviors or ADHD behaviors in preschool children (e.g., sociability), that these "side-effect" behaviors are more common in preschool than school-age children, that some "side effects" of methylphenidate are associated with improvements in behavior, and that preschool and school-age children may have different side effects of methylphenidate (e.g., mood changes and anxiety).

Ketoacidosis occurring in newly diagnosed and established diabetic children

A 6-y retrospective case note review was performed to determine the causes of ketoacidosis. 135 patients and 463 diabetic years were involved. Fifty-two ketoacidosis episodes occurred: 19 episodes in new patients and 33 episodes in 19 patients with established diabetes. 27% of newly diagnosed patients presented in ketoacidosis. They were similar in terms of age, sex and proportion living in single parent families to those presenting without ketoacidosis. The 33 ketoacidosis episodes occurring in established patients included 12 episodes in 3 children who were transferred to our care because of uncontrolled diabetes. Insulin omission was the cause of ketoacidosis in 9/19 (47%) patients, and was suspected in a further 5/19 (26%). Family and school problems were common and 14/19 patients came from single parent families. Established patients aged > or = 11 y were predominantly female (10F, 2M), whereas patients aged < or = 10 y were predominantly male (6M, 1F). 7 patients with multiple ketoacidosis episodes were all > or = 11 y and 6 were female. Families with > or = 2 diabetic children appeared vulnerable, 4 cases coming from 3/7 such families.

Clinical predictors of malaria in Gambian children with fever or a history of fever

Diagnosis of malaria in children is difficult without laboratory support because the symptoms and signs of malaria overlap with those of other febrile illnesses such as pneumonia. Nevertheless, in many parts of Africa diagnosis of malaria must be made without laboratory investigation. Therefore, a scoring system has been developed to assist peripheral health care workers in making this diagnosis. Four hundred and seven Gambian children aged 6 months to 9 years who presented to a rural clinic with fever or a recent history of fever were investigated. A diagnosis of malaria was made in 159 children who had a fever of 38 degrees C or more and malaria parasitaemia of 5000 parasites/microL or more. Symptoms and signs in children with malaria were compared with those in children with other febrile illnesses to identify features which predicted malaria. Symptoms and signs were incorporated into various logistic regression models to test which were best independent predictors of malaria and these regression models were used to construct simple scoring systems which predicted malaria. A nine terms model predicted clinical malaria with a sensitivity of 89% and a specificity of 61%, values comparable to those obtained by an experienced paediatrician without laboratory support. The ability of peripheral health care workers to diagnose malaria using this approach is now being investigated in a prospective study.

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor alpha, retinoic acid, vitamin D3, and the transforming growth factor beta families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

The Gambian National Impregnated Bednet Programme: costs, consequences and net cost-effectiveness

Clinical trials have indicated that treating mosquito nets with insecticide could be a potentially cost-effective method of preventing malaria. As malaria is one of the most common causes of death in children under five in developing countries, there has been substantial interest in whether such findings can be replicated for a country's control programme in practice. The cost-effectiveness of the Gambian National Insecticide-impregnated Bednet Programme (NIBP), from the viewpoint of providers (government and non-governmental agencies) and the community, has been calculated. Information was collected from existing records, interviews with NIBP personnel, observation and household surveys. Information is provided on the resource use consequences of the NIBP in terms of reduced expenditure on anti-malaria preventive measures, treatment in government health services, household financed treatment and "charity" (burial, funeral and mourning activities), as well as cash income lost as a result of child death. The annual implementation cost of the NIBP was D757,875 (US$91,864), of which 86% was recurrent cost. The estimated number of death averted was 40.56. The net implementation cost-effectiveness ratio per death averted and discounted life years gained were D3884 (US$471) and D260 (US$31.5), respectively. Adding the cost of all mosquito nets would increase the cost-effectiveness ratios by over five times, which is an important consideration for countries with a lower coverage of mosquito nets per capita. It is concluded that insecticide-impregnated mosquito nets are one of the more efficient ways of reducing deaths in children under 10 years in rural Gambia.

An efficacy trial of the malaria vaccine SPf66 in Gambian infants--second year of follow-up

In 1994, 630 Gambian infants were immunized with three doses of the synthetic polypeptide malaria vaccine SPf66 or with a control vaccine. No significant protection against first or total attacks of malaria was observed among the children who received SPf66. However, the period of follow-up was short. Thus, 532 children were followed for a second malaria transmission season during which 291 episodes of malaria were detected. Protective efficacies of SPf66 against first attacks of malaria and against all attacks of malaria were 8% [95% CI-20%, 30%] and 2% [95% CI-26% 24%] respectively. SPf66 did not provide any significant degree of protection to Gambian infants during a second year of follow-up.

Prevalence of hydrocele as a rapid diagnostic index for lymphatic filariasis

The real burden of lymphatic filariasis in most endemic areas remains unknown even thought it is a major public health problem in many tropical countries, particularly in sub-saharan African. The nocturnal periodicity of the parasite requires parasitological examinations to be done at night. The aim of this study was to develop and validate rapid epidemiological assessment tools for the community diagnosis of lymphatic filariasis, that may be used in the future to determine the distribution of the disease and identify high risk communities in Ghana. Twenty communities with varying endemicity of filariasis were sampled from 3 endemic districts. Community members were selected for the study using a modified Expanded Programme for Immunization (EPI) cluster sampling technique. The prevalence of hydrocele was high (range 4.5-40.75%, mean = 17.78%) and the community prevalence of microfilaraemia correlated well with that of hydrocele (r = 0.84). The findings suggest that it is possible to obtain reliable and valid estimates of the community burden of lymphatic filariasis using the prevalence of hydrocele as a diagnostic index.

Skill acquisition in sport: some applications of an evolving practice ecology

This paper builds on recent theoretical concerns regarding traditional conceptualizations of the skill acquisition process. The implications for the process of practice in sport contexts are explored with reference to the information-processing approach to motor behaviour and the newer ecological paradigm. Issues are raised with current principles of practice based on traditional theoretical ideas. A practice strategy that gives greater weight to the guided exploration of the practice workspace jointly defined by the properties of the individual's subsystems, the specific task and the environment is advocated. Such a constraints-led perspective supersedes previous distinctions between rudimentary and voluntary skills. Sports scientists, coaches, teachers and movement rehabilitation therapists are invited to review current practices in the light of recent theoretical advances from the ecological perspective.

Plasmodium vivax: a cause of malnutrition in young children

We studied the aetiology of malnutrition in a cohort of 1511 children < 10 years old in Espiritu Santo, Vanuatu. Malnutrition was categorized using standard anthropometric criteria as: underweight [weight-for-age (WA) Z score < -2], wasting [weight-for-height (WH) Z < -2], or stunting [height-for-age (HA) Z < -2]. On multiple logistic regression analysis, the only factors significantly associated with wasting were age < 5 years [OR (95% CI) 1.8 (1.2-2.9), p = 0.01] and having suffered one or more episodes of clinical P. vivax malaria in the 6 months preceding nutritional assessment [OR 2.4 (1.3-4.4), p = 0.006]. The incidence of P. vivax infection was significantly higher during the 6 months preceding assessment in underweight vs. non-underweight children [incidence rate ratio (IRR) 2.6 (1.5-4.4), p < or = 0.0001). These groups had similar incidences of clinical P. falciparum infection during the same period [IRR 1.1 (0.57-2.1) p = 0.8] and of either species during the 6 months following assessment [IRR P. vivax 1.3 (0.9-2.0) p = 0.2; IRR P. falciparum 1.3 (0.9-1.9) p = 0.2]. In these children, P. vivax malaria was a major predictor of acute malnutrition; P. falciparum was not. Wasting neither predisposed to nor protected against malaria of either species. Although P. vivax malaria is generally regarded as benign, it may produce considerable global mortality through malnutrition.

Follow-up of Gambian children recruited to a pilot safety and immunogenicity study of the malaria vaccine SPf66

A pilot safety and immunogenicity trial of the malaria vaccine SPf66 was undertaken in The Gambia in 1993. One hundred and fifty infants aged 6-11 months were immunized with either 0.5 mg or 1.0 mg of SPf66 produced either in Colombia or in the USA or with a control vaccine. Children who received SPf66 experienced more clinical attacks of malaria than did children in the control group during the first period of surveillance and the difference in incidence between children who had received high dose Colombian vaccine and the control children was statistically significant at the 5% level. During the 1995 malaria transmission season, 127 children from the original cohort of 150 were observed. During 18 weeks of intensive surveillance, the incidence of clinical malaria was again higher among children who had received SPf66 than among children who had received inactivated polio vaccine (6.23 vs 4.89 clinical attacks per 1000 days at risk), the effect being most marked among children who were in the high dose groups, but differences between groups were now no longer statistically significant.

The Gambian National Impregnated Bed Net Programme: evaluation of effectiveness by means of case-control studies

Two case-control studies, one on mortality and the other on malaria morbidity, were carried out in order to evaluate the impact of the Gambian National Insecticide Bed Net Programme during the second year of intervention and to explore the feasibility of such a study for the evaluation of programme effectiveness. For the mortality study, children 1-9 years old who died during the 1993 rainy season were matched by age and sex with 2 healthy controls from the same village. For the morbidity study, children 1-9 years old attending Fatoto or Jahalia Health Centres in The Gambia and who had fever and parasitaemia > or = 5000/microL were matched by age with a child attending the health centres without fever or parasitaemia. An additional healthy control was recruited from the case's village. No impact of insecticide-treated bed nets on mortality was detected and this was in keeping with the results obtained by prospective surveillance. A protective effect of insecticide-treated nets on malaria morbidity was detected when cases were compared with controls recruited at the health centres. However, this disappeared when cases were compared with controls recruited from the cases' villages. The mortality case-control study suggested that reducing the time between onset of disease and treatment may have an important impact on childhood mortality. In order to calculate programme cost-effectiveness, important for informed resource allocations to be made by health managers, it is essential to obtain evidence of effectiveness. This can be done by means of case-control studies, which are easier to carry out and require fewer resources than prospective surveillance. Nevertheless, it is necessary to be conscious of their pitfalls, particularly of the bias involved in the choice of cases and controls. The measurement of insecticide on the nets of the cases or controls is essential for such studies.

Effects of methylphenidate on preschool children with ADHD: cognitive and behavioral functions

OBJECTIVE

To report on implications for methylphenidate treatment of this very young age group and the need to examine factors related to achieving compliance.

METHOD

Thirty-one children with attention-deficit hyperactivity disorder (ADHD), aged 4 to 6 years, participated in a double-blind, placebo-controlled study using placebo, 0.3 mg/kg, and 0.5 mg/kg of methylphenidate twice per day.

RESULTS

Improvements related to medication were obtained on cognitive tests of attention and impulsivity as well as behaviors assessed by parent rating scales. In an interactive setting with their mothers, attentional abilities and the children's ability to work more productively also showed improvement. However, no changes were obtained with respect to the children's tendency to comply with parental requests. Side effects increased slightly with the high dosage of medication but remained mild.

CONCLUSION

The results suggest that methylphenidate can be used to improve the functioning of preschool-age children with ADHD, in a manner similar to their school-age counterparts.

Neonatal pain response to heel stick vs venepuncture for routine blood sampling

Neonatal pain response and adverse effects and maternal anxiety were assessed in 27 infants who were randomly allocated to venepuncture or heel stick. Pain was assessed by nurses using the Neonatal Infant Pain Scale (NIPS) and a three point scale for the mothers. NIPS scores were higher in the heel stick group compared with the venepuncture group. Maternal anxiety was higher before the procedure while perception of an infant's pain was lower in the venepuncture group compared with the heel stick group. Venepuncture is less painful than heel stick in newborn infants undergoing routine blood sampling.

Why can't most people draw what they see?

The study presented a theoretical and empirical approach to the adult drawing process. Four possible sources of drawing inaccuracies were described: misperception of the object, inability to make good representational decisions, deficient motor skills, and misperception of the drawing. In four studies the degree to which the latter three sources contributed to drawing inaccuracies was assessed. The results suggest that (a) motor coordination is a very minimal source of drawing inaccuracies, (b) the artist's decision-making process is a relatively minor source of drawing inaccuracies, and (c) the artist's misperception of his or her work is not a source of drawing inaccuracies. These results suggest that the artist's misperception of the object is the major source of drawing errors.

Why can't most people draw what they see?

The study presented a theoretical and empirical approach to the adult drawing process. Four possible sources of drawing inaccuracies were described: misperception of the object, inability to make good representational decisions, deficient motor skills, and misperception of the drawing. In four studies the degree to which the latter three sources contributed to drawing inaccuracies was assessed. The results suggest that (a) motor coordination is a very minimal source of drawing inaccuracies, (b) the artist's decision-making process is a relatively minor source of drawing inaccuracies, and (c) the artist's misperception of his or her work is not a source of drawing inaccuracies. These results suggest that the artist's misperception of the object is the major source of drawing errors.

A supervised learning network based on adaptive resonance theory

A neural network architecture, fuzzy ART with logistic discrimination (ART-LD), is introduced as a method of realising the pattern recognition task in a supervised learning manner. The system is formed by the hierarchical organisation of two network modules: a fuzzy ART and a logistic discrimination. The learning consists of two separate stages. Firstly, the fuzzy ART module self-organises the input patterns into category clusters, whose operations are governed by fuzzy set theory and "competitive learning" dynamics that ensure fast and stable learning. Then the outputs, which can be interpreted as fuzzy memberships of an input pattern to the encoded categories, provide the spatial distance information that is generalised by the subsequent logistic discrimination to give the final prediction. Examples are presented, and the generalisation capabilities of ART-LD are demonstrated through two simulated and one real classification problem.

Quantification of the relative contribution of major histocompatibility complex (MHC) and non-MHC genes to human immune responses to foreign antigens

Understanding the extent to which genetic factors influence the immune response is important in the development of subunit vaccines. Associations with HLA gene polymorphisms appear insufficient to explain the range of variation in immune responses to vaccines and to infections by major pathogens. In this study of Gambian twins we report that regulation of the immune response to a variety of antigens from Plasmodium falciparum and Mycobacterium tuberculosis is controlled by factors which are encoded by genes that lie both within and outside the major histocompatibility complex (MHC). We define the relative contribution of these genes, which varies for different antigens. The cumulative genetic contribution of non-MHC genes to the total phenotypic variance exceeds that of the MHC-encoded genes.

Statistical analysis of highly skewed immune response data

This paper considers methods of statistical analysis for highly skewed immune response data. Observations from population studies of immunological variables are rarely normally distributed between individuals; typically the distribution shows extreme levels of skewness. In some situations, skewness remains considerable even after transforming the data. Using resampling techniques, applied to several actual datasets of ELISA assay data, we consider the robustness of normal parametric methods, e.g. t tests and linear regression. Despite the skewness of the transformed data, we demonstrate that such methods are quite robust depending on the number of observations, type of analysis and severity of skewness. We also illustrate how bootstrap resampling can be used to provide a valid alternative method of analysis that can be used either for checking normal parametric analysis or as a direct method of analysis. We illustrate this combined approach by analysing real data to test for association between human serum antibodies to malaria merozoite surface proteins, MSP1 and MSP2, and resistance to clinical malaria, and confirm the protective effect of antibodies to MSP1 and demonstrated a similar protective effect for some antibodies to MSP2.