Ultrastructural assessment of Plasmodium falciparum in age-fractionated thalassaemic erythrocytes.

Culture of Plasmodium falciparum in age-fractionated thalassaemic red blood cells (RBC) has shown evidence of parasite damage on light microscopy in older cells during the third culture cycle (96-144 h). In this report, parasites growing in thalassaemic trait and normal RBC were examined ultrastructurally from 96 to 144 h. All parasite stages in old thalassaemic RBC showed evidence of damage worsening with culture duration. There were cytoplasmic alterations with ribosomal damage, and parasite cytoplasm became increasingly loose and grainy, with multiple fissures. Discontinuity of the nuclear membrane with an abnormal nucleolus was seen at l20 h. Cytosomes remained normal, but damage to the food vacuole and shrunken disintegrating parasites were observed at 144 h. These changes are compatible with cellular degeneration and developmental retardation and would account for the schizont maturation arrest and reduced reinvasion rates previously reported. Increased free radicals associated with thalassaemic erythrocytes would explain these changes, further supporting the role for oxidant stress in the protective mechanism.

Iron and its relation to immunity and infectious disease.

The continuing unresolved debate over the interaction of iron and infection indicates a need for quantitative review of clinical morbidity outcomes. Iron deficiency is associated with reversible abnormalities of immune function, but it is difficult to demonstrate the severity and relevance of these in observational studies. Iron treatment has been associated with acute exacerbations of infection, in particular, malaria. Oral iron has been associated with increased rates of clinical malaria (5 of 9 studies) and increased morbidity from other infectious disease (4 of 8 studies). In most instances, therapeutic doses of oral iron were used. No studies in malarial regions showed benefits. Knowledge of local prevalence of causes of anemia including iron deficiency, seasonal malarial endemicity, protective hemoglobinopathies and age-specific immunity is essential in planning interventions. A balance must be struck in dose of oral iron and the timing of intervention with respect to age and malaria transmission. Antimalarial intervention is important. No studies of oral iron supplementation clearly show deleterious effects in nonmalarious areas. Milk fortification reduced morbidity due to respiratory disease in two very early studies in nonmalarious regions, but this was not confirmed in three later fortification studies, and better morbidity rates could be achieved by breast-feeding alone. One study in a nonmalarious area of Indonesia showed reduced infectious outcome after oral iron supplementation of anemic schoolchildren. No systematic studies report oral iron supplementation and infectious morbidity in breast-fed infants in nonmalarious regions.

Red cell age and susceptibility to malaria during pregnancy.

BACKGROUND: Increased susceptibility to malaria in pregnancy is well recognized, and has generally been assumed to be due to hormonal changes resulting in altered immunity. Based on previous work demonstrating enhanced parasite growth in young normal and thalassemic red blood cells, we hypothesized that in pregnancy increased malaria susceptibility may be due, in part, to the increase in the population of young red cells. METHODS: FC27 strain of Plasmodium falciparum was cultured in the red cells and sera from healthy primigravida pregnant (n=9) and non-pregnant (n=9) women. Red cells from both pregnant and non-pregnant women were each placed in three cultures containing the sera from pregnant, non-pregnant and pooled control samples. Cultures were set up in triplicate and incubated for 144 hours. Parasite development and growth were assessed by slide microscopy. RESULTS: At 96 hours the median parasite growth in cells from pregnant samples (5.7%) was significantly better than that in the non-pregnant cells (4.8%) (p=0.01). There was no significant difference in parasite growth in cultures with pregnant and non-pregnant sera. As expected, there were significant differences in parameters measuring red cell age between the cells from pregnant and nonpregnant samples: median red cell creatine (11.09 mg/dl) versus (6.90 mg/dl) (p=0.004) and median reticulocyte count (2.3%) versus (1.4%) (p=0.0006). CONCLUSIONS: These preliminary results are consistent with the hypothesis that an increased population of young red cells may contribute to increased malaria susceptibility during pregnancy.

Iron and infection in the tropics: paediatric clinical correlates.

Iron deficiency is prevalent in children worldwide. Programmes of presumptive therapy, mass supplementation and food fortification have been introduced in many countries. The continuing unresolved debate over the interaction of iron and infection in the clinical setting indicates the need for firm guidelines for these practices. Iron overload is associated with increased susceptibility to certain infections, although the exact mechanisms may vary with the main pathology. Iron treatment has been associated with acute exacerbations of infection, in particular malaria. In Papua New Guinea parenteral iron was associated with increased rates of malaria and increased morbidity due to respiratory disease in infants but not in school children. Several subsequent studies in Africa using oral iron showed deleterious effects. In most instances cited, immunity was compromised, and therapeutic doses of oral iron were used. Knowledge of malarial endemicity, immunity with respect to age and the prevalence of haemoglobinopathies is important in planning interventions. A fine balance needs to be struck in the timing and dose of oral iron if informed recommendations are to be made. In parallel with supplementation studies, the effects of iron chelation on infection are being reported increasingly. Such therapy is clearly protective against malaria and some other infections but may predispose to fungal and Yersinia infections.

Meningitis in Hong Kong children, with special reference to the infrequency of haemophilus and meningococcal infection.

OBJECTIVE: To study the epidemiologic and aetiologic features of meningitis in children in Hong Kong. METHODOLOGY: A retrospective study of 85 children resident in the New Territory East region of Hong Kong admitted to a teaching Hospital because of meningitis during a 9 year period. RESULTS: Mycobacterium tuberculosis was the most common aetiological agent accounting for 13 cases (15.3%). Other bacteria accounted for 41 cases (48%); among these one fifth were caused by Haemophilus influenzae type b. The overall admission rates for tuberculous meningitis in Chinese children were 0.76/100,000 (95% CI 0.25-1.78) and 0.42/100,000 (CI 0.19-0.8) per year, respectively, for under 5 year olds and under 15 year olds. The overall annual incidence rates of bacterial meningitis other than tuberculous were 5.2/100,000 (CI 3.72-7.43) and 1.6/100,000 (CI 1.14-2.29) for Chinese children under 5 years and under 15 years, respectively. The annual incidence of H. influenzae meningitis in Chinese children under 5 years old was low at 1.1/100,000 (0.43-2.2). All five cases of meningococcal meningitis were in Vietnamese children (under 5 years of age incidence: 13.0/100,000 per year, CI 4.2-30.3). There were no cases of meningococcal meningitis in Chinese children during the 9 year period. CONCLUSION: M. tuberculosis was the most common aetiological agent of meningitis in Hong Kong children. The incidence of haemophilus or meningococcal meningitis was very low.

Echocardiographic evaluation of cardiac function in paediatric oncology patients treated with or without anthracycline.

Using Doppler echocardiography, we studied the left ventricular systolic and diastolic function in 124 healthy control children (group C), 110 oncology patients who had received anthracycline (group A), and 76 oncology patients who had received chemotherapy not including anthracycline (group N), at rest and after supine bicycle exercise. The mean dosage of anthracycline that group A patients received was 219 +/- 95 mg/m2. Impaired systolic function was detected in 29% of the patients in group A and 4% in group N. Figures for impaired diastolic function for group A and N were 27% and 28% respectively. Abnormal diastolic function was detected more frequently in the first two years after chemotherapy in both groups. Four parameters measured at rest appeared to be specifically abnormal in group A but not in group N. These were ejection fraction, fractional shortening, rate-corrected velocity of circumferential fiber shortening (VCFC) and left ventricle peak systolic wall stress (LVWS). After exercise more parameters were abnormal in group N patients when compared to normal children, but abnormalities of VCFC and LVWS remained specific for group A. In conclusion, abnormalities of diastolic function were common among paediatric oncology patients no matter whether they had received anthracycline treatment or not. Abnormalities of systolic function were more specific to anthracycline toxicity. VCFC and LVWS were the most sensitive measurements for differentiating group N patients from group A patients.

Invasion and growth of Plasmodium falciparum is inhibited in fractionated thalassaemic erythrocytes.

Epidemiological and clinical studies have indicated that the thalassaemias may confer protection against malaria. The study reported here investigated this protective effect in vitro, using a new approach which controls for the potential effect of red cell size and age on the virulence of the parasite. A Percoll density gradient method was used to separate alpha- and beta-thalassaemic trait, haemoglobin H and normal red blood cells (RBC) into fractions of different density. Correlations between RBC density, age and size in fractions of all genotypes were established using red cell creatine as an index of cell age. The development of Plasmodium falciparum over 3 erythrocytic cycles (144 h) in whole blood as well as fractionated samples was monitored by slide microscopy and flow cytometry. A significantly reduced rate of parasite invasion and growth was demonstrated in RBC from all thalassaemic genotypes tested. Poor reinvasion rates were noted in the second and third cycles. Increased duration of culture and red cell age also had a greater negative impact on parasite growth in thalassaemic RBC. This poor growth rate was also associated with the arrest of parasite growth at the schizont stage (schizont maturation arrest) and the accumulation of abnormal, trophozoite/schizont stage parasites in the older thalassaemic RBC fractions. These findings suggest a defect in the number and viability of merozoites generated by parasites growing in thalassaemic RBC. Age related factors such as oxidant stress may play a key role in mediating this kind of protective mechanism and deserve further investigation.

Thalassaemia trait, red blood cell age and oxidant stress: effects on Plasmodium falciparum growth and sensitivity to artemisinin.

Knowledge of innate mechanisms of protection against malaria could be used to bolster the existing limited treatments. Oxidant stress may play a role in the protective mechanism and the effect of red blood cell (RBC) age has recently been recognized. This study investigated the role of oxidant stress in the protection against malaria in thalassaemic trait RBC (alpha and beta) using an experimental approach which controlled for cell age. 'Young', 'intermediate' and 'old' RBC obtained by Percoll fractionation and whole blood were used to set up malaria cultures. Antioxidants (vitamin E and dithiothreitol) and pro-oxidants (riboflavin, menadione and artemisinin) were added to modulate oxidant stress effect. Antioxidants improved parasite growth. The degree of improvement was significantly greater with increasing RBC age (P < 0.0001), and relatively greater in thalassaemic RBC (P < 0.0001). Pro-oxidants had a parasiticidal effect. With the exception of the 'old' RBC fraction, the median inhibitory concentration (IC50) for riboflavin and menadione was significantly higher in normal RBC. In contrast, the IC50 for artemisinin was significantly higher in 'old' thalassaemic RBC but was similar in the 'young' and 'intermediate' fractions and whole blood. These findings suggest that oxidant stress plays a role in mediating the protection against malaria in thalassaemic RBC. Vitamin E and other antioxidant supplementation could feasibly exacerbate clinical malaria. Conversely, pro-oxidant agents could act as useful adjuvants to therapy. It is important to confirm the reduced sensitivity to artemisinin in 'old' thalassaemic trait RBC, as such an effect may promote selective pressure for the emergence of resistant parasite strains with widespread use of artemisinin.

Weight-for-age and weight-for-height references for Hong Kong children from birth to 18 years.

OBJECTIVE: Childhood obesity is an emerging problem in Asia. Sequential monitoring of the growth of an individual can detect a change in body fatness, provided there are ethnically appropriate growth references. METHODOLOGY: A territory wide cross-sectional growth survey of Hong Kong on 24709 individuals from the age of newborn to 18 years was performed in 1993. Weight-for-age and weight-for-height percentile charts were prepared separately for boys and girls. RESULTS: There was an average increase of 8.5 kg and 5.1 kg in the 18 year old boys and girls, respectively, compared to those surveyed 30 years ago. The percentile curves between 6 and 18 years were similar to those of Singapore. Weight-for-height percentile curves were close to those of America in the prepubertal years. CONCLUSIONS: These Hong Kong growth standards for weight-for-age and weight-for-height are important tools for the assessment of nutritional status of an individual and for monitoring changes in nutritional status of the population.

Carriage of Haemophilus influenzae and Streptococcus pneumoniae in healthy Chinese and Vietnamese children in Hong Kong.

Nasopharyngeal carriage of Haemophilus influenzae and Streptococcus pneumoniae was studied in 621 healthy Chinese children and 300 healthy Vietnamese children aged from 2 months to 5 years in Hong Kong. The carriage rate of H. influenzae type b in Vietnamese children was 1.3% (CI 0.04-2.63); it was zero in Chinese. The carriage rate of non-typable H. influenzae was 5.8% (CI 1.4-7.6%) in Chinese and 65.4% (CI 58.9-69.8%) in Vietnamese. The carriage rates of S. pneumoniae were 10.8% (CI 8.3-13.2%) and 55.7% (CI 50.1-61.3%) in Chinese and Vietnamese children, respectively. Univariate and multivariate logistic regression analyses were performed to search for factors associated with differences in carriage rates of both H. influenzae and S. pneumoniae between Chinese and Vetnamese children. Although older age, smaller living area and parental smoking were associated with higher carriage rates, these could not explain the remarkably low carriage rates of both bacteria in Chinese children.

Invasive Haemophilus influenzae type b infections in children hospitalized in Hong Kong, 1986-1990. Hong Kong Hib Study Group.

A 5-year territory-wide retrospective survey of invasive Haemophilus influenzae type b diseases was conducted in Hong Kong. Between 1986 and 1990, 57 cases (28 male) were recorded in children less than 12 years old (37 cases of meningitis, 9 of septicaemia and 11 of bacteraemic pneumonia). The annual incidence for children less than 5 years old was 2.7 per 10(5) (95% confidence interval (CI) 2.0-3.5). Of the 57 cases, 39 were Chinese and 18 non-Chinese (7 Vietnamese refugees, 6 Caucasians, 5 others). The annual incidence in Vietnamese refugees less than 5 years old was 42.7 per 10(5) (95% CI 17.2-87.9), giving a relative risk of 18.5 (95% CI 8.3-41.0). Chinese patients (68%) were under-represented as Chinese accounted for at least 94% of the population. Moreover, 14 of the 39 Chinese patients had pre-existing medical problems, compared with only 1 of the 18 non-Chinese patients patients had pre-existing medical problems, compared with only 1 of the 18 non-Chinese patients (p = 0.022).

Goitre in southern Chinese children in Hong Kong.

In a 9-year retrospective review of goitre in Chinese children in Hong Kong, 84 children and adolescents were identified. There was a female predominance with a male:female ratio of 1:5.5. The majority of patients (95%) were found to have diffuse enlargement of the thyroid gland. Forty-nine were found to have Graves' disease. The mean age of presentation of patients with Graves' disease was 11.34 years. Forty-three of them were found to have thyroid autoantibodies. Only two cases of autoimmune thyroiditis with thyroid autoantibodies were diagnosed. The other causes of goitre include simple colloid goitre, multinodular goitre and suppurative thyroiditis. The spectrum of disease causing goitre in Chinese children is thus quite different from that reported in Caucasian children in developed countries. Further studies are necessary to define the genetic or environmental factors resulting in the observed differences.

Double-blind, controlled calcium supplementation and bone mineral accretion in children accustomed to a low-calcium diet.

A randomized, double-blind, controlled calcium supplementation trial was conducted for 18 mo to determine its effects on bone acquisition and height increment in 162 7-y-old Chinese children (87 boys and 75 girls) with habitually low calcium intakes (280 mg/d). Distal one-third radial bone mineral content (BMC), area bone density (BMC/bone width), and height were evaluated every 6 mo. Baseline dietary intakes, serum 25-hydroxycholecalciferol, and physical activity were determined. The study group received 300 mg Ca/d as calcium carbonate; control subjects received placebo tablets. After 18 mo the study group had significantly greater gains in BMC (16.5% vs 13.97%; P = 0.02) and BMC/bone width (9.45% vs 6.31%; P = 0.0008) than the control subjects. The findings confirm a positive effect of calcium intake on bone acquisition but no effect on height increment. Whether a higher bone mass attained at age 8-9 y would be maintained and beneficial to future peak bone mass requires longitudinal investigation. Further study is warranted to determine calcium requirements for Chinese children.

Oral calcium treatment in vitamin D-dependent rickets type II.

Vitamin D-dependent rickets type II is a rare hereditary disease that results from target organ resistance to the action of 1,25-dihydroxyvitamin D3. There is a great heterogeneity in the clinical presentation of this condition. The affected patients usually present early in childhood with clinical and biochemical evidence of rickets. Physiological replacement dosage of 1,25-dihydroxyvitamin D3 has no therapeutic effect. Responses to pharmacological doses of vitamin D metabolites or long-term calcium infusion have been variable. A case is reported here of an 8 year old girl, of consanguineous parents with vitamin D-dependent rickets, type II, in whom treatment with high dose oral calcium resulted in marked biochemical and radiological improvement. It is concluded that high dose oral calcium treatment is an effective treatment option for patients with vitamin D-dependent rickets type II.

Intracranial tuberculoma and hydrocephalus developing during treatment of tuberculous meningitis.

A 3 1/2-year-old boy with tuberculous meningitis is described. He developed hydrocephalus and subsequently an intracranial tuberculoma while receiving appropriate antituberculous therapy. Such a paradoxical response is thought to be due to a hypersensitivity reaction to the infection during antituberculous therapy. Both hydrocephalus and tuberculomata should be looked for if any patient develops new neurological signs or symptoms during treatment of tuberculous meningitis.

Rapid serodiagnosis of typhoid fever by dot enzyme immunoassay in an endemic area.

A dot enzyme immunoassay (EIA) using 50-kD outer-membrane proteins (OMPs) of Salmonella typhi was compared with the Widal test for the serodiagnosis of typhoid fever in 109 febrile children admitted to a hospital in an endemic area. In the culture-positive typhoid group, the initial dot EIA was positive in 40 of 42 cases and the initial Widal test was positive in 41. In the culture-negative clinical typhoid group, both the dot EIA and the Widal test were positive in 17 of 18 cases. In the nontyphoidal fever group, the dot EIA was negative in all of 49 cases and the Widal test was negative in 44. With culture used as the gold standard, the dot EIA is as sensitive as the Widal test (95% vs. 98%), has a similar high negative predictive value (96% vs. 98%), and is more specific (75% vs. 67%). In addition, the dot EIA offers the advantages of simplicity, speed, early diagnosis, economy, and flexibility (i.e., other diagnostic tests can be conducted simultaneously).

Childhood abdominal tuberculosis. The role of echo-guided fine-needle aspiration in its management.

Two children presented with abdominal tuberculosis. Because of the nonspecific clinical features, the diagnosis required a high index of clinical suspicion. Fine-needle aspiration (FNA) under ultrasonographic guidance allowed an early definitive diagnosis and bacteriological confirmation to guide chemotherapy. Both patients responded well to antituberculous chemotherapy.

Epidemiology and etiology of pneumonia in children in Hong Kong.

The epidemiologic and etiologic features of cases of pneumonia among 1,740 children admitted to a teaching hospital in Hong Kong over a 3-year period were studied. Of the patients, 23% were < 1 year old and 69% were < 5 years old. The incidence of pneumonia requiring admission to the hospital was 6.4 episodes per 1,000 children per year for those < 5 years of age. The overall case fatality rate was 0.15% among patients who did not have severe underlying disease before contracting pneumonia. A bacterial etiology was confirmed by blood culture for only 2% of patients. However, culture of sputum or nasopharyngeal aspirates yielded predominant or pure growth of one bacterial agent in 17% of cases. Haemophilus influenzae was the bacterial agent most frequently isolated from nasopharyngeal aspirates or sputum, followed by Streptococcus pneumoniae and Staphylococcus aureus. Of the H. influenzae isolates, 38% were resistant to ampicillin. A viral etiology was proven in 9.1% of cases, and evidence of mycoplasmal infection was found in 3.8% of cases. Respiratory syncytial virus was the most frequently identified viral agent, followed by adenovirus and influenza A virus.

Treatment of respiratory syncytial virus infection with recombinant interferon alfa-2a.

A prospective randomised, double blind, controlled trial was conducted in 52 infants to determine whether recombinant interferon alfa-2a (INF-alpha-2a) would reduce the morbidity of acute bronchiolitis and the respiratory syncytial virus shedding time. All infants had a positive direct antigen immunofluorescence test for respiratory syncytial virus. INF-alpha-2a (50,000 IU/kg/day) or placebo was administered by daily intramuscular injection for three consecutive days. Sixteen infants received INF-alpha-2a and 36 received placebo treatment. The two groups were similar in demographic characteristics and initial oxygenation. The treatment group, however, had a significantly higher overall score for severity of illness at the start of treatment. More rapid drop of the clinical score was observed in the INF-alpha-2a group after treatment in the first three days and the two groups had similar clinical severity by day 3. There was no significant difference of the duration of viral shedding in the two groups. In conclusion, the overall clinical improvement was greater in the treatment group over the first three days, but the duration of viral shedding was not altered.