Association between infection with Helicobacter pylori and atopy in young Ethiopian children: A longitudinal study

BACKGROUND

Epidemiological evidence from developed countries indicates that Helicobacter pylori infection correlates with a reduced risk of atopy and allergic disorders; however, limited data are available from low-income countries.

OBJECTIVE

We examined associations between H. pylori infection in early childhood and atopy and reported allergic disorders at the age of 6.5 years in an Ethiopian birth cohort.

METHODS

A total of 856 children (85.1% of the 1006 original singletons in a population-based birth cohort) were followed up at age six and half years. An interviewer-led questionnaire administered to mothers provided information on demographic and lifestyle variables. Questions on allergic disease symptoms were based on the International Study of Asthma and Allergies in Children (ISAAC) core allergy and environmental questionnaire. Serum samples were analysed for total IgE levels and anti-H. pylori cytotoxin-associated gene A (CagA) IgG antibody using commercially available ELISA kits. Stool samples were analysed for H. pylori antigen using a rapid immunochromatographic test. The independent effects of H. pylori infection (measured at age of 3, 5 and 6.5 years) on prevalence and incidence of atopy and reported allergic disorders (measured at age of 6.5 years) were determined using multiple logistic regression.

RESULTS

In cross-sectional analysis, current H. pylori infection at age 6.5 years was inversely, though not significantly, related to prevalence of atopy and "any allergic condition" at age 6.5 years. However, detection of H. pylori infection at any point up to age 6.5 years was associated with a significantly reduced odds of both atopy and "any allergic condition" (adjusted OR AOR, 95% CI, 0.54; 0.32-0.92, P = .02, and .31; 0.10-0.94, P = .04, respectively). In longitudinal analyses, H. pylori infection at age 3 was inversely associated with incidence of atopy (AOR, 95% CI, 0.49; 0.27-0.89, P = .02). Furthermore, among H. pylori-infected children, those with a CagA+ strain had a more pronounced reduction in odds of atopy (AOR = 0.35 vs 0.63 for CagA+ vs CagA-), and this reduction reached borderline significance.

CONCLUSION

These data are consistent with the hypothesis that early exposure to H. pylori is inversely associated with atopy and allergic conditions. A possible modest protective association against atopy was observed in those infected with a more virulent CagA+ strain of H. pylori.

Does decentralisation of tuberculosis care influence treatment outcomes? The case of Oromia Region, Ethiopia

SETTING

Oromia Region, Ethiopia.

OBJECTIVE

To investigate the effect of decentralised care on anti-tuberculosis treatment outcomes and identify factors affecting outcome among new smear-positive tuberculosis (TB) patients.

DESIGN

This was a retrospective cohort study comparing patients treated in the community during the continuation phase with those managed throughout treatment in health facilities. Data were collected from TB registers and patient cards using a pre-tested data capture form.

RESULTS

Of the 2226 new smear-positive TB patients registered from July 2010 to June 2012 who were included in the study, 1599 (72.6%) received treatment in health facilities, and the rest in the community. Overall treatment success was 94.7%. Patients treated in the community had comparable treatment success with those managed in health facilities (aOR 1.7, 95%CI 0.80-3.57). Missing doses (OR 0.22, 95%CI 0.08-0.55), supervision during the continuation phase (OR 2.6, 95%CI 1.34-5.05), positive sputum at month 2 (OR 0.07, 95%CI 0.04-0.13) and human immunodeficiency virus infection (OR 0.25, 95%CI 0.13-0.46) were independent predictors of treatment success.

CONCLUSION

Overall treatment success is high in new smear-positive TB patients in Oromia. Patients receiving treatment in the community during the continuation phase have treatment success comparable with that of patients managed in health facilities.

Seroepidemiology of hepatitis B virus in Addis Ababa, Ethiopia: transmission patterns and vaccine control

A community-based seroepidemiological survey of Addis Ababa, Ethiopia was conducted in 1994 to inform on the transmission dynamics and control of hepatitis B virus (HBV) infection. Venous blood from 4736 individuals under 50 years of age from 1262 households, selected using stratified cluster-sampling, was screened for HBV markers using commercial ELISAs. HBsAg prevalence was 7% (95 % CI 6-8), higher in males (9%; 7-10) than females (5%; 4-6). HBeAg prevalence in HBsAg positives was 23% (18-29), and less than 1% of women of childbearing age were HBeAg positive. Overall HBV seroprevalence (any marker), rose steadily with age to over 70% in 40-49 year olds, indicating significant childhood and adult transmission. Estimated instantaneous incidence was 3-4/100 susceptibles/year, higher in males than females in 0-4 year olds, and peaking in early childhood and young adults. The age at which 50% had evidence of infection was around 20 years, and the herd immunity threshold is approximated at 63-77%. Addis Ababa is of intermediate-high HBV endemicity, with negligible perinatal transmission. Our main findings are the identification of a significant difference between males and females in the age-acquisition of HBV infection, and marked differences between age groups in HBV incidence rates. These results should target future research studies of underlying risk factors. Furthermore, we generate a crude estimate of the level of coverage of HBV vaccine that would be required to eliminate the virus from the study population.

Seroepidemiology of measles in Addis Ababa, Ethiopia: implications for control through vaccination

We undertook a representative survey of measles antibodies in Addis Ababa, Ethiopia 1994, to characterize immunity and transmission. Specific-antibody levels (IU/l) were determined by ELISA for 4654 sera from individuals aged 0-49 years (1805 < 15 years) collected by stratified household-cluster sampling. The proportion seronegative (< 100 IU/l) was 20% (95% CI: 16-25) in children 9-59 months old, declining to 9% (7-12) in 5-9 year olds, 5% (4-7) in 10-14 year olds, and < 1% in adults. The proportion of children (< 15 years old) with low-level antibody (100-255 IU/l) was 8% (7-10). Vaccination and an absence of a history of measles illness were strongly associated with low-level antibody. History of measles vaccination in 9 months to 14-year-old children was approximately 80%. We estimate a primary vaccine failure rate of 21% (12-34) and continued high measles incidence of 22 per 100 susceptibles (19-24) per annum. Our data support the introduction of campaign vaccination in the city in 1998, although higher routine vaccine coverage is required to sustain the impact. The implications of a high prevalence of low-level antibody are discussed.

Improving sensitivity of oral fluid testing in IgG prevalence studies: application of mixture models to a rubella antibody survey

A method for the analysis of age-stratified antibody prevalence surveys is applied to a previously reported survey of antibody to rubella virus using oral fluid samples in which the sensitivity of the assay used was shown to be compromised. The age-specific distribution of the quantitative results of antibody tests using oral fluids is modelled as a mixture of strong positive, weak positive and negative components. This yields maximum likelihood estimates of the prevalence at each age and demonstrates that, when used in conjunction with mixture modelling techniques, the results of antibody prevalence studies using oral fluids accurately reflect those obtained using sera.

Has oral fluid the potential to replace serum for the evaluation of population immunity levels? A study of measles, rubella and hepatitis B in rural Ethiopia

OBJECTIVE

To assess the suitability of using oral-fluid samples for determining the prevalence of immunity to vaccine-preventable infections.

METHODS

Paired blood and oral-fluid samples were obtained from 853 individuals of all ages from a rural Ethiopian community. Oral fluid around the gums was screened for measles- and rubella-specific antibodies using enhanced IgG antibody capture (GAC) enzyme-linked immunosorbent assays (ELISAs), and for anti-HBc antibodies using a prototype GACELISA. IgG antibodies in serum to measles, rubella and HBc were determined using commercial ELISAs.

FINDINGS

Relative to serum, oral fluid assay sensitivity and specificity were as follows: 98% and 87% for measles, 79% and 90% for rubella, and 43% and 87% for anti-HBc. These assay characteristics yielded population prevalence estimates from oral fluid with a precision equal to that of serum for measles (all ages) and rubella (ages < 20 years).

CONCLUSION

Our results suggest that oral fluid could have the potential to replace serum in IgG antibody prevalence surveys. Further progress requires assessment of variation in assay performance between populations as well as the availability of standardized, easy to use assays.

Sero-epidemiology of rubella in the urban population of Addis Ababa, Ethiopia

We conducted a community-based cluster sample survey of rubella sero-epidemiology in Addis Ababa, Ethiopia in 1994. Among 4666 individuals for whom complete data were available, rubella antibody prevalence was 91% (95% confidence interval: 90, 92). On multivariable analysis, seroprevalence was lower among individuals who were resident in Addis Ababa for 1 year or less. Approx. 50% seroprevalence was attained by age 4 years, and the estimated average age at infection was 5.2 years. The highest age-specific force of infection was estimated to occur in 5- to 9-year-olds. The early age at infection corresponded with a low estimated incidence of congenital rubella syndrome (CRS) of 0.3 per 1000 live births, equivalent to nine cases of CRS in 1994. The predicted critical level of immunity for elimination of rubella via vaccination was 85-91%, requiring 89-96% coverage with a vaccine of 95% effectiveness. Unless very high coverage of rubella vaccine could be guaranteed, the introduction of childhood vaccination could increase the incidence of CRS in Addis Ababa.

Detection of measles specific IgG in oral fluid using an FITC/anti-FITC IgG capture enzyme linked immunosorbent assay (GACELISA)

An IgG antibody capture enzyme linked immunosorbent assay (GACELISA) for the detection of measles specific IgG in oral fluid was developed using an FITC/anti-FITC amplification system. The GACELISA was evaluated by testing paired oral fluid and serum samples from 787 subjects in an epidemiological study of measles in rural Ethiopia. Oral fluids were tested by GACELISA and corresponding serum samples by a sensitive indirect ELISA for measles IgG (Behring Enzygnost). By comparison with the serum measles IgG assay, the oral fluid GACELISA had a sensitivity of 97.4% (95% confidence intervals: 95.9, 98.2) and a specificity of 90.0% (81.9, 94.3), with no significant differences observed by age group. Total IgG concentrations were measured on a subset of 160 oral fluids by an in-house ELISA. This showed that false negative GACELISA results tended to occur in samples with low concentrations of total IgG, although the trend was not statistically significant. It is concluded that the overall performance of the GACELISA was satisfactory, showing close agreement to the serum ELISA, and has potential to serve as an easily transferable tool for large scale epidemiological studies as required for the World Health Organisation's programme for the global control of measles.

Helicobacter pylori infection in Ethiopian children: a cohort study

Risk factors for infection with Helicobacter pylori (HP) were investigated in a cohort study of 121 seronegative children in Ethiopia aged 2-4 y, who had previously participated in a case-control study. Blood samples were drawn at inclusion in the cohort study and again after 12 and 30 months. At 12 months the parents were also interviewed about putative risk factors for infection, using a structured questionnaire. Analyses were made by comparing risk factors in seropositive and seronegative children. The seroconversion rate during the first year was 31% (27/87) and during the following 18 months 34% (17/50; corresponding to an annual incidence of 24%). After a period of 30 months, 58% (14/24) of the children who were 24-29 months old at inclusion in the study had seroconverted, compared with 40% (4/10) of those who were 30-35 months old, 73% (22/30) of those who were 36-41 months old and 31% (4/13) of those who were 42 months old or more. These results indicate that peak age for HP infection is below 6 y in this cohort in Ethiopia, and might also reflect a pattern of repeated seroconversion and sero-reversion in early childhood. Independent predictors of HP-seroconversion were the variables 'drinking-water', comparing water from a well with water from rivers or pipes (RR = 1.46, 95% CI 1.0-2.15) and 'antibiotic treatment' (RR = 1.84, 95% CI 1.16-2.92).

Risk factors for infection with Helicobacter pylori--a study of children in rural Ethiopia

The public health impact of Helicobacter pylori (HP) infection is gradually becoming obvious, the bacterium now being implicated as an aetiologic agent in a variety of gastric diseases. Transmission routes still remain unknown, although single risk factors, such as domestic crowding (especially bed-sharing) in childhood and low parental socioeconomic status, have been pointed out in studies from developed countries. In an attempt to study the risk factors in a developing country, we performed a case control study of 242 randomly selected children aged 2-4 y in Butajira rural area in Ethiopia. Blood samples were drawn and a questionnaire administered. The total prevalence of IgG antibody to HP among the children in the region was 48% (116/242). Several risk factors such as: crowding, water, animals, sanitation, etc. correlated strongly to seropositivity in a univariate analysis. After controlling for possible confounding, independent predictors of seropositivity were: living in town (OR = 2.15, p = 0.001), increasing age (OR = 1.71, p = 0.060), and being a Muslim (OR = 1.54, p = 0.005). It could not be excluded that a bad water supply in town could explain the difference in seroprevalence between town and village. These results indicate that, in developing countries, factors relating to community and religion might be as important risk factors for infection with HP in children as characteristics of the family or the home.

An evaluation of oral-fluid collection devices for the determination of rubella antibody status in a rural Ethiopian community

We compared 3 different oral-fluid collection devices to assess their suitability for use in community studies of rubella antibody. Of 58 individuals enrolled from 13 households from a southern Ethiopian village, 38 provided a blood sample and oral fluids by the 3 devices: 2 proprietary, Omni-SAL and OraSure, and a third a polystyrene sponge swab (Sponge). The Sponge swab, used like a toothbrush, was most acceptable to survey staff and to participants of all ages, although it proved ill-adapted for fluid extraction. The other devices more often caused participant discomfort or anxiety, particularly in the young. Statistical comparison of rubella-specific immunoglobulin (Ig) G in oral fluid, measured by antibody-capture radioimmunoassay, and in serum, by indirect enzyme-linked immunosorbent assay, showed no clear differences between the devices in oral-fluid performance. Specificity range was 75-100% and sensitivity 73-85%, relative to serum. Specific-antibody levels declined with increasing age, with concomitant decreases in sensitivity, as previously documented. The relationship between specific IgG and total IgG in oral fluid differed by device. Specific IgG levels were highly correlated between paired samples using the Sponge device. We consider the Sponge device to be the most suitable for community survey work, although the extraction method requires improvement. Further work is needed to improve the sensitivity of antibody status determination in adults.

A case-control study on determinants of rickets

A case-control study on rickets was performed on 156 cases and 307 controls admitted to Birla pediatric wards, Yekatit 12 Hospital. The following factors were significantly (p < 0.05) associated with diagnosis of rickets in univariate analysis: male gender, being a twin, abnormal birth weight, malnutrition, higher birth order, higher number of siblings, having a caretaker who is not the mother, lower education of the caretaker, having a caretaker who is not housewife, and with protective effect, exposure to sunshine (in number of days per week, duration of daily exposure in minutes, and not wearing clothes during exposure). In multivariate analysis, the following factors remained independently associated with diagnosis of rickets in children: being a twin (OR = 5.86, 95% CI = 1.40-24.50), history of high birth weight (OR = 8.94, 95% CI = 2.30-34.70), moderate and severe malnutrition (OR = 5.64, 95% CI = 2.30-13.80 for severe malnutrition when compared to normal weight), having the grand mother as caretaker (OR = 19.80, 95% CI = 3.70-104.70), and with protective effect, exposure to sunshine (OR associated with an increase of one day of exposure per week = 0.65, 95% CI 0.55-0.77; OR associated with daily exposure of more than 30 minutes, when compared to less than 15 minutes = 0.24, 95% CI = 0.09-0.64; and OR associated with being nude while exposed to sunshine = 0.32, 95% CI = 0.14-0.73). There was no significant difference between cases and controls in marital status or religion of the caretakers.

A comparison of oral fluid and serum for the detection of rubella-specific antibodies in a community study in Addis Ababa, Ethiopia

OBJECTIVE

To assess the utility of oral fluid compared with serum for the determination of age-prevalence of rubella-specific antibodies in an urban African community setting.

METHOD

Paired serum and oral fluid samples were collected from 439 individuals aged 0-49 years in Addis Ababa, Ethiopia, as part of a larger seroepidemiological survey in 1994. Oral fluid was sampled using a simple sponge device that was well accepted by subjects of all ages; venous blood was collected by Vacutainer system. We measured rubella-specific antibodies in serum by the Radial Haemolysis (RH) test, supported by two confirmatory assays, and in oral fluid by IgG antibody-capture radioimmunoassay (GACRIA).

RESULTS

Sensitivity and specificity of oral fluid results compared to serum were 89% and 76%, respectively. Sensitivity declined from 96% in age group 0-19 years to 90% in age group 20-29 and 78% in age group 30-49. Specificity was 86% in 0-9 year olds contrasting with 61% in older groups (10-49 years). The positive predictive value of an oral fluid sample was high in all age groups (range 92-100%), while the negative predictive value declined from > or =80% in those aged <10 years to <10% in those aged > or =30 years. Serum confirmatory tests suggested a proportion of false serum RH negatives, increasing with age, indicating a need to standardize serum as well as oral fluid tests.

CONCLUSION

In the community setting of a developing country, oral fluid surveys could be useful to estimate age-prevalence of rubella immunity and identify rubella-susceptible children for follow-up. Further work is required to simplify assays and sample processing, improve assay sensitivity and estimate assay specificity more precisely, and compare and standardise collection methods suitable for surveillance of a variety of childhood viral infections.

Age- and sex-specific HIV-1 prevalence in the urban community setting of Addis Ababa, Ethiopia

OBJECTIVE

To estimate the age and sex-specific prevalence of HIV infection in the population of Addis Ababa, Ethiopia.

DESIGN

Two-stage cluster sampling of the population aged 0-49 years of Addis Ababa, using kebeles (urban dwelling associations) as clusters.

METHODS

The sera used for this study were collected in an earlier study (1994) on the rate of acquisition of antibodies against measles, rubella, and hepatitis B. After separate approvals were obtained from the institutional ethics committees, sera were tested by enzyme-linked immunosorbent assay confirmed by Western blot. Age- and sex-specific HIV prevalence rates were estimated. The prevalence of HIV in men and women over 15 years of age was compared by calculating age-standardized HIV prevalence, using the age distribution of the census population as the standard. A time-dependent catalytic model was used to obtain crude estimates of HIV incidence from age-prevalence data.

RESULTS

A total of 3853 sera were available for analysis. The prevalence of HIV in adults was 6.0% [95% confidence interval (CI), 4.5-7.4%] for men and 6.9% (95% CI, 5.3-8.5%) for women, with peak prevalence in the 25-29 year age group of 16.3 and 11.8%, respectively. After standardization for age using the direct method, the HIV prevalence ratio comparing adult men with women was 0.97:1 (95% CI, 0.70:1 - 1.35:1). Three children aged less than 5 years were HIV-positive. The prevalence of HIV among adults ranged from 0-21.3% in different clusters, indicating the heterogeneity of the spread of HIV in the city. HIV prevalence estimates among the antenatal clinic patients of Addis Ababa in 1996 far exceeded the estimates obtained during the community survey, particularly in the youngest age group (15-24 years). Estimates of HIV incidence (per susceptible person per annum) for the age group 16-22 years ranged from 1.3-2.25% for men and from 2.1-2.4% for women.

CONCLUSION

By 1994, a substantial proportion of the adult population of Addis Ababa was infected with HIV. Promotion of behavioural changes and the control of sexually transmitted diseases should be strongly supported to limit the spread of the HIV epidemic in Ethiopia.

Seasons, temperature and coronary disease

Using data from a community-based register of heart disease (the WHO MONICA Project) associations between daily temperature, rainfall and other seasonal effects were investigated in relation to fatal coronary events and non-fatal definite myocardial infarctions in an Australian population. Coronary events, both fatal and non-fatal, were 20-40% more likely to occur in winter and spring than at other times of the year. Coronary deaths were more likely to occur on days of low temperature (and to a much lesser extent, on days of high temperature). No differences were found between patterns of sudden and non-sudden deaths (those occurring later after the onset of symptoms) associated with weather conditions. Statistical models allowing simultaneously for longer-term seasonal effects and daily temperature effects suggested that both exist. These results suggest that avoiding temperature stress could lead to reductions in the annual peaks in coronary events.