A population-based study of the prevalence and risk factors of low-grade Plasmodium falciparum malaria infection in children aged 0-15 years old in northern Tanzania

OBJECTIVES

Northern Tanzania experiences significant malaria-related morbidity and mortality, but accurate data are scarce. We update the data on patterns of low-grade Plasmodium falciparum malaria infection among children in northern Tanzania.

METHODS

Plasmodium falciparum malaria prevalence (pfPR) was assessed in a representative sample of 819 children enrolled in 94 villages in northern Tanzania between October 2015 and August 2016, using a complex survey design. Individual- and household-level risk factors for pfPR were elicited using structured questionnaires. pfPR was assessed using rapid diagnostic tests (RDTs) and thick film microscopy (TFM). Associations with pfPR, based on RDT, were assessed using adjusted odds ratios (aOR) and confidence intervals (CI) from weighted survey logistic regression models.

RESULTS

Plasmodium falciparum malaria prevalence (pfPR) was 39.5% (95% CI: 31.5, 47.5) by RDT and 33.4% (26.0, 40.6) by TFM. pfPR by RDT was inversely associated with higher-education parents, especially mothers (5-7 years of education: aOR 0.55; 95% CI: 0.31, 0.96, senior secondary education: aOR 0.10; 95% CI: 0.02, 0.55), living in a house near the main road (aOR 0.34; 95% CI: 0.15, 0.76), in a larger household (two rooms: aOR 0.40; 95% CI: 0.21, 0.79, more than two rooms OR 0.35; 95% CI: 0.20, 0.62). Keeping a dog near or inside the house was positively associated with pfPR (aOR 2.01; 95% CI: 1.26, 3.21). pfPR was not associated with bed-net use or indoor residual spraying.

CONCLUSIONS

Nearly 40% of children in northern Tanzania had low-grade malaria antigenaemia. Higher parental education and household metrics but not mosquito bed-net use were inversely associated with pfPR.

Plasma cytokine levels and human papillomavirus infection at the cervix in rural Nigerian women

INTRODUCTION

We conducted a study to test the hypothesis that systemic dysregulation of Th1/Th2 cytokine levels was associated with detection of carcinogenic or overall human papillomavirus (HPV) at the cervix among 964 women residing in a rural village in Nigeria.

METHODS

Levels in plasma were measured for 19 cytokines, including Th1-like cytokines IL-2, IL-12 (p40), TNF-a, IFN-g; Th2-like cytokines IL-4, IL-5, IL-6, IL-10, IL-13; innate/inflammation cytokines IL-1a, IL-1b, IL-8, eotaxin, MCP-1, MIP-1a, and IL-7; and cell development cytokines G-CSF, VEGF, and IL-17. Analysis was restricted to 5 cytokines, TNF-α (Th1), IL-8 (Th2), eotaxin and MCP-1 (innate/inflammation), and G-CSF (cell development), whose levels were detected in 80% or more of the samples measured as well as had a coefficient of variation of <30%.

RESULTS

Strong correlations were noted between levels of eotaxin and TNF-α (r=0.75), IL-8 and MCP-1 (r=0.60), eotaxin and G-CSF (r=0.44), and G-CSF and IFN-γ (r=0.43). Detection of carcinogenic or non-carcinogenic HPV DNA was unrelated to cytokine levels, except for levels of eotaxin and TNF-α, which were inversely correlated, albeit weakly, with detection of any carcinogenic HPV (P=0.048 and P=0.067, respectively). In analyses stratified by age group, levels of eotaxin were inversely correlated with detection of any HPV DNA (P=0.026) and carcinogenic HPV (P=0.042) in older, but not younger, women.

CONCLUSIONS

Our results do not support the hypothesis of association between systemic cytokine dysregulation and detection of HPV at the cervix in Nigerian women, but subgroup analyses raise questions about inverse associations between eotaxin and TNF-α in older women.

Incidence of visual loss in rural southwest Uganda

BACKGROUND

Surveys have been conducted to measure prevalence of eye disease in Africa, but not of incidence, which is needed to forecast trends. The incidence of visual loss is reported in southwest Uganda.

METHODS

A rural population residing in 15 neighbouring villages was followed between 1994-5 (R1) and 1997-8 (R2). Survey staff screened adult residents (13 years or older) for visual acuity using laminated Snellen's E optotype cards at each survey. Those who failed (VA >6/18) were evaluated by an ophthalmic clinical officer and an ophthalmologist. Incidence of visual loss (per 1000 person years (PY)) was calculated among those who had normal vision at R1.

RESULTS

2124 people were studied at both survey rounds (60.9% of those screened at R1); 48% were male. Participants in R1 were older (34.7 versus 31.5 years at R2, p<0.001). Visual loss in R2 occurred in 56 (2.8%) of 1997, yielding a crude incidence rate of 9.9, and an age standardised incidence rate of 13.2, per 1000 PY. Incidence of visual loss increased with age from 1.21 per 1000 PY among people aged 13-34 to 64.2 per 1000 PY in those aged 65 years or older (p for trend >0.001). The six commonest causes of visual loss were: cataract, refractive error, macular degeneration, chorioretinitis, glaucoma, and corneal opacity. If similar rates are assumed for the whole of Uganda, it is estimated that 30 348 people would develop bilateral blindness or bilateral visual impairment, per year.

CONCLUSIONS

Cataract and refractive error were the major causes of incident visual loss in south west Uganda. These data are valuable for forecasting and planning eye services.

HIV-1 epidemic trends in rural south-west Uganda over a 10-year period

The objective of this study was to examine the epidemic trends of HIV-1 infection in a rural population cohort in Uganda followed for 10 years. The methods used were to assess incidence and prevalence trends in adults in this longitudinal cohort study. The results showed that incidence of infection has fallen significantly in all adults, and separately in males, females, young adults and older adults over the course of the study period. There was also a reduction in prevalence, especially in young men and women. There was some evidence of a cohort effect in women. The conclusions are that this study provides the first evidence of a falling incidence in a rural general population in Africa. This was an observational cohort exposed to national health education messages, giving hope that similar campaigns elsewhere in Africa could be used effectively in efforts to control the HIV epidemic.

Generalizability of population-based studies on AIDS: a comparison of newly and continuously surveyed villages in rural southwest Uganda

BACKGROUND

Population-based studies are thought to provide generalizable epidemiological data on the human immunodeficiency virus type 1 (HIV-1) epidemic. However, longitudinal studies are susceptible to bias from added attention caused by study activities. We compare HIV-1 prevalence in previously and newly surveyed villages in rural southwest Uganda.

METHODS

The study population resided in 25 neighbouring villages, of which 15 have been surveyed for 10 years. Respondents (>/=13 years) provided socio-demographic and sexual behaviour data and a blood sample for HIV-1 serology in private after informed consent. We tested the independent effect of residency: (1) original versus new villages; (2) proximity to main road; and (3) proximity to trading centre on HIV-1 serostatus of respondents using multivariate logistic regression.

RESULTS

There were 8,990 adults censused, 68.3% were from the original villages, 48.2% were males and 6111 (68.0%) were interviewed and had definite HIV-1 serostatus. The HIV-1 prevalence was 6.1% overall, 5.7% in the new, and 6.4% in the original villages (P = 0.25). Residency in the new or original villages did not independently predict HIV-1 serostatus of respondents (P = 0.46). Independent predictors of HIV-1 serostatus were education (primary or higher, odds ratio [OR] = 1.7 and 1.4, respectively), being separated or widowed OR = 4.2, reported previous use of a condom OR = 1.8, or reported genital ulceration OR = 3.3, and age group 25-34 and 35-44 years OR = 5.8 and OR = 4.8 (all P </= 0.001).

CONCLUSIONS

In the context of rural Uganda where there has been considerable health education about AIDS, the additional attention to HIV infection caused by this longitudinal study does not appear to have appreciably affected the prevalence of HIV-1 infection.

Evaluation of E-optotypes as a screening test and the prevalence and causes of visual loss in a rural population in SW Uganda

BACKGROUND

Few population-based eye surveys have been conducted in sub-Saharan Africa, limiting the quality of epidemiological information on visual loss from Africa. In the present paper, we describe the prevalence of visual loss in rural Uganda and the screening accuracy of E-optotypes when used by non-medical staff.

METHODS

Residents of 15 neighbouring villages were screened for visual loss (<6/18 in either eye) using Snellen's E-optotypes. Individuals who failed were initially referred to an ophthalmic clinical officer (OCO), who retested visual acuity and subsequently referred to an ophthalmologist to determine the cause of visual loss. Subjects from two villages (248 individuals) who passed visual acuity screening were re-examined by the OCO to estimate the accuracy of the screening procedure.

RESULTS

Of the 4076 adults (aged 13 years and over, 69.3% of the censused population) who participated, 191 (4.7%) failed the vision screening criteria and 648 (15.9%) had non-vision impairing conditions. The prevalence of visual loss was at least 3.9%: 0.4% had bilateral blindness, 1.6% had bilateral visual impairment, 0.7% had unilateral blindness and 1.2% unilateral visual impairment. Cataract was the leading cause for all categories of visual loss except bilateral blindness, for which suspected glaucoma was most frequent. Refractive errors were the second leading cause of bilateral and unilateral visual impairment. Based on one subject (0.4%) in the validation sample who was found to have low vision, we estimated the sensitivity and specificity of E-optotypes for detecting visual loss to be 93% and 99%, respectively.

CONCLUSIONS

Cataract and refractive errors were responsible for most of the visual loss in rural Uganda. Snellen's E-optotypes provide a suitable cost-saving tool for conducting population-based eye surveys in sub-Saharan Africa.

Declining HIV-1 incidence and associated prevalence over 10 years in a rural population in south-west Uganda: a cohort study

BACKGROUND

In Uganda, there have been encouraging reports of reductions in HIV-1 prevalence but not in incidence, which is the most reliable measure of epidemic trends. We describe HIV-1 incidence and prevalence trends in a rural population-based cohort between 1989 and 1999.

METHODS

We surveyed the adult population of 15 neighbouring villages for HIV-1 infection using annual censuses, questionnaires, and serological surveys. We report crude annual incidence rates by calendar year and prevalence by survey round.

FINDINGS

6566 HIV-1 seronegative adults were bled two or more times between January, 1990, and December, 1999, contributing 31984 person years at risk (PYAR) and 190 seroconversions. HIV-1 incidence fell from 8.0 to 5.2 per 1000 PYAR between 1990 and 1999 (p=0.002, chi(2) for trend). Significant sex-specific and age-group-specific reductions in incidence were evident. Incidence was 37% lower for 1995-99 than for 1990-94 (p=0.002, t-test). On average, 4642 adult residents had a definite HIV-1 serostatus at each yearly survey round. HIV-1 prevalence fell significantly between the first and tenth annual survey rounds (p=0.03, chi(2) for trend), especially among men aged 20-24 years (6.5% to 2.2%) and 25-29 years (15.2% to 10.9%) and women aged 13-19 years (2.8% to 0.9%) and 20-24 years (19.3% to 10.1%) (all p<0.001, chi(2) for trend).

INTERPRETATION

Our findings of a significant drop in adult HIV-1 incidence in rural Ugandans give hope to AIDS control programmes elsewhere in sub-Saharan Africa where rates of HIV-1 infection remain high.

Alcohol and HIV: a study among sexually active adults in rural southwest Uganda

OBJECTIVE

To investigate the association between alcohol consumption and HIV sero-positivity in a rural Ugandan population.

METHODS

The adult population residing in a cluster of 15 neighbouring villages has been kept under epidemiological surveillance for HIV infection using annual censuses and sero-surveys since 1989. At the eighth annual survey all respondents were asked about their history of alcohol consumption, the sale of alcohol in their household, and other socio-demographic information. After informed consent, blood was drawn for HIV serology.

RESULTS

Of the total adult population 3279 (60%) were interviewed; 48% were males; 905 (27%) had not started sexual activity and were excluded from further analysis. Of the remaining 2374, 8% were HIV infected, 57% had ever drunk alcohol, and 4% lived in households where alcohol was sold. Living in a household where alcohol was sold was associated with a history of having ever drunk alcohol (OR 2.9, 95% CI : 1.7-4.8). HIV prevalence among adults living in households selling alcohol was 15% compared with 8% among those living in households not selling alcohol (OR 2.0, 95% CI : 1.1-3.6). Individuals who had ever drunk alcohol experienced an HIV prevalence twice that of those who had never drunk, 10% versus 5% (OR 2.0, 95% CI : 1.5-2.8). This association remained after adjusting for potential confounders including sale of alcohol in the household and Muslim religion (OR 1.8, 95% CI : 1.2-2.7). Only age, marital status and having ever drunk alcohol independently predicted HIV sero-positivity in a logistic regression model.

CONCLUSIONS

We have demonstrated an association between a history of alcohol consumption and being HIV sero-positive. This unexplored factor may explain in part the observed lower prevalence of HIV infection among Muslims. Public health campaigns need to stress the relationship between HIV and alcohol.