Karen H Witten

Incidence of malaria among children living near dams in northern Ethiopia: community based incidence survey

Abstract Objective: To assess the impact of construction of microdams on the incidence of malaria in nearby communities in terms of possibly increasing peak incidence and prolonging transmission. Design: Four quarterly cycles of malaria incidence surveys, each taking 30 days, undertaken in eight at risk communities close to dams paired with eight control villages at similar altitudes but beyond flight range of mosquitoes. Setting: Tigray region in northern Ethiopia at altitudes of 1800 to 2225 m. Subjects: About 7000 children under 10 years living in villages within 3 km of microdams and in control villages 8-10 km distant. Main outcome measures: Incidence of malaria in both communities. Results: Overall incidence of malaria for the villages close to dams was 14.0 episodes/1000 child months at risk compared with 1.9 in the control villages—a sevenfold ratio. Incidence was significantly higher in both communities at altitudes below 1900 m. Conclusions: There is a need for attention to be given to health issues in the implementation of ecological and environmental development programmes, specifically for appropriate malaria control measures to counteract the increased risks near these dams. Key messages Environmental development may have important effects on the epidemiology of vector borne diseases such as malaria This may be particularly important where disease transmission is unstable—for example, in highland areas Children in villages near recently constructed microdams in northern Ethiopia had a significantly increased risk of malaria It seems that this irrigation development programme is leading to increased malaria transmission across a range of altitudes and seasons Intersectoral collaboration is necessary in development projects that may affect communities both positively and negatively

Household risk factors for malaria among children in the Ethiopian highlands

Malaria transmission varies from village to village and even from family to family in the same village. The current study was conducted in northern Ethiopia to identify risk factors responsible for such variations in a hypoendemic highland malaria setting: 2114 children aged < 10 years living in 6 villages situated close to small dams at altitudes from 1775 to 2175 m were monitored. Monthly malaria incidence was determined 4 times over a 1-year period during 1997. Incidence results were then analysed by 14 individual and household factors using Poisson multivariate regression. Among 14 factors analysed, use of irrigated land (rate ratio[RR] = 2.68, 95% CI 1.64-4.38), earth roof (RR = 2.15, 95% CI 1.31-3.52), animals sleeping in the house (RR = 1.92, 95% CI 1.29-2.85), windows (RR = 1.84, 95% CI 1.30-2.63), open eaves (RR = 1.85, 95% CI 1.19-2.88), no separate kitchen (RR = 1.57, 95% CI 1.10-2.23), and 1 sleeping room (RR = 1.52, 95% CI 1.05-2.20), were significantly associated with malaria. The proportion of infection among children exposed to one or no risk factor was 2.1%, increasing with the number of risk factors and reaching 29.4% with 5 or more. Further studies are needed to confirm the importance of particular risk factors, possibly leading to simple health education and control measures that could become part of routine control programmes, implemented with inter-sectoral collaboration.

Can source reduction of mosquito larval habitat reduce malaria transmission in Tigray, Ethiopia?

The development of irrigation schemes by dam construction has led to an increased risk of malaria in Tigray, Ethiopia. We carried out a pilot study near a microdam to assess whether environmental management could reduce malaria transmission by Anopheles arabiensis, the main vector in Ethiopia. The study took place in Deba village, close to a dam; Maisheru village, situated 3–4 km away from the dam, acted as a control. Baseline entomological and clinical data were collected in both villages during the first 12 months. Source reduction, involving filling, draining and shading of potential mosquito‐breeding habitats was carried out by the community of Deba in the second year and routine surveillance continued in both villages during the second year. Anopheles arabiensis was highly anthropophilic (Human Blood Index = 0.73), biting early in the night before people went to bed. The major breeding habitats associated with the dam were areas of seepage at the dam base (28%), leaking irrigation canals (16%), pools that formed along the bed of streams from the dam (13%), and man‐made pools (12%). In the pre‐intervention year, 5.9–7.2 times more adult vectors were found in the dam village compared with the control village. There was a 3.1% higher prevalence of an enlarged spleen in children under 10 years in the dam village than in the control village during the pre‐intervention period, but no statistically significant difference was found in the incidence of falciparum malaria between the two villages during the same period. Source reduction was associated with a 49% (95% CI = 46.6–50.0) relative reduction in An. arabiensis adults in the dam village compared with the pre‐intervention period. There were very few cases of malaria during the intervention period in both villages making it impossible to judge whether malaria incidence had been reduced. These preliminary findings suggest that in areas of low intensity transmission community‐led larval control may be a cheap and effective method of controlling malaria. Further, large‐scale studies are needed to confirm these findings.

Revealing the burden of maternal mortality: a probabilistic model for determining pregnancy-related causes of death from verbal autopsies

BackgroundSubstantial reductions in maternal mortality are called for in Millennium Development Goal 5 (MDG-5), thus assuming that maternal mortality is measurable. A key difficulty is attributing causes of death for the many women who die unaided in developing countries. Verbal autopsy (VA) can elicit circumstances of death, but data need to be interpreted reliably and consistently to serve as global indicators. Recent developments in probabilistic modelling of VA interpretation are adapted and assessed here for the specific circumstances of pregnancy-related death.MethodsA preliminary version of the InterVA-M probabilistic VA interpretation model was developed and refined with adult female VA data from several sources, and then assessed against 258 additional VA interviews from Burkina Faso. Likely causes of death produced by the model were compared with causes previously determined by local physicians. Distinction was made between free-text and closed-question data in the VA interviews, to assess the added value of free-text material on the models output.ResultsFollowing rationalisation between the model and physician interpretations, cause-specific mortality fractions were broadly similar. Case-by-case agreement between the model and any of the reviewing physicians reached approximately 60%, rising to approximately 80% when cases with a discrepancy were reviewed by an additional physician. Cardiovascular disease and malaria showed the largest differences between the methods, and the attribution of infections related to pregnancy also varied. The model estimated 30% of deaths to be pregnancy-related, of which half were due to direct causes. Data derived from free-text made no appreciable difference.ConclusionInterVA-M represents a potentially valuable new tool for measuring maternal mortality in an efficient, consistent and standardised way. Further development, refinement and validation are planned. It could become a routine tool in research and service settings where levels and changes in pregnancy-related deaths need to be measured, for example in assessing progress towards MDG-5.

Professional assistance during birth and maternal mortality in two Indonesian districts

OBJECTIVE To examine determinants of maternal mortality and assess the effect of programmes aimed at increasing the number of births attended by health professionals in two districts in West Java, Indonesia. METHODS We used informant networks to characterize all maternal deaths, and a capture-recapture method to estimate the total number of maternal deaths. Through a survey of recent births we counted all midwives practising in the two study districts. We used case-control analysis to examine determinants of maternal mortality, and cohort analysis to estimate overall maternal mortality ratios. FINDINGS The overall maternal mortality ratio was 435 per 100,000 live births (95% confidence interval, CI: 376-498). Only 33% of women gave birth with assistance from a health professional, and among them, mortality was extremely high for those in the lowest wealth quartile range (2303 per 100,000) and remained very high for those in the lower middle and upper middle quartile ranges (1218 and 778 per 100,000, respectively). This is perhaps because the women, especially poor ones, may have sought help only once a serious complication had arisen. CONCLUSION Achieving equitable coverage of all births by health professionals is still a distant goal in Indonesia, but even among women who receive professional care, maternal mortality ratios remain surprisingly high. This may reflect the limitations of home-based care. Phased introduction of fee exemption and transport incentives to enable all women to access skilled delivery care in health centres and emergency care in hospitals may be a feasible, sustainable way to reduce Indonesias maternal mortality ratio.

Schistosome transmission, water-resource development and altitude in northern Ethiopia

Abstract Schistosomiasis continues to be a major public-health problem, not least in association with water-resource developments. The impact of microdam construction in the northern Ethiopian highlands, in relation to possible increased risks of Schistosoma mansoni infection, has now been assessed. The results of incidence studies, carried out on 473 individuals sampled across eight microdam sites at altitudes of 1800-2225m above sea level, indicated an overall annual incidence of 0.20 infections/person at risk. A multivariate Poisson regression model showed altitude and sex to be significant risk factors for infection, whereas proximity to a microdam was not significant, except possibly at very high altitudes. It was concluded that altitude was the major factor in this environment and that therefore, at least in terms of public-health planning, microdams should be sited as high as local geography permits.