Spatial analysis of malaria incidence at the village level in areas with unstable transmission in Ethiopia.

BACKGROUND: Malaria is the leading cause of morbidity and mortality in Ethiopia, accounting for over five million cases and thousands of deaths annually. The risks of morbidity and mortality associated with malaria are characterized by spatial and temporal variation across the country. This study examines the spatial and temporal patterns of malaria transmission at the local level and implements a risk mapping tool to aid in monitoring and disease control activities. METHODS: In this study, we examine the global and local patterns of malaria distribution in 543 villages in East Shoa, central Ethiopia using individual-level morbidity data collected from six laboratory and treatment centers between September 2002 and August 2006. RESULTS: Statistical analysis of malaria incidence by sex, age, and village through time reveal the presence of significant spatio-temporal variations. Poisson regression analysis shows a decrease in malaria incidence with increasing age. A significant difference in the malaria incidence density ratio (IDRs) is detected in males but not in females. A significant decrease in the malaria IDRs with increasing age is captured by a quadratic model. Local spatial statistics reveals clustering or hot spots within a 5 and 10 km distance of most villages in the study area. In addition, there are temporal variations in malaria incidence. CONCLUSION: Malaria incidence varies according to gender and age, with males age 5 and above showing a statistically higher incidence. Significant local clustering of malaria incidence occurs between pairs of villages within 1-10 km distance lags. Malaria incidence was higher in 2002-2003 than in other periods of observation. Malaria hot spots are displayed as risk maps that are useful for monitoring and spatial targeting of prevention and control measures against the disease.

Individual, household and environmental risk factors for malaria infection in Amhara, Oromia and SNNP regions of Ethiopia.

We assessed malaria infection in relation to age, altitude, rainfall, socio-economic factors and coverage of control measures in a representative sample of 11437 people in Amhara, Oromia and SNNP regions of Ethiopia in December 2006-January 2007. Surveys were conducted in 224 randomly selected clusters of 25 households (overall sample of 27884 people in 5708 households). In 11538 blood slides examined from alternate households (83% of those eligible), malaria prevalence in people of all ages was 4.1% (95% CI 3.4-4.9), with 56.5% of infections being Plasmodium falciparum. At least one mosquito net or one long-lasting insecticidal net (LLIN) was present in 37.0% (95% CI 31.1-43.3) and 19.6% (95% CI 15.5-24.5) of households, respectively. In multivariate analysis (n=11437; 82% of those eligible), significant protective factors were: number of LLINs per household (odds ratio [OR] (per additional net)=0.60; 95% CI 0.40-0.89), living at higher altitude (OR (per 100 m)=0.95; 95% CI 0.90-1.00) and household wealth (OR (per unit increase in asset index)=0.79; 95% CI 0.66-0.94). Malaria prevalence was positively associated with peak monthly rainfall in the year before the survey (OR (per additional 10 mm rain)=1.10; 95% CI 1.03-1.18). People living above 2000 m and people of all ages are still at significant risk of malaria infection.

Potential for integrated control of neglected tropical diseases in Ethiopia.

Ethiopia is one of the poorest and least developed countries in the world, endemic for many neglected tropical diseases (NTDs). The Ministry of Health is successfully controlling onchocerciasis through community-directed treatment with ivermectin and has implemented health system changes that would allow extension of integrated NTD control to schistosomiasis, lymphatic filariasis, soil-transmitted helminthiasis and trachoma. Funds are now needed to gain a better understanding of the endemicity and co-endemicity of these diseases and to formulate and pilot integrated packages for mass drug administration (MDA). Based on the experience gained, MDA may then be scaled-up to all NTD-endemic areas.

Burden of malaria during pregnancy in areas of stable and unstable transmission in Ethiopia during a nonepidemic year.

Little is known about the epidemiology of malaria during pregnancy in areas of unstable (epidemic-prone) transmission (UT) in sub-Saharan Africa. In cross-sectional studies, peripheral malaria parasitemia was identified in 10.4% of women attending antenatal care clinics at 1 stable transmission (ST) site and in 1.8% of women at 3 UT sites; parasitemia was associated with anemia in both ST (relative risk [RR], 2.0; P<.001) and UT (RR, 4.4; P<.001) sites. Placental parasitemia was identified more frequently during deliveries at ST sites (12/185; 6.5%) than at UT sites (21/833; 2.5%; P=.006). Placental parasitemia was associated with low birth weight at the ST site (RR, 3.2; P=.01) and prematurity at ST (RR, 2.7; P=.04) and UT (RR, 3.9; P=.01) sites and with a 7-fold increased risk of stillbirths at UT sites. The effectiveness and efficiency in Ethiopia of standard preventive strategies used in high-transmission regions (such as intermittent preventive treatment) may require further evaluation; approaches such as insecticide-treated bednets and epidemic preparedness may be needed to prevent adverse pregnancy outcomes.