Tewolde Ghebremeskel

Rolling out insecticide treated nets in Eritrea: examining the determinants of possession and use in malarious zones during the rainy season.

Objective  This paper describes determinants of insecticide treated net (ITN) ownership and use in malarious areas of Eritrea. With ITN distribution and re‐treatment now free for all living in these areas, we examine barriers (other than cost) to access and use of ITNs. We explore the differences between use of an ITN as a proportion of all households in the survey (the roll back malaria indicator), and use of an ITN as a proportion of those households who already own an ITN.

Larval Habitat Diversity and Ecology of Anopheline Larvae in Eritrea

Abstract Studies on the spatial distribution of anopheline mosquito larvae were conducted in 302 villages over two transmission seasons in Eritrea. Additional longitudinal studies were also conducted at eight villages over a 24-mo period to determine the seasonal variation in anopheline larval densities. Eight anopheline species were identified with Anopheles arabiensis predominating in most of the habitats. Other species collected included: An. cinereus, An. pretoriensis, An. d’thali, An. funestus, An. squamosus, An. adenensis, and An. demeilloni. An. arabiensis was found in five of the six aquatic habitats found positive for anopheline larvae during the survey. Anopheles larvae were sampled predominantly from stream edges and streambed pools, with samples from this habitat type representing 91.2% (n = 9481) of the total anopheline larval collection in the spatial distribution survey. Other important anopheline habitats included rain pools, ponds, dams, swamps, and drainage channels at communal water supply points. Anopheline larvae were abundant in habitats that were shallow, slow flowing and had clear water. The presence of vegetation, intensity of shade, and permanence of aquatic habitats were not significant determinants of larval distribution and abundance. Larval density was positively correlated with water temperature. Larval abundance increased during the wet season and decreased in the dry season but the timing of peak densities was variable among habitat types and zones. Anopheline larvae were collected all year round with the dry season larval production restricted mainly to artificial aquatic habitats such as drainage channels at communal water supply points. This study provides important information on seasonal patterns of anopheline larval production and larval habitat diversity on a countrywide scale that will be useful in guiding larval control operations in Eritrea.

Effectiveness of malaria control during changing climate conditions in Eritrea, 1998-2003.

Objective  To assess the effectiveness of impregnated mosquito nets, indoor residual spraying and larval control relative to the impacts of climate variability in the decline of malaria cases in Eritrea.

Interpreting household survey data intended to measure insecticide-treated bednet coverage: results from two surveys in Eritrea

BackgroundAs efforts are currently underway to roll-out insecticide-treated bednets (ITNs) to populations within malarious areas in Africa, there is an unprecedented need for data to measure the effectiveness of such programmes in terms of population coverage. This paper examines methodological issues to using household surveys to measure core Roll Back Malaria coverage indicators of ITN possession and use.MethodsITN coverage estimates within Anseba and Gash Barka Provinces from the 2002 Eritrean Demographic and Health Survey, implemented just prior to a large-scale ITN distribution programme, are compared to estimates from the same area from a sub-national Bednet Survey implemented 18 months later in 2003 after the roll-out of the ITN programme.ResultsMeasures of bednet possession were dramatically higher in 2003 compared to 2002. In 2003, 82.2% (95% confidence interval (CI) 77.4–87.0) of households in Anseba and Gash Barka possessed at least one ITN. RBM coverage indicators for ITN use were also dramatically higher in 2003 as compared to 2002, with 76.1% (95% CI 69.9–82.2) of children under five years old and 52.4% (95% CI 38.2–66.6) of pregnant women sleeping under ITNs. The ITN distribution programme resulted in a gross increase in ITN use among children and pregnant women of 68.3% and 48% respectively.ConclusionEritrea has exceeded the Abuja targets of 60% coverage for ITN household possession and use among children under five years old within two malarious provinces. Results point to several important potential sources of bias that must be considered when interpreting data for ITN coverage over time, including: disparate survey universes and target populations that may include non-malarious areas; poor date recall of bednet procurement and treatment; and differences in timing of surveys with respect to malaria season.

Costs and cost-effectiveness of vector control in Eritrea using insecticide-treated bed nets

BackgroundWhile insecticide-treated nets (ITNs) are a recognized effective method for preventing malaria, there has been an extensive debate in recent years about the best large-scale implementation strategy. Implementation costs and cost-effectiveness are important elements to consider when planning ITN programmes, but so far little information on these aspects is available from national programmes.MethodsThis study uses a standardized methodology, as part of a larger comparative study, to collect cost data and cost-effectiveness estimates from a large programme providing ITNs at the community level and ante-natal care facilities in Eritrea. This is a unique model of ITN implementation fully integrated into the public health system.ResultsBase case analysis results indicated that the average annual cost of ITN delivery (2005 USD 3.98) was very attractive when compared with past ITN delivery studies at different scales. Financing was largely from donor sources though the Eritrean government and net users also contributed funding. The interventions cost-effectiveness was in a highly attractive range for sub-Saharan Africa. The cost per DALY averted was USD 13 – 44. The cost per death averted was USD 438–1449. Distribution of nets coincided with significant increases in coverage and usage of nets nationwide, approaching or exceeding international targets in some areas.ConclusionITNs can be cost-effectively delivered at a large scale in sub-Saharan Africa through a distribution system that is highly integrated into the health system. Operating and sustaining such a system still requires strong donor funding and support as well as a functional and extensive system of health facilities and community health workers already in place.

Malaria environmental risk assessment in Eritrea

Agroclimactic data and growing degree day-water balance spatial analysis were used to describe potential risk of malaria based on climate suitability for the Plasmodium falciparum-Anopheles arabiensis (Patton) system in Eritrea. A model based on monthly accumulation of the product of two climate gradients, growing degree days (mean temperature-16/spl deg/C base temperature) and the ratio of monthly rain/potential evapotranspiration (R/PET) was most significantly correlated with infection prevalence data from a 2000-2001 survey of malaria at 173 sites in Eritrea. Results indicate: 1) optimum conditions for malaria transmission occur at sites with moderate temperatures (20-30/spl deg/C) and 6-11 potential malaria generations per year during months in which soil moisture exceeds a threshold of 20% of holding capacity, 2) additional consideration of a hydrologic gradient (R/PET), with thermal factors, most accurately reflected field malaria risk, 3) there is a need to systematically account for heat stress at high temperatures that result in decreasing suitability for propagation and transmission of malaria, and 4) marked differences in seasonality of transmission pattern found in Eritrea can be predicted, using growing degree day-water balance models. As a regional-scale component of more comprehensive risk assessment methods, the climate-based models developed ay enable future near real-time disease prediction and intervention by health system managers.