75717 DIME BRIEF Eritrea: evaluating the additive effects of indoor residual spraying (IRS) in a low-transmission setting looking to eliminate malaria The Development Background Impact Evaluation Despite significant progress in malaria control on a global scale, Sub-Saharan Africa still Initiative is a broad- bears the brunt of the disease, with over 90% of clinical cases occurring in this region. based World Bank Against this backdrop, Eritrea has long been considered a success story. The country program to generate has made considerable progress in reducing malaria prevalence through a combination knowledge on the of case management, larval habitat management (LHM), wide-scale distribution of free effectiveness of insecticide-treated nets (ITNs), and indoor residual spraying (IRS) in high-prevalence government areas. And yet, elimination appears ever an elusive goal, and malaria remains the programs. It supports leading cause of death in children under five. Given these facts, it is vital to enhance government agencies existing malaria control programs in order to move towards effective elimination. adopt a culture of real time evidence- based policy-making Impact evaluation on the basis of Abundant evidence exists to support individual malaria prevention methods, such as rigorous impact IRS or LHM. When it comes to establishing how effective these interventions are when evaluation. By testing combined, however, data is scarce. This is despite the fact that combining prevention how to make policies strategies has long been advocated as the way forward in eliminating malaria. The aim work, it contributes to of the impact evaluation in Eritrea is to help bridge this information gap. improving policy performance. As countries scale up prevention efforts to eliminate malaria, there is renewed interest in IRS techniques. The study is thus designed to estimate the benefits of introducing IRS DIME works with 300 agencies in 72 over and above the existing intervention package (ITNs, LHM and case management) in countries across 15 Gash Barka, Eritrea. Gash Barka, with near universal ITN coverage under the National thematic programs to Malaria Control Program (NMCP) and relatively low infection rates, still records higher generate knowledge, malaria transmission compared to other malarious areas of the country. improve quality of operations and A two-arm cluster-randomized community-controlled trial was performed in the area strengthen country to establish the additive effects of IRS. A total of 115 villages were randomly assigned to capacity for either treatment or control groups (57 treatment and 58 control villages), with a evidence-based minimum five-kilometer distance separating treatment and control villages to avoid policy- making. contamination. Both groups were already benefiting from standard malaria prevention activities in the region. Between June and July of 2009 households in the treatment This impact evaluation group were additionally sprayed with DDT in accordance with relevant WHO is part of DIME’s guidelines. Data was collected during the period October 6–15, 2009, which Malaria Impact corresponds to the peak of the malaria transmission season. A questionnaire was Evaluation Program. administered to one resident adult in a sample of 1,617 randomly selected households in both treatment and control groups (a total of 7,895 individuals surveyed). Additionally, blood samples were taken from all present household members who gave their informed consent. Results The prevalence of malaria parasite infection in the study area was as low as 0.5% at the end of the peak transmission season in 2009, and the study had no power to detect any differences in prevalence rates between treatment and control villages or between males and females. A marginally significant positive relationship – consistent over all DIME Brief on IRS in Eritrea 1 models – was, however, detected between age and infection; IRS v. ITNs – decision-making with imperfect children under the age of 15 were over twice more likely to be information infected compared to those 15 and older. chart It is believed that public health investments are effective to the extent that they crowd out private The observed low malaria prevalence in the sample can be health initiatives. IRS has frequently been attributed to a number of factors. Most importantly, mosquito discussed in this context with regard to the vectors may have been already suppressed as a result of negative implications it may have for individual ongoing malaria control activities. In other words, it can be bed net use. assumed that the control group may have benefitted from an overall suppression of transmission in this area due to near Interestingly enough, no such effect was observed universal ITN coverage and comprehensive control schemes in within the treatment group in the Eritrea IRS the past. Additionally, since the IRS intervention achieved impact evaluation. If anything, individuals were household coverage above 85%, protection may have been more likely to own and use ITNs, most probably unintentionally conferred on the control group despite the five- due to the fact that the spraying campaign made kilometer geographical buffer. Thus, comprehensive prevention the disease more salient within the community. efforts undertaken in Gash Barka in addition to IRS, combined with a limited sample size, may render any additive effects of Neither did the IRS intervention have any adverse impact on other individual preventive efforts. this method difficult to detect. Quite to the contrary, for example, individuals in the treatment group were found to be more likely Policy recommendations to keep livestock further away from their Eritrea has engaged in a long-term and comprehensive malaria dwellings. control program. Thanks to near universal ITN coverage, These insights may corroborate the hypothesis continued efforts to manage larval habitats, provision of access that, with imperfect information, the implications to prompt and effective treatment, and applying IRS in of the standard ‘crowd-out’ model are reversed. response to epidemic spells, the country may now be poised for Public health interventions in this case need not elimination. necessarily crowd out private health initiatives, but actually reinforce them, as awareness of the The results of the impact evaluation show that even in this problem increases. This finding carries powerful highly conducive environment, age remains an important risk implications for malaria elimination, as it has long factor. Given that the prevalence of malaria parasitaemia in the been acknowledged that combinations of study area was twice as high among younger individuals, individual interventions are most effective in despite overall low infection rates in the general population, achieving this objective. children and young adults may be a good target for further interventions to reduce parasite infection as Eritrea moves towards malaria elimination. Sources: Keating, Joseph; Locatelli, Andrea; Gebremichael, Andemariam; Ghebremeskel, Tewolde; Mufunda, Jacob; Mihreteab, Selam; Berhane, Daniel; Carneiro, Pedro. 2011. "An evaluation of an indoor residual spray campaign for reducing malaria infection prevalence in an intervention suppressed low-transmission setting in Eritrea: results from a household survey." Acta Tropica 119: 107-113. Carneiro, Pedro. (working paper). “Health and Behavioral Impacts of Indoor Residual Spraying in Eritrea.” Carneiro, Pedro; Locatelli, Andrea; Ghebremeskel, Tewolde; Keating, Joseph. (working paper). “Do Public Health Interventions Crowd Out Technician performing IRS Private Health Investments? Malaria Control Policies in Eritrea.” Photo: Bonnie Gillespie For more information on DIME, contact Arianna Legovini (alegovini@worldbank.org) or see www.worldbank.org/dime To contact the author, email Pedro Carneiro (p.carneiro@ucl.ac.uk) DIME Brief on IRS in Eritrea 2