Measuring low and unstable malaria transmission in Ethiopia: strategies for malaria surveillance and epidemic detection


Ashton, RA; (2014) Measuring low and unstable malaria transmission in Ethiopia: strategies for malaria surveillance and epidemic detection. PhD thesis, London School of Hygiene & Tropical Medicine. DOI: 10.17037/PUBS.02025451

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Abstract

In Ethiopia, malaria transmission is seasonal and epidemic-prone, with both Plasmodium falciparum and Plasmodium vivax being endemic. Such spatial and temporal clustering of malaria only serves to underscore the importance of regularly collecting up-to-date malaria surveillance data to inform decision-making in malaria control and improve responsiveness to potential epidemics. This thesis compares indicators and strategies used for the monitoring and surveillance of malaria in Ethiopia. Cross-sectional school-based surveys were conducted throughout Oromia Regional State, generating data on malaria prevalence by microscopy, risk factors for infection and intervention use. Filter paper blood samples collected during these school surveys were subsequently tested to determine exposure to malaria based on presence of anti-Plasmodium antibodies, and Bayesian geostatistical modelling was employed to predict P. falciparum and P. vivax seroprevalence across Oromia. In southern Ethiopia, a schoolbased syndromic surveillance system was piloted, exploring the utility of school absenteeism as a complementary indicator of malaria epidemics at community level. Finally, findings from the school surveys, measured and modelled seroprevalence, as well as data from the national Malaria Indicator Survey in 2011 were compared with spatially congruent estimates of malaria incidence collected from health facilities and to modelled parasite rate from the Malaria Atlas Project. Findings from this thesis demonstrate the limitations of microscopy as a primary indicator of malaria infection in cross-sectional surveys in areas of very low transmission. The work highlights the potential of serological indicators of Plasmodium exposure for inclusion in periodic large-scale malaria monitoring activities and develops a first ever geostatistical risk map based on serological indictors. This was supported by comparative analysis of a range of survey and modelling indicators against estimates of incidence from passive surveillance, indicating the inadequacy of cross-sectional surveys estimating population parasitaemia to reflect the spatial extent and temporal variability of transmission. The piloted syndromic surveillance system indicates that monitoring school absenteeism has potential as a complementary epidemic alert system, operating alongside the existing system at health posts, but is limited by low school enrolment in the piloted setting. The findings of this thesis indicate that existing periodic monitoring strategies and tools are insufficient to fully describe the extent of malaria in settings where Plasmodium transmission is spatially and temporally variable. Modifications to monitoring strategies are recommended, including incorporation of serological indicators and spatial modelling.

Item Type: Thesis
Thesis Type: Doctoral
Thesis Name: PhD
Contributors: Brooker, S (Thesis advisor);
Additional Information: uk.bl.ethos.631579
Faculty and Department: Faculty of Infectious and Tropical Diseases > Dept of Disease Control
Funders: John-Henry Credland Memorial Foundation, United States Agency for International Development Presidents' Malaria Initiative (cooperative agreement 663-A-00-09-00404-00)
Copyright Holders: Ruth Anne Ashton
URI: http://researchonline.lshtm.ac.uk/id/eprint/2025451

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