What measures of malaria do we need to monitor elimination?

1. What measures of malaria do we need to monitor elimination? Chris Drakeley

2. The Spectrum of Malaria Infection Infectious bite Biological parameters for assessing transmission intensity Infection Clinical malaria Less Common events: identified via health facilities or DSS Severe malaria Death (Greenwood et al. Parasitology Today 1992;7,277.)

3. (Guerra et al Plos Med 2008)

4. Entomological monitoring Requires long term, regular monitoring Sampling needs to be increasingly intense as the number of mosquitoes (and infected mosquitoes) decreases.

5. Mosquito human dynamics Routine entomology remains key for monitoring changes in vector behaviour What species are they? Do mosquitoes bite earlier? Do they bite outside? Are they resistant to insecticide? (Killeen et al BMC ID 2006)

6. Measuring parasites The gold standard measure Allows detection and enumeration of parasites Allows speciation and identification of potentially infectious individuals

7. Limitations of microscopy This method is limited by how much of a blood film can be read……. Ideally we need to identify all those infected (& infectious) RDT have similar sensitivity to microscopy

8. Progress with molecular methods • Two new methods the LAMP (above) • & NALFIA have 5 fold better sensitivity • that microscopy or RDT. • Species, density and gametocytes remain issues

9. Serological alternatives • Detecting anti malarial antibodies in the blood of people who have been exposed to malaria is another approach • Antibodies last for a long time and represent cumulative exposure to malaria • Cheap, easy and high through-put • Modern techniques are sensitive and specific

10. Data from the Thai-Cambodia boarder Increased sensitivity of serology to allows Identification of potential foci of infection for the control of drug resistance Identification of transmission sites:regional level Cook et al unpublished Blue bars –parasite prevalence , purple bars -sero prevalence

11. Identification of transmission sites:village level Data from Kenya showing that individuals closer to mosquito breeding sites have more antibodies or malaria exposure. Malaria transmission remains heterogenous and Identification and targeting high transmission foci within a village will be key. Wilson et al BMC ID 2006

12. Monitoring progress of the elimination effort Historical precedents for serological evaluation of malaria eradication attempts -Mauritius -Greece Antibodies to detect changes in exposure to both P.falciparum and P.vivax.

15. When & how to measure? • Monitoring will require a combination of approaches • Rapid situational assessments to identify key areas leading to • Detailed surveys (MIS) for risk factor analysis • Sentinel site monitoring for vector studies and parasite and vector resistance

16. Biological tools for the eradication toolbox • Use of existing tools to monitor entomological, parasitological and serological changes. • Technological developments to increase the sensitivity • Develop appropriate sampling frames for representative sample collection