EVALUATING A REACTIVE TEST-AND-TREAT PROGRAM FOR SUB-PATENT MALARIA IN MACHA, ZAMBIA: OPTIMAL STRATEGIES TO ACHIEVE ELIMINATION
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Background: In Choma District, Southern Province, Zambia, malaria prevalence by rapid diagnostic test (RDT) declined from 8% in 2008 to 1% in 2013. As part of an effort to achieve elimination, the Zambian government implemented a reactive test-and-treat (RTAT) program in parts of Southern Province in 2013. Individuals with confirmed malaria by health workers are followed-up within two weeks of diagnosis. All individuals living in households within 140 meters of the index case are tested with an RDT and treated if positive. This study aimed to optimize the RTAT strategy by characterizing infected individuals missed by both the RDT and the current screening radius. Methods: Health workers notified the study team of individuals with RDT confirmed malaria. For each study participant, a questionnaire was administered and a blood sample collected. To evaluate the optimal RTAT radius and assess the frequency of sub-patent, RDT negative infections, the radius was expanded to 250 meters and testing of dried blood spot samples by real-time polymerase chain reaction (PCR) was introduced. Spatial-temporal cluster detection was conducted to identify clusters of index households. Results: From January 2015 to January 2016, 101 index cases were followed-up through the RTAT program. 2504 individuals residing in 394 households were screened. Excluding index cases, parasite prevalence was 2.5% by PCR (53 of 2225) and 1.2% by RDT (26 of 2108). 66% of PCR positive individuals tested negative by RDT. 24 households had a PCR+/RDT- individual. Nearly half of those infected resided within the index case household. No clustering of index house was identified. Conclusion: The low number of secondary cases indicates a low efficiency of RTAT beyond the index case household in this setting, and the sensitivity of the RDT was too low to be an effective screening tool. Focal drug administration in which all individuals within index case households are treated may be a more efficient approach to achieving malaria elimination in southern Zambia.