Aiming at malaria elimination in Zanzibar

Sammanfattning: Following the increase of the international funding for implementation of the combined malaria control strategies in the past decade, a significant reduction of malaria attributed morbidity and mortality has been achieved. Yet, malaria is still a severe threat to global health. In 2013, more than 200 million malaria cases causing the death of over 600 000 people were reported. Zanzibar was among the first to implement artemisinin-based combination therapy (ACT) for malaria treatment, strengthened vector control measures including long lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS) as well as rapid diagnostic test (RDT) for malaria diagnosis at peripheral health care facilities. We assessed the effectiveness of malaria control tools and interventions for achieving malaria elimination in Zanzibar by studying the temporal trends of different malariometric indices in two districts of Zanzibar (Micheweni and North A) with a population of approximately 100,000 people each, between 1999 and 2013. Moreover, we conducted a health facility based study in the same districts for evaluation of RDT for malaria diagnosis including its performance within the integrated management of childhood illness (IMCI) algorithm as well as its field applicability as a source of parasite DNA for DNA extraction for molecular surveillance. The interventions, with high sustained community uptake, were associated with major decline in malaria transmission most pronounced from 2004 to 2007, after which there appears to be a steady state. The cross-sectional survey in 2013 revealed a 97.0% reduction of Plasmodium falciparum prevalence when compared to 2003. Health facility data showed 96.0 % reduction of parasitologically confirmed malaria infections. All cause mortality among children under five decreased by 70%. Moreover, the general perception of reduced malaria burden by the caretakers was not associated with reduced adherence to the vector control measures. RDT sensitivity against PCR and blood smear microscopy was relatively low (76.5% and 78.6%, respectively). Adherence to the RDT results was excellent (99.9%) and RDT performed well in the IMCI algorithm with equally high adherence among children under five as compared with other age groups. Further, RDT showed to be a good and reliable source of parasite DNA, useful for malaria case detection, molecular surveillance and RDT quality control. During the conduct of the studies in this thesis, malaria elimination was not achieved in Zanzibar. However, following implementation of effective and sustainable tools and interventions with high coverage and uptake, Zanzibar has reached a state of malaria preelimination. Additional tools and interventions are necessary for further reduction of malaria transmission towards malaria elimination.