Scientific Findings of the Southern and Central Africa International Center of Excellence for Malaria Research: Ten Years of Malaria Control Impact Assessments in Hypo-, Meso-, and Holoendemic Transmission Zones in Zambia and Zimbabwe

Abstract

ABSTRACT. For a decade, the Southern and Central Africa International Center of Excellence for Malaria Research has operated with local partners across study sites in Zambia and Zimbabwe that range from hypo- to holoendemic and vary ecologically and entomologically. The burden of malaria and the impact of control measures were assessed in longitudinal cohorts, cross-sectional surveys, passive and reactive case detection, and other observational designs that incorporated multidisciplinary scientific approaches: classical epidemiology, geospatial science, serosurveillance, parasite and mosquito genetics, and vector bionomics. Findings to date have helped elaborate the patterns and possible causes of sustained low-to-moderate transmission in southern Zambia and eastern Zimbabwe and recalcitrant high transmission and fatality in northern Zambia. Cryptic and novel mosquito vectors, asymptomatic parasite reservoirs in older children, residual parasitemia and gametocytemia after treatment, indoor residual spraying timed dyssynchronously to vector abundance, and stockouts of essential malaria commodities, all in the context of intractable rural poverty, appear to explain the persistent malaria burden despite current interventions. Ongoing studies of high-resolution transmission chains, parasite population structures, long-term malaria periodicity, and molecular entomology are further helping to lay new avenues for malaria control in southern and central Africa and similar settings.

Genomics reveals heterogeneousPlasmodium falciparumtransmission and population differentiation in Zambia and bordering countries

“…Mixed infections, also known as multiplicity of infections (MOI), are indicative of intense local exposure rates and correlate with estimates of malaria prevalence within Africa 44,45 and can range from one (monogenomic infection) in low transmission settings to MOI >10 (polygenomic infection) in high transmission settings 46 . Comprising 77% of all sequenced samples, polygenomic infections ( Fws < 0.95) dominated across Zambia, suggesting that malaria transmission remains high across the country with superinfections and co-transmission also likely to be high, even though malaria incidence has decreased since 2011 47 . Although there was limited heterogeneity of polygenomic infection rates at the provincial level ( Figure 1B ), we found a positive correlation between the prevalence of polygenomic infections and parasite prevalence at the sampling cluster level ( Figure 1C ).…”

Genomics reveals heterogeneous Plasmodium falciparum transmission and selection signals in Zambia

“…Mixed infections, also known as multiplicity of infections (MOI), are indicative of intense local exposure rates and correlate with estimates of malaria prevalence within Africa 67 , 68 and can range from one (monogenomic infection) in low transmission settings to MOI > 10 (polygenomic infection) in high transmission settings 69 . Comprising 77% of all sequenced samples, polygenomic infections ( Fws < 0.95) dominated across Zambia, suggesting that malaria transmission remains high across the country with superinfections and co-transmission also likely to be high, even though malaria incidence has decreased since 2011 70 . Although there was limited heterogeneity of polygenomic infection rates at the provincial level (Fig.…”

Advances in the genetic characterization of the malaria vector, Anopheles funestus, and implications for improved surveillance and control

“…Contrastingly, in southern African countries, An. funestus populations remain susceptible to DDT insecticides [ 101 , 102 ]. This demonstrates how diverse the genes involved in metabolic resistance across the continent are with CYP6P9a/b having a continental distribution.…”