Impact of Environmental Modifications on Malaria in Africa

Chronic hunger, food insecurity and famine continue to affect millions of residents of sub-Saharan Africa. Most people in African countries depend on rain-fed agriculture, making these populations vulnerable to drought and famine. Construction of dams and initiating rural irrigation schemes has been widely recognized as key solutions to food security and economic growth in drought prone regions. In the past decade, sub-Saharan African countries have experienced a new era of large dam constructions and expansion of irrigated agricultural farms. These environmental changes may have unforeseen ecologic consequences that adversely affect human health. However, to date there has been limited basic or translational research to evaluate the impact of water resource development and shifting agricultural practices on malaria ecosystems and attendant changes in the epidemiology, transmission, and pathogenesis of malaria. To address the major knowledge gaps and challenges in malaria control and elimination in the face of drastic environmental modifications in sub-Saharan Africa, this NIH U19 project will assess the impact of human-induced environmental modifications due to dam construction, irrigation and shifting agricultural practices on the epidemiology, transmission, pathogenesis and immunology of Plasmodium falciparum and P. vivax malaria in highly populated Kenya and Ethiopia where major investments in water resource development projects are taking place.

In the past decade, massive scale-up of insecticide-treated nets (ITN) and indoor residual spraying (IRS), together with the introduction of artemisinin-combination treatments, have led to substantial reductions in malaria prevalence and incidence in African highlands. However, rising insecticide resistance and increased outdoor transmission have greatly hampered the effectiveness of ITN and IRS because the current indoor-based interventions do not target the outdoor-biting mosquitoes. Consequently, most highland sites maintain sustained low- level transmission while some others have recently experienced resurgence in malaria rates. Therefore, new supplemental interventions that can tackle outdoor transmission and pyrethroid insecticide resistance are urgently needed. The central objective of this NIH R01 project is to determine the efficacy and cost-effectiveness of EPA-approved long-lasting microbial larvicides in reducing malaria transmission and clinical malaria incidence in western Kenya highlands. Through comprehensive evaluation of potentially cost-effective long-lasting microbial larvicides, this project will provide critically needed data on whether long-lasting microbial larvicides can be scaled up as a supplemental malaria control tool to further reduce malaria incidence in African highlands.

Molecular Epidemiology of vivax Malaria in Ethiopia

Vivax malaria is the most geographically widespread human malaria, causing tremendous suffering and major negative effects on economic productivity. People with African ancestry are thought to be protected from Plasmodium vivax infection because their lack of Duffy antigen expression on the surface of the erythrocytes renders P. vivax unable to invade the erythrocytes. However, recent studies reported sporadic vivax infections in Duffy negative human in a number of African countries. However, the epidemiological significance of vivax infection in Duffy-negative individuals is unknown. We examine the molecular epidemiology and population genetics of P. vivax in a vivax endemic area in Ethiopia.

Malaria in Southeast Asia

Malaria in the Greater Mekong Subregion of Southeast Asia remains an important public health problem. There is immense spatial heterogeneity in malaria distribution, with Myanmar having the highest regional malaria burden. Highly mobile populations crossing porous international borders are a major contributor to parasite introduction and continued transmission. The recent emergence of resistance to the artemisinin (ART) family of drugs as well as to their partner drugs raised global concerns. The vectorial system is highly diverse, and increased outdoor biting and development of insecticide resistance have rendered the two core vector control interventions – insecticide-treated nets and indoor residue spray less effective. Furthermore, falsified and substandard ART-based combination therapies (ACTs) have become a global crisis. Therefore, the central goal of this NIH U19 project led by Dr. Liwang Cui of University of South Florida is to improve the understanding of how mobile human populations, parasite drug resistance, and mosquito biology at international borders so that innovative control strategies can be developed to propel the course of regional malaria elimination. My laboratory collaborates with Dr. Cui on the vector biology subproject.