23Large-scale surveillance of mosquito populations is crucial to assess the intensity of vector-borne 24 disease transmission and the impact of control interventions. However, there is a lack of accurate, cost-25 effective and high-throughput tools for mass-screening of vectors. This study demonstrates proof-of-26 concept that near-infrared spectroscopy (NIRS) is capable of rapidly identifying laboratory strains of 27 human malaria infection in African mosquito vectors. By using partial least square regression models 28 based on malaria-infected and uninfected Anopheles gambiae mosquitoes, we showed that NIRS can 29 detect oocyst-and sporozoite-stage Plasmodium falciparum infections with 88% and 95% accuracy, 30 respectively. Accurate, low-cost, reagent-free screening of mosquito populations enabled by NIRS 31 could revolutionize surveillance and elimination strategies for the most important human malaria 32 parasite in its primary African vector species. Further research is needed to evaluate how the method 33 performs in the field following adjustments in the training datasets to include data from wild-caught 34 infected and uninfected mosquitoes. 35 36 Introduction 37 Malaria is holding back development in endemic countries and remains one of the leading causes of 38 death in children under 5 years-old in sub-Saharan Africa [1-3]. During the past decade, the large-scale 39 roll-out of long-lasting insecticide treated nets and indoor residual spraying across Africa has resulted in 40 a substantial reduction in malaria cases [4]. The WHO's Global Technical Strategy for Malaria 2016-41 2030 seeks to reduce malaria incidence and related mortality by at least 90% and to eliminate the 42 disease in a minimum of 35 countries [1]. These bold goals will require new interventions that can 43 address residual malaria transmission as well as new tools to better monitor their impact on vector-44 borne disease transmission. Mosquito surveillance is a cornerstone of the control of malaria and other 45vector-borne diseases [5]. However, presently, there is no high-throughput, cost-efficient method to 46 identify Plasmodium infection and infectiousness in mosquitoes. Molecular methods such as ELISA and
47PCR are used to determine parasite infection, but these are expensive and laborious [6][7][8], challenging 48 resource-poor countries with few funds and limited access to reagents and equipment, and thus are 49 unsuitable for large-scale surveillance. A further complication is that typically only 1-2% of mosquitoes 50 may be infected with transmission stage parasites (sporozoites), meaning that very large sample sizes 51 must be tested to accurately quantify site and time-specific estimates of mosquito infection rates as will 52 be required to assess progress towards malaria elimination [9].
54Recent advances indicate several mosquito traits can be accurately identified through analysis of their 55 tissues with near infrared spectroscopy (NIRS) [10][11][12][13] . Here, visible and NIR light (wavelength 400-56 2500 nanometers) ...