Fig. 1: Plasmodium falciparum salivary gland sporozoite load correlates significantly with sporozoite inoculum size.

a Schematic of the experimental procedure showing the single mosquito bite set-up followed by the isolation of mosquito salivary glands and mouse ear, and qPCR quantification of sporozoites in these tissues. b The sporozoite inoculum positively correlates with mosquito salivary gland sporozoite load: Spearman correlation ρ = 0.66, 95% confidence interval 0.55–0.75; P < 0.0001 (two-tailed). Each dot represents data from a single mosquito-mouse pair (n = 126 from 20 independent experiments). c Representative image of CSP-stained sporozoites (green) at a single mosquito bite site from 10 single mosquito bite sites. Left panel is a snapshot of the entire ear with the location of sites at which sporozoites were found delineated by circles. Right panels show zoomed in images of sporozoites at each site. Scale bars: 50 µm. d Inoculum size was binned as indicated. Mosquitoes in each bin were classified according to the salivary gland sporozoite load (filled bars >10,000 salivary gland sporozoites and striped bars <10,000 salivary gland sporozoites). Significant differences in inoculum size were observed between mosquitoes with >10,000 and <10,000 salivary gland sporozoites (one-sided χ², P < 0.0001). e Transmission efficiency: The percentage of salivary gland sporozoites injected during probing (inoculum/inoculum plus residual salivary gland sporozoites) was calculated for each mosquito-mouse pair and then binned as indicated. Mosquitoes in each bin were classified according to their salivary gland sporozoite loads (filled bars >10,000 sporozoites and striped bars <10,000 sporozoites). Significant differences in transmission efficiency were observed between mosquitoes with >10,000 salivary gland sporozoites compared to those with <10,000 sporozoites (one-sided χ², P < 0.0001). SG Spz salivary gland sporozoites.