Fig. 1

a Membrane and mouse feeding of Aedes albopictus with different titres of CHIKV. Mosquitoes were fed via artificial membrane with ovine blood containing different titres of CHIKV; the membrane blood meal titres represent the mean (and standard deviation, SD) of before and after feeding titres (i.e. the mean and SD of 2 titre determinations; 30 blood-fed mosquitoes were examined for each CHIKV blood meal titre; limit of detection 2 log₁₀CCID₅₀/ml). A different batch of mosquitoes were fed on CHIKV infected mice on day 2 post-infection; 2 groups of three mice were inoculated with 2 × 10² or 2 × 10⁴ log₁₀CCID₅₀/ml CHIKV, with n = 49/50 fed mosquitoes for each group. The mouse blood meal titres represent the mean (and SD) viraemia on day 2 (n = 3) for each group. b CHIKV titres in the mosquitoes. The CHIKV titers of all CHIKV positive mosquitoes from a are shown; blue lines represent means for each blood meal titre. No CHIKV was detected in any mosquitoes fed with a blood meal titre of 4.75 log₁₀CCID₅₀/ml. Whole mosquitoes were homogenized in 0.5 ml of medium and titres determined by standard CCID₅₀ assays. For membrane fed mosquitoes, a Spearman correlation was performed comparing blood meal titres and mosquito titres, with Rho and p values provided. c Quantification of anti-CHIKV staining density. Mosquitoes were fed as in A and 5–8 fed mosquitoes per blood meal dose were examined by immunohistochemistry for CHIKV using an anti-capsid monoclonal antibody and DAPI staining for DNA. Staining areas were quantified by image analysis and expressed as a ratio of CHIKV staining over DAPI staining for each organ/tissue. Mean background staining density in uninfected mosquitoes was 0.004, range 0–0.15). Statistics by Kolmogorov-Smirnov tests: (i) P = 0.047, comparing salivary gland staining for mosquitoes given blood meals containing 7 log₁₀CCID₅₀/ml (n = 7) with staining for those given 5.25/6.25 log₁₀CCID₅₀/ml (staining data for the latter two doses were combined to provide n = 4) and (ii) P = 0.012, comparing salivary gland staining for mosquitoes given blood meals containing 9.5 log₁₀CCID₅₀/ml (n = 7) with staining for those given 5.25/6.25 log₁₀CCID₅₀/ml (n = 4). d Example of whole body section showing IFA staining in: head (H); midgut (M); and salivary glands (S). e-g High resolution images of IFA staining in head, midgut and salivary glands, respectively