Fig. 4

Mosquito survival probability after direct feeding on ivermectin- and moxidectin-treated pigs. a–d At week one post-treatment of pigs (by SC injection of ivermectin and moxidectin), mosquitoes were allowed to feed on pigs on Day 1 (a), Day 3 (b), Day 5 (c) and Day 8 (d) post-treatment. Mean ivermectin plasma concentration detected in pigs on these feeding days was 18.2, 32.8, 26.1 and 15.3 ng/ml, respectively. Mosquito mortality after feeding was recorded and expressed as survival probability. Zero survival probability of mosquitoes was recorded within 2–4 days of feeding on ivermectin-treated pigs. Survival probability of mosquitoes that fed on moxidectin-treated pigs only increased at Day 1 (a) and Day 3 (b) post-treatment with mean drug plasma concentration of 50.5 and 40.2 ng/ml, respectively. Mosquitoes that fed on moxidectin-treated pigs were frozen and checked after Day 5 (a) and Day 10 (b) of monitoring to ensure presence of moxidectin (data not shown). From Day 5 and onwards (c–f), post-treatment of pigs with moxidectin, mean plasma concentrations of 37.4, 27.4, 14.2, 9.8 ng/ml, respectively, had no impact on mosquito survival. e At week two or Day 15 post-treatment of pigs, mosquito survival probability of 0 was observed on Day 12 after feeding on ivermectin-treated pigs with decreased mean plasma concentration of 2.4 ng/ml. f At week three or 22 days post-treatment of pigs, very low mean ivermectin plasma concentration of 1.45 ng/ml had no impact on mosquito survival. Survival probability was similar to mosquitoes that fed on moxidectin-treated pigs and untreated pigs (control)