The proposed infective biting dose was to be 3, 6, and 9 mosquitoes, respectively. However, a range of plus or minus one bite per dose was allowed. Therefore, screen-meshed boxes (7 × 7 × 7 cm) were filled with 4, 7, and 10 mosquitoes, to have a better chance of achieving the targeted mosquito dose in a single biting round. Participants who did not complete the minimal targeted dose were subjected to a second round of biting. Eighteen malaria-naïve volunteers were randomly assigned to one of three groups (N = 6) and were exposed by group, from the fewest (3 bites) to the greatest (9 bites) number of bites. Sporozoite challenge was carried out under strict adherence to experimental protocol in a secure room in the entomology unit at the IDIV. Volunteers were asked not to use any topical chemicals (e.g., soap, deodorant, perfume) that could affect mosquito feeding. Mosquitoes were allowed to bite the flexor side of the forearm for a 10 to 15-minute period, previously determined to be sufficient for full An. albimanus engorgement. After biting, all mosquitoes were dissected to confirm the presence of blood meal and sporozoites. Mosquitoes were considered positive if any number of sporozoites (> 1) was detected microscopically. Study participants were observed for 1 hour at the entomology unit, followed up by phone 8 hours later, and examined again 24 hours thereafter to assess the response to challenge.