Box and whisker plots of larval fluorescence after incubation with sera or phosphate buffered saline (PBS). The horizontal line within each box represents the median of the six readings (absent if there are only two integer readings), and the ⊕ symbol indicates the mean. Negative controls consisted of PBS and pooled serum from 100 specific pathogen-free cats (NEG-Pool). Fluorescence resulting from incubation of larvae with (a) serum from a cat experimentally infected with Aelurostrongylus abstrusus, collected before infection, on post-infection days (PID) 8, 29 and 141, and on post-treatment (PT) day 28 (PID 176); (b) serum from the experimentally infected cat (Exp-Aa) collected PID 141 and from two naturally infected cats (NAT-Aa1 and NAT-Aa2); (c) serum from NAT-Aa1, NAT-Aa2 and EXP-Aa (PID 141), and from a cat experimentally infected with the hookworm Ancylostoma braziliense (EXP-Ab)