Changes in parasite traits, rather than intensity, affect the dynamics of infection under external perturbation

摘要

Author summary Host-parasite interactions frequently lead to complex dynamics of infection that can be difficult to explain when parasite data are not accurate or complete, which is often the case in natural systems. We used the helminth-rabbit study case and developed a state-space mathematical model to capture the variation in intensity of infection and egg shedding in an experimental trial where hosts were infected weekly, then treated with an anthelminthic and subsequently re-challenged following the same infection regime. Simulations indicate that hosts control the parasite proportionally to the accumulated force of infection and intensities decrease both in the pre- and post-treatment phase. The peak and mean intensity of infection is similar before and after treatment; however, the degree of egg shedding declines proportionately with parasite body length and both traits are lower in the post- than the pre-treatment phase. The intensity of infection fails to adequately explain the variation in the degree of shedding within and between hosts. Instead, this pattern is captured by changes in parasite body length. More attention should be given to the host-parasite interactions within hosts and the impact of external perturbation on the dynamics of infection and transmission.