Laser-based killing of a macroparasite inside its live invertebrate host

Clearing infection is an essential step to address many issues in host-parasite interactions but is challenging when dealing with endoparasites of large size relative to that of their host. Here, we took advantage of the lethality, contactless and versatility of high-energy laser beam to achieve it, using thorny-headed worms (Acanthocephala) and their amphipod intermediate host as a model system. We show that laser-based de-parasitization can be achieved using 450 nm Blue Diode Laser targeting carotenoid pigments in the bird acanthocephalan Polymorphus minutus. Using proboscis evagination failure and DNA degradation to establish parasite death, we found that 80% P. minutus died from within-host exposure to 5 pulses of 50 ms duration, 1.4 W power. Survival of infected gammarids 11 days after laser treatment was 60%. Preliminary tests were also performed with Nanosecond-Green Laser targeting lipids in Pomphorhynchus tereticollis, another acanthocephalan parasite. We discuss the efficiency and side-effect of laser treatment in this host-parasite system and highlight the perspectives that this technology more generally offers in parasitology.