Systematic Literature Review: The Interface of Photogenetics and Phthiraptera (Lice)

Abstract: Background: Photogenetics, the use of light to control or observe genetically targeted cellular processes, has transformed modern biology. The order Phthiraptera (lice), with its simplified nervous system and robust phototactic behaviors, presents a potential model for applying these tools to parasitology. Objective: To systematically identify and synthesize the literature on the direct application of photogenetics in Phthiraptera and to evaluate the foundational research enabling such future work. Methods: We conducted a systematic review following the PRISMA 2020 guidelines, searching four electronic databases from inception to October 2023. Results: Our search yielded 127 records. After screening, no studies directly applied photogenetics to lice. However, 18 foundational studies were identified, detailing the photobiology, sensory anatomy (including SEM analyses), and genomics of Phthiraptera. These studies confirm the presence of ocelli and negative phototaxis in certain species, identify molecular components like opsins, and highlight the absence of genetic transformation protocols. Conclusion: A significant gap exists between the potential of photogenetics and its application in Phthiraptera research. The field is primed for a breakthrough contingent upon developing methods for genetic manipulation in these ecologically and medically important parasites.