Beyond the epistaxis: voluntary nasal leech (Dinobdella ferox) infestation revealed the leech behaviours and the host symptoms through the parasitic period

Abstract

Dinobdella ferox is the most reported and studied leech species parasitizing mammalian mucus membranes. However, our knowledge of D. ferox during parasitizing and its effects on hosts has remained limited. To investigate the behaviour of D. ferox in the parasitic period and the subsequent host symptoms, the author was infested voluntarily with three juvenile leeches under regularly-conducted examinations of complete blood count (CBC) and nasal endoscopy (NE). After the first head protrusion of the parasitizing leech at the host nostril, the occurrence of bleeding-related symptoms decreased and ceased completely weeks before the end of the parasitic period. Negligible impacts of the parasitizing leech on the host were shown by CBCs, and a parasitizing leech was able to hide from NE despite being so large it at times protrudes out of the host nostril. Finally, parasitizing D. ferox were coaxed to emerge at the nostril by water only after their first head protrusion, indicating that non-invasive removal of parasitizing D. ferox before head protrusion might be difficult. Through the voluntary infestation, the full documentation of behaviours of D. ferox in the parasitic period and host symptoms shown in this study will promote better diagnoses and treatments of nasal leech infestation.

Chromosome-level Dinobdella ferox genome provided a molecular model for its specific parasitism

“…Family Praobdellidae have a life cycle of parasitizing on mammalian mucous membranes [ 56 , 57 ]. Praobdellid leeches primarily parasitize the upper airway in mammals, and the nasal cavity is known as the most prevalent site of infection [ 34 , 55 ]. Leech infestation as a foreign body in the human respiratory system has been reported predominantly in Asia, the Mediterranean, and Africa [ 15 , 17 , 46 ].…”

“…In the early 2000s, researchers examined the host specificity of D. ferox , its development curve during the parasitic phase, and the behavioral inclination of free-living individuals before and after the parasitic period [ 13 , 34 ]. It was well known that juvenile D. ferox could only parasitize mammals and not avian or amphibian hosts, and its growth curve was correlated with host size.…”

“…Within a month, its mean parasitizing biomass expanded more rapidly in rabbits than in rats, and host mortality was indeed caused by its infestation. Furthermore, there was a notable inclination to dwell at the water surface before parasitizing, and it remained sensitive to airflow and vibration from hosts [ 34 , 48 ]. In contrast, after parasitizing, leeches preferred to settle at the bottom and remain unresponsive to host cues.…”