Ethno-etiology meets virology: land leeches (family: <i>Haemadipsidae</i> ) as potential disease vectors

OBJECTIVES: Hematophagous terrestrial leeches are common in rainforest habitats and widely regarded as pests. Despite limited research, circumstantial evidence raises the possibility that, beyond being an annoyance, terrestrial leeches could potentially transmit diseases. METHODS: We explored this possibility using multiple approaches. First, we reviewed published literature to synthesize knowledge related to disease transmission by leeches. Second, we collected terrestrial leeches (genus Haemadipsa) from human-occupied rainforests in Peninsular Malaysia and applied metagenomic methods for virus discovery to their anterior segments. Finally, we conducted interviews to probe local knowledge and behavior related to leeches, testing whether cultures may encode information that recognizes and helps to prevent vector-borne disease transmission. RESULTS: Results indicate that terrestrial leeches are potential disease vectors, particularly via mechanical vector-borne transmission stimulated by human removal techniques. Supporting this, we identified four novel viruses within leeches, three of which are distantly related to medically important animal and human viruses which could potentially be transmitted among animal species, including humans. However, ethno-etiological evidence suggests that local Indigenous cultures do not recognize land leeches as disease vectors or promote behaviors likely to reduce transmission, suggesting knowledge may not encompass difficult-to-observe vectors. CONCLUSION: We conclude that disease transmission by terrestrial leeches is plausible and merits experimental study. Accession numbers: PX094876, PX118495, PX118496, PX118497, PX118498, PX118499.