Previously, it was suggested that haemadipsid leeches represent an important vector of trypanosomes amongst native animals in Australia. Consequently, Chtonobdella bilineata leeches were investigated for the presence of trypanosome species by polymerase chain reaction (PCR), DNA sequencing and in vitro isolation. Phylogenetic analysis ensued to further define the populations present. PCR targeting the 28S rDNA demonstrated that over 95% of C. bilineata contained trypanosomes; diversity profiling by deep amplicon sequencing of 18S rDNA indicated the presence of four different clusters related to the Trypanosoma (Megatrypanum) theileri. Novy–MacNeal–Nicolle slopes with liquid overlay were used to isolate trypanosomes into culture that proved similar in morphology to Trypanosoma cyclops in that they contained a large numbers of acidocalcisomes. Phylogeny of 18S rDNA/GAPDH/ND5 DNA sequences from primary cultures and subclones showed the trypanosomes were monophyletic, with T. cyclops as a sister group. Blood-meal analysis of leeches showed that leeches primarily contained blood from swamp wallaby (Wallabia bicolour), human (Homo sapiens) or horse (Equus sp.). The leech C. bilineata is a host for at least five lineages of Trypanosoma sp. and these are monophyletic with T. cyclops; we propose Trypanosoma cyclops australiensis as a subspecies of T. cyclops based on genetic similarity and biogeography considerations.

While some historians have noted the absence of animals in medical history, few have made the animal the central object of their historical gaze. Twenty years ago W.F. Bynum urged medical historians to follow historians of science in paying attention to the role of non-human animals in the material practices of medicine. Yet few have responded to his call. In this paper we again ask the question: what work can the non-human animal achieve for the history of medicine? We do so in the light of the conceptual possibilities opened up by the rapidly emerging field of ‘animal studies’. This interdisciplinary and sophisticated body of work has, in various ways, revealed the value of the ‘animal’ as a tool for exploring the co-constitution of species identity. We asked ourselves, surely, in our present biomedical world, this must be an area that we as medical historians are best placed to comment on; and what better place to start than the well-known, yet surprisingly little-studied, medical leech?