Tick ecology is complex, fascinating, and incredibly important to our society. The emergence of zoonotic pathogens as major health threats makes it essential that we increase our understanding of pathogen vectors such as ticks. In the urban areas where the majority of humans live, we must determine the role that different tick host species play in supporting and transporting ticks. More fundamentally, little is known about how generalist ticks are interacting with the hosts they evolved with in habitats that have been modified by humans, and how these interactions are impacted by the introduction of other species.
In order to study this, we trapped small mammals at paired backyard/forest sites along the peri-urban fringe in Sydney, Australia in 2016 and 2017. Animals used in the study were put under general anaesthesia in the field using inhaled isoflurane to standardize tick collection and to gather information on the distribution of ticks across each host’s body. We defined host landscapes into five generalized body regions (head/limbs/genitals/dorsal/ventral).
The native long nosed bandicoot (Perameles nasuta) and the introduced black rat (Rattus rattus) made up the vast majority of trapped animals. Controlling for animal weight, P. nasuta had significantly more ticks than R. rattus. Ticks were distributed equally across P. nasuta, while ticks were mostly located on the heads of R. rattus.
While P. nasuta had more ticks than R. rattus, the two species had no difference in the number of ticks on their heads. Fewer ticks on all other body regions of R. rattus could suggest greater ability to groom, due to tooth morphology, flexibility, and social behaviours. Combined with the finding that P. nasuta at locations without R. rattus had significantly more ticks than P. nasuta at locations where R. rattus were also captured, it is possible that R. rattus suppress tick populations. Our study is the first to study introduced rats and their role in tick-host interactions, and the first to use GA in the field to study the distribution of ticks across host landscapes. Further work should be done to understand hosts as landscapes, and the role of introduced species in tick-host-pathogen interactions in cities, as they continue to expand around the world.