Ticks and fleas of the critically endangered mountain pygmy-possum (Burramys parvus) in Kosciuszko National Park, Australia.

The mountain pygmy-possum (Burramys parvus Broom, 1896) is a critically endangered marsupial, native to alpine-subalpine regions of Australia. Little research has been conducted on their health, including no formal parasite surveys. Parasite dynamics can reflect host and ecosystem health, acting as sensitive indicators of changing environmental, social, intra- and inter-species interactions and can contribute directly to host species knowledge. Reports of parasites affecting B. parvus are limited, with most from incidental observations. This study sampled ticks and fleas from B. parvus at eight sites in Kosciuszko National Park, New South Wales, Australia. A combination of morphological and molecular techniques was used to identify specimens, and screen for Rickettsia and Bartonella. The ticks were identified as Ixodes tasmani Neumann, 1899 and Ixodes sp. cf. tasmani Neumann, 1899. Ixodes heathi Kwak, 2018 was not found. The ticks that underwent molecular identification based on partial cox1 belonged to I. tasmani group within two distinct phylogenetic clusters. New mitogenomic reference sequences for two tick taxa and four flea species were obtained. Fleas were identified morphologically as Acanthopsylla rothschildi (Rainbow, 1905), Acanthopsylla scintilla (Rothschild, 1936), Pygiopsylla hoplia Jordan and Rothschild, 1922 and Stephanocircus simsoni Rothschild, 1905. Molecular screening found no evidence of Bartonella, one positive flea for Rickettsia, and a single suspect (late amplification) for Rickettsia. Statistically, greater B. parvus body weight was associated with decreased odds of tick presence and load, and male B. parvus had higher odds of flea presence. This study provides a systematic, standardised and formal survey of ticks and fleas of B. parvus in New South Wales, Australia, and establishes a baseline for future investigations into the impact of ectoparasites on the welfare of this critically endangered marsupial, supporting improved conservation measures across its restricted distribution.