Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2018

Ticks in Australia: endemics; exotics; which ticks bite humans? (#47)

Stephen C Barker 1 , Dayama Barker 1
  1. Discipline of Parasitology, School of Chemistry & Molecular Biosciences, University of Queensland, St Lucia, QLD, Australia

At least 71 species of ticks occur in Australia (Barker et al 2014 IntJParasit,12,941-; Ash et al 2017 Parasit&Vectors10,70-). A further 33 or so species are endemic to our neighbours New Guinea and New Zealand. The ticks of Australasia are phylogenetically distinct. Indeed, there are at least two lineages of ticks that are unique to Australasia: the sub-family Bothriocrotinae, Klompen, Murrell & Barker 2002; and the new genus Archaeocroton Barker & Burger 2018. Ixodes holocyclus, the eastern paralysis tick, is notorious for biting humans on the east coast of Australia. The toxins of this tick seem to be the most potent of all tick-toxins, indeed there have been at least 20 fatalities (Barker & Walker 2014 Zootaxa3816). To provide context to the number of fatalities caused by I. holocyclus, there have been comparable numbers of fatalities from red-back spiders (n=18) and funnel-web spiders (n=13, Sutherland & Tibballs 2001 OxfordUnivPress). Thankfully, deaths from the bite of I. holocyclus are now rare due to the advent of intensive care-units in regional hospitals and expert medical treatment. Not so, for dogs and cats, since the treatment of tick-paralysis in dogs and cats is difficult, and thus many be extremely expensive. But a new generation of tick-preventative for dogs, but not cats, provides unprecedented protection against I. holocyclus. The illnesses that I. holocyclus has been associated with include Australian multi-system disorder, post-infection fatigue, auto-immune disease, paralysis, allergies (particularly to the bites of larvae), Queensland Tick Typhus (Rickettsia australis), mammalian meat allergy and tick anaphylaxis. Professor Graves, the speaker following me, will address some of these illnesses. In WA and on Yorke Peninsular, SA, Amblyomma triguttatum triguttatum, the ornate kangaroo, tick is the villain (Rickettsia gravesii with a nasty bite) whereas on Flinders Island and other parts of Southern Australia the troublesome tick is Bothriocroton hydrosauri, the southern reptile tick (Rickettsia honei, Flinders Island Spotted Fever). Lastly, Ornithodoros capensis, the sea bird soft tick, is notorious for the very large number of different viruses that have been isolated from this tick (Barker & Walker 2014, Zootaxa3816).