''Rickettsia australis'' is a

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

that causes a medical condition called Queensland tick typhus. The probable vectors are the tick species, ''

Ixodes holocyclus ''Ixodes holocyclus'', commonly known as the Australian paralysis tick, is one of about 75 species in the Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is u ...

'' and '' Ixodes tasmani''. Small marsupials are suspected reservoirs of this bacterium.

Early Scientific History

In 1946 this bacterium was discovered and isolated as a new tick-borne illness that began to present in Australian soldiers stationed in northern Queensland. This illness was designated as the North Queensland tick typhus. From here, researchers began to continue this work. After many experiments were completed, such as cross-protection and serological assays in guinea pigs, it was concluded that the isolate previously seen in 1946 was a new addition to the spotted fever group. Although it wasn’t until 1950 when the organism was officially discovered and named ''Rickettsia australis'' by a scientist with the surname Philip.

Role in Human Disease

''Rickettsia australis'' causes Queensland tick typhus (QTT). This disease was first identified in 1946, although the specific bacterium was not identified until 1950. Rickettsia australis produces a spectrum of symptoms ranging from headaches and fever but can ultimately lead to sepsis and vital organ failure.

Biology

Rickettsia

The ''Rickettsia'' genus contain a distinct collection of intracellular gram-negative bacteria. They are serologically categorized into two major classes: # the spotted fever group #* Subsets: the ancestral group & the transitional group # the typhus group ''Rickettsia'' ''australis'' belongs to the category of the spotted fever group and the subset of transitional group. Together these organisms encompass more than 36 tick-borne species, 15 of these species are known causal agents of human illnesses. Of the vector-borne disease these zoonoses are among the oldest known.

Genome

''Rickettsia australis'' is a distinct pathogen that belongs in the ''Rickettsial'' spotted fever group. It genome is sequences and is approximately 1.29 Mb (mega–

base-pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s). It is also highly similar to ''Rickettsia akari'' which is the closest known phylogenetic neighbor. The chromosome has a predicted size of 1,297,390 bp. It is also known that the chromosome itself contain 1,110 genes with approximately 855 genes function to encode proteins with putative functions and 255 encode hypothetical proteins and proteins of known function. To see the whole genome project on the database Genbank the accession number is AKVZ00000000.

Vectors

The three tick species that have been identified as vectors of ''R. australis'' are ''Ixodes tasmani'', ''Ixodes holocyclus'', and ''Ixodes cornuatus''. The species of ticks known to harbor ''R. australis'' typically reside along the eastern coastline ranging from the Torres Strait islands to Queensland and Victoria.

Mechanism

Once the infected tick bites an individual, the ''Rickettsiae'' bacteria can spread throughout the bloodstream. It begins by targeting the endothelium and will eventually start to target the vascular smooth muscle cells (VSMCs). Once in the bloodstream, the ''Rickettsia Australias'' can immediately begin multiplying by binary fission. If left in the body long enough without treatment, it will parasitize healthy cells and create lasting damage.

Prevalence

''Rickettsia australis'' and its associated disease Queensland Tick Typhus are an ever changing diseases with growing public health importance.

References

{{Taxonbar, from=Q7331928 Rickettsiaceae