Flinders Island Spotted Fever Rickettsioses Caused by “marmionii” Strain of Rickettsia honei, Eastern Australia

Australia has 4 rickettsial diseases: murine typhus, Queensland tick typhus, Flinders Island spotted fever, and scrub typhus.We describe 7 cases of a rickettsiosis with an acute onset and symptoms of fever (100%), headache (71%), arthralgia (43%), myalgia (43%), cough (43%), maculopapular/petechial rash (43%), nausea (29%), pharyngitis (29%), lymphadenopathy (29%), and eschar (29%).Cases were most prevalent in autumn and from eastern Australia, including Queensland, Tasmania, and South Australia.One patient had a history of tick bite (Haemaphysalis novaeguineae).An isolate shared 99.2%, 99.8%, 99.8%, 99.9%, and 100% homology with the 17 kDa, ompA, gltA, 16S rRNA, and Sca4 genes, respectively, of Rickettsia honei.This Australian rickettsiosis has similar symptoms to Flinders Island spotted fever, and the strain is genetically related to R. honei.It has been designated the "marmionii" strain of R. honei, in honor of Australian physician and scientist Barrie Marmion.A ustralia has several endemic rickettsial diseases.In addition, epidemic typhus arrived with the first fleet in 1788 (1), but the disease did not become established in Australia.The current endemic rickettsial diseases are murine typhus (Rickettsia typhi), scrub typhus (Orientia tsutsugamushi), and the spotted fever group (SFG) diseases-Queensland tick typhus (QTT; R. australis) and Flinders Island spotted fever (FISF; R. honei) (2).QTT, first described in 1946, was characterized as a relatively mild disease with symptoms of fever, headache, malaise, enlarged lymph nodes, and a maculopapular (sometimes vesicular) rash.Most patients have an eschar and some have a slight cough, myalgia, and chills (3,4).Cases of QTT have been detected only on the eastern seaboard of mainland Australia, with most originating in late winter (5).FISF was described in Australia, in 1991.It is found in southeastern Australia and is characterized by fever, headache, myalgia, transient arthralgia, maculopapular rash, and cough in some cases (6,7).Most cases occur in summer.Both QTT and FISF are transmitted to humans by tick bites.Ticks of the genus Ixodes, especially I. holocyclus, are the main arthropod hosts of QTT and Bothriocroton hydrosauri (formerly Aponomma hydrosauri) are the main hosts of FISF (8-10).We describe 7 cases of a rickettsial disease similar to FISF, which occurred in the eastern half of Australia.The etiologic agent of this disease is an SFG rickettsia, genetically related to R. honei and less closely related to R. australis.The etiologic agent of the rickettsiosis has been designated the "marmionii" strain of R. honei.