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A novel spotted fever group Rickettsia was found in Haemaphysalis sulcata ticks collected from sheep and goats in Croatia in 2006. At the same time, a genetically identical organism was co-isolated with the embryonic cell line CCE3 obtained from the soft tick Carios capensis in Georgia, USA. In this study, further phenotypic and genotypic characteristics of the novel rickettsial strain present in H. sulcata ticks were investigated. Based on the cultivation of bacteria in mosquito and Vero cell cultures, the presence of rickettsiae in tick tissues and cell cultures [confirmed by transmission electron microscopy (TEM)] and the amplification and sequencing of five rickettsial genes, it was demonstrated that the novel Rickettsia strain fulfils the criteria to be classified as a novel species. The name Rickettsia hoogstraalii sp. nov. is proposed for the new strain. Rickettsia hoogstraalii sp. nov., an obligately intracellular bacterium, was grown in Vero cells and arthropod CCE3, ISE6 and C6/36 cell lines. The morphology of the cells of the novel species was typical of SFG rickettsiae. The small coccobacillary appearance of the bacteria was apparent with light microscopy. A Gram-negative bacterial cell wall and a cytoplasmic membrane separated by a narrow periplasmic space were visible by TEM. To date, Rickettsia hoogstraalii sp. nov. has been isolated from two species of ticks, H. sulcata and C. capensis. The novel species appears to be geographically widely distributed, having been detected in Croatia, Spain and Georgia, USA. Although no information is available regarding the possible pathogenicity of the novel species for vertebrate hosts, R. hoogstraalii sp. nov. has a cytopathic effect in Vero, CCE3 and ISE6 cells. Sequence analyses of the 16S rRNA, 17 kDa, gltA, ompA and ompB genes indicated that even though R. hoogstraalii sp. nov. was closely related to Rickettsia felis, it represents a separate species within the spotted fever group. The type strain of R. hoogstraalii sp. nov. is strain CroaticaT (=DSM 22243T=UTMB 00003T).

Rickettsia was first detected in seabird soft-bodied ticks, Carios capensis and C. sawaii in Japan. According to sequence analysis, Rickettsia in Japan was identical to Rickettsia scc31 in C. capensis in the U.S.A. This suggested that an environmental circulation had consisted among microorganisms, ticks and long distance migratory seabirds around the Pacific Ocean.

There are two major groups of ticks: soft ticks and hard ticks. The hard ticks comprise the prostriate ticks and the metastriate ticks. The mitochondrial (mt) genomes of one species of prostriate tick and two species of metastriate ticks had been sequenced prior to our study. The prostriate tick has the ancestral arrangement of mt genes of arthropods, whereas the two metastriate ticks have rearrangements of eight genes and duplicate control regions. However, the arrangement of genes in the mt genomes of soft ticks had not been studied. We sequenced the mt genomes of two species of soft ticks, Carios capensis and Ornithodoros moubata, and a metastriate tick, Haemaphysalis flava. We found that the soft ticks have the ancestral arrangement of mt genes of arthropods, whereas the metastriate tick, H. flava, shares the rearrangements of mt genes and duplicate control regions with the other two metastriate ticks that have previously been studied. Our study indicates that gene rearrangements and duplicate control regions in mt genomes occurred once in the most recent common ancestor of metastriate ticks, whereas the ancestral arrangement of arthropods has remained unchanged for over 400 million years in the lineages leading to the soft ticks and the prostriate ticks.

Carios capensis (Neumann, 1901) Host(s) Seabirds: Pterodroma neglecta, Pterodroma nigripennis, Puffinus assimilis, Phaethon rubricauda, Morus serrator, Stictocarbo punctatus punctatus, Larus novaehollandiae scopulinus, Anous stolidus pileatus, Onychoprion fuscatus serratus. Land bird: Porzana tabuensis tabuensis. Distribution World: Widespread on islands of the South Atlantic, Pacific and Indian Oceans, and occasionally on the mainland between 40 ºN and 45 ºS. Extralimital records in the Northern Hemisphere have been considered doubtful. New Zealand: Somes Island (Wellington Harbour), Cape Kidnappers, Raglan, West Coast, Banks Peninsula. References: Neumann (1901); Dumbleton (1958, 1961); Amerson (1968); Ramsay (1968); Theiler (1971); Heath (1977, 2006 a, 2010 a); Bishop & Heath (1998); Gordon (2010)., Published as part of Heath, Allen C. G., Palma, Ricardo L., Cane, Rachel P. & Hardwick, Scott, 2011, Checklist of New Zealand ticks (Acari: Ixodidae, Argasidae), pp. 55-63 in Zootaxa 2995 on page 58, DOI: 10.5281/zenodo.203775, {"references":["Neumann, L. G. (1901) Revision de la famille des ixodides. Memoires de la Societe Zoologique de France, 14, 249 - 372.","Dumbleton, L. J. (1958) The occurrence of an argasid tick in New Zealand. New Zealand Journal of Science, 1, 570 - 578.","Dumbleton, L. J. (1961) The ticks (Acarina: Ixodoidea) of sea birds in New Zealand waters. New Zealand Journal of Science, 4, 760 - 769.","Amerson, A. B. (1968) Tick distribution in the Central Pacific as influenced by sea bird movement. Journal of Medical Entomology, 5, 332 - 339.","Ramsay, G. W. (1968) The argasid tick Ornithodoros capensis Neumann, from the Kermadec Islands. New Zealand Entomologist, 4, 32 - 34.","Theiler, G. (1971) Ixodoidea. Pp. 327 - 334. In: van Zinderen Bakker, E. M., Winterbottom, J. M. & Dyer, R. A. (eds), Report on the South African Biological and Geographical Expedition 1965 - 66. A. A. Balkema, Cape Town.","Heath, A. C. G. (1977) Zoogeography of the New Zealand tick fauna. Tuatara, 23, 26 - 38.","Heath, A. C. G. (2006 a) Observations on Ixodes eudyptidis Maskell (Acari: Ixodidae), Ornithodoros capensis Neumann (Acari: Argasidae), and other tick parasites of sea birds in New Zealand. Systematic & Applied Acarology, 11, 131 - 140.","Heath, A. C. G. (2010 a) Checklist of ectoparasites of birds in New Zealand: additions and corrections. Surveillance, 37, 12 - 17.","Bishop, D. M. & Heath, A. C. G. (1998) Checklist of ectoparasites of birds in New Zealand. Surveillance, 25 (Special Issue), 13 - 31.","Gordon, D. P. (ed.) (2010) New Zealand Inventory of Biodiversity. Vo l u m e Tw o. Kingdom Animalia - Chaetognatha, Ecdysozoa, Ichnofossils. Canterbury University Press, Christchurch. 528 pp."]}