| Viruses, rickettsias, protozoa, and nematodes all have species that are transmitted between vertebrates through biting flies. |
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| Humans contract most rickettsial diseases only when they break into a cycle in nature in which the rickettsias live. |
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| The rickettsias, which range in size from 250 nanometres to more than 1 micrometre and have no cell wall but are surrounded by a cell membrane, cause a group of diseases characterized by fever and a rash. |
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| Pleomorphism is particularly prevalent in certain groups of bacteria and in yeasts, rickettsias, and mycoplasmas and greatly complicates the task of identifying and studying them. |
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| Polymerase chain reaction survey for rickettsias and bartonellas in ticks from New Zealand. |
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