The Rickettsiaceae are a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of bacteria, including most notably the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Rickettsia

Rickettsia

Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...

.

Most human pathogens are in genus Rickettsia. They spend part of their life cycle in the bodies of arthropods such as ticks or lice, and are then transmitted to humans or other mammals by the bite of the arthropod.

It is a Gram-negative bacteria, very sensitive to environmental exposure, and thus is an obligate intracellular infection.

Rickettsia rickettsii

Rickettsia rickettsii

Rickettsia rickettsii is a unicellular, gram-negative coccobacillus that is native to the New World. It belongs to the spotted fever group of Rickettsia and is most commonly known as the causative agent of Rocky Mountain spotted fever . By nature, R...

is considered the prototypical infectious organism in the group.

Similar arthropod borne Rickettsial infections exist in other areas of the world.