Rickettsia: A genus of gram-negative, aerobic, rod-shaped bacteria often surrounded by a protein microcapsular layer and slime layer. The natural cycle of its organisms generally involves a vertebrate and an invertebrate host. Species of the genus are the etiological agents of human diseases, such as typhus.Rickettsia Infections: Infections by the genus RICKETTSIA.Rickettsia prowazekii: A species of gram-negative, aerobic bacteria that is the etiologic agent of epidemic typhus fever acquired through contact with lice (TYPHUS, EPIDEMIC LOUSE-BORNE) as well as Brill's disease.Rickettsia rickettsii: A species of gram-negative, aerobic bacteria that is the etiologic agent of ROCKY MOUNTAIN SPOTTED FEVER. Its cells are slightly smaller and more uniform in size than those of RICKETTSIA PROWAZEKII.Rickettsia felis: A species of gram-negative bacteria transmitted by the flea Ctenocephalides felis, and known to infect CATS, oppossums, and humans.Typhus, Epidemic Louse-Borne: The classic form of typhus, caused by RICKETTSIA PROWAZEKII, which is transmitted from man to man by the louse Pediculus humanus corporis. This disease is characterized by the sudden onset of intense headache, malaise, and generalized myalgia followed by the formation of a macular skin eruption and vascular and neurologic disturbances.Rocky Mountain Spotted Fever: An acute febrile illness caused by RICKETTSIA RICKETTSII. It is transmitted to humans by bites of infected ticks and occurs only in North and South America. Characteristics include a sudden onset with headache and chills and fever lasting about two to three weeks. A cutaneous rash commonly appears on the extremities and trunk about the fourth day of illness.Boutonneuse Fever: A febrile disease of the Mediterranean area, the Crimea, Africa, and India, caused by infection with RICKETTSIA CONORII.Orientia tsutsugamushi: A gram-negative, rod-shaped to coccoid bacterium. It is the etiologic agent of SCRUB TYPHUS in humans and is transmitted by mites from rodent reservoirs.Typhus, Endemic Flea-Borne: An infectious disease clinically similar to epidemic louse-borne typhus (TYPHUS, EPIDEMIC LOUSE-BORNE), but caused by RICKETTSIA TYPHI, which is transmitted from rat to man by the rat flea, XENOPSYLLA CHEOPIS.Ticks: Blood-sucking acarid parasites of the order Ixodida comprising two families: the softbacked ticks (ARGASIDAE) and hardbacked ticks (IXODIDAE). Ticks are larger than their relatives, the MITES. They penetrate the skin of their host by means of highly specialized, hooked mouth parts and feed on its blood. Ticks attack all groups of terrestrial vertebrates. In humans they are responsible for many TICK-BORNE DISEASES, including the transmission of ROCKY MOUNTAIN SPOTTED FEVER; TULAREMIA; BABESIOSIS; AFRICAN SWINE FEVER; and RELAPSING FEVER. (From Barnes, Invertebrate Zoology, 5th ed, pp543-44)Siphonaptera: An order of parasitic, blood-sucking, wingless INSECTS with the common name of fleas.Dermacentor: A widely distributed genus of TICKS, in the family IXODIDAE, including a number that infest humans and other mammals. Several are vectors of diseases such as TULAREMIA; ROCKY MOUNTAIN SPOTTED FEVER; COLORADO TICK FEVER; and ANAPLASMOSIS.Ixodidae: A family of hardbacked TICKS, in the subclass ACARI. Genera include DERMACENTOR and IXODES among others.Tick-Borne Diseases: Bacterial, viral, or parasitic diseases transmitted to humans and animals by the bite of infected ticks. The families Ixodidae and Argasidae contain many bloodsucking species that are important pests of man and domestic birds and mammals and probably exceed all other arthropods in the number and variety of disease agents they transmit. Many of the tick-borne diseases are zoonotic.Coxiella: A genus of gram-negative, rod-shaped bacteria that is widely distributed in TICKS and various mammals throughout the world. Infection with this genus is particularly prevalent in CATTLE; SHEEP; and GOATS.Rickettsiaceae: A family of small, gram-negative organisms, often parasitic in humans and other animals, causing diseases that may be transmitted by invertebrate vectors.Rickettsieae: A tribe of gram-negative bacteria of the family RICKETTSIACEAE whose organisms are found in arthropods and are pathogenic for man and certain other vertebrate hosts.Rickettsiaceae Infections: Infections with bacteria of the family RICKETTSIACEAE.Arachnid Vectors: Members of the class Arachnida, especially SPIDERS; SCORPIONS; MITES; and TICKS; which transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.Rickettsial Vaccines: Vaccines for the prevention of diseases caused by various species of Rickettsia.Rhipicephalus sanguineus: A species of tick (TICKS) in the family IXODIDAE, distributed throughout the world but abundant in southern Europe. It will feed on a wide variety of MAMMALS, but DOGS are its preferred host. It transmits a large number of diseases including BABESIOSIS; THEILERIASIS; EHRLICHIOSIS; and MEDITERRANEAN SPOTTED FEVER.Rickettsia akari: A species of gram-negative bacteria that causes rickettsialpox. The vector is a mouse mite and the reservoirs are mites and mice.Arthropod Vectors: Arthropods, other than insects and arachnids, which transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.Phthiraptera: An order of small, wingless parasitic insects, commonly known as lice. The suborders include ANOPLURA (sucking lice); AMBLYCERA; ISCHNOCERA; and Rhynchophthirina (elephant and warthog lice).Ixodes: The largest genus of TICKS in the family IXODIDAE, containing over 200 species. Many infest humans and other mammals and several are vectors of diseases such as LYME DISEASE, tick-borne encephalitis (ENCEPHALITIS, TICK-BORNE), and KYASANUR FOREST DISEASE.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Citrate (si)-Synthase: Enzyme that catalyzes the first step of the tricarboxylic acid cycle (CITRIC ACID CYCLE). It catalyzes the reaction of oxaloacetate and acetyl CoA to form citrate and coenzyme A. This enzyme was formerly listed as EC 4.1.3.7.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Bacterial Outer Membrane Proteins: Proteins isolated from the outer membrane of Gram-negative bacteria.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Bartonella: A genus of gram-negative bacteria characteristically appearing in chains of several segmenting organisms. It occurs in man and arthropod vectors and is found only in the Andes region of South America. This genus is the etiologic agent of human bartonellosis. The genus Rochalimaea, once considered a separate genus, has recently been combined with the genus Bartonella as a result of high levels of relatedness in 16S rRNA sequence data and DNA hybridization data.Vero Cells: A CELL LINE derived from the kidney of the African green (vervet) monkey, (CERCOPITHECUS AETHIOPS) used primarily in virus replication studies and plaque assays.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Nymph: The immature stage in the life cycle of those orders of insects characterized by gradual metamorphosis, in which the young resemble the imago in general form of body, including compound eyes and external wings; also the 8-legged stage of mites and ticks that follows the first moult.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Tick Infestations: Infestations with soft-bodied (Argasidae) or hard-bodied (Ixodidae) ticks.Trombiculidae: Family of MITES in the superfamily Trombiculoidea, suborder Prostigmata, which attack humans and other vertebrates, causing DERMATITIS and severe allergic reactions. Chiggers, red bugs, and harvest mites commonly refer to the larval stage of Trombiculid mites, the only parasitic stage of the mite's life cycle.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Ctenocephalides: A genus of FLEAS in the family Pulicidae. It includes the cat flea (Ctenocephalides felis), one of the most common species on earth.Ehrlichia: Small, often pleomorphic, coccoid to ellipsoidal organisms occurring intracytoplasmically in circulating LYMPHOCYTES. They are the etiologic agents of tick-borne diseases of humans; DOGS; CATTLE; SHEEP; GOATS; and HORSES.Bacterial Proteins: Proteins found in any species of bacterium.L Cells (Cell Line): A cultured line of C3H mouse FIBROBLASTS that do not adhere to one another and do not express CADHERINS.Genes, Bacterial: The functional hereditary units of BACTERIA.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Q Fever: An acute infectious disease caused by COXIELLA BURNETII. It is characterized by a sudden onset of FEVER; HEADACHE; malaise; and weakness. In humans, it is commonly contracted by inhalation of infected dusts derived from infected domestic animals (ANIMALS, DOMESTIC).Pediculus: Lice of the genus Pediculus, family Pediculidae. Pediculus humanus corporus is the human body louse and Pediculus humanus capitis is the human head louse.Ectoparasitic Infestations: Infestations by PARASITES which live on, or burrow into, the surface of their host's EPIDERMIS. Most ectoparasites are ARTHROPODS.Genome, Bacterial: The genetic complement of a BACTERIA as represented in its DNA.Coxiella burnetii: A species of gram-negative bacteria that grows preferentially in the vacuoles of the host cell. It is the etiological agent of Q FEVER.Dog Diseases: Diseases of the domestic dog (Canis familiaris). This term does not include diseases of wild dogs, WOLVES; FOXES; and other Canidae for which the heading CARNIVORA is used.Hemiptera: A large order of insects characterized by having the mouth parts adapted to piercing or sucking. It is comprised of four suborders: HETEROPTERA, Auchenorrhyncha, Sternorrhyncha, and Coleorrhyncha.Ehrlichiosis: A tick-borne disease characterized by FEVER; HEADACHE; myalgias; ANOREXIA; and occasionally RASH. It is caused by several bacterial species and can produce disease in DOGS; CATTLE; SHEEP; GOATS; HORSES; and humans. The primary species causing human disease are EHRLICHIA CHAFFEENSIS; ANAPLASMA PHAGOCYTOPHILUM; and Ehrlichia ewingii.