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.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 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 Infections: Infections by the genus RICKETTSIA.Chlamydia Infections: Infections with bacteria of the genus CHLAMYDIA.Chlamydia trachomatis: Type species of CHLAMYDIA causing a variety of ocular and urogenital diseases.Chlamydia: A genus of the family CHLAMYDIACEAE whose species cause a variety of diseases in vertebrates including humans, mice, and swine. Chlamydia species are gram-negative and produce glycogen. The type species is CHLAMYDIA TRACHOMATIS.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.Aspartate Kinase: An enzyme that catalyzes the formation of beta-aspartyl phosphate from aspartic acid and ATP. Threonine serves as an allosteric regulator of this enzyme to control the biosynthetic pathway from aspartic acid to threonine. EC 2.7.2.4.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.Rickettsiaceae: A family of small, gram-negative organisms, often parasitic in humans and other animals, causing diseases that may be transmitted by invertebrate vectors.Homoserine Dehydrogenase: An enzyme that catalyzes the reduction of aspartic beta-semialdehyde to homoserine, which is the branch point in biosynthesis of methionine, lysine, threonine and leucine from aspartic acid. EC 1.1.1.3.Rickettsia conorii: A species of gram-negative, aerobic bacteria that is the etiologic agent of BOUTONNEUSE FEVER. It resembles RICKETTSIA RICKETTSII but is antigenically distinct and less virulent for animals and man. (From Bergey's Manual of Systematic Bacteriology, vol 1)Boutonneuse Fever: A febrile disease of the Mediterranean area, the Crimea, Africa, and India, caused by infection with RICKETTSIA CONORII.Anaplasma phagocytophilum: A species of gram-negative bacteria in the genus ANAPLASMA, family ANAPLASMATACEAE, formerly called Ehrlichia phagocytophila or Ehrlichia equi. This organism is tick-borne (IXODES) and causes disease in horses and sheep. In humans, it causes human granulocytic EHRLICHIOSIS.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.Bartonella henselae: A species of gram-negative bacteria that is the etiologic agent of bacillary angiomatosis (ANGIOMATOSIS, BACILLARY). This organism can also be a cause of CAT-SCRATCH DISEASE in immunocompetent patients.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.Alphaproteobacteria: A class in the phylum PROTEOBACTERIA comprised mostly of two major phenotypes: purple non-sulfur bacteria and aerobic bacteriochlorophyll-containing bacteria.PrintingWireless Technology: Techniques using energy such as radio frequency, infrared light, laser light, visible light, or acoustic energy to transfer information without the use of wires, over both short and long distances.Electronic Mail: Messages between computer users via COMPUTER COMMUNICATION NETWORKS. This feature duplicates most of the features of paper mail, such as forwarding, multiple copies, and attachments of images and other file types, but with a speed advantage. The term also refers to an individual message sent in this way.Rate Setting and Review: A method of examining and setting levels of payments.Antibodies: Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).United StatesVermontLegionnaires' Disease: An acute, sometimes fatal, pneumonia-like bacterial infection characterized by high fever, malaise, muscle aches, respiratory disorders and headache. It is named for an outbreak at the 1976 Philadelphia convention of the American Legion.Bronchopneumonia: Inflammation of the lung parenchyma that is associated with BRONCHITIS, usually involving lobular areas from TERMINAL BRONCHIOLES to the PULMONARY ALVEOLI. The affected areas become filled with exudate that forms consolidated patches.Legionella: Gram-negative aerobic rods, isolated from surface water or thermally polluted lakes or streams. Member are pathogenic for man. Legionella pneumophila is the causative agent for LEGIONNAIRES' DISEASE.Legionella pneumophila: A species of gram-negative, aerobic bacteria that is the causative agent of LEGIONNAIRES' DISEASE. It has been isolated from numerous environmental sites as well as from human lung tissue, respiratory secretions, and blood.Hartmannella: A genus of free-living amoebae found in fresh water. The cysts usually pass harmlessly through the intestinal tract of man and may thus be found in feces. Occasionally, these organisms cause respiratory tract infections or generalized fatal meningoencephalitis.Scrub Typhus: An acute infectious disease caused by ORIENTIA TSUTSUGAMUSHI. It is limited to eastern and southeastern Asia, India, northern Australia, and the adjacent islands. Characteristics include the formation of a primary cutaneous lesion at the site of the bite of an infected mite, fever lasting about two weeks, and a maculopapular rash.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.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.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Mites: Any arthropod of the subclass ACARI except the TICKS. They are minute animals related to the spiders, usually having transparent or semitransparent bodies. They may be parasitic on humans and domestic animals, producing various irritations of the skin (MITE INFESTATIONS). Many mite species are important to human and veterinary medicine as both parasite and vector. Mites also infest plants.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.Dictionaries, MedicalDictionaries as Topic: Lists of words, usually in alphabetical order, giving information about form, pronunciation, etymology, grammar, and meaning.Rickettsia felis: A species of gram-negative bacteria transmitted by the flea Ctenocephalides felis, and known to infect CATS, oppossums, and humans.Ctenocephalides: A genus of FLEAS in the family Pulicidae. It includes the cat flea (Ctenocephalides felis), one of the most common species on earth.Flea Infestations: Parasitic attack by members of the order SIPHONAPTERA.Siphonaptera: An order of parasitic, blood-sucking, wingless INSECTS with the common name of fleas.ItalyEctoparasitic Infestations: Infestations by PARASITES which live on, or burrow into, the surface of their host's EPIDERMIS. Most ectoparasites are ARTHROPODS.Rickettsial Vaccines: Vaccines for the prevention of diseases caused by various species of Rickettsia.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)Rhodnius: A genus of the subfamily TRIATOMINAE. Rhodnius prolixus is a vector for TRYPANOSOMA CRUZI.