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.Ehrlichia chaffeensis: A species of gram-negative bacteria that is the causative agent of human EHRLICHIOSIS. This organism was first discovered at Fort Chaffee, Arkansas, when blood samples from suspected human ehrlichiosis patients were studied.Ehrlichia canis: Species of gram-negative bacteria in the family ANAPLASMATACEAE, causing EHRLICHIOSIS in DOGS. The most common vector is the brown dog tick. It can also cause disease in humans.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.Ehrlichia ruminantium: A species of gram-negative bacteria in the family ANAPLASMATACEAE, that causes HEARTWATER DISEASE in ruminants.Rickettsiaceae: A family of small, gram-negative organisms, often parasitic in humans and other animals, causing diseases that may be transmitted by invertebrate vectors.Rickettsiaceae Infections: Infections with bacteria of the family RICKETTSIACEAE.Anaplasma: A genus of gram-negative bacteria whose organisms are obligate parasites of vertebrates. Species are transmitted by arthropod vectors with the host range limited to ruminants. Anaplasma marginale is the most pathogenic species and is the causative agent of severe bovine anaplasmosis.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.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)Anaplasmataceae: A family of bacteria which inhabit RED BLOOD CELLS and cause several animal diseases.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.Heartwater Disease: A tick-borne septicemic disease of domestic and wild ruminants caused by EHRLICHIA RUMINANTIUM.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)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.Horse Diseases: Diseases of domestic and wild horses of the species Equus caballus.Tick Infestations: Infestations with soft-bodied (Argasidae) or hard-bodied (Ixodidae) ticks.Anaplasmosis: A disease of cattle caused by parasitization of the red blood cells by bacteria of the genus ANAPLASMA.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.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.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.Neorickettsia: Genus of gram-negative, intracytoplasmic bacteria that are found primarily in VACUOLES of MONOCYTES in the BLOOD and MACROPHAGES of lymphoid or other tissues of DOGS; HORSES, and humans. (From Int. J. Syst. Evol. Microbiol. (2001) 51:2145-2165)Horses: Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest.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.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.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.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.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Ixodidae: A family of hardbacked TICKS, in the subclass ACARI. Genera include DERMACENTOR and IXODES among others.Anaplasmataceae Infections: Infections with bacteria of the family ANAPLASMATACEAE.Deer: The family Cervidae of 17 genera and 45 species occurring nearly throughout North America, South America, and Eurasia, on most associated continental islands, and in northern Africa. Wild populations of deer have been established through introduction by people in Cuba, New Guinea, Australia, New Zealand, and other places where the family does not naturally occur. They are slim, long-legged and best characterized by the presence of antlers. Their habitat is forests, swamps, brush country, deserts, and arctic tundra. They are usually good swimmers; some migrate seasonally. (Walker's Mammals of the World, 5th ed, p1362)Babesia: A genus of tick-borne protozoan parasites that infests the red blood cells of mammals, including humans. There are many recognized species, and the distribution is world-wide.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 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.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.Anaplasma centrale: A species of gram-negative bacteria causing mild ANAPLASMOSIS in CATTLE. It also can infect SHEEP and GOATS. It is transmitted by TICKS.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.Doxycycline: A synthetic tetracycline derivative with similar antimicrobial activity.Fluorescent Antibody Technique, Indirect: A form of fluorescent antibody technique commonly used to detect serum antibodies and immune complexes in tissues and microorganisms in specimens from patients with infectious diseases. The technique involves formation of an antigen-antibody complex which is labeled with fluorescein-conjugated anti-immunoglobulin antibody. (From Bennington, Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984)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.Serologic Tests: Diagnostic procedures involving immunoglobulin reactions.Chaperonins: A family of multisubunit protein complexes that form into large cylindrical structures which bind to and encapsulate non-native proteins. Chaperonins utilize the energy of ATP hydrolysis to enhance the efficiency of PROTEIN FOLDING reactions and thereby help proteins reach their functional conformation. The family of chaperonins is split into GROUP I CHAPERONINS, and GROUP II CHAPERONINS, with each group having its own repertoire of protein subunits and subcellular preferences.Disease Reservoirs: Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (DISEASE VECTORS) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.Chromosome Walking: A technique with which an unknown region of a chromosome can be explored. It is generally used to isolate a locus of interest for which no probe is available but that is known to be linked to a gene which has been identified and cloned. A fragment containing a known gene is selected and used as a probe to identify other overlapping fragments which contain the same gene. The nucleotide sequences of these fragments can then be characterized. This process continues for the length of the chromosome.Granulocytes: Leukocytes with abundant granules in the cytoplasm. They are divided into three groups according to the staining properties of the granules: neutrophilic, eosinophilic, and basophilic. Mature granulocytes are the NEUTROPHILS; EOSINOPHILS; and BASOPHILS.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.DNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Anaplasma marginale: A species of gram-negative bacteria and causative agent of severe bovine ANAPLASMOSIS. It is the most pathogenic of the ANAPLASMA species.Bacterial Proteins: Proteins found in any species of bacterium.Seroepidemiologic Studies: EPIDEMIOLOGIC STUDIES based on the detection through serological testing of characteristic change in the serum level of specific ANTIBODIES. Latent subclinical infections and carrier states can thus be detected in addition to clinically overt cases.Bacterial Outer Membrane Proteins: Proteins isolated from the outer membrane of Gram-negative bacteria.Oxytetracycline: A TETRACYCLINE analog isolated from the actinomycete STREPTOMYCES rimosus and used in a wide variety of clinical conditions.Argas: A genus of softbacked TICKS in the family ARGASIDAE. Most infect birds or bats but a few parasitize terrestrial mammals.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.