Rickettsiae are a diverse collection of obligate intracellular, gram-negative bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology that have a tropism for vascular endothelial cells. The vectors for transmission vary by species but include ticks 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. Coxiella/Q Fever, fleas, mites 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. Scabies, and lice. The most clinically relevant pathogens are R. rickettsii, which causes Rocky Mountain spotted fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever; R. prowazekii, which causes epidemic (louse-borne) typhus; R. typhi, which causes endemic typhus; and R. akari, which causes rickettsialpox. All of these diseases are a form of inflammatory vasculitis Vasculitis Inflammation of any one of the blood vessels, including the arteries; veins; and rest of the vasculature system in the body. Systemic Lupus Erythematosus and commonly present with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, and rash Rash Rocky Mountain Spotted Fever. Treatment is with doxycycline.
Last updated: 29 Mar, 2022
R. rickettsii: photomicrograph of a yolk sac Yolk Sac The first of four extra-embryonic membranes to form during embryogenesis. In reptiles and birds, it arises from endoderm and mesoderm to incorporate the egg yolk into the digestive tract for nourishing the embryo. In placental mammals, its nutritional function is vestigial; however, it is the source of intestinal mucosa; blood cells; and germ cells. It is sometimes called the vitelline sac, which should not be confused with the vitelline membrane of the egg. Embryoblast and Trophoblast Development smear, showing many intracellular bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology stained in red by Giemsa stain Giemsa stain Borrelia
Image: “10955” by CDC/ Billie Ruth Bird. License: Public DomainGiemsa-stained R. rickettsii in the cells of a tick
Image: “Rickettsia rickettsii” by CDC. License: Public DomainR. rickettsii | R. prowazekii | R. typhi | R. akari | |
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Vector | Hard ticks 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. Coxiella/Q Fever (Ixodidae family): Dermacentor (dog tick), Amblyoma (wood tick) | Human lice (
Pediculus humanus corporis
Pediculus Humanus Corporis
Epidemic Typhus):
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Rat and cat flea bites | Mites 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. Scabies from mice |
Disease | Rocky Mountain spotted fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever (the most serious rickettsial disease) | Epidemic (louse-borne) typhus | Endemic typhus | Rickettsialpox (the least serious rickettsial disease) |
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Epidemiology:
Pathophysiology:
Clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor:
Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas:
Identification Identification Defense Mechanisms:
Characteristic spotted rash Rash Rocky Mountain Spotted Fever of Rocky Mountain spotted fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever: hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and wrist of an affected child
Image: “Rocky Mountain spotted fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever PHIL 1962 lores” by CDC. License: Public DomainEpidemic (louse-borne) typhus is now a rare disease.
Pathogenesis:
Clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor:
Brill-Zinsser disease Brill-Zinsser Disease Epidemic Typhus:
Rash Rash Rocky Mountain Spotted Fever in a patient with epidemic typhus Epidemic Typhus Epidemic typhus is a febrile illness caused by the obligate intracellular gram-negative bacterium, Rickettsia prowazekii. Epidemic typhus is also known as louse-borne typhus or jail fever, and its symptoms include high fever, headache, myalgias, dry cough, delirium, stupor, and rash. Epidemic Typhus
Image: “ Epidemic typhus Epidemic Typhus Epidemic typhus is a febrile illness caused by the obligate intracellular gram-negative bacterium, Rickettsia prowazekii. Epidemic typhus is also known as louse-borne typhus or jail fever, and its symptoms include high fever, headache, myalgias, dry cough, delirium, stupor, and rash. Epidemic Typhus Burundi” by D. Raoult, V. Roux, J.B. Ndihokubwayo, G. Bise, D. Baudon, G. Martet, and R. Birtles. License: Public DomainPainless, black, crusted eschar of rickettsialpox, which develops as the last stage of the typical rash Rash Rocky Mountain Spotted Fever (macules → papules → vesicles Vesicles Female Genitourinary Examination → crusts/eschars that heal without scarring Scarring Inflammation).
Image: “Rickettsialpox lesion” by Krusell A, Comer JA, Sexton DJ. License: Public Domain