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The Black Death and Other Pandemics
Published in Scott M. Jackson, Skin Disease and the History of Dermatology, 2023
Epidemic typhus is an infection with a bacterium called Rickettsia prowazekii that is transmitted from person to person by the human body louse; the bacterium resides in the feces of the louse. This louse is slightly different from the lice that infest the hair of schoolchildren. Instead, it infests the body and garments of persons of poor health and hygiene living in unclean conditions. Scratching the louse bites causes the person to rub the louse feces into the wound, thus inoculating the body with the bacterium. The signs and symptoms of typhus include fever, chills, headache, rapid breathing, body aches, cough, nausea, vomiting, confusion, and a rash. The red, petechial rash starts on the torso and spreads outward to the arms and legs. The mortality rate of untreated epidemic typhus is anywhere from 10 to 60 percent; with antibiotics, the condition is uniformly survivable. Epidemic typhus should be distinguished from endemic (murine) typhus, which occurs worldwide and is spread by the rat flea, and typhoid, a febrile condition with red spots on the skin caused by S. typhi, made famous in the twentieth century by the life and career of “Typhoid Mary.”
Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Epidemic typhus transmitted between hosts by the body louse usually occurs in people living in unsanitary, crowded conditions. The disease is common in wartime. Lesions occur in the blood vessels of the heart and kidneys. Half of the patients die if untreated. Murine or endemic typhus is transmitted to humans by rat fleas and the disease is similar in nature, but milder than epidemic typhus. In Japan and Korea, humans may become accidental hosts for scrub typhus which is a congeni tally transmitted infection of mice. The host responds to rickettsial pathogens with a cell mediated immune reaction which destroys the infected cells.
Rocky Mountain Spotted Fever and Typhus Fever
Published in James H. S. Gear, CRC Handbook of Viral and Rickettsial Hemorrhagic Fevers, 2019
Serologic reactions — The currently available laboratory tests are quite adequate for the laboratory confirmation of the clinical diagnoses of RMSF or epidemic typhus. Two (and preferably more) serum samples taken during the 1st, 2nd, 3rd, and 4th to 6th weeks of illness are desired to demonstrate a titer rise of specific antibody during convalescence.
How relevant are in vitro culture models for study of tick-pathogen interactions?
Published in Pathogens and Global Health, 2021
Cristiano Salata, Sara Moutailler, Houssam Attoui, Erich Zweygarth, Lygia Decker, Lesley Bell-Sakyi
Most pathogenic Rickettsia spp. must be handled at BSL3, posing particular problems for studies on tick-bacterial interactions. Thus, as with highly pathogenic viruses, such as CCHFV, tick cell cultures are a useful substitute for live, intact ticks enabling a range of studies at the cellular and molecular level. Growth of Rickettsia rickettsii, causative agent of Rocky Mountain spotted fever in humans, was compared in tick (DALBE3 and IDE2) and mammalian cell lines at temperatures between 28°C and 34°C; raising the incubation temperature induced expression of rickettsial proteins in infected tick cells possibly associated with pathogenicity for mammalian cells [152]. In the absence of a louse cell line, tick (ISE6) and insect (Sf9) cell lines were used as models to analyze the effect on the proteome of Rickettsia prowazekii, causative agent of louse-borne human epidemic typhus, of growth in arthropod and mammalian environments [153]. In this study, rickettsial stress response proteins were upregulated in both arthropod cell lines and in a murine cell line, compared to levels in bacteria grown in hen egg yolk sacs, indicating possible limitations of cell cultures to model the in vivo situation. Nevertheless, comparison of siRNA expression profiles and coding transcriptomes of R. prowazekii grown in tick (AAE2) and human cell lines revealed novel siRNAs unique to arthropod cells and evidence for alternative transcription start sites used by rickettsial genes depending on the host cell environment [154]. A review of tropism in a range of pathogenic Rickettsia spp. found that the arthropod host range in vivo was reflected in the susceptibility of tick and insect cell lines in vitro, with tick-borne spotted fever group Rickettsia generally growing better in tick cells and insect-borne typhus group Rickettsia growing better in insect cells [155]. A recent study using both tick cell lines and experimentally infected vector ticks found that while two Rickettsia parkeri proteins, RickA and Sca2, played a role in actin polymerization in tick cells in vitro and in vivo, their absence did not affect patterns of R. parkeri dissemination in live, intact ticks [156].