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Table II.
Selected phenotypic differences between the insect and selected tick borne rickettsiae.
Rickettsial species | R. prowazekii | R. typhi | R. felis | R. rickettsii | R. conorii |
---|---|---|---|---|---|
Intranuclear growth | No | No | No | Yes | Yes |
Hemolytic activity | Yes | Yes | Yes | No | No |
Culture attributes: | |||||
plaque size (Vero) | Small | Small | Large | Large | Large |
Early escape before host cell death | No | Yes | Yes | Yes | Yes |
Escape via actin polymerization-derived motility (RickA) | No | No | Yes | Yes | Yes |
Persistence in humans or mammalian hostsa | Yes | Yes | NR | No (?) | No |
Maintenance in vectorb | TST only | TST;TOT | TST;TOT | TST; TOT | TST;TOT |
Major route of transmission to humans | Louse feces | Flea feces | Flea bite | Tick bite | Tick bite |
Plasmid(s) | No | No | Yes | No | No |
Type IV Pili | No | No | Yes | No | No |
Disease in humans: | |||||
Eschar | No | No | Yes/No | Rare | Yes |
Rash | Yes | Yes | Yes/No | Yes | Yes |
Fever | Yes | Yes | Yes | Yes | Yes |
Mortality Ratec | High | Low | NR | High | Mild |
a
NR = none reported; ? = Only one instance of R. rickettsii being recovered from a lymph node that was excised one year after the patient treatment and resolution of RMSF [30]. However, despite this exceptional case we are not aware of any instances of recrudescent RMSF like we have seen in Brill-Zinsser disease.