A rickettsiosis is a disease caused by intracellular bacteria.
Cause
Rickettsioses can be divided into a
spotted fever group (SPG) and
typhus group (TG).
In the past, rickettsioses were considered to be caused by species of
Rickettsia
''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickett ...
.
However,
scrub typhus is still considered a rickettsiosis, even though the causative organism has been reclassified from ''Rickettsia tsutsugamushi'' to ''
Orientia tsutsugamushi
''Orientia tsutsugamushi'' (from Japanese ''tsutsuga'' meaning "illness", and ''mushi'' meaning "insect") is a mite-borne bacterium belonging to the family Rickettsiaceae and is responsible for a disease called scrub typhus in humans. It is a ...
''.Examples of rickettsioses include
typhus, both endemic and epidemic,
Rocky Mountain spotted fever, and
Rickettsialpox
Rickettsialpox is a mite-borne infectious illness caused by bacteria of the genus ''Rickettsia'' (''Rickettsia akari''). Physician Robert Huebner and self-trained entomologist Charles Pomerantz played major roles in identifying the cause of the ...
.
Organisms involved include
Rickettsia parkeri
''Rickettsia parkeri'' (abbreviated ''R. parkeri'') is a gram-negative intracellular bacterium. The organism is found in the Western Hemisphere and is transmitted via the bite of hard ticks of the genus ''Amblyomma''. ''R. parkeri'' causes mild ...
.
Many new causative organisms have been identified in the last few decades.
Most are in the genus ''
Rickettsia
''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickett ...
'', but
scrub typhus is in the genus ''
Orientia
''Orientia'' is a genus of bacteria in family Rickettsiaceae. They are obligate intracellular, gram-negative bacteria found in insects and mammals. They are spread through the bites or feces of infected insects.
The genus comprises the species ...
''.
Diagnosis
No rapid laboratory tests are available to diagnose rickettsial diseases early in the course of illness, and
serologic assays usually take 10–12 days to become positive. Research is indicating that swabs of
eschars may be used for molecular detection of rickettsial infections.
Treatment
Doxycycline
Doxycycline is a broad-spectrum tetracycline class antibiotic used in the treatment of infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, Lyme disease, cholera, typhus, an ...
has been used in the treatment of rickettsial infection.
[Mobeen H Rathore">]
References
External links
*
{{infectious-disease-stub