A rickettsiosis is a disease caused by intracellular bacteria.
Cause
Rickettsioses can be divided into a
spotted fever
A spotted fever is a type of tick-borne disease which presents on the skin. They are all caused by bacteria of the genus '' Rickettsia''. Typhus is a group of similar diseases also caused by ''Rickettsia'' bacteria, but spotted fevers and typhus ...
group (SPG) and
typhus
Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...
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 "ricke ...
.
However,
scrub typhus
Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite '' Orientia tsutsugamushi'', a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.[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
Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...
, both endemic and epidemic,
Rocky Mountain spotted fever
Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally made up of small spots of bleedin ...
, 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 t ...
.
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 "ricke ...
'', but
scrub typhus
Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite '' Orientia tsutsugamushi'', a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.[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
Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mic ...
assays usually take 10–12 days to become positive. Research is indicating that swabs of
eschar
An eschar (; Greek: ''ἐσχάρᾱ'', ''eskhara''; Latin: ''eschara'') is a slough or piece of dead tissue that is cast off from the surface of the skin, particularly after a burn injury, but also seen in gangrene, ulcer, fungal infections, ...
s may be used for molecular detection of rickettsial infections.
Treatment
Doxycycline has been used in the treatment of rickettsial infection.
[Mobeen
Mobeen (Arabic: مبين; Persian: موبین) (also Mubeen, Mobin, Mubin) is a given name derived from an Arabic word (مبين), which is used as a poetic adjective in literature, speech and religious contexts. The name can be translated as 'di ...]