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 a ...

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 exposu ...

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 genus was n ...

. 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'' is a genus of bacteria in family Rickettsiaceae. They are obligate intracellular, gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gr ...

''. Examples of rickettsioses include

, 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 Petechial rash, made up of small s ...

, 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 ...

. 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 mil ...

. Many new causative organisms have been identified in the last few decades. Most are in the genus ''

'', 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 mi ...

assays usually take 10–12 days to become positive. Research is indicating that swabs of

eschar Eschar (; ; ; or ''an'' eschar) is a slough or piece of necrosis, dead tissue that is cast off from the surface of the skin, particularly after a Burn, burn injury, but also seen in gangrene, Ulcer (dermatology), ulcer, mycosis, fungal infection ...

s may be used for molecular detection of rickettsial infections.

Treatment

Doxycycline Doxycycline is a Broad-spectrum antibiotic, broad-spectrum antibiotic of the Tetracycline antibiotics, tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat pneumonia, bacterial p ...

has been used in the treatment of rickettsial infection.Mobeen H Rathore">

References

External links

* {{Authority control