Typhus fevers: Difference between revisions
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==Treatment== | ==Treatment== | ||
Treatments for most rickettsial illnesses are similar and include administration of appropriate antibiotics (e.g., tetracyclines, chloramphenicol, azithromycin, fluoroquinolones, and rifampin) and supportive care. Treatment should usually be given empirically prior to disease confirmation, and the particular antimicrobial agent and the length of treatment are dependent upon the disease and the host. No licensed vaccines for prevention of rickettsial infections are commercially available in the United States. | Treatments for most rickettsial illnesses are similar and include administration of appropriate antibiotics (e.g., [[tetracyclines]], [[chloramphenicol]], [[azithromycin]], [[fluoroquinolones]], and [[rifampin]]) and supportive care. Treatment should usually be given empirically prior to disease confirmation, and the particular antimicrobial agent and the length of treatment are dependent upon the disease and the host. No licensed vaccines for prevention of rickettsial infections are commercially available in the United States. | ||
==Prevention== | ==Prevention== | ||
Revision as of 01:35, 7 August 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Many species of Rickettsia can cause illnesses in humans. The term “rickettsiae” conventionally embraces a polyphyletic group of microorganisms in the class Proteobacteria, comprising species belonging to the genera Rickettsia, Orientia, Ehrlichia, Anaplasma, Neo-rickettsia, Coxiella, and Bartonella.
Classification
- Epidemic typhus
- Trench fever
- Murine typhus
- Cat-Flea rickettsiosis
- Scrub typhus
- Tick-Borne rickettsioses
- Rickettsialpox
- Anaplasmosis
- Ehrlichiosis
- Q Fever
- Cat-Scratch disease
- Oroya fever
Pathophysiology
Rickettsial agents are usually not transmissible directly from person to person except by blood transfusion or organ transplantation, although sexual and placental transmission has been proposed for Coxiella. Transmission generally occurs via an infected arthropod vector or through exposure to an infected animal reservoir host. Transmission
| Type of Infection | Spread |
| Epidemic typhus | Body louse |
| Trench fever | Body louse |
| Murine typhus | Flea infested rats |
| Cat flea rickettsioses | Flea infested dogs and cats |
| Scrub typhus | Mites |
| Tick borne rickettsiosis | Ticks |
| Rickettsialpox | Mites |
| Anaplasmosis | Ixodes tick |
| Ehrlichiosis | Lone star tick |
| Q fever | Infected veterinary animals |
| Cat scratch disease | Infected cats |
| Oroya fever | Sandflies |
Risk Factors
- Travelers
- Patients on prosthetic heart valve
- Immunocompromised
Natural History , Complications and Prognosis
The clinical severity and duration of illnesses associated with different rickettsial infections vary considerably, even within a given antigenic group. Rickettsioses range in severity from diseases that are usually relatively mild (rickettsialpox, cat scratch disease, and African tick-bite fever) to those that can be life-threatening (epidemic and murine typhus, Rocky Mountain spotted fever, scrub typhus and Oroya fever), and they vary in duration from those that can be self-limiting to chronic (Q fever and bartonelloses) or recrudescent (Brill-Zinsser disease). Most patients with rickettsial infections recover with timely use of appropriate antibiotic therapy. Travelers may be at risk for exposure to agents of rickettsial diseases if they engage in occupational or recreational activities which bring them into contact with habitats that support the vectors or animal reservoir species associated with these pathogens.
Diagnosis
A diagnosis of rickettsial diseases is based on two or more of the following:
- clinical symptoms and an epidemiologic history compatible with a rickettsial disease,
- the development of specific convalescent-phase antibodies reactive with a given pathogen or antigenic group,
- a positive polymerase chain reaction test result,
- specific immunohistologic detection of rickettsial agent,
- isolation of a rickettsial agent. Ascertaining the likely place and the nature of potential exposures is particularly helpful for accurate diagnostic testing.
Symptoms
Clinical presentations of rickettsial illnesses vary, but common early symptoms include
Illnesses resulting from infection with rickettsial agents may go unrecognized or are attributed to other causes. Atypical presentations are common and may be expected with poorly characterized nonindigenous agents.
Laboratory Findings
Appropriate samples for examination by specialized reference laboratories should be obtained.
- Antibody titers
- Immunohistologic assessment
- Isolation of rickettsial agent
- Polymerase chain reaction(PCR] may be done
Treatment
Treatments for most rickettsial illnesses are similar and include administration of appropriate antibiotics (e.g., tetracyclines, chloramphenicol, azithromycin, fluoroquinolones, and rifampin) and supportive care. Treatment should usually be given empirically prior to disease confirmation, and the particular antimicrobial agent and the length of treatment are dependent upon the disease and the host. No licensed vaccines for prevention of rickettsial infections are commercially available in the United States.
Prevention
With the exception of the louse-borne diseases described above, for which contact with infectious arthropod feces is the primary mode of transmission (through autoinoculation into a wound, conjunctiva, or inhalation), travelers and health-care providers are generally not at risk for becoming infected via exposure to an ill person. Limiting exposures to vectors or animal reservoirs remains the best means for reducing the risk for disease. Travelers should be advised that prevention is based on avoidance of vector-infested habitats, use of repellents and protective clothing, prompt detection and removal of arthropods from clothing and skin, and attention to hygiene.