ملخص

RICKETTSIAL INFECTIONS

Typhus group :
Epidemic typhus (louse borne typhus)
Endemic typhus (flea borne typhus)
Scrub typhus (mite borne)

Spotted fever group :

Rocky Mountain spotted fever
Other tick borne typhus fevers

Multiply in capillary endothelial cells, producing skin, CNS, heart, lungs, kidneys and skeletal muscles lesions. Endothelial proliferation, associated with a perivascular reaction, thrombosis and purpura.

In epidemic typhus the brain is the target organ.

In scrub typhus the cardiovascular system and lungs are attacked.

Eschar is often found in tick- and Scrub typhus (mite borne)

Rocky Mountain spotted fever
Transmitted by tick bites
Clinical features: Fever , maculopapular measles-like Rash, bleeding , peripheral gangrene hepatosplenomegaly
Epidemic (louse-borne) typhus
Transmitted to Human body louse through its excreta by scratching.
Clinical features:
First Week
High fever, rigor, congested eyes, confusion, rash
Second Week
worsening symptoms, stupor , palpable spleen. The temperature falls rapidly and the patient recovers gradually.
In fatal cases , patient usually dies in the second week from toxaemia, cardiac or renal failure, or pneumonia.
Endemic (flea-borne) typhus
Humans are infected with the faeces or contents of a crushed flea
symptoms resemble those of a mild louse-borne typhus.
The rash may be scanty and transient.
Scrub typhus fever
transmitted by mites
Onset is usually sudden , headache, fever, malaise,
cough. Maculo-papular rash
generalised painless lymphadenopathy.
temperature falls by lysis on about the 12thday.
In severe infection Cardiac, renal failure and
haemorrhage may develop.


Management of the rickettsial diseases
all respond to tetracycline or chloramphenicol
Louse-borne and scrub typhus can be treated with asingle dose of doxycycline

Resistant strains of Scrub typhus fever

may need treatment with rifampicin

Nursing care is important, especially in epidemic typhus.

Sedation may be required for delirium
blood transfusion for haemorrhage
Diagnosis of rickettsial infection
clinical grounds and response to treatment.
The Weil-Felix
Species-specific antibodies
Differential diagnoses
include malaria, typhoid

Prevention Vector and reservoir control , Lice, fleas, ticks and mites need to be controlled with insecticides.

Q FEVER

caused by rickettsia-like organism organism Coxiella burnetii
Transmitted by inhalation of aerosolised particles
C. burnetii is its antigenic variation, called phase variation, from animals or humans, express phase I antigen and are very infectious In culture there is an antigenic shift to the phase II form, which is not infectious.
Clinical features
Fever, headache and chills; maculo-papular rash .Other presentations include pneumonia and hepatitis.
Chronic Q fever may present with osteomyelitis, encephalitis and endocarditis.
Diagnosis
Is usually serological.
isotype tests
phase-specific antigens.
Phase I and II IgM titres peak at 4-6 weeks.
In chronic infections IgG titres to phase I and II antigens may be raised.
Management
Doxycycline reduces fever duration.
Treatment of Q fever endocarditis requiring prolonged therapy with doxycycline and rifampicin or ciprofloxacin; even then, organisms are not always eradicated.
Valve surgery is often required.