RICKETTSIOSES-1.pptx - RICKETTSIOSES By Martin Osodo(MBChB...

RICKETTSIOSES
By Martin Osodo(MBChB Y3)

•
Rickettsioses are a group of diseases generally caused by species
of Rickettsia.
•
Genera;

Rickettsia

Orientia

Coxiella

Ehrlichia

Rochalimaea

Anaplasma,

Neorickettsia

They are small, Gram-negative, aerobic, coccobacilli that are obligate
intracellular parasites of eucaryotic cells (residing in the cytoplasm or
within the nucleus).

•
mammals and arthropods are natural hosts,
but humans are incidental hosts(i.e
transmitted to humans by arthropods).
•
3 major groups based on clinical
characteristics of disease:
1. spotted fever group;
2. typhus group;
3. scrub typhus group .

Spotted fever group

Rocky Mountain spotted fever

Rickettsialpox

Boutonneuse fever
Typhus group

Louse-borne (epidemic) typhus

Brill-Zinsser disease (relapsing louse-borne typhus)

Murine (endemic or flea-borne) typhus
Scrub typhus group (Tsutsugamushi disease).

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Pathogenesis
–
Arthropod bite
–
Invade endothelial cells, destroy endothelial cells
–
Inflammatory cells accumulate/ blood leakage
hence red spots and rashes.
–
Release organisms reinfection

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Increased vascular permeabilty>>edema(life
threatenind in brain amd lungs)>>>low blood
volume>>>hypotension>>>decreased
perfusion of organs>>> organ dysfunction(e.g
acute renal failure, prerenal azotemia)

Spotted fever group
•
Rocky Mountain spotted fever
–
Agent: R. rickettsii
–
Vector: ticks
–
Distribution:Western Hemisphere, including most
of the US (except Maine, Hawaii, and Alaska);
Central and South America
–
Clinical features: rash>>>petechial;vasculitis (skin,
subcutaneous tissues, CNS, lungs, heart, kidneys,
liver, or spleen).