|
Scrub typhus (tsutsugamushi
disease) is caused by Rickettsia (Orientia) tsutsugamushi.
Visit:
Epidemic Typhus
Infected mites
pass the infection transovarially to their larvae, which crawl to the
tips of vegetation and attach to passers-by rather than to the usual
host, the rat.
Image1
;
Image2
;
Image3
;
Image4
While feeding, the mite passes the rickettsia into the
skin.
Image5 ;
Image6 ;
Image7 ;
Image8.
A multiloculated vesicle forms at the inoculation site and ulcerates,
after which an eschar (a
dry scab or
slough formed on the skin
) forms.
As the eschar heals, there is a sudden
onset of headache, malaise, anorexia, weakness, and fever, followed by
pneumonia, a macular rash (on the trunk before the limbs),
lymphadenopathy, hepato-splenomegaly, and conjunctivitis.
Mild
infections may exhibit only fever.
The most common
gastrointestinal symptoms of scrub typhus patients included vomiting,
nausea, diarrhea and hametamesis or melena . Gastrointestinal signs
included hepatomegaly , jaundice and abdominal pain.
Since multiple serotypes exist and
cross-immunity is transient, recurrent infections are common.
Severe
infections are complicated by meningoencephalitis involving cranial
nerves, focal myocarditis, pneumonia and circulatory collapse.
Mortality rate range up to 30%.
The rickettsiae grow in the endothelial cells and produce a vasculitis.
There are “typhus nodules”,
but these are usually smaller than those of epidemic typhus.
Necrosis of the skin and
lymph nodes and a dense mononuclear infiltrate in the heart and lungs
are seen in severe cases.
|
