CONTINUED from page 9
GEOGRAPHIC DISTRIBUTION
- "cosmopolitan" parasite
- endemic in S. and central America, W. and S. Europe, Middle East, North Am, Russia, China, parts of Africa
- incidence varies widely (13 to 220/100,000)
PATHOPHYSIOLOGY
Organ localization:
- in human, metacestodes spread via blood
- also can spread directly by cyst rupture (e.g. into peritoneum, pleura,
bronchial tree, or biliary ducts)
- majority have single
- organ involvement with solitary cyst (involves more than one organ in
only 10-15% of cases)
- most common site is liver (~60%) -lung (~25%)
- others: muscle, bone, kidney, brain, spleen
Cyst
Characteristics
- size varies (1-15 cm usually)
- biggest ever contained 48 Litres of fluid!!!
- slow to moderate growth (1 to 5 cm per yr)
Three
layers:
a) Pericyst
- inflamed host tissue
b) Exocyst
- acellular "laminated" membrane, which is characteristic of
the disease
c) Endocyst
- inner cellular "germinal" (forms "protoscolices",
fertile cysts)
d) Inner debris
- "hydatid sand": hooks/scolices free
- floating in the fluid
CLINICAL
CHARACTERISTICS
-
highly variable
-
initial phase always asymptomatic
-
can remain asymptomatic indefinitely
-
symptoms arise 2ยก to:
-
cyst growth and compression
-
cyst rupture
-
secondary bacterial infection
-
immunological reactions (acute sensitivity reactions, with urticaria and
anaphylaxis possible if cyst ruptures)
Pulmonary
symptoms
- chest pain
- cough
- hemoptysis
- pneumothorax
- pleuritis
- sudden onset of cough and fever may be associated with cyst rupture
