Source: <http://ryoko.biosci.ohio-state.edu/~parasite/echinococcus.html>
|
Source: <http://ryoko.biosci.ohio-state.edu/~parasite/echinococcus.html> |
| Echinococcosis is a parasitic cestode of the phylum platyhelminthes, commonly referred to as tapeworms. There are three forms that occur in humans: cystic (E. granulosus), alveolar (E. multilocularis), and polycystic (E. vogeli and E. oligarthrus) which is rare. The cystic strain is the most common and is known as Hydatid Disease, though all strains have similar life cycles and clinical presentations but affect different organs. |
Source: TMCR <http://tmcr.usuhs.mil/tmcr/chapter3/geographic.htm>
Global distribution of E. granulosa (black) and E. multilocularis (x
Hydatid disease unlike most parasitic diseases is more prevalent in the northern hemisphere. Human infection is most common in sheep-raising countries such as Australia and New Zealand, throughout England and Europe, the Middle East, Russia, Northern China, and Japan. In the Americas the disease is especially prevalent in the Southern Cone countries such as Argentina, Uruguay and Chile, and also occurs in Alaska and Canada. Alveolar hydatid disease (E. multilocularis) is a less widespread disease that occurs in countries with larger distributions of the reservoir hosts dogs, wolves, foxes and cats. The disease is mainly prevalent in northern and central Europe, Alaska, and parts of Canada. The spread of Echinococcus infection depends on the presence of dogs and foxes as definitive hosts, susceptible intermediate hosts such as sheep, goats and swine, an environment that enables egg survival, and human populations living in close contact with domesticated animals. |
| Hydatid disease is caused by the larval stage of the parasite and can range from an asymptomatic infection to serious disease that can be fatal. Severity depends on the location and size of cysts. Symptoms occur when growing hydatid cysts cause pressure necrosis of the surrounding tissues: |
Organ affected |
Percentage of Cases |
Symptoms |
 |
|---|---|---|---|
Liver |
75% |
abdominal pain, hepatic mass, bile duct obstruction |
|
Lungs |
22% |
chest pain, cough, hemoptysis |
|
abdominal/pelvic cavity, spleen, kidney, heart |
6% |
k |
Infected liver with hydatid cysts Source: Mich Dept. Natural Resources <http://www.michigan.gov/dnr/0,1607,7-153-10370_12150_12220-117400--,00.html> |
| Leakage of fluid from the cyst (hyatid sand) causes eosinophilia. Rupture of a hydatid cysts as a consequence of trauma or surgery is very dangerous because it can cause anaphylactic shock, possible allergic reaction, and risk spreading hydatid sand which can give rise to new cysts throughout the body. |  |
Source: CDC <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Echinococcosis_il.htm> Hydatid Sand |
CDC: http://www.dpd.cdc.gov/dpdx/html/Echinococcosis.htm |
Stephanie Connolly, Junior, stephcon@stanford.edu |
