Echinococcosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Kalsang Dolma, M.B.B.S.[3]
Overview
Echinococcosis is a potentially fatal parasitic disease that can affect many animals, including wildlife, commercial livestock and humans. The disease results from infection bytapeworm larvae of the genus Echinococcus - notably E. granulosus, E. multilocularis, and Echinococcus vogeli.
Historical Perspective
Goeze accurately described the echinococcosis cysts and the tapeworm heads for the first time in 1782. Later Batsch gave a detailed description of E. granulosus in 1786. Rudolf Leuckart identified E. multilocularis for the first time in 1863.
Classification
Echinoccocosis is classified based on the site of infection and the type of tape worm causing the infection into cystic echinococcosis and alveolar echinococcosis. It can also be classified based on the ultrasound findings and appearance.
Pathophysiology
The transmission of infection from the definite host to the intermediate host is by ingestion of embryonated eggs passed in the feces. Once the eggs are ingested they hatch in the small intestine and develop into onchospheres. There oncospheres reach various organs by migration through the vascular system and develop into cysts producing protoscolices. The definitive host is infected by ingestion of the organs infected with the cysts. After ingestion of the cysts they evaginate and invade the intestinal mucosa and develop into adult worms.
Causes
Human echinococcosis (hydatidosis, or hydatid disease) is caused by the larval stages of cestodes (tapeworms) of the genus Echinococcus. Echinococcus granulosus causes cystic echinococcosis (CE), the form most frequently encountered; E. multilocularis causes alveolar echinococcosis (AE); E. vogeli causes polycystic echinococcosis; and E. oligarthrus is an extremely rare cause of human echinococcosis. '''Echinococcus'' 'eggs contain an embryo that is called an oncosphere or hexcanth. From the embryo released from an egg develops a ''hydatid cyst'', which is able to survive within organs for years. ''Echinococcus'' adult worms develop from protoscolices and are typically 6mm or less in length and have a scolex, neck and typically three proglottids.
Differentiating Echinococcosis from other Diseases
Cystic echinococcosis must be differentiated from other diseases presenting with similar features of right sided abdominal pain such as pyogenic liver abscess and amebic liver abscess and fungal liver abscess.
Epidemiology and Demographics
Risk Factors
Natural History, Complications and Prognosis
Diagnosis
History and symptoms
Persons with echinococcosis often remain asymptomatic. The clinical presentation of echinococcosis infection depends upon the site of the cysts and their size. The cysts are mainly found in the liver and lungs but can also appear in the brain, eyes, spleen, kidneys, heart, bone, and central nervous system. Cyst rupture is most frequently caused by trauma and may cause mild to severe anaphylactic reactions, even death, as a result of the release of cystic fluid.[1]
Physical examination
Physical examination of a patient with echinococcosis may reveal hypotension, elevated temperature, jaundice, hepatomegaly and abdominal tenderness.
Laboratory findings
In the patients suspected of echinococcosis enzyme-linked immunosorbent assay (ELISA) and the indirect hemagglutination test are highly sensitive procedures for the initial screening of serum for cystic echinococcosis. In case of alveolar echinococcosis serologic test results are usually positive at high titers. Comparing a patient’s titers with both purified-specific and shared antigens permits the serologic discrimination between patients infected with E. multilocularis and those infected with E. granulosus.
X Ray
Radiography imaging permits the detection of hydatid cysts in the lungs; however, in other organ sites, calcifications can be visualized. On a chest Xray, cysts are well defined as a rounded mass with uniform density.[2]
Ultrasound
The imaging technique of choice for cystic echinococcosis is ultrasonography since it is not only able to visualize the cysts in the body’s organs [3] but it is also inexpensive, non-invasive and gives instant results.[4] Ultrasonography has been widely used for screening, clinical diagnosis, and monitoring of treatment of liver and intraabdominal cysts.
CT scan
The imaging technique of choice for cystic echinococcosis is ultrasonography since it is not only able to visualize the cysts in the body’s organs [3] but it is also inexpensive, non-invasive and gives instant results.[5] Ultrasonography has been widely used for screening, clinical diagnosis, and monitoring of treatment of liver and intraabdominal cysts.
MRI
Both MRI and CT scans can and are often used although an MRI is often preferred to CT scans when diagnosing cystic echinococcosis since it gives better visualization of liquid areas within the tissue.
Other imaging findings
Other diagnostic studied
Treatment
Medical therapy
Surgery
Primary prevention
Secondary prevention
References
- ↑ Chakraborty R, Smouse PE (1988). "Recombination of haplotypes leads to biased estimates of admixture proportions in human populations". Proc. Natl. Acad. Sci. U.S.A. 85 (9): 3071–4. PMC 280145. PMID 3362862.
- ↑ Junghanss T, da Silva AM, Horton J, Chiodini PL, Brunetti E (2008). "Clinical management of cystic echinococcosis: state of the art, problems, and perspectives". Am. J. Trop. Med. Hyg. 79 (3): 301–11. PMID 18784219.
- ↑ 3.0 3.1 Brunetti, Enrico, Peter Kern , and Dominique Vuitton. "Expert Consensus for the Diagnosis and Treatment of Cystic and Alveolar Echinococcosis in Humans." Acta Tropica (2009). Web. 24 February 2010.
- ↑ Macpherson, Calum N.L., Ruth Milner, and . "Performance Characteristics and Quality Control of Community Based Ultrasound Surveys for Cystic and Alveolar Echinococcosis." Acta Tropica 85. (2003): 203-09. Web. 24 February 2010.
- ↑ Macpherson, Calum N.L., Ruth Milner, and . "Performance Characteristics and Quality Control of Community Based Ultrasound Surveys for Cystic and Alveolar Echinococcosis." Acta Tropica 85. (2003): 203-09. Web. 24 February 2010.