Clinical Background
Echinococcosis infection is caused in humans by the larval stage of cestodes belonging to the genus Echinococcus.
Epidemiology
- Prevalence - endemic in Eurasia, South America and Africa
- In North America - most cases occur in immigrants from endemic countries
- Transmission - fecal-oral route
Organism
- 3 species - E. granulosus, E. multilocularis and E. vogeli
- The minute tapeworm, E. granulosus, develops in the intestine of dogs and other Canidae; prevalent where livestock are raised in association with dogs
- Its larval stage, the hydatid cyst, may be found in many mammals (cattle, sheep, hogs, man) when the eggs are ingested
- The adult worm is present only in dogs
- Cysts develop in intermediate hosts (human, sheep, cattle, goats)
- Hydatid cysts may form in any organ or tissue in humans; most commonly seen in the liver, lung and central nervous system
- In humans, the embryo develops slowly into hydatid cysts, reaching a diameter of 1 cm in 5 months or so; at the end of 10 or more years, they may contain liters of fluid
- The cysts vary considerably in size, depending on their age and location
- Cysts may or may not be able to expand freely depending on the location in the body
- In some cases, even a modest growth will result in serious impairment to the function of vital structures and even death
Clinical Presentation
- Hepatic disease is the most common presentation and may present as abdominal pain or a palpable right upper quadrant mass (about 2/3 of patients)
- Lungs are the second most common site of involvement of cysts
- Rupture of cysts leads to multifocal dissemination
Treatment
- Involves percutaneous aspiration, infusion of scolecoidal agents with reaspiration or surgery
Prevention
- Strict dog-control programs in endemic areas
