**2.2.3 Polycystic echinococcosis (PE)**

Forms of human polycystic echinococcosis (PE) are caused by *E. vogeli* and *E. oligarthrus*, which are confined in their distribution to Latin American countries.

Metacestode of *E. vogeli* is characterized by its polycystic form filled with liquid with a tendency to form conglomerates with multiples small spaces inside. The most affected organ in the intermediate host is the liver. Metacestode of *E. oligarthrus* is similar to *E. vogeli* but the division in secondary spaces is less frequent and the laminar membrane is significantly thinner.

Wild and domestic dogs as definitive hosts and paca (*Cuniculus paca*) as intermediate host participate in the life-cycle of *E. vogeli*. Polycystic echinococcosis due to *E. vogeli* has been communicated in the majority of the countries belonging to the neotropical region of America; including Panama, Colombia, Argentina, Ecuador, Brasil, Bolivia and Venezuela.

*E. oligarthrus* is the unique *Echinococcus* specie that uses felids as definitive hosts. Infections naturally acquired have been demonstrated affecting pumas, jaguars, and other wild felids.

### **2.2.3.1 Polycystic echinococcosis due to** *E. vogeli*

Clinical and radiological presentation is very similar to infection with multiple cysts of *E. granulosus*, and differential diagnosis depends on isolation of protoscoleces and morphological hook characteristics (D'Alessandro, 1997). Immunodiagnosis using a purified antigen of *E. vogeli* allowed discrimination between cases of PE and CE, but differentiation between PE and AE was not always possible (Gottstein, 1995). Albendazole with doses of 10 mg/kg/day has been used for chemotherapy in six cases with success of treatment in four and improvement in two (D'Alessandro, 1997).

#### **2.2.3.2 Polycystic echinococcosis due to** *E. oligarthrus*

Only three human cases have been reported to date, two orbital in Venezuela and Surinam and one cardiac in Brazil with 2 cysts (1.5 cm diameter) (D'Alessandro, 1997). The diagnosis was based on morphology of protoscolex hooks.
