Echinococcus

Background

• Cestode

Microbiology

• Echinococcus granulosus sensu stricto (G1 to G3), the major cause of cystic echinococcosis
• Echinococcus equinus (G4)
• Echinococcus ortleppi (G5)
• Echinococcus canadensis (G6 to G10)
• Echinococcus multilocularis, the major cause of alveolar echinococcosis
• Echinococcus vogeli, causes polycystic echinococcosis
• Echinococcus oligarthrus, extremely rare cause of human echinococcosis
• Echinococcus felidis
• Echinococcus shiquicus

Epidemiology

Species	Intermediate Hosts	Definitive Hosts	Distribution	Risk Factors
Echinococcus granulosus	sheep, cattle, pigs, camels, and goats	dogs and other canids	worldwide, with highest prevalence in Mediterranean, Russia, China, central Asia, north and east Africa, Australia, and South America	shepherds, exposure to feral dogs, slaughterhouse, unsanitary living conditions
Echinococcus multilocularis	rodents, domestic pigs, wild boars, dogs, monkeys	foxes, dogs, cars	mostly described in Europe and Asia, rare in North America
Echinococcus vogeli	rodents	bush dogs	Central and South America
Echinococcus oligarthus			Central and South America

Clinical Manifestations

• Any many present asymptomatically
• Rarely present with anaphylaxis from cyst rupture

Cystic Echinococcus

• Liver is the most common site (60%), followed by lung (20-30%)
• Can infect other sites including brain (10%)
• Can cause anaphylaxis when ruptures
• Can cause cholangitis

Alveolar Echinococcus

• Presents as liver cancer or metastases of unknown primary
• Liver involvement is present in 95% of cases

Diagnosis

• Generally made with ultrasound, possibly with MRI
• Serology can be helpful, but not necessarily that sensitive or specific
• Aspiration may be considered, but there is a risk of allergic reaction and a risk of secondary recurrence from leakages of hydatid fluid or protoscolices