Echinococcus

Question 1

Cystic echinococcosis - epidemiology

Answer 1

1 million affected worldwide

Worldwide distribution

Eradicated = NZ, Iceland, Tasmania

Question 2

Cystic echinococcosis - organism

Answer 2

Echinococcus granulosus
Adult = 3-8mm long
Eggs = 30-35um

Definitive host = canine
Intermediate host = sheep/goat

Question 3

Cystic echinococcosis - transmission

Answer 3

Ingestion of E granulosus eggs

Question 4

Echinococcus granulosus - cysts

Answer 4

Lifespan = 5-25 years
Growth rate = 0-5cm per year

2 membranes:
-Laminated membrane
-Germinal membrane producing protoscolices [parasite larvae that will only develop into adults in definitive host = canines]

Question 5

Cystic echinococcosis - clinical features

Answer 5

70% hepatic cysts
20% lung cysts
10% cysts elsewhere or in multiple sites

Can be asymptomatic or symptoms due to:
-Pressure effection - e.g. RUQ pain with capsular stretching
-Erosion into adjacent organs
-Rupture of cysts = can develop allergic rash, anaphylaxis

Question 6

Cystic echinococcosis - differential diagnosis

Answer 6

Cystic lesion in liver:
-Simple cyst
-Haematoma
-Abscess
-Cystadenoma
-Cystadenocarinoma
-Necrotic liver mets

Question 7

Cystic echinococcosis - diagnosis

Answer 7

Imaging:
-WHO classification CE1, 2, 3A/B, 4, 5
-Always do CXR to exclude lung involvement

Serology:
-Sensitivity 80-95% = depends on stage, organ and rupture. Non-viable cysts have low sensitivity
-Specificity 90% = may cross-react with other cestodes

Occasionally = diagnostic puncture

Question 8

Cystic echinococcosis - CE 1 cyst

Answer 8

Viable

Unilocular
Double line sign

Question 9

Cystic echinococcosis - CE 2 cyst

Answer 9

Viable

Multiseptated
Daughter cysts
Honey-comb
Rosette

Question 10

Cystic echinococcosis - CE 3A cyst

Answer 10

Transitional

Cyst with detached membranes
Waterlilly sign = floating membrane within pericyst

Question 11

Cystic echinococcosis - CE 3B cyst

Answer 11

Transitional

Daughter cysts in solid matrix

Question 12

Cystic echinococcosis - CE 4 cyst

Answer 12

Inactive

Cyst with heterogenous hypo/hyperechoic contents
No daughter cysts

Question 13

Cystic echinococcosis - CE 5 cyst

Answer 13

Inactive

Solid cyst with calcified wall

Question 14

Cystic echinococcosis - management

Answer 14

Depends on type, size and position of cyst

CE1/3A [both unilocular]:
<5cm = albendazole alone 3-6 months
>5cm = PAIR + albendazole

CE2/3B [both multilocular]:
Surgery or other percutaenous procedure with albendazole

CE4/5 [non-viable]:
Watch and wait

Question 15

Cystic echinococcosis - albendazole MOA

Answer 15

Blocks glucose uptake - kills cysts

Question 16

Cystic echinococcosis - albendazole use

Answer 16

Small CE1/3A cysts <5cm
Combined with surgery in CE1/3A >5cm and CE2/3B

Question 17

Cystic echinococcosis - albendazole SE

Answer 17

Hepatitis
Leucopenia
Alopecia [common and reversible]

Question 18

Cystic echinococcosis - praziquantel MOA

Answer 18

Prevents differentiation of protoscolex into a cyst
Does not penetrate mature cyst = may boost intra-cystic albendazole

Question 19

Cystic echinococcosis - praziquantel Use

Answer 19

Peri-operatively/procedure
Ruptured cysts

Question 20

Cystic echinococcosis - praziquantel SE

Answer 20

Nausea
Abdominal pain
Dizziness

Question 21

Cystic echinococcosis - PAIR

Answer 21

PAIR = puncture-aspiration-injection-reaspiration

-Only hepatic cysts
-Approach through liver parenchyma
-Aspirate tested for bilirubin - to assess if cyst continuous with biliary tree [do not inject scolicidal agent - ethanol or hypertonic saline]

Question 22

Cystic echinococcosis - PAIR use

Answer 22

CE1/3A cysts >5cm = give albendazole and praziquantel cover

Does not work if daughter cysts present

Question 23

Cystic echinococcosis - management of other cysts

Answer 23

Lung cysts:
-Surgery - followed by albendazole

Disseminated disease:
-Remove as many cysts as safely as possible
-Long term albendazole

Question 24

Cystic echinococcosis - control

Answer 24

Definitive host:
-Praziquantel treatment for dogs every 2 months

Community:
-Improved facilities at slaughter house - safe disposal of offal

Vaccine:
-EG95 vaccine for sheep

Question 25

Alveolar echinococcosis - organism

Answer 25

Echinococcus multilocularis

Question 26

Alveolar echinococcosis - epidemiology

Answer 26

Definitive hosts = foxes, domestic dogs

Intermediate host = small rodent - voles, marmot, lemmings, hamsters

Hyperendemicity:
-Parts of Germany, France - now expanding across Europe
-China

Question 27

Alveolar echinococcosis - incubation period

Answer 27

5-15 years

Question 28

Alveolar echinococcosis - clinical features

Answer 28

Primarily infects liver:
-RUQ pain, weight loss, jaundice, cholangitis
-Unlike CE = primary ifnection of other sites is rare

Infiltration of local organs = kidneys, adrenals, diaphragm, pleura, lungs

Can metastisises elsewhere = spleen, lungs, brain, bone

Question 29

Alveolar echinococcosis - diagnosis

Answer 29

Imaging [US/CT/MR/PET]:
-Infiltrate growth at margins of lesion
-Necrosis in centre of lesion
-Scattered calcification across lesion

Serology = confirmatory role

Biopsy = if unable to exclude malignancy

Question 30

Alveolar echinococcosis - management

Answer 30

Radical surgery with albendazole 2 years:
-Solitary liver lesions
-Resection margin

If hepatic complications - biliary obstruction with metastatic disease:
-Palliative surgery with lifelong albendazole

Metastatic disease but no hepatic complications:
-Lifelong albendazole

Liver transplant