Life cycle Echinococcus spp.

Question 1

What are the 2 Echinococcus species?

Answer 1

Echinococcus granulosus –> Cystic echinococcosis

Echinococcus Multilocularis –> Alveolar echinococcosis

Question 2

What is the classification of Echinococcus spp.?

Answer 2

Helminth in the category of cestode

Question 3

How is Echinococcus spp. transmitted?

Answer 3

Animal feces that contaminate human food/water

Question 4

What are the steps of the Echinococcus granulosus lifecycle outside of the human host (in the dog)?

Answer 4

1. Gravid proglottid start producing eggs by sexual reproduction in the small intestine of dogs.
2. Sexual reproduction results in embryonated eggs in the feces of dogs.
3. The intermediate host & accidental host can ingest these eggs via the fecal-oral route. Humans mainly get infected by consumption of contaminated water or food or soil with fecal matter of an infected dog. In soil the eggs can stay viable for up to a year.

Question 5

What are the lifecycle steps of Echinococcus granulosus. lifecycle in the human host (and sheep)?

Answer 5

4. In the human host the eggs reach the stomach and release six-hooked oncospheres under the influences of digestive juices
5. 8 hours after ingestion, the oncospheres penetrate the intestinal wall after which they are extracellularly transported via bloodstream to the liver which is the first filter. About 70% of the oncospheres will stay in the liver. Next is transport via pulmonary circulation to the lungs which act as a second filter. Residual oncospheres go through the bloodstream to other organs like the spleen, kidney, heart, brain and eyes.
6. When oncospheres lodge into organs they develop into thick-walled hydratid cysts which is the larval stage of the parasite.
7. Within the cyst protoscolices and daughter cysts are produced through asexual budding. This takes probably more then 10 months. If the cyst raptures it may form other cysts in other parts of the human. Here the life cycle for humans stops. If the dog eats organs containing cysts of intermediate hosts the cycle continues.
8. After ingestion the protoscolices comes out of the cyst and attaches to the intestinal mucosa of the dog and develop into the adult stage of the parasite in 32-80 days
9. Life cycle restarts

Question 6

What type of life cycle does Echinococcus granulosus have?

Answer 6

Indirect life cycle

Question 7

What are the definitive host, intermediate host and/or accidental host for Echinococcus Granulosus?

Answer 7

Wild and domestic dogs: Definitive host
Sheep and goats: intermediate host
Human: accidental host

Question 8

What are the steps of the Echinococcus multicularis lifecycle outside of the human host (in the fox)?

Answer 8

1. Gravid proglottid start producing eggs by sexual reproduction in the small intestine of foxes.
2. Sexual reproduction results in embryonated eggs in the feces of foxes.
3. The intermediate host & accidental host can ingest these eggs via the fecal-oral route. Humans mainly get infected by consumption of contaminated water or food or soil with fecal matter of an infected fox.

Question 9

What are the lifecycle steps of Echinococcus multicularis lifecycle in the human host (and rodent)?

Answer 9

4. In the human host the eggs reach the stomach and release six-hooked oncospheres under the influences of digestive juices
5. 8 hours after ingestion, the oncospheres penetrate the intestinal wall after which they are extracellularly transported via bloodstream to the liver which they will stay.
6. When oncospheres lodge into the liver they develop into alveolar hydatid cysts and may disseminate other organs. The alveolar hydatid cyst have outward budding and numerous protoscolices develop within cysts In humans here the life cycle stops. If the foxes eat the rodent with alveolar hydatid cysts in the liver the life cycle continuous
7. After ingestion the protoscolices comes out of the cyst and attaches to the intestinal mucosa of the fox and develop into the adult stage of the parasite in 32-80 days
8. Life cycle restarts

Question 10

What type of life cycle does Echinococcus multicularis have?

Answer 10

Indirect life cycle

Question 11

What are the definitive host, intermediate host and/or accidental host for Echinococcus multicularis?

Answer 11

Foxes and canines: definitive host
Rodents: intermediate host
Humans: accidental host

Question 12

What are the symptoms of Echinococcus granulosus infection?

Answer 12

cystic echinococcosis –> Symptoms are slow and mostly asymptomatic. It depends on the location of the cysts. In humans the liver gets enlarged causing abdominal pain, increase hepatic blood pressure. Rupture of cysts causes fever, eosinophilia and potential anaphylactic shock.

Question 13

What are the symptoms of Echinococcus multilocularis infection?

Answer 13

alveolar echinococcosis –> symptoms: Progressively destroys affected organ tissues, discomfort, pain, weight loss, malaise, death

Question 14

What is the incubation time for Echinococcus spp. infection?

Answer 14

One to several years depending of the location of the cyst

Question 15

Where is Echinococcus granulosus endemic?

Answer 15

Everywhere but more frequently in rural, grazing areas where dogs ingest organs from infected animals

Question 16

Where is Echinococcus multilocularis endemic?

Answer 16

is only in the northern hemisphere including central and northern Europe, Central Asia, Northern Russia, Northern Japan, North-central USA, Northwestern Alaska and northwestern Canada.

Question 17

How is Echinococcus spp. diagnosed?

Answer 17

Based on anamnesis and clinical findings. Ultrasonography, CT or MRI are used to detect cysts.
Serological test can be used to detect antibodies