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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Infectious Disease

Biology & Transmission: How Do You Get Hydatid Disease?

At a Glance

Humans contract Cystic Echinococcosis (hydatid disease) by accidentally ingesting microscopic tapeworm eggs from contaminated dog feces, unwashed produce, or water. Because humans are dead-end hosts, you cannot transmit the infection to family members or others.

Understanding how you contracted Cystic Echinococcosis (CE) is often the first step in moving past the shock of the diagnosis. It is important to know that humans are not a natural part of the parasite’s life cycle; rather, we are “accidental” participants in a cycle that usually involves dogs and livestock [1][2].

The Transmission Cycle

The parasite responsible for CE is a tiny tapeworm called Echinococcus granulosus. Its life cycle involves two main types of hosts:

  • The Definitive Host (Dogs): The adult tapeworm lives in the intestines of dogs and other canines [1]. These animals pass microscopic eggs in their feces [3].
  • The Intermediate Host (Livestock): Sheep, cattle, goats, and pigs accidentally swallow these eggs while grazing on contaminated grass [4]. Inside these animals, the eggs hatch into larvae and form hydatid cysts in organs like the liver or lungs [1]. The cycle is completed when a dog eats the organs of an infected animal containing these cysts [1].

Why Humans Are “Dead-End” Hosts

Humans become infected through the fecal-oral route [3]. This typically happens by touching a dog whose fur is contaminated with microscopic eggs and then touching your mouth, or by eating unwashed vegetables or drinking water contaminated with dog feces [5][3].

Practicing strict hand washing, especially after petting dogs, handling livestock, or before eating, is a crucial preventative measure to stop this transmission [5][6].

Once inside a human, the eggs hatch and form cysts, just as they do in sheep or cattle [7]. However, because dogs do not eat humans, the parasite’s life cycle stops there [2]. This means:

  • Humans are “dead-end” hosts: The parasite cannot complete its life cycle through us [2][8].
  • You cannot transmit it to others: You cannot pass this infection to your family, friends, or coworkers [3][5]. The eggs that cause infection only come from the feces of an infected canine, not from a person with a cyst [3].

Common Diagnostic Confusion

Because a hydatid cyst is a fluid-filled sac, it can look very similar to other medical conditions on an imaging scan. Doctors must carefully distinguish it from:

  • Simple Cysts: These are common, non-parasitic, and usually harmless fluid-filled sacs that often require no treatment [9][10].
  • Abscesses: These are pockets of infection (usually bacterial) that can look like a cyst but often cause fever and acute pain [9][11].
  • Tumors or Neoplasms: Both benign (non-cancerous) and malignant (cancerous) growths can sometimes mimic the appearance of hydatid disease [3][12].

CE vs. Alveolar Echinococcosis (AE)

It is also vital to differentiate CE from its more aggressive relative, Alveolar Echinococcosis (AE), caused by Echinococcus multilocularis [13].

  • CE (Cystic): Usually forms a single, well-defined, bladder-like cyst with a clear wall [1][3].
  • AE (Alveolar): Behaves more like a malignant tumor. It has an “infiltrative” nature, meaning it grows into surrounding tissues and can spread (metastasize) to other organs [14][15].

Your medical team uses specific radiological features and sometimes blood tests for biomarkers to ensure they are treating the correct form of the disease [16][17].

Back to Home Page

Common questions in this guide

Can I pass hydatid disease to my family members?
No, you cannot pass this infection to your family, friends, or anyone else. Humans are considered "dead-end" hosts, meaning the parasite cannot complete its life cycle and spread from a person to another person.
How do humans get Cystic Echinococcosis?
Humans typically become infected by accidentally ingesting microscopic tapeworm eggs. This usually happens by petting a dog carrying the eggs and then touching your mouth, or by eating unwashed produce and drinking contaminated water.
How is a hydatid cyst different from a simple cyst?
A simple cyst is a common, non-parasitic fluid-filled sac that is usually harmless and rarely needs treatment. A hydatid cyst is caused by a tapeworm parasite and requires specific medical evaluation and care. Doctors use detailed imaging scans to tell them apart.
What is the difference between CE and AE?
Cystic Echinococcosis (CE) typically forms a single, well-defined cyst. Alveolar Echinococcosis (AE) is a more aggressive form of the parasite that behaves like a tumor, growing into surrounding tissues and potentially spreading to other organs.
How can I prevent getting hydatid disease?
The most effective way to prevent infection is by practicing strict hand washing. Always wash your hands thoroughly after petting dogs, handling livestock, and before eating or preparing food.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my imaging, how can you be sure this is a hydatid cyst and not a simple cyst or an abscess?
  2. 2.Does my cyst show features of Cystic Echinococcosis (E. granulosus) or Alveolar Echinococcosis (E. multilocularis)?
  3. 3.What specific features on my ultrasound or CT scan rule out a tumor or neoplasm?
  4. 4.Given my history, should we consider testing for any other parasites that might mimic these findings?

Questions For You

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References

References (17)
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    Hepatic echinococcosis: A review.

    Bhutani N, Kajal P

    Annals of medicine and surgery (2012) 2018; (36()):99-105 doi:10.1016/j.amsu.2018.10.032.

    PMID: 30450204
  2. 2

    Combined cross-sectional and case-control study on Echinococcus multilocularis infection in pigs in Switzerland.

    Meyer A, Olias P, Schüpbach G, et al.

    Veterinary parasitology: X 2020; (4()):100031 doi:10.1016/j.vpoa.2020.100031.

    PMID: 32984810
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    Hydatid Disease: A Radiological Pictorial Review of a Great Neoplasms Mimicker.

    Alshoabi SA, Alkalady AH, Almas KM, et al.

    Diagnostics (Basel, Switzerland) 2023; (13(6)) doi:10.3390/diagnostics13061127.

    PMID: 36980435
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    First molecular identification of hydatid tapeworm Echinococcus granulosus sensu lato G6/G7 in Ecuador.

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    PMID: 28131366
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    Prevalence of cystic echinococcosis among livestock in pastoral and agro-pastoral areas in Uganda.

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    Parasitology 2024; (151(1)):68-76 doi:10.1017/S0031182023001154.

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    Immunology of cystic echinococcosis (hydatid disease).

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    British medical bulletin 2017; (124(1)):121-133 doi:10.1093/bmb/ldx033.

    PMID: 29253150
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    Agranulocytosis leads to intestinal Echinococcus multilocularis oncosphere invasion and hepatic metacestode development in naturally resistant Wistar rats.

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    Parasitology 2021; (148(1)):53-62 doi:10.1017/S0031182020002012.

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    Uncommon Locations of Cystic Echinococcosis: A Report of 46 Cases from Southern Iran.

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    Popliteal Echinococcosis: A Long Journey from the Liver.

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    Giant Calcified Hepatic Hydatid Cyst: A Case Report.

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    Pitfalls in the surgical treatment of undiagnosed lung lesions and cystic pulmonary hydatidosis.

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    Expression and serodiagnostic efficacy of a novel echinococcosis-specific recombinant fusion antigen rAgB8/1-Em18-Eg95.

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    A Case of Alveolar Echinococcosis Presenting as Cerebral and Spinal Intradural Metastases.

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This page provides educational information on the transmission and biology of Cystic Echinococcosis. It does not replace professional medical advice; please consult an infectious disease specialist for diagnosis and treatment.

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