Echinococcosis (Hydatid Disease)
A parasitic infection that forms cysts in the liver or lungs
Quick Facts
- Type: Parasitic (tapeworm) infection
- Common sites: Liver and lungs
- Source: Eggs from dog or livestock tapeworms
- Course: Slow-growing, often silent for years
Overview
Echinococcosis, also called hydatid disease, is an infection caused by the larval stage of Echinococcus tapeworms. People become infected by accidentally swallowing tapeworm eggs, usually from contact with infected dogs or contaminated food and water. The larvae travel through the body and form fluid-filled cysts, most commonly in the liver and lungs, that grow slowly over months to years.
There are two main forms. The more common cystic form tends to grow slowly and can often be treated. A rarer form behaves more aggressively and spreads through tissue like a tumor. Because cysts grow gradually, the infection may cause no symptoms for a long time. It is one of several parasitic infections spread between animals and people.
Symptoms
Symptoms depend on where the cysts form and how large they grow. Small cysts often cause no symptoms.
- Liver cysts: Pain or fullness in the upper right abdomen, nausea, and sometimes yellowing of the skin and eyes (jaundice)
- Lung cysts: Cough, chest pain, and shortness of breath, sometimes coughing up cyst fluid
- A feeling of pressure as a cyst enlarges and presses on nearby organs
- Fatigue and weakness
If a cyst bursts, it can cause a sudden severe allergic reaction and spread the infection. Sudden severe pain, difficulty breathing, or a severe allergic reaction needs emergency care.
Causes
Echinococcosis is caused by swallowing the eggs of Echinococcus tapeworms.
- Cystic echinococcosis: Linked to a tapeworm whose adult form lives in dogs, with sheep and other livestock as intermediate hosts.
- Alveolar echinococcosis: A rarer, more aggressive form linked to tapeworms of foxes and other wild canines.
Eggs are passed in animal feces and can contaminate soil, water, food, and animal fur. People become infected through hand-to-mouth contact after touching an infected animal or through contaminated food and water. Humans do not pass the infection directly to one another.
Risk Factors
- Close contact with dogs, especially working or herding dogs in rural areas
- Raising sheep or other livestock
- Living in or traveling to regions where the parasite is common
- Limited access to clean water and good sanitation
- Eating unwashed produce that may be contaminated with eggs
Diagnosis
Diagnosis relies on imaging to find cysts and tests to confirm the parasite.
- Ultrasound: A key test for liver cysts, showing their characteristic appearance.
- CT and MRI scans: Provide detailed images of cysts in the liver, lungs, and other organs.
- Blood tests: Detect antibodies to the parasite, supporting the diagnosis.
- Chest X-ray: Can reveal lung cysts as rounded shadows.
- Examination of cyst fluid or tissue: In some cases, samples obtained during a procedure help confirm the diagnosis.
Treatment
Treatment depends on the type, size, location, and number of cysts, and is best managed by specialists.
- Anti-parasitic medication: Drugs such as albendazole can shrink cysts and are used alone or with other treatments.
- Surgery: Removing cysts may be recommended, especially for large or complicated ones, taking care not to spill cyst contents.
- Puncture and drainage (PAIR): A needle technique used for certain liver cysts, combined with medication.
- Watchful monitoring: Some inactive cysts may simply be observed.
The aggressive alveolar form often needs long-term medication and specialized surgery, and in some cases lifelong treatment to keep it in check. Long-term follow-up with repeat imaging is important to watch for recurrence, because cysts can regrow if not fully treated. Care is usually coordinated by specialists experienced in parasitic diseases, who weigh the risks and benefits of each approach for the individual.
Prevention
- Wash hands thoroughly after handling dogs or livestock and before eating
- Deworm dogs regularly under veterinary guidance in endemic areas
- Avoid feeding raw animal organs to dogs
- Wash fruits and vegetables and use safe water
- Practice good farm and food hygiene in areas where the parasite is common
When to See a Doctor
See a doctor if you have persistent abdominal or chest discomfort, especially with a history of living around dogs and livestock in endemic areas. Seek emergency care if you experience:
- Sudden severe abdominal or chest pain
- Difficulty breathing
- Signs of a severe allergic reaction, such as widespread hives, swelling, or trouble breathing
- High fever with worsening pain
Frequently Asked Questions
How do people get echinococcosis?
People become infected by accidentally swallowing tapeworm eggs, usually after contact with infected dogs or through contaminated food, water, or soil. The eggs are passed in animal feces. The infection is not spread directly from person to person.
Where do hydatid cysts usually form?
The cysts most commonly form in the liver, followed by the lungs, but they can develop in other organs as well. Because they grow slowly, they may cause no symptoms for years until they become large enough to press on nearby structures.
Is echinococcosis dangerous?
It can be. Slow-growing cysts may cause organ damage over time, and a ruptured cyst can trigger a severe allergic reaction and spread the infection. The rarer alveolar form behaves aggressively. Early diagnosis and specialist treatment improve outcomes.
How is echinococcosis treated?
Treatment depends on the cyst type, size, and location and may include anti-parasitic medication, surgery, or a needle drainage procedure for certain liver cysts. Some inactive cysts are simply monitored. Care is best guided by specialists, with long-term follow-up.
Can echinococcosis be prevented?
Yes. Wash hands after contact with dogs or livestock, deworm dogs regularly in endemic areas, avoid feeding raw organs to dogs, wash produce, and use safe water. Good hygiene and animal control greatly reduce the risk.
References
- Centers for Disease Control and Prevention (CDC). Echinococcosis.
- World Health Organization (WHO). Echinococcosis.
- MedlinePlus, U.S. National Library of Medicine. Echinococcosis.