OVERVIEW

What is hydatid disease?

Hydatid disease, also known as echinococcosis, is a zoonotic disease caused by the larvae (hydatid cysts) of Echinococcus tapeworms parasitizing humans or other animals.

In humans, the larvae most commonly parasitize the liver, known as hepatic hydatid disease. Additionally, the larvae can infect other organs such as the lungs or brain. Symptoms vary depending on the affected area. With timely treatment, complete surgical removal of the lesions, and prescribed antiparasitic medication, most patients can be cured.

Is hydatid disease caused by all Echinococcus tapeworms?

Globally, four species of Echinococcus tapeworms can cause hydatid disease. Among them, Echinococcus granulosus and Echinococcus multilocularis are the primary pathogens in China, with E. granulosus being more common, accounting for over 95% of cases.

E. granulosus infection is also called cystic echinococcosis or unilocular hydatid disease, while E. multilocularis infection is known as alveolar echinococcosis.

Which regions in China have high incidence of hydatid disease?

High-risk areas in China are mainly concentrated in alpine meadow regions, cold and arid pastoral or semi-pastoral zones, including Xinjiang, Qinghai, Gansu, Ningxia, Tibet, Inner Mongolia, Shaanxi, Shanxi, and northern Sichuan.

Are there many hydatid disease patients? Who is most susceptible?

A 2004 national survey on major parasitic diseases in China revealed over 380,000 cases in the northwest. High-risk groups include those engaged in animal husbandry, slaughtering, hunting, or farming.

Why is hydatid disease called "worm cancer"? Is the mortality rate high?

Hydatid disease is colloquially called "worm cancer" due to its insidious onset, difficulty in treatment, and risk of recurrence. While cystic echinococcosis has a good prognosis, most alveolar echinococcosis cases cannot be surgically cured, resulting in a high mortality rate—earning its reputation as "worm cancer."

SYMPTOMS

What are the symptoms and manifestations of cystic echinococcosis in hydatid disease?

• Cystic echinococcosis is often clinically latent and asymptomatic. Patients are usually diagnosed incidentally during physical examinations years after infection, and some may even remain asymptomatic for life.

• Since hepatic echinococcosis is the most common, the most frequent clinical symptoms include dull pain in the right upper abdomen and bloating. Echinococcosis in other organs may cause symptoms related to the affected organ, such as cough, sputum production, and hemoptysis in pulmonary echinococcosis, or hemiplegia and epilepsy in cerebral echinococcosis.

• Long-standing or large cysts may lead to weight loss, emaciation, and anemia.

• Pediatric patients may exhibit developmental delays and intellectual disabilities, but these conditions can improve rapidly after treatment.

• In addition to its own symptoms, hepatic echinococcosis can cause a series of complications, such as fever and liver abscess due to bacterial invasion, bile duct obstruction due to cyst compression (leading to jaundice, bloating, and loss of appetite), or anaphylactic shock due to cyst rupture.

What are the symptoms and manifestations of alveolar echinococcosis in hydatid disease?

Alveolar echinococcosis resembles malignant tumors, with cysts growing rapidly. Patients often experience early symptoms such as weight loss, anemia, and right upper abdominal pain, typical of hepatic echinococcosis. Additionally, Echinococcus larvae can metastasize to other organs (e.g., lungs, brain) via blood or lymphatic circulation, leading to symptoms like hemoptysis or epilepsy.

CAUSES

How is echinococcosis transmitted?

Contact with water, food, or other items contaminated by parasite eggs, as well as soil, food, or water sources polluted by infected animal feces, or close contact with infected animals, can lead to the ingestion of eggs into the human digestive tract, causing infection. Direct infection can also occur through handling fox pelts.

Common infected animals include dogs, foxes, and wolves. Among them, dogs are the most common definitive host for Echinococcus granulosus, while foxes are the primary host for Echinococcus multilocularis.

What are the characteristics of cystic echinococcosis?

Cystic echinococcosis usually presents as isolated, localized lesions, most commonly in the liver. It rarely spreads within the liver or grows invasively, making treatment relatively easier with good outcomes. Most patients can recover after surgical intervention or antiparasitic drug therapy.

What are the characteristics of alveolar echinococcosis?

Alveolar echinococcosis tends to grow invasively, often leading to liver dysfunction, liver failure, and distant metastasis similar to malignant tumors. The cross-section of lesions is also difficult to distinguish from malignancies. Most patients cannot undergo curative surgery, resulting in a high mortality rate. Close follow-up and drug therapy are required.

DIAGNOSIS

How is hydatid disease diagnosed?

• Personal and medical history: The patient has a history of living or traveling in pastoral or endemic areas, with previous clinical symptoms such as right upper abdominal pain and bloating.
• Imaging examinations: Ultrasound is the most important diagnostic tool for hepatic hydatid disease, while CT and MRI can be used to detect hydatid disease in other locations.
• Laboratory tests: Detection of echinococcal antigens or antibodies in serum, though false positives and false negatives are common. Combining two or more different testing methods is often necessary, and positive results require further confirmation. Since antibodies may persist in the blood for months, laboratory tests have limited value in detecting postoperative recurrence or assessing treatment efficacy.

TREATMENT

Which department should I visit for hydatid disease?

General surgery, infectious diseases department, infection department, etc.

Can hydatid disease be cured?

After detecting hydatid disease, timely treatment, complete removal of the lesion, and taking antiparasitic drugs as prescribed by a doctor can cure most patients.

How is hydatid disease treated?

Surgical resection is the only radical treatment.

• For patients with hepatic hydatid disease, the lesion should be completely removed as much as possible while ensuring sufficient residual liver volume. For lesions that are too large to remove, liver transplantation may be considered.
• Surgery for cystic hepatic hydatid disease has good outcomes. Combined with subsequent medical treatment and follow-up, most patients can be cured.
• The resection rate for alveolar hepatic hydatid disease is relatively low, only 10%–60%, with a high risk of postoperative recurrence. Some international reports suggest that liver transplantation yields better outcomes than partial hepatectomy for treating alveolar hepatic hydatid disease.
• For patients unsuitable for surgery or those with incomplete resection or recurrence, high-dose mebendazole or albendazole can be administered for drug treatment. Most patients can also achieve the goal of controlling disease progression and improving quality of life.

DIET & LIFESTYLE

What should hydatid disease patients pay attention to after treatment?

Take medication on time as directed by the doctor and attend regular follow-up examinations. In daily life, wash hands before meals, avoid drinking untreated water or raw milk, and refrain from eating undercooked meat.

PREVENTION

How to prevent echinococcosis?

• Strengthen health education in endemic and pastoral areas, and enhance personal protection for those engaged in slaughtering, herding, and hunting.
• Develop good hygiene habits in endemic and pastoral areas to prevent "disease entering through the mouth." Wash hands before meals, avoid drinking unboiled water or raw milk, and do not consume undercooked meat.
• Administer regular deworming medication to herding dogs. Avoid contact with wild foxes.

Can close contacts of echinococcosis patients become infected?

Daily contact with echinococcosis patients does not lead to infection.

Humans are not the definitive host of Echinococcus tapeworms. The larvae cannot develop into adult tapeworms in humans, and humans do not shed eggs. Moreover, routine contact with patients does not expose others to infectious protoscoleces.

However, healthcare workers may be exposed to infectious hydatid cyst fluid during surgical procedures for hepatic echinococcosis, so occupational protection is essential.