Echinococcosis: causes, symptoms, diagnosis, and treatment

Echinococcosis, also known as hydatid disease, is divided into cystic echinococcosis (CE) and alveolar echinococcosis (AE), and is caused by Echinococcus granulosus and Echinococcus multilocularis, respectively.


Causes

The pathogen is Echinococcus granulosus and Echinococcus multilocularis. Both Echinococcus can complete their life cycle inside two types of mammal, and the adults are present in the small intestines of the definitive hosts.

The definitive hosts of Echinococcus granulosus are generally dogs and wolves, and the intermediate hosts are cattle, goats, and sheep.

The definitive hosts of Echinococcus multilocularis are generally foxes, dogs, and wolves, and the intermediate hosts are small mammals such as voles and rodents.

Echinococcosis occurs mostly in the liver, with 65.8% - 80% of cystic echinococcosis and 98% of alveolar echinococcosis, followed by lungs, with 14% - 18% of occurrence, succeeded by the abdominal cavity, pelvic cavity, spleen, kidney, brain, bones, muscles, subcutaneous tissue, orbit, mediastinum, mammary gland, parotid, thyroid, thymus, spermatic cord, myocardium, and pericardium.

Epidemiology

Source of infection

The most important source of infection is domesticated dogs, followed by wolves, foxes, and cats.

The route of transmission.

The disease is transmitted through the digestive tract.

High-risk persons

The high-risk persons include herders, farmers, dog breeders, hunters, and fur workers.


Signs and Symptoms

Hepatic cystic echinococcosis

There are usually no obvious symptoms in cystic echinococcosis in the early stage, and the asymptomatic period can last for several years to decades. Toxic and hypersensitivity reactions, such as anorexia, emaciation, anemia, developmental disabilities, urticaria, and angioedema, may occur in some patients. The corresponding symptoms are present after the enlarged cysts compress the parasitic organs and neighboring tissues.

The complications may be a result of compression, rupture, and infections of the cysts, and the main complications of hepatic cystic echinococcosis are jaundice, infection, stenosis, hemorrhage, biliary leakage, and allergic reactions. Secondary portal hypertension can occur.

Hepatic alveolar echinococcosis

There are not discomforts in patients with hepatic alveolar echinococcosis in the early stage, and there may be not obvious symptoms although the hepatic compensation increases. In the middle stage, sharply demarcated, rubbery, painless masses with smooth or nodular surfaces can be palpated, and the masses may be erroneously diagnosed as liver cancer. Obstructive jaundice occurs when the enlarged lesions erode the hepatic duct. The infections secondary to the colliquative, cavitary lesions may cause hepatic abscesses. Giant lesions erode most of the liver, so that portal hypertension may occur, and hepatic decompensation may be present. Finally, patients may die of hepatic failure, biliary infection, and metastasis to lungs, brain, and other organs.

Pulmonary echinococcosis

Pulmonary echinococcosis can be asymptomatic for many years if there are no complications due to slow development. With the development of cysts, patients may present compressive symptoms, such as cough, chest pain, hemoptysis, and dyspnea. If the ruptured cyst enters the bronchi, there may be paroxysmal cough, the patients can cough up a large amount of transparent mucus and internal capsules of the pathogen, and the scolices can be found in the sputum. Fever, purulent sputum, and hemoptysis may occur if there are infections. If the ruptured cyst enters the pleural cavity, hydropneumothorax may occur, subsequently progressing into empyema. Some patients may present with hypersensitive reactions such as skin rash, fever, nausea, vomiting, abdominal pain, bronchospasm, and shock, and there may be death in severe cases. In the percussion on the lesion area, there are dullness, and respiratory sounds are decreased or absent. Huge cysts can compress the mediastinum, displacing the trachea and heart.


Diagnosis

The diagnosis is mainly based on the imaging examinations, such as X-ray, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI).


Treatment

Surgical excision is the best treatment regimen, and after surgery patients should take orally albendazole 10 - 15mg/(kg.d) after meals in the morning and on the evening for 3 - 12 months in the treatment of hepatic cystic echinococcosis, for at least 2 years in the treatment of hepatic alveolar echinococcosis, and for 1 year in the treatment of pulmonary echinococcosis.

Patients contraindicated to surgery should take orally albendazole 10 - 15mg/(kg.d) after meals in the morning and on the evening for a lifetime.