Echinococcosis is a parasitic disease caused by tapeworms of the Echinococcus type. The two main types of the disease are cystic echinococcosis and alveolar echinococcosis. Less common forms include polycystic echinococcosis and unicystic echinococcosis. The disease often starts without symptoms and this may last for years. The symptoms and signs that occur depend on the cyst's location and size. Alveolar disease usually begins in the liver but can spread to other parts of the body, such as the lungs or brain. When the liver is affected, the patient may experience abdominal pain, weight loss, along with yellow-toned skin discoloration from developed jaundice. Lung disease may cause pain in the chest, shortness of breath, and coughing. The infection is spread when food or water that contains the eggs of the parasite is ingested or by close contact with an infected animal. The eggs are released in the stool of meat-eating animals that are infected by the parasite. Commonly infected animals include dogs, foxes, and wolves. For these animals to become infected they must eat the organs of an animal that contains the cysts such as sheep or rodents. The type of disease that occurs in human patients depends on the type of Echinococcus causing the infection. Diagnosis is usually by ultrasound though computer tomography (CT) or magnetic resonance imaging (MRI) may also be used. Blood tests looking for antibodies against the parasite may be helpful as may biopsy. Prevention of cystic disease is by treating dogs that may carry the disease and vaccination of sheep. Treatment is often difficult. The cystic disease may be drained through the skin, followed by medication. Sometimes this type of disease is just watched. The alveolar form often requires surgical intervention, followed by medications. The medication used is albendazole, which may be needed for years. The alveolar disease may result in death. The disease occurs in most areas of the world and currently affects about one million people. In some areas of South America, Africa, and Asia, up to 10% of certain populations are affected. In 2015, the cystic form caused about 1,200 deaths; down from 2,000 in 1990. The economic cost of the disease is estimated to be around US$3 billion a year. It is classified as a neglected tropical disease (NTD) and belongs to the group of diseases known as helminthiases (worm infections). It can affect other animals such as pigs, cows and horses. Terminology used in this field is crucial since echinococcosis requires the involvement of specialists from nearly all disciplines. In 2020, an international effort of scientists, from 16 countries, led to a detailed consensus on terms to be used or rejected for the genetics, epidemiology, biology, immunology, and clinical aspects of echinococcosis.
Signs and symptoms
In the human manifestation of the disease, E. granulosus, E. multilocularis, E. oligarthrus and E. vogeli is localized in the liver (in 75% of cases), the lungs (in 5–15% of cases), and other organs in the body such as the spleen, brain, heart, and kidneys (in 10–20% of cases). In people who are infected with E. granulosus and therefore have cystic echinococcosis, the disease develops as a slow-growing mass in the body. These slow-growing masses, often called cysts, are also found in people who are infected with alveolar and polycystic echinococcosis. The cysts found in those with cystic echinococcosis are usually filled with a clear fluid called hydatid fluid, are spherical, typically consist of one compartment, and are usually only found in one area of the body. While the cysts found in those with alveolar and polycystic echinococcosis are similar to those found in those with cystic echinococcosis, the alveolar and polycystic echinococcosis cysts usually have multiple compartments and have infiltrative as opposed to expansive growth. Depending on the location of the cyst in the body, the person could be asymptomatic even though the cysts have grown to be very large or be symptomatic even if the cysts are tiny. If the person is symptomatic, the symptoms will depend largely on where the cysts are located. For instance, if the person has cysts in the lungs and is symptomatic, they will have a cough, shortness of breath, and/or pain in the chest. On the other hand, if the person has cysts in the liver and is symptomatic, they will experience abdominal pain, abnormal abdominal tenderness, hepatomegaly with an abdominal mass, jaundice, fever, and/or anaphylactic reaction. In addition, if the cysts were to rupture while in the body, whether during surgical extraction of the cysts or by trauma to the body, the person would most likely go into anaphylactic shock and have high fever, pruritus (itching), edema (swelling) of the lips and eyelids, dyspnea, stridor, and rhinorrhea. Unlike intermediate hosts, definitive hosts are usually not hurt very much by the infection. Sometimes, a lack of certain vitamins and minerals can be caused in the host by the very high demand of the parasite. The incubation period for all species of Echinococcus can be months to years or even decades. It largely depends on the location of the cyst in the body and how fast the cyst is growing.
Cause Like many other parasite infections, the course of Echinococcus infection is complex. The worm has a life cycle that requires definitive hosts and intermediate hosts. Definitive hosts are normally carnivores such as dogs, while intermediate hosts are usually herbivores such as sheep and cattle. Humans function as accidental hosts, because they are usually a dead end for the parasitic infection cycle, unless eaten by dogs or wolves after death.
Hosts
… excerpt ends here. Continue reading the full article.
