Alveolar hydatid disease (AHD) is a form of

echinococcosis Echinococcosis is a parasitic disease of 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 ''u ...

, or a disease that originates from a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

flatworm The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegmen ...

. AHD is caused by an infection of the flatworm species '' Echinococcus multilocularis''. Although alveolar echinococcosis is rarely diagnosed in

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s and is not as widespread as cystic

(caused by ''

Echinococcus granulosus ''Echinococcus granulosus,'' also called the hydatid worm, hyper tape-worm or dog tapeworm, is a cyclophyllid cestode that dwells in the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and hu ...

''), it is also still a serious disease that has a significantly high fatality rate. It is considered one of the most life-threatening

helminthic Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as sch ...

infections humans can have. It is most prevalent in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

, Eastern

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedo ...

Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...

Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is borde ...

, and

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

, and is mostly confined to the Northern hemisphere, south to around the 40th or 45th degree of Northern latitude, save some cases reported in

Northern Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in t ...

Signs and symptoms

As the larvae grow in the liver, they create lesions. If untreated, this progresses into abdominal mass and/or pain,

jaundice Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...

, and finally liver failure.

Cause

AHD is caused by the larval stage of ''E. mulitilocularis'', a species of flatworm found in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

. Humans make poor intermediate hosts for the worm, as they play no role in their life cycle. However, when exposed the worms will still infect them. A major risk factor is when their domesticated dogs and

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

s eat wild, infected (typically arvicolid)

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

s. Their

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a rela ...

then will contain the worms' eggs, which have fully developed larval worms inside. Humans become infected after eating food or water contaminated by embryonated eggs, or by handling an infected host like dogs and cats or by

skinning Skinning is the act of skin removal. The process is done by humans to animals, mainly as a means to prepare the meat beneath for cooking and consumption, or to harvest the skin for making fur clothing or tanning it to make leather. The sk ...

infected foxes.

Pathophysiology

Once ingested by humans, "the

oncosphere An oncosphere is the larval form of a tapeworm once it has been ingested by an intermediate host animal. The intermediate host must ingest the tapeworm's eggs either in food or water-- once this has happened, the eggs hatch and develop into onc ...

s hatch in the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

, become activated, penetrate the epithelial layer, and migrate via

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

and

lymphatic vessel The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph ves ...

s to the visceral organs, primarily the liver, where they develop to another larval stage, the metacestode." The larval growth resembles a slow-moving liver tumor and it is able to destroy both the liver parenchyma and its function.

Diagnosis

Due to its infiltration into

biliary A bile duct is any of a number of long tube-like structures that carry bile, and is present in most vertebrates. Bile is required for the digestion of food and is secreted by the liver into passages that carry bile toward the hepatic duct. It ...

and

vascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

liver tissue, it can be difficult to differentiate AHD and

liver cancer Liver cancer (also known as hepatic cancer, primary hepatic cancer, or primary hepatic malignancy) is cancer that starts in the liver. Liver cancer can be primary (starts in liver) or secondary (meaning cancer which has spread from elsewhere to th ...

Management

Early detection and treatment and radical surgery is key to preventing fatality from AHD. Treatment may include liver resection to remove the larvae and

chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemother ...

using benzimidazoles. Chemotherapy must continue for many years, sometimes for the remainder of the patient's life. Failure to comply with these expensive and difficult treatments will likely result in death for the patient.

Prognosis

The disease is often progressive and destructive. The growth happens slow, and so many people do not get symptoms until the later stages. Central

necrotic Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

cavities are common in advanced stages of the disease.

Epidemiology

AHD is not as common as diseases caused by other flatworms, but it is still prevalent in the Northern hemisphere. It is not uncommon in China, with some communities having a 5% or more infection rate. In Europe, it is considered an emerging disease. The increasing fox populations of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

correlate with heightened reported cases.

History

In 1855,

Rudolf Virchow Rudolf Ludwig Carl Virchow (; or ; 13 October 18215 September 1902) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as "the father of modern pathology" and as the founder ...

, the German

pathologist Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in th ...

, recognized that the disorder that was at the time known as ''

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

carcinoma of the liver'', which was known for its tumor-like

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s in the liver, were actually caused by an ''Echinococcus'' species. For 100 year it was debated whether the species was ''E. granulosus'' or a different species. It was finally settled by two publications between 1954 and 1955, the former from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...

and the latter from

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...

Society and culture

AHD is confined to the Northern hemisphere. There are about 18,235 reported cases every year with 95% hailing from

Research directions

Wildlife research is working to detect the parasite in new areas.

References

External links

{{Medical resources , DiseasesDB = 4048 , ICD10 = {{ICD10, B, 67, 7, b, LinkMajor , ICD9 = {{ICD9, 122.7 , ICDO = , OMIM = , MedlinePlus = , eMedicineSubj = , eMedicine_mult = , eMedicineTopic = , MeshID = Diseases of liver Helminthiases