Liver fluke is a collective name of a polyphyletic group of parasitic trematodes under the phylum Platyhelminthes. [1] They are principally parasites of the liver of various mammals, including humans. Capable of moving along the blood circulation, they can occur also in bile ducts, gallbladder, and liver parenchyma. In these organs, they produce pathological lesions leading to parasitic diseases. They have complex life cycles requiring two or three different hosts, with free-living larval stages in water. [2]
The body of liver flukes is leaf-like and flattened. The body is covered with a tegument. They are hermaphrodites having complete sets of both male and female reproductive systems. They have simple digestive systems and primarily feed on blood. The anterior end has the oral sucker opening into the mouth. Inside, the mouth leads to a small pharynx which is followed by an extended intestine that runs the entire length of the body. The intestine is heavily branched and the anus is absent. Instead, the intestine runs along an excretory canal that opens at the posterior end. Adult flukes produce eggs that are passed out through the excretory pore. The eggs infect different species of snails (as intermediate hosts) in which they grow into larvae. The larvae are released into the environment from which the definitive hosts (humans and other mammals) acquire the infection. In some species another intermediate host is required, generally a cyprinid fish, and the definitive hosts are infected from eating infected fish. Hence, these species are food-borne parasites. [3] [4]
Liver fluke infections cause serious medical and veterinary diseases. Fasciolosis of sheep, goats and cattle, is the major cause of economic losses in dairy and meat industry. [5] Fasciolosis of humans produces clinical symptoms such as fever, nausea, swollen liver, extreme abdominal pain, jaundice and anemia. [6]
Clonorchiasis and opisthorchiasis (due to Opisthorchis viverrini ) are particularly dangerous. They can survive for several decades in humans causing chronic inflammation of the bile ducts, epithelial hyperplasia, periductal fibrosis and bile duct dilatation. In many infections these symptoms cause further complications such as stone formation, recurrent pyogenic cholangitis and cancer (cholangiocarcinoma). [7] Opisthorchiasis is the leading cause of cholangiocarcinoma in Thailand and Laos. [8] Clonorchis sinensis and Opisthorchis viverrini are both categorized by the International Agency for Research on Cancer (IARC) as Group 1 carcinogens. [9] [10]
Species of liver fluke include: [11] [12]
Trematoda is a class of flatworms known as flukes or trematodes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five traditional vertebrate classes: mammals, birds, amphibians, reptiles, and fish.
Clonorchis sinensis, the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on bile. It was discovered by British physician James McConnell at the Medical College Hospital in Calcutta (Kolkata) in 1874. The first description was given by Thomas Spencer Cobbold, who named it Distoma sinense. The fluke passes its lifecycle in three different hosts, namely freshwater snail as first intermediate hosts, freshwater fish as second intermediate host, and mammals as definitive hosts.
Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is used to treat schistosomiasis, clonorchiasis, opisthorchiasis, tapeworm infections, cysticercosis, echinococcosis, paragonimiasis, fasciolopsiasis, and fasciolosis. It should not be used for worm infections of the eye. It is taken by mouth.
Clonorchiasis is an infectious disease caused by the Chinese liver fluke and two related species. Clonorchiasis is a known risk factor for the development of cholangiocarcinoma, a neoplasm of the biliary system.
Fasciolosis is a parasitic worm infection caused by the common liver fluke Fasciola hepatica as well as by Fasciola gigantica. The disease is a plant-borne trematode zoonosis, and is classified as a neglected tropical disease (NTD). It affects humans, but its main host is ruminants such as cattle and sheep. The disease progresses through four distinct phases; an initial incubation phase of between a few days up to three months with little or no symptoms; an invasive or acute phase which may manifest with: fever, malaise, abdominal pain, gastrointestinal symptoms, urticaria, anemia, jaundice, and respiratory symptoms. The disease later progresses to a latent phase with less symptoms and ultimately into a chronic or obstructive phase months to years later. In the chronic state the disease causes inflammation of the bile ducts, gall bladder and may cause gall stones as well as fibrosis. While chronic inflammation is connected to increased cancer rates, it is unclear whether fasciolosis is associated with increased cancer risk.
Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans, and is transmitted by sheep and cattle to humans all over the world. The disease caused by the fluke is called fasciolosis or fascioliasis, which is a type of helminthiasis and has been classified as a neglected tropical disease. Fasciolosis is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite's metacercariae encysted on plants. F. hepatica, which is distributed worldwide, has been known as an important parasite of sheep and cattle for decades and causes significant economic losses in these livestock species, up to £23 million in the UK alone. Because of its relatively large size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species. F. hepatica's closest relative is Fasciola gigantica. These two flukes are sister species; they share many morphological features and can mate with each other.
Fasciola, commonly known as the liver fluke, is a genus of parasitic trematodes. There are three species within the genus Fasciola: Fasciola nyanzae,Fasciolahepatica and Fasciolagigantica. Fasciola hepatica and F. gigantica are known to form hybrids. Both F. hepatica and F. gigantica and their hybrids infect the liver tissue of a wide variety of mammals, including humans, in a condition known as fascioliasis. F. hepatica measures up to 30 mm by 15 mm, while F. gigantica measures up to 75 mm by 15 mm. Fasciola nyanzae is thought to exclusively infect the common hippopotamus, Hippopotamus amphibius.
Fasciola gigantica is a parasitic flatworm of the class Trematoda, which causes tropical fascioliasis. It is regarded as one of the most important single platyhelminth infections of ruminants in Asia and Africa. The infection is commonly called fasciolosis.
Tribendimidine is a broad-spectrum anthelmintic agent developed in China, at the National Institute of Parasitic Diseases in Shanghai. It is a derivative of amidantel.
Opisthorchis viverrini, common name Southeast Asian liver fluke, is a food-borne trematode parasite from the family Opisthorchiidae that infects the bile duct. People are infected after eating raw or undercooked fish. Infection with the parasite is called opisthorchiasis. O. viverrini infection also increases the risk of cholangiocarcinoma, a cancer of the bile ducts.
Dicrocoelium dendriticum, the lancet liver fluke, is a parasite fluke that tends to live in cattle or other grazing mammals.
Opisthorchis felineus, the Siberian liver fluke or cat liver fluke, is a trematode parasite that infects the liver in mammals. It was first discovered in 1884 in a cat's liver by Sebastiano Rivolta of Italy. In 1891, Russian parasitologist, Konstantin Nikolaevich Vinogradov (1847–1906) found it in a human, and named the parasite a "Siberian liver fluke". In the 1930s, helminthologist Hans Vogel of Hamburg published an article describing the life cycle of Opisthorchis felineus. Felineus infections may also involve the pancreatic ducts. Diagnosis of Opisthorchis infection is based on microscopic identification of parasite eggs in stool specimens. Safe and effective medication is available to treat Opisthorchis infections. Adequately freezing or cooking fish will kill the parasite.
Opisthorchiasis is a parasitic disease caused by certain species of genus Opisthorchis. Chronic infection may lead to cholangiocarcinoma, a cancer of the bile ducts.
Fasciolidae is a family of trematodes and includes several parasites involved in the veterinary and medical sciences, which cause the disease Fasciolosis. Fasciolidae is divided into five genera by Olson et al. 2003. The family's various species are localised in liver, gall bladder, and intestine. Their life-cycle includes an intermediate host, freshwater snails from the family Lymnaeidae.
Opisthorchis is a genus of flukes in the family Opisthorchiidae.
Opisthorchiidae is a family of digenean trematodes. Opisthorchiidae have cosmopolitan distribution.
Koi is a "salad" dish of the Lao people living in modern-day Laos and Isan, Thailand, consisting of raw meat denatured by acidity, usually from lime juice. Common varieties include koi kung, with shrimp as the main ingredient, and koi paa /koi pla, which consists of minced or finely chopped raw fish in spicy salad dressing.
Trematodiasis is a group of parasitic infections due different species of flukes, the trematodes. Symptoms can range from mild to severe depending on the species, number and location of trematodes in the infected organism. Symptoms depend on type of trematode present, and include chest and abdominal pain, high temperature, digestion issues, cough and shortness of breath, diarrhoea and change in appetite.
Carcinogenic parasites are parasitic organisms that depend on other organisms for their survival, and cause cancer in such hosts. Three species of flukes (trematodes) are medically-proven carcinogenic parasites, namely the urinary blood fluke, the Southeast Asian liver fluke and the Chinese liver fluke. S. haematobium is prevalent in Africa and the Middle East, and is the leading cause of bladder cancer. O. viverrini and C. sinensis are both found in eastern and southeastern Asia, and are responsible for cholangiocarcinoma. The International Agency for Research on Cancer declared them in 2009 as a Group 1 biological carcinogens in humans.
Gastropod-borne parasitic diseases (GPDs) are a group of infectious diseases that require a gastropod species to serve as an intermediate host for a parasitic organism that can infect humans upon ingesting the parasite or coming into contact with contaminated water sources. These diseases can cause a range of symptoms, from mild discomfort to severe, life-threatening conditions, with them being prevalent in many parts of the world, particularly in developing regions. Preventive measures such as proper sanitation and hygiene practices, avoiding contact with infected gastropods and cooking or boiling food properly can help to reduce the risk of these diseases.